ZOOLOGY
A TEXTBOOK FOR COLLEGES
AND UNIVERSITIES
NEW-WORLD SCIENCE SERIES
Edited by John W. Ritchie
SCIENCE FOR BEGINNERS
By Delos Fall
TREES, STARS, AND BIRDS
By Edwin Lincoln Moseley
SCIENCE OF THE EVERYDAY WORLD
By Carleton W. Washburne
HUMAN PHYSIOLOGY
By John W. Ritchie
SANITATION AND PHYSIOLOGY
By John W. Ritchie
LABORATORY MANUAL FOR USE WITH
"HUMAN PHYSIOLOGY"
By Carl Hartman
EXERCISE AND REVIEW BOOK IN BIOLOGY
By/. G. Blaisdell
PERSONAL HYGIENE AND HOME NURSING
By Louisa C, Lippitt
SCIENCE OF PLANT LIFE
By Edgar Nelson Transeau
ZOOLOGY
By T. D. A. Cockerett
EXPERIMENTAL ORGANIC CHEMISTRY
By Augustus P. West
NEW-WORLD SCIENCE SERIES
Edited by John W. Ritchie
ZOOLOGY
A TEXTBOOK
FOR COLLEGES AND
UNIVERSITIES
BY
T. D. A. COCKERELL
\\
Professor of Zoology
University of Colorado
ILLUSTRATED
Yonkers-on-Hudson, New York
WORLD BOOK COMPANY
1920
WORLD BOOK COMPANY
THE HOUSE OF APPLIED KNOWLEDGE
Established, 1905, by Caspar W. Hodgson
YONKERS-ON-HUDSON, NEW YORK
2126 PRAIRIE AVENUE, CHICAGO
World Book Company offers Zoology for col-
lege and university use. Modern zoology,
the science of animal life, is inseparably
linked with the general problems of biology,
sociology, and even ethics. Regarded thus
broadly, it is a science which cannot be
omitted from any adequate system of educa-
tion, and the purpose of the present text is
to supply a treatment of the subject suffi-
ciently modern and comprehensive to meet
the needs of this age of social and political
reconstruction. It may form the basis of a
course to be given preferably in the sopho-
more year, and is designed for the use of
those who have had little or no previous
training in the subject. It is the first vol-
ume of a series of college science texts that
will be issued by this house
Copyright, 1920, by World Book Company
Copyright in Great Britain
All rights reserved
TO THE MEMORY OF THOSE WHO DIED
THAT WE MIGHT HAVE A CHANCE
TO MAKE A BETTER WORLD
417198
Bitae jFilum
To live, to grow, to work, to love,
Shall earth below or heaven above
Ask more of thee ?
Thus holding fast the golden thread
Which joins the living and the dead
Through all eternity !
CONTENTS
CHAPTER PAGE
i. THE PHYSICAL UNIVERSE . . . . . . . t
v/ 2. THE LIVING SUBSTANCE . . . . . . . . 5
3. THE CELL AND ITS ACTIVITIES . . . . 13
4. THE TISSUES . 22
5. RESPIRATION 31
6. THE INDIVIDUAL .......... 37
7. MENDELISM . . 41
8. THE RED SUNFLOWER . . . . . . . .51
9. THE CHROMOSOMES .... . . . . .62
10. FERTILIZATION 73
11. SEX . . . . 77
12. NATURE AND NURTURE ........ 89
13. SOCIAL LIFE 94
14. CHARLES DARWIN 101
15. VARIATION . . . . . . . . . . . 115
16. ALCOHOL AND HEREDITY 120
17. NATURAL SELECTION , . . . . . . . .129
18. ARGUMENTS FOR EVOLUTION 137
19. THE HISTORY OF LIFE 144
20. THE FLORISSANT SHALES OF COLORADO ..... 157
21. CAROLUS LINNJEUS ......... 164
22. THE PRINCIPLES OF CLASSIFICATION 175
23. THE PHYLA OF ANIMALS 178
24. PROTOZOA 186
25. PROTOZOA AND HEREDITY . 194
26. PROTOZOA AND DISEASE . . 199
27. SPONGES . . . 207
28. COZLENTERATA 2IO
29. ECHINODERMATA 2l8
30. BRYOZOA ........... 226
31. PLATYHELMINTHES . . . . . . . . . 229
32. NEMERTINEA, NEMATHELMINTHES, AND ROTATORIA . . .233
33. ANNELID WORMS .......... 237
34. MOLLUSCA ........... 243
35. ARTHROPODA (GENERAL) 253
vii
viii CONTENTS
CHAPTER PAGE
36. ARTHROPODA (CLASSIFICATION) . . . . . . .257
37. HENRI FABRE 280
38. LEPIDOPTERA ..... , * . . . 286
39. BEES . .293
40. ANTS ... . . . * 299
41. SCALE INSECTS 308
42. GRASSHOPPERS AND THEIR RELATIVES 313
43. PROCHORDATA AND CYCLOSTOMES 320
44. THE STRUCTURE OF THE VERTEBRATES 328
45. FISHES 342
46. AMPHIBIANS 358
47. REPTILES 364
48. BIRDS 373
49. MAMMALS 396
50. THE EVOLUTION OF THE HORSE AND ELEPHANT . . -417
51. THE EVOLUTION OF MAN 429
52. THE CHARACTERS OF HOMO 435
53. THE GEOGRAPHICAL DISTRIBUTION OF LIFE .... 442
54. THE BIOLOGICAL REGIONS OF THE WORLD .... 447
55. LIFE ZONES 454
56. LIFE IN THE TROPICS . . 463
57. LIFE IN THE ARCTIC AND ANTARCTIC REGIONS .... 467
58. LIFE IN THE SEA . . 472
59. Louis PASTEUR 479
60. DISEASE IN RELATION TO HUMAN EVOLUTION .... 489
61. HISTORY FROM A BIOLOGICAL POINT OF VIEW .... 492
62. EUGENICS 500
63. Louis AGASSIZ 508
64. SPENCER FULLERTON BAIRD AND THE UNITED STATES NATIONAL
MUSEUM . . . . . . . ...;.••. 520
65. SOCIOLOGY FROM A BIOLOGIST'S POINT OF VIEW . . . 530
66. SOME GENERAL RESULTS . . . . .. . -535
THE LAST LECTURE . . . . . • .., •ri.^«; •;•..•».;• • • 538
INDEX -.-• •• . . . . 541
INTRODUCTION
THE problems which mankind is compelled to face
are at once old and new, — much older than man
himself in so far as they are the problems of life, and
growth, and reproduction ; yet ever new, since man-
kind progresses, and creates for itself conditions
which have never existed before. There are two
reasons why we cannot safely go back to even the
wisest of the ancients, to get from them adequate
counsel for the direction of our modern life. One is,
that we are no longer situated as they were : after
two or three thousand years of development, our
modern society necessarily presents many complex
features of which they knew nothing, and could not
have foreseen. The other is, that we represent the
maturer age of our species, with accumulated knowl-
edge and records of experience behind us — knowl-
edge and experience dearly won, and constituting a
precious guide to conduct. The mature man looks
back with pleasure and longing to the days of his boy-
hood, but he does not appeal to his boyish thoughts
for the guidance of his later life. Yet the ancient
and modern meet as the result of the most recent
researches. Paradoxically, the discovery of innumer-
able details, the revelation of undreamed7of complex-
ities, leads us back to a better conception of the
essential simplicity of nature. Natural law, the un-
derlying unity in the midst of diversity, stands more
clearly revealed today than ever before, and we are
nearer than we ever were to a true philosophy. Thus
we appeal to the totality of existence, past and present,
and every fact has its place in our system, and teaches
some lesson. The mind, however, is limited in its
powers, and for practical purposes it is necessary to
ix
X INTRODUCTION
digest and condense the results of research, and
thereby provide a short cut to the fruits of the labor of
generations. At the same time the educational process
is not complete unless the student has patiently trodden
some path of discovery of his own, and has thus come
to appreciate the methods of science. In a democratic
society, no citizen can afford to remain ignorant. The
democracy of this country still remains largely an
ideal, only to be realized when the average level of
intelligence has been raised through education. We
are like young persons expecting to inherit a great
estate, to the management of which we must bring
the best powers we are capable of developing. The
essential facts of biology, the science of life, should
surely be known to all, and we believe that some
course embo'dying them should be obligatory for
every student. If this is granted, some revision of
current methods appears to be required. The biology
or zoology for the average individual who has no
thought of specializing in the department should not
be too morphological, too rich in detailed facts of
structure and classification. Experience shows that
such minutiae are not remembered, and do not neces-
sarily leave as a residue any broad and useful con-
ceptions. The working out of a single problem or
small group of problems in detail is a different matter,
as it teaches of methods and points of view in a manner
never to be forgotten, and may well open the way for
an amateur interest which will remain a blessing
through life.
On the other hand, we cannot shirk the essential
problems because they are hard. Each generation
of men has to wrestle with the angel, and deal in some
manner with matters which it can never more than
INTRODUCTION xi
partly understand. From a psychological and peda-
gogical standpoint, it is surely an error to suppose
that each idea must be luminously clear at the moment
of presentation. Our deepest beliefs, our most pro-
found convictions, have been attained gradually, and
we thank our elders for early revealing to us the
existence of puzzles which required half a lifetime for
us to solve. A student may conceivably fail outright
in a course and yet have laid the foundation of a
brilliant discovery. There was doubtless humbug
in the ancient mysteries, as there is in many modern
ones ; yet mystery is not all humbug, and important
mental syntheses may require years for their de-
velopment. With the modern loosening of the hold on
religion, the feeling of awe may atrophy in a world too
superficially regarded and too cheaply explained.
The thread of our narrative is broken at intervals
by biographical chapters. We are too apt to receive
the gifts of science without asking whence they came.
It is well, therefore, to learn something of the lives of
those who have made discoveries or organized scien-
tific work. What we have today was not gained
without arduous toil and persistent zeal, often in the
face of many difficulties. As the pious studied the
lives of the saints, so may we pause now and then to
learn how scientific heroes have won new territory
for the kingdom of science. Thus, if we have any-
thing of generous response within us, we may return
to our studies refreshed, resolving that we also, in
some measure, will further the good cause.
T. D. A. C.
ACKNOWLEDGMENTS
THE author is greatly indebted to Professor G. H. Parker
and Professor H. S. Jennings, who read the manuscript and
offered many valuable suggestions. He is also indebted
to the kind criticisms of Dr. Donald W. Davis, Dr. E. B.
Copeland, Dr. Ross C. Whitman, and others. For the use
of some excellent photographs he has to thank Mr. E. R.
Warren. Mr. W. P. Hay rendered invaluable service in
selecting and advising in regard to illustrations, in addition
to the drawings with which he is credited in the text. Many
photographs have been secured through the courtesy of the
New York Zoological Society and the American Museum
of Natural History, New York City.
ZOOLOGY r
CHAPTER ONE
THE PHYSICAL UNIVERSE
I. IN the vast expanse of the known universe, the The laws of
materials composing the stars are essentially the same nature
as those found upon the earth, and the forces govern-
ing their movements do not differ from those which
may be noted and tested in any laboratory. Thus
physical nature possesses a unity which is more strik-
ing the more we inquire into it, and what we call the
"laws of nature," our statements of how things happen,
are considered to be valid everywhere. This uni-
formity of action extends not only through space but
also in time, so that after sufficient experience of
natural phenomena, man is able to predict events far
in the future, and assert the occurrence of others in
the remote past, in spite of the absence of any con-
temporary records. To the unscientific it seems
miraculous that an astronomer could say to his little
son, wondering at the sight of Halley's Comet in the
sky: "If you live to be a very old man, you will see
that comet again, but I shall never see it" ; and that
the boy should have lived, and come to old age, and
seen the comet appear in the very year predicted.
Such a prophecy is one of the commonplaces of modern
astronomy, but it could not be made were not the
r"laws of nature" valid throughout the ages.
2. It must not be supposed, however, that scientific Limitations
men have discovered all the important facts. The man
philosopher understands by the term "reality" the
totality of what exists, — all the phenomena of the
2 •:'•.•*
ZOOLOGY
The nature
of truth
can never be examined by
our human senses. The limitations 'of our percep-
tions are well shown when we realize that the vibra-
tions or waves which give us the sensations of light,
sound, or electric shock are only a few of those which
must exist. The ultra-violet light, which we cannot
see, we can determine by its chemical effects, and no
physicist doubts that there are innumerable vibrations
which we cannot detect at all.
3. Yet the known and unknown facts are so related
that the known part of nature is in a sense a fair
sample of the whole. The unknown does not con-
tinually disturb the known in unexpected ways, and
when it does so, it is usually brought into the region
of the known. Its nature is calculated from the
character of the disturbance. The scientific man has
to deal with "truth," and by truth he means not the
absolute reality of the philosopher, but such reality
as he has been able to test and examine. He does
not absolutely know that the "laws" deduced from
the experience of mankind will always be found valid,
but the mass of accumulated experience is such that
he finds he can rely upon them. This is especially
true in the realm of physics.
The unique-
ness of life
LIFE
4. Modern science tends to emphasize the unique-
ness of life, in spite of the fact that vital phenomena
are said to be "explained" by laws of chemistry and
physics. The ancients imagined life, in some form
or other, to be as widely diffused as heat or light,
and saw in the starry heavens a region peopled by
innumerable sentient human beings. Today, while
THE PHYSICAL UNIFERSE 3
we do not know what forms of spiritual existence may
.be possible, we can positively state that life, in the
ordinary acceptance of the word, is possible in only an
infinitesimal portion, relatively speaking, of the uni-
verse. It is practically certain that the earth is the
only planet of the solar system which can support
life, as we know it. Even if we assume (it is pure
assumption) that there are other systems wherein
life exists, the whole life-bearing surface must be so
small a part of space that it cannot be expressed in
intelligible mathematical terms. There are also good
reasons for limiting the duration of life, so that its
existence on any globe belongs to only a minute frag-
ment of the time which the astronomer recognizes as
representing the minimum required for the evolution
of the universe. Life, then, is the most unique and
exceptional phenomenon, or group of phenomena, in
the material universe ;. and had it been possible for
a scientific being to study nature prior to or outside
of the existence of life areas, he could hardly have
predicted or expected living beings, much less those
conscious of their own existence.
5. Asking how life originated, and what it is, we Matter and
must first determine the conditions under which it is €
manifested. The physical universe is said to consist
of matter, but this "matter" is known to us only
through its manifestations of energy, all of which
consist of movements during time, through space.
These movements may be gross and visible, or exces-
sively minute, such as those producing heat, or bringing
about chemical changes. Although an object such as
this book may be said to be stationary, as it rests upon
the table, its minute particles are actually in motion.
The totality of matter is said to be constant, and also,
4 ZOOLOGY
necessarily, the totality of energy; but this energy
may cease to produce any appreciable phenomena
without being destroyed. Physicists suppose that
conceivably the whole universe might (or, some say,
will) "run down," so that all its energy will be in
forms producing no chemical or physical "phenomena,"
and thus practically non-existent from a human
standpoint. No one knows how such an inert universe
could be started up again, but the translation of energy
from latent to active forms is familiar, and without it
there could be no life. Life exists because oscillation
or alternation between the two states of energy is
possible.
CHAPTER TWO
THE LIVING SUBSTANCE
1. LIFE, as we know it, is manifested only by pro- Protoplasm
toplasm. This protoplasm, or primal material of life, J^teriS8
is a translucent, jelly-like substance, seeming on in-
spection to have no definite structure. The amount
occurring in a single mass is, however, quite limited;
the protoplasm of the living body is broken up into
innumerable separate though contiguous units, called
the cells.
While we speak of the living material as protoplasm,
the word must be understood to indicate not a single
sort of substance, .but a whole class of substances
differing in minute though very significant details.
The protoplasm of man is not the protoplasm of the
worm or flower; yet it is convenient to have a single
word to designate all living material, which, however
diverse in details, is fundamentally similar in all cases.
This essential similarity has been strongly emphasized
by recent experimental work, which shows that it is
possible, up to a certain point, to reason from the
life phenomena of plants to those of animals, or vice
versa.
2. What, then, is this protoplasm ? It is a mixture chemistry
of complex chemical compounds, consisting of car- p^m*0"
bon, oxygen, hydrogen, nitrogen, and other elements.
Such a statement conveys little to the mind, especially
if we recall these elements in their pure form — car-
bon as charcoal or diamond, the other three as invisible
gases. A chemical analysis may give us all these
elementary bodies, in certain proportions, but we are
scarcely more edified than we should be if shown the
paints out of which a splendid picture had been made.
5
6 ZOOLOGY
Chemistry, however, has much to teach us about
protoplasm. In chemistry the ultimate particles of
the elementary substances are known as atoms (we
are not now concerned with the still smaller electrons),
and these atoms may be combined in definite systems
to form molecules, which are the least possible particles
of compounds. Thus water consists of hydrogen and
oxygen in chemical combination, the molecules having
two atoms of hydrogen to one of oxygen. The water
atom is comparatively simple, and is very stable ; that
is, it does not readily fall apart, and thus lose its pe-
culiar properties. It will be noted that the properties
of a compound cannot be readily deduced from the
properties of the elements of which it is composed ;
thus water has no particular resemblance to oxygen or
hydrogen. We are therefore not surprised that the
complex compound protoplasm is not like carbon or
any of the elementary gases derivable from it on
ultimate analysis.
Protoplasm 3. The protoplasm molecules, composing the smallest
system1"6 possible particles of this substance, are known to be
of extreme complexity, so that in comparison with the
water molecule they are, as it were, richly furnished
palaces as compared with a hut. So complex are they,
that it has been impossible as yet to construct a formula
representing the composition of any one of them, as
may be done for most of the molecules known to
chemists. With this complexity goes instability, so
that protoplasm is constantly in a state of change, the
molecules gaining and losing substance. They are
therefore dynamic systems of atoms, not static like the
water molecule. This power of changing, of being the
seat of processes, and therefore the cause of phenomena,
is fundamental to life ; but it alone would not suffice.
THE LIVING SUBSTANCE f
The dead body is the seat of rapid change ; it falls
apart, loses its identity. This is precisely what the
living substance does not; it has the marvelous power
of retaining its identity as a system, though all its
actual atoms may be lost and replaced by others. We
are reminded of a river, which looks the same from day
to day, though the water passes by. This ability to
retain its character in the midst of change applies not
merely to protoplasm in the broad sense, but also to
all the myriads of particular kinds, of which, as we shall
see, many coexist in the same individual. Thus this
ever changing substance (in one sense) is so stable
(in another sense) that it may continue almost un-
modified for millions of years, while mountain ranges
are raised up or worn away. This we know by com-
paring the fossil remains of animals and plants with
their modern representatives. The ancient protoplasm
itself has not been preserved, but the exact forms of
creatures of bygone ages are often clearly represented
in the rock, and we can rest assured in many cases
that their living substance was similar to that of
existing types.
4. Students of chemistry recognize inorganic and Carbon
organic chemistry. So-called organic chemistry is the comP°und8
chemistry of those carbon compounds which were
formerly supposed to stand in a class by themselves,
being produced by living beings, or derived from the
products of such. As carbon is only one of the numer-
ous elements, the study of its more intricate com-
pounds might seem to be a very small branch of the
science ; but as a matter of fact it is a very large part
of chemistry, and the most complex and difficult part.
The carbon atom has quite unique properties, and its
power of combining with other atoms is such that it
8
ZOOLOGY
Proteins
Complexity
of proteins
readily forms the basis of extremely complex and diverse
molecules. It is therefore peculiarly fitted to enter
into the living substance, and so far as we know,
without it no life would be possible.
5. When we are regarding the materials of the living
body from a chemical standpoint, we speak of proteins,
and recognize that within the protoplasm of a single
cell there are various kinds of proteins. Thus it is
not only true that the protoplasm of different animals
and plants differs, but that of any one individual, or
of any one of its cells, is far from uniform. Different
species may indeed have in their make-up many of
the same kinds of living materials, the specific difference
being due more to the particular combination than
anything else. Thus the words composing this sen-
tence are all different though they contain various
letters in common.
6. The proteins are broken down by the chemist,
so that they lose their original characters, and of
course their relation to life activities. The process is
similar to that which occurs in the digestion of foods in
the body. They do not go to pieces all at once, but
are reduced by a regular series of steps to what are
known as amino-acids. These amino-acids are of very
many kinds. Emil Fischer has endeavored to climb
up the stairway, as it were, toward the complexity of
the living stuff. It has long been known that many
organic compounds could be produced synthetically —
that is, put together — in the chemical laboratory.
Fischer was able to go so far as to produce polypep-
tids, which are combinations of amino-acids. The-
oretically, it might seem merely a matter of time and
patience to get the very substance of protoplasm con-
structed, but probably the difficulties are insuperable.
THE LIVING SUBSTANCE 9
In consequence of the complexity of the living cell,
it would be necessary to construct not one substance,
but a whole series of them, and then put them together
in such a way as to construct a living machine.
7. Suppose we could construct a cell, in all respects Cessation
like that of a living organism : would it be endowed
with life ? Could our scientific Pygmalion expect to without
see his Galatea live ? No certain answer can be given
to this question, but there are reasons for suggesting
the affirmative. Experiments have been made, in
which seeds and spores have been kept for considerable
periods at the extremely low temperatures known to
modern physicists, temperatures at which the very
air is liquefied. It is to be supposed that at these
temperatures all life activities, however subtle, must .
stop ; the machine is absolutely at a standstill. In
spite of this, on the return to normal conditions,
vitality is unimpaired. This being the case, we may
probably argue with reason that the extremely low
temperature which inhibits all change would, if main-
tained, preserve the material indefinitely, leaving it
ready at any time to take up life activities when
suitably warmed and moistened. Such permanent
cold storage would be found in the vast abysses of
space, where conceivably minute spores might cir-
culate for ages, until they chanced to fall upon a suit-
able planet. In some such way the earth may have
received its life ; but if so, we are still no nearer to
solving the problem of the origin of life itself.
8. The physics of the cell is no less interesting than Colloidal
the chemistry. Protoplasm is said to be a colloid
(from the word kolla, meaning "glue" in Greek), a
name given to substances which diffuse slowly in
liquids and do not form true solutions as do crystalloids,
10 ZOOLOGY
such as sugar or salt, with which they are contrasted.
The terms refer to states or conditions rather than to
substances, but a number of important facts are con-
nected with the colloidal nature of the living material.
Guyer defines protoplasm as an aggregate of colloids
holding water for the most part, and in this water crys-
talloids are held in solution. Now such colloids may
be more or less solid or liquid, and when they reach the
more solid condition they are spoken of as gels. Pro-
toplasm, in the living state, undergoes such changes,
and these are reversible, so that the two states may
alternate indefinitely. It is supposed that many of
the visible phenomena of the cell are due to conditions
of gelation. Heat or poisons may act so severely on
the protoplasm that an irreversible gelation results,
when death at once ensues. We are reminded of elastic
substances which lose their elasticity on being subjected
to too severe a strain.
9. One of the most striking properties of protoplasm
is its irritability; that is, its power of responding by
movement of some kind to a stimulus, which may
arise externally or internally. This disturbance or
stimulus may be physical or chemical, but the essential
point is that the living material does not merely trans-
mit the wave of energy, as an iron bar may transmit
heat, but displays characteristic movements of its own.
Irritability, in a biological sense, includes all such re-
sponses. Thus, if you meet a friend, who smiles in
response to your greetings, he is exhibiting irritability
in the sense now employed. In the lower forms of life
this irritability is more or less general, and the paths
of disturbance are indefinite; but in higher animals
there is a definite nervous system, and through it
messages are very rapidly transmitted to and from the
THE LINING SUBSTANCE II
brain. It has been suggested that the transmission of
a nerve impulse may be connected with a wave of gelation
sweeping along the nerve, an almost instantly reversible
change in the density of the material. If this is true,
there is some analogy with the transmission of sound
in air, the sound "waves" representing temporary
conditions of density. Darwin, when experimenting
with that remarkable insectivorous plant, the sundew
(Drosera), found that if one side of the leaf received a
stimulus (e.g., caught a fly), the sensitive hairs on the
other side moved after a time. During the interval,
he noted that a wave of cloudiness passed across the
leaf, apparently a condition of temporary or reversible
gelation. This activity was prevented by such an-
aesthetics as ether or chloroform, and if their action
on the nerve tissue of animals is analogous, we can
understand how their effects are produced.
10. The colloidal particles of the living substance, Energy of
each consisting of many molecules, bear electric charges. $Ub8uInce
They are immersed in or surrounded by water, con-
taining dissolved materials which themselves bear
positive or negative charges of electricity. The whole
forms a system in which attraction and repulsion, and
therefore gelation or liquefaction, depend upon electric
states. When particles of a* colloid are brought to-
gether, or when they are driven apart, as the result of
electric forces, new states are produced, leading to
fresh changes. Thus, without going into further de-
tails, we gain some idea of the physical phenomena
implied when we say that living protoplasm is a dy-
namic system of atoms and molecules. We also see
how the life processes are dependent upon the presence
of water and of non-living matters in solution ; in other
words, the protoplasm molecules, though the exclusive
12 ZOOLOGY
seat of life, cannot carry on their functions except in
a special environment. From the standpoint of pure
physics, it becomes impossible to separate rigidly the
processes or displays of energy of the living material
from those going on in the immediately adjacent
medium ; indeed, the whole combination really dis-
plays the activities which we call vital.
The fact that water, in a liquid state, is necessary
for the manifestation of vital activities, greatly re-
stricts the possibilities of life in the universe. If we
make a table of the known temperatures, from the cold
of space to that of the hottest stars, the portion of it
on which we mark water as liquid seems almost in-
finitesimal ; yet it is within these narrow limits that
the manifestations of life must occur. It is true, as
we have seen, that temperatures below the limit do
not necessarily injure the vital machine ; but those
above the boiling point cause irreparable damage.
Gelation occurs which is irreversible, and the rhythm
of life has departed.
The vital II. Life, then, is rhythmic; summer and winter,
day and night, the rise and fall of each successive gen-
eration, the beating of the heart, the reversible states
of the living colloid, the dance of the atoms and elec-
trons, everywhere in nature we see the swinging pendu-
lum which marks the passage of time. No wonder that
music appeals to us irresistibly, and that in decorative
art beauty is gained by the repetition of a theme.
As Bergson insists, our deepest convictions arise out
of the very nature of life itself.
CHAPTER THREE
THE CELL AND ITS ACTIVITIES
I. LIVING creatures are either single cells, or are made The cell
up of aggregations of cells. The word "cell" is rather
misleading; it was given many years ago to those
plant cells which take the form of a little compartment
or box, containing a fluid. Such cells are rigid, some-
times large enough to be seen with a hand lens without
difficulty. We now know that the hard wall, the box,
is composed of cellulose, which is not part of the living
material, and that the essential thing is the protoplasm
which it incloses. Not only are all plants cells or
groups of cells, but the same is true of animals. In
animals, however, there is no stiff wall of cellulose,
though there is commonly a thin membrane, and the
distinctness of the cells is much less evident on in-
spection. Since we recognize the fundamental simi-
larity of plant and animal cells, we use the same word
for both, and think of the living unit rather than
anything inclosing it. Our definition is thus entirely
changed, and comes to be : a cell is a particle or unit of
protoplasmic material, which exhibits all the essential
phenomena of life. It consists, of course, of innumer-
able molecules which, taken by themselves, would
not function as living things. Such a cell may exist
apart from others, as in the Protozoa or one-celled
animals. There is a relation between the nature of
the cell wall and the activities of the organism ; the
essentially stationary plant has stiff cell-walls, but in
the mobile animal most of the cells are necessarily
flexible. The function of a muscle cell, for example,
is connected with its ability to change its shape.
13
ZOOLOGY
Cell life and
individual
life
2. In protoplasm the molecule is composed of in-
numerable atoms, the colloid particle of many mole-
cules ; tfie cell, of multitudes of these colloid particles.
System within system, they all function as a unit ;
and the individual animal or plant, made up of mil-
lions of cells, also behaves as a single machine. Never-
theless, the cell is a definite unit of life, and its indi-
viduality is not lost in that of the creature of which it
forms a part. During the life of the individual, cells
are born and die ; every time we wash our hands, dead
skin cells, so small and flat as to escape observation,
fall away. In the blood are active cells known as
leucocytes (Greek for "white cells") or white blood cor-
puscles, which crawl about with a flowing motion,
looking like certain free single-celled animals (Protozoa)
which are found in the water of ditches (Fig. i). These
leucocytes may be taken from the body, and if kept in
a nourishing solution at the right temperature, continue
to live as independent beings. Still more remarkable
is the fact, recently discovered, that portions of a liv-
m£ body, composed of
highly specialized cells,
may be cut off and
isolated, and under
suitable conditions will
go on growing for an
indefinite period. No
one can deny life to
such isolated particles ;
yet the admission com-
pels us to recognize
FIG. i. Amiba, one of the Protozoa ; an ex- that the "life" of a
ample of a free-living cell, occurring in ponds - j
and ditches, n, nucleus; «,, ec, inner and man 1S Composite, and
outer protoplasm ; p, pseudopodia. is in a true Sense the
THE CELL AND ITS ACTIVITIES 1 5
summation of the lives of innumerable cells — some-
what as the life of a town or a school is the aggregate
of the lives of its members. The life of the body differs
from the life of the town or nation in that it is much
more completely socialized ; the parts or individual
cells work in more complete harmony, and are under
more accurate control by the governing power which
has its principal seat in the brain. In spite of this,
disturbances often occur, and the disease called cancer,
in which a group of cells runs riot, growing without
proper relation to the rest of the organism and without
developing even the necessary means for its own main-
tenance, represents anarchy in the corporate system.
Cancer tissue is not capable of entering into coopera-
tion with the rest of the body. When we say that hu-
man life is composite in the manner described, we do
not infer that human personality is without its proper
and definite unity, though the study of psychology
exhibits to us wonderful complexities of personality,
connected with bodily states and with the diverse ac-
tivities of the nervous system. With this, however,
we are not just now concerned.
• 3. Since cells are true units of life, they exhibit all Evolution of
the essential vital functions. That is to say, they react Hfe
to stimuli, they build up and break down, and finally
they reproduce. The origin of new cells is always
from the division of preexisting ones, so far as we have
any knowledge ; reproduction is division. No man
can make a cell, nor can he say how one came into
existence. Professor T. C. Chamberlin makes the
ingenious suggestion that prior to the appearance of
bacteria (decay-producing germs) it may have been
possible for a 'series of carbon compounds to evolve,
leading up to those complex enough to be the seat of
i6
ZOOLOGY
Continuity
of life
Reproduc-
tion
life ; whereas in our modern world this is impossible,
owing to the destructive attacks of minute organisms.
The suggestion is that life, having once evolved, will
tolerate no repetition of the process. However this
may be, it is everywhere recognized as a matter of
experience that every new cell, and therefore every new
life, arises from other life already existing. The theory
of evolution is merely an extension of this conception,
postulating that all life has thus arisen, and might be
traced back, had we all the data, to some common an-
cestor in a very remote past. The sameness and unity
of life phenomena lend support to this doctrine.
4. If it is true that all life arises from other life, it
necessarily follows that the stream of life is continuous,
there is no break between generations. At no point,
from the beginning many millions of years ago, — if
we may postulate such a beginning, — to the present
moment, has the sacred flame of life which burns in
us ever gone out. In a sense we are many millions of
years old, and have witnessed the story of evolution
from the beginning. Yet we must die. What is
death, that great contradiction of life's fundamentals ?
Are we to add death to the phenomena of the cell, to
complete its list of vital functions by this final negation
of all of them ?
5. The answer to this question is not to be left to
speculative philosophers or to theologians. It is de-
termined by observation. The continuity of life from
generation to generation is an observed fact, and it is
only possible because certain cells, at least, do not die.
The problem takes on a new aspect, however, when we
note that the animals which consist of one cell, the
Protozoa, reproduce by dividing, and both parts live.
There is no dead body. Woodruff, after raising
THE CELL AND ITS ACTIVITIES If
thousands of generations of the slipper animalcule,
Paramecium, concludes that, as Weismann long ago
assumed, these creatures are potentially immortal,
and do not even require the supposed stimulating
effect of conjugation — the union of the protoplasm
of two individuals. The fact that under natural con-
ditions myriads die from accidental causes or disease
has no bearing upon the question. We are obliged, in
the face of this evidence, to strike off death from the
list of phenomena necessarily accompanying life, and
therefore exhibited by every cell.
6. Yet we must die, and the innumerable cells com- why we die
posing our bodies must die, excepting only those which
go to form a new generation. Early in the develop-
ment of the individual, certain portions of the proto-
plasm are set aside to form the germ cells, whose
function it is to start a new generation. On this fact
Weismann developed his theory of the continuity of
the germ protoplasm, or germ plasm, the living material
which is passed on from parent to offspring. This
germ plasm does not make any muscles, or nerves, or
other body structures while it is waiting for the time
when it will take part in the formation of a new in-
dividual. The other cells, on the contrary, divide
many times, and the final result is muscle cells, and
nerve cells, and connective tissue cells, and so forth.
This specialization of the cells is necessary, in order
that they may do the work required in a highly or-
ganized body; but as a result they are rendered quite
unfit for reproduction. They have sacrificed the
potentiality of new life for the sake of becoming special-
ists. The body as a whole has bought all those powers
and qualities which make it man rather than protozoan,
at the price of having to die. The race, however, does
1 8 ZOOLOGY
not die ; it continues by those germ cells which, re-
maining inactive and biding their time, at length
come forth to defeat the forces of death.
Samuel Butler, in his fantastic story "Erewhon"
(anagram of "Nowhere"), states that the Erewhonians
believed that the soul of man was not immortal, but
that the universe was peopled by potentially immortal
beings, who need never die unless they were born into
the world. These beings, it was held, were aware that
death would eventually follow birth, but such was
their desire and curiosity to know what it was to be
alive, to be actual living people, that they could not
resist. They were willing to accept death as the price
of that precious experience. This fantasy now turns
out to embody a truth, and it is an actual fact that
death is the price of the higher life.
Metabolism j. Cells also build up and break down ; the living
cell maintains its identity, yet is constantly in a state
of change. Biologists have invented certain terms to
use in referring to these activities. The changes going
on in the cells, and consequently in the body, are
spoken of in general terms as metabolism, with the
adjectival form metabolic. Thus we say, the body
exhibits metabolism, or the metabolism was intense,
or the metabolic processes led to such and such results.
This word "metabolism" covers a great many things,
and for more exact (though still vague) definition we
speak of anabolism, the processes tending to build up
the body, and katabolism, the processes connected with
tearing it down, expending its energies for the per-
formance of work. Roughly, these distinctions are
like those between saving and spending. Naturally,
one cannot spend without having accumulated, but
at any particular time; one or the other process may
THE CELL AND ITS ACTIVITIES 19
be the leading one. During the period of growth
anabolic tendencies are uppermost ; females, on the
whole, are more anabolic than males, since they save
not only for themselves, but for a future generation.
Male insects, in particular, may be short-lived and
intensely active when they become adult — rapidly
spending, as it were, the accumulations of their earlier
life.
8. In accordance with these general principles, the Food
cell takes in and gives out substances — solid, liquid,
or gaseous. It is nourished by food. This food may
be of various kinds, but it is not identical with the
living protoplasm of the cell. Even when one animal
eats another alive, the victim is reduced to non-living
material of a relatively low grade before it can be
utilized as food. This food material is not put together
to form new cells ; it is built into the existing cells,
bit by bit, as infinitesimal particles. So only may the
cells grow, and the body grow by the increase of ma-
terial in cells which consequently divide to form new
cells. The process of thus taking in material and
making it part of the living stuff is called assimilation,
or "making like." Thus it is that the cells already
present at any time control the future growth ; with-
out their aid, nothing avails.
9. Material is given out by the cells, as a result of Diverse
their metabolism. Carbon dioxid (CO2), a stable or CgJJg °
static compound of carbon and oxygen, is the result
of a kind of combustion, in the course of which energy
is "liberated"; that is to say, appears in the form of
work or heat. This matter will be dealt with later in
connection with respiration. This carbon dioxid is a
gas, but there are also fluid and solid products of cells.
The bone cell entombs itself in a limy deposit. The
20 ZOOLOGY
fat cell is entirely given over to the production of an
oily substance. The cells of the stomach wall secrete
small quantities of hydrochloric acid, which, in greater
amount would be a violent poison. All cells give rise
to waste products, the results of their katabolic pro-
cesses. In general, we speak of the waste products as
excretions, of the useful products as secretions. The
marvel is, that different cells, all nourished in essen-
tially the same way, can secrete entirely different
substances, acid or alkaline, solid or liquid, accord-
ing to their appropriate function. The mother's milk
and the poison of the snake are equally products of
cell activity.
10. So astonishing is this power of cells to take up
ordinary nourishment and out of it elaborate the
most extraordinary and unique substances, that we
are prepared to believe that their ability is wholly
independent of the character of the food. This is not
really the case. No cell can change one of the chemical
elements into another, or produce a secretion contain-
ing a particle more of a given element than was con-
tained in the food. Thus, for instance, if the food of
babies is deficient in the element calcium, which goes
toward the formation of the hard parts of bones, the
result is the condition known as rickets. The man
who dilutes the milk may be responsible for rickety
children, whose bones become bent and deformed,
because they are deficient in lime. An abundance of
other substances will not make up for the deficiency.1
1 Certain authors state that rickets is not due so much to deficiency of
lime in the food, as to an abnormal state of the body in which the lime is
not adequately deposited. In the absence of lime-containing food, the body
can produce no lime ; but under certain conditions, though it is supplied, it is
not properly utilized.
THE CELL AND ITS ACTIVITIES 21
Many years ago the baby lions in the London zoological
gardens died in numbers in spite of the fact that the
animals were well housed and given expensive food.
In Dublin, where conditions were not supposed to be
so good, the young lions lived. It turned out that the
death of the London lions was owing to a rickety con-
dition of the base of the skull, and this in turn to a
deficiency of lime in the milk of the lionesses. This
deficiency appeared to be owing to the fact that the
beasts had been fed on good cuts of meat, with too
little bone. In Dublin, where they could not afford
to treat them so well (as they considered it), they
gave them more bone and less meat, with the good
results already mentioned. Thus, while the cell can
do marvelous tricks of conjuring, there are limits to
its powers.
CHAPTER FOUR
Organs and
tissues
Epithelial
tissue
THE TISSUES
1. THE animal body consists of more or less dis-
tinguishable parts or organs, having characteristic func-
tions. These organs are made up of tissues, which are
aggregates of cells of particular kinds. As we- survey
the different groups of animals, we observe that the
organs essentially correspond throughout long series.
Thus even a fish has eyes, nostrils, and mouth corre-
sponding with those of man. Coming to the tissues, we
observe even closer similarities, and are obliged to con-
clude that the kinds of tissue were mostly evolved quite
early in the history of life. In spite of the astounding
diversity in the form of living beings, the hundreds of
thousands of species, the materials of which they are
made show comparatively little diversification. An
enumeration of all the known types of tissue does not
require much space. It is, of course, true that the
similar tissues of diverse animals are not exactly alike ;
but they are of the same general character and behave
in analogous ways, so that we classify them under gen-
eral headings, and find that one description will suffice
to indicate their main features. The following account
is based primarily on the tissues of man.
2. Approaching the animal from the outside, we
meet first with the epithelium. This may be defined as
surface tissue, but the surfaces which it covers may be
external or internal. The outer covering or skin is con-
tinuous with' the more delicate lining of the mouth, and
that in turn with the surface of the windpipe and gullet.
The epithelium may consist of a single layer of cells, as
in the intestine, or of many layers, as in the skin. The
absorbent surface of the intestine is necessarily thin ;
22
THE TISSUES
but the skin, protecting the body from the buffeting of
the outer world, requires, as it were, several lines of
defense. The outer layers are contin-
ually being worn away, but others are
beneath, ready to take their place.
Epithelial cells are of two principal
types, squamous or scale-like and col-
umnar or column-like. Squamous
cells are easily obtained for examina-
tion by gently scraping the roof of the FIG. 2.
mouth. The surface layers of the skin,
or epidermis (epi, upon, dermis, the
skin), are also flat, the outermost cells
upward and sweep the
mucus, dust, and germs
From Ritchie's "Hu-
man Physiology"
Cells from the
lining of the trachea,
a is a cell that manu-
factures sticky mucus
(b) in which dust and
. germs from the air are
becoming horny as they lose their vi- caught. The cilia (c)
tality. In the intestine the cells are on the other cells beat
columnar, and also in the trachea or
windpipe, where they have in addition UP °ut °f the air pas-
r • i • ,1 j sages and lungs.
a covering 01 cilia on the exposed sur-
face. These cilia, moving somewhat like the oars of a Ciliated
boat, are very fine protoplasmic threads of no great "achea the
length. Their activity depends upon the life of the
cell, not upon that of the whole organism, and they may
be seen in motion under the microscope after removal
from the body. Their function is to convey upward to
the mouth the innumerable fine particles of dust which
exist in the air we breathe, and adhere to the moist sur-
faces of the air passages.
Horns are special developments of epidermal tissue, Horns and
characteristic of certain hoofed animals. The horn core antlers
of the ox, which is a bony extension of the skull, is
covered with true horn of epidermal origin ; and hence
the horn when removed is hollow, and may be used by
Little Boy Blue and others to produce a sound. The
antlers of deer are outgrowths of bone, and are thus
ZOOLOGY
quite different from horns. A corn (Latin cornu, horn)
is a horny thickening of the epidermis in response to
pressure ; an expression of a tendency which has re-
sulted in various useful adaptations, but which in this
case is distinctly injurious.
3. The term " connective tissue" is used in a general
sense to include the inner framework of the body, or
more specially and accurately to denote the fibrous ma-
terial which unites the various cells and groups of cells
much as cellulose does in plants. It does not, however,
arise from the other body cells, nor is it secreted by
them ; it consists of special cells of relatively primitive
type, with their secretions, modified to serve mechanical,
ends. It is probably because connective tissue cells re-
main in a relatively unmodified condition while nerve
and muscle cells are becoming exceedingly specialized,
that they are capable later on of assuming so many
different forms and func-
tions. They may produce
elastic or non-elastic fibers,
A B
From Ritchie's "Human Physiology"
FIG. 3. Connective tissue. In its first
stage connective tissue is a group of
cells which build around themselves a
mass of jelly-like material, as shown
in A . This material hardens into the
fibers that are seen between the cells
in B. All through the body a frame-
work of connective tissue runs, holding
the cells, organs, and tissues in place.
From Ritchie's "Human Physiology"
FIG. 4. Bone cells. These much-branched
cells deposit around themselves bone ma-
terial (6), thus building bones to support
the body. The bone cells build a net-
work of fibers like dense connective tissue
and then fill the spaces between the
fibers with hard mineral matter, a is a
cavity from which the bone cell has been
removed.
THE TISSUES 2$
or cartilage and ultimately bone, or store up oily mate- Fat cells
rial and become fat. Or again, they may develop
Drawing by R. Weber
FIG. 5. Development of a fat cell. The black spot is the nucleus. The original
cell is of the type of connective tissue cells. Globules of fat are developed in the
cytoplasm ; these run together and increase, until at last the whole cell is a mass of
fat with a thin outer covering consisting of what is left of the cytoplasm, the nucleus
pushed to the wall. In this way material is stored up in the body, to be utilized
later as a source of energy. Sometimes cells whose normal function is not that of
forming fat behave in a similar manner. The result is fatty degeneration, a very
serious'disease. Pathological (diseased) states are often due to developments which
in another place, or at another time, would be normal and beneficial ; just as crimes
are often actions which under other circumstances would be desirable. The per-
version of functions is a great source of evil.
abnormally, and produce tumors (Latin tumor, a swell-
ing) dangerous to life. In general terms it may be said
that connective tissue cells have special powers of pro-
ducing or secreting substances which serve mechanical
ends, or, in the case of fat, afford a means of storing
up fuel to be later utilized by the body. The material
they use is derived from the food, but they have the
power of selecting the raw materials and converting
them into what may be fairly termed manufactured
products.
4. It is contrary to familiar usage to call the blood a Blood
tissue, yet from the standpoint of the physiologist it
cannot be otherwise considered. In cartilage we have
a number of cells, separated by a solid substance. In
blood we similarly have cells, but they are in a fluid
medium, the plasma. It is necessarily so, since the
blood flows, serving as a means of communication be-
tween the various parts of the body. The blood vessels
26
ZOOLOGY
are the streets through which traffic has to pass, in
order that every part may be served with the food and
The leuco-
cytes or
white cells
Drawing by W. P. Hay. after Perrier
FIG. 6. Blood corpuscles of various animals, a, human red blood corpuscles;
b, red and white corpuscles of the pigeon; c, red corpuscles of a frog; d, red and
white corpuscles of a snake ; e, red corpuscles of Proteus ; /, colorless corpuscles of
a sphinx caterpillar ; g, colorless corpuscle of a river mussel. All magnified to the
same degree.
oxygen necessary for life, and the waste materials may
be removed. The principal cells of the blood are known
as the red and white corpuscles, the former vastly more
numerous. The red cells, which appear pale yellowish
when seen singly, are the carriers of oxygen. The white
cells, really colorless rather than white, are capable of
motion in the manner of simple Protozoa. They have
been called the policemen of the blood, because they
attack and devour injurious bacteria and other particles.
They are more efficient perhaps than the policemen of
our streets, since they execute sentence and effectively
dispose of the criminal at the moment of making the
arrest. This process is called phagocytosis, and is re-
garded as one of the important ways of protecting the
body from disease. It is, however, less important than
was formerly supposed, since the blood-fluid (serum) it-
THE TISSUES 2J
self often kills the bacteria ; while on the other hand the
white cells are not always able to destroy the bacteria,
even by devouring them. There are reasons for think-
ing that the white cells may secrete a substance poison-
ous to bacteria, and thus destroy them without con-
suming them.
5. Muscle is the tissue concerned with movement, Muscle
which may be either that of a part of the body, as the t
heart, or that of the whole organism. There is, of
course, a great deal of movement going on, as, for ex-
ample, that of absorption, which is not controlled by
muscle ; but the gross and obvious movements are nearly
all muscular. Muscle cells are elongated, like very
slender worms attached together in bundles. Their
function is, of course, to contract, which they do in
response to a stimulus. This is not in itself a special
function of these cells ; the primitive one-celled amiba
also contracts under suitable conditions. The muscle
cell, however, has the same sort of relation to an amiba
that an express train has to a person walking along the
road. The walker does many things which the train
does not, but the train is extraordinarily specialized for
going, and for going in a particular way along a par-
ticular track, under the control of an engineer. In the
case of the muscle, the engineer is the nerve.
Those muscle cells which are under voluntary control Voluntary
are striated, showing fine cross-lines in the manner of a musce
file. This is equally true in vertebrate and invertebrate
animals. Unstriated muscle is not under the control of
the will ; such, for example, is the muscle which causes
the movements of the intestine. The distinction here
made is not absolute, however, for the heart muscle is
striated. The fibers of the heart are in fact somewhat
intermediate in structure between the two great classes
28
ZOOLOGY
just defined, but it is fortunate for us that they require
no effort of the mind to call them to activity. It must
also be said that even the typical voluntary muscles
carry on most of their work with, as it were, only
general instructions from the nervous centers. In walk-
ing or writing, for instance, we are wholly unaware of
the details of muscular movements, though we will the
operations in a large and general sense. Reflex centers,
uncontrollable by the will, often dominate the move-
ments of so-called voluntary muscles.
6. Nerve tissue has to do with the conveyance of
stimuli along definite paths. The old primitive gen-
eralized response is modified in such a manner that
messages are flashed from the surface to the brain or
spinal cord, and thence back to the muscles of the part
affected by the stimulus, in much less time than it takes
to tell about it. Psychologists have determined by
actual experiment that the transmission is not in-
Drawing by R. Weber
FIG. 7. Diagram of a nerve cell. M = muscle-fiber. N = nucleus. The arrow
indicates the direction of the external stimulus. The disturbance set up is com-
municated along the nerve-fiber, as along a telegraph wire, to the muscle-fiber,
which thereupon contracts. The muscle is in the ulterior of the body, but is able
to react to events going on outside. The diagram illustrates a very simple type.
In the higher animals the usual course of events is different. The impulse is com-
municated to the brain or spinal cord, and the central nervous system sends out a
call through an efferent (out-carrying) nerve for action. Volition comes into play,
and reactions may be controlled by the will. Thus it is possible by an effort to
avoid sneezing.
THE TISSUES
t A
> o
stantaneous ; it takes an appreciable and measurable Nerve cells
time. Formerly it was supposed that the nerve fibers,
which seem to present no
cellular structure, were not
parts of cells. We now
know that the nerve cell,
with its nucleus, is pro-
longed into fiber-like exten-
sions, reminding us of the
pseudopodia of the amiba,
but vastly longer, and per-
manent. Bundles of these
fiber-like filaments consti-
tute the nerves. The gen-
eral property of irritability
is here greatly accentuated,
and the impulse is capable
of being conveyed to other
kinds of cells, which act in
consequence of it. So far
we seem to be dealing with
nothing more than an ex-
treme modification of prim- of secretions. A represents the simplest
itive functions, but when case' in which tluree ceUs (shaded) are
capable of secreting some substance,
we come to regard mental which is poured out on to the surface o£
phenomena, especially as the body- In B the sland cells secrete
r i . into a pocket or tube, which is capable
found in man, we enter upon of holding the material until it is
a new field. The power of wanted, as in the case of the saliva or
i ^i • the secretion of the stomach (gastric
memory may be theoreti- juice). This makes it ^Me to furnish
Cally explained as analogous at a given moment much more of the
to that of the phonograph ; secref d ™*5t™ce ^han lThe cf ls coxf
J ' supply without notice. In plants the
a path Of disturbance lias gland cells are often situated on a
left its record in the brain. knob or Prominence or at the end of a
TTT, . hairlike structure, thus reversing the
When We Come tO COnSClOUS- structure of the tubular gland.
FIG.
section.
Drawing by R. Weber
Diagrams of gland cells, in
The arrows mark the outflow
ZOOLOGY
Glands
Excretion
and secre-
tion
ness and reason we appear to transcend all rational
explanation ; the intellect, powerful though it may be,
cannot understand itself. It is better frankly to admit
our ignorance than to clothe it in words which sound
learned but mean little.
7. Gland tissue, consisting of the cells secreting the
saliva, gastric juice, sweat, etc., is a modified form of
epithelium, in which the functional significance is en-
tirely altered. These cells, like many of the connective
tissue group, take up material from the blood, and from
it produce special substances according to the kind of
gland. The closed cavities of the body are lined with
glandular epithelium, secreting serum. The largest
gland in the body is the liver ; developing from a pocket
or depression in the wall of the alimentary canal, it as-
sumes great complexity, both in external features and
minute structure. The pancreas and kidneys are also
glands, but the latter serves to excrete waste products
from the blood, instead of producing a substance to be
subsequently utilized. Physiologically speaking, secre-
tion and excretion are not essentially different ; but in
the former case the product is utilized, in the latter it is
waste.
CHAPTER FIVE
RESPIRATION
1. WE ordinarily think of respiration, or breathing, Adaptation
, f , . , , rr<i . totheat-
as the process of taking air into the lungs. 1 he air mosphere
we thus breathe consists of various gases, principally
nitrogen and oxygen. The oxygen, approximately one
fifth of the whole, is the part used in respiration. Al-
though nitrogen is an important constituent of proto-
plasm, the nitrogen of the air cannot be taken up by
the animal body. It serves to dilute the oxygen, and
the body is so constructed that the particular mixture
forming the atmosphere near the surface of the earth is
best suited to its needs. This relationship is called ad-
aptation, and it is obviously the body which is adapted
to the atmosphere, not the atmosphere to the body.
2. Respiration, however, does not necessarily re- The use of
quire lungs, or any visible process of breathing. It is
common to all living beings, cells or individuals, plants
or animals. Life requires free oxygen, which in
animals is obtained from the air. Green plants are
able to make sugar or other carbohydrates (containing
carbon, hycjrogen, and oxygen) from carbon dioxid
(CO2) and water (H2O), and in the process free oxygen
is liberated. Lower plants, yeasts, and bacteria are
able to bring about fermentation, in which oxygen-
containing molecules are broken up. Thus, in one
way or another, all living cells get access to oxygen,
though they may live in the absence of air, as do the
anaerobic (Greek, "living without air") bacteria.
The higher plants have innumerable stomata (Greek,
stoma, "a mouth"), little apertures in the surfaces of
the leaves, through which air, containing small amounts
of carbon dioxid, is able to enter.
31
32 ZOOLOGY
Forms of 3- Why should free oxygen be so necessary? It is
energy needed for the process known as oxidation, in the course
of which energy is released or made manifest. Stu-
dents of physics speak of potential or latent energy,
and kinetic or active energy, states which may alter-
nate, while the sum total of energy remains the same.
When energy becomes potential, it is just as though
matter were to disappear into a fourth dimension of
space ; it exists, but cannot be appreciated. The
conception of potential energy is thus in a sense meta-
physical, but the ordinary experience of mankind
makes it commonplace when we recall the lifted weight,
the bent spring. We know very well that when we
lift a lo-pound weight a foot, we expend or use a
definite amount of energy ; and that if we set the
weight upon a shelf it will stay there, ready to liberate
the same amount of energy at any time by falling on
our toes or otherwise. The agent which disturbs the
weight — knocks it off the shelf — does not make the
energy, but only sets it free.
Work 4. The oxygen unites with carbon, forming the very
stable or static compound known as carbon dioxid,
with the chemical formula CO2. This is a. gas, heavier
than air, and is given off through the respiratory ap-
paratus. Carbon and oxygen have a chemical affinity
for each other, and from the standpoint of the present
discussion may be compared to the weight and the
earth, attracted together by gravitation. The falling
weight and the uniting atoms display kinetic energy,
and work results. The word " work," in biological dis-
cussions, is used in the broadest sense, to describe all
the life activities; so that even a sleeping person is
said to be doing work, or at any rate the organs of his
body are. The beating of the heart is only an obvious
RESPIRATION 33
example of what is going on in every part, and the
essential feature of all is movement.
5. If kinetic energy is displayed as movement, it Modification
need not be of a gross or visible character. Much of of energy
it takes the form of heat, which we may be able to feel,
but cannot see. It may appear as light, even in the
living animal, such as the glowworm (a beetle), which
produces a bright light with amazingly little expendi-
ture of energy. Or again, it may be represented by
nerve impulses, conveying messages to and from the
brain ; or by muscular contractions, enabling us to
work in the more ordinary sense of that word. The
oxidation process therefore provides the power which
runs the machine, and without it life activities
cease.
6. When we try to define oxidation, the first ob- Combustion
vious thought is that it is combustion. When coal
burns in air, the carbon and oxygen unite, carbon
dioxid is formed, and energy is liberated to warm us or
to run an engine. In modern chemistry the matter
is more closely defined, and the term oxidation has
come to include a certain type of reaction, no matter
whether oxygen is present or not. It is a reaction in
which there appears to be a transfer of electrical
particles or electrons, and thus we come back to the
alternation of electric states as the source of the dy-
namic properties of the living substance. At this point
we are near the limit of our present knowledge, and
proceeding thence, science will probably make nota-
ble gains in the not distant future.
7. When oxidation takes place, something is oxidized Oxidation
or burnt. The source of the oxidized material is the
food, but not necessarily directly and as such. When
yeast causes alcoholic fermentation, grape sugar
34 ZOOLOGY
(C6Hi2O6) is broken up, and the oxygen momentarily
liberated combines with carbon to form carbon dioxid,
while the residue (C2H6O) is alcohol. In this case
the process is simple, direct, and rapid, but ordinarily
it is quite otherwise. Various substances may be
taken into the body and oxidized without previous
change, to a greater or less extent. This is true of
alcohol, and this is why it has been claimed that alcohol
has a certain food value. The more typical foods,
however, are those materials which are broken up or
reduced and then built up into the living substance
itself. This is the anabolic process, and the opposite
or katabolic process is that in which this living material
is oxidized with the production of work in the sense
already defined. Thus we finally see that respiration
has to do with the life activities of every cell, and the
conception of it as taking place merely in the lungs is
quite erroneous. Breathing is seen to be merely a means
directed toward a respiratory process which is going
on all over the body.
Blood a 8. There is plenty of evidence showing that the
oxygen °f oxygen absorbed by the lungs is not all used up in
those organs. The red corpuscles (red only in mass)
in the blood contain a substance called hemoglobin,
which readily takes up oxygen, but also readily gives
it up. The corpuscles, circulating with the blood,
carry the oxygen to every part of the body. Much,
though by no means all, of this oxygen is set free in
the smallest vessels, and the blood returning to the
heart in the veins contains less oxygen and correspond-
ingly more carbon dioxid, the product of combustion.
The difference in color of the blood is connected with
these changes ; the arterial blood, rich in oxygen, is
bright red ; the venous blood, dark purple.
RESPIRATION 35
9. Since respiration is an essential, vital function, Adaptive
we find many beautiful adaptations connected with
it. The body is suited to what may be called normal
conditions, but under special circumstances it has the
power of adjusting itself to a certain extent to the en-
vironment. Thus Dr. E. C. Schneider and others
made experiments on Pike's Peak, Colorado (14,109
feet above sea level), and found that at this high
altitude the rate of blood flow was increased from 30
to 76 per cent, and the number of red blood corpuscles
in circulation was very appreciably increased. Ob-
viously such changes would facilitate the carriage
through the body of the diminished supply of oxygen,
and thus make up for the disadvantages of the rarefied
atmosphere. Such plastic adaptations, if we may so
call them, have of course their basis in the structure of
the organism, just as in the case of an automobile
constructed to run on "high" or "low."
10. The evolution of the respiratory apparatus in Evolution of
diverse forms is very interesting. In the lowest
animals oxygen is merely absorbed through the surface
of the body. These animals being aquatic or parasitic,
the oxygen obtained is that dissolved in the fluid,
usually water, in which they live. The amount re-
quired may be small, but differs in different forms ;
thus coral animals flourish only where the water is in
motion, near the surface, especially where there is surf.
The tumbling waters inclose many bubbles of air, and
some of the oxygen is dissolved. Many aquatic animals,
as mollusks (Fig. 66, page 249) and various insect larvae
(young of May flies, etc.) possess external gills, which
are branched processes of a delicate nature, rich in
blood vessels. These take up oxygen, but in some
cases serve the needs of the animals only under special
environments. Thus May fly "nymphs," as they are
36 ZOOLOGY
called, get along very well in running streams, where
fresh water, with its oxygen, is constantly passing
by. Brought into a laboratory and placed in a dish
of water, they die overnight of suffocation. In the
amphioxus and the lower vertebrates we find a notable
advance of structure, the development of gill arches.1
The new plan enables the animal to cause a current of
water to flow through the gills, thereby giving all the
advantages of a running stream, even when the sur-
rounding water is quiet. The next great advance is
connected with the discovery of the land. Land life
implies the breathing of air, and yet it is not possible
to do this without some sort of moist chamber, in
which water will be constantly present and the delicate
blood vessels will not be in danger of desiccation. In
the insects and their relatives this end is gained by the
system of trachea, branching tubes connected with
small openings, or spiracles, on the sides of the body.
In the higher vertebrates, and also in most of the land
snails, the structure takes the form of one or more sacs,
known as lungs. Lungs in the vertebrates are in pairs,
and in the lowest forms are simple, moist cavities.
In warm-blooded animals, which have to maintain a
constant temperature, and are generally very active,
the need for- oxygen is greatly increased. This cannot
be met by a corresponding increase in the size of the
lungs, which would assume the dimensions of balloons ;
so there arises instead an amazing complexity, which
gives an enormous increase of surface for absorption,
without any great addition to the external dimensions
of the organ. The spongelike tissue presents a vast
number of little cavities, into which air enters, and
through the walls of which gases pass.
1 Young lungfishes and amphibians, and some adult amphibians, have
external gills.
CHAPTER SIX
THE INDIVIDUAL
1. WE always think of the individual as the natural Thcin-
unit of life. The very word implies indivisibility in the iJ^oMi
sense that the whole is something different from a mere
aggregation of its parts. This idea is not without sup-
port from analogy. The atom, the molecule, even the
cell, — each possesses this property of individuality.
They do things as wholes, which their parts could not
do separately. They behave as machines, the several
parts of which cooperate for a common purpose. Surely
the individual animal or plant also so behaves ; is a
workable machine, a whole which may not be divided
without destroying its characteristic functions.
The fact that reproduction is -division has no bearing
on the argument. We have seen that in the many-
celled animals the reproductive cells are set aside, and
are not part of the machine, except in an indirect sense.
Therefore it is reasonable to say that the production of
young is no infringement on the wholeness or individ-
uality of the parent.
2. Nevertheless, upon further inquiry, it becomes The in-
hard to define the individual in a biological sense. It hard to
would be simple to say that the individual is the prod- definc
uct of a single fertilized egg cell. This is ordinarily but
not necessarily the case. Dr. Jacques Loeb made some
experiments with sea-urchin eggs, placing them soon
after fertilization in sea water greatly diluted with dis-
tilled water. In this mixture the eggs took up so much
water that their enveloping membranes burst and part
of the protoplasm escaped in the form of a globule or
drop. The eggs were then returned to normal sea
water, and in due course developed. When the ex-
37
ZOOLOGY
Identical
twins and
double
monsters
Poly-
embryony
truded drop of protoplasm had become entirely sepa-
rated, both it and the portion left within the membrane
developed, producing two individuals from what was a
single fertilized egg. When the drop was not com-
pletely separated, a double monster was produced, a
pair of individuals joined together.
3. The sort of thing which happened in Loeb's ex-
periment occasionally occurs among the higher animals
without any intentional disturbance. Calves or chick-
ens have two heads or more than the normal number of
legs. Even in man we have such cases as that of the
famous Siamese twins — two individuals connected by
a band of living tissue. It is not so generally under-
stood that this process of division, carried to comple-
tion, gives rise to what are called "identical twins."
Such twins, always extraordinarily alike, and of the
same sex, are due to the division of a single zygote or
fertilized cell. They have exactly the same inheritance,
and are thus of great interest to biologists because they
afford a means of testing the effects of environment,
which is the variable factor, the other being constant.
According to the suggested definition of the individual
given above, they are parts of the same individual,
although of course no one really so considers them.
4. This division of the fertilized cell not only occurs
under experimental conditions and as a rare "accident,"
but in certain animals is a normal occurrence. There
are certain minute insects which regularly exhibit poly-
embryony, the zygote splitting up into a considerable
number of individuals. Professor H. H. Newman has
shown that in the nine-banded armadillo of Texas poly-
embryony regularly occurs, four individuals being pro-
duced by a fertilized egg cell. These, as in the case of
identical twins, are always of the same sex and very
THE INDIVIDUAL 39
much alike. They differ to the same extent that the
two sides of any single individual may differ.
c. The question of the individual may be discussed Processes
. of regenera-
from another standpoint. When we accidentally knock tion after
off a small piece of skin, the wound heals ; but if we mjunes
lose a finger, no new finger grows in its place. A lizard,
however, may lose its tail, and a new tail grows. If the
tail is broken at one side, sometimes a tail begins to
grow at the point of fracture, and two tails result.
Going to a lower level in the scale of animal life, we
find that the arm of a starfish, removed with a certain
amount of the disk, will grow new arms and eventually
form a whole starfish. Many of the lower invertebrates
may be divided into two or more' parts, and each part
FIG. 9. Renilla, a compound animal, living in the sea
(Phylum Ccelenterata, Order Alcyonaria).
will regenerate what it lacks, producing a whole in-
dividual. This is not the division of ordinary reproduc-
4o
ZOOLOGY
Colonies of
polyps
Human
personality
tion, not even a normal budding process, but a violent
tearing apart of the individual, the parts of which con-
tinue to function nevertheless. A man cannot be so
treated, and survive ; but there is every transition be-
tween the process of healing in a wound and that of
complete regeneration of two individuals upon division.
6. The individual is elusive also in those lower forms
of life which exist in groups or colonies, such as the
zoophytes or hydroid polyps. These animals occur in
numbers on a common stem, through which nourish-
ment passes. On account of this arrangement it is
possible for the individuals to assume very special
functions, some for feeding, some for defense, others for
reproduction. Are they really separate "persons"?
In spite of their intimate union, they must be so con-
sidered, and indeed in many species the reproductive
persons at length float away as independent organisms.
7. All these considerations show how difficult it is to
define the individual in biological terms ; yet we have
no doubt about the "oneness1" of our personality.
There is a side to this question which transcends bio-
logical reasoning; but the biological facts, so far as
they go, are of the highest significance.
CHAPTER SEVEN
MENDELISM
FIG. 10. Gregor Johann Mendel, at about
the age of 40.
i. GREGOR MENDEL Life of
was born on July 22,
1822, in Austrian Si-
lesia. As a boy he so
distinguished himself in
school that his parents
decided to give him
unusual advantages,
though at considerable
sacrifice to themselves.
His younger sister con-
tributed part of her
dowry that he might
continue his education.
The result was that,
instead of becoming a
farmer like his father,
he was admitted into
the Augustinian house of St. Thomas at Briinn, where
he was expected to take part in the educational work
of the institution. In 1847 he was ordained a priest.
As a teacher he was so successful that at the expense of
the cloister he was from 1851 to 1853 sent to the Univer-
sity of Vienna, where he studied mathematics and the
natural sciences. He studied under the entomologist
Kollar, and in 1853-1854 published two short papers on
insects. Returning to Briinn, he not only continued his
teaching, but carried on experiments with plants and
honeybees. Although it is known that his experiments
in hybridizing bees were quite extensive, the results
were never published and have apparently been lost.
41
42
ZOOLOGY
Mendel's
guiding
principle in
crossing
plants
Fortunately his work with plants, which led him to the
remarkable generalizations now everywhere associated
with his name, was described at some length in papers
communicated to the natural history society of Briinn.
Mendel's originality and sagacity were shown at the
very beginning of his work, in his selection of plants
with which to work. The problems which interested him
were those of inheritance, and he saw that it was neces-
sary to find plants which possessed constant and easily
recognizable differentiating characters, but which would,
nevertheless, cross without any marked impairment of
fertility in successive generations. It was also desirable
to find a species which could be easily grown, and would
not be too liable to cross-fertilization by insects, which
would of course spoil the statistical results. The great-
est discoveries in science have usually been made with
the most commonplace materials, and in this case
Mendel chose for his principal investigations the or-
dinary cultivated pea, in its several common varieties.
2. Mendel worked for eight years with his peas, and
when he came to publish his results, he stated his guid-
ing principle as follows :
"Those who survey the work done in this department
(of hybridization) will arrive at the conviction that
among all the numerous experiments made, not one has
been carried out to such an extent and in such a way as
to make it possible to determine the number of different
forms under which the offspring of hybrids appear, or
to arrange these forms with certainty according to their
separate generations, or definitely to ascertain their
statistical relations. It requires some courage to under-
take a labor of such far-reaching extent ; this appears,
however, to be the only right way in which we can
finally reach the solution of a question, the importance
MENDELISM 43
of which cannot be overestimated in connection with
the history of the evolution of organic forms."
Although Mendel modestly implied that any one who
might survey the past work would arrive at the convic- •
tion mentioned, it was in fact due to his quite excep-
tional and extraordinary insight that he was able to put
his finger on the weak point in previous investigations,
and plan others according to "the only right way" to
resolve the difficulties and uncertainties surrounding the
subject. We have here a beautiful example of the
scientific method, — not working at random, but fol-
lowing a carefully thought-out plan, developed after a
full consideration of what was previously known.
3. In order to carry out the experiments planned, it study of
was necessary to choose varieties of peas which differed characters
in some marked characters, and cross one with another. "* Peas
Thus the ripe peas may be either smooth (or with only
shallow depressions) or angular and wrinkled ; they may
be green or various shades of yellow. The oods may be
deeply constricted between the seeds, or lack this char-
acter. The stem may be short or long. These and
other characters were readily observed, and it was noted
that they represented opposites, as smooth or wrinkled,
green or yellow, tall or short, etc. Mendel now crossed
plants having such opposite characters, and watched
the inheritance of these particular characters, not es-
pecially concerning himself with the other parts or
peculiarities of the plants.
4. At the outset Mendel noticed that the offspring Dominant
of his crosses were not intermediate between the parents. *?* ™caer^
On the contrary, in respect to the characters studied, acters in
they closely resembled one or the other parent. Of
each pair of opposing characters, one appeared in the
offspring, the other being absent. Not only this, but
44
ZOOLOGY
all the plants resulting from a cross were alike in this
respect, and it made no difference which was the seed
and which the pollen parent. Thus, on crossing
smooth-seeded with wrinkled-seeded varieties, only
smooth-seeded plants were produced. Plants from
green seeds crossed with those from yellow seeds gave
only plants with yellow seeds. Tall with dwarf gave
only tall. The character which thus appeared Mendel
called dominant; the other, which disappeared, reces-
sive.-
Discovery 5- When the plants resulting from such crosses were
of the crossed together, or produced seeds by self-fertilization,
three-to-one . , 11111.
ratio the next generation showed both the dominant and re-
cessive characters, without any intermediates. After
elaborate statistical studies, Mendel discovered that
the numerical relations between the two sorts in the
grandchildren of the original cross were substantially
constant, following what appeared to be a definite law.
Of every four individuals, on the average, three showed
the dominant character and one the recessive. Al-
though the immediate parents had exhibited no trace
of the recessive character, it reappeared in apparently
pure and uncontaminated form in one fourth of their
offspring.
6. Mendel did not stop here, but continued his ex-
periments, breeding together the plants obtained as just
described. He found that when the extracted recessives
(as they are called) were bred together, they gave only
plants showing the recessive character, no matter how
many generations were produced. With the dominants
it was different ; some gave only dominants, and others
again split up into dominants and recessives, in the pro-
portion of three to one. It was eventually determined
that of the three dominants, one came pure, while the
Allelomor-
phic or
alternative
characters
MENDELISM 45
other two split up. Thus, of the whole series of grand-
children exhibiting the 3 to i ratio, half, when bred to-
gether or self-fertilized, came true, and half gave 3 to
i again. 'The half coming true consisted of one domi-
nant and one recessive out of each four ; the other half,
of two dominants.
In discussing such experiments, we now call the
original cross, or parental generation, P ; the following,
or filial generations, /\, jF2, F^ etc. It must not be
forgotten that these terms are purely relative ; the P
represents the F\ of its parents, the Fz of its grand-
parents, and so forth.
The characters which act as opposites in inheritance,
in the manner described, are said to be allelomorphic.
7. The principal facts brought out by the experi- Detennin-
ments have now been described, but how may they be ?[ deTetop-
explained ? Mendel observed that the characteristics ment give
studied were -inherited as units, and when he used "haracters
plants having two pairs of opposite characters, he saw
that the inheritance of one pair was independent of the
inheritance of the other. That is to say, there was no
connection between size and the color of the seed, or
between the color of the seed and its smooth or wrinkled
surface. There was a connection between the color of
the seed coat (white or gray to brown) and the color of
the flowers, however. Obviously the inherited thing is
not a particular- color or size or surface, but something .
which so acts in development as to produce these
effects. This something, which may be called a de-
terminer, may produce only one visible effect, or many.
In the examples cited in the preceding paragraphs there
was only one effect considered or noted for each de-
terminer. Of each pair of opposites only one can ap-
pear in a given individual ; but if there are several
46
ZOOLOGY
pairs, A-a, B-b, C-c, etc., then A is just as likely to
occur with B as with b, and B with C as with c.
Modern research has shown that while the simple
cases recorded by Mendel are typical, there are nu-
merous exceptions, which are explained by various ex-
tensions of the theory, without at all contradicting
Mendel's essential results.
8. Not only are the determiners inherited as units,
but they ordinarily remain unmodified, whether they
produce any visible features or not. We are reminded
of the phenomena of chemistry. Thus oxygen and
hydrogen, two gases, when united become water, which
is not at all like either of them. An atom of oxygen
may today be part of water, tomorrow part of iron
rust, and the third day again appear as oxygen, not in
the least changed by the temporary loss of its ordinary
properties. It is quite certain that the determiners are
not chemical atoms, they are doubtless thousands of
times more complex than that; nor do they form
chemical combinations as do the atoms, but they re-
semble them in their stability and reappearance after
having seemed to cease to exist.
9. Having thus postulated the existence of inde-
pendently inherited determiners, pairs of which are
mutually exclusive, we can proceed to develop a theory
of Mendelian inheritance. Each plant (or animal) is
double or duplex, in the sense that it inherits or receives
one set of determiners from each parent. Should the
two sets be alike, we say that the individual is pure-
bred, technically homozygous; should they be different,
it is cross-bred, or heterozygous. We may express the
facts by formulae, as did Mendel, in which, however, we
cite only the characters with which we are immediately
concerned. Let a pure-bred tall pea (TT) be crossed
MENDELISM 47
with a pure-bred short or dwarf pea (#), the offspring
will be tall, but will have inherited determiners for both
characters. Its formula will be Tt. Of course the
formula for the whole plant (something no one has yet
tried to construct) would be excessively long and com-
plex, but we confine ourselves to one or a few pairs of
characters. We are in the position of a man who might
be looking at a crowd. He could not follow the move-
ments of all the individuals at once, but he could select
any one or two individuals and see exactly where they
went and what they did.
10. Now it appears that while each individual has Only half of
two sets of determiners, he can give to his progeny only
one of these; otherwise the number would be double passed to
in each generation. So the cross TT X tt (we use X spring
to signify crossing) gives us 7V, and can give nothing
else, because each parent contributes one item, and the
one has only T to give, the other only t.
The Tt plant is tall, because tallness is dominant and
dwarfness is recessive.
II. Suppose we take the F\ individuals, which are, as So-called
we have said, Tt, are cross-bred or heterozygous, and ^nc^m
cross them together, thus : Tt X Tt. Each parent can inheritance
now give T or t, and gives either quite without choice
or discrimination — as we say, "at random." Let us
follow the fortunes of the first Tt. Of this pair, the T
goes out, and is equally likely to meet T or t from the •
other parent. Thus half such T's will form the com-
bination of TT, and the other half Tt. Now the t of
the first parent goes out in the same way, and is also
equally likely to meet T or £, and in half the cases forms
tT, in the other half tt. We thus get the four possible
combinations, all equally likely; they are TT, TV, tT,
and tt. This sounds confusing, but the same result may
48 ZOOLOGY
be reached experimentally, without going to the trouble
of raising plants. Take a half-dollar and toss "heads
or tails." On the first toss you are equally likely to get
heads or tails ; so also on the second toss, the first hav-
ing no effect on the second. So half the first tosses of
each pair will be heads (H) and half will be tails (h).
Now, after tossing heads, half the second tosses (on the
average) will be heads and half tails. The same after
tossing tails. Hence, after a large number of successive
pairs of tosses, you get this result, \HH, \Hh, \hH,
\hh. The tosses, like the Mendelian combinations of
determiners, follow the "laws of chance." In a small
number of cases the proportions will not be likely to
agree exactly with the theory, but the larger your
statistics, the closer the agreement.
Explanation 12. Returning now to the visible results, the F%
toeC-to-one generation from our cross between the tall and dwarf
ratio peas gives us J7T, \Tt, \tT, \ti. The first is homozy-
gous or pure-bred for tallness, and will of course be tall.
Crossed with others like itself, it will give only tails -
provided that by "like" we mean not merely in ap-
pearance, but in actual constitution. Tt and tT differ
only in that one got its tall factor from one parent, the
other from the other. As this makes no difference, and
as T is dominant, both will be tall. Finally, tt is
homozygous for dwarfness, the recessive character, and
will therefore be dwarf. It is what we call an "ex-
tracted recessive," and when crossed with others like it-
self can give only dwarfs, in spite of the fact that both
its parents and one of its grandparents were tall. We
now see how the three-to-one ratio is explained theo-
retically; given the facts, it seems very simple, but it
is hard to exaggerate the credit due to Mendel for first
detecting the law governing inheritance.
MENDELISM 49
13. Mendel's work was duly published, in a paper Mendel's
which is a model of clearness and convincing logic. J^J/bttt
Nevertheless, it was completely ignored. The botanist ignored
Nageli, with whom he corresponded, was unable to ap-
preciate the importance of his novel ideas. The Briinn
society sent out its publications to other societies and
to libraries, but no one understandingly read Mendel's
account. Darwin, who of all men was most fitted to
make good use of it, never saw it at all. Mendel was
appointed Pralat, and took upon himself important
executive duties. In 1872 the government imposed
special taxes on the property of religious houses, and
Mendel, claiming that all should be equal in law, re-
sisted this injustice. The latter part of his life was
spent in the bitter struggle for what he considered to
be the- right, and he died a disappointed man, on Janu-
ary 6, 1884. A few years after his death the tax he had
resisted was removed without debate. As to his scien-
tific work, he died wholly unknown, though it is related
that he used to say hopefully, " Meine Zeit wird schon
kommen /" (My time will surely come!)
14. It did come, indeed, but not until 1900, sixteen Rediscovery
years after he had gone. Three naturalists, De Vries, papers and
Correns, and Tschermak, at about the same time, re- *e "f^.of
M en d elism
discovered Mendel's paper and perceived its signifi-
cance. Professor Bateson, at the University of Cam-
bridge, in England, took up "Mendelism" with
extraordinary vigor, and became the leading exponent
of the subject. In many places experiments were be-
gun, to test the theory. It was soon found that
Mendel's principles were applicable not only to plants,
but also to animals, including man himself. Numerous
exceptions and difficulties were encountered, but these
served only to .bring to light new facts which were
50 ZOOLOGY
eventually, in one way or another, accommodated by
the rapidly extending theoretical structure. "Mendel-
ism," as we know it today, would astonish Mendel
himself, but his researches stand at the very root of
the growth which has sprung from the work of modern
experimenters. Most wonderful of all, perhaps, is the
confirmation and extension of the theory made possible
by investigations into the minute structure of the germ
cells, due to instruments and methods wholly out of
Mendel's range, belonging to a science called cytology,
which scarcely existed in his time.
CHAPTER EIGHT
THE RED SUNFLOWER
I. THE red sunflower may be studied in illustration Mendeiian
of the principles of heredity and of plant breeding. Its {
advantages for this purpose arise from the fact that its by *&* red
• • - i • • 111- 11 sunflower
origin is known, and its whole history belongs to recent
times, since the rediscovery of Mendel's law. It is also
very easily grown, and the various crosses may be made
with little difficulty. It is only necessary to cover the
heads with paper bags before they come into flower,
and at intervals dust the stigmas with pollen from
another plant. The great amount of pollen produced
by the flower head, although reaching its own stigmas,
has no effect. The plants are always, with possible
rare exceptions, sterile with their own pollen. When
the summer is over and the seed is ripe, the heads
may be cut off, bags and all, and the seed garnered at
leisure.
2. The sunflowers (Helianthus, which in Greek means Characters
sunflower) are peculiar to the Western Hemisphere.
They are most numerous in the United States east of
the Rocky Mountains, but extend south to the Andean
region of South America. The common garden sun-
flower (Helianthus annuus) is an annual, coming from
seed every year. Others are perennial, growing year
after year from the same clump ; while still others send
out underground branches, from which new plants arise,
the original roots and stems perishing at the end of the
season. All these plants are herbaceous ; that is, the
stems die at the end of summer or fall.
Sunflowers belong to the great group of plants
called Composite. The so-called flower is really a flower
head, consisting of a disklike or more or less elevated
51
52 ZOOLOGY
receptacle, on which are placed the very numerous
flowers or florets. The outer florets bear the large rays,
which give the head its conspicuous appearance. These
are sterile and do not produce seed, but they make the
sunflowers easily visible to the bees, which carry the
pollen and so bring about fertilization. The large
center or disk is composed of great numbers of small
florets, each giving rise to one seed. The florets do not
all bloom simultaneously, and a brief examination will
often show that a head which is apparently in full
flower is really mainly still in bud.
Varieties of 3. The garden or annual sunflower, aside from varia-
sunffower tions in color, has several distinct forms. That with
the tall single stalk and the enormous head at the
summit is commonly known as the "Russian sunflower."
The disk may be a foot across. This variety forms an
important crop in Russia, but it did not originate there,
and the name is as misleading as that of the "Irish
potato," which also is of American origin. The first
description of the large-headed sunflower was published
in 1567, and was made from plants growing at Madrid,
in Spain. Its native country was supposed to be Peru,
but more probably it was Mexico, as no similar sun-
flower is known to exist in Peru. The wonderful sym-
metrical heads, with their bright orange rays, early
attracted the attention of artists. Anton Van Dyck
or Vandyke (1599-1641), when painting his own por-
trait, introduced a sunflower into the picture, — a very
large head, with two or three rows of rays. In the
nineteenth century Edward Burne- Jones, the English
painter, wrote: "Did you ever draw a sunflower? It
is a whole school of drawing and an education in itself.
Do you know what faces they have, — how they peep
and peer, and look arch and winning, or bold and a little
THE RED SUNFLOWER 53
insolent sometimes ? Have you ever noticed their back
hair, how beautifully curled it is ?"
4. In Western North America, in that great prairie The prairie
region which old geography books used to describe as s
the "Great American Desert," the sunflower grows wild.
It is not like the large-headed garden kind, for it has
many branches and much smaller heads. Some bot-
anists call it a distinct species, but it is perfectly fertile
when crossed with the "Russian" variety, and when
examined in detail, presents no material difference in
the structure of its parts. These wild sunflowers were
brought into cultivation by the American Indians in
very early times, from Canada to Mexico. They
yielded an abundance of oil, "which the Indians, more
mindful of their appearance than of their diet, mostly
used for anointing their hair and skin." The seeds
were parched and ground and made into bread. The
state of Kansas, recognizing the sunflower as one of its
most characteristic products, long serviceable to man,
adopted it as its emblem.
5. The coloring matters in the sunflower are ob- Coloring
viously of more than one kind. Aside from the chloro-
phyllj to which the green of the leaves and stems is due,
there is the orange or yellow pigment in the rays. This,
as well as the chlorophyll, can be seen under the micro-
scope to be located in definite particles. A closer in-
spection usually shows some purplish speckling on the
stem, and the prairie sunflower has a dark disk. The
dark color of the disk florets, as well as the speckling
on the stem, is caused by a coloring matter called antho-
cyanin, dissolved in the cell sap. Anthocyanin (from
Greek words meaning flower-blue) is a name for a class
of pigments which may be pink or blue, and when ex-
tracted may often be changed from one color to the
54
ZOOLOGY
Red sun-
flower due
to an ex-
tension of
anthocyanin
already
present
other by chemicals. The acid state is pink, but when
an alkali is introduced the solution may become blue.
The anthocyanin of the sunflower turns green in alkali,
but this is probably due to the presence of a yellow
substance (flavone).
6. The first sunflower with red (maroon) on the rays
seems to have been observed in South Dakota in 1892,
but no record was made of the fact at the time. In
1910, in Boulder, Colorado, a plant was found by the
roadside, having the rays strongly suffused with chest-
nut red. This was an example of the prairie species
or race, and had not come from a cultivated source.
FIG. ii. The red sunflower (Helianthus annuus, variety).
THE RED SUNFLOWER 55
The red color was the same anthocyanin as occurs in the
disk of these sunflowers, only greatly increased in
amount and extending over the rays. The coloring
matter was really pink, but the effect on an orange
background was chestnut. It was an astonishing thing
to see a style of coloration entirely new to Helianthus,
though well known in some allied plants, and due not
to any new substance, but to an increase of one com-
mon in sunflowers. Thus does Nature produce novel-
ties, by taking advantage of what exists. Man, noting
the process, may in certain respects follow her example.
If he cannot produce variations, he can at least often
combine them, and the combinations will be in every
practical sense new forms.
7. The Boulder variety with -reddened rays existed Red sun-
in 1910 as a single plant. Since sunflowers are sterile a^BouWe
with their own pollen, it could be propagated only by Colorado
crossing with orange-rayed forms. Would the red ap-
pear in the offspring, would it be dominant or recessive ?
When the following summer came, and a garden full of
sunflowers burst into bloom, about half showed the red
color. It is probable that this may be explained as
follows : The original plant was of course the result of
the combination of two gametes or germ cells, derived
from its parents. The change in the germ plasm which
gave rise to the red variety probably took place during
the formation of one of these gametes. Thus, al-
though there may have been no "red" parent, the plant
was a cross between a "red" and a "no-red" gamete.
These diverse gametes united to form a zygote, or ferti-
lized cell, from which a plant developed. Red being
dominant, the result was red ; but the plant would
produce two kinds of gametes, "red" and "no-red."
In the new crosses, the other parent was always orange-
56 ZOOLOGY
rayed (no-red); so "red" X "no-red" would give
"red," and "no-red" X "no-red" would give orange
rays. If we use R for "red" and r for "no-red," the
formula is as follows :
Rr X rr = Rr and rr (half of each)
Of course the actual crosses are between the gametes,
and are to be expressed thus :
R X r = Rr
Develop-
ment of a
pure-bred
strain
Production
of wine-red
sunflower.
The 9, 3, 3,
i ratio
8. Having now obtained a number of plants like the
original one, these could be crossed together, and would
give homozygous or pure-bred reds.
Thus Rr X Rr will give RR, Rr, rR, rr, a quarter of
each being the theoretical expectation. The gametes,
being R and r (in equal numbers) on each side, and com-
bining at random, give this result as follows :
R. K
The lines indicate the possible combinations, each one
as likely to happen as any other. The homozygous
reds, if isolated, will now come true, except so far as
they may be influenced by pattern and dilution factors,
and environmental conditions, as explained below.
9. There had been known in cultivation since 1889
a variety of the garden sunflower called "primrose,"
having the rays pale yellow, the color of the English
primrose. This had arisen as a "sport" from the or-
dinary kind, and the same variation has since been ob-
served in the prairie sunflower. Knowing that the red
of the red sunflower was chestnut only because on an
THE RED SUNFLOWER 57
orange background, it was naturally suggested that if
the color could be put on the "primrose" rays, an en-
tirely new effect would be the result. How might this
be done ? Homozygous (pure-bred) red was crossed
with primrose, and to save a year the progeny were
grown in the greenhouse during the winter. They were
very ordinary heterozygous reds. The cross had been
as follows, using 0 for orange and o for primrose (no-
orange), R for red and r for no-red :
RROO X rroo = RrOo (gametes RO X ro give RrOo
zygote)
RROO is the same as RR given above. So long as all
the plants had the orange background, it was not neces-
sary to insert it in the formula.* The RrOo plants are
red on orange, because red is dominant over no-red, and
orange over no-orange (primrose). In former times
breeders had sometimes made first crosses as just de-
scribed, and failing to get the desired result had neg-
lected to continue the work. Thanks to Mendel, it was
possible to see ahead in this case. The apparently or-
dinary reds had one property which no reds had ever
had before, they were heterozygous for orange. It was
only necessary to cross them together. In this cross
the "red" factors and the "orange" ones combined
independently of each other. The reds, as explained
above, gave RR, Rr, rR, and rr, which is three reds to
one plain orange. The orange, on the same principle,
gave 00, Oo, oO, and oo, which is three orange to one
primrose. But as these combinations were independ-
ent, each one was as likely to occur with one as another
of the other group. The theoretical expectation, follow-
ing the so-called law of chance, is that RR, for example,
in each four times will happen to occur once with 00,
ZOOLOGY
Color
patterns in
sunflowers
(9o, oO, and oo. The total result may be expressed by
a diagram, as follows, in which each zygote is repre-
sented within a square. Each combination of red and
orange is repeated four times, combining with the other
four. The red series is repeated vertically, the orange
transversely.
RR
Rr
rR
rr
00
00
00
00
RR
Rr
rR
rr
Oo
Oo
Oo
Oo
RR
Rr
rR
rr
oO
oO
oO
oO
RR
Rr*
rR
rr '.
00
00
00
00
It will be seen that, of the sixteen squares, nine have
at least one R and one 0, and therefore will be red on
orange, or chestnut red. Three have (9, but no R, and
are plain orange, like the wild ancestor. One has
neither R nor (9, and so is primrose. Finally, three
.have R but no (9, and are red on a primrose background.
It is these last we aimed to get, and as was expected,
they present quite a new shade of color. The red is
wine-red or "old rose." Thus a new color variety is
"created," by recombining old factors. In the original
experiment giving this result the plants obtained were
71 chestnut-red, 19 orange, 25 wine-red, and 8 primrose.
The theoretical expectation, following the 9, 3, 3, I
ratio, was 69 chestnut, 23 orange, 23 wine-red, and 8
primrose.
10. So far, we have considered only the shade of
color. It was surprising to find that, given a certain
color, it might appear in various different patterns.
THE RED SUNFLOWER 59
These patterns are the same for the chestnut as for the
wine-red. The rays may be entirely red, or the ends
may be yellow or orange. Sometimes the red is con-
fined to the middle of the ray, and the whole effect is
that of a red ring on an orange ground. These patterns
are inherited independently of the color, so that a flower
may have the pattern factor, yet no development of
anthocyanin to make it manifest. It is a remarkable
fact that photography will reveal the patterns in appar-
ently uniform rays, showing that there is already some-
thing there, not readily appreciated by our eyes. The
patterns of another species of sunflower, Helianthus
cucumerifoliuSj are quite different from those of the
H. annuus.
ii. The combinations of color and pattern give quite Various
a variety of forms, but there are in addition many varia- varieties'
tions in structure. Some of these are horticulturally
worthless, though scientifically interesting --such as
the variety tortuosus, with the ends of the rays twisted
as though in curl papers. There are so-called doubles,
in which all the florets are ligulate or rayed. The rays
may be 'in two or three rows, an approach to the type
of the star dahlias. Some forms have the rays cleft at
the end. Perhaps the most interesting recent develop-
ment is the collarette, in which the rays have a narrow,
more or less curled lobe attached near the base, after
the manner of the well-known collarette dahlia. These
modifications affect the flowers, but they may be com-
bined with various growth forms, and hybrids are pos-
sible between different species — even between annuals
and perennials. It will thus be evident that the possi-
bilities are so numerous that we can have no idea at
present of their limits. What the dahlia has done, in
its horticultural history of about a century, the sun-
60 ZOOLOGY
flower may in some measure parallel. There is, how-
ever, this important difference : the dahlia can be
propagated vegetatively, by tubers, and hence it is
possible to preserve and increase the various heterozy-
gous forms. The sunflower, propagated by seed, will
not remain constant unless homozygous ; and then,
under ordinary circumstances, it must be hand-polli-
nated. Consequently, it will be practically impossible
to maintain a large number of pure strains representing
the variations of the sunflower. Some of the best semi-
doubles appear to be necessarily heterozygous, and con-
sequently incapable of producing seed that will regularly
come true.
Variation in 12. Finally, it must be added that even when the color
expression anj markmg factors are those desired, there may be
great variations in "expression." These may in some
cases be caused by the presence of what are called
"dilution factors," having the property of causing the
color to be relatively faint, or diluted. Such factors
have been demonstrated even in animals. They may
be due also to purely environmental causes, having
nothing to do with heredity. For example, it appears
that the red tends to fade out in very hot weather,
and it has been claimed that its appearance is greatly
affected by the soil.
Plant breed- 13. Plant breeding, in the light of our present knowl-
occupation ec^ge? 'ls a fascinating subject, and may be carried on
very well in a small garden. It is especially suitable
for amateurs, who do not expect to earn their living in
this manner. They can experiment as they will, with-
out being obliged to consider financial, results. The
best way is to select some species or genus of plants,
and study it intensively, becoming acquainted with all
its known variations and special peculiarities of struc-
THE RED SUNFLOWER 6 1
ture and habit. It is desirable to consider the character
of the plant from the standpoint of a breeder; thus it
should be one which will do well in the locality, which
will not take too long to come to maturity, which can
be crossed without undue difficulty. Some of the more
difficult and lengthy problems are equally worth while,
but they must be solved by institutions, which are not
limited to the short span of a human life.
CHAPTER NINE
THE CHROMOSOMES
Cytoplasm I. THE cytoplasm or substance of the cell incloses a
and nucleus reiativejy small body known as the nucleus. In some
cases there is more than one nucleus, and in certain
special kinds of cells, as the red corpuscles of the blood,
the bacteria, and very few Protozoa, no nucleus appears.
When the nucleus is absent, it is possible, at least in
some cases, that the nuclear matter (nucleoplasm) is
diffused through the cell. Ordinarily the nucleus is a
small, rounded body near the center of the cell, which
is much more deeply colored with certain stains than
the cytoplasm, so that microscopic preparations of ani-
mal tissues often appear to be minutely speckled. The
spermatozoon, or sperm cell, the contribution of the
male to the process of fertilization, carries very little
cytoplasm. Being motile, having to seek the egg cell,
it cannot afford to be burdened with anything not
necessary for its peculiar function. The nuclear matter
is present, and can be shown to consist of materials
similar to those in the relatively gigantic egg cell.
Chromatin 2- From 'its universal presence in ordinary cells, and
andchromo- the fact t]iat a piece of cytoplasm cut from a cell, if
somes . . J
containing no nucleus, dies, we assume that the nucleus
is of special importance for life. On examining more
closely, we find a kind of material in the nucleus which
stains most readily, known as chromatin. This chro-
matin, when cells are dividing, is seen to collect in small
bodies, usually • more or less rod-like or thread-like,
known as chromosomes. The words "chromatin" and
"chromosome" imply the presence of color, and are
misleading, since the material is colored only when
artificially stained.
62
THE CHROMOSOMES 63
3. On examining these chromosomes, we note the Thechromo-
fact that for any particular kind of animal or plant JJSSein
number
FIG. 12.
Drawing by C. E. Allen
Chromosomes in cell of lily (LUium canadense), greatly magnified.
there is a definite number in each cell. The two excep-
tions to this general statement do not invalidate the
rule, but when explained are seen to be quite in harmony
with it. One is, that the number may be slightly dif-
ferent in the two sexes ; the other, that the gametes, or
cells uniting in the process of fertilization, contain only
half the number characteristic of the species.1 The
number of chromosomes in different organisms differs
greatly ; thus the cells of a certain parasitic worm have
1 Other exceptions recently noted do not invalidate the general principle.
Miss Caroline M. Holt has found that the cells in the intestine of the pupa
of the mosquito may contain many more chromosomes than are normal for
the species, but the numbers are always multiples of three. The chromo-
somes have increased by division without the usual accompaniment of cell
division. Such cells degenerate or disintegrate, and are absorbed as nutri-
ment by the cells of the developing adult. (Journal of Morphology, Septem-
ber, 1917.)
64
ZOOLOGY
Mutations
with altered
numbers of
chromo-
somes
Maturation
of germ
cells ; the
reduction
division
only two, while other animals and plants have very
many. So regularly is any difference in the number of
chromosomes associated with a difference of species,
that naturalists have come to regard it as a specific char-
acter. Thus Professor E. B. Wilson was examining the
chromosomes of certain bugs (Hemiptera) which a
specialist in entomology had declared to be all of one
species. He discovered that he had two lots, from dif-
ferent parts of the country, differing in the number of
chromosomes. He then returned some of them to the
specialist, who was able to find valid external characters
in the insects, and was obliged to confess that he had
been mistaken ; that there really were two species.
There are cases, however, in whicfi differences in the
chromosome number have arisen under observation, and
do not separate what we should ordinarily call species.
Lamarck's evening primrose has 14 chromosomes ; but
from it has arisen a large form, called by De Vries
(Enothera gigas, which has 28 chromosomes. Another,
called semigigas, has 21. These plants, which De
Vries calls mutations, have very distinct external char-
acteristics accompanying the difference in chromosomes.
If we found them on different islands or in different
countries, knowing nothing of their history, we should
doubtless call them "good species," and should point
to the chromosome count in confirmation of our opinion.
4. The behavior of the chromosomes in the germ
cells or fertilizing cells is remarkable, and confirms the
view that they are of particular significance for heredity.
The germ-cell material is in most cases set aside early
in development, and is compelled to wait until sexual
maturity for its opportunity. It does not become
specialized, in the manner of muscle cells or nerve cells,
as by so doing it would lose the power of contributing
THE CHROMOSOMES 65
to the development of a new individual. It merely in-
creases in quantity by the absorption and assimilation
i &^n
Drawing by A. B. Stout
FIG. 13. Cells of sedge (Carex aquatilis), greatly magnified. Stages of cell division
(mitosis), an equal amount of ckromatin going into each of th'e two cells.
of food, while the number of cells is increased by divi-
sion. When the proper time comes, the germ cells go
through a peculiar process known as maturation,
whereby they are made ready for fertilization, and the
consequent origin of new individuals. In ordinary cell
division (called mitosis) the chromosomes divide, so that
each resulting cell gets half, and has the same number
of chromosomes as the mother cell. In the maturation
divisions something different occurs. The sperm cells
are formed by a division in which half the chromosomes
go into one cell, half into another. There is no division
of the individual chromosomes, such as occurs in mitosis.
When there is an odd chromosome, one of each pair of
sperm cells has it, the other is without it. The matur-
ing egg cell, on the other hand, finally throws off a
minute particle known as a polar body. This is formed
by a division of the nucleus, in which half the chromo-
somes remain, while the other half pass into the polar
body. • Thus the egg cell, too, comes to have only half
66 ZOOLOGY
the specific number of chromosomes at fertilization.
The polar bodies perish, and consequently some of the
material of inheritance is wasted, but the surviving
group of chromosomes carries all the cytoplasm neces-
sary for the beginnings of development after fertiliza-
tion. Were this cytoplasm divided equally, in a process
similar to that which makes two sperm cells, there would
probably not be enough for either, and both, though
fertilized, would perish.
The spermatocyte, or sperm-forming cell, divides to
form two, and these divide again to form two spermato-
zoa each. The oocyte, or egg-forming cell, does not
thus divide; but its nucleus divides, so that there re-
sults one large cell and a polar body. The large cell
undergoes another nuclear division, as described above,
when the second polar body is formed and the number
of chromosomes is reduced to half. The first polar
body also divides, but comes to nothing. Thus, where
four spermatozoa are formed, the corresponding cells of
the female are one functional egg cell and three minute
cells which perish. As a matter of fact the spermatozoa
produced by the male are vastly more than four to one
egg cell of the female, following the law that the number
produced must vary with the chances of survival. The
male produces myriads of spermatocytes, and hence
vast numbers of spermatozoa.
When fertilization takes place, each gamete (matured
germ cell) brings to the union its half set of chromo-
somes, and thus the regular number is made up again.
Were it not for this, the number would be altered at
each fertilization ; thus, without the reduction division,
each gamete would carry the full number typical of the
species, and uniting, the two would double the number.
After several generations there would be an enormous
THE CHROMOSOMES
67
number of chromosomes in every cell. The resulting
mechanism would no longer be able to develop normally,
if at all.
The whole process may be represented by the fol-
lowing diagram, in which A, A' , and again B, B' ', are
homologous chromosomes, derived from different par-
ents and representing similar structures, but not pre-
cisely alike. At the reduction division, because one of
each pair goes out, we get gametes of four sorts, AB,
A'B, AB', A'B'. If these are sperms, uniting with a
similar series of eggs, we may have :
Sperm
Egg
Zygote
AB
A'B'
=
AA'BB'
A'B
AB'
=
A'ABB'
AB'
A'B
=
AA'BB'
A'B'
AB
=
A'AB'B
A'B' —
A'B'
=
A'A'B'B'
The first four zygotes are all alike, and are heterozygous
(cross-bred) for both sets of factors carried by the
chromosomes ; the fifth is unlike the others, being
homozygous (pure-bred) for both sets of factors ; but if
dominance is complete, it will appear like them.
Sperm cells (gametes) from male
.jerms fail
B'
' A A' \''^^ ~~" aT1C* s°Pensh
B BjSpermatogenes,* E^cell
m fern ale
f A' B '
5permatocyte divisjon%^^
the chromosomes are
separated into two sets,
but do not divide
A - A' Ylvfo pairs of
f homologous
B - B'J chromosomes
FIG. 14.
Polar bodies
(Which perish)
Germ plasm
Oiicyte division: half
the chromosomes will
Zyiotes divide to fbrtn an individ-
TiaJ: the chromosomes also divide
(mitosis). Some of the cells thus formed
are set aside as<germ celk^emi plasm).
Drawing by W. H. Schanck
68 ZOOLOGY
Reduction 5. In the higher plants there is a peculiar complica-
and fertili- • i i • n i i
zationinthe tlon whereby certain cells come to have more chromo-
flowerin somes tnan tne number normal for the species. The
plants pollen tube, which has developed from the pollen grain,
brings to the ovary two sperm cells, one of which unites
with an egg nucleus which has the reduced number of
chromosomes. The duplex number is thus made up,
and so far the process is essentially like that observed
among animals. In the maturation of the egg nuclei,
division takes place as in animals, and part of the
chromosomes are rejected. Two of the particles come
together and produce a nucleus in which, apparently,
the full number of chromosomes is restored. This is
then fertilized by the second sperm nucleus, and the
resulting zygote has one and a half times the duplex
number of chromosomes. Thus if 4 is the simplex num-
. ber and 8 is the duplex, then it will have 12. The zygote
so formed does not produce an embryo, but instead pro-
duces a quantity of undifferentiated cells, constituting
the endosperm. This endosperm serves as nourishment
for the embryo proper, or the plant into which it de-
velops. That there is a real process of fertilization in
the formation of the endosperm is proved by the phe-
nomenon called xenia, whereby the seeds show the in-
fluence of the pollen parent. This is especially notice-
able in corn (maize), where red grains appear on white
ears, when they have been fertilized by pollen from
plants carrying the factor for red.
The above account is based on recent observations on
particular plants ; it is probable that it is essentially
true for all the higher flowering plants (angiosperms),
but there are doubtless differences in detail.
6. The chromosomes are not all alike. They may
differ visibly in size or shape, but there are many
THE CHROMOSOMES
69
reasons for believing that their differences are much
more profound than mere inspection would suggest.
At fertilization a set from each parent goes to the forma-
tion of the zygote, and (excepting the odd chromosome,
to be considered later in connection with sex) the two
sets correspond in the sense that each type of chromo-
some has its mate. Thus the cells of the individual are
duplex or double, containing a contribution from each
parent. Shortly before the reduction division, the cor-
responding chromosomes, derived from the parents of
the reproducing individual, are seen to become coupled,
the pairs uniting side by side or twisting more or less
around one another. This phenomenon is called synap-
sis. There is reason for thinking that when they sepa-
rate, they do not always retain their original integrity,
that there may be some interchange of materials. This
matter has been investigated by Dr. T. H. Morgan and
his associates at Columbia University, with very re-
markable results. In the study of inheritance in flies
of the genus Drosophila, it was found that certain char-
acters were not inherited in accordance with the theory
of random sampling, but came out in groups. At first
One set of
chromo-
somes from
each parent
Synapsis
Linkage,
and its
results
FIG. 15.
Ba^**a!5a=r. Drawing by C. E. Allen
Cells of lily (Lilium canader.se). i, synapsis; 2, resting stage. Greatly
magnified.
70 ZOOLOGY
it might well seem that this could be explained on the
supposition that each group of characters was due to a
r\
Drawing by R. W-eber (after Morgan)
FIG. 1 6. Linkage and crossing-over. A, B, determiners in the same chromosome,
are linked. But at synapsis (2) the chromosomes divide, and the upper half of
each becomes attached to the lower half of the other (3). Then A and b will go
together, no longer A and B. The division may occur at any point, or at more
than one point, but the nearer the determiners are together, the less likely are they
to be separated.
single inherited factor, which gave rise to various re-
sults. This, however, was negatived by the fact that
the characters were not necessarily associated, but only
generally so. It gradually became evident that the
phenomenon, known as linkage, had to do, not with the
identity of the factors, but with their occurrence in the
same chromosome. This was confirmed by the dis-
covery that the number of such groups in Drosophila
corresponded with the number of chromosomes. Should
this theory be true, how might we account for the fact
that linkage is not absolute, that there are exceptions ?
Indeed, not only are there exceptions, but they evidently
follow some rule, certain of them being much more fre-
quent than others. The idea was suggested that per-
THE CHROMOSOMES Jl
haps failures of linkage might be due to the fact that in
synapsis there was an exchange of material between the
homologous chromosomes, that synapsis was in fact a
sort of "shuffle and cut" process. Should this be true,
it might be expected that if the factors or determiners
occupied definite places in the chromosome, those near-
est together would be least likely to be separated. This
hypothesis was tested by the most elaborate breeding
experiments, and eventually the relative positions in the
chromosomes of many factors were determined. The
results not only agreed with the hypothesis, but served
to confirm it. Thus if the relative positions of A and
B were calculated, and then those of B and C, it followed
that A and C ought to behave in a certain way when
brought together in a cross, and predictions of this sort
were fulfilled in numerous instances. It was found that
some factors crossed over less than once in a hundred
times ; others as often as once in every other time. In
the latter cases the factors lie far apart, probably near
the opposite ends of the chromosome. Very recently LOSS of part
Mr. C. B. Bridges has been able to show that in a par-
ticular case, instead of an exchange of substance, a
piece out of a chromosome was lost. In an experiment
with Drosophila flies, a particular character which
should have appeared, according to the known char-
acters of the ancestors, failed to develop. It occurred
to Bridges that if it, or rather the determiner for it, had
really got lost, very possibly other determiners, known
to lie very close to it in the chromosome, had also gone.
He tested this by further breeding, and found it to be
the case. Thus he at once confirmed his idea concern-
ing the loss of a fragment, and furnished additional
proof of the theory concerning the position of the de-
terminers in the chromosome,
72 ZOOLOGY
Synapsis What is the purpose of the synaptic shuffle and its
viability resulting phenomenon, the crossing over of factors
otherwise linked ? Evidently, in heterozygous or cross-
bred races, it increases variability, and provides for the
almost endless variety of living types, furnishing the
material for natural selection. Through such means
Nature furnishes, as it were, innumerable keys to un-
lock the doors of opportunity. Many, indeed most,
must fail ; but many succeed, and these fill the world
with variously adapted forms of life.
CHAPTER TEN
FERTILIZATION
1. REPRODUCTION comes about through division. In Reproduc-
the simplest forms of life trie cell is the individual, and it division*
divides into two equal parts, each of which feeds and
grows to the size of the original cell. In the many-
celled animals and plants, — that is, all the higher
forms, — cell division does not usually give rise to new
individuals. As in the first case, new cells are pro-
duced, but they are retained as part of the body of the
creature. Sometimes, however, a mass of these cells
is set apart, forming a bud or similar structure, which
may break away and become a separate individual.
Thus the Hydra, a small ccelenterate animal found in
ponds, produces buds which develop into what seem to
be little hydras parasitic on the mother. These pres-
ently break away, and become new individuals. Many
plants reproduce by runners or tubers ; in some kinds
of sunflowers the original plant dies, while its under-
ground branches produce new plants the following year.
In Arizona certain branching cacti rarely produce seed,
but their branches break off and take root where they
fall, thus producing new plants.
2. In all the cases just cited there is no fertilization, Conjugation
MI the biological sense. It is found, however, that even Jorms of
among the one-celled animals (Protozoa) conjugation fre- Ufe
quently takes place, though apparently not essential.
This conjugation consists in the union of two individ-
uals ; in Paramecium these come together, exchange
portions of their protoplasm, and then separate. Each
may be said to have fertilized the other, by giving it a
portion of its substance ; neither has lost in bulk, since
the exchange is equal. In other cases, as for instance
73
74
ZOOLOGY
Fertilization
by union of
a sperm cell
with an egg
cell
Partheno-
genesis, or
reproduc-
tion from
unfertilized
egg cells
certain seaweeds, multitudes of minute cells are thrown
out, all exactly alike. These join in couples and com-
pletely fuse, after which they develop into new plants.
This union is also fertilization, and unlike the Para-
mecium, the cells participating will not develop or con-
tinue their race without it.
3. In the higher forms of life, the cells which take
part in fertilization are not alike. The sperm cell pro-
duced by the male is very different in appearance from
the egg cell produced by the female, although each con-
tains the essential contribution of chromosomes. Fer-
tilization is no longer optional, as it were ; it is obliga-
tory. In the highest plants, indeed, certain vegetative
methods of reproduction are still possible ; and when
impossible under natural conditions, they may still take
place through man's influence, by cuttings or grafts.
Nevertheless, the seeds will not develop without some
stimulus, something of the nature of fertilization. In
the higher animals reproduction by the union of sperm
and egg cells is the invariable method, and we think of
fertilization as necessary for the continuance of life.
4. We think of the process of fertilization as consist-
ing essentially of the union of the protoplasm of two
cells derived from different individuals. These cells,
called gametes, have the simplex or reduced number of
chromosomes ; they make up the full number when
united to form -the zygote. This seems clear enough,
but we are puzzled when we find that in many animals,
even such highly organized ones as insects, partheno-
genesis takes place ; that is, reproduction from unferti-
lized egg cells. This is not like the simple division of
the protozoan, or the vegetative propagation of the
plant ; here we have an egg cell, apparently made for
fertilization, and it develops without it ! It is, as it
FERTILIZATION 75
were, self-fertilized. Many egg cells which thus de-
velop without fertilization do not lose half their chromo-
somes, and thus the cells of the resulting individual
carry the full number, notwithstanding the lack of any
contribution from a sperm.
5. Still more surprising, however, is the fact that Artificial
Dr. Jacques Loeb has been able in a number of cases to
bring about artificial parthenogenesis. This means that caused by
, , . . , , . r -i- i chemical or
he has succeeded in causing development in unfertilized physical
eggs through the action of various chemicals, or even by stimuli
mechanical or physical stimuli. In all such cases, of
course, there is no possibility of the union of protoplasm
from different individuals. It begins to appear, then,
that if we mean by fertilization that which induces
growth, the protoplasmic union has little to do with it.
6. Dr. Loeb also found that development may often Deveiop-
be made to occur by introducing the sperm of some by6^*1186
quite different animal : for example, sperm of a sea sPerm of
111 r r i T-<I • unrelated
urchin added to eggs of a starfish. The resulting or- animals
ganisms would develop properly, but would show only
maternal characters. That is, they would possess none
of the characters of the male parent, the sperm of which
had "fertilized" them. Evidently, then, even here
there had been no intimate protoplasmic union.
7. The final conclusion is, that the egg cell contains cross-
within itself all the essential factors for development. ^^n^nof
Since, however, bisexual reproduction has come to be cells with.
the normal method among the higher animals and powers
plants, typical egg cells develop qualities which cause
them to remain latent until a sperm arrives. It is like
the sleeping beauty in the old story, waiting to be
awakened by the right prince. In parthenogenesis she
awakes of her own accord, or in response to some un-
toward disturbance. In a sense, there is less of magic
76 ZOOLOGY
in this than in the more common event. As so often
happens when we study life, we find that it is the com-
monplace, the everyday thing, which is most marvelous.
So careful is Nature, in the majority of cases, to bring
about cross-fertilization, to unite diverse individuals in
the stream of inheritance, that innumerable adaptations
have arisen to that end. Thus many flowers, although
producing both ovules and pollen, do not ripen both at
the same time, or have special structures to bring about
cross-fertilization through the agency of insects. In the
common garden sunflower, although the pollen of any
head falls all over the adjacent stigmas, it is quite inert,
and no seeds are produced unless pollen is brought from
another plant.
Fertilization 8. From Dr. Loeb's experiments with the sperm of
process6 unrelated animals we gather this, that what we ordi-
narily call fertilization is a double process. It is, first
of all, the initiation or liberation of the activities of the
egg cell, and secondly the union of the nuclei with their
chromosomes. The latter has to do with heredity, the
former not at all. The wrong kind of sperm may serve
as a fertilizer in the sense of starting development, be-
cause the chemical substances it carries are adequate
for that purpose ; but its chromosomes are too different
from those of the egg cell to unite with them to make
an organism. Many different machines may be run by
the same power, but the parts of those machines cannot
be mixed up and transposed without stopping all pro-
duction.
CHAPTER ELEVEN
SEX
i. NEARLY all familiar animals are bisexual; that is The two
to say, they have two sexes, male and female. The sexes
sexes may be so similar in appearance that they cannot
be distinguished without close examination ; or they
may be so different that it is hard to find any characters
in common. Among the. lowest animals we cannot dis-
tinguish sexes ; all the individuals are substantially
alike, and if they conjugate, it may be impossible to
regard one or the other as male or female. Sometimes
there is a difference in size, and then the smaller cell is
thought of as male, the larger as female ; but this is
only a rather loose analogy. Among the higher plants Sex of
we have no trouble in recognizing sex, though the sex phu
phenomena are in many respects quite unlike those of
animals. An ordinary flower, such as a buttercup or a
rose, has stamens and pistils. At the top of each stamen
is an anther, and when this bursts at maturity, the yel-
low powdery pollen is set free. This pollen consists of
grains, which are not gametes or germ cells, but which
produce such. At the bases of the pistils are the ovules,
and these again are not germ cells, but are the producers
of them. The pollen, falling on the pistil, grows a pollen
tube, which conveys the gametes to the ovule, to meet
the gametes there developed, and fertilization takes
place. Such flowers are neither male nor female, but
they produce structures which take on true sexual
functions.
In many cases the stamens and pistils do not occur
together in the same flower. They may be borne by
different plants, which, as in the case of the willow,
present a quite different appearance when in flower.
77
ZOOLOGY
Primary
sexual
characters
Secondary
sexual
characters
On the other hand, there are groups of animals, such as
the common snail, in which both male and female
organs exist in the same individual. Snails are there-
fore said to be hermaphrodites (from Hermes and Aphro-
dite), but they are not self-fertile ; they pair as do other
sexual animals.
2. Sexual characters are those which distinguish sex.
On analysis, we find that they are of two different sorts.
The primary sexual characters, are those which have to
do with the sexual function itself, which is essentially
the production of gametes. It is on account of this con-
ception of sex that botanists object to speaking of male
and female plants or flowers ; they point out that these
organisms give rise to the gametophytes or true sexes,
which produce the gametes. If we object to this on the
ground that the so-called gametophyte generation is so
insignificant, they point out that in the higher flowerless
plants it is conspicuous, being known as the prothallium.
Ferns produce spores, which give rise to these prothallia,
and these in turn produce the gametes.
Secondary sexual characters are those which accom-
pany sex, and are nearly always of some importance in
relation to it. Such, for instance, are the bright plumes
of certain male birds, or peculiarities of the voice. Al-
though these two groups of characters appear so distinct,
they do in fact grade into one another, unless we restrict
the first entirely to the gamete-producing function.
Structures existing for the preservation and nutrition of
the zygote or fertilized cell can hardly be excluded from
the group of primary sexual characters, since without
them, in the animals in which they occur, reproduction
would be impossible. From these there is actually
every gradation, to characters which appear to have no
functional relation to sex. Nevertheless, in a broad
SEX
79
sense, the distinction made is a valid and convenient
one.
3. Many naturalists have discussed the question, Why do
why should the two sexes exist ? The answer is not sexes exist?
simple, yet from the fact that sexuality is such a wide-
spread phenomenon, we cannot doubt that it has a
meaning in relation to the preservation of life. At first
it appears that reproduction depends upon sexuality,
3 4
Drawings by R. Weber
FIG. 17. The rose scale (Aulacaspis rosa), an extreme case of sexual dimorphism,
i, Adult male, with 2 wings, 2 antennae, 6 legs, but no mouth. 2, Adult female;
legs, antennae, and wings not developed, but mouth (on under side) well devel-
oped. This female never leaves the scale (3). The scale shows the cast skin of the
larva at A , the second cast skin at B, and the white adult scale covering the female.
4 shows the scales on a rose branch, twice natural size.
8o
ZOOLOGY
Diversity
resulting
from conju-
gation
but a little study of the more primitive organisms con-
vinces us that this is not the case. That it does so in
the higher animals must be only because there are cer-
tain advantages, for such animals, in this mode of re-
production. Our second thought may well be that it
is not primarily a matter of reproduction at all but of
diversity of vital functions. The male and female have
different duties, and between them, like Jack Spratt and
his wife in the nursery rhyme, they cover the field of
opportunity. We observe that among the social insects
such as the ants, there appear to be three sexes : males,
females, and workers. The workers are not really
another sex; they are sterile females, lacking sex, but
they represent a further diversity of function. There
is no doubt, of course, that diversities in the abilities
and behavior of the sexes are useful in many cases. Out
of the fact of sex has grown a multitude of consequences,
which in man especially are of the greatest significance.
Yet it is impossible to explain the origin and rise of sex
on the basis of results which were millions of years
ahead. Of what value is sex in its simplest form, when
it is narrowed down to the primary function of produc-
ing germ cells which are capable of uniting to form a
new individual ?
4. Professor H. S. Jennings found that even in such
non-sexual animals as the Paramecium, conjugation
increased variability. This is easily understood if we
suppose that the germinal constitution of different in-
dividuals is not exactly alike. If one is ABC, the other
abc, then after conjugation we may get Abe, or aEC, or
abC, etc. Granting that increased variability is bene-
ficial, in so far as it produces new combinations which
may prosper under particular conditions, we can see
how conjugation was justified. Its function, from the
SEX 8 1
first, must have resembled that of trade. It was not
necessary, but often advantageous. This, however, is
not sex. Sex implies the production of gametes which
have the reduced number of chromosomes. These
gametes are diverse, the one produced by the male in
animals small and motile, that produced by the female
relatively large and incapable of propelling itself. Still,
the outcome of the fertilizing process and all that goes
with it is a shuffling of determiners, with a correspond-
ing diversity in the members of the resulting genera-
tion. It is because of sex that scarcely any two human sex and
beings are alike, that life takes on such extraordinary J
diversity everywhere. This diversity has permitted
adaptation to almost every kind of environment; has
furnished, as it were, keys to open every door of oppor-
tunity. If we think of this as the principal meaning of
sex in the scheme of evolution, we may regard the sexual
differences as merely means to an end. The egg cell
carries the cytoplasm with which to support the first
stages of development ; it cannot seek the sperm, nor
could two egg cells, thus provided, seek one another.
So the sperm, free from baggage, which the Romans
truthfully called "impedimenta," can travel in search
of its mate ; but two sperms would not have between
them enough nutrient substance to support the early
cell divisions. The differences now appear to have a
meaning, and it is interesting to note that those char-
acteristics which distinguish the gametes, also more or
less distinguish the sexes themselves in their relation to
one another.
5. We may have our opinion concerning the utility Mechanism
of sex, but it is quite another matter to decide why termination
individuals are male or female. Many opinions have
been expressed, but it is only rather recently (1902)
82 ZOOLOGY
that much real light has been thrown on the subject.
When it came to be realized that the chromosomes were
Drawing by R. n ejer
FIG. 18. Diagram to show spermatogenesis, the small "sex-chromosome" going to
one sperm of every two.
of prime importance in the study of heredity, these
bodies were scrutinized with great care, in a considerable
number of animals. It was found that the sperm cells
of certain insects were not all alike, but were of two
kinds, differing in the number of chromosomes. There
was a peculiar chromosome, often standing a little apart,
which existed in one of the kinds of sperrn, not in the
other. It was evident that in the reduction division
this chromosome had no mate, and hence only one of
every two sperms could receive it. Consequently just
half the sperms possessed one more chromosome than
did the other half. Further investigations showed that
the peculiar chromosome, now called x, did often have a
mate, usually smaller, which was named the y-chromo-
some. In such cases every other sperm contained an
x, the rest a y. There were other modifications of the
scheme, but the general outcome was as follows : Each
of the egg cells contains an ^-chromosome ; when a
sperm containing an x unites with it, then the zygote
contains 2x and produces a female. When the sperm
lacks an x, then the zygote comes to have x or xy, and
produces a male. Although this was made out first in
SEX 83
insects, it is equally true of many other animals, appar-
ently including man. Recent work has revealed a num-
ber of cases to which the above description is not ap-
plicable, but the principle remains the same ; namely,
that sex is determined at the moment of fertilization,
by the number of ^-chromosomes, or sex-chromosomes,
which go into the zygote.
The y, when present, seemed to have no function at
all ; but C. B. Bridges has lately published an account,
of certain cases in Drosophila which appear to show
otherwise. Owing to certain abnormalities in chromo-
some distribution, it was possible to produce males
without the y which is normally present in that insect.
They were quite ordinary in appearance, but absolutely
sterile. Taking advantage of these same abnormalities,
it was found that zygotes with y or yy, but no x, and
also those with 3*, were unable to live.
It thus appears, on the face of this evidence, that sex
is determined by the amount of a ^particular kind of
chromatin, which exists in a special chromosome. One
portion produces a male, two portions a female, while
three are incapable of development. Is a female, then,
all that a male is, and something more ? Hardly so, for
femaleness inhibits the development of male character-
istics. Gametically, the female may be a product of the
male determiner plus another, but in development the
characters of the one are obviously not added to the
characters of the other.
The arrangement provides that exactly half the off-
spring shall be male, and half female, on the average.
The chances of an egg cell being fertilized by one or the
other sort of sperm are even. Why, then, are the sexes
not equal in number in all animals ? There are various
other factors entering into this matter ; the chances of
84
ZOOLOGY
Sex-linked
and sex-
limited
characters
living may differ, even when the zygotes formed are
half of each sex. Cases are known among insects, in
which the sperms of the male-producing type degener-
ate, so that only females are produced. Unfertilized
eggs, developing parthenogenically, give rise to males.
The quantitative difference between the sexes is thus
maintained. Should it happen, in any case, that only
part of the sperms degenerate or fail to function, the
sex ratio will be disturbed.
6. Certain characters are said to be sex-linked.
These are not the secondary sexual characters (sex-
limited), and have no necessary connection with any of
the sexual activities. Sex-linked characters are those
for which the determiners are carried by the sex chro-
mosome (^-chromosome). How can such a fact be
ascertained, since, although the chromosome may be
seen, no one can distinguish determiners in it ? In the
Drosophila flies, the normal color of the eyes is bright
red. A variation with white eyes appeared, and Pro-
fessor Morgan proved experimentally that it was sex-
linked, in the following manner : A white-eyed female,
mated with a red-eyed male, gave only red-eyed females
and white-eyed males. These, crossed together, gave
both red- and white-eyed of each sex. The theory is
as follows : Red-eye and white-eye are allelomorphic,
— that is, paired opposites in inheritance. Red is
dominant over white. If these determiners are in the
^-chromosome, then the white-eyed female has two
"white" x's. The red-eyed male has one "red" x.
Half the sperms of the male carry the "red" x, and pro-
duce females carrying one "red" and one "white" x.
Red being dominant, such heterozygous females are
red-eyed. The other half of the sperms carry no x, and
unite with gametes from the females carrying one
SEX
white
x.
Such are males and are necessarily white-
eyed. In the next generation the sperms from the
male carry no red, but of the egg cells from the heterozy-
gous female half carry red, the other half not. Each
half is equally likely to be fertilized by a male- or
female-producing sperm ; hence there are both red- and
white-eyed males and females. Similar facts were de-
veloped in numerous other cases, proving that the sex
chromosome carries other determiners than that for
sex, and at the same time confirming the sex chromo-
some theory.
7. Although sex is said to be determined by the germ Gynandro-
plasm of the zygote, and therefore decided at the mo-
ment of fertilization, there are various apparent excep- acters of
,. . . A . . v . , i both sexes
tions and complications. Among insects individuals
occasionally appear which combine the characters of
the two sexes in a remarkable way ; these are called
gynandromorphs. A certain kind of parasitic wasp not
only has the sexes differently colored, but whereas the
males are winged, the females are wingless. A speci-
men was found in which the right side showed the male
characters, with wings, and the left those of the female,
Drawing by R. Weber
FIG. 19. Face of gynandromorphic bee (Melissodes), the clypeus showing the color
of the male (light) on one side, of the female (dark) on the other.
86
ZOOLOGY
Determina-
tion of
sexual
characters
through
secretions
apterous. In a kind of bee (Metis sodts) the females
have the face black, but in the males a large part of the
face (the clypeus) is yellow. A specimen was collected
in Texas, which had the clypeus half yellow and half
black, the division between the colors perfectly sharp
and definite. In other cases the sexual characters are
variously combined, forming a sort of mosaic.
Various explanations have been given for these
strange phenomena, but as Morgan has recently (1914)
shown, it is almost certain that they are due to accidents
in cell division at an early stage of growth. If at some
early division, after fertilization, the sex chromosome
fails to enter a particular cell, the tissue developing from
that cell will appear as if the chromosomes in question
had been absent from the start. Thus the determina-
tion of sex at fertilization is only determination in this
sense, that it provides the machinery for the develop-
ment of sex. If that machinery goes wrong, the ex-
pected results do not follow.
8. Among the vertebrates, especially, secondary sex-
ual characters are determined by certain secretions
which act upon the various parts of the body. In such
animals the gynandromorphic phenomena could not
occur. The development of the characters does not
depend on the •chromosomes in the tissue cells, but on
the special activities of certain localized cells connected
with the sexual organs. Consequently, as is well
known, the removal of the sexual organs or their in-
jury by disease results in profound changes, affecting
different structures. It is not especially surprising that
when the sexual organs of certain male animals are re-
moved, special male characters, such as horns, fail to
develop. We are more astonished, however, to find
that in various birds the removal or degeneration of the
SEX 87
female organs leads to the appearance of male plumage.
The female, in such cases, carries the determiner for
male plumage, but its influence is prevented by an
inhibitor which goes with femaleness. Professor Mor-
gan has very recently made a remarkable experiment
which shows that this inhibitor is not a necessary conse-
quence of femaleness, but is associated with it. In the
breed of fowls known as the Seabright bantam, the
male bird is colored and has the feathers formed nearly
as in the female, instead of showing the typical plumage
of a cock. It occurred to Morgan that perhaps the in-
hibitor of typical male plumage had been developed in
the sexual organs of the male as well as those of the
female. He accordingly removed those organs from a
male, which then developed feathers like those of cock
birds of ordinary breeds !
9. The secretions or hormones which control the mani- Sexual
festation of sexual characters may so far influence sex Of ^ms in
as to produce sterility. It has been known from an- cfttle and
cient times, that when cattle produce twins of opposite
sexes, the female is usually barren. Dr. Frank R.
Lillie of Chicago recently investigated this matter, and
found that the facts were as follows : The twins, repre-
senting different zygotes, have at first their separate
envelopes or chorions. As development proceeds, the
chorions fuse, and the blood vessels of the two embryos
unite to form a single system. It results from this that
whatever secretions are produced by the one flow in the
veins of the other. The hormones from the male,
flowing through the body of the female, cause the sup-
pression of the reproductive organs of the lattjer. Oc-
casionally the envelopes of the two embryos remain
unfused, and in such cases, as Dr. Lillie was able to
demonstrate, the female is perfectly fertile. In sheep,
88 ZOOLOGY
while the chorions fuse, the circulations of the twins
remain distinct ; hence the sexes are normal. It rarely
happens among sheep that the female of a pair of
opposite-sexed twins is sterile, and in such cases it
must be supposed that there has been a fusion of the
circulation.
CHAPTER TWELVE
NATURE AND NURTURE
1. CONTEMPLATING the characters of any living Effects of
being, whether plant or animal, we may ask which are
due to heredity ("nature") and which to environment
("nurture"). The answer to this question assumes
great practical importance in relation to domestic
animals and plants, and still greater when we come to
consider man and all the problems of education, of
morality, and justice. First of all, however, it is neces-
sary to be quite sure what we mean by these terms. In
a broad sense, heredity and environment are alike
nature; but the custom has grown up of using "na-
ture" to mean the inherited equipment, as when we
speak of "the nature of the beast," or say, in the words
of the old nursery rhyme, "dogs delight to bark and
bite, it is their nature to."
2. With this definition or limitation, the matter Favorable
superficially appears rather simple, but it is in fact
very complex and often puzzling. We cannot say that sayy for
we came into the world as infants, with our "nature,"
and that every subsequent addition is due to "nur-
ture," though in one sense this may be true. Most
assuredly the environment provided our food, the source
of all our growth. Not only this, but the physical sub-
stance of the living body is constantly wearing away,
so that after a few years there is very little of the
original material with which we were born. A little
further inquiry shows us that long before birth we were
growing, and absorbing nourishment, so that if we wish
to go back to the actual beginning and ascertain what
our "inheritance" was, we find that it was nothing more
than a fertilized cell of the minutest size. Truly it
89
f
ZOOLOGY
Dominance
of the
hereditary
factors
seems that we
started in busi-
ness with very
little capital,
and have be-
come almost
everything we
are by taking
advantage of
the environ-
ment. In our
original phrase,
it seems to be
nearly all nur-
ture and very
little nature in-
deed.
3. We notice,
however, that
we are human
beings, and that
the offspring of
such are always
human. So also
the progeny of
elephants are elephants, of cabbages, cabbages. Why
should this be so, if the environment is the principal
thing? Heredity appears to contribute to the elephant
a single minute mass of protoplasm of microscopic size ;
the whole vast body is built up out of the nourishment
secured ; should the latter not determine the size,
form, and quality ? On the contrary, the microscopic
cell decides not merely that the creature shall be an
elephant, and no other sort of beast, but also what
Photograph by W. M. Goldsmith
FIG. 20. Two lots of potatoes raised by Mr. William M.
Goldsmith at Gunnisoh, Colorado, in 1918. Both had the
same parentage, but one lot was propagated from the larg-
est tubers in the hill, and the other from the smallest.
Similar tubers are shown at the base of each bucket.
Both lots were given the same treatment. The yield
shown in the buckets was 25 and 27 Ibs., respectively,
showing no superiority in the product of the large tubers.
Potatoes are reproduced vegetatively from the tubers
without change in hereditary qualities, except in the rare
case of a bud sport or mutation. The experiment illus-
trates the non-inheritance of acquired characters. The
little tubers were little because of differences in time of
development or position, broadly speaking of nutrition,
and not because they had inherited different qualities.
There are, however, other forms of the potato genus
which have invariably small tubers, and these will repro-
duce nothing larger, being controlled by heredity.
NATURE AND NURTURE 91
particular sort of elephant it shall be ; perhaps even
whether it shall be a good-natured, tamable elephant
or a dangerous, vicious animal ! I know a family of
people in which a dimple in the chin has been inher-
ited through five generations, though there was nothing
peculiar, nothing having to do with dimples, in the
''nurture" of all those persons. To such apparent
trifles does the grip of heredity extend ! Surely, then,
it is all "nature," and "nurture" is a negligible factor!
4. The matter is not so easily settled, though, for interreia-
when we come to study inheritance in detail we discover hereditary
that the individual has a bundle of inherited qualities, factors in
For each of these qualities, or rather determiners of dividual
qualities, all the others act as an environment. The
individual is thus complex, and the total result comes
from the interactions of many forces, internal and ex-
ternal. In man, at least, the inheritance is potentially
richer than the possible development, so that choice
partly determines the adult character. As Bergson
states : "Life is a tendency, and the essence of a tend-
ency is to develop in the form of a sheaf, creating by its
very growth divergent directions among which the im-
petus is divided. This we observe in ourselves, in the
evolution of that special tendency which we call our
character. Each of us, glancing back over his history,
will find that his child-personality, though indivisible,
united in itself diverse persons which could remain
blended just because they were in their nascent state ;
this indecision, so charged with promise, is one of the
greatest charms of childhood. But these interwoven
personalities become incompatible in course of growth,
and, as each of us can live but one life, a choice must
perforce be made. We choose in reality without ceas-
ing; without ceasing, also, we abandon many things.
ZOOLOGY
FIG. 21. The effect of environment on squash plants. The two plants shown were
grown at Boulder, Colorado, from the same lot of seeds. On the left, the ground
was left untilled; on the right, it was turned up and manured. Another squash,
from the same lot of seeds, growing just behind the big one, also had fertile soil,
and grew to a large size ; but its fruits were green and worthless, because it was
crossed with some other kind. The large plants are those which have had ad-
vantages in this world ; have been to college, as it were. But sometimes, if the
heredity is unfavorable, the environment is powerless to give satisfactory results.
The route we pursue is in time strewn with the remains
of all that we began to be, of all that we might have
become. But Nature, which has at command an in-
calculable number of lives, is in no wise bound to make
such sacrifices. She preserves the different tendencies
that have bifurcated with their growth. She creates
with them diverging series of species that will evolve
separately." (Creative Evolution, page 99.) Heredity
provides the hand of cards, but ours may be the choice
to play. Does heredity also determine that choice ?
In part, yes, but as every one knows, it is very largely
determined by the influence of others, by opportunity,
and lines of least resistance.
5. As an illustration of the force of heredity and its
independence of environment in certain cases, we may
cite the inherited dimple in the chin of the P. family.
The dimple is correlated with a depression in the bone
D$ D$ D$ D$ D$ D$
NATURE AND NURTURE 93
beneath. The facts were communicated to the writer
by Miss P., one of his former students, in whom the
dimple is very distinct. In the following pedigree the
generations are marked (i), (2), etc., $ = male, ? =
female, D = dimple present, d = no dimple. X =
married, and the vertical line below shows the offspring.
The P. family is of French-Scotch ancestry, the Scotch
side from the Macdonalds.
© D£x?9
0 D
Dimple is evidently dominant, but in the fourth' and
fifth generations we should expect some non-dimple chil-
dren. Their absence may be due to chance, just as the
children of a given family may be all boys or all girls.
Other inherited qualities, such as musical ability,
might appear much more irregularly, their successful
development depending upon a favorable environment.
Thus, while dimple is due to heredity, and appears in
any environment which permits development and
growth, 'success as a pianist requires not only favorable
heredity but special environment. Other qualities, de-
pending on the environment and not on heredity, such
as ability to speak English rather than French, are not
inherited at all. A person of French descent has as
much difficulty in learning French as one of English
descent, provided that he has had no more opportunity
to hear it spoken. This in spite of the fact that his
remoter ancestors for many generations may have
spoken French.
A society
Cooperation
organisms
Cooperation
many-celled
organisms
CHAPTER THIRTEEN
SOCIAL LIFE
1. SOCIETIES, whether among men or animals, are
groups of individuals associated together for common
ends. "Plant societies," sometimes referred to by
botanists, are groups of plants growing together, but
without the features of a true society ; they are better
called "plant associations." It is true that in forests
the trees protect one another from the violence of the
winds, and that in rather numerous cases different forms
of plants cooperate for mutual benefit. For example,
plants of the pea family have bacteria growing in their
root tubercles; and these bacteria, being able to "fix"
— or make part of an available chemical compound -
the nitrogen of the air, are in turn highly beneficial to
their. hosts. Such intimate relationships between differ-
ent species are defined by the term symbiosis (Greek,
"living together") and are not properly called societies.
2. Nevertheless, even in the lowest plants and ani-
mals the parts of the cell may be said to be joined to-
gether for common ends, the cell being a complex
machine. Thus no life can exist without a sort of rudi-
mentary socialization of the parts of the individual, and
it is the interplay between these which makes life. The
principle of cooperation may in this sense be said to
have begun with life itself.
3. In a still more obvious sense, socialization was
manifested when the first two cells remained together,
to make the beginnings of a many-celled animal or
plant. Very soon the cells thus associated began to
develop along different lines, and the several types of
tissues were formed. A human being is an extreme and
very complex example of this sort of differentiation and
94
SOCIAL LIFE 95
specialization. The myriad cells of the body have their
different functions to perform, and successful life de-
pends upon cooperation. Death results from the fail-
ure of any one set of cells to do its work.
4. Groups forming societies are found even among Social
the lower forms of animal life. Thus among the Ccelen- among the
terates, the group of the sea anemones and jellyfishes, lo^er
we have the zoophytes (Greek, "animal plants"), which
occur in groups so closely associated that we wonder
whether they constitute one animal or many. The in-
dividuals of the zoophyte "colony" are variously differ-
entiated ; some do the feeding, some the fighting (sting-
ing), others the reproducing for the group. The repro-
ductive members in many species become free, and float
about as little jellyfishes, when no one doubts that they
are separate animals. Thus socialization in these low
forms of life is extreme, but is governed by instinctive
reactions. We do not identify it with symbiosis, be-
cause the individuals, though very different, are all of
the same species.
5. Much higher in the scale, the ants and bees form Social life
complex societies, and here the fact of socialization is
plain to any onlooker. Among the ants, for example,
are males, females, and workers (sterile females), and
sometimes special forms known as "soldiers." -The
latter have very large heads, but do not possess large
brains to correspond. They are tremendous fighters,
and sometimes when their jaws have closed on an enemy
in bulldog grip they will permit their heads to be pulled
off before they will let go. All these different forms of
ants cooperate, each type fulfilling its own special tasks
and serving the interests of the city, which is the ant
hill. They make fewer mistakes than we do, because
they are governed by instincts, or in other words react
96 ZOOLOGY
in precise ways to particular stimuli, having little "free-
dom of the will." This dominance of instinct makes
them equally reliable as workers, whether in their own
nests or in those of other ants. Hence it has been pos-
sible for certain kinds to establish a system of slavery,
by stealing the immature forms of other species and
raising them to maturity. The "slaves," thus ob-
tained, work quite as well in the colonies of their ab-
ductors as they would in their own. The peculiar ant
called Polyergus, though a great fighter, has to depend
for food entirely on its slaves. There is nothing but
instinct to prevent the latter from running away and
leaving their masters to starve, but they never do so.
They are enslaved by their own natures.
6. Passing up through the lower vertebrates and
mammals, in the line leading toward man, we find very
little socialization ; practically none until we come to
the monkeys, which live in bands.1 Had man never
appeared, there would be no reason for connecting the
highest types of life with relative perfection of social
organization. Some intelligent being who might be
discussing the matter can be thought of as saying :
"Extreme socialization is very well for insects, such as
ants, but is quite unsuited for vertebrates, especially
the higher types ; a loose form of organization, in bands
or flocks, is often advantageous, but all experience is
against carrying the principle to extremes." It could
not be argued, however, that the method failed among
the ants, for these are the most successful of insects, and
literally own the earth wherever it is possible for them
to live.
1 Birds, wolves, prairie dogs, and other vertebrates occur in groups or
flocks, but they do not form highly developed societies, nor do they belong to
the series giving rise to man and his relatives, except in the very general
sense of being vertebrates or mammals.
SOCIAL LIFE 97
7. In the development of man the change of posture Deveiop-
which permitted the hands to be used for making ™m*&
things, and the long period of infancy and youth which society
gave opportunities for education or "social inheritance,"
necessarily implied a certain weakness. As compared
with other animals, man was a feeble beast, at first much
greater in his possibilities than in his performance.
Had he not become socialized, he must have become
extinct ; only through socialization could he realize his
potential powers and turn his weakness into strength.
The development of human society was guided by con-
scious purpose, and hence was progressive. No com-
bination of mere instincts could have developed fast
enough to save him, nor would it have left him free to
advance. Ant societies have been doing for at least
two million years what they do today; their social
system is static and unprogressive.
8. The human social unit, formed at first for protec- The free-
tion against the elements and from enemies, developed JaJJiidt
through the specialization of the individual. This obligation
. ,. . to decide
specialization, however, was much more plastic and
variable than that of the ants. It left a large element
of choice, and found expression in psychological rather
than structural peculiarities. No one could call into
being powers which were beyond the limits of his or-
ganism, limits set at the moment of fertilization. Yet
each one found himself potentially able to do any one of
many incompatible things, and hence not only had
"freedom of choice," but was compelled to choose.
The freedom he did not possess, and which the ant es-
sentially has, was that of escaping decisions, of evading
personal responsibility. The philosophical postulate
that actually each choice made is determined by ante-
cedent events, and hence not "free," may find logical
98 ZOOLOGY
support ; but it does nothing to save man from his ever-
lasting dilemma, his perpetually recurring choice of
good and evil. With the increasing complexity of his
social life, this choice becomes still more important and
more difficult, and organized education becomes neces-
sary. The experiences of the individual are not suffi-
cient to form the basis of his judgments, and were it not
possible for him to find a short cut through education to
the experiences of the race, modern civilization could
not exist. The glaring defects in this civilization are
largely due to the imperfections of the educational
processes which are implied in the system ; it is as
though we had a complicated machine, parts of which
were poorly constructed and out-of-date. So long as
this condition existed, the very excellence of other parts
wTould only increase the danger of disaster.
Origin of 9. Owing to the inequalities of inborn endowment,
leadership jt -g not possible, even were the educational system per-
fect, to bring every individual to the same level of effi-
ciency. It is not desirable to organize society on a basis
representing the powers and capacities of the least effi-
cient, hence leadership is necessary. Certain individ-
uals do more of the thinking and planning than others,
or do the more difficult work. There is no escape from
this arrangement without lowering the social level, but
in all ages this racial necessity has been made the excuse
for predatory or tyrannical acts. Just as the imper-
fectly educated person is like a defect in the ma-
chinery, so also the imperfectly socialized but otherwise
able individual is a menace to the state because he is
trying to do two incompatible things at once. It is
this division of activities which is referred to in the
Scriptural saying that no man can serve God and
mammon.
SOCIAL LIFE 99
\
10. When, however, the leaders are essentially honest Advantages
and socially minded, their leadership is still not without advantages
its possible disadvantages. The amount of leadership °£.leader~
desirable depends upon a variety of circumstances, but
it may be taken as axiomatic that the freedom of the
individual should be as great as his capacity permits.
It may even be better to have some things done poorly
through personal initiative than comparatively well
under direction, because the activities required bear
fruit in other ways. Aside from this, observation in-
dicates that there is a constant tendency to exaggerate
the abilities of those who have assumed leadership, and
to permit them to do a share of the social planning out
of all proportion to the superiority of their intellects.
They themselves, of course, are especially liable to this
delusion. When a leader really is far in advance of his
following, his greater sagacity is likely to be under-
estimated during his lifetime ; but he whose powers are
mediocre, and of whom all men speak well, is more
likely to be thought, and to think himself, a king by
divine right. It is not to be supposed that these con-
flicts, arising from social organization and the diversities
of individuals, will ever be overcome ; they are part and
parcel of the interplay of human life, and constitute, as
it were, the rules of the game. All we can do, or should
wish to do, is to understand these rules and play up to
the limit of our capacity.
11. We have referred to the leadership by the highly Value of
endowed of those less so ; but there is another and in-
creasingly more important type of leadership, which
depends mainly on environmental differences. In a
complex society people become specialists, and he who
has mastered what humanity knows about bacteria or
balloons takes the leadership, in regard to his specialty,
100 ZOOLOGY
over even greater men occupied in other ways. We are
told that this is an age of specialists, and it is certainly
true that we are coming to depend more and more on
leaders of this class. The more eminent, at least, also
lead by virtue of inborn ability, but the group as a
whole is a product of particular forms of education.
The arrangement permits society to act on a basis of
intelligence far exceeding that possible for a single
citizen, and through our means of communication the
wisdom of the specialists is almost immediately avail-
able to all who are able to profit by it. Conse-
quently, it becomes worth while to expend large sums
of public money in support of scientific research,
whereby truths are ascertained and become common
property. We must add, however, that even this form
of leadership, so beneficial in most respects, is not with-
out its dangers. Specialists who devote themselves to
the intensive study of particular problems are likely to
become narrow-minded, so that they fail to see the re-
lations between their own discoveries and things in
general. Their truth is true, but is not the whole truth.
Thus the fruits of special research need to be recon-
sidered and restated in the light of a broader philosophy,
and it would be a misfortune if all the ablest members of
society restricted themselves to narrow though produc-
tive fields of intellectual activity.
CHAPTER FOURTEEN
CHARLES DARWIN
1. CHARLES DARWIN was born in 1809 at Shrews- Darwin's
bury in England. His father was a doctor of medicine,
and his grandfather, Dr. Erasmus Darwin, was a rioted
poet and philosopher, with ideas on evolution. The
philosophical verse of Erasmus Darwin, written in a
style which seems artificial in these days, found many
admirers in the eighteenth century. Today we care
little for the work as literature, but are interested in the
mental tendencies exhibited, in connection with those
found in the far more illustrious grandson. The faculty
of imagination, which may make a poet and dreamer,
is no less valuable to a man of science. Charles Dar-
win came of good stock, and had many competent
ancestors in addition to those just mentioned. His
mother was one of the Wedgwoods, a family note-
worthy in many respects, but now best remembered in .
connection with the beautiful pottery made at the
Etruria works in Staffordshire. An elaborate pedigree
of the ancestors of Darwin has lately been issued by the
Francis Galton Laboratory for National Eugenics, and
it appears that these include such persons as Charle-
magne and Alfred the Great.
2. When eight and one half years of age, Darwin was Boyhood
sent to a day school at Shrewsbury. By this time his
taste for natural history, and more especially for collect-
ing, was well developed. He tried to make out the
names of plants, and collected shells, coins, minerals,
and many other things. He remarked in after years
that the passion for collecting was clearly innate, as
none of his sisters or his brother ever had this taste.
It was no doubt stimulated by the prevalent custom in
101
• //. [ ZOOLOGY
English schools of collecting various objects, so that a
new boy, on entering, is asked, " What do you collect ?"
FIG. 22.
From an old engraving
Erasmus Darwin, grandfather of Charles Darwin.
Many who have begun by collecting stamps, birds' eggs,
or butterflies, have developed into good amateur natu-
ralists. When somewhat older, Darwin began to col-
lect beetles, and not only obtained a fine series of these
insects, but was able to send rare specimens to the en-
tomologist, Stephens, who mentioned them in his work
on British Entomology. Thus the "mere collector"
came to realize that he could contribute something to
the progress of science.
CHARLES DARWIN 103
3. In 1818 Darwin went to Dr. Butler's school at The old-
Shrewsbury, and remained until he was sixteen years English
old. He had a very poor opinion of the instruction, but sch<x>1
it is evident that he made more progress than the state-
ments in his autobiography would suggest. It is diffi-
cult for us to appreciate the narrowness of the curricu-
lum of an English school of those days, with its entire
emphasis on the classical language's and theology, and
almost total neglect of science. If the product of such
an educational factory was better than might have been
expected, it was due to the invigorating influences out-
side the classroom and in the home. On the other'
hand, the translation of Latin not only served to make
the pupil familiar with that language but also contrib-
uted largely to the formation of a clear and good
English style, — a matter of the first importance for
those who, like Darwin, had something of value to say.
4. In October, 1825, Darwin went up to Edinburgh Darwin's
University to study medicine. Here he remained two ^£5 at
years, and although he never took a medical degree, he Edinburgh
must have acquired a considerable knowledge of scien-
tific subjects. He wrote home that the lectures on
human anatomy were as dull as the lecturer himself,
and the subject disgusted him. In after years he deeply
regretted that he did not dissect more diligently. For-
tunately, he made the acquaintance of several young
men interested in zoology, and the year following his
arrival at the University he read a paper before the
Plinian Society, announcing a zoological discovery of
his own. As it was evident that Darwin would never Cambridge
make a doctor, he was taken from Edinburgh and sent ^S^fL-
to Cambridge, with the idea of turning him into a sorHenslow
clergyman. At Cambridge University he was entered
at Christ's College, and although he passed his ex-
104 ZOOLOGY
aminations without difficulty, he afterwards expressed
the opinion that much of his time was wasted, so far as
academical studies went. Nevertheless, his scientific
interests were further stimulated by Professor John
Stevens Henslow, a botanist and all-round naturalist,
who rambled with him into the country around Cam-
bridge, and became his intimate friend. The dons used
to speak of Darwin as "the man who walks with Hens-
low."
The voyage 5. In 1831, on returning from a geological tour in
Wales, Darwin found a letter from Henslow stating that
the Beagle, a vessel of the Royal Navy, was about to
circumnavigate the globe, for the purpose of surveying
and charting various coasts. Captain FitzRoy wished
to have a naturalist on board, and was willing to give
up part of his own quarters to a competent young man
who would serve without pay. Could Henslow recom-
mend some one ? He could and did recommend Dar-
win, whereupon arose a great controversy in the latter's
family. Charles was "instantly eager to accept the
offer," but his father strongly objected, and regarded
the plan as so preposterous that he added : "If you can
find any man of common sense who advises you to go,
I will give my consent." This man was found in Uncle
.Wedgwood of Maer, and the arrangements were at
length made. There still exists a memorandum by
Darwin, detailing the objections raised, as follows :
"i. Disreputable to my character as a clergyman
hereafter.
" 2. A wild scheme.
"3. That they must have offered to many others
before me the place of naturalist.
"4. And from its not being accepted there must be
some serious objection to the vessel or expedition.
CHARLES DARWIN 105
"5. That I should never settle down to a steady life
hereafter.
"6. That my accommodations would be most un-
comfortable.
"7. That you [his father] should consider it as again
changing my profession.
"8. That it would be a useless undertaking."
This list is extremely characteristic of Darwin, who
had the habit of marshaling impartially the arguments
for and against any proposition. Thus it has come
about that those who may wish to find reasons against
Darwin's opinions, look for them in Darwin's works.
Undoubtedly this careful survey of the pros and cons
gave to Darwin's writings much of their extraordinary
power ; he never allowed himself to be carried away by
an idea, unchecked by the objections which careful and
prolonged thought could muster against it.
The objections to the voyage were not sustained in
the event, except perhaps No. 6; Nos. i and 7 ceased
to be objections. The hardships were accentuated by
a constant tendency to seasickness, and it was supposed
that this had to do with the physical defects which
made Darwin a semi-invalid for the rest of his life.
Since, however, a similar weakness existed in another
member of the family, who did not go to sea, it is
probable that there was a constitutional defect, which
may have been aggravated by the five years'
voyage.
6. Darwin's journal of the voyage has been published Darwin's
in what is now one of the classics of travel. As we read,
it is difficult to realize that it was written by a young
man recently graduated from college. Its style is so
mature, its thought so profound, and the knowledge of
zoology and geology shown is so remarkable, that we
I06 ZOOLOGY
should have to search long to find a parallel. No better
example could be found of the force of innate ability.
There are few passages in the literature of exploration
as charming as this description of the first day in a
Brazilian forest :
"The day ha.s passed delightfully. Delight itself,
however, is a weak term to express the feelings of a
naturalist who, for the first time, has wandered by him-
self in a Brazilian forest. The elegance of the grasses,
the novelty of the parasitical plants, the beauty of the
flowers, the glossy green of the foliage, but above all the
general luxuriance of the vegetation, filled me with ad-
miration. A most paradoxical mixture of sound and
silence pervades the shady parts of the wood. The
noise from the insects is so loud, that it may be heard
even in a vessel anchored several hundred yards from
the shore ; yet within the recesses of the forest a uni-
versal silence appears to reign. To a person fond of
natural history, such a day as this brings with it a
deeper pleasure than he can ever hope to experience
again. After wandering about for some hours, I re-
turned to the landing place ; but, before reaching it, I
was overtaken by a tropical storm. I tried to find
shelter under a tree, which was so thick that it would
never have been penetrated by common English rain;
but here, in a couple of minutes, a little torrent flowed
down the trunk. It is to this violence of the rain that
we must attribute the verdure at the bottom of the
thickest woods ; if the showers were like those of a
colder clime, the greater part would be absorbed or
evaporated before it reached the ground."
Thus, throughout the voyage, aesthetic enjoyment
and keen analysis went hand in hand, and it is not sur-
prising that the scientific results were great.
CHARLES DARWIN IO/
7. The Beagle sailed down the coast of South America Discoveries
and through the Straits of Magellan ; then northward lanfdgeign
up the coast of Chile, to the Galapagos Islands ; thence
across the Pacific, where Darwin made his famous study
of coral islands, to Australia and New Zealand ; from
Australia across the Indian Ocean to Cape Colony, then
once more across the Atlantic to Brazil, and home. In
South America Darwin made long trips overland, doing
a great deal of important zoological and geological work.
He discovered the bones of many remarkable extinct
animals, which were afterwards described by Professor
Owen. A skull representing a new suborder of mam-
mals was found in the yard of a farmhouse, where small
boys were amusing themselves by throwing- stones at it.
Among living creatures perhaps the most interesting was
a new species of South American ostrich, which received
the name Rhea darwinii. In the Galapagos Islands,
Darwin noted that the different islands had distinct
species of birds and reptiles, and that the degree of re-
semblance between these species was roughly in pro-
portion to the distance between the islands. This
caused him to begin thinking definitely about the
mutability of species, though he had as yet no theory
or distinct opinion.
8. In October, 1838, Darwin chanced to read the Maithuson
Essay on Population, by Malthus, which was then ^^he*011'
attracting a good deal of attention. In this work it was senn of ^e
pointed out that populations tended to increase, and natural
consequently press on the means of subsistence, which selectlon
must be limited. Hence the process could not go on in-
definitely. Darwin relates that : " Being well prepared
to appreciate the struggle for existence which every-
where goes on, from long-continued observation of the
habits of animals and plants, it at once struck me that .
Ip8 ZOOLOGY
under these circumstances favorable variations would
tend to be preserved, and unfavorable ones to be de-
stroyed. The result of this would be the formation of
new species. Here, then, I had at last got a theory by
which to work ; but I was so anxious to avoid prejudice,
that I determirted not for some time to write even the
briefest sketch of it." Even before reading Malthus,
he had dimly perceived the consequences of non-adapta-
tion to surroundings, but now the matter became rela-
tively clear and definite in his mind. In 1842 he wrote
a rather full but rough statement of his views, which he
did not attempt to publish. It was printed at the time
of the Darwin Celebration at Cambridge in 1909, and
in it we can see the foundations of The Origin of Species,
published seventeen years later, in 1859.
Emma 9. In 1839 Darwin married his cousin, Emma Wedg-
wood. The union was in all respects a happy and fruit-
ful one. Mrs. Darwin, though not scientific, was a
person of quite unusual ability and character, and her
devotion to her husband is described by one of her sons :
"If the character of my father's working life is to be
understood, the conditions of ill health, under which he
worked, must be constantly borne in mind. No one,
indeed, except my mother, knows the full amount of
suffering he endured, or the full amount of his wonderful
patience. For all the latter years of his life she never
left him for a night ; and her days were so planned that
all his resting hours might be shared with hen She
shielded him from every avoidable annoyance, and
omitted nothing that might save him trouble, or pre-
vent him from becoming overtired, or that might allevi-
ate the many discomforts of his ill health. I hesitate
to speak thus freely of a thing so sacred as the lifelong
devotion which prompted all this constant and tender
CHARLES DARWIN
109
DARWIN COMMEMORATION
1809—1859-1909
CAMBRIDGE
UNIVERSITY
BANQUET
23 JUNE 1909
Charles Darwin
MT. 59
FIG. 23. Reproduction of cover of the Darwin Memorial Dinner souvenir, com-
memorating the one hundredth anniversary of Darwin's birth and the fiftieth anni-
versary of the publication of his greatest work, The Origin of Species.
110 ZOOLOGY
care. But it is, I repeat, a principal feature of his life,
that for nearly forty years he never knew one day of the
health of ordinary men, and that thus his life was one
long struggle against the weariness and strain of sick-
ness. And this cannot be told without speaking of
the 'one condition which enabled him to bear the
strain and fight out the struggle to the end." (Francis
Darwin.}
Monograph io. In 1842 Darwin settled near the village of Down
in Kent, where he remained for the rest of his life. Al-
though not far from London, it was a thoroughly rural
spot, with plenty of flowers and birds. Here, during
the next fifteen years, the various works arising out of
the voyage of the Beagle were completed, and in addi-
tion Darwin wrote a monograph of the living and fossil
Cirripedia or barnacles. This latter, being strictly tech-
nical, is unknown to the public, but it was a first-class
piece of zoological work, and has stood the test of time
as few such writings have. Some critics regretted that
a man of Darwin's ability should have spent so much
time describing and classifying innumerable specimens ;
but he always said that the experience was most valu-
able to him, as it brought him into intimate contact
with the problem of species. The naturalist who shirks
such drudgery, in order to give his time to larger and
more attractive projects, will certainly fail from lack of
detailed knowledge of his materials. While all this was
going on, Darwin was patiently accumulating data of
all sorts bearing on the problem of evolution, experi-
menting on his own account, reading books of every
kind, and corresponding with people all over the world
who might be able to help him with facts. Yet he did
not publish, and confided his views to only a few of his
most intimate friends.
CHARLES DARWIN III
ii. The publication of Darwin's theory was finally Da. win and
brought about by an extraordinary coincidence. Alfred
Russel Wallace, a naturalist then traveling in the Malay
Archipelago, was attacked with malarial fever when at
Ternate in the Moluccas. During his periods of pros-
tration he had time to think over problems which in-
terested him, and his mind followed along the very lines
which Darwin's had in 1838. He also had read Malthus
on Population, and like Darwin was well prepared by
his great knowledge of living nature to appreciate the
struggle for existence. He immediately perceived that
he had hit upon a great principle, and as soon as he was
well enough wrote out a rather full statement of it, with
a view to publication. Wondering what he should do
with the paper, he thought of Darwin as a man who
would be likely to understand and appreciate the argu-
ment. So he forwarded the manuscript to him, asking
him to have it published by some society if it seemed
worth while. Darwin was amazed to read an account
of the very theory he had been elaborating for so many
years, in words practically identical with those he would
have used himself. Here was a chance for rivalry, but
it is pleasant to record that the two men were rivals only
in the sense of each endeavoring to give fuller credit to
the other than was claimed. Darwin was so conscien-
tious that he at first wished to publish Wallace's paper
and say nothing about his own labors. For, said he,
"it was by the merest accident that Wallace sent his
paper to me. Had he sent it elsewhere, it would have
been printed, and he would have had priority, for I had
no intention of publishing at present." Fortunately he
consulted Sir Charles Lyell, the geologist, and Sir
Joseph Hooker, the botanist, his two best scientific
friends, who already knew about his work. They pro-
112
ZOOLOGY
The Origin
of Species
Varied
studies in
later years
posed that Darwin should prepare an abstract of his
views, and this, together with Wallace's paper, should
be read before the Linnaean Society of London. This
was done on July i, 1858. Fifty years later, the Society
celebrated the event in a special meeting, which Wallace
and Hooker attended. Wallace, when he came to write
his great book on evolution, called it Darwinism.
The next year, 1859, saw the publication of Darwin's
book, The Origin of Species, and immediately the whole
civilized world was agog with discussions on evolution
and its relation to religious belief. Darwin found him-
self in a whirlwind of controversy, in which he was bit-
terly assailed and vigorously defended ; but he kept out
of the arena and quietly continued his researches. His
friend, T. H. Huxley, pursued a very different course.
A brilliant naturalist and master o£ English, he de-
lighted to battle for what he understood to be right,
and appeared here and there, on the platform and in
the press, in defense of the new theory of evolution. It
was very largely owing to Huxley that the new doctrine
became so widely understood. Ultimately Darwin's
victory was practically complete. Almost all living
naturalists, except the oldest, were converted. The
Church, at first bitterly hostile, became acquiescent.
After Darwin's death, when a statue was erected to his
memory in the great hall of the Natural History Mu-
seum, the three chief partakers in the ceremony were
the Prince of Wales (afterwards King Edward VII), the
Archbishop of Canterbury, and Professor Huxley.
12. The last twenty years of Darwin's life, from
1862, were occupied by labors so varied and important
that it would be difficult to understand how they could
be undertaken by one in robust health, and it is
marvelous that they should have been performed by an
CHARLES DARWIN 113
invalid. Possibly the ill health itself had a certain ad-
vantage, for it compelled Darwin to spend a large part
From an engraving
FIG. 24. Thomas Henry Huxley.
of each day resting, and no doubt turning over in his
mind the various problems connected with his work.
Most of us are so active, rushing to and fro, that we
have not sufficient time for thought. In continuation
of the work on the theory of evolution appeared in 1868
The Variation of Animals and Plants under Domestica-
tion^ and in 1871 The Descent of Man. The former gave
an abundance of data concerning the phenomena of
variation, and the effects of selection by man ; the latter
114 ZOOLOGY
discussed the evolution of man in general, and set forth
the supplementary theory of sexual selection. In 1872
appeared The Expression of the Emotions in Man and
Animals, in which it was shown that corresponding
muscles existed, which in contraction expressed more or
less similar feelings. Thus a certain psychological con-
tinuity in evolution was established, corresponding with
a morphological one. Observations on his own children
in early infancy were included in this study. There was
also a series of important botanical works, concerned
with the structure and fertilization of orchids (1862),
insectivorous plants and the movements and habits of
climbing plants (1875), the effects of cross- and self-
fertilization (1876), different forms of flowers on plants
of the same species (1877), and the power of movement
in plants (1880).
Earthworms The last book, published in 1881, was on The Forma-
tion of Vegetable- Mould, through the Action of Worms.
Darwin had observed that objects left on the ground in
England disappeared after a period beneath the earth,
and seeking the cause, noted that earthworms were con-
tinually bringing soil to the surface as a result of their
feeding and burrowing operations. This turning over
of the soil is of great importance from an agricultural
point of view, and the extent to which it goes on was
proved by a long-time experiment in which the power
of worms to bury objects was thoroughly tested.
Darwin died on April 19, 1882, and was buried in
Westminster Abbey, a few feet from the grave of Sir
Isaac Newton.
References
DARWIN, FRANCIS. Life and Letters of Charles Darwin. 1887.
DARWIN, FRANCIS. More Letters of Charles Darwin. 1903.
LITCHFIELD, HENRIETTA. Emma Darwin. A 'Century of Family Letters.
1915.
POULTON, C. B. Charles Darwin and the Theory of Natural Selection. 1896.
CHAPTER FIFTEEN
VARIATION
1. WE say that things are "as like as two peas," but Variability
two peas are not exactly alike. Everywhere among umversal
living beings we find variation ; the individuals of a
species differ in various ways from one another. Some
creatures are much more variable than others ; char-
acters which separate species in one group may only
distinguish individuals in another. Sometimes one
stage is more variable than another ; differently colored
caterpillars may produce a very uniform lot of moths,
as in the case of the white-lined sphinx. In other cases
the immature stages are very uniform, but the adults
vary.1 Even when the variations are many and im-
portant, they follow certain lines, they are not indis-
criminate. Consequently, when a particular sort of
variety has been found in one species, we expect to see
similar variations in related species. What the cone-
flower has done, the sunflower will do.
2. These variations, though all classed under one
general heading, really represent several quite different
phenomena. Theoretically we distinguish the follow-
ing:
a. Variations due to changes in the germ plasm itself, Different
or "original variations." These may be due ***&*?*
variation
1 For beautiful illustrations of variations in caterpillars and moths, see
Packard's work on the Saturniidae, or great silk moths, in Memoirs National
Academy of Sciences, Vol. XII (First Memoir), 1914. For variation in
snails and slugs, see the colored plates in J. W. Taylor's Monograph of the
Land and Freshwater Mollusca of the British Isles, or H. A. Pilsbry's work
on Liguus, in Journal of Academy of Natural Sciences of Philadelphia, Vol.
XV (2d Series), 1912. All these works illustrate the subject in color in the
most exquisite manner. Any dealer in shells will supply series of Helix
nemoralis and various marine shells, illustrating variation. Leaves and
flowers (especially garden flowers) afford endless examples.
"5
Il6 ZOOLOGY
either to the addition of something to a deter-
miner, or the loss of something, or conceivably
to a shifting or shuffling of what is already
there. Such a variation might occur in a de-
terminer, through some chemical change in the
protoplasm, and if recessive to the normal, pro-
duce no visible effect for hundreds of genera-
tions. It is therefore very difficult to say that
a variation is "new," in a genetic sense. Even
if we are sure that we have witnessed its first
appearance on the stage, we may not know how
long it has been waiting behind the scenes.
The discovery of multiple allelomorphs is signifi-
cant in this connection. These are various
determiners which appear to occupy exactly the
same place in the same chromosome, and there-
fore cannot coexist in a gamete. The inference
is very strong that these are actually mutations
of a single original substance. A good example
is found in the fly Drosophila, in which several
different eye colors appear to be due to modi-
fications of a single determiner. No gamete can
carry more than one of these modified factors,
and only two can coexist in a zygote.
b. Variations due to the loss of a determiner. Since
Bridges has shown that a fragment may dis-
appear from a chromosome, this type of varia-
tion is evidently possible. In numerous cases
the allelomorphs (alternative characters) are to
each other as plus and minus, positive and
negative, and this fact has given rise to the
"presence and absence theory." According to
this view, the recessive is simply the absence
of that which is represented by the dominant.
VARIATION 117
The fact of multiple allelomorphs throws new
light on this matter, and we must doubtless say
that the recessive determiner is not simply a
vacant spot, but is a real factor which does not
function as does the dominant. Hence this
class of cases falls under our group <z, rather
than under the present group. Still, we must
admit that sometimes there is actual loss of sub-
stance instead of modification, and there is
reason for thinking that this may very rarely
be brought about by environmental factors.
There may be, in some cases, a selective de-
struction of the items of inheritance.
The above two types of variation are the most diffi-
cult to study and understand, but also the most im-
portant, since they will permanently modify the
material of inheritance. Could we bring them about
experimentally, we could practically produce new
species. Even then, we could work along only certain
lines which the character of the germinal substance
permits, just as the chemist can make only certain
compounds. It is probably fortunate that man has
not been able in this manner to play the parfe of a
creator ; he would doubtless have made a mess of
things. Nature may be "blind," but working in the
long run and the fullness of time, she does her work
better than we could hope to imitate.
3. Two other classes of variations have nothing to New corn-
do with any change in the germ plasm itself. ShS
c. Variations due to new combinations. These have qualities
been discussed under Mendelism and the Red
Sunflower. It is evident that they will break
up again, forming still other combinations, ex-
cept when they become homozygous. In the
n8
ZOOLOGY
Effects of
environment
Varieties,
subspecies
latter event, practically new constant forms
may arise, representing no new factors but the
old factors newly distributed. They are like
new words, formed out of the old letters of the
alphabet. It is probable that this process has
been a factor in evolution.
d. Variations due to environmental conditions acting
on the body or mind, such as education, the
effects of starvation, cuts or wounds of any
kind, and so forth. These are not inherited.
Although this kind of variation has no direct
significance for evolution, it is not without its
importance. Except in the case of purely ex-
ternal injuries, the variation observed is only
in part due to environment. That is to say, it
represents the response of the organism to cer-
tain conditions, and the nature of this response
is determined by heredity. The ability to re-
spond, as in education, is part of the inherited
adaptability of the animal. Now this will often
be a prime factor in the struggle for existence,
enabling the creature to survive where others,
• less ready to become modified, will perish. In
the case of man, especially, all his higher
achievements are conditioned by his extraordi-
nary tducability, and the educational process
has to be repeated in each generation.
When environmental conditions (e.g., alcohol) af-
fect the germ plasm, there may be results
appearing in the next generation, as we shall
see below.
4. In zoological and botanical nomenclature, the
word "variety" is used very loosely. The student
usually has to deal with preserved specimens, and does
VARIATION 119
not know how the variations have been brought about,
though he can often reason from analogy. Among
birds and mammals, especially, it has become custom-
ary to recognize subspecies. A subspecies is a phase or
form which is reasonably true to type within a given
area, but at one or more points intergrades with its
allies occupying adjacent territory. As Beebe has
shown in the case of birds, the peculiarity (e.g., a
darker or lighter color) may be due to the immediate
effects of environment, and the intergradation may be
merely the expression of the intergrading climatic condi-
tions. On the other hand, Sumner, experimenting with
subspecies of wild mice, has found genuine hereditary
differences. Mere inspection would not show which
kind of " subspecies" we were dealing with. Suppose
the differences to be inherited, the intergradation where
two types meet may be due to hybridization. Ento-
mologists recognize varieties and aberrations. The
aberration or "sport" is supposed to occur occasionally,
here and there. It may be known only by a single
specimen, though the species to which it belongs is
common. It is found, however, that the same kind of
difference may distinguish an aberration in one place,
and a local race or subspecies in another ; and exactly
the same thing is true of plants. Botanists use the
word "form" or "forma" to designate minor varieties,
but with no regard to their genetic significance. Ulti-
mately the nomenclature of varieties will have to be
revised in the light of genetic research, but it is not
possible to do this thoroughly at present.
CHAPTER SIXTEEN
Supposed
inheritance
of
alcoholism
ALCOHOL AND HEREDITY
I. Is "alcoholism" inherited? This question has
been much debated, but it has been difficult to reach a
definite conclusion. An affirmative answer is suggested
by such instances as the following. A normal woman
married a normal man, and the three children were all
normal. Her husband died, and she married a drunk-
ard. The three children from this union'were all defec-
tive, two being drunkards. The second husband died,
and again the woman married, this time a sober man.
The children produced were sound and normal. Ob-
viously, it seems, the children of the second marriage
inherited their father's alcoholism. But what did they
inherit ? There is no proof that the large quantities of
alcohol consumed by the father caused the alcoholism of
the children. It is at least as likely that the father
himself was defective, and his addiction to alcohol was
an effect rather than a cause. Perhaps the children
would have shown defects had there been no such sub-
stance as alcohol. As a matter of fact, in the case cited,
they did show other defects than a tendency to drunk-
enness. One never developed properly, and .two were
tuberculous. The question, "Is alcoholism inherited ?"
thus assumes a new meaning. We used to think that
consumption or tuberculosis was inherited, but it is now
known to be due to a particular bacillus. What is in-
herited is a susceptibility to the attacks of this bacillus.
Of course, when the bacillus is present, this comes to the
same thing in a practical sense as if the disease itself
were inherited. So also with alcoholism. If it is the
tendency to succumb to temptation in the presence of
alcohol which is inherited, then "alcoholism" may be
"inherited" in the same sense that consumption is.
120
ALCOHOL AND HEREDITY 1 21
2. Miss Anne Moore some years ago prepared an Alcoholism
interesting report on the feeble-minded in New York, mindedn^ss
and the facts set forth have a direct bearing on the
problem of alcoholism. She quotes from the report of
the British Royal Commission on mental defectives,
and shows that it agrees with the American results.
The Royal Commission found that over 62 per cent of
all chronic inebriates were mentally defective, and that
such defective persons reacted to the effects of alcohol
more readily than normal ones. Miss Moore found
that alcoholism was closely connected with various
kinds of mental deficiency. It became a deciding factor
in many cases, because it brought those who had poor
natural endowments below the level of efficiency. Dr.
H. H. Goddard. in his recent (1914) book on Feeble-
mindedness, discusses this problem at some length.
He reaches the following conclusion: "Everything
seems to indicate that alcoholism itself is only a symp-
tom, that it for the most part occurs in families where
there is some form of neurotic taint, especially feeble-
mindedness. The percentage of our alcoholics that are
also feeble-minded is very great. Indeed, one may say
without fear of dispute that more people are alcoholic
because they are feeble-minded than vice versa."
3. Thus the matter might have rested, but for the Experiments
work of the experimentalists. It is not possible to ex- ^ gum
periment with man, and the most carefully collected
statistics are open to the objection that they represent
the effects of various causes. Dr. Charles R. Stockard
of New York undertook a series of investigations on
guinea pigs, and obtained decisive results which are now
famous. Guinea pigs reproduce so rapidly that it is
possible to have many successive generations under ob-
servation, and satisfy oneself that the stock used is
122
ZOOLOGY
Defective
young from
alcoholized
parents
Results of
injury to
germ cells
of male
parent
normal. Under ordinary circumstances, they do not
drown their sorrows in alcohol ; there are no " alcoholic"
families, nor is there any alcoholic past to complicate
matters. The reactions of these animals ought to be
perfectly naive and natural. In order to avoid the
complications arising from indigestion, Dr. Stockard
gave the alcohol in the form of vapor, which the guinea
pigs inhaled for definite periods. The individuals thus
treated often became blind, from the effect of the al-
cohol on the surface of the eye, but in other respects
they were little if at all injured. After a long period of
treatment they remained fat and vigorous. Neverthe-
less, their offspring plainly showed that they were affected
by the alcoholism of their parents.
4. In the first place, the alcoholized individuals pro-
duced fewer young, and of these very many were still-
born, or died not long after birth. The survivors were
many of them markedly defective. The defects prin-
cipally concerned the central nervous system and special
sense organs. Tremors and paralysis were very com-
mon, as also were defects of the eyes. In extreme cases
the entire eyeballs and optic nerves were absent in the
descendants of alcoholized animals. As the size of the
litters was reduced through so many premature deaths,
it sometimes happened that rather strong animals were
produced in badly alcoholized lines. This resulted from
the advantage gained from being the only one in a
litter, and thus getting all the nutriment available.
5. It might be supposed that since the young are de-
veloped in the body of the mother, the condition of the
mother, resulting from the alcohol, would be the de-
cisive factor. Thus it would not be a matter of inheri-
tance at all, in the proper sense, but only of injury to
the young animal before birth. Dr. Stockard's experi-
ALCOHOL AND HEREDITY 12$
ments gave an exactly opposite result. There was a
larger proportion of degenerate, paralytic, and grossly
deformed animals descended from the alcoholized males
than from the alcoholized females. In other words, the
sperm cells were more sensitive to the poison than the
egg cells. It is a marvelous thing, considering the
minute size of the sperm, that this almost infinitesimal
particle should be affected in a definite way, so as to
produce very conspicuous results in the animal to which
it in part gives rise. This is of course only an aspect of
the familiar marvel of heredity, but being new, it as-
tonishes us more.
6. We may now return to our first question. In the injured
light of Dr. Stockard's experiments, is alcoholism in- f^™^8
herited ? The offspring of the alcoholized guinea pigs offspring
were of course not alcoholics ; they showed various
defects, including low vitality. They showed characters
not present in their alcoholized parents at all. How, then,
can we speak of inheritance ? What really happened in
these cases ? The alcohol, penetrating to every part of
the body, injured the substance of the germ cells. The
germ plasm was directly affected, and its functions were
impaired. There was no tendency to produce new
varieties of guinea pigs ; the effects were pathological,
such as might be produced by poisonous substances in
any living tissues. It simply comes to this : the germ
cells, with their chromosomes and the rest, are, after all,
living protoplasm. They are not able to resist injurious
influences in every case, though their power of resistance
may be great. The history of life shows us how ger-
minal complexes have retained their substantial identity
for ages, unmodified or little modified by all the vicissi-
tudes of existence. Yet they have not wholly charmed
lives ; they may be injured by the direct action of cer-
I24
ZOOLOGY
tain substances or conditions, so that the individuals
they produce, if they produce any, are below the normal
standard.
7. The germ plasm is the vehicle of life which con-
tinues from generation to generation. Will it recover
from the injury, or will the effects continue "unto the
third and fourth generation"? Stockard records that
"the mating records of the descendants of the alcohol-
ized guinea pigs, though they themselves were not
treated with alcohol, compare in some respects even
more unfavorably with the control records than do the
data from the directly alcoholized animals." To be
specific, of 194 matings of non-alcoholized offspring of
alcoholized parents, 55 resulted negatively or in early
abortions ; 18 stillborn litters of 41 young occurred, and
17 per cent of these stillborn young were deformed.
One hundred and twenty living litters contained 199
young, but 94 of these died within a few days and almost
15 per cent of them were deformed ; while 105 survived,
and 7 of these showed eye deformities.
These defects continue even to later generations. Dr.
Stockard goes on : "The records of the matings of F2
animals (F2 means second filial generation, or grand-
children of the original parents) are still worse, higher
mortality and more pronounced deformities, while the
few Fa individuals which have survived are generally
weak and in many instances appear to be quite sterile
even though paired with vigorous, prolific, normal
mates."
8. After reading the accounts of Stockard's experi-
ments, we turn to the still more recent work of Dr.
Raymond Pearl on fowls, and are astonished to find
that his results appear to be contradictory. The
methods used with the fowls were parallel with those
ALCOHOL AND HEREDITY 125
employed on the guinea pigs, and naturally we should
expect to get similar results. In one respect there is
complete agreement. The proportion of fertile eggs
was reduced by subjecting the parents to alcohol ; the
higher the dosage the smaller the number of zygotes
formed. On the other hand, the number of embryos
which after being formed died before hatching, and the
number of individuals dying after hatching, was actu-
ally less among the offspring of alcoholized than un-
treated birds. When both parents were alcoholized,
the average weight of the offspring at hatching was
greater than when one or neither received treatment.
The superiority of the offspring of fowls subjected to
alcohol was maintained during their subsequent de-'
velopment, and they showed no greater proportion of
abnormalities than the controls.
9. How can such contradictory results be explained ? Explanation
Dr. Pearl supposes that the essential facts are about as
follows : The gametes or germ cells vary in their vitality,
and are not equally affected by any deleterious agent.
Consequently, on treating the parents with alcohol or
any similar substance which reaches the germ plasm,
we may expect to find three classes of effects :
a. Some cells will be destroyed, or so injured that
they are incapable of forming viable zygotes.
b. Some cells will be injured, but will form zygotes
which are capable of living, though variously
imperfect or pathological.
c. Some cells will not be appreciably affected.
It will be seen that this situation parallels the effects
of disease on adults. . In the presence of some acute
bacterial diseases, some will die, others will live but
suffer injury, still others will escape unharmed. In the
case of bacterial disease, there is little or no evidence
126 ZOOLOGY
that the elimination has any effect beyond producing
(selecting) a race capable of withstanding the disease,
except in cases where there is a mixture of races, which
respond differently to the influence. In the latter class
of cases, the surviving type may be superior or inferior,
judged by general standards, to that perishing. Dr.
Pearl assumes, however, that the selective action of
alcohol or other poisons on the germ cells is such as to
eliminate all the weaker gametes, — those which under
normal circumstances would produce the poorer class of
the population. Consequently, if Classes a and c are
large, the survivors (Class c) will really be the best
gametes,, — not improved in any way by the alcohol,
but producing better zygotes on the average, because
originally more vigorous. The infertile eggs represent
the smaller, less viable elements of the ordinary chicken
population.
In the guinea pig, on the other hand, while Class a is
approximately as in the fowl, Class b includes practically
all the survivors. Few cells escape some injury. Hence
Dr. Stockard's results. Why should guinea pigs and
fowls thus differ ? We cannot say at present, but it is
not surprising that the cells of such different creatures
should differ in their resistance to poisons. Analogous
differences can be observed in the' same species (e.g.,
man), with regard to the poisons of different bacteria.
In some diseases most or all of those affected perish,
while the rest remain uninjured. In others, while some
perish and some escape, large numbers are variously
injured. As Pearl points out, the results will differ
according to the dosage. If the amount of poison used
is sufficient, all will fall in Class a ; that is, there will be
no offspring. Of course it may not always be possible
to attain this result without killing the parents. Short
ALCOHOL AND HEREDITY 127
of this extreme, a certain number will fall in Class <z, .
while the rest will be in Class b, all showing injury.
Still diminishing the dose in proportion to the power of
resistance, Class c will begin to appear, and become
larger as the amount of poison used decreases. In
birds, the high temperature and rapid metabolism
doubtless favor the rapid elimination of alcohol ; thus
the dose, though apparently identical with that of the
guinea pigs, is in effect less. It may well happen in
some cases that when Class b is small and Class c large,
the statistical results will show an actual improvement
over the normal population, in spite of the fact that a
certain number suffer injury.
10. If, as appears certain, alcohol thus discriminates Outstanding
against the weaker gametes in the fowl, what will be the pr°
effect on future generations ? It all depends on the
source of the relative weakness. Is it a matter of
hereditary composition, or of differences of nourish-
ment, dependent possibly on position ? In the latter
case there will be no permanent effect ; in the former,
the average of the later generations should at least in
some degree maintain the observed superiority. Thus,
by an extraordinary paradox, it would be possible to
improve a breed of fowls by administering alcohol to
one or more generations. Experiments are now in
progress, designed to settle this question.
If the germinal difference is hereditary, we should
expect a strongly heterozygous or cross-bred type to
show the effects more distinctly than a homozygous one.
In such a mixed type there might be many different
sorts of gametes, which might respond differently to
environmental influences.
11. We now return once -more to our original ques-
tion. There is no reason to suppose that alcoholism, as
128 ZOOLOGY
Results vary such, is inherited ; but alcohol may affect the germ cells
and'power *n sucn a wa7 as to produce defectives of various kinds,
of resistance even when it does not injuriously affect the health of
the parents. This injurious result may be carried
through generations, though they have never touched
alcohol. On the other hand, if the dose is less in pro-
portion to the power of resistance, a large number of
gametes may wholly escape injury, and these may be
the strpngest members of the gametic population. Pro-
fessor Karl Pearson of London has published statistics
which seem to indicate the absence of any inferiority
in the offspring of a series of workingmen. addicted to
alcohol. Thus the practical results may be diametri-
cally opposite, according to the ratio between the poison
and the ability to resist it, and the way in which the
poison operates. A priori considerations indicate what
is possible, but actual experience is necessary to show
what will happen in the case of any particular species
or race, under any particular conditions.
Dr. Goddard's evidence, showing the association of
alcoholism with nervous disorders or feeble-mindedness,
no longer possesses quite the meaning he attached to it.
It is indeed a symptom, but the guinea-pig experiments
show that nervous defects are precisely those which re-
sult from the injury to the germ plasm by alcohol in a
previous generation. Of course no one will claim that
they are necessarily due to this cause, but in any given
case it at least appears possible.
CHAPTER SEVENTEEN
NATURAL SELECTION
I. A FIRE, once lighted, burns in all directions until The ex-
the fuel is exhausted. Life 'similarly extends, flowing
into every possible channel until checked by circum-
stance. It is possible to imagine a universe which
might become completely vitalized, alive in all its
parts ; but immediately it would produce non-living
waste materials, as the result of its own activity. Burn-
ing or living are states which, from their nature, imply
the coming and going of material ; hence a house cannot
be all on fire, or a person all alive. By the constant
addition of fuel, the sacred flame can be kept burning
indefinitely ; by a similar process the flame of life has
been kept burning these many million years. The
activity has been continuous, the materials ever chang-
ing.
2. When we speak of life seeking opportunity for ex- Lifeevery-
tension, we need not imply anything more purposeful
than the similar activity of the fire. Living beings
feed, grow, and reproduce. These processes, un-
checked, lead to increase in what is called geometrical
progression, like compound interest. It is easy to
calculate that any common roadside weed, occupying a
square foot of ground and producing 500 seeds in a
season, would in a few years cover the whole land sur-
face of the earth with its offspring, if all survived. As
a matter of fact it does nothing of the sort ; most plants
and animals are about as numerous one year as the
next, the population remaining constant. Even when
there is a rapid increase, as for example when the so-
called Russian thistle reached this country, it is tem-
porary, and does not go nearly to the theoretical limits.
129
1 3o
ZOOLOGY
Ratio be-
tween
numbers
and chance
of survival
3. Why should life thus press against the environ-
ment, seeming ever to seek the impossible ? In a cer-
tain sense, the hunger of life and the hunger of fire are
parallel phenomena, as St. Francis seems to have dimly
perceived when he regretted having deprived "brother
fire" of the opportunity to consume his coat. There
is, however, another point of view. Life cannot extend
indefinitely ; everywhere it finds limits to its activities.
The 500 seeds of the roadside weed are so many trials,
experiments, tickets in the great lottery of the world.
It is practically impossible for all to succeed, and conse-
quently, were no surplus produced, life would become
extinct. By a strange paradox, it becomes necessary
to accept failure in order to attain success. Sacrifice is
part of the game, and those who fail have played their
part. There is actually a definite ratio between the
number of offspring and the chances of survival. The
scale insect which produces a family of six thousand
prospers as a species, but the individual at birth faces
fearful odds. We recall the old story of the lion and the
fox. The lioness goes forth with her single cub, and
meets mother fox with her many children. "Ah," says
the fox, " I have a fine family ; I am sorry for you, with
only a single cub!" The lioness replies: "I beg you
to recall that my child is a lion, yours are only foxes !"
Biologically, the lion is quite right. Species which pro-
duce few young are those in which the rate of survival
is correspondingly high ; one lion is worth several foxes,
and thousands of spiders, in this sense. Nevertheless,
even the most successful forms of life cannot avoid
losses, and were man himself to produce on the average
only two children for each pair of parents, our species
would vanish from the earth.
NATURAL SELECTION 131
4. Since the process of elimination must go on, is it The struggle
perfectly haphazard ? Is the lottery altogether im-
partial? Surely not; we have only to think for a vivaiofthe
moment of the causes of premature death. Disease
may not spare the best, from our point of view, but it
picks and chooses in its own manner. Some deaths are
due to what we call "pure accident," but the more we
examine into the subject the smaller this accidental
group appears to become. Creatures attacked by
enemies may fight or fly, but they differ in their ability
to do either. Individuals are not exactly alike, and
consequently their chances of survival are not alike.
After all, it is not Nature which chooses, if by " Nature"
we mean an external, impersonal agency. Nature would
be impartial, if the behavior of life were uniform. The
process we have just described, which is going on every-
where and at all times, is what Darwin called Natural
Selection. Its consequence is the Survival of the Fittest.
The effort to survive is spoken of as the Struggle for
Existence. These expressions are now classical, and
cannot be changed ; but they need a little explanation.
The struggle for existence appears to imply volition, but
this is not intended. There is volition in the effort to
obtain food, or to fight enemies ; but the defense of the
body against the attacks of bacteria is quite uncon-
scious. Plants, which we do not think of as being
aware of things, struggle for existence as much as ani-
mals. Then, again, the survival of the fittest implies
only fitness to survive under the given conditions. Ideal
fitness has nothing to do with it. One who is fit to go
through college may not be fit to resist smallpox or
swim when thrown into the water. Moreover, the only
fitness we are concerned with is that to produce off-
spring. Creatures may live to old age, yet remain
132
ZOOLOGY
Natural
selection
compared
with selec-
tion by man
Modifica-
tions of
Darwin's
theory
wholly unfit in the Darwinian sense ; their race does not
survive.
5. The phenomena we have just described can be ob-
served at any time ; their existence does not admit of
dispute. The question is, what have they to do with
evolution ? Is the race altered by the survival of the
fittest ? The whole matter turns on the question
whether, since the survivors differ from those which
perish, the differences will be transmitted to future
generations. Darwin took this for granted, and was
fortified by the experience of mankind in producing
many special varieties of animals and plants through the
agency of selection. In one sense, of course, man had
not produced these things, he had only chosen them ;
but their selection and isolation, and often recombina-
tion, had in effect changed the character of the popula-
tions. Man had done this, as for instance with the
sugar beet, in the course of a few years. Was it not
reasonable to suppose that Nature could do the same,
given almost unlimited time ?
6. Since Darwin's day our knowledge of the processes
of heredity has greatly increased, and consequently the
whole subject has had to be reconsidered. It is no just
criticism of Darwin, that he did not introduce into his
reasoning facts which were then unknown. First came
Weismann, the eminent zoologist of Freiburg in Baden,
with his theory of the continuity of the germ plasm.
He pointed out that each new generation arose from the
special reproductive cells of the one before, and conse-
quently the effects of environment on the organism
could not be inherited. The only exceptions to this
rule would be those in which the germ plasm itself was
affected. This theory at first caused surprise, but cases
brought forward to show the "inheritance of acquired
NATURAL SELECTION 133
characters" broke down on. examination. The char-
acters, if acquired, were due at least in part to the
hereditary constitution, and hence would be reproduced
from the germ cells. Even if the inheritance of ac-
quired characters sometimes occurred, it was certainly
too rare to be important.
The process of natural selection of course knows noth-
ing of these matters. The creature is selected on ac-
count of what it is, no matter how it became so. Thus
a highly educated person of mediocre ability would have
an advantage over an uneducated one who might be
markedly superior from the standpoint of inheritance.
If the principal characters of organisms were such as are
not inherited, natural selection could do nothing for
evolution ; there would be no relation between fitness
to survive and ability to leave fit offspring. Obviously,
this is not true ; but we can no longer assume that all
sorts of variations tend to be inherited.
7. The researches of Mendel, greatly extended and Limitations
supplemented in later years, have shown that many *° selection *
individuals are Heterozygous or cross-bred. These,
though "selected," will not come "true." They break
up into all sorts of new combinations. This is why
eminent men do not usually have sons equal to them-
selves. Some types, such as the "blue" Andalusian
fowl, are incapable of existing except as heterozygotes,
and no process of selection will cause them to have more
than half their offspring " blue." The other half will be
blacks and speckled whites. Furthermore, selection
cannot eliminate the recessives, — those determiners
which may be present in the germ plasm of cross-bred
individuals without producing any effect. Morgan, in
working with flies, has found a number of "lethal"
factors, which when received from both parents are
134
ZOOLOGY
fatal to existence. The individuals homozygous for
them never develop at all. No selection could be more
rigorous than this, yet these factors have not been
eliminated from the stream of inheritance. They sur-
vive in the heterozygotes.
The con- 8. It also appears that although individuals are
determiners different, the determiners giving rise to them go on from
age to age unaltered. That they never alter is of course
an absurd proposition ; but they are at any rate
extraordinarily constant. "Original variations" modi-
fying the very substance of the reproductive cells are
decidedly rare, instead of occurring all the time, as was
once supposed. The constancy of these elements is
shown hot merely by the experience of breeders, but
also and more convincingly by the record of the rocks.
Fossil remains millions of years old show us that certain
forms of life, though continually subjected to "natural
selection," have remained substantially unchanged.
Even their habits have scarcely altered. Others, of
course, have been greatly modified, but change seems
not to have been obligatory as a consequence of the
selective process.
9. All these considerations appear to weaken the
theory of natural selection as an effective cause of
evolution, but in reality they simply modify our idea
of its manner of operation. Unquestionably some
types are more "plastic" than others, and are more
quickly molded by selective agencies. Those organisms
whose life is very simple, who require "but little here
below," do not quickly change. There is no direction
in which they can readily improve. Bacteria, for ex-
ample, have apparently existed for fifty million years,
without important structural changes. Many species
have developed, adapted to particular modes of life,
Conserva-
tive and
plastic
types
NATURAL SELECTION 135
but the group as a whole has continued to carry on its
lowly functions in its relatively simple way. On the
other hand, the higher forms of life exhibit innumerable
structural modifications, which adapt them to all sorts
of special conditions. The effects of natural selection
are in. proportion to the necessities of the organism, in
relation to the environment. If no change is advan-
tageous, selection itself will destroy all variations, and
hold the creature true to type. Thus it can just as well
prevent evolution as cause it. But when conditions are
changing, or new adaptations permit entrance into new
fields of opportunity, selection is a powerful factor, pro-
vided that the necessary heritable variations occur. In
the absence of such variations there may be no "fittest"
to survive, and the species becomes extinct.
10. Regarding the matter quite broadly, there can Complexity
be no doubt that the beauty and variety of living things
has been brought about through the agency of selection, result of
The rocks are full of fossil types which have perished ;
every species has had to endure the test of fitness. In
a sense, the motive force of evolution has been environ-
mental change, compelling adaptations as the price of.
existence. Without periods of heat and cold, moisture
and dryness, without a world presenting all sorts of
different conditions, evolution could not have taken
place. Man is the outcome of innumerable trials., in-
numerable adjustments. As life has become more
varied, each type has become part of the environment
of others, — as their prey, or their enemy, or as occupy-
ing space they would possess. Thus the complexity of
adjustment has increased by a principle of acceleration
growing out of itself, like progress in human society.
Whichever way we regard the matter, we can only come
back to the great realities. What we see represents the
136 ZOOLOGY
pick of the ages ; for every species existing, thousands
have perished, many before they had become well es-
tablished. Over and over again, success has been won,
only to be lost as times changed, and the old had to give
way to the new.
References
WALLACE, A. R. Darwinism.
CHAPTER EIGHTEEN
ARGUMENTS FOR EVOLUTION
I. IT is one thing to show how evolution might have Obstacles
occurred, and another to demonstrate it as a fact,
Modern naturalists are more nearly unanimous about tog of
the demonstration than the theory. Practically with-
out exception, they agree that the various forms of life
have developed from common ancestors through an
evolutionary process. When it comes to explaining
how this happened, there is plenty of room for differ-
ences of opinion, owing to the complexity of the subject.
There is no single cause, no simple explanation ; and
like the blind men of India who examined an elephant,
scientific workers have magnified the importance of
their particular points of contact. For example, it
appears to be very difficult for the experimentalist to
conceive of processes which cannot be demonstrated in
the laboratory, changes requiring thousands of years.
On the other hand, it is hard for the philosophical
biologist, who sees things in the large, to realize the
importance of little things. He will, as it were, draw
large checks on the bank of Nature, not realizing that
there may be obstacles to getting them cashed. This
error was the prevailing one some years ago, but today •
the tendency is too much in the other direction. In our
very proper zeal for tangible facts, we have lost some of
the breadth of view and power of imagination which are
necessary for scientific progress.
2. Since we agree as to the fact of evolution, we can Uniformity
all join in our search for the evidences of its occurrence.
First of all, we note the extraordinary uniformity which
underlies all the manifestations of life, animal or vege-
table. Protoplasm is everywhere the living substance,
137
138 ZOOLOGY
and the processes of heredity and variation are essen-
tially the same in every case. We can actually reason
from a plant to an animal, as the experimenters of re-
cent years have so frequently shown. Professor Jen-
nings, working with minute Protozoa in ditch water,
can determine facts of the greatest importance for the
understanding of mankind.
Then we have the fact that all life, so far as we know,
comes from preexisting life. How, when, or where life
originated we do not know. It may have had more
than one origin, but in any given case the presumption
that a particular animal or plant did not arise by
"spontaneous generation" is so. strong that we take the
fact for granted. In any event, it is impossible that
any of the higher forms should thus originate.-
Many 3- Not only is there this general uniformity in life
organisms processes, but it is astonishing to note how few are the
tissues kinds of materials, or tissues, of which animals and
plants are constructed. The voluntary muscle fibers
of man, with their fine cross-lines like those on a file,
look like those of a beetle. The nerve tissue, connective
tissue, skin tissue, and so forth are substantially alike
in great numbers of different animals. So again in
plants, we find greenness always due to chlorophyll,
and the building material stiffening the walls of the
cells is cellulose.
Homoiogy Then again, throughout long series of diverse types,
t^ie or&ans-> or working parts made of tissues, correspond
accurately. They are said to exhibit homology. No
one doubts that the eyes of a man, a dog, and a frog
represent the same structures ; although this is not true
of the eyes of an insect or a mollusk. The arms of a
man are homologous with the wings of a bird ; it is an
anatomical error, if a pleasing symbolism, to represent
angels with arms and birdlike wings.
ARGUMENTS FOR EVOLUTION 139
Why should all this uniformity of type exist amongst
so much lesser diversity, except as a result of evolution
from common ancestors ? Agassiz used to say that it
might represent not common descent, but common
origin in the mind of a Creator. One may note the
evolution of pottery in a large museum, and refer the
modifications to their common source in the mind of
man. The idea is a fascinating one, but no modern
naturalist accepts it in place of evolution ; though he
may sometimes ask himself whether there has not been
a creative influence guiding the evolutionary process.
4. We can say of the similarity of structure just de- Remnants of
T, , , . . .... . ancient
scribed that it is at any rate functionally appropriate, structures
Whatever its origin, it serves the purposes of the crea-
tures. There are, however, other similarities which
may not be thus explained. We frequently find vestigial
structures, which not only possess no function, but, as
in the case of the human appendix vermiformis, may be
actually detrimental. A little projection on the in-
wardly folded margin of the human ear appears to repre-
sent the tip of a pointed lobe which existed in an ances-
tor. The horse wrinkles the skin of its neck to drive
away flies, using a muscle which exists in us only as a
very thin and useless layer of tissue. We no longer
cock our ears like a dog or a horse, but remnants of the
-muscles for this purpose remain, and some persons can
use them to a certain extent.
5. Still more astonishing is the evidence from embry- oidcharac-
ology. The human embryo, long before birth, exhibits 181
structures on the side of the neck corresponding to the embryo
gill slits of early vertebrates. They are inexplicable
except on the view that a remote ancestor was aquatic.
The slits divide the gill arches, and it is from one of
these that the lower jaw develops. Embryologists be-
140 ZOOLOGY
lieve that had it not been for early aquatic life, we
should not have possessed this useful structure. Man
at birth is tailless, but the early embryo has a distinct
pointed tail. So with many other structures, the prin-
ciple applying to plants as well as animals. These facts
have led to the saying that the ontogeny (individual de-
velopment) repeats the phytogeny (race development or
evolution). This is largely a fact, yet it has been
exaggerated in some quarters, with grotesque results.
It is not necessary, for instance, to assume that a boy
must pass through a stage in which he is a howling
barbarian.
6. Another class of evidence is derived from Paleon-
tology, the study of fossils. Since the earliest known
rocks (Cambrian) which contain well-preserved fossils
show us a highly developed invertebrate fauna, it is im-
possible to trace the origin of the major invertebrate
groups. In the case of the vertebrates we are more
fortunate, and in several instances series of forms have
been discovered, illustrating evolutionary progress.
For an account of two of the best of these, see the
chapter (pages 417 and 425) on the horse and the ele-
phant. The geological record, in spite of the large col-
lections obtained, remains extremely fragmentary.
Thus, although we know the later (Tertiary) history of
the mammals fairly well, their much longer Mesozoic
evolution is represented only by the most meager frag-
ments. There are innumerable "missing links" in all
groups, and we can never hope to complete the history
of life from fossil remains. At the same time, all we
know accords with the theory of evolution, and every
fresh discovery in some measure illustrates it. It must
not be supposed that the several phyla have steadily
progressed from lower (less complex) to higher (more
ARGUMENTS FOR EVOLUTION \\\
complex) throughout the ages. On the contrary, after
an exuberant development in certain lines, it has often
happened that some relatively primitive and insig-
nificant type has given rise to the group destined to be
dominant long after. This is so true, that we are accus-
tomed to think of highly specialized types as ends of the
branches of the tree of life, giving rise to nothing be-
yond. For example, though amphibians were derived
from fisjies, it was not from the highest fishes, such as
the perch. or sole, which have gone far beyond the point
where it would be possible for them to develop any
amphibian features. The paleontologist, convinced of
the truth of evolution, is greedy for every fragment of
evidence he can glean from the past. It is as though
some great book had been broken up, and the leaves
scattered far and wide. He knows that many of the
leaves must have been destroyed, others are lost and will
never be found ; but every page, every line, which he
can recover conveys part of the message of the book.
7. The study of geographical distribution is also very Distribution
suggestive. If evolution has taken place, members of a
group having a relatively recent common ancestor might idea of
be expected to occupy the same continent or hemisphere.
This is what we find in a number of cases ; for example,
the humming birds, with hundreds of species, are all
American. There seems to be no climatic or other
reason why humming birds should not flourish in the
Old World tropics, but they have never been able to get
there. A series of islands forming an archipelago will
often have a series of birds, mice, reptiles, or snails,
each island with its particular sorts. As Darwin noted
in the case of the Galapagos Islands, the nearness of the
islands, and the shallowness of the sea between them,
correspond in a marked degree with the degree of re-
142 ZOOLOGY
semblance between the native products. It is an ob-
vious suggestion that some of the islands were more
recently connected than others, and that evolution has
been going on since they became separated. Such
theories are beautifully illustrated by the animals of the
Hawaiian Islands, and especially the remarkable snails
(Achatinellida) characteristic of the group.
The exceptions to the principles just cited are quite
numerous, but they can often be explained, and it is
presumed that only our ignorance prevents the explana-
tion of all. For example, the llama of South America
belongs to the Camelidae or camel family. That it
should exist so far away from its relatives, the camels,
seems quite anomalous, and contrary to the idea of
descent from a common ancestor. The explanation is
found in the presence of great numbers of camel fossils
in North America ; the camel group once extended all
over the western hemisphere, as well as over Asia, but
has now left only remnants at the ends of its range.
The opossum, a marsupial, is far removed from its
marsupial relatives in Australia; but we know that
marsupials once existed in every continent and in great
variety. The development of the higher mammals
crowded them to the wall, and they now survive in a
very small part of their former territory.
Changes in 8. Darwin was influenced by the well-known fact
piantsfunder that many domesticated animals and cultivated plants
the com- have changed greatly under the influence of man. The
paratively 11111. i • 11 i
brief in- race horse and the dahlia, the pig and the plum, are no
fluenceof longer what they were a few centuries ago. Man has
chosen what he wanted from among the variations
afforded by Nature, and has preserved and propagated
many beautiful and useful types. He has, when the
fancy took him, developed the grotesque or even
man
ARGUMENTS FOR EVOLUTION 143
hideous, and has saved among dogs and goldfish what
Nature would surely have rejected. Some of the do-
mesticated and cultivated varieties are so distinct that
did we not know their origin, they might pass for new
species, if not new genera. If man's selections, com-
bined no doubt with more or less crossing in most
groups, could produce such marked results within a
short time, what might Nature do in millions of years ?
In later years, Professor de Vries of Holland has called
attention to the phenomena of mutation, whereby a
species of plant, such as Lamarck's evening primrose,
may give rise to a series of distinct types which will
breed true. We do not call these species, because we
know their origin, yet some of them are as distinct as
admitted species, and if found isolated would be re-
garded as such.
CHAPTER NINETEEN
THE HISTORY OF LIFE
Absolute I. IT is well known that life has existed on the earth
and relative f many millions of years. The evidence for this is
age of fossils f. 11111.
found in the fossil remains scattered through the sedi-
mentary rocks. The relative age of nearly all the rock
formations is known, since they have been found in
various, places one upon the other. Thus if in one
locality B is above A, we know that it is later, except in
the case of a complete overturn, which can occur only
in a limited area. At another place we find B with a
third formation C above it, though A may here be
absent. We have, then, A, B, C, in proper sequence.
Somewhere else D will be found over C, and so on, until
we are able to construct a geological column, such as
may be found in textbooks. Of course all the forma-
tions cannot be found actually forming such a column,
if only because each new deposit is necessarily made up
of materials derived from older ones. The absolute
age of the rocks is very much more difficult to deter-
mine, but some estimates have been made from the
consideration of various factors, such as the probable
rates of deposition and denudation, and the changes
taking place (at approximately known rates) in radio-
active minerals.
Type fossils 2. The correctness of the method just described
necessarily depends on our ability to recognize various
formations when we find them. How are we to know
that the B which lies beneath C is the same B which
elsewhere rested above A ? It is not likely to be con-
tinuous from one place to the other. The character
of the rock itself is no certain guide ; rocks of entirely
different periods may present the same appearance and
144
THE HISTORY OF LIFE
146 ZOOLOGY
contain the same elements. The only decisive criterion
is the presence of characteristic fossils. Thus the fossils
enable us to recognize the formations, and the relative
positions of the formations in turn give us relative dates
for the fossils. What do we mean by characteristic
fossils ? Experience shows that throughout all the ages
life has been changing. The various geological levels
have their representative remains. The length of time
a family, genus, or species may last varies greatly ac-
cording to the type concerned ; but whenever we can
get an assemblage of species, the geological date becomes
relatively exact. In a city, the names of a hundred
persons present at a meeting would usually define the
date within a year, although some of them might have
lived there fifty years. The same principle applies to
the fossils, though of course we are dealing with very
large units of time.
Relative 3. There are two qualities which make particular
geologist of groups of fossils especially useful to the geologist. One
different [s t}ie likelihood of being preserved. Thus marine shells
groups :>f ....... • 11 •
animals living in shallow water are especially important, since
the shells are readily fossilized and exist in situations
where they are likely to be covered by mud or sand and
preserved. Consequently we find such shells in very
many formations, and can compare the sets one with
another. At the other extreme are butterflies, of which
fewer than 25 species are known fossil, and none of these
in more than one place. It is impossible, from such
scanty remains, to form any exact idea of the changes
in butterfly structure from age to age. The other valu-
able quality is that of showing relatively rapid modifica-
tion. Thus the mammals have changed conspicuously
during periods which have witnessed very little change
in various types of trees. Other organisms are even
THE HISTORY OF LIFE 147
more constant than the trees. Not only this, but the
mammals have progressed along definite lines, so that
the different members of the horse group, for example,
form a sequence which is readily appreciated. Given the
key to this development, — increase in size, reduction
in the number of toes, and so forth, — any one having
the fossils before him .could arrange them in the proper
order. The oysters, on the other hand, have, as it were,
shuffled their characteristics, producing a multitude of
species without any distinct advance. Consequently,
though the species of oysters are extremely useful for
the recognition of geological horizons, the student could
not arrange them correctly except by knowing whence
they came.
4. The science of fossils is called "paleontology," Paieon-
literally, the science of that which is old. Paleozoology ^the^*
has to do with fossil animals, paleobotany or paleophy- science of
tology with fossil plants. The student of these subjects
is a paleontologist, though we also hear such strange
expressions as " fossil botanist." Since fossils are of
such fundamental importance for geology, paleontology
has long been associated with that science as a division,
and is so treated in textbooks. It is, however, obviously
part of the study of life, and now that evolution is made
the cornerstone of biology, the whole subject acquires
new importance. To study the life of today and ignore
that of the past is as unprofitable as to study a country
or city without taking any account of its history.
5. Dr. Charles Schuchert of Yale University has The geologic
published a "Geologic Time Table" which, though not '
pretending to exactness, represents the most expert
consideration of the available evidence. The time rep-
resented since the beginning of the Cambrian, where
we first meet with satisfactory fossils, may have been
GEOLOGIC TIME TABLE (Adapted, with alterations, from Schuchert and Barrell, American
Journal of Science, 1914)
ERAS
MAJOR DIVISIONS
PERIODS
EPOCHS
ADVANCES IN LIFE
DOMINANT
FORMS OF
LIFE
MODERN*
Recent
(Alluvial or
Post-Glacial)
Rise of
Civilization
Age of Man
CENOZOIC
(probably 3 to
4 million
years)
Quaternary
Glacial
Pleistocene
Extinction of many
Great Mammals
Age of modern
Mammals
and great de-
velopment of
Herbaceous
Plants
Tertiary
Late Tertiary
Pliocene
Evolution of Man
Miocene
Culmination of Mammals
Early
Tertiary
Oligocene
Rise of Higher Mammals
Eocene
Vanishing of
Archaic Mammals
MESOZOIC
(probably at
least 9 mil-
lion years)
Late Mesozoic
Cretaceous
Lance
Extinction of
Great Reptiles
Age of
Reptiles
Montanian
Coloradian
Extreme specialization
of Reptiles
Comanchian
Rise of higher Flowering
Plants
Early Mesozoic
Jurassic
Rise of Birds and
Flying Reptiles
Triassic
Rise of Dinosaurs
PALEOZOIC
(probably at
least 1 8 mil-
lion years)
Late Paleozoic
Permian
Rise of Land Vertebrates
and Ammonites
Diversification of Insects
Age of
Amphibians
Pennsylvanian
Rise of Primitive
Reptiles and Insects t
Mississippian
Tennesseian
Rise of Ancient Sharks
Rise of Echinoderms
Waverlian
Middle Paleozoic
Devonian
Rise of Amphibians
First known land plants
Age of
Fishes
Silurian
Rise of Lung-fishes
and Scorpions
.Early Paleozoic
Ordovician
Cincinnatian
Land Plants?
Corals, Armored Fishes
Nautilus
Age of Higher
Invertebrates
Champlainian
Canadian
Ozarkian
Cambrian
Croixian
Shelled Animals
Dominance of Trilobites
First Marine Plants
LATE
PROTEROZOIC
Algonkian
Keweenawan
Animikian
Huronian
Age of
Primitive
Marine
Invertebrates.
Fossils almost
unknown
Oldest Known Fossils
EARLY
PROTEROZOIC
Neo-Laurentian
Sudburian
ARCHEOZOIC
Paleo-Laurentian
Kewatin
Fossils
unknown.
Unicellular
plants and
animals are
believed to
have existed
The
Unrecoverable Be
ginning of Eajrth History
* The modern era, called by Schuchert and Barrell Psychozoic, is not a true era comparable with the
others, but ought in all reason to be considered part of the Cenozoic.
t The insects are so well developed in the Pennsylvanian, that their actual origin must be much earlier.
I48
THE HISTORY OF LIFE 149
from 30 to 50 million years. The tendency is to in-
crease rather than decrease the estimate. It is quite
certain, however, that life existed for an immense period
prior to the Cambrian, though only very inadequate
remains have been discovered. The deficiency of fos-
sils in the earlier (Algonkian) deposits may be largely
due to the unsuitability of primitive types for preserva-
tion ; but more especially to the fact (as it seems to be)
that the early life existed in the sea, and the old shore
lines are now buried beneath the oceans or far below
the surface of the earth. Although great masses of
Algonkian rock have been studied, they appear to repre-
sent old land and fresh-water surfaces, where only very
primitive forms of plant life existed. These include
algae (water weeds of low type) and minute objects con-
sidered to be bacteria. Somewhere, some day, some
happy naturalist will perhaps discover an old Algonkian
shore deposit, with well-preserved animals much older
than any now known.
6. Fpr our knowledge of Cambrian life we are espe- Life in
cially indebted to Dr. Charles D. Walcott of the Smith-
sonian Institution. Cambria is the old name of Wales,
where the Cambrian rocks were first described by the
English geologist, Adam Sedgwick ; but we now know
them from many different regions. The most remark-
able deposit of fossils was found by Dr. Walcott on the
mountain side above Field, in the Canadian Rockies.
Fragments picked up near the base of Mount Wapta
indicated that somewhere on the slope fossils would
be found in place. Following this clew, a quarry was
made at an altitude of 8000 feet above sea level, and
after the surface rock had been blasted out, a wonder-
ful series of remains was obtained. So perfect is the
preservation, that even such delicate objects as jelly-
1 50 ZOOLOGY
fish have left recognizable impressions. There are
many marine invertebrates, including highly organized
Crustacea of numerous kinds, but no vertebrates of any
kind, and none of the higher plants. Worms were
numerous, and some of them possessed remarkable
characters, — leglike appendages, bristles, or spines.
Appearance J. After some millions of years a vertebrate fauna
^ " appeared, — still aquatic, but apparently living in fresh
waters. Singular armored forms are found, apparently
the ancestors of the fishes. Their exceedingly fragmen-
tary remains occur in Colorado and Wyoming, in rocks
of Ordovician age. The Cambrian and Ordovician con-
stitute the early Paleozoic. In the Middle Paleozoic (Si-
lurian and Devonian rocks) 'great changes are observed.
The fishes now become abundant ; land plants and
arthropods (scorpions) appear. Finally, vertebrates
become adapted to a partly terrestrial life, and am-
phibians are developed. We now come to the Late
Paleozoic, often called Carboniferous, — that is, coal-
bearing. It is divided into Mississippian, P.ennsyl-
vanian, and Permian, all periods of long duration. In
the Pennsylvanian the great forests and masses of vege-
tation gave rise to anthracite coal, but flowering plants
were absent. Land vertebrates were becoming numer-
ous, and insects swarmed everywhere. The earliest
insects were some of them of immense size ; one found in
France was about 2 feet 4 inches from wing tip to wing
tip. These lasted for a long time, but in middle Penn-
sylvanian they died out, and the country was overrun
with cockroaches, almost to the exclusion of other in-
sect types. In the Permian, however, the land surface
in North America was elevated, the climate became
cooler, many new families of smaller insects developed,
and the cockroaches diminished greatly in numbers and
THE HISTORY OF LIFE
importance. Here we come to the end of the Paleozoic,
or period of the old life, as we choose to call it. In
From Proceedings U. S. National Museum
FIG. 26. Wing of fossil cockroach (Phoberoblatta reticulata) from the Carboniferous
(Pennsylvanian) rocks near Brookville, Pennsylvania. Magnified about two
diameters.
reality it was the young life, the youth of the world, and
we are the real veterans.
8. The Mesozoic (middle life) period is called the age The age of
of reptiles. It may have lasted about nine million years,
certainly not more than half the length of the Paleozoic.
It begins with the Triassic and ends with the Creta-
ceous, — the latter name from creta, chalk, because it is
the period of the chalk cliffs of Albion. Early in the
reptiles
152
ZOOLOGY
Advent of
warm-
blooded
animals
Flowering
plants
Mesozoic those strange reptiles known as dinosaurs
became prominent, and this type continued to develop,
producing carnivorous and herbivorous species, many
of them of immense size. One of the best-known dino-
saurs is the Diplodocus, of which a skeleton may be seen
in the museum at Pittsburgh. The tail and neck are
both very long, and the head is so small as to be incon-
spicuous. Many dinosaur skeletons are exhibited in
the American Museum in New York and in the National
Museum at Washington. Some were protected by mas-
sive bony armor plates, crests, or spines. All, however,
had small brains, and they must have been stupid ani-
mals. For millions of years they flourished, but finally
died out completely at the end of the Mesozoic. What
destroyed them, we do not know ; they may have been
short of food, or perhaps the mammals learned to eat
their eggs, which they did not know how to protect.
9. While the dinosaurs were rulers of the earth, many
important events were taking place. Warm-blooded
creatures evolved from reptilian types, one series devel-
oping wings and becoming birds, the other retaining
the four walking legs and giving rise to the mammals.
The early birds, like their reptilian ancestors, were
toothed. Of the first mammals we know little ; but
they were small, and are believed to have laid eggs,
like the Australian duckbill of the present time.
Another event of scarcely less importance was the
appearance of flowering plants, and with them of types
of insects adapted for visiting flowers. The latter
appear to have come in principally with the development
of herbaceous vegetation at the end of the Mesozoic and
during the Cenozoic. The first flowering plants were
woody, and were mostly, if not wholly, pollinated
through the agency of the wind, or at any rate without
THE HISTORY OF LIFE
153
Photograph from Am. Mus. Natural History
FIG. 27. Brontosaurus (or Apatosaurus), one of the dinosaurs, a gigantic Mesozoic
reptile, as restored by C. R. Knight under the direction of Professor Osborn at the
American Museum of Natural History, New York.
the assistance of bees or butterflies. Owing to the
change in the flora, the landscape during the Cretaceous
Photograph from Am. Mus. Natural Mistory
FiQ. 28. Skeleton of Brontosaurus, with human skeleton for comparison.
must have been very different from that of the early
Mesozoic. In the Cretaceous, the plants and most of
the invertebrates, could we see them alive today, would
154
ZOOLOGY
The age of
mammals
Photograph from Am. Mua. Natural History
FIG. 29. Skeleton of Hcspcrornis, a Mesozoic bird.
look familiar; but the vertebrate life would appear
wholly strange.
10. Following the Cretaceous is the Cenozoic, more
often called Tertiary, — the age of mammals. This
occupied three or four millions of years only, but it
saw the development of the strictly modern fauna and
flora. The mammals, which had remained insignificant
and apparently not very numerous. for millions of years,
got a new start. Before very long they produced such
an array of new types that we wonder where these could
have been developing. Undoubtedly, both in the case
of the mammals early in the Tertiary and the flowering
plants in the Mesozoic, the apparently sudden -exuber-
ance of development must be partly illusory. Prepa-
rations for these brilliant displays on the stages of
Europe and America must have been going on behind
the scenes, — that is to say, in parts of the world
whence we have no fossils of the periods concerned.
Some day new light will be thrown on these matters,
— perhaps in the far north, or in that great Antarctic
continent which, though now covered with ice, once
supported luxuriant vegetation.
THE H-ISTORY OF LIFE
155
Photograph from Am. Mus. Natural History
FIG. 30. Skeleton of Patriofelis ferox, Marsh. A large carnivorous creodont mam-
mal from the lower Tertiary (Bridger Eocene) of western North America.
Photograph from Am. Mus. Natural History
FIG. 31. Patriofelis ferox, as restored by C. R. Knight. The creodonts, in later
periods, gave place to the modern carnivores, the very numerous creodont genera
becoming extinct.
II. In some respects the Miocene divisions of the The
Tertiary, say about a million years ago, saw the culmi-
nation of life in the northern hemisphere. The climate
156 ZOOLOGY-
was mild, and the number of species of plants and ani-
mals existing was immense. The flora had become
varied enough to permit innumerable adaptive modifi-
cations in the insect world, — species living on particu-
lar parts of particular plants. Life had flowed into
almost every channel of opportunity. Then at the end
of the Tertiary, during a relatively short period which
we separate as the Quaternary, came a succession of
glacial epochs, covering- the northern regions with ice.
The consequent impoverishment of the biota has not
been wholly recovered from to this day. Nevertheless,
in the presence of hard times, and doubtless partly in
consequence of them, man developed. Here was a
being who could in a measure defy nature ; who could
up to a certain point create his own environment and
consequently take possession of the earth. The age
of man ought to be regarded as part of the Tertiary,
but this egotistical creature must needs set it apart,
recognizing a grand division of geological time since
he arrived.
References
WALCOTT, C. D. "Evidences of Primitive Life." Smithsonian Report for
SCHUCHERT, CHARLES. " Paleogeography of North America." Bulletin
Geological Society of America, Vol. 20, 1910.
SCHUCHERT, CHARLES, and BARRELL, JOSEPH. "A Revised Geologic Time
Table for North America." American Journal of Science, July, 1914.
MATTHEW, W. D. "Climate and Evolution." Annals New York Academy
of Science. Vol. XXIV. 1915.
OSBORN, H. F. The Age of Mammals. The Macmillan Company. 1910.
MATTHEW, W. D. " Dinosaurs." Handbook of American Museum of Natural
History. New York, 1915.
CHAPTER TWENTY
THE FLORISSANT SHALES OF COLORADO
1. NEAR the western base of Pike's Peak, almost TheFioris-
under the shadow of that great mountain, lies the santVaUey
Florissant Valley. It is an upland region, over 8000
feet above the level of the sea, with grassy meadows
and rocky slopes, and granite hills all around. Super-
ficially it resembles many of the smaller so-called parks
of Colorado, and there is little about it to attract atten-
tion. It is, nevertheless, one of the classic localities
of the world, known to geologists and paleontologists
everywhere, mentioned in all geological textbooks, —
though, like a prophet in his own country, unheard of
by most of the people of Colorado. Here may be found
preserved the life of a million years ago : leaves and
flowers, butterflies and beetles, in many cases almost
as perfect as when alive, so that the most minute struc-
tures can be seen with the aid of a microscope.
2. During the Miocene Period, long before the ap- The ancient
pearance of man in the world, there was a large lake,
shaped rather like the letter L, at what is now Florissant.
In those days it is probable that the elevation was
less than 8000 feet ; possibly much less, since we know
that the Rocky Mountains have been steadily rising
during the last few millions of years. Whether they are
still going up, we cannot tell, as any slight difference
from year to year would be too small for us to measure,
in the absence of any visible stationary point for com-
parison. The climate was moister and warmer, more
like that of the Southern states today, but not tropical.
This we know from the character of the vegetation.
Around the lake were active volcanoes, which sometimes
threw out very finely divided ash, sometimes liquid
158 ZOOLOGY
The mud or lava. At times of eruption there were, no
volcanoes doubt, violent gusts of wind and poisonous gases, while
hot cinders fell here and there and set fire to the forests.
Thus leaves and even branches were torn from the trees,
and charcoal may still be found to testify to the forest
fires. Insects and other creatures were killed, and fell
into the shallow water of the lake, where they were
presently covered by deposits of the finest ash, falling
gently from above. Thus the various remains were hid-
den beneath successive layers of volcanic material, and
when a mass of lava flowed over the whole, its weight
pressed the wet ash down, and in course of time con-
verted it into hard shale. What had been the life of
the locality, now crushed flat, was hermetically sealed
between the layers, to be uncovered in about a million
years by creatures of a kind not then in existence.
Little could the stray butterfly, perishing miserably,
realize that some day its remains would be placed in a
museum, where they would be the wonder and admira-
tion of many generations of men !
HOW the 3. In the course of ages the volcanoes ceased their
iccur activities, and movements of the earth drained the lake.
The climate became much cooler and drier, and the
fauna and flora changed accordingly. Whatever de-
scendants of the old Florissant plants and animals might
exist mostly migrated to quite other parts of the country,
though some doubtless still live in Colorado. For ex-
ample, the narrow-leafed cottonwood of the foothill
gulches is so similar to that common in the Florissant
shales, that we can hardly doubt that the former has
been derived from the latter. Streams running through
the valley bottom cut into the soft shale, and enormous
quantities of it were carried away to the rivers of the
plains and perhaps even to the sea. What precious
THE FLORISSANT SHALES OF COLORADO
'59
Photograph from American Museum Journal
FIG. 32. Fossil flower (Parana cocker etti, Knowlton") from the Miocene shales of
Florissant. Enlarged.
fossils were thus destroyed, we can never know, but
the amount of fossiliferous material still remaining is
very great. At various places along the Asides of the
valley the shale is either exposed, or is readily reached
by digging. On the surface it is usually weathered and
spoiled ; but by digging a trench good shale may often
be found, and when carefully split by hitting the edge
with a knife, it will show broad surfaces which may or
may not reveal fossil remains. Collecting fossils in this
way is laborious and often disappointing, but some-
times a single stroke of the butcher knife shows a speci-
men which carries back the history of some group of
plants or animals a million years. After many days
of work, the collections always prove to contain species
new to science, and there are few localities which yield
such good returns.
i6o
ZOOLOGY
4. When the various fossils have been assembled
together and studied, many interesting facts appear.
We learn that the distribution of living things today is
From American Naturalist
FIG. 33. Fossils from Florissant. Above, a fossil oak leaf, Quercus ramaleyi, and
next to it a living representative, Qiiercus fendleri, which grows today in Colorado.
Below, a wing of an extinct dragon fly, Phenacokstes mirandiis. Enlarged.
THE FLORISSANT SHALES OF COLORADO l6l
in many respects very unlike that of the past. In the Themigra-
shale are remains of redwood trees ; and there are even extermina-
great redwood trunks, now completely silicified, stand- tionof
ing at Florissant. Today the redwood, once widely
spread over the northern hemisphere, is making its
last stand, confined to a rather small area in California.
In the shale is also the Ailanthus or Tree of Heaven,
a genus now confined to eastern Asia. We find in addi-
tion leaves of magnolia, elm, beech, chestnut, poplars,
pines, and oaks, — such an assemblage as does not exist
in the Rocky Mountains today. We are reminded
rather of the mixed hardwood forests of the Eastern and
Southern states. We wonder why some of these trees
have disappeared from Colorado ; why there are no
longer any elms or chestnuts native in the region, though
they still exist in the Eastern states. Was it the change
of climate, or did some blight sweep them off, like the
chestnut blight which is now so destructive along the
Atlantic seaboard ? There were figs and walnuts, -
we have fruit of both ; wine grapes and holly, roses of
four different kinds, and many other plants dear to the
eye or lips of man ; but there were no men to see or use
them. These things must seem strange to those who
imagine that the beauty and wealth of nature exists for
us alone !
5. In Africa are found certain blood-sucking flies The fossil
which carry the. parasites of disease to men and animals.
These are the tsetse flies (Glossina), and one of them is
the bearer of the cause of sleeping sickness, which has
wiped whole villages of people off the map. Another
makes it almost impossible to keep cattle in certain
localities. Many remarkable animals which once
lived in North America are now extinct, and it is often
very difficult to imagine the cause of their disappear-
162
ZOOLOGY
Geography
of ancient
times
Photograph from Am. Mus. Natural History
FIG. 34. Tipula madurei, a crane-fly fossil in the Miocene shales of Florissant,
showing the details of the markings of body and wings, as they appeared in life.
Enlarged.
ance. Among suggested causes, disease often appears
probable, and if insects existed which would be likely
to carry the parasites of epidemic diseases, the probabil-
ity is increased. It was therefore very interesting to
discover, several years ago, a fossil tsetse fly in the Floris-
sant shales. Since then others have been found, so that
today we know four species of fossil Glossina from this
locality. They may have been the cause of the extinc-
tion of some of the Miocene animals, but why did they
themselves finally disappear, remaining only to plague
the men and beasts of Africa ? To this question we
have as yet no answer.
6. The Florissant fossils may throw light on events
happening in very different parts of the world. During
Tertiary time there was a long period when the present
Isthmus of Panama was under water. We know this
from the marine fossils found in cutting the canal, and
THE FLORISSANT SHALES OF COLORADO. 163
from the close resemblance between the marine fishes of
the Atlantic and Pacific coasts at the present time.
Also during Tertiary time was a period when what is
now Bering Strait was dry land, and animals were able
to cross from Asia to America, and vice versa. What
can these remote happenings have to do with Floris-
sant ? When Bering Strait was passable, there was a
migration of Old World animals into North America ;
we call it the Miocene migration. So again, later than
this, the Panama region was elevated and South Ameri-
can forms were able to pass into Central and North
America. With the first invasion came, for instance,
the elephant group ; with the second, the sloths. Now,
so far as we can judge, Florissant shows very distinct
evidence of the beginnings of the first invasion, but
none of the second. If we are right in this, it follows
that the Florissant shale was laid down in the interval
between the arrival during the Miocene of Asiatic ani-
mals, and that later on of South American ones. By
putting together various bits of evidence of this sort,
we may eventually obtain a relatively exact chronology
of the various deposits, and therefore types of life, which
are represented in the country. The actual number
of years represented is of course uncertain, but the
order in which the events occurred, and the nature of the
geographical and climatic changes, may be revealed
to us. Thus apparently insignificant fossils, which at
first seem to possess no general interest, may be the in-
dicators of the acts into which the great drama of the
earth is divided.
References
Popular Science Monthly, August, 1908, 'page 112; American Museum
Journal, November, 1916, page 443.
CHAPTER TWENTY-ONE
CAROLUS LINN^US
Great men
and their
environment
i. THERE are some
who maintain that
great men are purely
the product of their en-
vironment; that they
are made by opportu-
nity, and always arise
out of a normal popu-
lation to meet a need.
Biology lends no sup-
port to such opinions ;
nor does history, which
abounds with situa-
tions in which disaster
resulted from incapac-
ity. On the other
hand, both biology and
history show that ca-
pacity is sterile without opportunity, that the meeting
ground of these factors is the place where significant
progress arises. So it happened to Linnaeus, that being
a genius, he came into the world at a time when it was
possible to apply his powers to fundamental reforms in
natural history. In the eighteenth century, under-
neath a great deal of superficial slowness and stupidity,
the ideas which we still regard as modern were develop-
ing and coming to the surface. Their expression was
often crude, as in the political and social excesses of the
French Revolution, the educational fantasies of Rous-
seau. The liberators of America, with their doctrine of
the equality of men, were in some respects ill-informed,
164
CAROLUS LINNAEUS 165
were experimenting with materials they did not fully
understand, but they were none the less prophets
of the dawn. History has much to say about all
these movements, but takes little note of the corre-
sponding unrest in purely intellectual fields, where
changes no less significant for the future were taking
place.
2. Carolus Linnaeus, also known as Carl von Linne, Boyhood of
was born at Stenbrohult, in Sweden, on May 23, 1707.
His father was a country pastor, who had an orchard
and a garden. Carl grew up in the midst of flowers,
and early developed that love of nature, of the beauty
and variety of the out-of-doors, which was the motive
power of his life's activities. His father naturally
wished him to become a pastor, and sent him to a school
at Wexio, where he studied Latin and Hebrew under
Lutheran auspices. Here he appeared to make little
progress, and the school authorities were disposed to
advise his withdrawal. They did not believe it was in
him to make a competent clergyman; he had better
occupy himself with some trade or handicraft. Pastor
Linnaeus accordingly went to Wexio to remove his boy,
full of sorrow for the failure. Here he had occasion to
consult a physician, Dr. Rothmann, who was also a
lecturer in the school. The doctor had taken note of
Carl and was by no means of the opinion that he was
a dullard. True, he would scarcely make a pastor;
but he had scientific instincts, so why not a physician ?
So confident was Dr. Rothmann of Carl's abilities,
that he proposed to take him into his own house for a
year, and instructed him free of charge. The good
doctor, acting out of the kindness of his heart and his
zeal for the promotion of science, had no idea of the
tremendous importance of his act.
1 66
ZOOLOGY
Linnaeus
with Dr.
Stobaeus
Life at
University
of Upsala
3. The year with Dr. Rothmann completed, Carl
proceeded to the University of Lund, where he found
lodging under the roof of Dr. Stobaeus. His new
patron was a man of some consequence, with a collec-
tion of natural history specimens and a valuable library.
The library was so valuable, containing so many rare
and costly books, that it was kept locked ; only Stobaeus
himself and his assistant had access to it. Carl Lin-
naeus, eager for botanical knowledge, persuaded the
assistant to bring him books, on the one -condition
that they should be read during the hours of the night,
when there was no fear of detection. Very early in
the morning they were replaced on the shelves, and the
doctor had no reason to suspect the infringement of
his rules. It so happened, however, that the doctor's
old mother did not sleep well, and from her window she
noted, night after night, a candlelight in the young
man's room. Dr. Stobaeus, suspecting some dissipa-
tion, resolved to find out what this meant, and at two
in the morning softly went to Linnaeus's door, and
opened it. He saw Carl hard at work, the most pre-
cious botanical works from the library spread out be-
fore him ! The doctor, far from being angry, was de-
lighted to witness such zeal, and from that time did
everything in his power to further Linnaeus's studies.
He gave him a key to the library, and begged him to
read by day and take the necessary rest at night.
4. After a year at Lund, Linnaeus wished to go to
the greater University at Upsala, where he had hoped to
find still better opportunities for learning. His parents
consented, but were unable to support him there ; he
would have to work his way through as best he could.
A year had not passed when he found himself almost
penniless, — so poor that he had to line his shoes with
CAROLUS LINNAEUS l6j
birch bark and pasteboard, and his clothes were worse
than shabby. Nevertheless, he continued the study
of botany with enthusiasm, and was once describing
some plants in the botanic garden when an eminent
professor of the University, Celsius by name, passed by.
Celsius questioned Linnaeus, and was so impressed by
his knowledge of plants that he took him into his house
and became his enthusiastic patron. Through this new
influence the poor student became prosperous, and was
even permitted to give lectures on botany, taking the
fees of those who chose to attend. In many European
universities the privat docent system is maintained ;
certain men, after due examination, are permitted to
lecture, though not professors. If they are successful,
they may have very large classes, and receive more in
fees than the salary of a regular member of the faculty.
So it happened with Linnaeus, that he drew students
from the established department of botany, and it
seemed as though the tail were about to wag the dog.
This aroused jealousy and indignation, and a rule was
passed that henceforth no undergraduate should be per-
mitted to give public lectures. This cut off Linnseus's
source of income, but he was now ready for other enter-
prises.
5. The Academy of Sciences at Upsala requested Botanical
Linnaeus to make a journey to Lapland, to collect and " Lapland8
study the products of that country. We have his
narrative, showing the enthusiastic spirit in which he set
forth :
"I journeyed from Upsala town the I2th of May,
1732, which was a Friday, n o'clock A.M., when I was
25 years old, all but twelve hours. Now began all the
ground to delight and smile, now comes beautiful Flora
and sleeps with Phoebus. . . . Now stood forth the
i68
ZOOLOGY
Journey to
Holland
and other
countries
winter rye quarter of an ell tall, and the grain had
newly shown a blade. The birch began now to burst
forth, and all leafy trees to show their leaves, except
the elm and aspen. . . . The lark sang to us the
whole way, quivering in the air. . . . The sky was
clear and warm, the west wind cooled with a pleasant
breeze, and a dark hue from the west began to cover the
sky. . . . The woods began to increase more and
more, the sweet lark which ere now had delighted our
ears, deserted us, but yet another one meets us in the
woods -with as great a compliment, namely the thrush,
Turdus minor, who, when she on the highest fir-top
plays to her dearest, also lets us joy therein. Yes, she
tunes in so high with her varied notes that she often over-
masters the nightingale, the master of song."
In the autumn he returned, after a journey of about
2500 miles, mostly on foot and alone. The Flora
Lapponica, published later, gave an account of the
plants he found. One of these was the delicate and
beautiful twinflower, which afterwards came to bear
his name and was called Linncea borealis. It was the
wish of Linnaeus that he should be commemorated by
some lowly and humble plant of his own northern coun-
try, rather than by a gorgeous product of the tropics.
6. Linnaeus now turned to teaching, and later to
medicine, as a means of earning his living. After a
time he made a journey to the principal countries of
Europe — to England and France, Germany, and Hol-
land, — in order to visit the botanical establishments
and meet the botanists. Many stories are told of what
he saw and did on this eventful journey. At Leyden in
Holland there lived a famous old aristocrat named Boer-
haave, equally celebrated in medicine and botany.
Linnaeus, provided with a suitable letter of introduction,
CAROLUS LINN&US 169
called on him every day for a week, but was not ad-
mitted. It was said that Boerhaave had made even
Peter the Great of Russia wait two hours in an ante-
room before seeing him. There seemed no chance for
the young botanist, but it occurred to him to send in a
little book he had published. This pleased Boerhaave,
who at last granted him an interview, and took him into
the garden to see a tree which was supposed to be unde-
scribed. Linnaeus at once recognized it, and told his
learned host where he would find a description ; when
they returned to the house the book was found, and
Boerhaave had to admit that he was right. In such
ways Linnaeus gained the friendship and respect of men
in the countries he visited, and came away with the
beginning of an international reputation.
7. After practicing medicine in Stockholm with Professor
great success, Linnaeus at length became Professor of
Botany at Upsala. This enabled him to devote himself
to biological science, and to the encouragement of those
who were interested in natural history. His influence
was profound, both through his published works and his
personal relationships with students all over the world.
In North and South America, in China and Africa,
wherever explorers could penetrate, Linnaeus had his
friends and disciples, collecting plants and animals for
their beloved master. Some of these helpers are still
remembered in the names of familiar plants ; thus
Peter Kalm sent from North America the beautiful
genus Kalmia, the so-called laurel of our Eastern states.
8. The work of Linnaeus was extensive and varied, The
but we are now concerned only with its principal as- deificati
pects. In the field of botany he devised a system of of plants
classification which was based primarily on the number
and character of pistils and stamens. Those who had
ZOOLOGY
The
Linnaean '
system of
naming
animals and
plants
previously given attention to the structure of flowers
had interested themselves in the conspicuous parts,
the brightly colored petals. Linnaeus realized that the
essential organs were those which produced the ovules
and pollen, the means of reproduction. The new con-
ception justified itself in various ways ; it appeared to
bring together related but superficially dissimilar plants,
and to solve many puzzles. It was also very easy to
understand, and the merest beginner, with the Linnaean
system, could classify plants with fair success. Today
we classify plants on a different basis, not because we
deny the importance of the reproductive parts, but be-
cause we now see that all parts are more or less impor-
tant and must be considered. The idea of evolution
leads us to the conception that there is such a thing as
a natural classification, in which the arrangement is
expressive of actual degrees and kinds of relationship.
This natural classification is an ideal to which we con-
stantly approach, but which we never can expect fully
to realize ; hence botanical (and zoological) arrange-
ments are constantly subject to change, and no simple
method, however convenient, can be accepted. We
have abandoned the beautifully simple and intelligible
Linnaean method for one far more intricate and diffi-
cult, compelled to do so by the change in our scientific
ideals.
9. The other great contribution to scientific reform
made by Linnaeus has to do with names. He was the
founder of modern zoological and botanical nomen-
clature. The language of science was Latin, the names
of animals and plants were Latin, and even those of
men who wrote on these subjects took a Latin form.
Previous authors had the conception of the genus, the
group of kinds or species, to which was given a distinc-
CAROLUS LINNAEUS IJl
tive name, preferably derived from classical sources.
Thus, all violets were Viola, all slugs Limax. To these
designations were added sentences defining the differ-
ent sorts belonging to these genera. Lister, writing
in 1678, called the common large garden slug Limax
cinereus, maximus, striatus et maculatus, which simply
means the large gray streaked and spotted slug. In
Europe any one at all familiar with slugs would at once
recognize the animal, so that the name, if cumbersome,
was sufficiently illuminating. It was a name and de-
scription all in one. At the timie of Linnaeus many new
animals and plants were being discovered and described ;
strange creatures were coming from all parts of the
world, and it was obviously impossible to find a suffi-
ciently illuminating sentence-name to designate each.
The method was too cumbersome and too difficult.
Therefore Linnaeus proposed a new plan, — to retain
the genus-name, and add to it a single other word,
designating the species. The large slug accordingly
became Limax maximus ; the sweet violet, Viola
odorata;- the horse, Equus caballus ; and mankind him-
self, Homo sapiens (sapiens •, wise or knowing). But if
the sentence were no longer sufficient to indicate the
species clearly, how should the single word suffice?
It did not, but when it was first published, it was to be
accompanied either by a description or a reference to
some previous author who had given a description or
figure. The validity and meaning of the -name had to
depend on the adequacy of the accompanying data.
At the same time, specimens of the species named were
to be preserved whenever possible, and would be useful
thereafter as evidence. Such specimens we now call
types ) and regard them as among the most precious pos-
sessions of any museum.
172 ZOOLOGY
The species io. The rapid and wide acceptance of the Linnaean
andTthe1"* system of nomenclature was due partly to its inherent
Systema simplicity and convenience, but also to the fact that
Naturx
Linnaeus himself proceeded to apply it to all animals and
plants known in his day. He cataloged the living crea-
tures of the world, so far as they had been recorded or
were represented by obtainable specimens, and to every
species applied a name. In the Species Plantarum of
1753 we find the starting point for botanical nomencla-
ture, while the tenth edition of Systema Naturce, pub-
lished in 1758, gives us the earliest animal names now
entitled to recognition. After the name, for purposes
of reference, we often write the name of the author who
first proposed it. Such author-names, when frequently
'cited, are usually abbreviated, and by common consent
"L." stands for Linnaeus. Consequently, in looking
over any catalog of the animals or plants of a country,
one may see at a glance how many and which were
known in Linnaean days ; they are those the names of
which are followed by the letter "L."
Modification ii. Linnaeus sometimes added a third name, .to desig-
nate the variety. Thus European man was Homo
nomen- sapiens Europ&us. In later times much more interest
clature , , . . . 111 11
has been taken in variations and local races, so that the
use of varietal or subspecific names has become general.
The various complexities thus arising are chiefly of
interest to specialists, whose work demands the con-
sideration of many small matters. Thus Forel, a Swiss
student of ants, described an ant from British Columbia
as Formica rufa obscuripes whymperi. This seems like
a return to the old sentence method, but the meaning
is quite different. Formica rufa is the red ant ; in one
part of its range it is represented by a race or sub-
species which Forel called obscuripes (dull or dusky-
CAROLUS LINNAUS ' 173
legged), and included in this race is a variety or lesser
group, called whymperi after the well-known climber of
mountains who discovered it. Most people, of course,
would be satisfied to call the animal Formica rufa, but
the more intricate investigations of Forel and others
are very important as throwing light on problems of
evolution, and the nomenclature has to meet the re-
quirements of the work.
The question may be asked, how far should the
naming of things go ? Will not science be smothered
by the mass of verbiage ? The answer must be, that
names are only means to the end of designating the
objects with which we are concerned. The question is,
then, how far is it worth while to go in separating out
and distinguishing natural objects ? Every individual
of Homo sapiens has a name, and no inconvenience re-
sults. An infinite intelligence might be able to know
and name every individual insect or bacillus, but the
human mind has its limits. To the scientific man,
however, the question is not so much one of ability to
discriminate, as of ability to derive any general ideas
or broad principles from the analysis. The work which
seems to an outsider hopelessly petty and trivial may
reveal the hidden forces of the universe, or may afford-
means of dealing with the most pressing problems of
mankind. The individual naturalist does not usually
expect to attain any far-reaching results, but he knows
that he is contributing to a structure of knowledge,
which when reasonably complete will begin to yield
fruits of a kind he may only dimly foresee. His faith
is, that the building will be serviceable, and all human
experience goes to justify it.
12. After the death of Linnaeus, writers in all coun-
tries continued to describe "new genera" and "new
174* ZOOLOGY
Synonyms species." These were, of course, new only in the sense
homonyms °f not having been scientifically named before. It
soon appeared that through various misunderstandings,
or mere ignorance of what had been done, the same
animals or plants often received several names. The
rule of priority was accordingly established, and ac-
cording to it the name first given, accompanied by data
for recognition, is the valid or proper name. All others
are synonyms, and have no standing. Names being
of course international, it makes no difference where
or by whom the first name is published, provided it is
in Latinized form (and great latitude is permitted here !)
and conforms to the rules generally. There is one nec-
essary exception to priority, however : it cannot be per-
mitted for two different genera of animals or of plants
to have the same name, nor for two species in the same
genus to be named alike. When names are thus inad-
vertently duplicated, the one latest published is called
a homonym, and it is necessary to propose a substitute
for it.
CHAPTER TWENTY-TWO
THE PRINCIPLES OF CLASSIFICATION
I. WHEN we contemplate the enormous bulk of Necessity
scientific literature, and the multitude of facts dis-
covered and recorded by scientific men, it seems as if
science must eventually be smothered by its own mass.
Yet those who have long engaged in scientific pursuits
know that, on the contrary, it is becoming easier to deal
with the accumulating materials. The secret of this is
classification, the putting in order of our data so that
each item can be found where it belongs. This is not
peculiar to science. Although there are hundreds of
millions of people in the world, a letter mailed in the
Philippine Islands reaches a particular individual in
Colorado, requiring only five words on the envelope in
addition to the name. The reader of these lines has a
name, and presumably lives in a particular house, on
a particular street, in a particular town, situated in a
particular county of a particular state of the United
States. All these things being known and named, that
individual can be found without any difficulty. So it is
with the zoological or botanical classification. The
reader is probably an American, he is a member of the
species Homo sapiens, which is included in genus Homo,
which falls in the family Hominidae, which belongs to
the Mammalia, these in turn being Vertebrata, which
are Animalia or animals.
2. Suppose for a moment that some being from Significance
another world has come here and captured a man. He
is acquainted with zoological methods, and desires to
find out what the strange creature may be. His reason-
ing will be somewhat as follows : Obviously, at the out-
set, this is an animal, not a plant. It has a vertebral
175
i76
ZOOLOGY
Classifica-
tion aims to
express re-
lationship
column, or so-called backbone (really a multitude of
bones) ; so it is a Vertebrate animal. It is warm-
blooded ; so it must be a Mammal or a Bird. There is
hair upon its body, but no trace of feathers ; this is
decisive, it is a mammal. The finger nails and the form
of the teeth suffice to indicate the order Primates ("for
the first shall be last, and the last shall be first"), which
contains man and the monkeys. The large brain and
relatively long legs with flattened soles show that it is
one of the Hominidse, of which the only living genus is
Homo. The creature therefore is a man. The existing
men are all considered to belong to a single species,
Homo sapiens, but there are many races and subspecies.
If the man has pale (so-called "white") skin, and hair
which is not "woolly," he surely belongs to the sub-
species europceus, and is zoologically European, al-
though politically perhaps American. This sounds
cumbersome, but of course in practice the zoologist
takes a short cut to his conclusion. He perceives im-
mediately that the animal before him belongs to a
particular group, and has only to ascertain its position
in that group. If he finds that there is no place for it
in the system, that no description hitherto made fits it,
he calls it "new," and proceeds to describe it and give it
a name.
3. So far, the object has been simply to sort objects
and data 1 so that they can be easily found ; but modern
classification has much more ambitious purposes. It is
nothing less than to express by means of the arrange-
ments the actual "blood" (or "sap") relationship be-
tween organisms. Classification thus aims to reveal
the actual plan of nature, not merely an artificial plan
1 Data is the plural of datum. Those who should know better often use
it as if it were singular.
THE PRINCIPLES OF CLASSIFICATION 177
devised for man's convenience. This is in its entirety
an impossible ideal, yet we continually approximate
more closely to it. The naturalist who understands
this purpose finds even a check list, a bare list of genera
and species, full of meaning and interest, provided it
represents an attempt at classification.
CHAPTER TWENTY-THREE
Dominant
groups of
Abundance
of success-
f ol types
THE PHYLA OF ANIMALS
COULD we assemble together specimens of all the
kinds of animals which have ever existed, the gaps
which separate the phyla, classes, orders, and families
would be filled by what we now call "missing links."
Nevertheless, it would still be possible to distinguish
the larger divisions, since the animals possessing their
special characters would be much more numerous than
the intermediate forms. We may illustrate the facts to
a certain extent by comparison with objects made by
man, which have undergone a kind of evolution, though
by psychical instead of physical reproduction. No one
doubts, for example, that the wheels of a locomotive and
an automobile are alike modified forms of the original
cart wheel. It would be possible to accumulate a col-
lection illustrating numerous intermediate stages ; yet
if all wheels were to pass us in review, the highly adapted
ones would be vastly more numerous than those leading
up to them. As long as the automobile was in a rela-
tively experimental stage, the number of these machines
was comparatively small. As soon as the evolution had
gone far enough to produce a highly serviceable ma-
chine, the number enormously increased. So, then,
with the phyla of animals. The arthropod type, the
vertebrate type, etc., represent successful mechanisms,
which have increased and become diversified because
competent to do so. The "missing links" represent
Nature's experiments, perhaps well suited to particular
times and conditions, but not able to occupy any large
place in the world. A phylum (plural phyla) is the
largest division of the animal kingdom. Most people
think of animals as belonging to two great groups, the
178
THE PHYLA OF ANIMALS 179
vertebrates or backboned animals, and the invertebrates, Vertebrates
without any spinal column. The vertebrates consti- 76
tute a phylum ; but the invertebrates cannot be thus
grouped together, since the various phyla which they
include are as distinct from one another as they are
from the vertebrates. In several important respects a
man is more like an earthworm than the latter is like a
sea anemone.
Since the phyla or grand divisions are so important, Disputed
one would suppose that all naturalists would long ago p ya
have agreed as to their number and limits, if only as a
matter of convenience. This is true in respect to
several, but others are still in dispute. The questions
involved have to do with the amount of difference neces-
sary to establish a phylum. Naturally not all are
equally distinct, and at some point it must be difficult
to say whether a given group should be a phylum or a
class, or whether we should compromise and talk about
a "subphylum." It is assumed, however, that a
phylum must not be "polyphyletic" ; that is, a collec-
tion of unrelated organisms, not derived from any com-
mon ancestor possessing the characters of the phylum.
For this reason the proposal to include the sponges
among the coelenterates appears highly objectionable,
since it is improbable that the two groups have any
common ancestor nearer than the Protozoa, or one-
celled animals.
We may recognize the following phyla, which are
more fully discussed farther on :
Phylum Protozoa (page 1 86)
Animals consisting of single cells, which may however Protozoa
be aggregated together in groups. They are all small, tophyta
and are closely related to the Protophyta or one-celled
i8o
ZOOLOGY
Sponges
Ccelenter-
ates
Echino-
derms
plants. All groups above the Protozoa are classed
together as Metazoa, merely to emphasize the fact that
they are many-celled or compound.
Phylum Porifera (page 207-)
The sponges, in which numerous cells are associated
together to form the individual, and these are special-
ized or modified in various ways.
Phylum Ccdenterata (page 210)
Primitively radially symmetrical animals, such as the
jellyfish and the sea anemone. The Ctenophora, jelly-
fishlike marine animals with eight longitudinal bands
of cilia, constitute a subphylum.
Phylum Echinodermata (page 218)
Secondarily radially symmetrical animals, certainly
more related to the worms, or even to the arthropods,
than to the ccelenterates. They include the starfish,
sea urchin, etc.
Phylum Bryozoa (page 226)
Small marine or fresh-water animals living in colonies.
Phylum Brachiopoda (page 227)
Lamp shells The lamp shells, resembling bivalved mollusks, but
really related more nearly to the worms.
Phylum Platyhelminthes (page 229)
Flatworms, such as the planarian, the liver, fluke and
the tapeworm. The Nemertinea (page 233) may be re-
garded as another phylum, or a class under Platyhel-
minthes.
Phylum Nemathelminthes (page 233)
The roundworms, with cylindrical unsegmented
bodies, such as the hookworm.
Bryozoa
Flatworms
Round-
worms
THE PHYLA OF ANIMALS l8l
Phylum Trochelminthes
Minute aquatic animals related to the worms, con- Rotifers
sisting in the main of the Rotatoria or rotifers (page 235),
but including also the minute fresh-water animals called
Gastrotricha, and equally minute marine Kinorhyncha,
both so rarely observed that it is unnecessary to discuss
them here.
Phylum Phoronidea
Phylum Chatognatha
Phylum Sipunculoidea
These are small groups of marine animals, which can- Small and
not be satisfactorily referred to any of the other phyla.
The sipunculoids, from the nature of their early stages, ful
have been classed with the annelids, but they are not
segmented. Such groups represent Nature's relatively
unsuccessful experiments, which have never developed
and spread as have the dominant phyla. They are
very interesting to the zoologist but of little conse-
quence to the majority of people.
Phylum Annelida (page 237)
The annelid or segmented worms, including the e&rth- Annelid
worms and leeches. In the older classifications all the
worms now separated as Annelida, Platyhelminthes,
and Nemathelminthes were grouped together as Verrnes.
Pratt, in his Manual of the Common Invertebrate Animals
(1916), separates the annelids, but treats all the above
groups from Bryozoa to Sipunculoidea as subphyla of
Vermes. This has the great advantage of avoiding the
recognition of small and relatively unimportant groups
as phyla, but the assemblage is an extremely miscel-
laneous one. It can be roughly defined as consisting of
182
ZOOLOGY
bilaterally symmetrical animals consisting of many
cells, without true segmentation and without any trace
of a notochord, and without the special characters of
the mollusks. The fact is that the' bilaterally sym-
metrical type of animals gave rise to a great many
independent branches, some of which assumed great
importance ; while others, though very distinct in struc-
ture, remained relatively insignificant.
Phylum Arthropoda (page 257)
Arthropods The jointed-footed animals, such as the insects, centi-
pedes, crabs, spiders, etc.
Phylum Mollusca (page 243)
Mollusks The mollusks, including snails, slugs, clams, cuttle-
fish, etc. Although mollusks, annelids, and bryozoans
are so different in appearance when adult, they show
curious resemblances in the early stages.
Phylum Prochordata (page 320)
The forms which, while lacking a vertebral column,
nevertheless breathe by means of gill slits, and have at
least in some stages a more or less developed notochord.
A miscellaneous group, unsatisfactory because its divi-
sions are so little related to one another. It is sometimes
included with the vertebrates as a phylum Chordata.
Phylum Vertebrata (page 328)
Vertebrates The vertebrates ; fishes, reptiles, amphibians, birds,
and mammals, including man. The relationship be-
tween the various phyla may be roughly indicated as
follows, the most primitive types being placed lowest in
the diagram :
Prochor-
dates
THE PHYLA OF ANIMALS
183
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I 84 ZOOLOGY
Another way to regard the animals is from the stand-
point of the mode of life. Assuming that the first life
was aquatic, we can construct the following scheme,
again beginning at the bottom (see diagram, page 185).
Adaptation This diagram illustrates what Professor H. F. Osborn
calls "adaptive radiation," the tendency for life to
occupy all favorable situations, becoming modified to
suit the environment. It will be noted, however, that
there are limitations ; not all groups occupy all environ-
ments.
THE PHYLA OF ANIMALS
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CHAPTER TWENTY-FOUR
PROTOZOA
Characters i. Protozoa are usually defined as the simplest ani-
mals, consisting of only a single cell. Some forms, how-
ever, are said to be "colonial," existing in regular and
well-defined groups of numerous individuals or cells.
Thus the common fresh-water Anthophysa consists of
pear-shaped flagellate cells united in compact clusters,
often attached to a stalk. The slime molds or Myce-
tozoa form sporangia which are composed of many cells
and have the appearance of fungi. Even in these cases,
however, we do not find the development of tissues con-
sisting of specialized cells, such as exist in other groups
of animals. As if to make up for this lack of specializa-
tion, the single protozoan cell is often a remarkably
complex structure, having many recognizable parts, or
secreting an elaborately constructed shell. The Pro-
tozoa are readily distinguished from other animals if
attention is paid to their characters, though the smaller
worms may be confused with them on superficial ex-
amination. The latter, if examined more closely, will
be seen to have various complex internal organs wholly
lacking in Protozoa. When we look in another direc-
tion and try to separate the Protozoa from the Proto-
phyta or lowest plants, the task becomes much more
difficult. Indeed, many groups are claimed both by the
botanists and the zoologists. It might seem easy to
refer the green Euglena to the plants, since it possesses
chlorophyll, the characteristic coloring matter of green
plants. It is found, however, that very closely related
animals lack the green. There is another group which
makes a shell of cellulose, which is also a typical plant
product ; but in other respects the organisms resemble
186
PROTOZOA 187
Protozoa. We are obliged to confess that there is no
perfectly valid distinction between the lowest animals
and the lowest plants ; they grade one into the other.
2. Protozoa abound in the sea and in fresh waters ; Variety and
they occur also in damp soil, while vast numbers of of protozoa
species are parasitic. The Mycetozoa may be regarded
as Protozoa adapted to life in air. The species of Pro-
tozoa are excessively numerous, and in some cases they
appear almost indefinitely so. The marine Radiolaria,
described by Professor Haeckel of Jena, construct elabo-
rate and beautiful shells of almost every conceivable
pattern, reminding us of the infinite variety of snow
crystals. The thousands of "species" named all have
characteristic forms, but more recent researches indi-
cate that many can be grouped as phases of variable
species. Even so, however, the number of distinct
kinds is very great, and the same may be said of another
marine group, the Foraminifera. It is a remarkable
fact that in spite of the low type of organization and the
multitude of species, the different types of Protozoa are
on the whole extraordinarily constant and of great an-
tiquity. The very same species may be found in fresh
waters on continents and islands, in the tropics and in
cool countries, at sea level and in the mountains. Con-
sequently the student who believes he has a new Proto-
zoan is obliged to consider in comparison the species of
the whole World, for the animal he has discovered in
New York may have been described from, Tasmania.
3. The principal types of Protozoa may be classified Flagellates
in groups or subphyla by the use. of a few simple char-
acters. The Mastigophora or flagellates move by means
of a slender, undulating or vibratile thread of proto-
plasm called the ftagellum (little whip). In certain
types there are two or even more of these flagella, and
i88
ZOOLOGY
some of these show a distinct approach to the bacteria
or other lowly organized plants. One of the commonest
cSr. B
x^x
Drawing by R. Weber, after Leidy
FIG. 36. A , Amiba diffluens. B, Amiba radiosa. Greatly magnified, n, nucleus;
c.v., contractile vacuole; p.p., pseudopodia. The contractile vacuoles are excretory
organs. They become filled with waste fluids and gases, which they eventually pour
out on the surface of the body, contracting as they do so. Thus they possess, in a
very simple form, functions of the lungs and kidneys of higher animals. They differ
in function from the lungs in not being connected with the absorption of oxygen,
which is taken in through the surface of the body.
flagellates in ponds and ditches is the elongated green
Euglena viridis. In this animal one may notice a red
Drawing by W. P. Bay
FlG. 37. Amiba, magnified about 500 diameters, cv, contractile vacuole ; ^nu-
cleus; ec, ectoplasm; en, endoplasm. The endoplasm contains diatoms and other
minute plants taken in as food and food masses in various stages of digestion and
assimilation.
PROTOZOA
I89
"eye spot," which probably enables the creature to dis-
tinguish differences in illumination, though it is quite
unable to see any distinct object. In its simplest form
the eye is a spot or area of coloring matter, which is
changed by light and stimulates the living protoplasm.
One of the marine flagellates is occasionally so abundant
off the coast of California as to color the sea red, and to
kill many fishes and other animals by clogging their
gills. The Noctiluca is a relatively large flagellate,
quite visible to the naked eye, which floats in the ocean
near the surface, and when disturbed produces a bril-
liant light, so that the wake of an ocean steamer at night
is often resplendent as though with fireworks. Other
flagellates, such as the Trypanosoma, are parasitic within
the bodies of animals.
4. The Mycetozoa, often regarded as plants, arise from Slime molds
a firm-walled spore, which in water gives birth to a
swarm cell. These swarm cells are produced in great
numbers, and are flagellate, resembling the Masti-
gophora. They swim about, feeding on bacteria. After
Drawing by R. Weber
FIG. 38. Sporangia of Mycetozoa (after Lister). A, Sporangium of Didymium, on
a fragment of a leaf ; much magnified. B, Compound sporangium, or aethalium, of
Spumaria, on grass; about twice natural size. C, Group of sporangia of Trichia,
on wood ; about four times natural size.
190
ZOOLOGY
Parasitic
Protozoa
a time they coalesce to form a slimy wandering mass,
the plasmodium; and this, now living in the air, usually
on logs, forms a definite structure of characteristic ap-
pearance, which produces spores. The fructifying stage
usually incloses the spores, and is called a sporangium,
but in one group it has the spores on the outer surface
and is termed a sporophore. Some sporangia are very
large, that of Reticularia lycoperdon (lycoperdon, a puff-
ball, which it resembles) is often 4 or 5 inches across.
The plasmodium or slime stage is a multinucleate mass
of protoplasm resulting from the union of a large num-
ber of cells, and as it grows the nuclei greatly increase
in number. It feeds on dead plant tissue.
5. The Sporozoa (spore animals) are parasitic Pro-
tozoa, without cilia, but in certain genera producing
sexual forms, the male (sperm) cells then often flagel-
late. Reproduction is typically by spore formation
(compare the Mycetozoa), the individual breaking up to
c
Drawing by R. Weber
FIG. 39. Stages in the development of Didymium, one of the Mycetozoa (after
Lister) ; magnified about 1400 diameters. A, Spore. B, Swarm cell escaping from
a spore case. C, Swarm cell; /, flagellum.
PROTOZOA
191
give rise to a great number of smaller organisms. In
the malaria parasite, which is conveyed to man by the
Drawing by R. Weber (after Leidy)
FIG. 40. Shells of three species of Difflugia. A, D. capreolata. B, D. corona.
C, D. acuminata, variety inflata. Although Difflugia corona presents marked
variations, it never assifmes the form of D. acuminata or D. capreolata. Distinctive
characters are not confined to the shell; one species (D. rubescens) has the contained
animal of a beautiful brick-red color. Greatly magnified.
mosquito, sexual reproduction occurs in the body of the
insect, but asexual sporulation takes place in the human
blood.
Gregarines are sporozoans usually found in the ali-
mentary canal of insects and other arthropods. One
common species lives in the earthworm.
6. The Rhizopoda include many of the most common The Amiba
fresh-water Protozoa, which possess neither flagella nor
cilia, but move slowly about by means of projections of
the body, called pseudopodia (singular, pseudopodium)
or false feet. The Amiba (or Amceb.a) is a naked form
common in ponds.1 When at rest it is spherical, but its
protoplasm flows outward to form elongated pseudo-
podia. Within the body can be seen nucleus and con-
1 This animal was originally called Proteus, on account of its changing
form, but it was found that the name had previously been used for another
animal. Amiba was then substituted, with the spelling here given, though
it is more usual to write Amoeba.
192
ZOOLOGY
Ciliates or
Infusoria
tractile vacuole, and also frequently various objects taken
in as food. Many other rhizopods form shells of
various kinds, often looking like little jars or flasks, or
flattened and circular, like buttons. In one genus
(Quadrulella) the shell is composed of quadrangular
plates ; in another (Difflugia) it consists principally of
sand grains united together by a secretion of the animal.
In one family the pseudopodia are threadlike.
Related to the Rhizopoda are the Heliozoa or "sun
animalcules," a common representative having a
spherical form and long, raylike pseudopodia, resem-
bling conventional pictures^of the sun. The marine
Radiolaria, already mentioned, are related to the
Heliozoa.
7. The Infusoria move by means of cilia (singular,
cilium), which are very fine eyelash-like projections
from the body, moving like the oars of a boat and caus-
ing the animal to be rapidly propelled through the
water. Reproduction is usually by simple transverse
B
Drawing by R. Weber
FIG. 41 . Types of Protozoa. A , Shell of Lagena (Foraminifera) Marine ; B, Stylo-
cephalus, a gregarine parasitic in beetles; C, Quadruletta, a freshwater Rhizopod.
All much magnified.
PROTOZOA
193
division, but the individuals may frequently be seen to
conjugate \ whereby a certain amount of their proto-
plasmic substance is interchanged. This differs from
Drawing by W. P. Hay
FIG. 42. Paramecium. A, anterior; B, posterior end; m, oral opening; cv1, an-
terior contractile vacuole in contraction ; cv2, posterior contractile vacuole in state
of expansion ; /, food masses ; n1, micronucleus ; ri2, macronucleus. Greatly mag-
nified.
the sexual reproduction of the Sporozoa, and.it can
hardly be said that sex exists, since the conjugating
individuals are alike. In the Suctoria cilia are nearly
always absent in the adult, which possesses tentacles
instead.
Cilia are by no means confined to the Protozoa ; thus
they exist in the human windpipe, where they serve to
remove the accumulations of mucus and dust,
CHAPTER TWENTY-FIVE
PROTOZOA AND HEREDITY
Races of I. THE species of fresh-water Protozoa, widely dis-
Protozoa tributed over the earth, are remarkably constant in
what we call their specific characters. When minutely
studied, however, they are found to vary within rather
wide limits, and it appears that there exist numerous
minor races, too much alike to be recognized as distinct
species. Professor H. S. Jennings of Johns Hopkins
University has shown that the intensive study of these
minute animals will yield results of the highest interest
in connection with the problems of heredity. The
slipper animalcule, Paramecium (plural, Paramecia\ is
a ciliated form extremely common in water containing
decomposing vegetable matter. It is transparent, so
that all its characters can be readily observed, while its
rapid rate of reproduction makes it possible to follow
it through numerous generations. As it does not neces-
sarily conjugate, but is capable of reproducing for very
long periods, if not indefinitely, by simple division, it is
possible to eliminate the confusion due to biparental
inheritance.
Pure lines "Pure lines" can be obtained, all directly descended
from a single ancestor. Such pure lines have members
with identical hereditary composition, although in-
dividuals may show conspicuous differences due to en-
vironmental conditions. Even in a watch glass it is
impossible to make the conditions absolutely uniform.
The lower layers of the water are likely to contain
accumulations of bacteria, which are injurious to the
protozoans. Individuals entering the less favorable
surroundings will have their vitality somewhat im-
paired, and thus they show less energy in swimming to
194
PROTOZOA AND HEREDITY 195
the upper layers. By degrees, just like men, they be-
come regular inhabitants of the slums, and show the
effects of this in their appearance. Consequently Jen-
nings found that even within a pure line the individuals
differed in size, the largest being very much larger than
the smallest. Yet if he selected one of the largest and .
one of the smallest to start new lines, their progeny
varied over the same average under similar conditions.
It made no difference whether the ancestor of the new
group was large or small, because these differences were
not inherited. Similarly, among people, the descend-
ants of an ignorant man, who had never been educated,
would not necessarily show any inferiority to those of
one who had had every advantage.
2. Nevertheless, when various "wild" Paramecia, of Races of
different sizes, were selected to start pure lines, it was
found that there were races differing in average size.
Jennings isolated eight such races. There were also
races differing in various other characters. Each one of
these races varied, owing to environmental effects, but
the ranges of variation were not the same. . Thus one
race might vary from A to D, another from E to E, a
third from C to F. Now the smallest member of one
race might be much smaller than the largest of the next,
yet if the first race averaged largest, its small represen-
tative would give rise to animals averaging larger than
the progeny of the large member of the other race.
Thus the result depends upon the hereditary composi-
tion, of the race, and not upon the appearance of the
individuals. It is often impossible to determine, on mere Effects of
inspection, whether a character is due primarily to heredity JUenf
or environment. Of course all characters are actually vironment
due to the combination of both factors, but one or other
may be responsible for the conspicuous deviation from
I
196 ZOOLOGY
the average. Similarly, among plants, smallness may
be due to growth under unfavorable conditions, such as
lack of moisture ; or may be (as in the case of the dwarf
sweet pea) an inherited character. Among sunflowers,
the seeds of large kinds produce dwarfs when grown in
shade, but no amount of sunshine will make the small
kinds grow tall. Among ourselves, we are continually
puzzled to know whether the qualities of individuals are
primarily inherited, or are principally due to favorable
or unfavorable surroundings. No one, trying to judge
himself, can be quite sure how much to attribute to
each of the two factors. Yet the breeder of animals or
plants, especially if he can keep many successive genera-
tions under observation and experiment at will with
environmental factors, may determine the relations
between cause and effect with a high degree of accuracy.
The experience so gained enables him to form reasonably
accurate judgments in many other cases on mere in-
spection, or with a limited history to guide him.
Constancy 3. Since the selection of large or small (or otherwise
ncrs differing) Paramecia among the members of a pure line
did not produce any change in the characters of the
race, it was held that the hereditary qualities remained
constant during the period of the experiment. Experi-
ments of this sort were continued long enough, not only
with Paramecia but with other organisms, to lead to
the conclusion that actual changes in the germ plasm
(original variations) were extremely rare, to say the
least. This appeared to be equally true of animals, and
plants ; thus the Vilmorin wheats remained the same
after ma-ny years of selection. There remained, how-
ever, this difficulty — that since selection could be
based only on tangible or visible characters, it was
difficult or impossible to choose the deviations due to
PROTOZOA AND HEREDITY 197
heredity (if there were any) , instead of the probably much Expert
larger ones caused by the environment. To avoid this
difficulty Jennings began new experiments with a quite
different protozoan, the Difflugia corona (Fig. 40, B).
This is a shelled rhizopod, the shell being made of grains
of sand embedded in a chitinous secretion, and presenting
a variable number of projecting spines. When division
takes place, to form a new individual, the shell is formed,
and it cannot be altered subsequently. The shells are
readily preserved, so that many successive generations
may be directly compared. It was found that the ani-
mals differed in the size and shape of the shell, the length
and number of the spines, etc. After many generations,
the descendants of a single ancestor, selected for various
characters, were found to have actually diverged from
one another, the difference being inherited. This ap-
pears to contradict flatly the evidence derived from
Paramecium, but it may well be that species differ in
the mutability of their germ plasm, or are mutable at
certain times and not at others. It must be remem-
bered that the species of Difflugia are extremely widely
spread over the world, and are essentially constant in
their characters. This proves that they are of great
antiquity, and suggests that however the hereditary
qualities may have varied, they have very rarely done
more than oscillate about a mean. It may be that the
complex molecules forming the determiners are never
rigidly constant for great lengths of time, but change
within small limits, which usually elude our powers of
observation. This might be true, and yet the chemical
oscillation, if we may so term it, might be strictly
limited under ordinary circumstances, so that the
termination of a series of generations would find the
organism practically as it was at the beginning. Only
198 ZOOLOGY
by the selection and isolation of the minor varieties
could these be established as permanently differing
strains.
References
JENNINGS, H. S. "Heredity, Variation, and the Results of Selection in the
' Uniparental Reproduction of Difflugia Corona." Genetics, September,
1916.
JENNINGS, H. S. "Modifying Factors and Multiple Allelomorphs in Relation
to the Results of Selection." American Naturalist, May, 1917.
SPILLMAN, W. J. "Application of Some of the Principles of Heredity to
Plant Breeding." Bulletin 165, Bureau of Plant Industry, United States
Department of Agriculture.
CHAPTER TWENTY-SIX
PROTOZOA AND DISEASE
I. PARASITISM has arisen independently in various Origin of
groups of Protozoa. It represents an effort on the part Jmong181
of these animals to extend their range, to find new oppor- Pr<>tozoa
tunities for existence. The fluids within the bodies
of animals appear to be especially suitable for proto-
zoan life, but the species which are found as parasites
are not identical with those living free. They have
special characters which fit them not merely for para-
sitic life in general, but for life in a particular kind of
animal, the involuntary host.
We may imagine the evolution of a parasitic proto-
zoan type to have been somewhat as follows. Origi-
nally an inhabitant of the waters surrounding or im-
bibed by the prospective host, it finds its way into the
alimentary canal, where it becomes established and at
the same time modified for the new mode of life. Then,
after a time, it penetrates the walls of the gut, and occu-
pies the blood or some other body fluid, and is now an
obligatory parasite. All this will doubtless take a very
long time, and requires perhaps millions of generations
of the evolving organism. That it should happen at
all is rather surprising, when we consider the extraor-
dinary stability of the free-living species. These latter
have remained true to type in the presence of tropical
heat and arctic snows, and through immense periods of
time.
The parasites have certainly undergone more rapid
change, fitting themselves for life in various hosts, some
of which are themselves of comparatively recent evolu-
tion. Herein they met the necessities of the situation,
showing a power of adaptation where nothing else would
199
200
ZOOLOGY
The
parasitic
ameboid
Protozoa
Filterable
viruses
The
disease-
causing
flagellates
suffice. Even so, however, they departed little, as a
rule, from the primitive protozoan structure, and some
of them would hardly be recognized as parasites if taken
out of their proper environment. The evolution has
been largely physiological, a change in abilities and reac-
tions rather than in outward form or obvious structure.
2. Among the Rhizopods we find ameboid species,
known as Entam&ba, inhabiting the alimentary canal.
One of these types is the cause of dysentery, a disease
especially prevalent and fatal in warm countries. The
cause of rabies or hydrophobia, long in doubt, is now be-
lieved to be an ameboid protozoan, which establishes
itself in the nervous system of the victim. A protozoan
has also been connected with smallpox, while the exist-
ence of other disease-producing, amiba-like organisms is
inferred rather than certainly known. In the case of
yellow fever, for example, the virus or organism cannot
be seen, nor can it be isolated from a liquid by means of
filtration. It belongs to a class of filterable viruses, rec-
ognized only by their effects. The list of such disease-
producing but invisible creatures is being increased as
new observations are made, and from the close analogy
between their effects and those due to Protozoa we infer
that they probably belong to this group. Possibly some
day microscopical technique will be improved suffi-
ciently to enable us to see and study the structure of
these infinitesimal beings, but at present it appears im-
possible to combine an image sufficiently large for vision
with adequate illumination.
3. The flagellate Protozoa or Mastigophora include
the genus Trypanosoma, which is the cause of some of
the most serious diseases known. Trypanosomes are
long, pointed animals, with an undulating membrane
along the side, the margin of which extends as a flagel-
PROTOZOA AND DISEASE 2OI
lum from one end. Species of trypanosomes occur fre-
quently in the blood of various animals, without neces-
sarily giving rise to any
ill effects. Others are
extremely dangerous, one
producing the disease
called " sleeping sickness "
in man, another the na- Drawing by ^eber (after
gana disease Of domestic ^ Wellcome Research Laboratories) .
animals in Africa. The FlG' «' Trypanosome of camel, greatly
magnified.
Ciliata or ciliate Protozoa
are usually thought of as free living, but even these in-
clude parasites, such for example as the Opalina, com-
mon in -the frog. This is an oval species, capable of
being extended to look like a worm. The most charac- The
teristic parasitic Protozoa are, however, the Sporozoa, or sP°rozoa
"spore animals," which have neither cilia nor flagella,
and reproduce mainly by the formation of spores, or
small particles arising in great numbers at one time from
the parent. Here we include a division called Hemo-
sporidia, living in blood, members of which cause malaria,
tick fever, and apparently Rocky Mountain spotted
fever.
4. It is not difficult to understand how the organism Alternate
of dysentery, which occupies the alimentary canal, can parasitic
be acquired through drinking infected water. In tropi- Protozoa
cal countries the prudent traveler boils all his water, or
uses distilled water. But what about the malaria para-
site, found in the blood, or that of sleeping sickness, also
inhabiting the internal fluids ? Can these animals, in
the course of one or a few generations, pass into the ali-
mentary canal, and thence into the blood ? The sup-
posed course of evolution is not thus repeated, nor does
it appear that the origin of parasitism in these types
202
ZOOLOGY
Economic
results from
study of
Protozoa
was necessarily in the bodies of warm-blooded animals
at all. They are parasites of Arthropods, which are con-
veyed to mammals and other animals when the insects
or arachnids suck their blood. Thus the parasites have
alternate hosts, belonging to very different classes of
animals, both of which must be present for the comple-
tion of the entire cycle of normal activities. It is note-
worthy in this connection that the alimentary canals of
many Arthropods, such as insects and centipedes, are
inhabited by Gregarines, a group of Sporozoa which
.have nothing to do with disease in higher animals. We
may infer, though we can never prove, that millions of
years ago, in Carboniferous times, the great cockroaches
then so abundant were infested by these parasites, at a
time when no warm-blooded animals had evolved. We
do not know how it first came about that alternation be-
tween a vertebrate and an invertebrate host was estab-
lished, or by what means a parasite was able to accom-
modate itself to the strange environment of warm
blood. We do know, however, that this happened more
than once ; for trypanosomes and malaria parasites are
little related, and certainly evolved from quite different
branches of the great protozoan stem.
5. With the establishment of the theory of alternate
hosts, a great new field of preventive medicine was
opened up. It would be difficult to exaggerate the value
of the various discoveries which have given us knowl-
edge of the course and mode of transmission of yellow
fever, malaria, sleeping sickness, and other diseases.
Through them the most fertile regions of the world are
opened up to the white man ; and while innumerable
deaths are prevented, our food supply is increased enor-
mously. We have only begun, as yet, to take advantage
of the offerings of science in this direction ; but it is
PROTOZOA AND DISEASE 203
within the memory of all mature persons that the region
of the Panama Canal, once a hotbed of pestilence, has
been made healthful. In the course of the investiga-
tions leading up to these results, many men have suf-
fered illness or even death, but this does not deter medi-
cal investigators from taking risks which they, better
than any others, understand. At an early stage in the Yellow fever
investigation of the transmission of yellow fever in Cuba,
Dr. J. W. Lazear of the United States Army lost his
life; but this did not prevent his colleagues, Reed,
Carroll, and Agramonte, from continuing the work,
until they had proved conclusively that this disease is
brought about only through the bite of a particular type
of mosquito, known as Stegomyia. The mosquito does not
itself cause the disease, but conveys the organism which
produces it. With this information it was easy to un-
derstand why yellow fever never became permanently
established in the North, for Stegomyia lives only in
warm temperature and tropical regions. It was also
possible to see the futility of a great deal of disinfection
work which had formerly been regarded as the most
important means of protection. A man may sleep in a
bed which has just harbored a yellow-fever patient, and
suffer no evil consequences. More especially, however,
it was possible to get rid of the disease by destroying the
breeding places of the mosquitoes, the whole yellow-fever
problem being thus rendered comparatively simple and
easy of solution. There is no longer any excuse for
the prevalence of yellow fever in a community.
6. In the case of malaria (ague or swamp fever) it was Malaria
also found that mosquitoes were to blame, but this time
an entirely different kind, belonging to the genus Ano-
pheles. The causative organism of malaria, called Plas-
modium, is readily visible under the compound micro-
204 ZOOLOGY
scope, and can be traced without difficulty in both
its hosts. Long ago people connected malaria with
swamps, — the word itself, from the Italian, meaning
"bad air," which was supposed to rise at night from the
stagnant waters. We now know that Anopheles breeds
in the swamps, and flies at night; it is the swarm of
mosquitoes, which arise and bite whoever may be acces-
sible, that bring about the disease. The malaria organ-
ism has a double life-cycle, reproducing sexually in the
body of the mosquito and asexually in the blood of man.
Thus we must regard the mosquito as the primary host,
or the more important of the two from the standpoint of
the parasite. At the time of reproduction or sporula-
tion in the blood, the affected individual suffers a "chill,"
followed by fever, which occurs at regular intervals while
the active phase of the disease lasts. There are several
types of malaria, and at least three different species of
parasites have been distinguished, — all, however, car-
ried by Anopheles. The proof of the connection be-
tween mosquitoes and malaria was established not only
by the observation of the organisms in the blood, but
also by the experimental transmission of the disease. It
was also shown experimentally that men could live and
work in the most malarious districts, and suffer no harm,
provided they were protected from mosquitoes at night.
In localities where there is no Anopheles, malaria cannot
be acquired, though persons who have acquired it else-
where may continue to suffer at intervals. Anopheles
may even be present, but unless it is infected by the
Plasmodium, no malaria results.
Sleeping 7. The important African diseases due to trypano-
andnagana somes are also carried by insects, but of a different
family of Diptera or flies. In this case the alternate
hosts are species of tsetse fly, of the genus Glossina.
PROTOZOA AND DISEASE
205
These look somewhat like house flies, but are recognized
by the long, straight proboscis projecting in front of the
head, and by the way in which the wings are folded over
From drawing by John T. Scott
FIG. 44. Tsetse fly (Glossina palpalis), female; X 5 diameters. From a speci-
men collected in Southern Nigeria, Africa, by G. Garden, April 28, 1909. This
fly is widely distributed over tropical Africa. It has a formidable proboscis, and
sucks the blood of man and other animals. In so doing, it transmits a minute
protozoan, called Trypanosoma gambiense, which produces in man and monkeys
the disease known as " sleeping sickness." From this disease many thousands of
the inhabitants of Africa have perished. Another related protozoan, Trypanosoma
brucei, is carried by a different tsetse fly, Glossina morsitans, and produces in cattle
and horses the highly fatal disease called "nagana." Tsetse flies once existed in
Colorado, as is proved by fossils found at Florissant. They may well have trans-
mitted the organisms causing disease, and thus been instrumental in extermi-
nating some of the larger animals. Thus we find here, as throughout the realm
of animate nature, that all living things are actors in the great drama of exist-
ence, and those which seem at first to have the most insignificant parts often
prove able to influence an ever widening circle of events. Man and his affairs can-
not be understood without reference to the humblest forms of life.
206 ZOOLOGY
the back, the ends not projecting as they do in ordinary
flies. Glossina palpalis is the principal transmitter of
sleeping sickness, or rather of the protozoan which
causes it. Through the extension of commerce in tropi-
cal Africa the disease has been enormously extended, and
has destroyed the lives of untold thousands of native
people. The sickness is of long duration, and eventually
the victims sleep to death. Another tsetse fly, Glossina
morsitans, carries the trypanosome of nagana disease,
which makes it impossible to keep cattle in some dis-
tricts. It is found that the large wild animals of Africa
harbor the parasite, without suffering any serious conse-
quences ; hence they serve as a reservoir. from which the
tsetse flies may always renew the supply. At Floris-
sant, in Colorado, several species of fossil tsetse flies
have been found, and it is surmised that at one time
these may have been carriers of the organisms of dis-
ease. Today there are no species of Glossina living in
the Western Hemisphere.
Tick fever 8. Other disease-producing Protozoa, belonging to
the genus Babesia, are carried by ticks. One of these
gives rise to a fatal affection of cattle, in which the red
blood corpuscles are broken up. In the Southern states
cattle have acquired a tolerance of this parasite, just as
in tropical countries the negroes are relatively tolerant
of malaria. When such cattle, infested by ticks, are
driven northward, the ticks may leave them and bite
Northern cattle, which then succumb to the disease.
The cause of Rocky Mountain spotted fever, a disease
which is very fatal to men in certain districts, is also
carried by ticks, but of a different species from those
living on cattle. Fortunately the disease is at present
rare and local, though the ticks are widespread.
CHAPTER TWENTY-SEVEN
SPONGES
i. THE Sponges or Porifera (pore-bearing) constitute
a very distinct phylum of animals, little related to any
characters
of sponges
Drawing by W. P. Hay
FIG. 45. A simple sponge attached to a seaweed. On the right the same animal
is shown in vertical section.
others. They are all aquatic, the great majority being General
marine. They have existed in great abundance for
many millions of years, as is proved by their fossil re-
mains. The genera and species are very numerous, and
of very diverse structure and appearance ; yet all are
sponges, and there has apparently been no tendency to
evolve into anything higher. There is a similar lack of Mode of life
progressive tendencies in the life of the individual
sponge. The ovum or egg cell is fertilized by a minute
flagellated sperm-cell, as in the higher animals. The
fertilized cell becomes a ciliated larva, which swims
about for a time and then becomes fixed to some object
and develops into a sponge. There is a veritable meta-
morphosis, the creature becoming entirely changed, and
207
208
ZOOLOGY
finally we have, in typical cases, a structure resembling a
hollow vase perforated with holes. The central cavity
has an opening above called
the osculum (little mouth),
while the walls are perfo-
rated by pores. During life
water enters by the pores
and passes out through the
osculum. The inner cavity
is lined with peculiar flagel-
lated cells, the base of each
flagellum being surrounded
by a little cup or collar.
The whiplike movements of
the flagella cause the neces-
sary flow of water. Thus
the sponge, beginning life as
a free-living larva, as if on
the way to produce a rela-
tively high type of animal,
assumes a vegetative form,
and appears almost to lose
its integrity as an individual.
The cells of which it is com-
posed are less definitely asso-
ciated together than those of
the higher animals, so that
the distinction between a
sponge and an aggregate type
of protozoan is not so radical
From "Animate Creation" as might at first appear. In
FIG. 46- Skeleton of Euplectella as- the Sponge, however, the Cells
pergillum, or Venus-cup sponge, com- 11 • -i • i
posed of flinty fibers; about | natural are nOt a11 Similar, either in
size. form or function.
SPONGES 209
2. Sponges are said to possess a skeleton, but the term The sponge
is employed in a very loose sense. We mean that there
are fibers or spicules which give the structure its stiffness
and prevent it from falling to pieces even when all the
living material has been removed. In an ordinary bath
sponge we see this skeleton, consisting of a horny sub-
stance called spongin, which in life is merely the frame-
work of the animal. One group of sponges has a skele-
ton made of calcareous or limy spicules, while others
have the spicules siliceous or flinty. This property of
secreting different materials, limy or flinty according to
the species, is found also in Protozoa. The hornlike
substance, spongin, is said to be allied to silk. The
spicules resemble little crystals in form, and it is charac-
teristic of the relatively unorganized and vegetable-like
growth of the sponge that these units are scattered
through the substance, instead of being articulated to
form a definite mechanical unit comparable to the skele-
ton of a vertebrate. It must be said, however, that the
structure of the whole animal is often complicated and
beautiful, especially in the flinty forms.
There is no special nervous system, and therefore the
actions of the cells are largely independent of one an-
other, as though they were distinct individuals. It is
well to remember in this connection that even in our-
selves, with our brain and highly organized nervous
system, the white blood cells behave essentially as in-
dependent units.
CHAPTER TWENTY-EIGHT
Protozoa
and
Metazoa
Endoderm
and
ectoderm
CCELENTERATA
1. ANIMALS are divided into the Protozoa and Meta-
zoa. The Protozoa, as we have seen, consist of single
cells, or of aggregations of similar cells. The Metazoa
are the multicellular or many-celled organisms, includ-
ing, of course, all the higher forms. If we set aside the
sponges as representing a quite distinct line of develop-
ment, we may recognize in the typical Metazoa certain
characteristics common to the whole series, apparently
indicating evolution from a single stem. The ccelen-
terate, such as the jellyfish or hydra, is essentially a sac
with two layers of cells, of which the inner is called the
endoderm and the outer the ectoderm. The terms
"hypoblast" and "epiblast" are used by authors in the
same sense. Now these layers may be seen in the early
stages of the highest animals, and in development they
form definite structures. Thus the inner layer gives
rise to the various parts connected with the alimentary
canal, but from the outer is developed the nervous sys-
tem. A middle layer, becoming distinctly defined in the
higher groups, produces the skeleton of the vertebrate
and other important structures. This middle layer
(mesoderm or mesoblast) is not present in the ccelente-
rates, though materials derived from the two primary
layers form a poorly organized mesoglcea lying between
them.
Thus it appears that the basic structure of the higher
animals was laid down in the lower Metazoa ; and what
was then developed, millions of years ago, conditions the
development of man himself today.
2. On the other hand, the ccelenterates lack very
important structures. They possess a single internal
210
C(ELENTERATA 211
cavity, serving as a stomach and having a single orifice. Relative
They have therefore the form of a vase or bottle, and to of^oeiente
that extent resemble the sponges, though the resem- ratestruc-
blance is wholly superficial and represents no commu-
nity of function or descent. In the other Metazoa, be-
ginning with the echinoderms and worms, there appears
a second body cavity, the ccelom, between the intestine,
or stomach, and the body wall. In their vaselike form
with a single cavity, the ccelenterates thus stand at the
base of the metazoan series, and in a sense we may say
that a jellyfish is less like a sea urchin than the latter is
like a man.
When we have once grasped the essential features of
the ccelenterate structure, it is not difficult to detect
them in the most diverse members of the group. As the
position of the animal differs according to the species, or
even in the same species at different periods of life, we
do not speak of the upper and lower surfaces, but of the
oral and aboral sides. The oral side is that which ex- The oral
hibits the mouth opening, and -the aboral that opposite
to it. Thus in a sea anemone the upper side is oral, and
the mouth is directed upward. In a jellyfish the lower
side is oral, and the upper corresponds to the base of the
sea anemone.
3. The ccelenterates possess radial symmetry, in the Radial sym-
manner of a flower. This early attracted the attention r
of naturalists ; hence the name "sea anemone," and the
scientific term Anthozoa (flower animals), applied to the
great group including the sea anemones and most of
the coral animals. Others form plantlike colonies, and
were in some cases originally described as seaweeds.
Such are termed zoophytes, the name meaning in Greek
" animal plants." The radial symmetry of the ccelente-
rate is said to be primitive, whereas that of the echino-
212
ZOOLOGY
Two modes
of repro-
duction
derms (such as the sea urchin) is secondary or derived,
— a response to the needs of sedentary life. These
Drawing by R. Weber
FlG. 47. Diagram illustrating the radial symmetry of a starfish (Echinodermata) ,
A ; and a medusa (Ccdenterata), B.
facts. are determined from a study of the early stages,
but it is also to be noted that the radial segmentation of a
jellyfish is fundamentally different from that of an echi-
noderm. In the echinoderms, as A. H. Clark pointed
out, the divisions are lines of weakness ; hence the typi-
cally five-rayed condition, which provides that no such
line will go straight across the body. In the jellyfish
the divisions are marked by lines of greater strength, and
hence when continued across the body give added rigid-
ity. We therefore find quadripartite ccelenterates.
4. The primitive character of the ccelenterates is
shown also by their modes of reproduction. They pos-
sess sex, but also reproduce by budding. Individuals
are produced as lateral buds, which live for a time as
parasites attached to the parent, and finally become de-
tached and independent. This is a natural process, but
a fresh-water Hydra may be cut up into a number of
pieces, and each one will grow into a perfect individual.
In certain groups the asexual mode of reproduction is
lost, and there are separate sexes as in higher animals.
In the fresh-water Hydra the male and female genera-
tive cells may be produced by the same individual, when
CCELENTERATA
213
it is said to be a hermaphrodite. When the animals are
well fed, they usually show female characters.
""'*"%,
Drawing by W. P. Hay
FIG. 48. A hydra (Hydra oligactis), with two buds, a and b ; m, mouth ; /, tentacles
with batteries of nematocysts ; enlarged about 5 diameters.
5. The ccelenterates are divided into three great Divisions of
groups, the Hydrozoa or Hydromedusae, the Scyphozoa Ccel
or Scyphomedusae, and the Anthozoa. The first con-
tains the hydroid zoophytes, hydra and other less-known
animals ; the second the true medusae1 or jellyfishes ; the
third the sea anemones and their relatives. Nearly all
these animals are marine, but Hydra is a common fresh-
214
ZOOLOGY
water animal; and a few kinds of small fresh-water
medusoids (Hydrozoa) are known. Great excitement
was caused, many years ago, by the discovery of the first
of these medusoids in the water-lily tank in the Botanic
Garden in Regent's Park, London.
iiydrozoa The Hydrozoa are remarkable for the branching
colonies of many of the species. This type of structure
may be thought of as due to a budding process, — the
buds, as in a plant, remaining attached, with nourish-
ment flowing from one to the other. It results from
this that specialization is possible, and we find the indi-
viduals or persons of the colony taking on different func-
tions. Some feed, others reproduce, while others have
stinging properties and serve for defense. On examin-
stat
Drawing by W. P. Hay (after Nutting)
FIG. 49. A, a small portion of a colony of Obelia commissuralis, one of the Hy-
drozoa, common on American coasts, hy, hydranth in a hydrotheca; gon, a gon-
gangium containing young medusa. B, a medusa; stat, statolith; greatly enlarged.
COELENTERATA 21$
ing a branching hydroid, one may often see small, cup-
like structures attached to the stem. These are the
hydrothecce, and in them are set the hydroid persons,
more or less resembling minute hydras. The reproduc-
tive persons may remain permanently attached to the
colony, or, in other species, they are set free as swim-
ming medusae, whereby the range of the species is ex-
tended. The word medusa, as applied to a jellyfish or The me-
similar animal, is derived from the Medusa of ancient
fable, a woman with snakes for hair. The naturalists
of early times, who had a good deal of imagination,
fancied a resemblance between the head of the medusa
and the jellyfish, with its snakelike pendent tentacles.
When the reproductive person or medusoid is set free,
the base becomes the upper surface and the oral side is
below. These medusoids have been found and studied
by naturalists in many cases without reference to the
hydroid stage ; consequently two systems of classifica-
tion have sprung up for stages of the same animals. By
degrees, however, the connection between particular
colonial forms and their medusoids is being established,
and the classifications are amended accordingly.
Certain medusoids possess small vesicles at the mar-
gin of the bell or umbrella, and these vesicles contain
statolithsj — hard, stony bodies which are supposed to
enable the animals to perceive their position in space.
The force of gravity, acting on the statoliths, produces a
downward pressure to which the animal reacts. Thus
the function of these organs is something like that of the
semicircular canals in the human ear, but in these latter
the mechanism is entirely different. Nature attains the
same or similar ends in wholly diverse ways.
The Scyphozoa are not very closely allied to the Hy- Scyphozoa,
drozoa, and it is even probable that they acquired the fishes
2l6 ZOOLOGY
medusa form independently. Some of them are of great
size, the disk or umbrella as much as 4 feet in diameter.
One specimen was found to weigh 90 pounds, but
of course this was mainly water. Large jellyfishes cast
up on sandy shores form only thin films when dried by
the sun.
The sea 6. The typical anthozoan, as represented by the sea
and™*16 anemone, is a more or less columnar animal, with the
relatives upper end furnished with numerous tentacles, which
serve for catching the prey. In the middle of the upper
surface is seen the mouth opening, which is usually more
or less oval or slitlike, giving the animal an incipient
bilateral symmetry. The mouth is the upper end
of the throat or stomodceum, the lower end of which
really corresponds to the mouth of the hydra. The
stomach cavity is not a simple sac, as in the hydroids,
but is invaded by a series of leaflike projections from
the sides, called the mesenteries. In the coral-forming
species the septa of the coral alternate with the mesen-
teries, and hence it is possible to determine to a con-
siderable extent what form the soft parts had in fossil
corals of vast antiquity. The Alcyonaria (Fig. 9, page
39) constitute a peculiar subclass of Anthozoa, in which
the individuals possess eight pinnate or featherlike ten-
tacles. All produce a limy so-called skeleton, and the
various remarkable colonial forms, as seen after the death
of the animals, resemble columns of basalt or other cu-
rious structures, little suggestive of anything living. It
is only by the careful study of the living creatures that
we can perceive their agreement with the ccelenterate
plan of organization.
Coral 7- Coral reefs, produced by Anthozoa living in vast
groups, are of great interest and importance to geog-
raphers and geologists. Innumerable islands of the
CCELENTERATA 21 7
Pacific Ocean are composed wholly of coral, and the
great barrier reef of Australia is also coralline. Many
rocks consist of fossil coral ; thus a fossil coral reef may
be seen at Beulah, New Mexico, now 8000 feet above the
level of the sea. Charles Darwin, during the voyage of Darwin's
the Beagle, studied the formation of coral reefs, and con- obseryations
eluded that the circular coral islands represented vol-
canic peaks or masses of rock which had disappeared
beneath the waves, leaving the surrounding coral to
grow upward in circular form. The coral animals do
.best where the surf breaks on them, the water being
abundantly supplied with oxygen, and hence they tend
to grow most on the outer side of the reef. Were the
reef to subside suddenly, the animals would perish ; but
the subsidence has been so slow that they have kept pace
with it, building always on the skeletons of their ances-
tors. The wash of the waves has piled up masses of
dead coral, with the result of forming a beach a little
above sea level, on which coconut palms and other vege-
tation may grow. Professor W. M. Davis of Harvard
University recently visited the South Seas to study this
matter afresh, and was able to confirm Darwin's theory.
It must be said, however, that there are various kinds of
reefs, and some of them are largely due to lime-secret-
ing algae or seaweeds.
CHAPTER TWENTY-NINE
Origin and
characters
of Echino-
dermata
ECHINODERMATA
I. THE origin of the Echinodermata is problematical,
but they are certainly much less primitive than the
Ccelenterata. The larva is more or less wormlike or
curiously branched, with a distinct bilateral symmetry.
There seems to be a certain relationship with the Cirri-
pedia or barnacles, and therefore with the Arthropoda.
However this may be, the phylum is one of the most dis-
tinct and easily recognized, though its different members
are very diverse. They inhabit the sea, although one of
the wormlike sea cucumbers (Synapta) may be found in
brackish water in mangrove swamps. The adult ani-
mals are usually recognizable by their radial symmetry,
with a calcareous outer skeleton ; internally we find a
complete alimentary -canal, with two openings, and a
body cavity between this and the outer wall. The nerv-
ous system is closely connected with the skin, and there
Drawing by W. P. Hay
FIG. 50. Common starfish (Asterias) of Atlantic Coast. A, upper or aboral sur-
face ; B, lower or oral surface ; C, cross-section of one of the arms ; D, diagram of
the water- vascular system ; m, madreporic body ; e, eye ; mo, mouth ; ag, ambula-
cral groove ; /, tube feet ; rt, radial water tube ; /, digestive gland ; b, body cavity ;
5, plates of skeleton.
218
ECHINODERMATA 219
is no brain. There is no heart or definite system of
blood vessels. There is, however, a remarkable water- Water-
vascular system, which consists of a series of tubes con- system
nected with tube feet or podia, especially conspicuous in
the starfish, where they serve for locomotion. In a
starfish or sea urchin a sievelike plate (madreporite) may
be found on the upper (aboral) surface. Through this
water passes into a canal, propelled by movements of
minute cilia. This canal or tube ends in a tubular ring,
from which proceed radially five tubes, following the
arms of the starfish, or ascending within the sides of the
sea urchin. Extending from these radial tubes are small,
hollow processes, the tube feet. The structure is some-
what more complicated than this brief description would
suggest, and of course differs in detail in different groups,
but the fundamental pattern is that just outlined. In
the wormlike sea cucumbers the canals are present in the
young, but lost in the adult. The sea urchin was
studied ages ago by Aristotle, and because of its spiny
surface he called it Echinus, or hedgehog. This name
is still used for the animal, and has become the basis of
the name of the phylum, Echinodermata meaning
"hedgehog-skinned" or "spiny-skinned." Aristotle
observed that the mouth and gullet of the sea urchin
(on the lower surface) are surrounded by a series of
elongated pointed plates, which serve for mastication.
The whole structure resembles a lantern, and is often
called "Aristotle's lantern." Reproduction is sexual, Aristotle's
but arms of starfishes, if removed with a portion of the ant<
disk, will develop into whole animals.
2. Attempts have been made to understand the Psychology
psychology of echinoderms. Professor Jennings, work- starfish
ing on the coast of California, made many experiments
with the common starfish of that region. The animal
220 ZOOLOGY
readily responds to direct stimuli, of course, but is it
capable of utilizing its past experiences ? When a star-
fish is turned on its back, it feels uncomfortable, or acts
as if it felt so. With its arms it tries to take hold of
some neighboring object and turn over. Obviously if
all five arms acted at once, they would counteract one
another, and the animal would remain in the reversed
position. Hence as soon as one arm has a good hold,
the others cease to oppose it, and success results. When
the surface is flat, it is a matter of chance which arm
initiates the work. Now Professor Jennings conceived
the idea of holding down four of the five arms, and caus-
ing a given starfish repeatedly to use a particular mem-
ber in the act of righting itself. After repeated lessons,
he found that the animals would continue for a time to
use this arm in preference to the others, even when not
interfered with. Thus it seemed to have memory,
though the education of starfishes is an expensive busi-
ness, requiring a separate tutor for each individual and
the repetition of the whole course about once a week.
Critics suggested that after all there was perhaps no true
educational process, but that the impeded arms were
slightly injured or stiffened, or suffered from lack of
exercise, giving the active one a better chance. Whether
the starfish remembers or not, it is a persevering animal.
It can open clamshells by sheer persistence, although in
a single pull the mollusk is the stronger. The starfish
envelops the shell, and the poor mollusk, striving to save
its life, exerts its adductor muscles to the utmost, shut-
ting the valves "as tight as a clam." It has been cal-
culated that the starfish can exert a pull equivalent to
I3S° grams, but the mollusk can resist one of 4000
grams. However, the starfish has more " staying power,"
and tires out its prey, which finally has to succumb.
ECHINODERMATA
221
3. The echinoderms may be divided into three sub- Divisions of
phyla, called Pelmatozoa, Asterozoa, and Echinozoa. dermata
The Pelmatozoa in-
clude the cystoids,
blastoids, and cri-
noids, but only the
last of these divisions
is living today. The
other two disappeared
before the end of Pa-
laeozoic time, but were
important groups in
their day. The Pel-
matozoa are fixed,
usually with a distinct
stalk, on the aboral
surface, and conse-
quently the mouth
is directed upward.
Exceptions to this
statement are found,
however, in the adults
of many crinoids,
which are wholly free, and might easily be confused
with starfishes. The word crinoid means "like a lily" Crinoids or
and has been given because of the long-stalked forms, sealUies
with the so-called calyx and feathery arms at the sum-
mit, resembling flowering plants. The crinoids were
dominant during the Palaeozoic, producing innumerable
genera and species, often of large size and complex form.
A wonderful slab of fossil crinoids (Scyphocrinites) may
be seen in the United States National Museum. These
existed during a period when much of the interior of
North America, east of the Rocky Mountains, was cov-
From Perrier's "Traitf de Zoologie'
FIG. 51. Isocrinus (or Pentacrinus) asteria.
222
ZOOLOGY
ered by a shallow sea, an American Mediterranean. In
these waters crinoids existed in vast numbers, and their
remains may be found in the rocks over a large part of
the country. When this sea was drained, during the
Mesozoic, the crinoids mostly died out, leaving com-
paratively few representatives. In more modern times
many genera and species of crinoids have come into ex-
istence, but they mostly show little resemblance to those
of remote antiquity, and there is no reason to suppose
that the group will ever again recover its ancient glory.
starfish 4. The Asterozoa, or star animals (Greek, aster, a
star, from which our English word is little modified), in-
clude the starfishes and brittle stars. There are very
important differences between these groups, although
both have the starlike form, with arms extending from
a central disk. In the Asteroidea or true starfishes, the
arms are usually five, but may be much more numerous ;
they are not sharply marked off from the central disk.
The arms present on the under surface ambulacral
grooves, with podia (singular, podium) or tube feet. In
Brittle stars the Ophiuroidea (snakelike animals) or brittle stars
there is a round central disk, with long, wormlike arms
which curl around objects presented to them. The
ambulacral grooves are closed, and the podia have only
sensory and respiratory functions. The arms readily
snap off, whence the name brittle star. In the ophiu-
roids the madreporite is on the oral side of the disk.
Although the asteroids and ophiuroids are so easily dis-
tinguished, there is a group called Lysophiuroida, found
in the Palaeozoic rocks of Europe, which is more or less
intermediate between the two, indicating that they had
a common ancestor.
5. The Echinozoa include also two extremely distinct
groups, the Echinoidea or sea urchins, and the Holothu-
ECHINODERMATA
223
From " Animate Creation"
FIG. 52. A sea urchin, showing spines and extended podia.
roidea or sea cucumbers. They agree in being without Sea urchins
arms or stalk, but their superficial appearance would
not suggest any affinity. The sea urchin is variously
rounded or oval, conical or flattened, with a hard surface
to which are attached numerous spines. These spines
may be clubbed, exceedingly large, and thick, or they
may be very slender, sharp, and needlelike. There are
also very peculiar structures known as pedicellarice,
which may likewise be found on starfishes. They ap-
pear to be modified spines, but have the form of a little
stem, on the end of which are two or three pincer-like
valves, which open and shut. These pedicellariae differ
in form and function. Some grasp and destroy minute
swimming larvae of animals which might settle on the
224
ZOOLOGY
Sea
cucumbers
The Cu-
vierian
organs
Echinus.. Others break up particles of grit, while some
hold small Crustacea and other animals until the tube
feet can reach them and pass them to the mouth. Some
have poison glands, and serve to repel the attacks of
enemies. The common California sand dollar is a very
flat echinoid, adapted, as are the flatfishes, for life on
sandy bottoms, where they offer little resistance to the
currents or tidal movements of the water.
6. The Holothuroidea, shaped like a cucumber or a
worm, at first present no resemblance to the echinoids.
If we imagine an echinoid to be soft, and to be elongated
by pulling at the oral and aboral ends, it will assume a
form resembling that of a holothurian. Instead of
having a hard shell, the sea cucumbers possess only an
imperfect skeleton, usually in the form of minute spic-
ules, reminding us of the
sponges. In some cases
the skeletal elements are
entirely absent. It is dif-
ficult to preserve good
specimens of holothuri-
ans, because of their
behavior when irritated.
Sometimes they turn in-
side out, or rather extrude
the internal organs of the
body. The first parts
extruded are the Cuvier-
ian organs (part of the
respiratory apparatus),
which form a tangle of
sticky white thread, en-
veloping and rendering
helpless any creature FIG. 53. A sea cucumber.
ECH1NODERMA TA 22$
which has had the temerity to attack the holothurian.
A large lobster has been seen thus ensnared, and quite
unable to move. It might be supposed that this mode
of defense would be fatal to the sea cucumber, but
that animal merely goes into retirement for a time, and
regenerates the lost parts.
The wormlike species (Synapta) behave differently.
The posterior part of the body is amputated, while the
head with its feelers buries itself in the sand or mud.
The Echinodermata, whatever their origin, have them-
selves given rise to no other groups. They represent a
separate branch of the tree of life, as do the sponges and
mollusks.
Characters
o Bryozoa
CHAPTER THIRTY
BRYOZOA
I. THE Bryozoa (the term meaning "moss animals")
small aquatic creatures, mostly marine, nearly
From "Animate Creation"
FiG. 54. Bryozoans, Plumatella, from fresh water. The upper figure greatly
enlarged.
always living in colonies or zoaria, often looking very
much like seaweeds or corals. Each separate individ-
ual (zooid) is placed in a membranous or calcareous
(limy) sac, called the zooecium. They differ entirely
from coral animals in possessing an alimentary canal
with two openings, and a well-developed nervous system,
distinct body cavity, etc. The mouth is surrounded by
delicate respiratory tentacles. The colonies are formed
by gemmation or budding, but the animals have sexual
organs, being usually hermaphroditic. There is no
heart or true blood system.
The Bryozoa are of great antiquity, and are abun-
226
ERYOWA
227
dantly preserved as fossils. Like the much more primi- Antiquity of
tive sponges, they represent an isolated type, which has
produced a great number of genera and species, without
showing much real progress.
BRACHIOPODA
I. The nearest relatives of the Bryozoa are the so- structure of
called lampshells or Brachiopoda. They are exclusively Brachi°P°da
marine, and today are relatively rare, fewer than 200
species being known. In Palaeozoic times they were
extremely numerous, and thousands of forms have been
made known from the fossil remains. The name "lamp-
shell" is derived from the fact that in typical forms the
bivalved shell, more or less oval in form, shows an open-
ing at one end for the pedicel by which the animal is at-
tached to a rock or some other solid object. The shell
consequently resembles a Roman lamp, such as those
recovered at Pompeii, the opening corresponding to that
for the wick. For many
years the Brachiopoda
were classified as mol-
lusks, but the most super-
ficial examination of the
internal organs shows that
this is entirely erroneous.
On opening the shell we
find the variously coiled or
twisted brachidia, which
support the brachia or
fleshy arms ; the latter
possess a respiratory func-
tion, and also set up cur-
rents of water which serve
From Nicholson's " Classifica-
tion of the Animal Kingdom "
FIG. 55. Brachiopods. A, B, Lingula;
C, Waldheimia ; D, Isocrania. p, pedun-
cle; v, ventral valve; d, dorsal valve; s,
sand particles inclosing end of peduncle.
228
ZOOLOGY
Lingula, an
ancient
type still
surviving
to convey small particles of food to the mouth. These
structures are fully developed in the typical lampshells,
but are variously modified in other families. The sexes
in the Brachiopoda are separate.
The burrowing species, typified by Lingula, are oblong
and flattened, with thin shells, and have a long, worm-
like pedicel. Living specimens may be obtained on the
California and southern Atlantic coasts, and extremely
similar shells come from the older Palaeozoic rocks. We
thus think of the Lingula as one of the oldest of all
living creatures, little changed during many millions of
years.
CHAPTER THIRTY-ONE
PLATYHELMINTHES
I. IT was formerly customary to include under the The Vennes
name Vermes^ a great variety of different organisms, UJ^JJ?8
roughly classed as worms. These did not. of course, writers
include the so-called worms which are the larvae of in-
sects, but they did include such creatures as rotifers,
which would not usually be thought of as worms at all.
It could be said of the Vermes that they were bilaterally
symmetrical, usually greatly elongated or "vermiform,"
with a distinct body cavity between the intestine and
outer wall. They could thus be excluded from the
ccelenterates and echinoderms, while the absence of
distinct jointed appendages served to indicate that they
were not Arthropods. In recent works these Vermes or
Vermidea have been divided, so that today we recognize
flatworms, nemertines, threadworms, rotifers, and anne- Fiatworms
lids, forming a series of phyla. The flatworms are
called Platyhelminthes, which is an exact Greek transla-
tion of the English term. The Greek word for a
worm appears in many other combinations, and a stu-
dent of worms calls himself a helminthologist, while a
society for the study of worms is a helminthological
society.
The flatworms, as the name suggests, are more or less Groups of
flat and usually ribbonlike. They are usually divided flatworms
into three classes, the Turbellaria, Trematoda, and Ces-
toda; but a fourth division is indicated by a group of
peculiar animals living on the outer surface of fresh-
water Crustacea, turtles, etc., to which the name Temno-
cephaloidea has been given. The Turbellaria or plana-
1 Our word "worms" is a strict equivalent. There is no "W" in Latin:
thus the Latin vallum is our "wall."
229
230
ZOOLOGY
Land and
fresh-water
flatworms
Parasitic
flatworms
rians are free-living flatworms, with ciliated skin, hav-
ing the alimentary canal in the form of a blind sac,
B Drawing by R. Weber
FIG. 56. A land planarian from Guatemala. A, about twice natural size; B, a
cross section of hinder part of body much enlarged, showing the two posterior
branches of the intestine.
— that is, with only one opening, — which may be
simple or variously lobed. On account of the form of
the intestine, there is a certain resemblance to the
Ccelenterata, but it is superficial, and does not extend
to other parts of the anatomy. Turbellarians exist in
the sea in great numbers, and are fairly numerous in
fresh water. A small, dark species may often be found
in mountain springs. There are also many land species,
looking something like slugs, living in regions where the
climate is moist. A large form has become established
in hothouses. Some of the species are quite large and
brightly colored ; others, such as the fresh-water Rhab-
doccelida, are microscopical and transparent, looking
like Protozoa, but easily distinguished by the complexity
of their anatomy.
3. The Trematoda include the parasitic worms known
as flukes. They possess an alimentary canal, but have
lost the ciliation of the body surface, and have developed
suckers or adhesive organs. There is no doubt that
they arose from free-living ancestors, and are modified
for parasitic life. Throughout the Vermidea we find
many instances of such modification, taking place quite
independently in the different groups. We can no more
PLATYHELMINTHES 23 1
put the parasitic worms together, because of their
parasitism, than we could unite in one group of plants
the parasitic rust fungi and the mistletoe. The de- The liver
structive liver fluke of the sheep may be taken as an
example of this group. It lives in its early stages in a
small fresh-water snail (Lymncea), common in Europe
and America. The young flukes, known as cercarice,
eventually leave the snails and attach themselves to the
grass at the edge of the pond, where grass and worms are
eaten together by the sheep. In the body of the sheep
they seek the liver, where they develop to full size.
Eggs are produced, which become scattered over the
pastures, and when they hatch, the snails, if present, be-
come infested. It used to be estimated that a million
sheep died annually in the British Islands from the at-
tacks of the liver fluke, but now that the life history is
known, it is comparatively easy to guard against infes-
tation. The European liver fluke is not native in
America, but has been introduced unintentionally by
man. There is, however, a large native American
species.
4. The cestodes, or tapeworms, represent the most Tapeworms
extreme specialization for parasitic life among flat-
worms. They are flat and white, resembling tape, but
usually segmented. The alimentary canal is wholly
absent, even in the early stages. The unsegmented
tapeworms are rarely observed; and we may take the
common segmented forms, such as T<znia, as typical of
the group. In these the adult worm possesses a so-
called head, which produces no eggs, but carries the
organs which fix the animal to the intestine of the host.
Following the head are numerous segments or pro-
glottids, which are egg-producing, and usually drop off
from time to time when mature. The segmentation is
232
ZOOLOGY
Life history
of the
tapeworm
entirely different from that of an annelid or arthropod,
in which the successive segments carry different organs
and together make up a
single animal of which
they are the necessary
parts. In the tapeworm
the segments in a sense
represent different indi-
viduals, attached but not
combining to form parts
of a single machine. Each
segment takes nourish-
ment independently,
through the skin, and each
one produces eggs when
mature, excepting only the
"head" orscolex.
The eggs give rise to a
hooked embryo (or in
some species to a ciliated
larva), which seeks the
proper host and develops
into a bladder worm or
Cysticercus. The host of
the Cysticercus is usually
, r , , . FIG. 57. A tapeworm, Tania solium:
eaten by the final host, in a> head; b§ a progiottid; B, a single
the body of which the ma- progiottid detached; p, genital pore; u,
ture tapeworms develop.
The invention of cooking by man not only made many
substances palatable and digestible, but was of great
importance as a means of destroying the young stages
of parasitic worms, which would otherwise be eaten
alive.
From Nicholson's "Classification
of the Animal Kingdom"
CHAPTER THIRTY-TWO
NEMERTINEA
I. THE nemertean worms are little "known to the Characters
general public, as they are of slight economic impor- *J*
tance. They mostly live in the sea, burrowing in mud teans
or sand, or hiding under stones and among the holdfasts
of large seaweeds. Fresh-water and even land forms
have been found, the latter living in moist earth or de-
caying vegetable matter. There are even a few para-
sitic or 'semiparasitic forms, though nemerteans in
general live independently. The great majority are
long and more or less cylindrical, and, as in the Tur-
bellaria, the skin is ciliated and the body is unseg-
mented. There is, indeed, much resemblance to the
flatworms, but the alimentary canal has two openings
(as in all the higher worms) instead of one. The mouth
is furnished with a remarkable proboscis which is capa-
ble of being everted. The sexes are usually separate,
whereas the flatworms are hermaphroditic, with very
few exceptions. Some of the marine species attain
extraordinary lengths ; the threadlike Linens is said to •
reach a length of 27 meters. Others are beautifully
colored, — bright red, orange, or pink, or purplish with
white cross lines. They are carnivorous, attacking any
animals which are not too large.
NEMATHELMINTHES
I. The Nemathelminthes are the threadworms; the structure of
scientific name is only the English one in Greek. They
have the usual wormlike shape, — cylindrical, not flat,
and without visible segmentation. The group in gen-
eral is parasitic, but small forms may be found com-
233
234
ZOOLOGY
Habits and
abundance
of thread-
worms
Parasitic
thread-
worms
monly in water or damp earth. They are not ciliate.
The sexes are almost invariably separate. They are
divided into the Nematoda
or nematodes ; the Nemato-
morpha, which include the
hairlike Gordius ; and the
Acanthocephala, a group of
curious parasites having re-
curved hooks on the proboscis:
The nematodes, or typical
threadworms, exist in the
greatest variety and abun-
dance. They are parasitic on
animals and plants, many
of them infesting man.
Although the parasitic forms
are best known, Dr. M. A.
Cobb, who has paid special
attention to the subject, be-
lieves that the free-living
ones, when fully described,
will prove even more numer-
ous. He states that the
nematodes in a lo-acre field,
if arranged in single file,
would form a procession long
enough tO reach around the
WOrld.
To give Some idea of the stomach> *• intestine; o, ovary;
p, genital pore.
numbers occurring as para-
sites, we may cite the case of a young horse in which
were found 500 A scar is, 190 Oxyuris, several millions
of Strongylus, 214 Scleroslomum, and 287 Fiiaria, not
to mention a quantity of tapeworms. Some of the
B
From Nicholson's "Classifica-
tion of the Animal Kingdom"
J^ *?: A nematode worm
dilis bioculata) , female, enlarged.
g, gullet; v, muscular gizzard; s,
NEMATHELMINTHES 235
diseases produced by these animals are extremely seri-
ous. Trichinosis is due to infestation by the small
nematode Trichinetta, which we get through eating in-
fested pork which has not been sufficiently cooked.
The notorious hookworm of the Southern states is also
a nematode.1 So also is the African Guinea worm,
which lives first in a minute fresh-water crustacean
(Cyclops), and is swallowed by man in drinking water.
Another species infests man and the mosquito alter-
nately. A nematode, attacking the roots of plants,
produces swellings or galls. Another is very injurious
to the sugar beet.
The structure of nematodes is quite complicated, so
that Dr. Cobb, in making a diagram of the anatomy, is
able to enumerate no less than 116 distinct parts. For-
tunately the small species are transparent, so that the
various organs can be seen in the living animal.
References
COBB, M. A. "Nematodes and Their Relationships." Yearbook United
States Department of Agriculture for 1914. For a well-illustrated ac-
count of the genera, see WARD and WHIPPLE, Fresh-water Biology. 1918.
ROTATORIA
I. The Rotatoria, or rotifers, are minute aquatic structure of
animals which may be taken for Protozoa, unless atten- arotifer
tion is paid to their anatomy. They seem to have
"wheels in their heads," owing to the presence of con-
stantly moving cilia arranged in a circle around the
anterior end. As they are usually quite transparent,
it is easy to see the chitinous gizzard or mastax, the ali-
mentary canal, reproductive organs, etc. The common
free-swimming forms have a short bifurcated or two-
1 See the publications of the Rockefeller Sanitary Commission for the
Eradication of Hookworm Disease.
ZOOLOGY
toed tail, but there are species (as Melicerta) which are
attached and surrounded by a tube. These tubes stand
on end, projecting at right
angles to the surface to which
they adhere. Rotifers are
most abundant in fresh water,
but rather numerous species
occur in the sea. Some ab-
errant genera are parasitic.
A remarkable property of
rotifers is that of resisting
desiccation ; as the. water in
which they live dries, they
secrete gelatinous plugs at
either end of the body and
are thus protected within
their own skins, where they
can resist great extremes of
temperature as well as dry-
ness. This property enables
them to survive the most un-
toward circumstances, and to
be carried accidentally from
place tO place, with the re- From Perrier 's" ^ Train deZoologie"
Suit that the Species are ex- FIG. 59. A rotifer, Hydatina senta,
tremely widely distributed.
female; greatly enlarged.
References
HARKING, H. K. Bulletin 81, United States National Museum. Gives a list
of all the known species, and a full bibliography.
Cambridge Natural History, Vol. II. Good general account by Marcus
Hartog.
CHAPTER THIRTY-THREE
ANNELID WORMS
1. THE higher worms are distinguished by the seg- structure of
mentation of the body (into annuli or rings) and, except worms"5
in leeches, by the presence of bristles which can be used
in locomotion. Thus, an earthworm appears perfectly-
smooth, but pass the fingers along the sides, and it feels
rough. Examination with a lens reveals little project-
ing points, which give the worm a hold on the walls of
its burrow, recalling, the spiked shoes of the telephone
company's "trouble man." These bristles or spinelike
structures are called "chaetse," and hence the great
group so common in the sea, distinguished by the
abundance and length of the chaetse, is called Poly-
chceta (many bristles). In contrast with them, the
earthworms and their relatives are called Oligochceta
(few bristles). While these are the two main groups of
annelids, we must associate with them a third important
group, the Hirudinea or leeches. These may be recog-
nized by the flattened under side and the presence of an
adhesive disk or sucker, at each end of the body. There
is also a small group called Archiannelida, the members
of which have rings of cilia around the body, but no
bristles, and when adult are not visibly segmented. As
in so many other cases, the place of these animals in the
classification is determined by the totality of their
characters, and would not be suspected on superficial
examination.
2. The ringed worms are not only interesting in Resem-
themselves, but also on account of their apparent
affinity with the Arthropoda, the great group which in-
cludes the insects and Crustacea. First of all we have
the segmentation of the body, so characteristic of
237
ZOOLOGY
The Poly-
chaete or
many-
bristled
worms
arthropods. Then there are the bristles, often placed
(as in the marine Nereis) on lobelike outgrowths which
resemble rudimentary legs. The head, though without
antennae', may be provided with long tentacles, and we
can often recognize jaws which are very like those of
an insect. Thus we have an animal which satisfies in a
general way the requirements of an ancestor of the ar-
thropods, foreshadowing their characters, though not of
them. The comparatively low organization is shown by
the fact that many marine worms retain the method of re-
production by constriction or budding, forming a series of
individuals joined at the ends, like a string of sausages,
ultimately coming apart. This goes with true sexual
reproduction, as we have found in the lower groups.
3. Polychaete worms
are aquatic, and al-
though a few species
live in fresh water, the
sea is the habitat of
the vast majority of
the species. Some are
free swimming, others
make tubes, often re-
minding us of those
constructed by insect
larvae. Many are beau-
tifully colored, and this
ornamentation may be
due to different causes.
Sometimes the bristles
densely covering part
of the body are splen-
didlv iridescent. In From Perrier's " Trait* de Zoologie"
FIG. 60. A Polychaete worm, Amphilnte
Other Cases the red, edwardsii; about f natural size.
ANNELID WORMS 239
yellow, violet, green, or other tint may be due entirely
to pigments in or under the skin. Red may be due to
haemoglobin in the blood, the substance which also
makes our blood red. The worm is so transparent that
the full red color of the blood shines through the skin.
This case is interesting in reference to the question
whether the bright colors of many marine worms have
any useful purpose. Obviously haemoglobin has a
function in relation to respiration, and its red color may
have no particular significance as such. Did we not
know the physiological significance of haemoglobin, we
might be puzzled to offer any reason for the bright color
of the worm. The tubes of Polychaeta have as a basis
a secretion of the worms themselves, but frequently
particles of sand or fragments of shell are built in, much
as in the case of the tubes made by caddis-fly larvae
(page 273). The Serpulidce make calcareous (limy)
shells, suggestive of those made by mollusks. This re-
semblance is particularly striking in the genus Spirorbis,
the small tube shells of which are coiled like a snail.
The coiled shells of Spirorbis adhere to various objects,
and as they are hard they are easily preserved as fossils.
In strata many millions of years old, these small struc-
tures are found, apparently as well developed as those of
today.
Polychaete gills are 'interesting structures, finely
branched, with the form of seaweed or feathers. Aquatic
insect larvae often show gills of various forms, having
the same function of absorbing oxygen from the water.
4. The oligochaetes do not all live in the earth ; many Earthworms
inhabit fresh water. Thus the polychaetes and oligo-
chaetes divide the world between them, and there are
few places where one or the other may not be found.
Strangely, true earthworms appear to have been absent
240
ZOOLOGY
Darwin's
experiments
with earth-
worms
Structure of
earthworms
from or excessively rare in the Rocky Mountain region ;
those found there today are cosmopolitan species intro-
duced by man, excepting a small form from the moun-
tains of Colorado. Generally speaking, the ocean is a
barrier to earthworms, and hence these, like amphib-
ians, are absent from oceanic islands, except when
introduced by human agencies. When islands are
found to possess many peculiar earthworms, we infer
that they were once united with the nearest continent.
The importance of earthworms to mankind has been
shown by Charles Darwin and others. In moist coun-
tries the ground may be seen to be almost covered with
their castings after a shower. They burrow through
the soil, and bring that which was below to the surface.
Darwin allowed a field to remain uncultivated for many
years, to see how soon and how deeply the worms would
bury objects originally left on the surface. The bury-
ing process is simply one of turning over the soil,
whereby the original surface is covered by material
from beneath, and eventually sinks. In this manner
the soil is subjected to the action of the bacteria which
work in the presence of oxygen and, breaking up in-
soluble chemical compounds, render the materials in it
fit for plant food.
5. The so-called cocoons of earthworms are really
egg cases. They are oval or round objects composed of
chitin, containing several eggs. The oligochaetes are
hermaphroditic, possessing both male and female or-
gans, though these frequently mature at different times.
The alimentary canal is a straight tube running through
the body, not affected by the segmentation. Earth-
worms have no distinct organs of vision, but appear to
be sensitive to light. Although they cannot hear, they
readily appreciate vibrations in the soil. Unlike the
ANNELID WORMS 24!
polychsetes, the oligochaetes are, generally speaking,
without gills, though these structures are developed in
a few fresh-water forms. There are no jaws, except in
a peculiar group which is parasitic on crayfishes and
has no close resemblance to the earthworms.
6. Leeches (Hirudined) are usually found in fresh Leeches
water, where they swim with an undulating motion. In
moist regions land leeches may be found, and there are
even marine species. The medicinal leech (Hirudo
medicinalis\ formerly used to draw blood, possesses
jaws. Other leeches have a proboscis, but are without
jaws. The Hirudinea resemble the earthworms in the
segmented body, and also in the egg cocoon, which may
be found attached to plants or rocks in ponds. With
one exception chaetse are absent, and this separates
them from all the oligochsetes except a few aberrant
types. There are some species with external gills.
Simple eyes are present.
We may infer that of the three great groups of anne- Lines of
,.,,,, i .... , modification
lids, the polychsetes are the most primitive, in spite 01 in annelids
the fact that they include 'many specialized forms. The
leeches and earthworms are related, but represent
widely divergent branches of a common stock, — both,
however, adapted to fresh-water and terrestrial exist-
ence. Of these, no doubt the oldest are fresh-water
forms. The earthworms have lost the jaws, the leeches
the chsetae ; hence it is impossible to derive either group
from the other.
References
Cambridge Natural History, Vol. II.
BEDDARD, F. E. "Earthworms and Their Allies." Cambridge Manuals of
Science and Literature, 1912.
HALL, MAURICE C. Proceedings United States National Museum, Vol. 48,
page 187. ( Account of oligochgetes, parasitic on crayfishes.) See also
242 ZOOLOGY
Max M. Ellis, Proceedings United States National Museum, Vol. 42,
page 481, and Vol. 55, page 241.
SMITH, FRANK. Proceedings United States National Museum, Vol. 52, page
157. (North American earthworms.)
MOORE, J. P. Bulletin United States Bureau of Fisheries, Vol. 25 ; and Pro-
ceedings United States National Museum, Vol. 21. (North American
leeches.)
PRATT, H. S. A Manual of the Common Invertebrate Animals, 1916. Pages
227-322. (Descriptions and figures of the commoner annelids.)
SMITH, FRANK, in WARD and WHIFFLE. Fresh-water Biology, 1918, pages
632-645. (Aquatic earthworms.)
CHAPTER THIRTY-FOUR
MOLLUSCA
1. THE Mollusca include such familiar animals as the Characters
snails and slugs, cuttlefish, oysters, and clams. They
are soft-bodied, without the chitinous external armor of
the Arthropoda. The majority of the species possess a
shell, which is secreted by the animal, and consists prin-
cipally of carbonate of lime. The alimentary canal,
blood system (with a simple heart), respiratory system
(lung or gills), and liver are well developed, and eyes are
usually present. Some feed on vegetable matter, others
are carnivorous. The number of known species is very importance
great, and as the shells are readily preserved as fossils,
mollusks are of great importance to the geologist. In
the course of time the groups of mollusks have become
variously modified and consequently their fossil remains
serve as excellent guides to the strata, each considerable
layer of rocks having its own characteristic assemblage.
2. The larger groups of mollusks are so different that Groups of
at first they seem to have little in common. Compare, MoUusca
for instance, a snail with a clam or an octopus. There
is, however, a certain similarity of structure which leads
us to place them all in a single phylum, and sometimes
very different-looking forms are found to be connected
by intermediates. Thus the snail and the slug, al-
though very distinct, are merely the extremes of a series
of species in which the shell is of all sizes, grading from
the larger one of the typical snail to the rudimentary or
hidden one of the slug. Finally, in some slugs, not even
a rudiment of the shell remains. The large group called
Gastropoda (literally stomach-footed) includes the or-
dinary coiled shells — terrestrial, fresh-water, and ma-
rine — and the naked slugs. If we examine an ordinary
243
244
ZOOLOGY
After Bulletin A merican Museum of Natural History
FIG. 61. Pyramidula ralstonensis, a fossil snail from the Eocene of Wyoming.
Enlarged about five diameters.
structure of garden or greenhouse snail, we observe that the body,
asnai1 when extruded from the shell, is elongated, with the
head at one end. There is always, of course, a portion
of the animal within the shell. The flat surface on
which the animal moves is called the/octf, and the move-
ment is by wavelike undulations, as can be seen if the
snail is caused to walk on a piece of glass. It is difficult
at first to believe that the substance of the foot is not
flowing from one end to the other, just as waves on the
ocean give the appearance of masses of water moving
rapidly forward. As the snail moves, slime is secreted
by the slime glands^ and thus the creature travels on a
track of its own laying. The head is marked by four
tentacles, the upper long ones bearing eyes at the end/
These eye-bearing tentacles can be retracted by the
contraction of internal muscles; they turn outside in,
as do the fingers of a hastily removed glove. Below the
tentacles is the mouth, which is furnished with a trans-
versely placed chitinous plate called the jaw. The jaw
moves up and down, and cuts the tissue of plants. In
certain carnivorous slugs, which devour their prey
alive, there is no jaw. In addition to the jaw is a
delicate rasping structure, the lingual membrane. This
Jaw and
lingual
membrane
MOLLUSCA
245
may be obtained by cutting .off the head of the snail and
boiling it in caustic potash solution, which dissolves
away everything except the jaw and lingual membrane.
The surface of the membrane, examined under the com-
pound microscope, is seen to be covered with innumer-
able delicate teeth, arranged in rows. These teeth are
different in different kinds of mollusks, and are of great
value for classification. Around the edge of the shell,
in front, will be seen a soft fold, which is the margin of
the mantle. This is the organ which secretes the shell,
adding always material around the aperture, until the
animal is mature, when the work is usually finished by
addition of a thickened edge, the lip. On the right- Breathing
hand side, when the snail is active, there appears an apparatus
opening, which admits air to the lung. The lung is a
simple moist sac, the walls of which are richly supplied
with blood vessels. The lung-breathing snails are
called pulmonates, and include many terrestrial and
From "Animate Creation'
FIG. 62. A large African land snail, Achatina, about natural size.
246 ZOOLOGY
fresh-water forms, but the. majority of marine species
are gill breathers. Thus the land slugs have lungs,
Eye -bearing
tentacles
Drawing by R. Weber
FIG. 63. A land slug (Limax). Natural size.
situated beneath the mantle ; but the sea slugs (nudi-
branchs) are very different, and possess external feather-
like gills. The lung-breathing aquatic mollusks, in-
cluding the commoner pond snails, have evidently been
derived from land-inhabiting ancestors. With rare ex-
ceptions they have to come to the surface of the water
to take in air.
Shell of the 3. The snail's shell, from which the principal char-
acters for the description of the species are derived, is
nearly always very distinctive. Many kinds of mol-
lusks are known from the shell alone, yet we have no
difficulty in recognizing them. The commoner form
of shell is more or less conical, the upper end being
called the apex, the lower side the base. It is composed
of whorls, twisting around a central axis, which may be
hollow and open below, the opening being called the
umbilicus. The whorls are attached to each other along
a spiral line called the suture ; the surface of a whorl
may be rounded or keeled, or may have raised lines.
The aperture of the shell, commonly called the mouth,
has of course no connection with the true mouth of the
animal. The mouth may be surrounded by a thicken-
ing called the lip, and on this are often denticles or
lamellcs. The shells of land and fresh-water mollusks
are usually thinner and lighter than those found in the
MOLLUSCA
247
sea. The marine forms, moving in a relatively dense
medium, can afford to have thick shells, and in addition
Drawing by R. Weber
FIG. 64. Freshwater Mollusca (enlarged). A, a sinistral shell (Physa). B, a
dextral shell (Lymncea).
they need to be protected from the buffeting of the
waves if they live near the shore. Most snail shells Dextral and
have what is called a dextral spiral ; that is, if the shell sheUs
is held so that the aperture faces the observer, it is on
the right-hand side. Sinistral shells have the aperture
to the left, the whole spiral being reversed. Certain
genera, as the fresh-water Physa, are regularly sinistral.
Very rarely sinistral specimens of ordinarily dextral
species are found ; these are much prized by collectors
of shells. The reversal of the normal twist, as a rare
abnormality, is not confined to mollusks ; even in man
the heart is occasionally on the right instead of the left
side.
Some marine shells, such as the Murex, are protected Sea slugs
by great spinelike projections. Even the sea slugs,
naked and apparently without any resource against'
enemies, have special means of protection. Some are
248 ZOOLOGY
colored olive-brown or red, exactly like the seaweeds on
which they live ; others (Chromodoris) are extremely
External gills
End of foot
Mantle
Drawing by R. Weber (after MacFarland)
FIG. 65. Sea slug or nudibranch (Chromodoris porter a) from the coast of California ;
showing warning coloration. It is bright ultramarine blue, with the band along
each side of the mantle bright orange (enlarged).
conspicuous, with purple or blue and orange colors.
These latter secrete substances which make them dis-
tasteful, and it is supposed that they possess "warning
coloration," enabling fishes to recognize them and let
them alone. Many of the gill-breathing Gastropoda,
especially those living in the sea, possess a circular
shelly or horny plate, the operculum, with which they
close the mouth of the shell when alarmed. When the
animal is in motion the operculum is seen attached to
the outer surface of the body, held somewhat as the
shield of a marching Roman soldier.
4. The Amphintura, formerly classed with the Gas-
tropoda, include the Chitons, a marine group which has no
spiral shell and looks as much like a crustacean as like a
mollusk. The body is flat and usually broad, and on the
upper surface are eight transverse shelly plates, giving a
false appearance of segmentation. The creature is bi-
laterally symmetrical, without any of the torsion so
characteristic of the snails. In many cases the shell
valves bear minute eyes, which may number many
thousands in a single individual. Related to the chitons
MOLLUSCA
249
is a curious wormlike group without any shell, which
may be considered the slugs of this series. Chitons are
common on rocks between tide marks on our Atlantic
and Pacific coasts ; some of the Californian species are
quite large, one being about 9 inches in length. An-
other bilaterally symmetrical group of mollusks is the
Scaphopoda, including the Dentalium or tooth shell. TheScapho-
The shell is a long, cylindrical tube, tapering apically. ^thsheiis
These are all marine.
5. The Lamellibranchiata or leaf-gilled mollusks are Bivalve
also called Pelecypoda (hatchet-footed). They are the Mollusca
bivalves, with two similar parts to the shell ; familiar
examples are the oyster, clam, mussel, and cockle.
They differ from the Gastropoda in many very impor- structure of
tant characters ; there is no well-defined head, and the ablvalve
u
m
Drawing byW.P. Hay (after model in Am. Mus. Natural History)
FIG. 66. A lamellibranchiate mollusk, the common clam or quahog (Venus mer-
cenaria), partly dissected: g, gills, mainly cut away; m, mantle; sl and s2, upper
and lower siphons ; aa and pa, anterior and posterior adductor muscles ; ht, heart ;
h, hinge ; u, umbo.
250 ZOOLOGY
foot is adapted for burrowing and consequently without
a flat surface or sole. The shell is hinged above, and the
mantle adds material all along the margins, producing
concentric lines of growth. Within the mantle, between
it and the foot, are the leaflike gills. The mantle edges
are usually united posteriorly to form more or less
tubular organs called siphons. The upper of these, the
anal siphon, is for the purpose of getting rid of waste
water and food materials. The lower or branchial
siphon is the one through which water enters, carrying
oxygen in solution, which is absorbed through the sur-
face of the gills. When the valves of the shell are ex-
amined, it will be seen that there is an apical point,
representing the earliest stage of the shell ; this is the
umbo. Below the umbo is the hinge, which in some
species is large and complicated. Within are seen the
anterior and posterior scars of the adductor muscles,
which close the shell. Passing from one to the other,
but variously curved, is the pallial line, marking the
attachment of the mantle. Many species of bivalves,
Pearls particularly the large fresh-water mussels, have the
shell lined within with a beautiful pearly substance, the
nacre. In the region of the Ohio and Mississippi rivers
the shells of these mussels are used as a source of pearl
buttons, while occasionally the nacre forms around some
object in a globular fashion, and is then a true pearl.
It has been found that pearls result from the presence
of parasites, which are inclosed and rendered harmless
by the secretion of nacre.
Cephalopoda 6. The Cephalopoda or head-footed mollusks include
the octopus, squid, nautilus, and the extinct ammonites.
Although the shell is spiral, the animals are symmetrical.
The foot forms a series of appendages surrounding the
mouth ; thus the octopus derives its name (eight-
MOLLUSC A 251
A B
FIG. 67. An octopus. A, upper surface showing body and eyes, B, lower surface
showing the adhesive disks.
footed) from the eight long tentacles, which bear ad-
hesive disks. The eyes are often exceedingly large and The eyes
well developed, superficially extremely like those of
vertebrates, and possessing similar parts. Since the
mollusks belong to quite a different stem from the
vertebrates, the independent development of eyes so
similar in form is a remarkable example of "convergent
evolution." Most cephalopods (but not the Nautilus) The ink sac
have an ink sac, from which is expelled a black sub-
stance serving to confuse an enemy and facilitate suc-
cessful flight. In function it corresponds with the
"smoke screen" used by steamers as a protection
against submarines. It is this black material which
has been used as a paint under the name of "sepia."
The shell may be absent, as in the Octopus. When shell of the
present, it may be external, as in the Nautilus, or in-
ternal. In the latter case it may be quite rudimentary,
a condition paralleling that of the slugs. The nautilus
and ammonite shells are divided internally by septa into
a series of compartments, only the last or outer of
which is occupied by the animal. In former geological
ages the Cephalopoda were more abundant and varied
252
ZOOLOGY
FIG. 68. Shell gallery, British Museum Natural History, London, showing large
models of cephalopods suspended from the ceiling.
than at present, and were especially represented by the
ammonites, sometimes as large as a cart wheel.
References
BINNEY, W. G. A Manual of American Land Shells. Bulletin 28, U. S.
National Museum, 1885.
PELSENEER, PAUL A. A Treatise on Zoology. Edited by E. Ray Lan-
kester, Part V, 1906.
ROGERS, JULIA E. The Shell Book. Nature Library, 1913.
BAKER, F. C. The Mollusca of the Chicago Area. Bulletin III, Chicago
Academy of Sciences. Part I, 1898; Part II, 1902.
KEEP, JOSIAH. West Coast Shells, Revised Edition, 1912.
CHAPTER THIRTY-FIVE
ARTHROPODA
THE phylum Arthropoda (from the Greek, meaning Antiquity of
"with jointed feet") includes more species of animals
than all the other phyla combined. It is of immense
antiquity, with representatives in the Cambrian rocks,
laid down not less than 30 millions of years ago. A
terrestrial form, a scorpion, is known from the Silurian
strata, and is more than 20 millions of years old. Un-
like some of the ancient groups, the arthropods have
continued to flourish up to the present time, producing
in all ages vast numbers of genera and species, adapted
to almost every conceivable condition of life.
The earliest known arthropods were marine, and must Evolution of
have been derived from some primitive type of seg- Arthr°P°da
mented worm. The characteristic feature is the ex-
ternal more or less hard covering (exoskeleton), the
essential basis of which is the hornlike substance
chitin, though there may be also a deposit of carbonate
of lime, as in the larger Crustacea (crabs and their rela-
tions). In the segmented worms paired appendages
(parapodia) are frequently well developed. These are
muscular projections from the body, and often bear
remarkable chsetae or bristles, which may be jointed.
The arthropod has such paired appendages still further
developed, the majority being jointed and serving as
legs. They commonly arq bristly or hairy, and bear
one or two claws at the extremity. With the develop-
ment of a hard surface, segmentation is necessary to
permit flexibility ; so not only the body but also the
appendages are jointed at intervals. Among the vast
numbers of arthropods known, species will be found
which do not agree with the general definition of the
253
254
ZOOLOGY
phylum. They may be quite soft-bodied and legless,
so that on inspection one would never suspect their
relationships. In such cases the zoologist is guided by
the general structure, which serves to indicate relation-
ships with more typical or ordinary forms. In many
groups degenerate members are found living a seden-
tary or parasitic life, and losing the striking peculiarities
which were developed by their ancestors.
TheTardi- A very singular and perhaps really primitive type of
water bears arthropod is the so-called water bear. Water bears or
Tardigrada are microscopic animals found in ponds and
ditches, along with Protozoa, rotifers, and small worms.
They are transparent, more or less cylindrical, but fairly
stout, with four pairs of short, stout legs which are not
very different from the parapddia of worms. There is
a simple alimentary canal, but there are no well-
developed mouth parts or definite breathing organs
or blood system. The muscular fibers of the body and
appendages are unstriated, as in the case with muscles
not under voluntary control. Each individual carries
the organs of both sexes, and is
therefore said to be hermaphro-
ditic.
What are we to think of such
a type ? Is it really a primitive
form allied to the worms, a-nd
surviving from a bygone age ? Or
is it a degenerate descendant of a
more highly developed ancestor ?
In any event, it is 'today an iso-
lated group, regarded as more or
less related to the mites, but
really without cousins in this
world. The species seem to be
Drawing by W. P. Hay
FIG. 69. Echiniscus, one of the
Tardigrada; greatly enlarged.
ARTHROPODA 255
few, but they have been little studied in this country.
Any one who will investigate them patiently is sure to
make discoveries. Although the group is essentially a
fresh-water one, there are very few marine representa-
tives, while some are terrestrial, living in damp places.
Regarding the arthropods broadly, we divide them into
two great series : one adapted to aquatic life and usually
breathing by means of gills; the other characteristically
terrestrial. The first includes the Crustacea, the sec-
ond the Arachnida, Prototracheata or Onychophora,
Myriapoda, and insects. On investigation, we find land
Crustacea and aquatic arachnids and insects ; so the
distinction of habitat is only broadly valid. We find,
however, that such animals as the insects and spiders
have developed special organs for breathing air, and Develop-
certain of them, when living in the water, carry a bubble breathing""
of air entangled in the hairs of the abdomen. We are stnjcturcs
reminded of the whale, a mammal which has become
modified for aquatic existence, but is still obliged to
breathe air. Yet many insect larvae, such as those of
the may-flies, breathe the oxygen dissolved in the water.
These have developed gills, but apparently not very
efficient structures, since in many cases the animals can
live only in running water, where a new supply of oxygen
is continually brought to them. Everywhere the tend-
ency is for each group to develop members fitted for
every available mode of life, aquatic and terrestrial,
free and parasitic, motile and sedentary, limited in this
by the ability to vary and by the competition of those
which got there first. In the sea the Crustacea are Habitats of
dominant, and insects, so successful on the land, are crustaceans
practically absent. In the fresh water insects abound,
but the Crustacea also are numerous. On the land in-
sects may be said to rule, the combined terrestrial
256 ZOOLOGY
members of the other groups being relatively insignifi-
cant in numbers. Just as the insects seem with diffi-
culty to invade the waters, so the Crustacea appear to
find it hard to succeed on land. The isopod Crustacea,
called wood lice and pill bugs, -are widespread, but not
very numerous in terrestrial species. Living in damp
spots and under stones, they manage to breathe air, and
in some cases have developed tracheal tubes correspond-
ing in function to those of the insects. Yet on the whole
they have no chance to compete with the insects, which
are so perfectly adapted for aerial conditions,
structure of It is characteristic of the Crustacea that they have
insects and • r i 1 • i •
crustaceans two Pairs of antennae, whereas the insects and myna-
pods have only one, and the arachnids are wholly with-
out these structures. Here, again, exceptions occur ;
some Crustacea have only one pair of well-developed
antennae, and there are insects which have none. In-
sects never have more than six legs, except in some
larvae, such as the caterpillar. The other groups
usually have more than six, in many cases a much
larger number. Of all the groups, only the insects are
winged. Before reviewing the arthropods in detail, it
will be useful to give a summary of the principal groups.
CHAPTER THIRTY-SIX
PHYLUM ARTHROPODA
Class Crustacea
Subclass Trilobita
THE trilobites, now entirely extinct, were formerly Thetrfio-
very abundant in the sea. They were highly developed ^^tn
as early as Cambrian time, group
The body was segmented,
and bore very numerous
jointed appendages. It is
possible that these primi-
tive Crustacea gave rise to
some centipedelike type
which took to the land,
developing tracheae or air
tubes for breathing. It
has been suggested that in
this manner the trilobites
may have been remote an-
cestors of the insects ; but
Dr. G. C. Crampton, of the
Massachusetts Agricultural
College, has lately given
good reasons for excluding
them from the direct line
of ancestry. At the time
when the insects were becoming dominant the trilobites
were disappearing.
Subclass Eucrustacea (or Crustacea proper)
The appendages are modified in various ways, for Appendages
locomotion, for feeding, and as organs of sense. Conse-
257
FIG. 70. A trilobite, Dalmanites, show-
ing the dorsal surface.
ZOOLOGY
Modifica-
tion of
appendages
quently the larger crustaceans, such as the crayfish,
which are easy to examine, are commonly used to illus-
Photograph by W. P. Hay
FIG. 71. A "lady crab" (Ovalipes ocellatus], about half natural size.
Found in the sea along the Atlantic coast.
trate an important evolutionary principle, the modifica-
tion for various functions of a series of originally similar
parts. It is not difficult to see that the two pairs of
antennae, the mouth appendages and the feet, are built
upon the same general plan, but are greatly altered in
detail to serve different purposes. The same principle
is illustrated in the mammalian teeth, which are vari-
ously modified for grinding and cutting, or in the hands
and feet of man. The typical crustacean appendage is
said to be biramose (two-branched) ; that is to say, it
has a basal part and 'two terminal parts, like a hand
with two fingers. The outer of these terminal parts
is called the exopodite (outer leg part) and the inner the
endopodite (inner leg part). In this respect the Crus-
tacea differ from the terrestrial group of arthropods,
but the legs of terrestrial Crustacea (Isopoda), as
well as of many aquatic forms, are without the ter-
PHYLUM ARTHROPODA
259
minal division. No doubt the early Crustacea, with
branched appendages, were essentially swimmers, and
Photograph by W. P. Hay
FIG. 72. A prawn (Palcemonetes), which occurs in great numbers along the
south Atlantic coast and is extensively used as food.
the unbranched leg has evolved for walking, whether in Evolution of
the water or on the land. Adaptation for walking in the w g egs
sea, and on the rocks and seaweed at low tide, made pos-
sible the eventual population of the land by arthropods.
The Entomostraca are mostly small Crustacea, especially
abundant in fresh water, and including some very an-
cient types. The "higher" and mostly larger Crustacea
are called Malacostraca. Some, such as the crab and
crayfish, possess a carapace or shield covering the thorax ;
others, including the terrestrial wood lice, are without
this structure.
Class Arachnoidea
A great series of arthropods in which the antennae
are wholly absent and the head and thorax are usually
fused into a cephalothorax.
260
ZOOLOGY
Ancient
Xiphosura
Subclass Xiphosura
Aquatic animals,
known as horseshoe
crabs, on account of the
outline of the cephalo-
thorax. They differ from
the true arachnids in pos-
sessing gills. The name
Xiphosura (sword tail.)
refers to the swordlike
(or spinelike) tail. The
horseshoe crabs, or king
crabs, which of course
are not crabs at all, grow
to a large size, and may
be found in abundance
in the sea along our
Atlantic coast. Large
specimens are about a
foot and a half long, and
the color is dark brown.
Although the individuals
are many, all belong to a single species, Limulus (or
Xiphosura) polyphemus. Several others occur in Asiatic
seas, but the group is a very small one in the existing
fauna, evidently an ancient type represented by a few
survivors. At Mazon Creek, Illinois, nodules of the
carboniferous period are found containing fossil animals
and plants, and among them a primitive king crab
called Euproops dance. This animal, which lived more
than ten million years ago, inhabited fresh water ; so
it is not unlikely that the Xiphosura had their origin in
inland waters.
Photograph by W. P. Hay
FIG. 73 . A horseshoe crab (Limulus) show-
ing the ventral surface; about J natural
diameter.
PHYLUM ARTHROPODA
26l
Subclass Arachnida
Mainly terrestrial animals, the most familiar being characters
the spiders and scorpions. The group also includes the ofarachnids
mites, of which many are aquatic, some living in the
sea. There is also a remarkable and aberrant group,
with small body and very long legs, known as sea
spiders (Pycnogonida), and found exclusively in the sea.
These differ so much from the typical arachnids that
they should probably form a separate subclass. The
most ancient arachnids appear to be those with a dis-
tinctly segmented abdomen, such as the scorpions and
harvest men. Even the spiders, which today are char-
acterized by the unsegmented abdomen, formerly had
Photograph by W. P. Hay
FIG. 74. Photograph of two sea spiders or pycnogonids. The fragment of coral
over which they are crawling is incrusted with bryozoans ; about natural size.
262
ZOOLOGY
FIG. 75. A scorpion (natural size).
distinct abdominal segments,
as the older fossils distinctly
show. A very few Asiatic
species still have this character
fairly well developed, at least
on the upper surface.
The mites, though mostly
very small, include the ticks,
some of which are as large as
peas, or even larger. Although
the arachnids have nearly al-
ways four pairs of legs, whereby
they differ at once from the in-
sects, which have only three,
gftU
duced to two pairs. The simple eyes (usually eight)
of the spiders contrast with the large compound eyes of
FIG. 76. A wolf spider.
PHYLUM ARTHROPODA 263
the insects ; but the insects also have simple eyes
(ocelli).
Class Prototracheata
The arthropods, with their jointed legs and usually
hard chitinous covering, seem isolated in the animal
kingdom. The various soft-bodied and legless mem-
bers of the group, such as the female scale insect, are
obviously not primitive, but highly specialized. Look-
ing for some real relative outside of the arthropod
phylum, we can turn only to the higher worms. These
are adapted for life in the water or in moist earth,
whereas the majority of the arthropods live on the sur-
face of the earth or on plants. The Crustacea do indeed
inhabit the waters in great numbers, but they show
little resemblance to worms. There is, however, one
group of animals which, although terrestrial, is soft-
bodied, without chitinous body rings, and doubtless
primitively so. Superficially, at least, it seems to com-
bine the features of a worm with those of a centipede.
The Peripatus, first discovered in the Island of St. Vin-
cent, West Indies, was taken by its discoverer for some
strange kind of slug. This was in 1826, and since that
time many related species have been found, widely
scattered over the earth, so that today over 70 differ-
ent forms can be enumerated. It is found that these Thetracheal
animals breathe by means of trachea, — that is to say, syst<
'minute tubes connected with small openings on the sur-
face of the body. Hence the group has been called
Prototracheata, or first (in the sense of primitive)
trachea-breathing animals.1 They resemble the terres-
trial arthropods in this feature, but the tracheal open-
ings are scattered over the surface of the body, instead
1 It is also called Protracheata and (more generally) Onychophora.
264
ZOOLOGY
of Peripatus
of being in pairs, one on each side
of each segment. Since the form of
the tracheae and other structural
features in the Peripatus are very
' unlike those of the typical tra-
cheate arthropods, such as the
insects, it is evident that we can
regard the Prototracheata only as
a relatively primitive type, not in
any sense as truly ancestral. It
is a branch from an early stock
which came off very long ago, and
has been modified in its own way,
which is not the way of the-insects
Distribution or spiders. At the present time
the species are widely scattered
and generally rare, as is usually
the case with an ancient and
waning stock. When alive, the
Peripatus is a very handsome
animal, with a soft, velvety skin,
which in some species is very
beautifully colored with subdued
shades of reddish or greenish.
The numerous pairs of soft legs
remind one of the abdominal legs
of a caterpillar, while the soft,
flexible antennae are not unlike the
tentacles of a snail or slug. The
form figured was found in South
Africa. No kind of Peripatus is
FIG. 77. Peripatus (Peripatopsis) capensis, X 3 ;
viewed from the dorsal surface. The largest speci-
men recorded was 65 mm. long.
After drawing by Miss Balfour
PHYLUM ARTHROPODS
known from the United States, but there are species in
Mexico, South and Central America, and the West Indies,
and no fewer than five inhabit the Isthmus of Panama.
Class Diplopoda
The millipedes, usually with long cylindrical bodies, Millipedes
and most of the segments bearing two pairs of legs.
They move slowly, and usually curl up when alarmed.
The surface of the body is typically smooth or tubercu-
lated, often shiny. A very ancient fossil form (Palceo-
campa, from Mazon Creek, Illinois) was profusely
hairy, and the curious little Polyxenus, still living in
various parts of the world, is hairy. In Mexico and
other southern countries very large millipedes, as long
as a finger, may be found. The millipedes and centi-
pedes have commonly been classed together as a great
group Myriapoda (many or myriad legs), but they are
really very distinct groups, though agreeing in the single
pair of antennae and the numerous segments and legs.
FIG. 78. Two millipedes.
FIG. 79. Dorsal and ventral views of
a common centipede.
266
ZOOLOGY
Class Chilopoda
Centipedes The centipedes are so called because they are supposed
to have a hundred legs, though the number differs, in
different forms, from thirty to over three hundred. They
differ from the diplopods in having only one pair of legs
to a segment, and by the greater number of joints to the
antennae. . In the diplopods the antennae do not have
more than seven joints, in the chilopods they have at
least twelve. Some centipedes (Scolopendra), common
in the Southern and Western states, are very large ; others
(Geophilus) are small and extremely slender. The poison
claws represent the first pair of legs, greatly modified.
They are connected with glands, and the secretion flows
through a passage opening near the tip of the claw.
In addition to the important classes Chilopoda and
Diplopoda, there are two represented by minute and
rarely observed species. Both have only one pair of
legs to a segment, though in other respects they differ
The greatly from the chilopods. The Symphyla (Scuti-
gerella and Scolopendrella) differ from the chilopods in
lacking maxillipeds (jaw feet), or modified legs serving
as mouth parts. They have twelve pairs of legs, and
the antennae are quite long, sometimes with as many as
fifty joints. The Pauropoda (Pauropus and Eury-
pauropus] are more like diplopods, with short and
curiously modified antennae, which are branched at the
end. They wholly lack special respiratory organs,
whereas the diplopods possess tracheae (air tubes), with
openings (spiracles) at the bases of the legs. Symphyla
and Pauropoda may be found under stones or stumps
in damp places, and are probably more widely spread
than the published records show, as owing to their
minute size they have been overlooked.
PHYLUM ARTHROPODA 267
Class Insecta
The insects, the most abundant of all animals. The Characters
head is distinct, and there are typically three pairs of
legs, all attached to the thorax. In the majority of
species there are two pairs of wings ; but these may be
reduced to two, as in the flies (Diptera), or may be
altogether absent. When the wings are absent, they
may be primitively so (e.g., Collembola), or the animals
(euch as the louse and bedbug) may be evidently derived
from winged ancestors. There is usually a distinct
metamorphosis, or change in form during growth. This
may be extreme (complete), as in the butterflies, which
hatch from eggs as caterpillars, pass through the dor-
mant chrysalis stage, to emerge as an adult (imago)
totally unlike either caterpillar or chrysalis. The wings
are never developed until the adult stage is reached, and
after reaching the adult or imago stage the animal grows
no more. If it ever seems to do so, it is only because
the body becomes distended with eggs.
The classification of insects is in an unsettled condi-
tion, owing largely to differences of opinion as to the
number of orders and other divisions to be recognized.
Some authors recognized even five different classes,
four of which are based on the primitively wingless
forms often treated as an order Aptera. Our present
treatment represents a less extreme point of view, but
like all other classifications is subject to revision. We
begin with the groups which seem to be most primitive.
Order -Protura
Minute wingless terrestrial insects, slender in form
and without antennae. Some are without a tracheal
system. There are six legs, the front pair held forward
268
ZOtiLOGY
Springtails
Thysanura
or " silver
fish"
and used as organs of touch, in the absence of the an-
tennae. The first three abdominal segments have short
appendages. These singular little ani-
mals were first made known by the
Italian entomologist, Silvestri, in 1907,
but have since been found in many
countries. They combine primitive
with specialized characters.
Order Collembola
Small, wingless terrestrial insects,
without metamorphosis. The an-
tennae are well developed, but have
few joints. A forked appendage (fur-
cula) beneath the abdomen enables the
insect to leap; in one group this is
absent. The body is sometimes
clothed with scales. These small
creatures, known as "springtails," may
be found under rocks. One kind
occurs on snow in the winter.
Order Thysanura
Wingless terrestrial insects with
slender antennae and six legs.
They do not leap, and are gener-
ally much larger than the Collem-
bola, though of no great size. A
common form, found in houses, is
somewhat carrot-shaped, with sil-
very, glistening scales, and is pop-
ularly known as the "silver fish/' From Bulletin 67, u.s
. . i • i r National Museum
It is about one third of an inch Flo 8l A «.silver fish,.
long, and has three long tails. (Lepisma).
From Bulletin 67, U. S.
National Museum
FIG. 80. A springtail
(Entomobrya) ; greatly
magnified.
PHYLUM ARTHROPODA
269
Campodea represents a very different group of Thysa-
nura, or perhaps distinct order ; a soft, fragile white
animal, with two long tails instead of three. It occurs
in damp places.
Order Orthoptera
Terrestrial insects with incomplete metamorphosis, Grasshop-
the pupa stage being active. The mouth parts are well etJs'and°k"
developed, for biting. The anterior wings, called teg- cockroaches
mina (singular, tegmen), fold over the abdomen ; but in
many species the wings are absent. The grasshopper,
cricket, and cockroach are familiar Orthoptera. It will
be noted that some, presumably the most primitive,
have no power to jump, while others possess large hind
legs and leap vigorously. The former type is illustrated
by the cockroach, mantis, and earwig, the latter by the
grasshopper, cricket, and locust. For additional par-
ticulars see Chapter 42.
Order Archiptera
This includes
the stone flies
(Perloidea or
Plecoptera) and
the May flies
(Ephemeroidea
or Plectoptera),
often regarded
as representing
two distinct or-
ders. They are
winged insects,
with incomplete
metamorphosis,
the immature
Stone flies
and May
flies
From Bulletin 67, U. S. National Museum
FIG. 82. A stone fly (Pteronarcys) .
270
ZOOLOGY
stages passed in fresh water. The stone flies have
two tails, and the wings fold over the body as in the
cockroaches. The similar segments of the thorax in
the young closely resemble those of very ancient fossil
insects. The antennae are long and slender. The May
flies, noted for the brief period of their adult life, usually
have three tails, while the antennae are short and incon-
spicuous.
Order Odonata
Dragon flies The dragon flies ; usually large insects, passing their
early stages in the water, the ugly young being absurdly
called nymphs. They are carnivorous in all stages.
The larva is active, and has no resting stage before
transforming into an adult. The adult insect has biting
mouth parts, very small, threadlike antennae, and very
well developed wings. The species differ greatly in
size, one having wings only about 9 mm. long, while in
another the hind wing of the female reaches 94 mm.
From Bulletin 67, U. 5. National Museum
FIG. 83. A dragon fly (Plathemis) .
PHYLUM ARTHROPODA
271
Order Neuroptera
A quite miscellaneous assemblage of insects, having Lace-wing
the veining of the wings more or less netlike, including
the lace-wing
fty(Chrysopa) ^ \t!Tx ^*&
and the ant
lion. In most
cases the
larvae are ter-
restrial, but
the Dobson
flies and their
relatives, often placed in a distinct order, have aquatic
larvae.
Order Isoptera
The so-called white ants, which are not ants, while Termites
some of them are black. They are strictly terrestrial,
c d
From Bulletin 67, U. S. National Museum
FIG. 84. A lace-wing fly (Chrysopa) : a, eggs ; b, larva ;
c, cocoons ; d, adult fly with left wings removed.
From Bulletin 67, U. S. National "Museum
FIG. 85. A "white ant," Termes flavipes : a, worker; b, male; c, e, f, stages of
female; d, soldier.
272 ZOOLOGY
with imperfect metamorphosis, and are remarkable for
their social life in large colonies. The anterior and
posterior wings are similar
to one another.
Order Corrodentia
The book lice (which
are not lice) and their rela-
tives ; very small insects
with long, slender antennae
From Bulletin 67, U. S. National Museum and incomplete metamOr-
FIG. 86. A "tree louse, " Psocus venosus phosis. In One grOUp the
wings are well developed,
in another group they are absent.
Order Mallophaga
Biting lice Biting lice, abundant on birds, though some genera
infest mammals. They are wingless.
From Bulletin 67, U. S. National Museum From Bulletin 67, U. S. National Museum
FIG. 87. A bird louse, Goniodes fold- FIG. 88. A head louse, Pediculus capitis
cornis (Mallophaga). (Siphunculata) .
Order Siphunculata
True lice The true lice, including those infesting man. The
mouth is beaklike, adapted for sucking.
PHYLUM ARTHROPOD A
273
Order Thysanoptera
Small insects known as thrips, common on flowers. Thrips
They feed on the
sap of plants,
and are often
injurious. The
metamorphosis
is quite incom-
plete. WingS Pfom Buuetin 6?j V s Nationai Museum
are USUally prCS- FIG. 89. Tobacco thrips: a, adult; b, antenna of same;
ent in the adults, c> young larva ; *• full^own larva-
but many species are wingless.
Order Trichoptera
The caddis flies, formerly placed with the Neuroptera, Caddis flies
but really more nearly allied to the Lepidoptera. The
larvae are aquatic, and usually construct cylindrical
cases. In one genus the larva case resembles a snail,
and was once described as such by an eminent natural-
ist. Some of the adults are so similar to moths as to
lead to confusion, but the hind wings are folded length-
wise when at rest, which is not true of the Lepidoptera.
From Bulletin 67, U. S. National Museum (after Packard)
FIG. 90. A caddis fly, larva, and its case.
274 ZOOLOGY
Order Lepidoptera
The butterflies and moths, or scale-winged insects ;
with complete metamorphosis ; the larvae terrestrial,
with few exceptions. See Chapter 38.
Order Mecaptera (or Panorpatce)
Scorpion Scorpion flies and their relatives, often regarded as a
suborder of Neuroptera. The head is prolonged into a
beak. The males of Pan-
orpa, the true scorpion flies,
have the end of the abdo-
men enlarged and curved
upward, in the manner of
scorpions. The wings when
are more Or leSS
From Bulletin 67, U.S. National
Museum (after Packard) narrow, the anterior pair
FIG. QI. A scorpion fly (Panorpa) . ••> i i • j
similar to the hind ones.
Frequently the wings are prettily marked. The meta-
morphosis is complete, and the larvae resemble caterpil-
lars. All the species are carnivorous, feeding on other
insects.
Order Hymenoptera
Bees, The bees, wasps, ants, sawflies, and their relatives.
wasps, etc. gee Chapes 39 and 40. The most primitive Hy-
menoptera are the sawflies, in which the abdomen is
broadly attached to the thorax, and the larvae have legs,
those which feed exposed on foliage closely resembling
caterpillars. Another great group consists of the ich-
neumon flies, chalcid flies, and others, nearly all parasitic
in their immature stages on other insects, and of great
importance as destroyers of insects injurious to crops.
PHYLUM ARTHROPODA
275
The wasps are very diverse, belonging to two entirely
different series, one of which (the digger wasps) is closely
related to the bees. The ants are not closely related to
From Bulletin 67, U. S. National Museum
FIG. 92. A sawfly, the so-called pear-slug (Caliroa cerasi} : a, adult ; b, c, larva
(enlarged) ; d, larvae on leaf.
From Bulletin 67, U. S. National Museum
FIG. 93. A chalcis fly (Spilochalcis maria} ; enlarged.
the bees, and have acquired social habits quite inde-
pendently. All Hymenoptera have the metamorphosis
complete.
276
ZOOLOGY
Beetles
Order Coleoptera
The beetles, usually easily recognized by the hardened
anterior wings, called elytra (singular elytron), which in
Q/ c
From Bulletin 67, U. S. National Museum
FIG. 94. A " ladybird " beetle (Megilla) : a, larva ; b, pupa ; c, adult beetle (enlarged).
The figure at the right of the illustration is a rove beetle (Philonthiis), enlarged.
the majority of species cover the abdomen and conceal
the membranous posterior wings. The posterior wings
are folded when at rest. The mouth is mandibulate ;
that is, adapted for biting, as in the Hymenoptera and
Orthoptera. The metamorphosis is complete. The
antennae usually have ten
or eleven joints.
A small group of minute
insects, parasitic on bees
and other insects, has been
separated as an order Strep-
siptera, but it may be con-
sidered a suborder of
Coleoptera.
Order Rhynchota (or
Hemiptera)
From Bulletin 67, U. S. National Museum ^ ^ b '^das,
FIG. 95. A bug, Leptoglossus oppo situs, .
one of the Hemiptera. plant llCC, Scale inSCCtS, and
PHYLUM ARTHROPODA
277
other diverse forms, characterized by the incomplete The Rhyn-
metamorphosis and the sucking instead of biting mouth chota
Divisions of
From Bulletin 67, U. S. National Museum
FIG. 06. The "seventeen-year locust" (Tibicina septendecim) : a, b, adult insects;
c, shell of nymph, after emergence of adult.
parts. In male scale insects the metamorphosis is more
nearly complete, there being a resting pupa stage.
The Rhynchota consist of two great divisions, by
some regarded as separate orders. In the Homoptera Rhynchota
the anterior wings are of nearly the same consistency
throughout, whereas in the Heteroptera (or Hemiptera
proper) the front wings or hemelytra are membranous
apically, with the basal part more or less hard and
opaque, in the manner of the elytra of beetles. The
division between the two parts is abrupt, and the divid-
ing line is more or less oblique. The Homoptera include
some very peculiar groups, such as the scale insects
(Chapter 41) and aphids or plant lice, but the more
typical form of the suborder is that of the so-called
seventeen-year locust, a large species of cicada. The
Heteroptera include many plant bugs, and others which
are predatory, feeding on different insects. Some, such
as the bedbug, suck the blood of vertebrates.
278
ZOOLOGY
Fleas
Flies
Order Siphonaptera
The fleas ; small, wingless, jumping insects with com-
pressed bodies, somewhat related to the flies. The
metamorphosis is complete
and the mouth is formed for
sucking. The antennae are
short and relatively incon-
spicuous. The bacillus of
bubonic plague is carried by
fleas, which accordingly be-
come of great economic im-
From Bulletin 67, U. S. National Museum
FIG. 97. A flea. portance in some countries.
Order Diptera
The true flies, having only two wings. The mouth
parts are adapted for lapping or sucking, and the meta-
morphosis is complete. In the presumably more primi-
tive Diptera (suborder Nematocera) the antennae are more
or less long, with many joints. This series includes the
mosquitoes, gall gnats, crane flies, and others less famil-
iar. The higher Diptera have the antennae short, or at
From Bulletin 67, U. S. National Museum
FIG. 98. A robber fly (Eicherax) with
its larva and pupa.
From Bulletin 67, U. S. National Museum
FIG. 99. A green-bottle fly (Lucilia),
showing the thoracic bristles.
PHYLUM ARTHROPODA
279
any rate with few joints, usually three. At the end of the
series we place such forms as the house fly and tsetse
fly, in which the pupa
is entirely inactive. The Chaetotaxy,
more highly specialized
flies are remarkable for
the arrangement of the
bristles on the thorax.
In addition to the gen-
eral covering of fine hair
(pubescence), there is a
series of regularly placed
bristles, the position and
number of which char-
acterize different genera
and species. The bris-
tles on the head also are
very important. Va-
rious Diptera are connected with the propagation of
the germs of disease, as we have seen in Chapter 26.
References
SHARP, D. "Insects." Cambridge Natural History, Vols. V, VI. This is
the best general treatise on insects.
COMSTOCK, J. H. and A. B. Manual for the Study of Insects. Especially
useful for the figures of wing venation.
KELLOGG, V. L. American Insects. Holt & Co.
HOWARD, L. O. The Insect Book. Doubleday, Page & Co. The numerous
plates are particularly useful, but there is no direct connection between
the plates and the text. There is a good bibliography.
RILEY, W. A., and JQHANNSEN, O. A. Handbook of Medical Entomology.
Comstock Publishing Company.
BRUES, C. T., and MELANDER, A. L. Key to the Families of North American
Insects.
SMITH, J. B. Explanation of Terms Used in Entomology. Brooklyn Ento-
mological Society.
LUTZ, F. E. Field Book of Insects. Putnam's Sons. A convenient and
useful semipopular handbook.
From Bulletin 67, U. S. National Museum
FIG. 100. A crane fly (Tipula).
CHAPTER THIRTY-SEVEN
The spirit
of Fabre
Fabre's
early years
HENRI FABRE
1. "Do you know the
Halicti ? Perhaps not.
There is no great harm
done ; it is quite possible
to enjoy the few pleasures
of life without knowing
the Halicti. Neverthe-
less, when questioned
with persistence, those
humble creatures with no
history can tell us some
very singular things ; and
their acquaintance is not
to be disdained if we de-
sire to enlarge our ideas a
little upon the bewilder-
ing rabble of this world.
Since we have nothing better to do, let us look into these
Halicti. They are worth the trouble." With these per-
suasive words does Fabre, combining the spirit of the
poet with that of the naturalist, introduce us to those
wild bees which abound in both hemispheres, unnoticed
by the common man. To him all life is interesting ; and
especially insect life, on account of the remarkable
character and diversity of its manifestations. Every
garden, every hedgerow, is a veritable wonderland.
2. J. Henri Fabre, born in 1823, spent his long life in
the warm, fertile region of the south of France, where
the Rhone wends its way toward the sea. There was
one exception to this statement; a brief period in Cor-
sica, as teacher of physics in the college at Ajaccio, gave
280
By courtesy of Dodd, Mead 6* Co.
FIG. 101. J. Henri Fabre.
HENRI FABRE 281
him access to a new fauna and flora and greatly stimu-
lated his scientific interests. Sometimes he regretted
his inability to visit remote regions. "To travel over
the world, by land and sea, from pole to pole ; to cross-
question life, under every clime, in the infinite variety
of its manifestations, — that surely would be glorious
luck for him that has eyes to see with ; and it formed
the radiant dream of my young years, at the time when
Robinson Crusoe was my delight. There rosy illusions,
rich in voyages, were soon succeeded by dull, stay-at-
home reality. The jungles of India, the virgin forests
of Brazil, the towering crests of the Andes, beloved by
the condor, were reduced, as a field for exploration, to a
patch of pebble-stones within four walls.
"Heaven forfend that I should complain! The
gathering of ideas does not necessarily imply distant
expeditions. Jean-Jacques Rousseau herbalized with
the bunch of chickweed whereon he fed his canary ;
Bernardin de Saint-Pierre discovered a world on a
strawberry plant that grew by accident in a corner of
his window ; Xavier de Maistro, using an armchair by
way of post chaise, made one of the most famous jour-
neys around his room.
"This manner of seeing country is within my means, Homesur-
always excepting the post chaise, which is too difficult J0undmgs
to drive through the brambles'. I go the circuit of my
enclosure over and over again, a hundred times, by short
stages ; I stop here and I stop there ; patiently I put
questions ; and at long intervals I receive some scrap of
a reply.
"The smallest insect village has become familiar to
me. I know each fruit branch where the Praying
Mantis perches ; each bush where the pale Italian
Cricket strums amid the calmness of the summer
282
ZOOLOGY
Fabre as a
teacher
Fabre's
studies of
insects
nights ; each wad-clad blade of grass scraped by the
Anthidium (bee)." (See Chapter 39, page 296.)
Thus the necessity for remaining at home became an
advantage. It was this intensive and loving study of
his immediate environment which made it possible for
Fabre to write his great work, or series of works, the
Souvenirs entomologiques.
3. At the age of nineteen Fabre became a teacher of
elementary subjects in the school at. Carpentras. The
salary was small, and the school a dismal place. Fabre,
with his poetic and sensitive nature, was torn by op-
posite emotions. He taught with enthusiasm, always
wishing to convey some of his own rich feeling, and of
course met with a considerable measure of success. At
the same time he was distressed by the prevalent condi-
tions, the dirt and barbarism, the impossibility of at-
taining more than a fraction of what he aimed at. Thus
he was glad to leave the primary work when a chance
came to teach physics in the island of Corsica. It was
this stay in Corsica which finally confirmed him in his
devotion to natural history. Not only the greatly in-
creased opportunities for observation, but a fortunate
meeting with the naturalist Moquin-Tandon, gave this
direction to his thoughts. Moquin-Tandon, professor
at Toulouse, was a remarkable and versatile man who
has left a strong impression on French science. He
knew how to make zoology and botany interesting, and
to use graceful language in describing the most abstruse
details. It was a revelation to Fabre when this en-
thusiast showed him, in a plate of water, the anatomy
of a snail.
4. ' After a time Fabre returned to the mainland of
France, to teach in the lycee of Avignon. Now began
a period of twenty years, devoted to pedagogy and
HENRI FABRE 283
entomology. It happened that a book by Leon Dufour,
devoted to the natural history of insects, fell into his
hands. The descriptions of insect life at once caused
him to begin observations on his own account. There
was an account of the wasp Cerceris, and its manner of
storing its prey. Fabre soon discovered how much
there was to learn, how extraordinarily inadequate and
fragmentary were the researches of those who stood high
in the world of science. Few had combined the genius
and the patience to see things through, to follow in
every detail the life of these small animals. Thus a
new field opened up before him, and he cultivated it
assiduously until from the infirmities of old age he could
work no more. In all this he was very happy, but
otherwise he was in the midst of difficulties. The
small salary of about $500 a year did not suffice for the
support of his growing family. He was obliged to do
all sorts of miscellaneous tutoring, in order to increase
his means. At length, utilizing his literary skill, he
began to write textbooks of elementary science, and
these in due time yielded a fair income. Thus it
eventually became possible, when harassed by those
who could not appreciate scientific teaching, for him to
retire from the duties of the schoolroom and devote
himself to research and writing. He lived in Orange,
but later moved to Serignan, a peaceful and obscure
village, where he could work undisturbed.
5. In this modest retirement, far from the main cur- Fabre's
rents of the world's affairs, Fabre won fame without
seeking it. For many years his writings were well
known to entomologists, but it was not until near the
end of his life that the general public became aware of
his existence. The masters of literature had come to
realize that here was something more than a student of
284 ZOOLOGY
technicalities, — a man who, while discussing insects,
made noble contributions to the literature of France.
Fabre's poetical and romantic instincts, which repelled
some of the rigidly scientific, naturally appealed to
literary men. The modern student of comparative
psychology does not employ the language of the Sou-
venirs entomologiqueSy with its strong suffusion of human
emotions. The question has naturally arisen, can we
accept Fabre as a contributor to technical science ?
We can and must, for his observations are the best in
his special field, but we may make allowances for the
language. The controversy is an old one, with many
aspects. To make nature live and move in literature
is to see it with human eyes, — the only eyes we have ;
but we cannot do this and preserve an attitude of cold
scientific detachment. In the hope of escaping from the
human bias, we describe phenomena in scientific
phrases, which possibly often do no more than decently
cover the nakedness of our ignorance.
The festival 6. Thus it came about that on the third of April,
atSerignan 1910, there was held a festival in the sleepy village of
Serignan. Eminent men, scientific and literary, as-
sembled to do homage to Fabre. A banquet was given
in the large hall of a cafe, and Edmond Perrier, repre-
senting the Institute of France, described in a speech
the life and works of the entomologist. "Moved to
tears by his memories and by the simple and pious
homage at last rendered to his genius, Fabre wept, and
many, seeing him weep, wept with him." The Sou-
venirs entomologiques began to be translated into Eng-
lish, and were widely read on both sides of the Atlantic.
They are now to be found in every large library, under
various titles given by the translators and publishers.
HENRI FABRE 285
References
C. V. Fabre, Poet of Science. Century Company, New York.
FABRE, J. HENRI. The Life and Love of the Insect. 191 1. Followed by many
other translations under various titles.
The work of George W. and Elizabeth G. Peckham on the solitary wasps
and jumping spiders best represents the spirit of Fabrian research in
this country.
In using the translations from Fabre, it is necessary to remember that some
errors have crept in, owing to the lack of entomological knowledge on
the part of the translators.
CHAPTER THIRTY-EIGHT
Characters
of Lepidop-
tera
The larva or
caterpillar
LEPIDOPTERA
i. THE Lepidoptera or scale-winged insects (Greek
lepis, a scale, and pteron, a wing) include the butter-
flies and moths. It is a curious thing that in English
we have no single word to include both, in spite of
the fact that few people can distinguish accurately be-
tween them. The old Latin papilio, though trans-
lated butterfly, was any lepidopterous insect ; the same
is true of the German word schmetterling. The scales
which cover the wings of most Lepidoptera are flat-
tened hairs, and on the same insect various transi-
tional states may be found, from the scarcely or not
modified hair to the broad, shinglelike scale. The pos-
session of such scales is not in itself proof that an insect
is lepidopterous ; they may be found, for example, on
mosquitoes. Even the relatively primitive Thysanura
(page 268) have scales. The Lepidoptera, however,
possess two pairs of wings, a sucking mouth, and have
a complete metamorphosis.
Beginning life in the egg, they hatch as caterpillars,
commonly but erroneously called " worms." The cater-
pillar is a remarkable creature, since it contradicts in
so many features the characters of the adult. It is
usually long and cylindrical, with a rounded head and
eight pairs of legs. The anterior three pairs, attached
to the thoracic segments, are the so-called true legs,
representing the six legs of all adult insects. The re-
maining ten legs, attached to the abdomen, are soft
and fleshy, and are sometimes called false legs, though
they are veritable legs and function as such. They
disappear entirely in the adult insect. The cater-
pillar also appears to have no antennae, though there
286
LEPIDOPTERA
287
are in reality very minute ones ; and the eyes, instead
of being compound, are simple and extremely small,
From "Animate Creation "
FIG. 102. The oleander hawk moth, with its caterpillar and pupa. This is a
European species.
arranged in a little group on each side of the head. The
mouth is provided with large mandibles, and hence
the animal, in this stage, agrees with the primitive
mandibulate group. The caterpillar feeds on plant
tissue (a very few species devour other insects), and
growing rapidly, changes its skin at intervals. That
is to say, the skin splits open, and the caterpillar walks
288
ZOOLOGY
out of it, clad in a new skin which had formed under-
neath. Caterpillars and reptiles are not the only
animals which change their skiris ; we do likewise, only
we do it gradually. Every time we wash our hands,
dead skin cells fall away imperceptibly and new ones,
formed underneath, take their place. The caterpillar
is the larva stage, the word "larva" applying to this
stage in any insect, "caterpillar" specifically to the
larva of one of the Lepidoptera.
The pupa The caterpillar, becoming full fed, changes into a
pupa, which may be exposed or in a cocoon, or may be
buried in the ground, according to the species. The
word "chrysalis" was applied to the pupa of certain
butterflies, which shine with a golden luster. From the
pupa emerges the moth or butterfly. The ancients,
observing how many larvae entered the ground and
remained apparently dead all winter, emerging as beau-
tiful moths next year, compared the adult or imago
with the human soul. The buried pupa of course sug-
gested the dead body, from which a perfect being should
emerge on the day of resurrection.
Butterflies 2. The Lepidoptera are divided into several very dis-
tinct groups, of which the butterflies constitute one.
In the butterflies (Rhopalocera) the antennae are knobbed,
whereas in the moths they come to a point. In some
tropical groups this distinction is not perfectly clear,
so that disputes have arisen as to whether certain species
were butterflies or not. Commonly the butterflies are
also distinguished by the fact that they fly by day,
and when at rest hold the wings erect, one against the
other. Neither of these distinctions is reliable, how-
ever, since many moths are day fliers, and the manner of
holding the wings varies in both groups. The butterfly
pupa is not inclosed in a cocoon, as are those of many
LEPIDOPTERA
289
moths, nor is it buried in the ground. The various
groups of moths are distinguished by the structure
of the wings and
mouth, as well as by
the character of the
i
larva. Thus the
geometrids, or earth
measurers, have cat-
erpillars which pos-
sess fewer abdom-
inal legs, and walk
by bending the body
in the shape of a
letter U. Several
families are in-
cluded under the
general term Micro-
lepidoptera, and are
noted for the small
size of nearly all the
species. At the other extreme are the often gigantic
Saturniidae, which include the large Asiatic silk moths,
and the familiar American luna, cecropia, and poly-
phemus moths.
The lowest Lepidoptera show many features in
common with the Trichoptera or caddis flies (page 273),
from primitive members of which the whole order
may be supposed to have .arisen.
3. Lepidoptera are especially noted for the various Protective
characters which, they possess, apparently enabling
them to elude their enemies. Many species show
protective coloration; thus, for example, the red-under-
wing moth, Catocala, when it settles on the bark of a
tree, so perfectly resembles the surface on which it
From "Animate Creation "
FIG. 103. Milkweed butterfly (Danaus archippus).
290
ZOOLOGY
Warning
coloration
Photograph by J. H. Watson
FIG. 104. Grcdlsia Isabella on pine. This moth, which is found only in a limited
area in Spain, and is named after Queen Isabella, is of a delicate pea-green color,
the veins broadly covered with dark red scales. On the pine tree (Pinus maritima),
on which it feeds, its colors produce an effect similar to that of the pine needles.
rests that it is extremely hard to detect it. Some moths
and caterpillars, however, are very conspicuous. Many
years ago the naturalist Bates wrote to Darwin, calling
his attention to an extremely gaudy tropical cater-
pillar of large size, ornamented with red, yellow, and
black. How can such colors be of any advantage, it
was asked ? Must they not betray the larvae to every
passing bird ? Darwin, puzzled, wrote to Wallace, who
suggested that perhaps the caterpillars were distaste-
ful to birds, and if so, the more easily they could be
recognized the better chance they would have of
avoiding the fatal experimental peck.' This has since
been shown to be really the case, and such examples
are classed under the head of warning coloration. Still
more remarkable are the resemblances between dif-
LEPIDOPTERA
ferent Lepidoptera, classed under the head of mimicry. Mimicry
This term is rather unfortunate, because it suggests
intentional imitation, which is absurd, since the in-
sects have no control over their appearance. H. W.
Bates, the naturalist already referred to, called atten-
tion to mimicry as present among the butterflies of
the Amazon region. Certain kinds, owing to their
nauseous qualities, are rarely attacked by birds. Others,
little related, and differing greatly in structure, re-
semble the immune kinds very closely, and so escape,
although perfectly edible. This is called Batesian
mimicry, to distinguish it from Mullerian mimicry,
which was made known by Fritz Miiller. In Mullerian
mimicry different inedible species resemble one another,
and it is supposed gain an advantage from the resem-
blance, because birds which have tasted one and re-
jected it will avoid the other at sight. These phe-
nomena have given rise to a great deal of discussion,
and opinions differ as to their interpretation. It has
been pointed out that in several cases the supposed
mimics do not fly in the same places as the forms they
resemble, and it has been noted that the "protected"
species do in fact suffer from the attacks of various
FIG. 104 a. Agapema anona, a moth of the
family Saturniidse, from Arizona.
FIG. 104 b. Cocoon
of Agapema anona.
292 ZOOLOGY
enemies. Broadly speaking, however, there can be
little doubt that the facts are essentially as Bates and
Miiller indicated, although when we come to details
there are complications and exceptions. The butter-
flies have been in course of evolution for a very long
time, and what they are today depends very largely
on conditions existing in the past, of which we have
little or no knowledge.
Cases are known in which the "protected" butter-
flies, as though conscious of their immunity, fly in a
slow and leisurely manner, almost inviting inspection.
Their mimics, although belonging to another group,
which usually flies rapidly, imitate the leisurely flight.
It is a little difficult for us to believe, as we must be-
lieve, that this "bluff" is wholly unconscious.
References
WALLACE, A. R. Darwinism, Chapter IX.
ELTRINGHAM, H. African Mimetic Butterflies. An expensive book, with
beautiful illustrations, which may be examined in large libraries.
SCUDDER, S. H. The Life of a Butterfly. Henry Holt & Co.
HOLLAND, W. J. The Butterfly Book and The Moth Book. Doubleday,
Page & Co.
CHAPTER THIRTY-NINE
BEES
1. BEES are closely related to the digger wasps, and Origin and
appear to have been evolved from them. So close is the ships of bees
resemblance, in certain cases, that it is difficult at first to
see any distinction. All bees, however, have at least
some plumed or featherlike hairs, while the hairs of the
wasps are simple. Plumed or branched hairs occur also
among the ants, but these are not likely to be confused
with bees. The digger wasps capture insects of various
kinds, and store them in their nests as food for the
young. The bees, on the other hand, are vegetarians,
and their maggotlike young feed on a mixture of honey
and pollen. Certain kinds of bees are parasitic in the
nests of others ; these gather no pollen, but, depositing
their eggs in the cells of industrious species, cause the
latter unwittingly to support their offspring at the ex-
pense of their own. These parasitic bees are often
gaily colored, sometimes resembling wasps, and are
without the scopa or arrangement of pollen-collecting
hairs seen in other species. Although they thus live
at the expense of their neighbors, they prosper less
than the working kinds, and are always relatively
scarce. Indeed, were they to become excessively nu-
merous, both they and their hosts would perish to-
gether, as would a human society, the majority of
whose members got their living by stealing.
2. We do not know when the first bees came into Fossil bees
existence, but very well-preserved examples, showing
the characteristic mouth parts, are found in Baltic
amber,1 which is probably about two million years old.
1 Amber is a fossil resin, which when flowing from the trees entrapped
and inclosed great numbers of insects and other small creatures. These
are now preserved with all their most delicate parts, resembling specimens
mounted in Canada balsam for the microscope.
293
294
ZOOLOGY
Adaptation
to flowers
Habits of
bees
Certainly the bees could not have evolved before the
flowers, though it is likely that primitive flowers were
not dependent on bees for the carriage of their pollen.'
In Africa it has been observed that cycads, a very
ancient type of plants, are apparently pollinated
through the agency of beetles ; and we have fossil
beetles of vastly greater antiquity than the earliest
known bees. Bees are adapted to flowers in two ways :
their mouth parts are so constructed that they can get
nectar from the blossoms, and their hairs, or sometimes
special surfaces on the legs, are suited for the collec-
tion of pollen or mixtures of pollen and honey. In the
leaf-cutting bees and their relatives the under side of
the abdomen is densely covered with stiff hairs, con-
stituting the ventral scopa. Here is accumulated a
mass of usually orange or yellow pollen, which, while
destined for the young, also serves to pollinate the
flowers which the bee visits. That is to say, some of
the pollen gets detached and sticks to the stigma of
the flower, leaving in every case sufficient for the next
generation of bees. Thus the bee does not serve the
flower alone, nor the flower the bee alone, but each
gives to the other, — the bee service or labor, the flower
material or capital. Other bees, serving the flowers
in similar ways, carry the pollen on the legs, while
even the hairs of the head may be dusted with the
powderlike material. The humblebee has a smooth sur-
face on the hind legs, fringed with hairs ; this is known
as the corbicula or pollen basket, and is a specialized
structure for carrying moistened pollen. All the work
is done by female bees ; the male, often differing in
appearance from the female, visits flowers and may
accidentally carry a small amount of pollen, but he is a
born loafer. His motto may well be, a short life and a
BEES 295
merry one, for he has no functions which will justify
old age. Thus the Halictus bees, which burrow in the
Y
From ''Animate Creation "
FIG. 105.. The honey bee (Apis mellifera) : a, queen (female) ; b, worker (sterile
female) ; c, drone (male) . The outline of the front of the head is shown above each
form.
ground, hatch out male and female in the late summer.
The males die, but the females survive the winter, and
may be seen in the spring industriously making their
nests, without any assistance from the other sex. In
the case of the Anthop\ora bees, which construct holes
in banks and are the cliff-dwellers of the group, the
males may be observed to stand at the entrance of
the tunnels. They are easily recognized by the largely
yellow or white face, and it is this face which is exposed
as their round heads fill the orifice. These males are
in fact able to function as front doors, stepping aside
whenever a female desires to enter. In the case of the
social bees, such as the honeybee, there seems to be a
third sex, the worker. The workers are, however,
sterile females, while the drones are the males. The
queen bee is the egg-laying female.
The males being comparatively worthless, it seems The sting
that Nature has not thought it worth while to protect
them with a sting. Only female bees (including workers)
can sting. The sting is a modification of the ovipositor
296
ZOOLOGY
Various
kinds of
nests
or egg layer of more primitive Hymenoptera, and hence
on morphological grounds we could hardly expect to
find it in males.
3. The nests of bees
are very diverse, according
to the species. Very many
burrow in the ground, but
others nest under or on
rocks, on trees, or in stems
of- plants. A group of very
large bees (Xylocopa) works
in wood, and has thus
earned the name "carpen-
ter bees." The pretty
spotted bees called Dian-
thidium make nests of
resin and pebbles ; but
their relatives, the species
of Anthidium, collect woolly material from the stems
of plants. The leaf-cutting bees (Megachilt), found
in almost every country in the world, cut semicir-
cular pieces of leaves with their mandibles, and use
these to line their cells. Frequently they use petals
for the same purpose, though certainly not for orna-
ment, as the young are reared in total darkness. The
Honeybees social bees, including the humblebees * and honey-
bees, have special wax-producing organs on the abdo-
men, and hence are able to make the cells in which
their young are reared, without recourse to the support
afforded by the walls of a tunnel. The comb of the
humblebee is a complex structure, with receptacles
for the larvae (young), and others for honey and pollen.
It is, however, a roughly and loosely constructed affair
1 Hummel in German; "bumblebee" is a corruption.
From Brehm's " Thierleben "
FIG. 106. A wood-boring or carpenter
bee (Xylocopa), with its nest. The
latter is exposed by splitting open the
timber in which it was constructed.
and
humblebees
BEES
297
compared with the beautiful comb of the honeybee, with
its symmetrical six-sided cells. In the great group of
From Brehm's "Thierleben"
FIG. 107. A leaf-cutting bee (Megachile) : a, female; b, male; c, a rose leaf with
parts removed by the bee ; d, a nest in a cavity in a plant stem ; /-», details of the
construction of the cells of a nest ; k, a pupa.
bees we find still preserved representatives of numerous
stages of evolution, from the simple tunnel of the soli-
tary bee, to the complicated nest, with no less com-
plicated habits, of the most completely socialized kinds.
The true honeybees (Apis) are confined to the Old
World, except where they have been introduced by
man. In the tropics of both hemispheres, however,
are numerous species of stingless social bees (Trigona
'and Melipona), mostly of small size. Some of these,
as if to make up for the absence of stings, have the
power of emitting an irritating liquid, and are ex-
tremely pugnacious when disturbed.
4. Just as we find a series of types of nests, so also Mouth
do we find in the mouth parts of bees a beautifully bees
graduated series leading from the wasplike type to
298 ZOOLOGY .
the long-tongued species which visit tubular flowers.
In some of the least specialized bees the tongue is
very short and broad, and notched in the middle,
indicating its primitively double nature. In others it
is daggerlike, and by selecting appropriate species one
may arrange a series with successively longer tongues
until we come to certain tropical bees in which the
tongue is actually longer than the body and when
turned backward projects behind like a tail. On each
side of the tongue are the four-jointed labial palpi.
These palpi or feelers in the lower bees have four
similar joints, but as the tongue elongates, so do the
two basal joints of these palpi, while the two apical
joints remain at the end, still small and unmodified.
The maxillce form external sheaths, and these too bear
palpi, with the maximum number of six joints. In the
higher bees these palpi seem unable to keep up with the
elongation of the other mouth parts, and they become
reduced to five, four, three, or two joints, or even dis-
appear altogether. They follow the law that useless
parts tend to become smaller, but usually remain as
vestiges. It is also to be noted that, as in so many
other cases, the number of parts (as joints of the palpi)
may become reduced, but never increased over the
primitive number.
Wings of So, again, in the wings of bees we find specialization
by reduction. The upper wing of a bee or wasp shows
a thickening on the upper margin, called the stigma.
This may be large, or almost absent. Just beyond the
stigma is an inclosure, bounded by so-called veins,
known as the marginal cell. Below the marginal cell
are other inclosures, often more or less square, the
submarginal cells. The usual number of submarginal
cells is three, but there may be only two, and a small
parasitic bee has only one.
CHAPTER FORTY
ANTS
1. ANTS have always attracted the attention of man- Characters
kind on account of their abundance, wide distribu- ° a
tion, and social habits. They constitute a group of the
order Hymenoptera, and are especially distinguished
by the structure of the abdomen or hind body, which
has one or two modified basal joints, forming nodes or
scalelike structures. It will also be noticed that the
antennae are elbowed or sharply bent, superficially ap-
pearing as if broken. Nearly all ants exist in three
forms, the male, female, and worker. The male and
female have wings, but the latter removes her wings
when she has been fertilized and is about to start a
nest. The workers, which are sterile females, are
entirely wingless. The sting in ants, bees, and wasps
represents and is derived from the ovipositor which
exists in more primitive groups. This ovipositor, or
egg placer, naturally belongs to the female; hence
male Hymenoptera do not sting. Among the ants,
the workers of many genera, .being modified females,
can sting ; but in many other genera this power is lost.
2. Polymorphism is the name given to indicate the Poiymor-
existence of several different forms within the limits phism
of a species. If there are only two forms, — for in-
stance, two sexes differing in appearance, - - we speak
of dimorphism. When there are three forms, as male,
female, and worker, the term trimorphism may be
used. Beyond this comes polymorphism, from the Greek
words meaning " many forms." We also use the adjecti-
val forms polymorphic, dimorphic, trimorphic. Ants are
often highly polymorphic. Frequently the workers
differ greatly in size, and in some species there is a
299
3°°
ZOOLOGY
group or caste known as soldiers, with enormous heads.
These peculiar individuals, which occur especially in
History of
the ant
colony
From Brehm's " Thierleben "
FIG. 108. Ants. 1-8, Formica rufa: i, male; 2 a and b, workers, much enlarged ;
3, female; 4, head of worker ; 5, larva; 6, pupa cases; 7-8, pupa. 9-11, Cam pono-
tus herculeanus: 9, worker; 10, male; n, female.
the genus Pheidole, found commonly under stones, have
brains no larger than those of their small-headed
fellows. In some cases the differences between ants
are due to special causes such as the presence of para-
sites, and do not come under the head of normal
polymorphism.
3. The history of an ordinary ant colony is roughly
as follows : At a certain time of year, differing with
the locality and species, the functional sexes are pro-
duced. These are nearly always winged, and have the
instinct to leave the nest, rising into the air for the
marriage flight. During this period they are attacked
by various enemies, but those which survive return to
the earth, not to leave it again. The males die, but the
females seek a place to found a nest, or sometimes
4NTS 301
return to the nest from which they came. Not rarely
one may find an impregnated female, or queen mother,
recognizable by her large size, occupying a small
cavity under a stone. She has removed her wings, as
though to prevent all temptation to leave home and
duty. She waits patiently for her eggs to mature, and
at length lays them in a small group. From them
hatch the larvae or grubs, which are fed with a secre-
tion produced by the mother. It may be months
before this first brood has been produced and reared to
maturity, and in the meanwhile the female not only
takes no food, but feeds her young at the expense of
her own substance. The individuals thus produced
are small workers, and it is now their duty and occupa-
tion to go forth from the nest on excursions, to hunt
for food for themselves and their exhausted parent.
In this they are successful, being guided by suitable
instincts, and when the queen is properly fed she pro-
ceeds to lay many more eggs. She may live to be
fifteen years old, continually producing eggs, but after
raising her first brood taking no more interest in the
young. These latter are now fed by the workers, who
assume all the duties connected with the colony, except
that of producing eggs. With time, the nest or colony
becomes more populous and more prosperous, and like a
city, it appears to be able to continue almost indefinitely.
The majority of ants nest in the soil, but many, Ants' nests
especially in tropical countries, live in nests built in
trees, or occupy cavities in the stems of plants or in
galls. In Mexico and Central America we find acacia
trees with remarkable enlarged thorns which are hollow
and are inhabited by ants.
4. The ants are not the only inhabitants of their
nests. Just as human habitations shelter domesti-
302 ZOOLOGY
Animals cated animals and pets of various kinds, so the ants
with ants have associated with them a miscellaneous fauna,
known collectively as myrmecophiles (Greek for "ant
lovers "). A very common ant in temperate regions,
known as Lasius, nests under rocks. In the spring
and early summer, if we lift the rocks or stones scattered
on a hillside, we shall probably find the nests, and be
able to examine the more superficial galleries. We
shall see, not only the ants, but frequently numerous
small mealy bugs (Coccida) and plant lice (Apkidida),
which feed upon the roots of plants. The ants evi-
dently regard them as their property, for they seize
them with their jaws and hasten to carry them off to
passages underground. The fact is that these insects
secrete a sugary substance on which the ants feed ;
it is the same substance which, when produced by plant
lice living on trees, falls on the leaves and is recognized
as honey dew. The ants not only keep certain kinds
of coccids and aphids in their nests, but make excur-
sions to visit others which live on various plants above
ground. In tropical countries the best way to find
mealy bugs and scale insects (coccids) is to watch where
the ants are going. If these animals are thus useful
to the ants, how do the latter reciprocate ? Just as
man does in the case of his animals, — they give pro-
tection. Many wasps and other insects feed upon
aphids and coccids, but should they enter an ants'
nest they would at once be attacked. The protection
above ground is not so complete, but collectors of
coccids know to their cost that they are likely to have
their hands attacked by stinging ants, while ants have
been seen to drive away wasps which were seeking to
provision their nests with aphids.
Other creatures in the nests are scavengers, still
ANTS 303
others are parasitic on the ants, while many seem to
take advantage of the protection afforded without
having any special connection with ant life. Indeed,
the ants appear to harbor useful animals, pets, scaven-
gers, and camp followers of all kinds, just as we do.
5. Since the ants have domestic animals, have they Foodofants
any kind of agriculture ? The more primitive ants are
essentially carnivorous and, like savage peoples, live
by hunting from day to day. We find, however, that
various species, such as the bearded ants so common
in the Southwest, have a system of harvesting. The
ancient advice to "go to the ant" and study her wise
prevision, has its basis in this fact. The small ants of
the genus Pheidole gather many seeds ; and, as Wheeler
points out, .the large-headed soldiers, with their power-
ful jaws, become the "official nut crackers of the
colony." It was at one time supposed that some of
these harvesting ants did actually raise crops, but
this proved to be a mistake, and hence the term "agri-
cultural ants," as applied to them, is a misnomer.
Although we are obliged to deny all knowledge of Leaf-cutting
agriculture to the harvesters, there is another group of ****
ants which really do raise crops. In tropical America,
and so far north as Arizona, the leaf-cutting ants are
often observed carrying on their peculiar occupations.
They nest in the ground, but come forth in long pro-
cessions and, ascending the trunks of trees and stems
of herbaceous plants, cut off leaves and carry them
home. Sometimes they will even take small flowers,
and appear as if carrying bouquets. In hot countries
they are often called "parasol ants," because it is fanci-
fully supposed that the leaves they carry seem to pro-
tect their heads from the sun. As a matter of fact
the leaves are carried into the underground chambers,
3<H
ZOOLOGY
Fungus
gardens
where they are reduced to fragments and serve as
culture beds for the growth of particular kinds of fungi
or, as it were, miniature mushrooms. The fungus in
each case starts from material brought by the queen
founder of the colony from her home nest in a special
pocket or pouch in the head. Each kind of leaf-
cutting ant cultivates a particular species of fungus,
and takes every precaution to keep the underground
gardens free from contamination by useless sorts. Thus
these animals have a genuine system of horticulture,
with all regard for the principles of manuring, pure seed,
and clean cultivation.
Honey ants 6. Ants not only store seeds, but there are some
species which know how to put up preserves. The
honey ants, especially to be found in the Southwest,
have peculiar forms of workers whose function it is to
serve as living honey jars. Many kinds of ants eat
nectar and honey dew, and after storing it in some
quantity in their crops, regurgitate it to feed the larvae
in the nests. The honey ants exhibit an extreme exag-
geration of this function. Special workers, destined to
be "repletes," are fed by the others while food is
abundant, and the material accumulates in their
abdomens. After a time the hind part of the body be-
comes swelled and globular, shaped like a pea and of
about the same size. These repletes, thus filled with
so-called honey, never leave the nest, and are to be
found only by digging. The ordinary workers, long-
legged and agile, go forth at night, and are quite un-
like the repletes in appearance. In this strange manner
food is stored up, to serve the whole colony in times of
scarcity. It is a curious fact that this method of ac-
cumulation has developed quite independently in dif-
ferent groups of ants, in localities as far apart as North
America and Australia.
ANTS 305
7. Sometimes more than one species of ant is found Slavery
in a given nest. When this is the case, the association
may be one of essential equality, or it may be that one
species has been captured by and works for another.
The red ant known as Formica sanguined (sanguinea,
bloody) raids the nests of black ants of the Formica
fusca group, and after a battle, carries away the larvae
and pupae. The ants developing from these in the
sanguinea nest live and work there along with their
masters, and the effect of the raid is to increase the
working population. Formica sanguinea has lost none
of the instincts and powers of ordinary ants ; it can
live without slaves, although it rarely does so. An-
other sort of red ant, known as Polyergus, is in a very
different position. It cannot exist without slaves, for
although it is a great fighter, it cannot procure its own
food. The large and remarkable mandibles are fitted
for fighting and seizing other ants, but are wholly un-
suited for any domestic purposes. There are many
other ants, exhibiting various kinds and degrees of
association, social parasitism, and slavery. Wheeler,
reflecting on all these phenomena, is led to remark :
"He who without prejudice studies the history of
mankind will note that many organizations that thrive
on the capital accumulated by other members of the
community, without an adequate return in productive,
labor, bear a significant resemblance to many of the
social parasites among ants. This resemblance has
been studied by sociologists, who have also been able
to point to detailed coincidences and analogies between
human and animal parasitism in general. Space and
the character of this work, of course, forbid a considera-
tion of the various parasitic or semiparasitic institutions
and organizations — social, political, ecclesiastical, and
306
ZOOLOGY
Analogies
and
differences
between
human and
ant society
criminal — that have at their inception timidly strug-
gled for adoption and support, and having obtained
these, have grown great and insolent, only to degenerate
into nuisances from which the sane and productive
members of the community have the greatest difficulty
in freeing themselves." (Ants, page 503.)
8. In spite of so many resemblances between the
social life of ants and mankind, we must note some
important differences. Ant society is conducted by
the female sex, if we include in this term the sterile
females or workers. The males are short-lived, and
have no part in the affairs of the nation. Ants do not
possess the " choice of good and evil," as do men. They
appear to have some power of choice, but in the main
they are governed by instincts, which hold them down
to definite lines of conduct. Thus, as "free agents,"
it would seem that the slaves of the Polyergus might at
any time go off and leave their useless owners to
starve. This is, however, impossible ; their instincts
hold them more effectively than any chains. It must
be confessed that although man is not thus tied down
to the path of custom, he is very largely controlled by
his habits and traditions. There are numerous situa-
tions in human society which ought to be considered
intolerable and are only endured because people have
neither the initiative nor the imagination to break
away from them.
Ants also differ greatly from civilized man in that
they have no idea of progress. The wonderfully pre-
served insect fauna of amber, perhaps a couple of
million years old, includes thousands of ants. These
show that there has been little or no progress in ant
life and organization since that remote time. It must
be remembered, however, that of the total period during
ANTS 307
which the human species has existed, only a small
portion, comparatively speaking, has been marked by
any regular progress.
Reference
WHEELER, W. M. Ants : Their Structure, Development, and Behavior. Co-
lumbia University Press, 1910.
CHAPTER FORTY-ONE
SCALE INSECTS
Peculiarities I. SCALE INSECTS and mealy bugs, technically known
ofCocadae as Coccidg^ constitute a group of Hemipterous insects,
From Brehm's " Thierleben"
FIG. 109. The cochineal insect : a, colony of the insects on a prickly pear plant ;
b, male ; c, female.
but differ in remarkable ways from the other members
of the order. From ancient times it was customary to
utilize the coloring matter obtainable from, certain
small round objects found on oak trees in the region
Kermesasa of the Mediterranean. They were regarded as berries
source oi (kokkos), or called by the Arabic name kermes. For
many centuries the opinion that these objects were of
vegetable origin prevailed, but in 1551 Quinqueran de
Beaujeu published a book on the productions of Pro-
vence (France), in which he clearly explained that they
were insects. The supposed berries, said he, were the
female insects, which produced innumerable very
minute "worms." The latter settled on the twigs, and
grew into berrylike adults. With the discovery of
Mexico, came the report by Francisco Hernandez and
others that on the tuna, or prickly pear, existed a new
sort of coccus, much to be preferred as a source of
red dye. This, which came to be known as the cochi-
SCALE INSECTS 309
nilla, or cochineal, was imported into Europe. The The
cacti on which it fed were brought over, to establish
the cochineal industry, and these plants now abound in
all the Mediterranean countries. So characteristic are
the prickly pears today in the landscape of Greece and
Italy, that artists depicting scenes of classical times
sometimes put them into their landscapes, ignorant of
the fact that these cacti are natives of America, and did
not exist in Europe until brought over to feed the
cochineal.
Other insects of the same group produce wax, while Wax and lac
still others are the source of lac, which is used as a
varnish. The wax and lac are not the insects them-
selves,, but their secretions, which in life serve for pro-
tection. Lac coccids also yield a coloring matter,
known as "lake"; while the name "vermilion" is
derived from the vermes or "worms" developing in the
kermes. All these coloring matters are now largely
superseded by the coal-tar dyes.
2. While the Coccidse are thus beneficial, they also The cottony
include species which are among the most dreaded sca\e°D
pests of the fruit grower, while others injure ornamental
plants. One of the worst of these pests was the cottony
cushion scale (I eery a purchasi), which threatened to
destroy orange culture in California, but was finally
overcome by a beetle (Novius cardinalis), brought
from Australia. The cottony cushion scale is about
the size of a pea, and produces a white, fluted ovisac,
containing the eggs. Vast numbers of these scales
collect on the branches of trees, and suck the sap.
These are the females; the male, not often noticed, is
a small fly with two wings. When this creature came
to be a pest in California, the entomologists found
that it had first been described from New Zealand, but
3io
ZOOLOGY
Howthe
were saved
San Jose
scale
was believed to have come from Australia. In Aus-
tra^a> however, it was not destructive. It was sug-
gested that probably there existed in Australia one or
more natural enemies, which devoured it as fast as it
increased, and so kept it in check. It had reached
America without these enemies, and had been able to
multiply without hindrance. With some difficulty the
Government authorities were able to send a man to
Australia, on what must have seemed to many a wild-
goose chase ; but the result proved the correctness of
the a priori opinions. Natural enemies of the scale
were found in Australia and brought to America ;
and one of these in particular, a red lady-beetle, checked
the plague and soon reduced the pest to comparative
insignificance. Thus the "balance of nature," dis-
turbed by man, was restored.
3. Quite a different sort of coccid is the San Jose
scale (Aspidiotus perniciosus). The Californian city of
San Jose (pronounced ho-say') gives its name to this
notorious pest of orchard trees, but we now know that
it came from Asia. The scale is very small, hardly
larger than a pin's head, and is very hard to detect on
the bark of a tree, unless massed in quantity. Scales
of this type are therefore very easily carried about on
trees, and escape observation until they begin to appear
in the orchards as pests. On account of this, horti-
FIG. 1 10. San Jose scale, showing the winged male form, a larva, and a mature
female with her protective scale ; all much enlarged.
SCALE INSECTS 311
cultural quarantine officers are now stationed at various
ports and examine all consignments of plants arriving.
The number of injurious insects intercepted in this way
is amazing, and much harm is prevented ; though it
seems hard to a passenger from Japan to have his
highly prized little tree destroyed because it has scales
on it which he himself cannot see at all! One needs
entomological knowledge and a lively imagination to
picture the possible evil which may come from such
minute objects. The San Jose scale, which was brought
in before the days of quarantine, represents the extreme
type of Coccid development. The scale is like a little
oyster shell, covering the minute fleshy female insect.
This female has no legs or antennae, but has a large
mouth, designed for sucking the juices of plants. Her
main function appears to be the production of young ;
she is inert, unable to move about, a picture of de-
generation. The young are extremely small, oval
creatures, with six legs and a pair of six-jointed antenna.
For a short time they can run about at will. They
may be blown about by the wind, or may get from tree
to tree on birds or insects. Their free time is short, and
presently they have to settle down, for the rest of their
lives if females, and begin to develop little scales. Some
of them produce males, which are small, flylike insects
with long antennae and a pair of wings. The adult
males have no mouth parts ; they do not eat. Their
sole function is to bring about the fertilization of the
females, and this done, they die.
4. Thus the Coccidae are exceptions to many rules. Evolution of
We say that insects have six legs, but many adult scale Coccidae
insects have none. We say that Hemiptera have four
wings, but female coccids never have any, while the
males have only two, or rarely none. How, then, do
312 ZOOLOGY
we know that these creatures are insects and Hemip-
tera ? We judge by the totality of their characters,
and especially by the young stages, which repeat more
or less the characters of their remote ancestors. In
spite of their extraordinary character, there is no doubt
whatever about their place in the classification. They
are very instructive as examples of evolution by the
loss of characters, accompanying a sedentary and more
or less parasitic existence. The loss of wings finds its
parallel in the lice and bedbugs, which are of course
wingless in both sexes. In the different species of
coccids there are all the stages between well-formed
legs and antennae, and none. In some the adult females
are mere bags of eggs, and to classify them accurately
Sexual ' we are obliged to examine the larvae. The Coccidae
also illustrate in a very remarkable way sexual dimor-
phism. The two sexes of the San Jose scale, if examined
by one unfamiliar with the group, might well be placed
in different orders of insects, — the female immobile
and without legs, antennae, or wings, but with a highly
developed mouth ; the male of an entirely different
shape, with legs and antennae, a pair of large wings,
and no mouth whatever ! It is amazing that the germ
cells of this species should be able to produce such
totally different organisms. We are led to think of
the possibilities inherent in living beings, but perhaps
sometimes never realized. There is one species, the
mussel scale of the apple, which reproduces partheno-
genetically and only very rarely produces males.
Suppose that all coccids developed this characteristic,
and no males were ever produced ; who could ever
guess that locked up in the germ cells of the female was
the potentiality of a being unlike her in almost every
respect !
CHAPTER FORTY-TWO
GRASSHOPPERS AND THEIR RELATIVES
I. THE order Orthoptera (Greek, straight-winged) The
derives its name from the straight or nearly straight Orth°Ptera
upper margin of the front wings or tegmina of many
locusts and grasshoppers. The Greek word orthos ap-
pears also in "orthodox," used to designate straight
or strictly correct opinions. The name, as applied to
the various insects now classed as Orthoptera, is ill-
chosen, since many have rounded wings, while many
others lack these organs altogether. We here accept
the order as limited by the earlier authors, but it ac-
tually contains very diverse elements, and various
efforts have been made to subdivide it. In the most
modern classification the order is restricted to the
locusts, grasshoppers, and crickets, the cockroaches and
other groups being removed from it. When we look Ancient
for evidence on this point in the rocks, we find that Orth°Ptera
insects of the orthopterous type are extremely ancient,
being abundantly represented in the rocks of the
Carboniferous age, which are probably not less than
15 million years old. At the time when the material
which later became anthracite coal was laid down in
Pennsylvania and adjacent states, cockroaches were
the dominant insects. They were of large size and
varied structure, and found food and shelter in the
luxuriant forests of primitive vegetation. During the
same period there also existed insects, large and small,
which are grouped together under the name Protor-
thoptera, or beginning Orthoptera. Some of these
superficially resembled our modern katydids, and had
spots on the wings, as may be seen in the fossils so
wonderfully preserved in nodules at Mazon Creek,
313
ZOOLOGY
Illinois. Thus, at this very early period, the true
Orthoptera were in process of evolution, while the cock-
roaches had already started on a separate path of their
own. When we see a cockroach, however little we
like its appearance or odor, we owe it a certain respect,
as belonging to one of the very oldest families in the
land.
insect music 2. The true or typical Orthoptera nearly always
have the hind legs enlarged, and consequently the
power of jumping ; they also chirp in various ways,
and appear to have been the inventors of music, coming
into existence long before there were any singing birds.
Their cries differ greatly according to the species,
From Brehm's " Thierleben"
FIG. in. A group of cockroaches, showing individuals in various stages of growth.
GRASSHOPPERS AND THEIR RE L AT I FES
315
and experts can often distinguish between closely re-
lated forms by their voices. It is also found that the
sound proceeds from
quite different parts of
the body in different
kinds ; it may be the
legs, the tegmina, or the
abdomen. In no case,
of course, does it come
from the mouth, as with
us. Various students
have tried tO record From Bulletin 67, U.-S. National Museum
OrthopterOUS SOngS in FIG. 112. A tree cricket (Orocharis) : a, fe-
i , • j male: b, male.
musical notation, and
in so doing have brought out some interesting features.
In some cases we find simply the monotonous repe-
tition of a single note ; but in others there is a regular
variation, the sound rising and falling to produce true
rhythm. Sometimes the song is in such a high key
that it is inaudible to some human ears, though seem-
ing loud to others.
3. As might be expected in such a primitive group, Mouth parts
the mouth parts are adapted for biting, not for suck-
ing; and the metamorphosis is "incomplete." By
the latter expression we mean that the infant grass-
hopper, on hatching from the egg, is visibly a grass-
hopper — not a grub, maggot, or wormlike animal.
It is remarkable — as is the case with human infants —
for the relatively large size of its head, and it has no
wings. At this early period of its life it can hop well,
but it is entirely mute. The grasshoppers' children
literally obey the injunction that they should be seen
but not heard. In many cases they avoid even being
seen, owing to their close resemblance to inanimate
ZOOLOGY
Colors of
locusts
objects. As the grasshopper grows, wing pads appear,
and the insect is said to have reached the pupa stage.
The tegmina or superior wings appear as small, more
or less triangular objects, with the anterior or costal
margin upward ; whereas in the adult the costal
margin is downward when the insect is at rest. In this
way it is easy to distinguish a pupa from the adult in
those species which have the adult wings small and
functionless. In the great lubber grasshopper of the
Western foothills and plains there are no wings, na-
ture having seemingly given up the effort to support
the vast body in the air. The winged locusts and
grasshoppers are often remarkable for the bright colors
— red, blue, or yellow — of the hind wings. They
are thus conspicuous in flight, and the question has
naturally been raised why they should be so brightly
colored, seeming to attract the attention of their
enemies, the birds. It is noteworthy, however, that
when pursued they settle on the ground, doubling
back a short distance at the moment of alighting.
When thus at rest, with the bright colors concealed,
they so perfectly resemble the surface of the earth
that the puzzled entomologist often searches for them
in vain, though he thought he saw them alight. It is
even to be noted that particular varieties agree in
color with the rocks ; thus along the front range in
Colorado, where the disintegrating Carboniferous rock
produces red soil, the hoppers are red to correspond.
The bright under wings exposed in flight actually serve
to puzzle the enemy, who has formed a mental image
which suddenly disappears.
4. Naturalists are often asked how to distinguish a
iho°cuPstsSand grasshopper from a locust. There is no essential dif-
ference, but the far-famed locust of Egypt is remarkable
Protective
coloration
Grass-
GRASSHOPPERS AND THEIR RELATIFES
317
for its large size and its powers of flight. There are
many species of these large locusts, which migrate in
From Brehm's " Thierleben'
FIG. 113. The migratory locust of the Old World (Pachytylus migratorius).
vast swarms and sometimes are met with at sea, Rocky
hundreds of miles from land. The Rocky Mountain
locust, on the other hand, is a relatively small insect,
which when observed singly would always be regarded
as a mere grasshopper. In former times this species
used to migrate in incredible numbers, utterly de-
stroying the crops. It is improbable that such great
plagues of grasshoppers will ever again occur in our
country; for the territory in which they bred has been
mainly turned into farms, and the plowing of the land
destroys the eggs. Our abundant and troublesome
grasshoppers today are almost entirely resident or
nonmigratory forms, and these will be diminished in
number as more land passes into cultivation.
ZOOLOGY
Stick and 5. Somewhat related to the locusts are the Phas-
midae, or stick insects and leaf insects. Many are so
extraordinarily like dry twigs as to be very hard to
detect, while others, with broad, green wings, almost
perfectly resemble leaves. In the early days of ex-
ploration, sailors used to tell how, in certain tropical
countries, the leaves fell off the trees, but crawled back
to their places. Such apparently gratuitous lies were
in fact founded on observation, as is the case with many
other strange tales of travelers.
Rather similar to the phasmids, but structurally
very distinct, are the Mantidae or soothsayers. In this
group the front legs are curiously modified, and are
held, as it were, in an attitude of prayer. Consequently
the common species of the Mediterranean region
The praying (Mantis religwsd) has been regarded as a sacred animal,
and is known as the " praying mantis." As a matter
of fact, its apparently pious attitude merely indicates
readiness to spring upon its prey, as a cat springs upon
a mouse, and the voracious creature should properly be
called the " preying mantis." The mantids are so pe-
culiar, that one might well suppose them to be of rela-
tively recent origin, but the evidence of the fossils
indicates that they are extremely ancient. Like the
mantis
From Brehm's " Thierleben"
FIG. 114. A praying mantis, its egg mass and recently hatched young.
GRASSHOPPERS AND THEIR RELATIVES 319
cockroaches, they place the wings over the abdomen
when at rest.
6. The cockroaches or Blattidse constitute a large cockroaches
group of insects, most abundant in the tropics. One
species is extremely common in houses in England,
where it is known as the black beetle, although it is
dark brown, and is not a beetle. In Central America
some of the cockroaches are over 3 inches long and
fully if inches broad. These are repulsive creatures,
but there is a small, delicate green species, often found
in bunches of bananas, which is rather attractive.
Superficially, cockroaches seem to have no head, that
member being hidden under the large thoracic plate.
The broad wings, with very numerous veins, are folded
over one another across the back, presenting a flat
surface from above. The hind legs are not adapted' for
jumping, nor are there any musical organs. The long,
slender antennae have very many joints. Cockroaches
were abundant in later Paleozoic times, many millions
of years ago. A fossil wing is figured on page 151.
Forty-three living species of cockroaches are known
from the United States, but they are mostly Southern,
and ten have probably been introduced through human
agencies.
References
SCUDDER, S. H. Guide to the Genera and Classification of the North American
Orthoptera. E. W. Wheeler, Cambridge, 1897.
WALDEN, B. H. Euplexoptera and Orthoptera of Connecticut. Connecticut
Geological and Natural History Survey, Bulletin 16, 1911.
BLATCHLEY, W. S. Orthoptera of Indiana. Indianapolis, 1903
CHAPTER FORTY-THREE
The noto-
chord
Dorsal
nerve cord
Breathing
by means of
gills
PROCHORDATA AND CYCLOSTOMES
I. THE vertebrates are distinguished from inverte-
brates by the possession of a vertebral column. That
is to say, they possess a so-called backbone, which
consists of a great number of bones, the vertebrae,
arranged in a series. Prior to the development of this
structure, in the very early embryo of all vertebrates,
appears a rodlike element known as the notochord.
It is not cartilage, and does not become bone, but it
occupies the place of the subsequently developing verte-
brae, and has an essentially similar function, that of
stiffening the animal.
In all vertebrates the main nerve cord is dorsal ;
that is to say, it is on the upper rather than the lower
side of the animal, being just above the notochord.
In invertebrates the reverse is true, so that we may say
that the orientation or position of the vertebrates is
reversed as compared with the invertebrates.
Vertebrates breathe in different ways, terrestrial forms
and aquatic ones derived from them (as whales) having
lungs, while primitively aquatic groups possess gills.
The gills are, however, very different from those of
invertebrates in the majority of instances, although the
function of absorbing oxygen from the water is the
same. The young of the lowest types of fishes, and
even the adults of certain amphibians (such as the
Necturus or mud puppy), possess external gills, which
correspond in general structure to those of many
invertebrates. We find, however, that in adult fishes
there is another type of gill, which consists essentially
of an arrangement whereby water, entering through
the mouth, passes out on each side through the gill
320
PROCHORDATA AND CYCLOSTOMES
clefts, between the branchial arches. Animals cannot
break up the molecule of water (H2O) and take the
oxygen ; they have to depend on the small amount of
that gas which is dissolved in the water. Consequently,
if the breathing apparatus is not very adequate, they
may have to live near the surface or in running water.
Various insect larvae with external gills, which live in
running streams, perish from suffocation if placed in
a dish of still water. Now the gill-cleft arrangement
is one for creating a stream, which flows' continually
past delicate tissues full of blood, which are at the same
time largely concealed and protected from injury. It
is evidently an advance in mechanical organization, -
an invention of Nature, as it were.
2. These being the more fundamental characters of The
the vertebrates, we naturally ask ourselves, whence did
they come ? Are they wholly peculiar to these animals ?
Seeking an answer to this question, we come upon a
series of animals which certainly are not vertebrates,
because they possess no vertebral column ; yet they
possess, in greater or less degree, the notochord, the
dorsal nerve cord,- and the gill-slit apparatus. These
creatures belong to entirely distinct groups, typified
by the Amphioxus, the Balanoglossus, and the tunicate
or sea squirt. All are marine, and of comparatively
small size. This series of animals, thus set apart from
the vertebrates and invertebrates alike, is grouped under
the name Prochordata, mainly as a matter of conven-
ience. It is not certain that some of the characters
mentioned may not be found or have existed among the
invertebrates ; thus Professor Patten of Dartmouth
College describes a notochord as existing in a scorpion.
In his opinion the scorpions (a very ancient group,
certainly) are the survivors of the gigantic Eurypterids
322
ZOOLOGY
Tunicates
of early Palaeozoic times, and these Eurypterids he
thinks may be the ancestors of the curious extinct
creatures called "Ostrocbderms," which seem to lead
toward the true vertebrates. However this may be,
no one sees in the living Prochordates the actual types
which gave rise to the vertebrates, but only animals
possessing some of the characters which those ancestors
must have possessed. They show us, in some measure,
how the evolution may have taken place, and represent
the unprogressive remnants of a group, most of which
either died out entirely or evolved to higher things.
They are therefore far more interesting than their
undistinguished superficial appearance would suggest.
3. The Tunicata or Ascidians are marine animals
which in the adult state appear under a variety of
forms, some attached to rocks, others floating in the
open sea. The name "tunicate" is derived from the
tunic or coat forming the outer layer of the animal.
The commoner species, known as "sea squirts," are
found attached to rocks; when irritated they rapidly
123
Drawings by W. P. Hay and R. Weber
FiG. 115. i, lateral view of an ascidian, and 2, a diagram of its anatomy, a, incur-
rent orifice ; b, excurrent orifice ; c, branchial basket ; d, stomach ; e, nervous system.
3, another species of ascidian (Styela).
PROCHORDATA AND CYCLOSTOMES 323
contract, emitting a stream of water. The mouth
leads into a large sac, the pharynx, the walls of which
nerve ganglion
Drawing by W. P. Hay
FIG. 116. Diagram of the anatomy of Appendicularia, one of the Larvacea:
a, lateral view ; b, cross section of tail.
have a more or less latticelike structure, with many
small openings. This is the gill apparatus, and the water
passing through it gives up its dissolved oxygen to the
blood. At the end of the pharynx is the opening of the
alimentary canal. The pelagic or free-swimming Tuni-
cata are very different — more or less cylindrical, and
transparent. Some are quite large, others minute.
These animals were formerly associated with the Mol-
lusca and regarded as a sort of shell-less clams, but the
investigation of their immature stages showed the entire
error of this view. The larva or young stage is a more The larval
or less tadpolelike creature, with a long tail containing a tumcate
notochord. In development, all this gradually disap-
pears by absorption, except in a group of. minute free-
swimming forms constituting the class Larvacea, which
retain the elongate form and notochord through life. In
addition to the characters mentioned, the tunicates have
a dorsal nervous system, so that in several important
respects they are to be associated with the vertebrates
rather than with the typical invertebrate animals.
It is commonly said that the tunicates exhibit de-
generation. This is not quite exact, but it is true that
after seeming in the early stages to promise develop-
324
ZOOLOGY
Balano-
glossus
ment leading to a vertebrate type, they belie all such
expectations and change into a creature of relatively
simple structure and limited activities. They become
specialized in a .new direction, and although they are
efficient and anything but degenerate in their own
particular line, it is impossible for us, who represent
the culmination of the other alternative, to regard them
without a certain sense of disappointment, almost of
reproach. It is also apparently true that following
their special line, they have abandoned all possibility
of extensive and varied evolution in the future.
4. The Balanoglossus is a wormlike animal found in
sand or mud or under rocks in the
sea, not far from the shore. This
general type includes a number of
genera and species, differing in
size, color, and various anatomi-
cal details. Some are orange,
others greenish or purplish. The
name Balanoglossus or "acorn
tongue" is derived from the more
or less acorn-shaped proboscis or
head-like structure at the anterior
end, which is used in burrowing.
Posterior to this is the collar, at
the anterior end of which is the
mouth, leading into a pharynx
with gill slits. At the anterior
end of the digestive tract, pro-
jecting into the proboscis, is a
small structure regarded as a
Drawing by w. P. nay notochord. Hence the animal
FIG. 117. Balanoglossus: p, must be associated with the
proboscis ; m, mouth ; c, collar ; 111111
g, gill slits; a, anus. Prochordata, although wholly
PROCHORDATA AND CYCLOSTOMES
325
unlike any vertebrate type in most of its characters.
The larva or first stage is minute and transparent,
and forms part of the plankton, or floating fauna
of the sea. It has no resemblance to the adult,
but does recall the larva of the Echinoderms, — a fact
of considerable interest, because many naturalists
suppose that the whole prochordate series, leading in
one direction to the vertebrates, may have come from
an animal which belonged to the same group as the
ancestors of the starfish and sea urchins.
5. The Amphioxus (more correctly called Bran- Amphioxus
chiostoma) derives its name from the fact that it is
sharp at both ends. The name is used for any one of
several similar species which burrow in the sand in
shallow bays. They are pallid creatures, shaped like a
small fish, the largest about 4 inches long. Of all the
Prochordates, they show most vertebrate characters.
They have a dorsal nerve cord, but no skull or brain ;
a well-developed notochord, but no vertebral column ;
a pharynx with gill slits, which do not, however, open
on the surface of the body, but lead to a chamber
FIG. 118. Amphioxus (Branchiostoma lanceolatum).
326 ZOOLOGY
through which the water passes, eventually escaping
through a median aperture. The mouth, surrounded by
long, whiskerlike cirri, is on the under surface, and is
without jaws. The alimentary canal possesses a
diverticulum or sac which constitutes a primitive liver,
and represents the stage of development of that organ
found in the early embryos of vertebrates. There are
pigment spots on the dorsal nerve cord which appear
to be primitive organs of vision, while a pit at the an-
terior end seems to represent the beginning of an organ
of smell. Finally, the muscular tissue of the animal
is segmented (the divisions are called "myotomes"),
apparently the beginning of that segmentation which
in vertebrates finds expression in the vertebrae with
their attached ribs. Thus it seems that the intercostal
muscles, which in ourselves lie between the ribs and
serve to expand the chest in breathing, are actually
more primitive than the ribs supporting them. The
Amphioxus, therefore, though not a vertebrate, repre-
sents a very remarkable approach to the vertebrate
type, and does not show the so-called degenerate fea-
tures of the other prochordates.
Cycio- 6. The next stage in evolution, so far as known to us,
famprey's*116 'ls represented by the Cyclostomes ("round-mouths")?
andhag- including the lampreys and hagfishes. These are not
prochordates, neither are they true fishes. They pos-
sess a primitive but genuine brain, with a cartilagi-
nous skull. The notochord is enveloped in a sheath,
but there are no distinct vertebrae. There are paired
eyes, but the nostril is single and median. There is
no lower jaw, and there is no trace of paired fins. The
liver is of the same general type as that of vertebrates
in general. Lampreys li.ve in the sea or in fresh water,
and feed on the flesh and blood of fishes. The peculiar
PROCHORDATA AND CYCLOSTOMES
327
FIG. IIQ. Lampreys.
From "Animate Creation"
round mouth acts as a sucking disk, and enables the
lamprey to hold on to the side of a fish, while it rasps
the flesh with its horny teeth. Fishes with soft scales
are most likely to be attacked, and dense, hard scales
serve as a protection. The hagfishes, which are marine,
actually burrow into the bodies of fishes and become
parasitic. In very ancient rocks in Scotland there
has been discovered a small fossil animal which in
many ways resembles the cyclostomes, having a skull
but no jaws or limbs, but possessing distinctly formed
vertebrae. This extinct form, known as Palaospon-
dylus, suggests that the cyclostome type is a very old
one, although we know next to nothing about its history.
The hard, porcelainlike scales of many ancient fishes
may have been developed partly as a protection against
these predatory creatures.
CHAPTER FORTY-FOUR
THE STRUCTURE OF THE VERTEBRATES
Theverte- i. VERTEBRATE animals may be defined as those
skeleton possessing a vertebral column ; but as we have already
seen, they possess other important characters, some of
which are shared by types lower in the evolutionary
series. The skeleton of a vertebrate, or endoskeleton
(internal skeleton), consists of numerous separate parts,
which support the muscular and other tissues of the
body, and protect the more important organs, such as
the brain, heart, and lungs. In the lowest vertebrates,
such as the sharks, the skeleton is wholly cartilaginous,
consisting of gristle which can be easily cut with scis-
sors or knife. In the bony fishes, such as the salmon or
perch, and in all the higher vertebrates, hard bone is
formed. This bone, however, is laid down in cartilage,
or sometimes (e.g., the flat bones of the skull) in mem-
brane, being formed by cells which secrete lime salts.
Thus even man has first a cartilaginous skeleton, and
it is only in the course of development that it is replaced
by bone. The process of becoming bone is called ossifi-
cation.
From Zittel's " Palteontologie "
FIG. 120. Skeleton of a perch, showing a loosely articulated skeleton of a relatively
primitive kind.
328
THE STRUCTURE OF THE VERTEBRATES 329
2. The bones consist of the vertebra, the skull, and The
the pectoral and pelvic girdles with their appendages, column*1
the limb bones. To the vertebrae are directly articu-
lated the ribs, which in the higher groups join the breast
bone or sternum on the ventral side. In fishes and
snakes there is no sternum. A few other bones occur-
ring in various animals are not directly articulated to the
main skeleton. The replacement of the dorsal elastic
rod by bone necessitated the formation of separate
pieces or vertebrae ; otherwise the then aquatic animal
would have been unable to swim with any success. On
the functional side the case is parallel to that of the
arthropods, which developed separate rings in their
hard chitinous exoskeleton — as seen, for example, in
the centipedes. A typical vertebra consists of a cen-
trum or main body, from which arises above the neural
arch, inclosing the neural canal, containing the spinal
cord. The spinal cord is developed in the embryo
round the primitive groove (the central canal which it
contains is a relic of this), and thus belongs to the ecto-
derm or outer tissue. The vertebral column, on the
other hand, has quite a different origin, from the meso-
derm or middle tissue, but in the course of development
it surrounds and incloses the cord. In many fishes the
notochord remains between the vertebral centra, which
may then be deeply excavated in front and behind ;
such vertebrae are called amphiccelous. In addition to
the characters mentioned, vertebrae frequently exhibit
well-marked dorsal spines and transverse or lateral
processes.
3. The skull consists of a number of bones, which are The skull
for the most part firmly articulated together. The
mandible or lower jaw, which is movable, is not primi-
tively part of the skull at all, but is derived from the
330 ZOOLOGY
first gill arch, which swings into position in the course
of development. Thus it may be said that our posses-
sion of a lower jaw depends on the fact that our ances-
tors were aquatic. The exact number of bones in a
skull depends upon the amount of fusion and modifica-
tion which takes place in development. Thus in the
upper jaw of man there is no separate piece (the pre-
maxilla) in front, except at an early age. This part
completely fuses with the main body of the jaw; but
in various other animals it is permanently distinct.
Pectoral and 4. The pectoral and pelvic girdles serve for the attach-
gkdies ment of the anterior and posterior limbs respectively.
In the lowest fishes (sharks and rays) the girdles are
represented by cartilaginous structures of simple form,
but in higher vertebrates they are more complex, and
are represented by several different bones. In man we
recognize a scapula or shoulder blade, and clavicle or
collar bone, forming the pectoral girdle. The clavicle
is not present in all animals ; thus in the ungiilates or
hoofed animals it is absent. This absence is evidently
due to the loss of the structure, and it has been reported
that traces of it may be found in the embryo of the
sheep. On the other hand, the scapula is compound,
consisting primitively of more than one bone. Near
the concave surface for the articulation of the first bone
of the arm is a process which seemed to the anatomists
of olden times (who possessed a very lively imagina-
tion !) to resemble the head and beak of a crow (cor ax).
Hence they called it the coracoid process. Later on it
was discovered that in various vertebrates (e.g., birds)
the coracoid process is represented by a large and im-
portant bone, to which the name coracoid bone was
given. This coracoid bone represents in fact the ven-
tral portion of the primitive pectoral arch, joining the
THE STRUCTURE OF THE FERTEBRATES 331
sternum at its median end. The clavicle is accessory
to the main arch. In the domestic fowl the coracoid
From Zittel's " Palceoniologie" (after Dotto)
FIG. 121. Skeleton of Iguanodon, an extinct reptile belonging to the group of
Dinosaurs, found fossil in Belgium. The skeleton is much more highly specialized
than that of the fish, the shoulder and pelvic girdles being fully developed, sc,
scapula; co, coracoid bone ; p, pubis; pp, postpubic process; is, ischium; I-V, digits.
can be seen as a relatively thick bone on each side at-
tached to the breastbone, while the united clavicles
constitute the wishbone.
The pelvic girdle consists of homologous parts, except
that there is nothing to represent the clavicle. It be-
comes firmly attached to the ribs, and is in man a very
solid structure, to afford support to the hind limbs.
The cavity for the articulation of the thigh bone or
femur is much deeper than that for the arm bone, and
is called the acetabulum or vinegar cup, because it more
or less resembles the vessel used on the table to hold vin-
egar in ancient times. The flat portion of the pelvic
girdle, corresponding to the scapula, is called the ilium.
332 ZOOLOGY
The limbs 5. The limbs originate as paired fins. In the limbs
of fishes we find a series of bones, supporting a large
number of rays. In the terrestrial vertebrates the
number of parts is reduced and, as it were, stereotyped,
so that five is the typical and maximum number of toes
or digits. In the frog the hind foot has a rudimentary
sixth toe, a relic of the earlier condition when these parts
exceeded five. Occasionally in man and other animals
an extra digit appears as an abnormality. In the horse,
on the other hand, there is only a single functional digit
on each foot, the enlarged toenail being the hoof.
The anterior In the anterior limb the first long bone, articulating
with the scapula, is the humerus. It is followed by two
less robust bones, side by side, the inner being the radius,
the outer or posterior the ulna. We commonly feel our
pulse in the radial artery, close to the lower (distal) end
of the radius. In the wrist is a group of small bones,
collectively known as the carpus. The more primitive
carpus (as in the turtles) consists of a central bone, the
os centrale, three basal bones, and five apical, the last
standing at the bases of the five digits. In man the
three basal bones are preserved, but the centrale has
disappeared, and the fourth and fifth of the apical row
have united to form the unciforme. The accessory
pisiform (pealike) bone has nothing to do with the primi-
tive carpus.
Following the carpus is the series of five digits. The
first bones (in ourselves supporting the palm of the
hand) are called metacarpals ; the others are the pha-
langes.
The In the posterior limb we have corresponding parts :
the first long bone is the femur ; then follow the tibia and
fibula (the tibia being the stout shin bone). The small
bones of the ankle are collectively called the tarsus, and
THE STRUCTURE OF THE FERTEBRATES 333
From Ritchie's "Human Physiology"
FIG. 122. Vertebrate limbs. A is the human leg; B, the human arm; C, the fore
leg of a horse ; D, the wing of a bird ; E, the foot of a bird ; F, the hind leg of a frog ;
G, the wing of a bat ; H, the fore leg of a tortoise.
334 ZOOLOGY
beyond these are metatarsals and phalanges. Man is
peculiar for walking on the whole series from the tarsus
on — the largest of the tarsal bones, the os calcis, form-
ing the heel. When he "trips it on the light fantastic
toe" he reverts to the posture of a remote ancestor.
The alimen- 6. The alimentary canal or digestive tract of verte-
brates does not differ fundamentally from that of all but
the lower invertebrate animals. Even the sea urchins
and starfish have such a canal, with the same two open-
ings for the entrance of food and the ejection of waste,
respectively. The stomach is simply an enlargement
of this canal, provided with special glands which secrete
the gastric juice. The liver, primitively a pouch or sac
arising from the digestive tract, becomes a large and
complicated organ. Even the lungs originate in the
same manner, and are at first simple sacs. At the an-
terior end of the alimentary canal, in the mouth, we find
the teeth. It can be seen in the sharks that the teeth
are structures of the skin, not differing essentially from
the spines which may be found on the outer surface of
the animal. The number at first is very great, but as
evolution proceeds they are reduced and specialized,
and become firmly attached to the jaw bones. Ex-
treme types of specialized teeth, like those of the ele-
phant and the horse, seem to have little in common with
the simple conical structures of many fishes and reptiles.
Many invertebrates possess teeth of different kinds,, but
these are not homologous with those of vertebrates.
The nervous 7. In all vertebrates there is a brain, serving as the
system chief controlling center of the nervous system, and there-
fore of the whole body. The smaller nerve centers,
called ganglia, are relatively very unimportant. The
brain is continuous with the spinal cord, and both emit
a series of nerves which branch and extend to every part
THE STRUCTURE OF THE VERTEBRATES
335
From Zittel's "Palaontologie" (after Claus)
FIG. 123. Skeleton of an Egyptian vulture. Rh, cervical vertebrae ; DM, thoracic
vertebrae; Cl, clavicle; Co, coracoid bone; Sc, scapula; St, sternum; II, ilium;
Is, ischium ; Pb, pubis ; H, humerus ; R, radius ; U, ulna ; CC', carpus ; Me, meta-
carpus ; p', p", p'", phalanges of the three digits ; Fe, femur ; T, tibia ; F, fibula ;
Tm, tarsometatarsus ; Z, toes.
336 ZOOLOGY
of the body. These nerves are different in function ;
afferent or sensory nerves convey impulses to the brain
or cord ; efferent or motor nerves convey them in the re-
verse direction, and are the means whereby muscular
activity is stimulated.
Primitively the brain is a swelling at the anterior end
of the spinal cord, and in the course of evolution it be-
comes divided into three vesicles known as the fore-,
mid-, and hind-brain. These vesicles are hollow, and
the cavities become variously modified. The fore-
brain gives rise to the cerebral hemispheres, which in
man occupy most of the surface of the brain. Anteri-
orly the olfactory lobes, connected with the sense of smell,
are developed. The upper and side parts of the mid-
brain form the optic lobes, having to do with the sense of
sight. The hind-brain forms the cerebellum (little brain)
anteriorly and the medulla oblongata posteriorly — the
latter directly continuous with the spinal cord. If we
take any one of the lower vertebrates, such as a fish or
a frog, we find the organs of immediate sensation well
developed, but that part of the brain which keeps the
record of past experiences is very small. In man, on
the other hand, the part connected with memory and
reflection is very large. Thus the lower vertebrates act
almost wholly in response to stimuli just received,
whereas man's actions depend on past as well as present
experiences. It is possible to predict exactly what a
fish will do under given circumstances, almost as though
it were a mere machine. One cannot make similar pre-
dictions about a man, except in the case of actions still
brought about by reflexes which are not under the con-
trol of the brain. Such reflexes are observed in tickling,
which may produce irresistible kicking or coughing ac-
cording to the part stimulated. Others, like those pro-
THE STRUCTURE OF THE VERTEBRATES
337
ducing movements of the stomach, do not rise into the
field of consciousness. Thus we have : (a) unconscious
-md.
After Wiedersheim
FIG. 124. Brain of a European rabbit. A, dorsal view; B, ventral view; b.o.,
olfactory lobe ; cb', median, and cb", lateral lobe of cerebellum ; cr, crura cerebri ;
ep, epiphysis ; f.p., longitudinal fissure ; f.b., cerebral hemisphere ; hp., hypophysis or
pituitary body; m.b., mid brain; md., medulla oblongata; pv., pons Varolii; i— xii,
cranial nerves.
activities ; (&) conscious activities not or little con-
trolled by the brain ; (c) conscious activities under full
mental control. The proportions of these can be
roughly estimated from a study of the nervous system.
The blood system is not peculiar to vertebrates. The blood
Blood is a fluid containing free cells or corpuscles, which
are of two sorts. The more numerous are rigid and
disklike, and contain hemoglobin, which gives the red
color to the blood. These red corpuscles (which are
really pale yellow when seen singly) are usually ellipti-
cal, but in mammals (except the camel family) they are
circular ; in mammals, also, they are without the nuclei
338 ZOOLOGY
which nearly all cells possess. It has been estimated
that there are about five millions of these corpuscles in a
cubic millimeter of human blood, but the number differs
according to environmental conditions, e.g., altitude.
The less numerous corpuscles are colorless (so-called
white corpuscles) and are amoeboid, resembling minute
protozoa, and like them capable of independent life and
movement, given a suitable environment. The func-
tions of these two types of corpuscles are entirely differ-
ent ; the red carry oxygen through the body, while the
white serve as policemen, attacking and destroying
bacteria and dead tissues.
Thecircuia- 9- The blood is contained in a closed system of ves-
tory system sejs knOwn as arteries, capillaries, and veins, and is pro-
pelled through them by the beating of the heart. Just
as the stomach is an enlargement of the alimentary canal,
so the heart is primitively a mere swelling of a blood
vessel, provided with muscular walls. It is so far inde-
pendent of the main nervous system that its contrac-
tions will continue when it is isolated from the body.
In fishes we find that the blood coming from the various
parts of the body is collected in a sinus venosus, which
has contractile walls. Thence we pass to the auricle or
first part of the heart proper, then to the ventricle. In
sharks and some other forms there is in addition a bulb
(conus arteriosus] with muscular contractile walls at the
beginning of the great blood vessel (the aorta) leaving
the ventricle. In the course of evolution the sinus
venosus and conus arteriosus lost their distinct charac-
ter and function, while the heart became divided longi-
tudinally, so that there were two auricles and two ven-
tricles. Now the blood received from the great vein or
veins enters the right auricle and, passing into the right
ventricle, is pumped into the lungs, from which it re-
THE STRUCTURE OF THE VERTEBRATES 339
turns to the left auricle, and leaves the heart finally
from the corresponding ventricle. The partition be-
From Kitchie's "Human Physiology"
FIG. 125. The "tree of life," indicating the main outlines of the evolution of the
vertebrates.
340 ZOOLOGY
tween the auricles in man is not completed until a late
stage of development, and sometimes the opening,
called the foramen ovate, does not close at all. In such
cases part of the venous blood passes to the left side of
the heart without going through the lungs, and con-
sequently the blood fails to receive enough oxygen and
the complexion is bluish. Fortunately such failures to
complete development are very rare.
All warm-blooded animals have two auricles and two
ventricles. The division of the auricles begins earlier,
in the amphibians ; while the crocodiles, among reptiles,
have two ventricles.
stages of 10. The principal stages in the evolution of the verte-
evoiution6 Crates may be summed up as follows :
a. Development of 'brain and cartilaginous skull,
with paired eyes. (Cyclostomes.)
b. Development of cartilaginous skeleton, with well-
formed vertebrae, pectoral and pelvic arches, and paired
fins ; also paired nostrils. (Elasmobranchs, sharks and
rays.)
c. Development of bony skeleton and scales, also air
bladder. (Bony fishes.)
d. Development of limbs for terrestrial locomotion,
with five (or fewer) digits ; development of lungs in
adult stage, for breathing air. (Amphibians.)
e. Development of eggs with hard shells, which could
be laid on land ; elimination of early aquatic stages.
(Reptiles.)
/. Warm blood, developed independently in birds and
mammals. This necessitated a body covering of hair or
feathers, or (as in the porpoise) a thick layer of fat be-
neath the skin. There was also developed a heat-regu-
lating mechanism, involving the blood system and sweat
glands with suitable nerve control.
THE STRUCTURE OF THE VERTEBRATES 341
g. Anterior limbs become wings ; surface covered
with feathers ; teeth lost in modern forms. (Birds.)
From these nothing further arises.
h. Covering of hair ; in higher forms young nourished
in body of parent. (Mammals.)
i. Upright posture, with freedom of anterior feet as
hands to make tools ; corresponding development of the
brain to guide the work. (Man.)
References
HUXLEY, T. H. Manual of the Anatomy of Fertebrated Animals. D. C. Ap-
pleton Company, New York.
KELLICOTT, W. E. Outlines of Chordate Development. Henry Holt & Co.,
New York, 1913. (Embryology of vertebrates.)
PRATT, H. S. A Course in Vertebrate Zoology. Ginn & Co., Boston, 1905.
(Anatomy of selected types.)
JORDAN, D. S. Manual of the Vertebrate Animals of the Northern United
States. A. C. McClurg & Co., Chicago. Eighth Edition, 1899. (Clas-
sification, with descriptions of the genera and species. The region
covered extends west to the Missouri River.)
GREGORY, W. K. Present Status of the Problem of the Origin of the Tetra-poda
(four-footed animals). Ann. N. Y. Acad. Sci., XXVI, 1915.
CHAPTER FORTY-FIVE
FISHES
Definition i. FISHES may be briefly defined as aquatic verte-
brates in which the skull is well developed, with jaws, and
the pectoral and pelvic girdles are developed, each usu-
ally supporting a pair of fins. Respiration is by means
of gills. Fishes exist in the sea and in fresh waters
throughout the world. Although the remoter ancestors
of fishes were undoubtedly marine, there is some reason
for thinking that the actual evolution of the first fishes
was in fresh water. Even sharks, now characteristically
marine, appear to have formerly lived in fresh water -
as shown, for example, by their occurrence in the nod-
ules of Pennsylvanian age at. Mazon Creek, Illinois.
These were primitive types, little resembling the mod-
ern sharks in the details of their structure ; but there is
a typical shark existing today in the fresh water of Lake
Nicaragua, Central America.
ciassifica- 2.. The classification of fishes has given rise to many
turn of fishes differences of opinion, and is still subject to modifica-
tion. The object sought is to arrange all the fishes in
accordance with their natural relationships, assuming
them to have evolved from a common ancestor. While
there must be a true or ideal classification, accurately
representing the historical facts, it is hardly to be ex-
pected that we shall ever completely attain it, though
we continually move toward it. Regarding the fishes
(Pisces) as a class, we have the following principal divi-
sions :
Sharks and (a) Subclass Elasmobranchii, or the sharks and their
relatives. Some would separate these as a class
distinct from the Pisces. In the true sharks
and rays (or skates) — the latter being broad,
342
FISHES
343
flattened-out sharks — the slitlike gill openings
are five to seven on each side, the skeleton is
From "Animate Creation
FIG. 126. A dogfish, a small species of shark, with two of its young
and two of its egg cases.
cartilaginous, and the skin is beset with thorn- Piacoid
like (placoid) scales, or granules, but in Mus-
telus, the dog shark, with pointed, overlapping
scales. The eggs are large and comparatively
few ; they are deposited in leatherlike cases or
hatched within the body. The teeth of sharks
are characteristic — usually pointed or more or
less serrated, often triangular, and sometimes
very large. They are extremely hard, and con-
sequently are often preserved in the rocks as
fossils. Associated with the elasmobranchs,
but very peculiar, are the Holocephali or Chi-
mseras, which are comparatively rare today, but
Teeth ol
sharks
344
ZOOLOGY
were once more numerous, and are known to be
of immense antiquity. The body is long and
tapering, and the thick head, with its blunt
snout and large eyes, has a most grotesque ap-
pearance. The skull is very peculiar, and the
vertebral column is imperfectly developed. In
the mouth are bony grinding plates instead of
teeth, and it is through the fossilization of these
that we know a good deal about the former
abundance of the group.
Lungfishes (b) Subclass Dipneusti, or lungfishes. The skeleton,
though mainly cartilaginous, shows some tend-
ency toward ossification. There are many
anatomical peculiarities, but the most remark-
able is that of the modification of the air blad-
der into a sac with numerous cellular spaces,
which functions as a lung. Very young indi-
viduals have long, featherlike external gills.
The body is covered with scales, which super-
ficially resemble those of the higher fishes,
though differing in the details of structure. It
is an extraordinary thing that the scales of
Sagenodus, preserved in nodules about fifteen
million years old at Mazon Creek, Illinois, agree
in almost every detail with those of Neocerato-
dus, living today in the rivers of Queensland.
From Dean's "Notes on Australian Lungfish "
FIG. 127. The Australian lungfish, Neoceratodus forsteri.
FISHES 345
The living lungfishes are the Australian Neo-
ceratodus or barramunda, the Lepidosiren of
South America, and the Protopterus of Africa.
(c) Subclass Teleostomi, or true fishes. Some include TheTeieo-
the lungfishes with these ; others separate out Jnwteh'es
additional subclasses for certain ancient types
surviving in few species, including in one the
curious African genus Polypterus, in another the
sturgeon and the paddlefish. It is difficult to
define the Teleostomi, as they are so numerous
and diverse, but the skeleton is at least partly
bony ; there is only a single gill opening on each
side, leading to gill arches on which are gill fila-
ments ; and there is a swim bladder, which may
disappear with age. In the higher forms, with
wholly bony skeleton and stiff fin rays, the pelvic
girdle approaches the pectoral one, so that the
pelvic fins may be directly below the pectorals.
Thus it is possible to arrange the multitudes of
fishes in groups representing different degrees of
specialization, and it is not necessary to know
much about the subject to perceive that a
perch stands higher in the series (i.e., is more
remote from the common ancestor) than a
herring. It is also evident that the land verte-
brates (amphibians) could not have arisen from
the higher fishes : first because of the position
of the fins in the latter, and secondly because
the structure corresponding to the lungs in
these fishes has been modified into the swim
bladder.
3. Agassiz recognized a large group of fishes, nearly Ganoid
all extinct, which he called Ganoids. The name is de- fishes
rived from ganos, brightness (Greek), in allusion to the
346
ZOOLOGY
shining, smooth plates covering the body. A typical
example is found in the living African genus Polypterus,
^^ /& j£? s& ^
From Perrier's "Traite de Zoologie "
FIG. 128. Polypterus bichir. River Nile.
twelve species of which inhabit the rivers of that conti-
nent. The surface of these fishes is hard and porce-
lainlike, and is composed of scales of which the exposed
portions are diamond-shaped. On removing these
scales from the body, it is seen that each has a peg,
which fits into a socket in the scale next to it.
We now know that the group of ganoids is artificial ;
that is to say, it associates together fishes which are not
nearly related, and keeps apart those which should be
more nearly associated. The Polypterus is a very old
type, a member of a large and once dominant group
called Crossopterygii, showing certain resemblances to
the lungfishes and the primitive amphibians. Another
sort of ganoid fish is the garpike of the Mississippi Val-
ley. This is entirely different from the Polypterus in
many important characters, and falls in a very distinct
group, but it has the characteristic rhomboidal ganoid
Photograph from Am. Mus. Natural History
FIG. 129. Garpike.
FISHES
347
Photograph from Am. Mus. Natural History
FIG. 130. Group showing nesting habits of the bowfin.
scales, though without the well-defined peg-and-socket
arrangement. It is to this type that the term " ganoid "
has been,more especially restricted in recent years.
The bowfin (Amia calva), also of the Mississippi
Valley, is actually nearer to the garpike than the latter
is to Polypterus, though its scales are not ganoid. It is,
however, a very distinct and isolated type, and although
the scales superficially resemble those of many of the
higher fishes, the fine fibrillx or threads composing the
basal part run lengthwise as they do in the lung-
fishes.
The sturgeons (Chondrostei) constitute another iso- sturgeons
lated type surviving from ancient times. They have
large, bony plates on the body,*and the tail is heterocer-
cal — that is to say, bends upward at the end, carrying
the £n on the lower side. This is a feature also ob-
served in the sharks, and less conspicuously in the
bowfin and garpike. It will be noted that these groups
of archaic fishes exist in fresh water, in the large river
systems of continental areas, but not in the sea.
348 ZOOLOGY
Photograph from Am. Mus. Natural History
FIG. 131. Shovel-nosed sturgeon.
The bony 4. Coming now to the typical bony fishes, or Teleos-
tei, we find a bewildering array of families, genera, and
species, both in fresh water and in the sea. Although
certain fishes, such as the salmon, live in both fresh and
salt water, the marine fishes are in general quite differ-
ent from those of rivers and lakes. The great develop-
ment of the modern families seems to have taken place
at the end of the Mesozoic time, when the sea invaded
large parts of the northern continents. In those days
the whole Mississippi Valley, to the very bases of the
present Rocky Mountains, was a great shallow sea, warm
and eminently fitted for the growth and development of
diverse animals. Some of the fishes were very large, the
giant Hypsodon (or Portheus) exceeding any modern spe-
cies of similar type. The scales show us that the fauna
was not so diversified as the modern one, and it was not
until the Tertiary that a number of the higher forms
came into existence. No doubt the various families
originated in different areas, and it was not until much
later that many of them spread over the waters of the
FISHES
349
fishes
earth. Consequently, even if at a given time in the past
all the now existing families had been evolved, not so
many of them would be found in any particular region
as today.
5. The scales of the bony fishes were classified by Scales of
Agassiz as cycloid and ctenoid. Any scale which had a
circular or oval or squarish outline, with the exposed
edge even and free from teeth or spines, was called
cycloid. Whenever the exposed margin showed dis-
tinct prominences resembling teeth, the scale was called
ctenoid or comblike. Agassiz thought that these dis-
tinctions separated great groups of fishes, and to some
extent he was correct, but it is now known that in many
instances species with ctenoid scales are more nearly
allied to others with cycloid, than to particular groups
in which they are ctenoid. In various flatfishes, the
scales are ctenoid on the upper side, cycloid on the lower
side. The fact is that while the cycloid condition is
undoubtedly the more primitive, it may be secondarily
acquired by the loss of the ctenoid features. The case
After drawing by Max M. Ellis
FIG. 132. Cycloid scale of Notropis cornutus, an American freshwater fish;
showing apical radii.*
350
W6LQGY
P/wtograph by J. Arthur Button
FIG. 133. Scale of perch, showing ctenoid margin and basal radii.
is parallel to that of the paired limbs of vertebrates ; fins
are more primitive than feet, yet the whale has ac-
quired fins, although undoubtedly having an ancestor
with legs. It is also easy to observe, when we come to
study fish scales, that the so-called ctenoid scales are of
very different types, often having little in common.1
1 Scales may be prepared for study as follows : Remove them from the
middle of the side of the fish, trying to avoid regenerated scales, which have
the central sculpture imperfect ; place them, while wet, on a glass slide, first
removing the skin which covers the part which was exposed ; put on a square
cover glass, or if the scales are large, a second slide ; use a clamp to hold down
the cover glass, or two or three^ if a second slide has been used ; put on two
FISHES 351
Photograph by J. Arthur Hutton
FIG. 134. Cycloid scale of herring, showing transverse radii.
A further examination of ctenoid or cycloid scales
shows various interesting features. The surface is
marked with numerous fine lines, which are usually con-
centric, but in some cases transverse or longitudinal.
These are the circuli; they are not growth rings, as
some have supposed. There are, however, more or less
distinct rings called annuli, due to irregularities of
square gummed labels, each overlapping one side of the cover glass, or if a
second slide is used, the labels may bind together the ends of the slides;
write the data on the labels. After a day or two the scales will be dry, and
the clamps may be removed. The scales will remain in place without further
attention.
352 ZOOLOGY
growth ; these have been much studied of late, because
it appears that they may be used to interpret the past
history of the fish. In the case of salmon, especially,
the study of scales has thrown light on the life history,
and has come to be of practical importance in relation
to the regulation of the fishing industry. The salmon is
a migratory fish, and the different surroundings affect
the growth of the scales, and are recorded in the annuli.
It has even been possible to infer that an extinct fish
used to migrate, from a study of its scales. In addi-
tion to the marks just described, there are often radi-
ating (occasionally transverse) lines (radii) representing
grooves. These may extend in every direction from
the nucleus of the scale, or may be all basal, or all apical ;
or apical and basal, but not lateral. In typical ctenoid
scales, there are nearly always strong basal radii, and
where they reach the margin the latter is often crinkled,
producing a scalloped effect. Taking all these different
characters together, it is often possible to classify a fish
if we have no more than a single scale from the middle
of the side, where the characters are best shown.
6. Some of the principal groups of bony fishes are the
following :
Salmon, M Isospondyli. Marine and fresh-water fishes with
trout, and soft fins ancj tjie pectoral and pelvic fins far
herrings ' *\
apart. The group is a large one, with very
diverse families, the most important being the
herrings and their relatives, and the group in-
cluding the salmon and trout. The latter are
especially distinguished by the second dorsal
fin, a little fin above the root of the tail. Some
other fishes have such a fin, but they have
either very different scales, or none at all. The
salmon or trout scale is cycloid, and without
FISHES 353
Photograph from Am. Mus. Natural History
FIG. 135. Common herring (Clupea).
radii. In the herring group, some species have
cycloid scales, others ctenoid scales ; but when
the scales are ctenoid, they are still very differ-
ent from those of the fishes higher in the series.
A remarkable feature of many of the herring
family is the transverse circuli and radii of the
scales, running across from side to side. These
features may be seen very well in the scale of
the common herring. This peculiar structure
is evidently extremely ancient, as a scale from
the Chico Cretaceous of California, belonging
to a period fully five million years ago, is just
like that of a herring of the genus Pomolobus.
(b) Apodes (literally "without feet," rneaning with- Eds
out ventral or pelvic fins). The eels and their
relatives, slender and mostly cylindrical fishes,
are found in fresh waters and in the sea. Scales
are present in some forms, absent in others,
but when present are minute and of peculiar
structure. The very young eel is a translucent,
band-shaped creature, so different from the
adult that naturalists formerly gave it a sepa-
rate name. The common fresh-water eel mi-
grates to the sea in winter, and there lays its
354
ZOOLOGY
Catfishes,
suckers, and
minnows
eggs, which give rise to the peculiar larvae, look-
ing something like an Amphioxus, but with a
well-formed head and large eyes.
(c) Ostariophysi. A series of orders, in which the
anterior vertebras are enlarged and modified,
and through them a series of small bones con-
nects the air bladder with the ear. It seems that
the air bladder thus becomes an organ of hear-
ing. The great majority of fresh-water fishes
belong to this series ; only a few (certain cat-
fishes) enter the sea. The catfishes are quite
without scales, and are noteworthy for their
long barbels, slender appendages in the region
of the mouth. The scaly Ostariophysi common
in this country are the suckers (Catostomidce)
and the carps and minnows (Cyprinida). The
suckers may usually be recognized by the long
dorsal fin and the presence of both basal and
apical radii on the scales. The carp family is a
very large one, with numerous small species,
commonly known as "minnows" in the
Photograph from Am. Mus. Natural History
FIG. 136. Common bullhead or catfish.
FISHES 355
Photograph by E. R. Sanborn, N.Y. ZooL Soc.
FIG. 137. Carp (Cyprinus carpio).
streams of the eastern United States. The
goldfish belongs to this family ; in its wild form
it is dark, the gold variety existing only in a
state of domestication. The case recalls that
of the canary, the wild form of which is a dull-
green bird. These conspicuous and beautiful
forms have arisen as variations, and have been
conserved by man, who admired them. The
Japanese have also obtained in a similar manner
many strange and grotesque forms of goldfish,
which would have no chance for success in the
struggle for existence in the wild state.
(d) Haplomi. The pikes (Esocidce) and the killi- Pikes and
fishes (P&ciliida) are common fresh-water
forms. Some of the latter are excessively
abundant in certain localities, and are very im-
portant as destroyers of mosquito larvae. The
pikes will be recognized by the elongate snout,
356 ZOOLOGY
and the single dorsal fin placed far back over
0 the base of the tail. The Pceciliidse are rela-
tively small, often spotted or striped, with the
single dorsal fin nearly always posterior to the
middle, and the caudal (tail) fin rounded or
squared (truncate), not bifurcated. The scales
are cycloid, with strong basal radii.
Spiny-rayed (e) Acanihopterygii. Spiny-rayed fishes ; generally
known by the anterior position of the pelvic
fins, and the rays of some of the fins hard and
spinelike. The scales are generally ctenoid,
with not merely marginal teeth, but a consid-
erable area covered with fine projections or
variously modified. Such scales usually have
strong basal radii, arranged in a fanlike manner,
and the basal margin is likely to be scalloped.
When a typical spiny-rayed fish, of which the
perch or the sea bass may be taken as an
example, has been thus defined, it is necessary
to state that within the group as now recog-
nized are many exceptions. There are, first of
all, the relatively primitive families, such as
the flying-fish group, in which the scales are
wholly cycloid. These strange fishes have the
pectoral fins enormously enlarged, serving as
organs of temporary flight ; and the lower lobe
of the tail fin is elongated, so that it may be
used to strike the water as the flying fish ap-
proaches its surface, and thus give it a new
start. These fishes are of course specialized
animals in their own way, but not in the direc-
tion of the mass of the acanthopterygians, in
relation to the special characters in which they
are primitive. Aside from the relatively primi-
357
Photograph by E. R. Sanborn, N. Y. Zoo/. Soc.
FIG. 138. Common sunfish (Eupomotis gibbosus), one of the spiny-rayed fishes.
live members of the group, there are others
which lack the special characters for opposite
reasons : they are highly specialized members
of groups which once possessed them, and in
which they have been lost. Thus, for example,
the cycloid scales on the lower side of certain
flatfishes certainly represent a secondary adap-
tation, not a primitively cycloid character.
Certain families are entirely without scales.
The modifications in structure and appearance
are almost endless, producing many grotesque
forms. The flatfishes, adapted for life on
sandy sea bottoms, have one side colored and
. the other, which is away from the light, color-
less. The head is curiously twisted and both of
the eyes are, of course, on the upper or colored
side of the fish. This metamorphosis, gained
through ages of evolution, is passed through in
the development of each individual fish. The
very young have the body symmetrical.
Reference
JORDAN, D. S. A Guide to the Study of Fishes (Henry Holt & Co., 1905), is
the best work of reference.
Flatfishes
CHAPTER FORTY-SIX
Discovery
of the land
by verte-
brates
Amphibians
AMPHIBIANS
1. IN Palaeozoic times, many millions of years ago,
certain vertebrates learned to live upon the land. Al-
ready the land was populated with many kinds of plants
and multitudes of insects. A vertebrate, entering upon
aerial existence, was necessarily subject to certain dis-
advantages, especially the chance of desiccation. This
danger has not yet ceased to menace the lowest land
vertebrates. Thus, on one occasion, it was noticed that
little toads were leaving a roadside ditch in which they
had lived as tadpoles, and, trying to cross the road, were
perrshing in great numbers in the thick dust. The tran-
sition from water to land could not be abrupt. The
eggs were still laid in the water, and the young stages
passed therein ; but emergence on the land opened up a
great new territory, with warmth and food in abundance.
On land, gills were no longer suitable for breathing, and
so their place was taken by internal sacs — that is to
say, by lungs. The lungfishes already have such organs,
so here the transition must have been gradual ; indeed,
it could otherwise hardly have taken place. We know
least about the origin of the legs for terrestrial locomo-
tion, with typically five digits. They are certainly
modified from the paired fins of fishes, but the earliest
known four-footed animals have passed beyond the
transition stage.
2. The first land vertebrates, arising in some such
manner, were amphibians. The word (from the Greek,
meaning "both" and "life") has reference to the life
both in water and on land, to the metamorphosis from
the tadpole to the frog or toad. As a matter of fact, this
metamorphosis does not always occur ; many species
358
AMPHIBIANS 359
are permanently aquatic, while the Alpine salamander
is viviparous. The surface of the body in living species
is smooth or rough, and ordinarily without scales, but
there is a group of legless amphibians possessing minute
scales in the skin. The skull articulates with the atlas,
or first vertebra, by two surfaces or condyles, whereas
all living reptiles, and all birds, have only one. The
mammals have two condyles, as have the amphibians.
Gills are present in the early stages. The red blood
corpuscles are oval, and show distinct nuclei.
3. In Palaeozoic times there existed amphibia, often Palaeozoic
of large size, more or less covered with a dermal armor.
These animals, known as Stegocephalia, had various
fishlike characters, some even having overlapping scales.
In several different localities their footprints have been
found, so that we know the outward form of the five-
toed feet. In some species the anterior feet have only
four toes, showing already a reduction of one from the
primitive number. These Stegocephalia, though ap-
parently well protected, died out entirely at an early
period, leaving the race of amphibians to be continued
by forms which, although often abundant, never reached
the size of the largest of the early group. The groups
now living are the following :
(a) Apoda ("without feet") ; wormlike or snakelike Legless
tropical animals, without any trace of legs, amp ian£
and even without pectoral and pelvic girdles.
They are thus much modified for their burrow-
ing life, yet at the same time they show primi-
tive features, the most interesting being the
presence of small scales in many of the genera.
These scales are imbedded in the skin, and re-
call those of the eels. The eyes are little de-
veloped. The animal, at least in the genus
360
ZOOLOGY
Tailed
amphibians
Photograph by E. R. Sanborn, N. Y. Zool. Soc.
FIG. 139. A water newt (Notophthalmusviridescens).
Ichthyophis of the Oriental region, produces
quite large eggs, and the embryo at a late stage
has long external gills and more or less of a
tail fin. At the time of hatching, the gills are
lost, though the larva is aquatic.
(b) Urodela, or tailed amphibians ; generally known
as salamanders, water dogs, or newts. In the
American genus rather ridiculously called
Siren by zoologists, but "mud eel" by other
persons, the body is snakelike, and only the
anterior limbs are present, while the jaws are
without teeth. This is a specialized or de-
graded form ; the others have teeth in both
jaws, and the legs are all present. The giant
salamander of Japan has been known to reach
a length of over 5 feet. A related fossil form
was discovered in Germany, and was an-
nounced, when described in 1726, as "homo
diluvii testis," the man who witnessed the
deluge ! Salamanders, when terrestrial, live
in damp places, and often breathe largely
through the skin. The so-called water dog of
AMPHIBIANS
361
the United States and Mexico, also known as
the axolotl, is capable of reproducing while still
in the aquatic condition, with external gills.
It has, nevertheless, a mature, terrestrial stage,
in which it appears as a salamander with large
yellow spots or blotches. A remarkable newt,
the Typhlomolgfy is found in underground
waters in Texas. Being permanently in the
dark, it is colorless, and the eyes are hidden and
useless.
Anura ("without tail"), the tailless amphibians; jumping
also called Batrachia Salientia, from their habit
of jumping. These are the frogs and toads, toads
well known to all. The species are numerous,
and differ much in details of structure. The
young are known as tadpoles, and undergo a
curious metamorphosis. The tail is not
dropped off, but absorbed. One group of
Photograph by E. R. Sanborn, N. Y. Zool. Soc.
FIG. 140. Tadpoles of common frog.
362
ZOOLOGY
Photograph by E. R. Sanborn, N. Y. Zotil. Soc.
FIG. 141. African swimming frog.
toads, called the Aglossa, is without a tongue.
The tongue of the frog is a remarkable struc-
ture, attached in front instead of behind, and
capable of being thrust out with great rapidity
to take an insect. Some toads have very
poisonous secretions. Gadow calls attention
to the brilliant red under surface of the fire-
bellied toad of Germany, and shows that this
serves as " warning coloration." He states that
the secretion of the skin is very poisonous, and
he knows of no creature which will eat or even
harm them. He kept large numbers in a viva-
rium, together with various snakes, tortoises,
and crocodiles ; but for years they remained
unmolested, although they shared a pond in
which no other frog or newt could survive.
Hungry water tortoises would stalk them, and
touch them with the nose to get the scent,
AMPHIBIANS
363
when they would immediately withdraw. The
little toads remained motionless, "well knowing
that quick movements, or a show of escape,
would most likely induce the tortoise to a
hasty snap, with consequences to be regretted
by both." The expression "well knowing"
must be taken with reservations, as the action
is doubtless instinctive.
We usually distinguish the frogs from the toads by
the fact that the first are smooth and more generally
aquatic, the second rough
or warty, and in the adult
stage often found far from
water. This separation is
satisfactory only for the
most common forms. The
typical frogs have teeth in
the upper jaw, but none
in the lower jaw, while
the typical toads have no
teeth in upper or lower
jaw. The tree frogs or
Hylidse have more or less
enlarged adhesive disks at
the ends of the toes, which
enable them to climb with
ease and safety.
Photograph by E. R. Sanborn, N. Y. Zool. Soc.
FIG. 142. Giant tree frog.
References
GADOW, H. "Amphibia and Reptiles." Cambridge Natural History, 1901.
MARSHALL, A. MILNES. The Frog; An Introduction to Anatomy, Histology,
and Embryology. Edited by G. H. Fowler (Macmillan). This author re-
marks : "The tadpole is really a fish ; not merely in its habits, but in its
mode of breathing, in the arrangement of its heart and its blood vessels,
and, indeed, in almost every detail of its organization."
PICKERSON, M. C. The Frog Book. Doubleday, Page & Co.
CHAPTER FORTY-SEVEN
Reptiles dis-
tinguished
from
amphibians
Characters
ofReptilia
REPTILES
1. MODERN reptiles include the lizards, snakes, croc-
odiles, and tortoises. In the popular mind they are
confused with the amphibians, but they represent a very
distinct group, much more perfectly adapted to terres-
trial life. Whereas the amphibians lay soft eggs in the
water, and pass at least their early stages in that
medium, the reptilian type is able to produce hard-
shelled eggs, which are laid on land, often in the driest
situations. It is the development of an egg shell which
makes terrestrial life possible, and enables the animals
to exist far from water. The only practicable alter-
native to this arrangement is viviparity ; and it is inter-
esting to see that the birds and mammals, each diverging
from a primitive reptilian group, have adopted the two
possible methods, — the birds continuing the egg-laying
habit, and the mammals, except the most primitive,
giving birth to active young. Even among the reptiles
occasional species are said to 'be viviparous. Such, for
instance, are the snakelike lizard or so-called slow-
worm (Anguis fragilis) and the viviparous lizard
(Lacerta vivipara), both common in England. In these
cases, however, the eggs hatch without being laid or at
the moment of laying, and there is no arrangement for
prolonged nutrition in the body of the parent, as in the
higher mammals. It is interesting to note that the
marine turtles, now well adapted to sea life, come to
land to lay their eggs, thus reversing the procedure of
the amphibian.
2. Reptiles are cold-blooded, with a scaly skin ; they
breathe by lungs, which are much less complex than
those of mammals and birds. In all living forms the
skull has a single occipital condyle; that is, a single
364
REPTILES 365
place of articulation with the first vertebra. In this,
reptiles agree with birds, and differ from amphibians
and mammals. On account of this character, it used
to be supposed that the mammals had arisen directly
from the amphibians ; but more recently fossils have
been found in South Africa which are distinctly reptilian,
and approach the mammals more closely than any
amphibian. These ancient animals, the cynodont or
dog-toothed reptiles, had paired occipital condyles and
the teeth distinctly differentiated into incisors, canines,
premolars, and molars. Presumably they were cold-
blooded and without hair, but we have no knowledge
of anything but their bones and teeth.
3. The classification of living reptiles is relatively ciassifica-
simple, because we have today only the remnants of
a mighty host. Numerous and diverse as are the species
of snakes, lizards, and turtles, they appear insignifi-
cant beside the dinosaurs, plesiosaurs, pterosaurs, and
ichthyosaurs of several million years ago. It was in the
Mesozoic age that the reptiles reached the maximum of
size and diversity of structure, — a time when the
mammals were small and insignificant, apparently
promising little for the future. There still exists in New
Zealand a remnant of the Mesozoic reptilian fauna, the
tuatera of the Maoris, Sphenodon of the naturalists.
This animal, now almost extinct, resembles a large
lizard, the back ornamented with spines. The structure
of the skeleton shows that it has nothing to do with the
lizards, but is related to some of the most ancient fossil
forms ; it is a relic of antiquity which has managed to
survive in an isolated part of the. world, free from com-
petition.
6. Parallel or analogous adaptations are common
among animals, and thus we find that millions of years
366
ZOOLOGY
Adaptations before there were any whales or bats, swimming and
ing and flying mammalia, the reptiles had developed similar
flying
Giant rep-
tiles of the
Mesozoic
age
From Zittel's " Palaontologie "
FiG. 143. Skeleton and body outline of a plesiosaur, restored by R. Owen.
Jurassic of Dorsetshire, England.
types. The plesiosaurs were aquatic and had long
paddles for swimming, in place of legs. As with the
whales, the bony framework of these structures shows
plainly that they are derived from legs, and not directly
from fishlike fins. The pterosaurs, on the other hand,
had long wings and were capable of flight ; yet they
were entirely different from birds or bats. One of these
creatures, found fossil in Kansas, had a spread of wings
measuring nearly 20 feet. It must have been curiously
like an airplane. In spite of their wonderful adaptive
features, all these animals died out ; indeed, we may say
that they disappeared because of their adaptive features,
— they were specialized for particular modes of life, and
when conditions changed, they could not change to meet
them.
5. The dinosaurs (the name means "terrible rep-
tiles") were the gigantic reptiles of the Mesozoic; they
flourished fpr about nine million years, and then became
extinct. The disappearance of these great, stupid
beasts coincides approximately with the rise of the more
modern type of mammals, warm-blooded, active, and
relatively large-brained. Many dinosaurs were herbiv-
orous, feeding on vegetation, and some of these were
REPTILES
367
the largest of all four-footed animals. The long tail
at one end is so like the long neck at the other, with its
.quite insignificant head,
that we have to look
twice at the skeleton of
the Diplodocus to be sure
which is which. The
problem of feeding these
vast creatures must have
been a difficult one, and
they possibly died out for
lack of sufficient food, or
it may have been because
of disease or predatory
enemies. Possibly the
mammals took to eating
their eggS Or yOUng. Eveil ZitteVs " Pala-ontologie " (after H. v. Meyer)
in their prime, these great FlG- J44- Skeleton of a pterodactyl; afly-
, , j M , ing reptile, one of the Pterosauria.
animals had terrible ene-
mies in other dinosaurs, which were carnivorous. This
we know from their sharp and powerful teeth, adapted
for holding and tearing flesh. These carnivorous dino-
saurs had the front legs adapted for grasping or tearing,
but not for walking. They walked on their hind legs,
which were mostly three-toed and resembled more_or
less those of birds. Consequently, when their tracks
were discovered many years ago by geologists ("foot-
prints in the sands of time"), they were supposed to be
those of gigantic extinct birds. The armored dinosaurs
were grotesque creatures, with massive bony armor
plates, and crests or spines covering parts of the body
and tail. They were herbivorous,- and were presuma-
bly protected by their armor from the attacks of the
carnivorous forms. Other dinosaurs had extraordinary
horns, recalling the rhinoceros.
ZOOLOGY
Photograph by E. R. Sanborn, N. Y. Zodi. Soc.
FIG. 145. Giant land tortoise (Testudo mcina) from the Galapagos Islands. Sim-
ilar large tortoises formerly inhabited continental areas, but they have died out,
leaving only a few species on islands.
Tortoises 6. The tortoises or turtles (Chelonid) are easily rec-
ognized by the bony covering of the body and the tooth-
less jaws. The covering or shell consists of a dorsal or
upper portion, called the carapace, and a ventral or
lower plastron. In very young animals the shell is soft,
the plates not being fully ossified. The surface is
covered with horny shields, which according to Gadow
are phylogenetically older than the underlying bony
plates, and do not correspond with them either in num-
ber or position. These shields furnish the well-known
tortoise shell, which is obtained from the hawksbill
turtle (Chelone imbricate) of tropical seas. In certain
river turtles the shell is covered with soft, leathery skin
instead of hard shields; the soft-shelled turtle of the
United States is an example. In the leathery turtle
(Sphargis) the limbs are transformed into paddles, and
REPTILES
369
the same is true of the very different Chelone. These
are independent adaptations to marine life, recalling
the whales and the plesiosaurs. Gigantic land tor-
toises exist in the Galapagos Island and the islands of
the Indian Ocean, where they have been able to survive
on account of their isolation. In former geological
times similar great tortoises were found on continental
areas, — for example, in Colorado and in Egypt.
7. The Crocodilia, or crocodiles and alligators, were Crocodiles
formerly much more numerous than at present. They and aUi
superficially resemble gigantic lizards, but are' struc-
turally quite distinct. There are several living genera,
of which the most familiar are Crocodilus, the true
crocodiles, and Alligator, the alligator. The latter is
distinguished from the former by the broad, rounded
snout. The alligator of the southern United States
may be looked upon as a remnant of an old fauna,
since animals of this genus were formerly much more
gators
Photograph by E. R. Sanborn, N. Y. Zool. Soc.
FIG. 146. Senegal crocodile.
370
ZOOLOGY
Photograph by E. R. Sanborn, N. F. Zool. Soc.
FIG. 147. American alligator (Alligator mississippiensis).
widespread, occurring in Europe and Asia. It used to
be supposed that there were no living Old World alli-
gators, but in 1879 a species was described from China.
The species of living crocodiles are relatively numerous,
and are known on both sides of the world.
Lizards 8. The lizards, or Lacertilia, are extremely numerous
' and widely distributed over the earth. The ordinary
forms are scaly, and possess four well-developed legs,
but there are strangely modified lizards without legs
and even without distinct scales. In such cases the
structure of the skull serves to indicate that they are of
the lizard group, and not the snakes they seem to be.
The snakelike form has been developed independently
among the fishes (eels), lizards, and true snakes. The
Gila (pronounced hee'la) monster (Heloderma) of Arizona
is a poisonous lizard, and appears to possess "warning
coloration," dark brown and orange. The chameleons
are African arboreal lizards, famous "for their power of
changing color. This is done through the movements
REPTILES
371
Photograph by E. R. Sanborn, N. Y. Zool. Soc.
FIG. 148. Gila monster (Helodcrma suspectum).
FIG. 149.
Photograph by E. R. Sanborn, N. Y. Zobl. Soc.
Iguana '(Iguana tuberculata) , a large lizard common in tropical America.
of the pigment in the chromatophores ; it may be
brought near the surface, giving a dark color, or with-
drawn from sight, when the skin appears pale or white.
Chameleons have enormously long tongues, which are
thrust out to capture insects. Lizards have consider-
able power of renewing lost parts, particularly the tail.
A species found in New Mexico has a bright blue tail,
and it can hardly be doubted that this serves to attract
372 ZOOLOGY
a pursuing enemy, which seizes the brilliant object,
while the lizard escapes, to grow a new tail in due time.
Snakes 9. The snakes, called Ophidia, are well known to all
and easily recognized, unless the comparatively rare
legless lizards and amphibians are confused with them.
They are highly specialized animals, in which the limbs
and limb girdles have disappeared. The eyes are with-
out eyelids, which are present in the lizards. Many
snakes are poisonous, but more are harmless, and the
latter should be protected as useful animals, since they
destroy many mice and gophers. The poisonous
rattlesnakes, instead of having warning coloration,
possess a rattle on the tail, by means of which they are
enabled to frighten possible enemies.
References
GADOW, H. "Amphibia and Reptiles." Cambridge Natural History.
STEJNEGER, L. "The Poisonous Snakes of North America." Report of
United States National Museum for 1893.
MATTHEW, W. D. "Dinosaurs." Handbook oj American Museum of Natu-
ral History. New York, 1915.
CHAPTER FORTY-EIGHT
BIRDS
I. ALL birds have feathers, and in this they differ Characters
from every other group of animals. In common with
the reptiles, they lay hard-shelled eggs and have scaly
feet, but they resemble mammals in having warm blood.
The blood is, indeed, warmer than that of mammals ;
in the small, active, singing birds it is at least 10 degrees
(Fahrenheit) above that of man. In all zoological
arrangements the birds (Aves, from the Latin avis, a
bird) follow the reptiles and are followed by the mam-
mals ; but no zoologist believes this to have been the
course of evolution. The mammals and birds arose
independently from reptilian ancestors, and today the
birds are much more reptilian than mammalian in
structure. The feathers must be regarded as greatly
modified scales, and the single occipital condyle at the
base of the skull is a reptilian feature. Although
me.
From Thompson's "Zoology"
FIG. 150. Wing of a dove, showing the bones and important feathers : h, humerus;
r, radius; u, ulna; c, carpals; m.c., carpo-metacarpals ; s.f., secondary feathers;
p.f., primary feathers.
373
374
ZOOLOGY
modern birds are without teeth, very ancient fossil
forms are known in which the jaws have numerous
Feathers
From Owens1 "Comparative Anatomy "
FIG. 151. Young blackbirds, showing the developing feather tracts.
sharp teeth like those of a reptile. The wings are of
course modified anterior limbs, as may be seen by com-
paring the bones with those of other animals. Thus
the beautiful idealistic paintings of angels, in which
these beings are represented with human arms and
hands, and in addition birdlike wings, are contrary to
the teachings of anatomy. The anatomist prefers the
winged sandals of Mercury, which do not offend against
his science.
2. Feathers are not scattered over the bird at random.
Mr. C. W. Beebe figures the sprouting feathers of a
12-day embryo chick, and it can be seen that they are
arranged in rows crossing each other X-wise, just as the
scales of a fish. In the penguins, probably the most
primitive of living birds, the feathers grow on all parts
of the body, but in other birds they occupy definite
areas. These feather tracts can be observed when the
bird is plucked and the points of attachment become
visible ; since they differ in the various groups of birds,
they are of assistance in classification. Although the
BIRDS • 375
feathers are thus attached to definite regions of the body,
they ordinarily cover the surface, and of course prevent
undue loss of heat. It is evident that the warm-
blooded type of organization developed along with the
hair or feathers which helped to conserve the heat and
protect the body from rapid changes of temperature.
In the case of those mammals which have lost the hairy
covering, special arrangements attaining the same end
are found, — thick layers of fat in whales and porpoises,
clothes and houses for man. No birds are as naked as
man, but some have large bare areas. The turkey
vulture, for example, has the head and neck bare,
because its habit of feeding upon carrion would make
it impossible to keep feathers in that region decent.
The colored bare areas about the heads of various birds
appear to serve for ornament.
3. A typical large feather, used in flight, consists of structure
a main shaft, from which arises on each side an oblique ^feathers
series of barbs. These barbs can be seen under the
microscope to be compound, giving rise on each side
to a series of barbules. Thus the structure resembles
that of a bipinnate leaf. The barbules, however, are
provided with little hooks, the barbicels, which hold on
to the barbules of the adjacent barbs and thus keep the
surface of the feather intact, enabling it to resist the
pressure of the air. On closer examination, it is seen
that not only do the various feathers on a single bird
differ in structure, but different kinds of birds have
different feathers. If we knew nothing of birds but
their feathers, it would be possible to construct a fairly
accurate classification. The colors of feathers, like
those of the scales of butterflies, are due partly to pig-
ment and. partly to structure. Pigment is coloring
matter which may be extracted, corresponding to a dye.
ZOOLOGY
Blacks, reds, browns, and usually yellows are due to such
pigments. The bluebirds, however, furnish no more
blue on analysis than the rainbow ; the pigment present
is not blue at all, and the brilliant- effect is due to the
manner in which the surface of the feathers reflects the
light. This can be determined by examining the
feathers by transmitted light under the microscope.
In all such cases the underlying pigment is connected
with the effect produced, but the manner in which the
light is reflected is the more important factor.
Moulting 4. A caterpillar, as it grows, sheds its skin from time
to time ; a snake does the same. The scales of fishes
and reptiles, and the feathers of birds, are renewed
when lost. In birds, however, we find a periodical loss
of feathers, the moult. Feathers, like clothes, wear out,
and were they not renewed the bird would become "a
thing of rags and patches." Moulting renews the
plumage, replacing the old clothes by new and clean
ones. Usually the moult is annual, after the rearing of
the young; but it may occur more frequently. The
feathers do not all come out at once, or the bird would
be disabled. Some water birds, as ducks, do indeed
shed their primary or large wing feathers at once, and
for a while are unable to fly. If the external physical
conditions, such as the amount of moisture, are greatly
altered, the color of the feathers after a moult may be
modified. In the ptarmigan, however, the plumage
regularly. changes to white in the winter, to harmonize
with the snow, on which the bird is almost invisible.
This is not due to a change in the feathers themselves,
but to an alternation of white and brown colors in
successive plumages. Once a feather is formed, it is a
dead structure, like a hair, and cannot be modified,
except through wear or dirt affecting its appearance.
377
In some cases, however, the effect of wear is quite
marked. Thus Beebe points out that in the cock
sparrow the throat feathers have dusky-brown tips, and
as these wear away in the spring the clear black centers
appear. Thus the worn sparrow is more handsomely
marked than the one which has recently moulted. A
very extraordinary case is that of the tropical American
motmot (Momotus), which has long tail feathers, the
ends racket-shaped, with the shafts bare for a con-
siderable distance before the broad tips. It is found
that the birds themselves remove the barbs for a con-
siderable distance, and thus produce this singular effect.
Are we obliged to suppose that these birds, like some
human beings, regularly mutilate themselves for the
sake of fashion ? It seems to be the case that for a
certain distance the barbs are loosely attached, and
hence fall away as the bird preens the tail feathers.
Thus it is possible that a structural peculiarity and an
instinct combine to produce the result, without any
deliberate intention on the part of the bird.
5. The bird's bones are peculiar, yet they agree in Anatomy of
general type with those of other vertebrates. The birds
lungs are supplemented by a series of air cavities, and
even many of the bones in the majority of birds contain
air. In the ostriches and penguins, which do not fly,
there are no air spaces in the bones, but their presence
is not invariable in flying birds. The terns and swifts,
remarkable for their powers of flight, have solid bones.
The sternum or breastbone in flying birds is keeled,
presenting a more or less narrow edge extending out-
ward, as every one who has carved a chicken knows.
This keel affords attachment to the great pectoral
muscles, which are used in flight. The early experi-
ments in aviation, in which men attached winglike
378 ZOOLOGY
structures to their arms, were doomed to failure, be-
cause we have not a keeled sternum. We have the
pectoral muscles, but the greatest athlete could never
develop them as the bird does, having no proper surface
for attachment. Relatively to the size of the bird, the
keel is largest in those which use the wings most actively.
Thus the humming bird, which is incessantly in motion,
hovering over the flowers, has a proportionately im-
mense sternum when compared with the soaring alba-
tross. It is said that the wings of a humming bird
execute from six hundred to a thousand strokes a
minute. In groups of birds which have lost the power
of flight the keel of the sternum also has gone ; such are
the ostrich, cassowary, and apteryx. It was once
thought that all such birds were primitive, belonging to
a type prior to the evolution of flying structures ; but
this view is contradicted by other anatomical evidence.
Senses of 6. Dogs and ants are remarkable for their keen sense
of smell. The horse, with expanded nostrils, sniffs the
breeze. Birds have very little sense of smell, and de-
pend upon their sight. The vulture does not detect the
odor of carrion ; it may be close at hand, and offensive
to the human nostril, but the bird perceives nothing.
Yet from the sky he detects the fallen animal by its
position and lack of motion. Sight suffices where the
most acute nostrils would fail, owing to the distance.
The bird's eyes are not only large, but capable of a
remarkable amount of accommodation; that is, adjust-
ment to near or far sight. It is almost as though the
soaring eagle possessed a telescope, which could be
immediately converted into a microscope as it swooped
upon its prey. The human eye is incapable of such
feats, though possessing the same powers to a limited
extent ; that we see smaller and more distant things than
.
BIRDS 379
any bird sees is due to our invention of instruments,
supplementing by lenses the imperfections of our eyes.
In addition to the peculiarities of the eye itself, birds
have a sort of extra eyelid, the nictitating membrane,
which when drawn across the eye shades it from intense
light. This structure is present, more or less devel-
oped, in many other vertebrates.
7. In any classification of birds, the Archaopteryx Primitive
stands quite apart. Although extinct many millions
of years ago, it is known by two wonderfully preserved
fossils, from the Upper Jurassic rocks of Solenhofen in
Bavaria. Not only are the forms of the bones clearly
indicated, but the impression of the feathers on the
rock remains. The creature is described as of about
the size of a crow, with a small head having toothed
jaws and no true beak. The neck vertebrae were less
numerous than in modern birds. The tail was most
remarkable, with about twenty bones as in a reptile,
but covered with long feathers. There were birdlike
wings, with long feathers adapted for flight, but these
wings had in addition three digits, each with a hooked
claw. The legs were four-toed. This animal was
certainly a member of the class Aves, since it had
feathers ; but in other respects it was intermediate
between birds and reptiles. It is almost the ideal
"link" which evolutionists might have postulated and
hoped to find. Other toothed birds, called Hesper-
ornis and Ichthyornis, have been found in the Creta-
ceous rocks of Kansas. These are not only more recent
than the ArchaopUryX) but are much more like typical
birds.
8. Many other extinct birds are known, though the The great
remains are mostly fragmentary. From the Lower
Eocene of Wyoming comes the gigantic Diatryma,
ZOOLOGY
BIRDS 381
nearly 7 feet high, with a large head and short and
massive neck. The beak is extremely large and com-
pressed, and quite without teeth. The wings were
greatly reduced, as in the cassowary, and the bird was
wholly unable to fly. Although fragments of Diatryma
were discovered in New Mexico in 1874, no one had any
accurate idea of the nature of the bird until Mr. W.
Stein found a nearly complete skeleton in Wyoming
in 1916.
Passing over about three million years, we come to Birds of the
the deposits of the Rancho La Brea, near Los Angeles, asp tbe s
California. Here a great number of bones of mammals
and birds are found embedded in asphalt, which belongs
to the Pleistocene period, and is thousands but not
millions of years old. The very numerous birds, which
were entrapped by the tar which still comes to the sur-
face in the locality, have not yet been fully described.
Their structure was, however, essentially like that of
living species, the modernized type of bird having fully
evolved at the time represented by the deposits.
9. Coming now to the living birds, we can notice
only some of the principal groups, regarded as Orders.
(a) Sphenisciformes. Penguins, a group of marine Penguins
birds, confined to the antarctic regions, ex-
tending as far north as Australia and the
southern end of South America. They are
quite incapable of flight, the wings being re-
duced to flappers which are used in swimming.
These strange birds abound on the coasts of
the antarctic continent. Here the Emperor
Penguin, a large and handsome species, nests
at the coldest season of the year, in darkness,
with the temperature 25 to 75 degrees below
zero.
382
ZOOLOGY
BIRDS
383
(b) Struthioniformes. Ostriches, the largest of exist- Ostriches
ing birds, though not so large as the Dinornis
maximus or moa
of New Zealand,
which became ex-
tinct since man in-
habited that coun-
try. The ostrich,
of which there are
several distinct
races or species,
inhabits the drier
parts of Africa and
Arabia, but was
formerly more
widely distributed
in Asia. As every
one knows, the
wings are unsuited
for flight, while the
legs are long and
powerful, enabling
the birds to run
at a speed of 60
miles an hour,
though this cannot
be maintained for
long. On account
of the valuable
plumes, ostriches
are domesticated,
not only in Africa,
but also in Arizona
and California. FIG. 155. Emeu and young.
FIG. 154.
From Zittel's " Palaontologie '''
A moa (Dinornis), restored,
and three kiwis.
ZOOLOGY
L
Cassowaries
South
American
ostriches
Photograph by E. R. Sanborn, N. Y. ZooL Soc.
FIG. 156. California condor (Gymnogyps calif ornianus) , the largest of North
American vultures, now extremely rare.
(c) Casuariiformes. Cassowaries and emeus. The
emeus are Australian, while the cassowaries
inhabit New Guinea and the adjacent islands.
The wings are quite rudimentary, and there
are no ornamental wing and tail plumes such
as are seen in the ostrich. The cassowaries
have a long crest or helmet on the head, and
the bare skin of the neck and head are brightly
colored.
(d) Rheiformes. The rheas or South American
ostriches ; differing from true ostriches by the
presence of three toes (ostriches having only
two), a feathered neck, practically no tail, and
other characters. Three species are known ;
one of them, Rhea darwinii, was discovered by
Darwin when he made his journey around the
world.
BIRDS
385
Loons and
grebes
(e) Apterygiformes. The Apteryx or kiwi of New The kiwi of
Zealand ; a genus of birds about the size of a
fowl, with long, slender beak and entirely
rudimentary wings. They are somewhat re-
lated to the emeus on the one hand, and the
extinct moas on the other, but constitute a
very distinct and isolated group, surviving in
New Zealand because of the absence of carniv-
orous mammals and other enemies. Five
forms are recognized.
(f) Colymbiformes. Looris and grebes. Here we
first come to a North American group,
well represented in the northern hemisphere.
They are aquatic birds, with webbed or lobed
toes, and capable of vigorous flight.
GO Procellariiformes. Albatrosses and petrels, ma- Petrels and
rine birds with tubular external nostrils. They
are quite distinct from the gulls, with which they
are often associated and which they more or less
resemble. They
are to be found in
mid-ocean, and
nest on isolated
rocky islets, where
they are usually
free from moles-
tation. •
(h) Ciconiiformes.
Storklike birds, a
miscellaneous as-
semblage includ-
ing storks, ibises,
herons, cormo-
their rela-
tives
Pkotosropk by R.R.
N- Y- Zo6L Soc-
FIG. 157. Black-necked stork, or jabiru
(Xenorhynchus asiaticus), found from
rants, pelicans, India to Australia,
386
ZOOLOGY
Storks and
their
relatives
Ducks,
geese, and
swans
Birds of prey
gannets, flamingos, and others. The order
contains very divergent elements, and should
perhaps be divided. They are wading or swim-
ming birds, and are best recognized by the pe-
culiar features of the several genera. They are
associated together on anatomical grounds, and
on the same grounds kept entirely apart from
the cranes and some other birds with which
they might be confused. The birds afford many
examples of convergent evolution, in which
different groups have produced species adapted
to the same general mode of life, and conse-
quently superficially more or less similar.
(i) Anseriformes. Ducks, geese, and swans, fa-
miliar to all. They are most easily recognized
by the form of the bill. The young are
covered with down, and are able to swim soon
after hatching from the egg. Nearly all have
webbed feet.
(/) Falconiformes. Also called Raptores, or birds of
prey ; including the hawks, eagles, vultures, and
their relatives. The hooked bill is character-
istic, though it is found in other birds, such as
the owls and parrots. The owls, though
resembling the hawks in their flesh-eating
habits and the form of the bill, are really not
related to them ; in fact, modern students of
birds associate the owls more closely with the
humming birds than with the Falconiformes.
The national bird of the United States is the
so-called Bald Eagle, Halicetus leucocephalus,
-the specific name meaning "white-headed"
in Greek. It is widely distributed over our
country, but by no means peculiar to it.
BIRDS
387
Photograph by E. R. Sanborn, N. Y. Zool. Soc.
FIG. 158. Mute swans (Olor dor) ; an Old World bird, domesticated for about
seven centuries.
FIG. 159.
Photograph by E. R. Sanborn, N. Y. Zool. Soc.
Canada geese (Branta canadensis) .
388
ZOOLOGY
Fowls and
their
relatives
(k) Galliformes. The
fowls and their
relatives. The
word "fowl"
comes from the
same root as the
German vogel, and
originally meant
simply a "bird."
Words, like the
birds themselves,
become special-
ized. In addition
to a number of
peculiarities in the
skeleton, the fowls
are characterized
by the large crop.
The family Phasi-
anidcz (pheasant
family) includes
the turkey, guinea
fowl, grouse, ptar-
migan, quail,
prairie chicken,
partridge, and
many kinds of
pheasants. It fur-
ther includes the
genusGa/foj, which FlG. l6l. Jungle
Contains the do- native in tropical Asia.
mestic fowl, originally a native of the Oriental
region. Here also comes the peacock (Pavo),
likewise a native of Asia.
Photograph by E. R. Sanborn,
N. Y. Zool. Soc.
FIG. 160. Harpy eagle (Thrasaetus har-
pyia) ; tropical America.
Photograph by E. R. Sanborn,
BIRDS
389
(/) Gruiformes. Cranes and their relatives, includ- Cranes
ing the rails and bustards. They have no true
crop. .
(m) Charadriiformes. Plovers, snipes, curlews, gulls, Plovers,
terns, auks, and pigeons, — a mixed assem-
blage, declared by the anatomists to be more
or less related ! The marked differences be-
tween the several families have to do with the
adaptation of the birds to particular modes of
life — by the sea, on the rocks, or in the forest
- and to particular feeding habits. At the
same time it is remarkable how certain types,
seemingly fitted only for a particular kind of
existence, can modify their habits to suit the
circumstances. Thus the curlew, with its
extremely long and slender curved bill, is
beautifully adapted for extracting mollusks
or worms from deep mud or sand by the water's
edge. In Labrador, however, Dr. Coues
found the birds feeding almost entirely on the
crowberry, the fruit of a hillside plant. The
gulls, which we
think of as ex-
clusively ma-
rine, abound in
the great basin
between the
Rocky Moun-
tains and the
Sierra Nevada;*
and in the early
days of Utah
saved the farm-
ers by devour-
From "Animate Creation"
FIG. 162. The rock dove (Columba lima),
the species from which the domesticated
pigeons have been derived.
390 ZOOLOGY
ing the hosts of grasshoppers. The pigeons,
though typically arboreal, are by no means
universally so; indeed, the domestic bird
is derived from the rock dove, which in-
habits rocky situations on the coasts and in
the mountains of 'Europe. The passenger
pigeon of America is now entirely extinct,
though formerly it existed in countless myri-
ads. The last one died at Cincinnati, Ohio,
September i, 1914. The dodo of the Island
of Mauritius was a peculiar large pigeon, in-
capable of flight. In its isolated home it fared
well until man arrived on the scene and ruth-
lessly destroyed the helpless and clumsy
creatures. By 1693 it appears that the last
dodo had perished.
Cuckoos (n) Cuculiformes. Consisting of two suborders, one
containing the cuckoos, the other the par-
rots. The European cuckoo is noted for its
parasitic habits, its eggs being placed in the
nests of other birds, which know no better than
to rear the alien young. The little cuckoo,
not content to share the nest with its rightful
occupants, will
even push the
latter over the
side, where they
die in neglect
upon the ground.
This is merely
an extreme case
of a not uncom-
mon penOme- From "Animate Creation"
, that of One FIG. 163. The yellow-billed cuckoo.
BIRDS
391
(o)
From "Animate Creation"
FIG. 164. The three-toed woodpecker.
creature taking advantage of the instincts or
habits of another. Slaves are enslaved as much
by their own na-
tures as by the
force and cun-
ning of their
masters ; char-
acters which
were entirely
serviceable un-
der different
conditions, be-
come the instru-
ments of tyranny. The parrots, generally
known by their characteristic bills and brilliant
plumage, are widely spread over the earth, but
mainly confined to warm or tropical regions.
They are fruit and seed eaters, but the kea
parrot of New Zealand has in recent times
taken to killing sheep. The birds alight on
the backs of the unfortunate animals, tear
away the wool, and penetrate the flesh until
they come to the fat in the region of the kid-
neys, which they devour. This transition to a
flesh-eating habit is not so abrupt as we might
suppose, since the parrots of this genus (Nes-
tor) naturally feed on insect larvae. The gray
parrot of Africa is famous for its ability to
talk, and even to sing in a fashion, following
the human voice. The green American par-
rots also are clever talkers.
Coraciiformes. Another strange assemblage, Owls, hum-
containing such divergent types as the .king- JJJS^Jjj!'
fishers, owls, goatsuckers, humming birds, peckers
392
ZOOLOGY
Perching
birds;
sparrows
and their
relatives
swifts, trogons, toucans, and woodpeckers.
They are mainly arboreal, and the young are
born blind and helpless. There are over 550
species of humming birds known, exclusively
confined to the New World. In the Old
World tropics their place is taken to some
extent by the sun birds, which are, however,
Passeriformes, with no real relationship to the
humming birds. The fairy humming bird of
Cuba is the smallest bird known, being only
2| inches long. The swifts, though resembling
the swallows, are not at all closely related to
them ; the swallows are Passeriformes, and are
structurally nearer to the sparrows than to the
swifts.
Passeriformes. The largest and highest group,
which is among the birds what the Composite
are among the plants. Wonderfully successful
in the struggle for existence, presenting in-
numerable families and genera adapted to
different modes of life, feeding on almost every
kind of animal and vegetable matter, but
From "Animate Creation "
FIG. 165. A group of finches.
BIRDS
393
especially fitted
to • live on the
multitudes of
insects and the
seeds and fruits
of the higher
plants. The
name Passeri-
formes is from
Passer, the Eu-
ropean sparrow,
but the term
"sparrowlike
birds" is inade-
quate, and con-
veys too narrow
a meaning. It
is better to think
of them as perch-
ing birds, or song
birds, or finches
and warblers,
but all such ex-
pressions cover only a part of the group. One
great division is known to naturalists as the
oscines, or singing birds, but affinity of struc-
ture compels us to include here so unmusical a
creature as the crow ! So also the birds of par-
adise, which cry wok, wok, wok, in the forests
of the Aru Islands. Other oscines are the
larks, flycatchers, robins, thrushes, wrens,
swallows, waxwings, shrikes, vireos, jays,
creepers, finches, warblers, and bluebirds. The
so-called robin of America is a thrush, very dif-
Photograph by E. R. Warren
FIG. 166. Rocky mountain jay (Perisoreus
canadensis capitalist . This bird belongs to
the family Corvidae, which includes the
jays, magpies, crows, etc. It is common
in the higher mountains of Colorado, and
makes itself very familiar about camps,
amusing the campers by its impudent ways.
It is often called the Camp Robber. Mr.
Warren says: "Like all their family, they
are great hands to carry away and hide
food, and when fed a bird will usually eat a
mouthful or two, take all it can hold in its
bill, and fly off with it, presently returning
to repeat the performance." It is interest-
ing to note that a group of birds is charac-
terized by its habits and psychology, as
well as by the structural characters used
for classification.
394
ZOOLOGY
ferent from the original robin redbreast of
England. The bluebird is typically American,
and is unknown in Europe.
It is scarcely possible to exaggerate the importance of
birds for mankind. Aside from the value of their bodies
as food and their feathers as ornament, they serve as
the constant guardians of our crops. While an occa-
sional hawk may raid the barnyard, and the cherries
may suffer from the robins, all the damage done by
birds to human interests is insignificant in comparison
with the benefits conferred. The normal increase of
injurious insects is sufficient to maintain each kind in
Photograph by E. R. Warren
FIG. 167. Western robin (Planesticus migratorius propinquus), Monument
Valley Park, Colorado Springs, Colorado. This bird belongs to the thrush
family, Turdidse, and is very different from the true robin of England. It goes
southward in the winter, returning early in the spring, though in Colorado a few
birds remain throughout the year. Note the long bill, well adapted to the capture
of cutworms in the soil. In Colorado it has seemed to us that the cutworms were
worst when the ground was long covered by snow in spring, and we have thought
that this might be largely due to the protection they thus gained from the robins. •
BIRDS
395
the presence of its natural
enemies. This condition
is spoken of as the " bal-
ance of nature," and
when it is destroyed by
the elimination of one
side of the balance, — of
the birds, — only disaster
can result. In similar
fashion, birds keep down
the mice and other ro-
dents, and hinder the in-
crease of weeds by con-
suming vast quantities of
their seeds. The preser-
vation of birds thus becomes not merely a matter of
sentiment but a public policy of the highest importance.
Photograph by E. R. Warren
FIG. 168. Western tree sparrow (Spizella
monticola ochracea), Colorado Springs,
Colorado. A winter resident in Colorado,
and a typical member of the large family
Fringillidae, which includes the sparrows,
finches, etc. Note the short, thick bill,
adapted for feeding on seeds, etc.
References
BEEBE, C. WILLIAM. The Bird; Its Form and Function. Henry Holt & Co.,
1906.
KNOWLTON, F. H. Birds of the World. Henry Holt & Co., 1909.
RIDGWAY, R. Birds of North and Middle America. (United States
National Museum.) This is the standard work on the classification
of American birds, but is severely technical.
NEWTON, ALFRED. A Dictionary of Birds. A. C. Black, 1893-96.
WEED, C. M., and DEARBORN, N. Birds in Their Relations to Man. J. B.
Lippincott Company, 1903.
United States Department of Agriculture. Many valuable bulletins on
economic ornithology.
CHAPTER FORTY-NINE
Characters
of Mam-
malia
Egg-laying
mammals
MAMMALS
1. MAMMALS are warm-blooded animals, differing
from birds in lacking feathers and in having two con-
dyles, or articulations of the skull with the first vertebra.
The heart has four cavities, the right and left auricles
and ventricles, and the body is usually covered with
hair. The largest whales, fully 80 feet long, are the
bulkiest of all living animals ; but some mammals are
so small that they can climb a stem of wheat. The
group came into existence during the Mesozoic, and
persisted for ages without very much development.
With the dawn of the Tertiary era the development of
modern mammalian life began, to produce in the course
of three or four million years an enormous diversity of
types, many of them highly specialized and very re-
markable. Eventually man appeared, a mammal
capable of looking back on all this long history and in
some measure grasping its character and significance.
2. The class Mammalia is divided into two subclasses,
the Prototheria or egg-laying mammals and the Euthe-
ria or viviparous mammals. To the former are referred
the fragmentary remains from the Triassic, which give
us the earliest indication of mammalian life. Their
egg-laying habits are of course only inferred, from their
general resemblance to reptilian types. Even so, we
should hardly have the courage to assume the former
existence of oviparous mammals, were it not for the fact
that such creatures still exist in the Australian region.
These living Prototheria constitute the order Mono-
tremata, and include the duckbill (Ornithorhynchus)
("bird bill" in Greek) of Australia, and the so-called
spiny Anteaters (Echidna or Tachyglossus, and Zaglos-
396
MAMMALS
397
sus) of Australia and New Guinea. The egg-laying
habit of the duckbill may be directly traced to its
Li.
Photograph by E. R. Sanborn, N. Y. Zool, Soc.
FIG. 169. Echidna (Echidna aculeata).
reptilian ancestry, but the peculiar ducklike muzzle,
suggesting a bird or a duck-billed dinosaur, is evidently
a special adaptation. The teeth are absent in the adult,
but present at an early stage ; so the animal has evi-
dently had toothed ancestors. The spiny anteaters
are entirely different in appearance, having strong
spines plentifully mixed with the fur, and the skull
produced into a long, slender beak, very suggestive of
a weevil.
3. The Eutheria are divided into the Marsupial and Marsupials;
Placental mammals. The marsupials are in some degree gar<£,an~
intermediate between the Prototheria and the placen- opossum,
and their
tals. The young are born in a very rudimentary con- relatives
dition, and are not nourished by a typical placenta or
base of attachment to the mother. These little-de-
veloped young are nearly always concealed in a pouch or
marsupium, where they are fed with the parent's milk.
398
ZOOLOGY
Placental
mammals
Photograph by E. R. Sanborn,
There are other charac-
teristic features of the
skeleton and teeth, but
within the limits of the
Marsupialia we find the
greatest diversity of out-
ward form and of habits.
Nature, as in so many
cases, produces species
adapted to all sorts of
life and consequently su-
perficially resembling
FIG. 170. Great gr' te"(Macro- OtherS which have Para1'
pus giganteus). lei habits but are not at
all closely related. Australia is the present home of
marsupials, but America also possesses examples, the
most familiar being the opossum. The opossums, of
which there are several kinds, inhabit both North and
South America, living in trees. The survival of so
many marsupials in Australia has been possible be-
cause the region has been cut off from the rest of the
world for ages, and the higher mammals have for
the most part failed to reach it. In Australia we find
the kangaroos, wombats, phalangers, pouched mole,
and many other forms. It used to be said that the
Australian marsupials simulated almost every type of
land mammal except the mole, and it was a matter
of great interest to zoologists when at length a molelike
species (Notoryctes) was discovered.
4. The Placental or higher mammals, including all
the most familiar forms, are nourished within the body
of the mother, and are born in an advanced state of
development. There are numerous orders, of which
the following are the most important :
MAMMALS 399
Photograph by E. R. Sanborn, N. Y. Zool. Soc.
FIG. 171. European hedgehog (Erinaceus Europaeus), one of the larger
Insecdvora.
(a) Insectivora. The Insectivores, or insect eaters, insectivores
include the moles, shrews, and hedgehogs, the
last confined to the Old World. There are
also various isolated and peculiar genera, such
as the Solenodon of Cuba and Haiti, a creature
with a bristly, pointed snout and long, thick
tail. In the popular mind some of these ani-
mals, such as the shrews, are confused with the
mice, but a glance at their sharp, pointed teeth
shows the incorrectness of this association.
They are actually nearer to the bats, different
as these appear. The golden moles of South
Africa, with their metallic-looking fur of golden
bronzy, greenish, or violet shades, are beautiful
and remarkable animals. Representatives have
been found fossil in North America, but are of
course known only by the bones.
(b) Chiroptera. The bats, easily recognized by their Bats, flying
- „. « -» * . . i mammals
powers of flight. Many are insectivorous, but
400
ZOOLOGY
FIG. 172.
Photograph by E. R. Sanborn, N. Y. ZooL Soc.
Barbary lion (Felis led).
Photograph by E. R. Sanborn, N. Y. Zoo'l. Soc.
FIG. 173. Cheetah of hunting leopard (Cynalurus jubatus) . In Asia it is trained
for the chase of the antelope.
MAMMALS 401
others feed on fruit, and are sometimes very
destructive in tropical countries. The vampire
bats of Central and South America are blood-
suckers, and have a peculiar tubular stomach,
adapted for the digestion of blood.
(c) Carnivora. The carnivores, with sharp teeth Carnivores,
and claws. The principal families are :
(i) Felid<2. Lions, tigers, cats, and their rela-
tives. The largest American species are
the mountain lion (or puma) and the
jaguar; the latter beautifully spotted, and
confined to the tropical and subtropical
regions. ,
(ii) Hy<znid<%. Hyenas, belonging to the Ethio-
pian and Oriental regions.
(iii) Fiverridce. Mongooses, civets, etc. The
mongoose was introduced from the Old
World into Jamaica to destroy the rats,
which were seriously injuring the sugar
cane. This it did, but it then turned its
attention to the native birds. The de-
struction of the birds is supposed to have
led to the great increase of ticks in recent
years, though it is proper to state that the
ticks were doubtless mostly or all intro-
duced by man. The case of the mon-
goose in Jamaica is therefore cited as an
illustration of the danger of disturbing
the "balance of nature."
(iv) Mustelidcz.- Martins, weasels, wolverines,
badgers, skunks, and otters. The skunk,
with its handsome black and white fur,
illustrates the theory of warning colora-
tion.
402
ZOOLOGY
Photograph by E. R. Warren, "Mammals of Colorado"
FIG. 174. Long-tailed Texas skunk (Mephitis mesomelas varians), Crested Butte,
Gunnison County, Colorado. The skunk, well known for its odor, differs from
most animals in its striking black and white coloration. This is believed to be
"warning coloration," enabling would-be enemies to recognize the animal easily
and, recalling former experiences, let it alone. Thayer suggests, however, that the
peculiar ornamentation breaks up the outline of the creature, as it were, and is
actually deceptive or concealing. The reader may form his own opinion from the
picture.
(v) Ursidce. The bears. The polar bear is
placed in a distinct genus from the brown,
grizzly, and black bears. The typical
grizzly bear described by Lewis and Clark
appears to be extinct, though related
species exist in North America,
(vi) Procyonidce. Raccoons ; characteristic
American animals. The Asiatic panda
is referred to the same family,
(vii) Canidce. Dogs, wolves, coyotes, and foxes.
The suborder Pinnipedia includes the aquatic carni-
vores, — seals, sea lions, and walruses. The name
"walrus" is a modification of a Scandinavian word
meaning "whale horse." The upper canine teeth in
MAMMALS
403
Photograph by E. R. Sanborn, N. Y. Zoo'l. Soc.
FIG. 175. Black-footed ferret or weasel (Mustela nigripes), representing the family
Mustelidae.
Photograph by E. R. Sanborn, N. Y. Zoo'l. Soc.
FIG. 176. Arctic fox (Alopcx lagopus), found in arctic regions.
404
ZOOLOGY
Pliotograph by E. R. Sanborn,
N. Y. Zool. Soc.
FIG. 177. Hunting dog (Lycaori) ;
South and East Africa.
P Holograph by E. R. Sanborn,
N. Y. Zool. Soc.
FIG. 178. Raccoon dog (Nyctereutes pro-
cyonides) ; Japan and Northeast Asia.
Rodents,
gnawing
mammals
this genus (Odobanus) are modified into immense tusks,
which are used in digging for food and in fighting.
Although the animals are so large, they feed mainly on
bivalve mollusks which -they find in the mud and sand
of northern shores.
(d) Rodentia. Rodents, or gnawing animals, best
known by their peculiar teeth. The canine
teeth are absent, while the incisors grow from
persistent pulps, grinding against one another.
When, as occasionally happens, an upper in-
cisor is knocked out, the lower one opposed to
it continues to grow in a circle, eventually
entering the brain and killing the animal. The
surfaces of the grinding teeth are more or less
flattened, not conical as in carnivores and in-
sectivores. The enamel pattern is often elabo-
rate. Rodents are the dominant and diversified
mammals, in this respect corresponding to the
Passeriformes among the birds. They include
the squirrels^ chipmunks, woodchucks, beavers,
gophers, mice, rats, porcupines, guinea pigs,
and many lesser-known forms. The guinea pigs
MAMMALS
405
Photograph by E. R. Warren, "Mammals of Colorado"
FIG. 179. Pika (Ochotona saxatilis) ; Irwin, Gunnison County, Colorado. The
pikas, often called conies, are found among rocks in the mountains of the northern
hemisphere from Eastern Europe to Western America. Their cheerful cries may
be heard in the summer far above timber line. These animals constitute a very
distinct family, related to the rabbits, but with short ears and no tail.
Photograph by E. R. Warren
FIG. 1 80. Mountain rat (Neotoma cinerea orolestes) ; Colorado Springs,
Colorado. This is a native American rat, easily distinguished by the bushy tail from
the Norway or brown rat, which has been introduced into this country from thie
Old World. The mountain rat is often troublesome in houses, from its habit of
carrying off spoons and other articles. It is sometimes called the trade rat, because
it is said that it always leaves something in exchange for what it takes. The ex-
planation is, that if it is carrying a stick and finds a bright object like a spoon or
fork, it will drop the stick and take the more attractive thing.
406
ZOOLOGY
Photograph by E. R. Sanborn, N. Y. Zob'L Soc.
FIG. 181. Branick paca (Dinomys branicki) ; a rare rodent from Peru,
long known only from a single specimen.
Photograph by E. R. Sanborn, N. Y. Zool. Soc.
FIG. 182. American beaver (Castor canadensis).
MAMMALS 407
are of course not pigs, and they do not come
from Guinea ; the original intention was to say
Guiana pig. They constitute a peculiar
South American genus, and should be known
as cavies (Cavia). The Norway rat and house
mouse are of Old World origin, and have been
introduced into America by man. The native
American rats and mice belong to different
genera, although the genera Castor (beavers),
Marmota (marmots and woodchucks), Sciurus
(squirrels), and some genera of voles are com-
mon to the New and Old Worlds. The prairie
dog (Cynomys, meaning "dog mouse") is
peculiar to North America ; it is essentially a
squirrel modified for life on the treeless plains.
The rabbits, hares, and pikas are usually
placed with the rodents, from which they differ
by having two pairs of incisor teeth in the upper
jaw. Anatomical evidence has lately been
presented, which seems to show that these ani-
mals constitute a group distinct from the true
rodents and of quite independent evolution.
(e) Edentata. Sloths, anteaters, and armadillos, sloths, ant-
all American. The name of the order means
"toothless," and is accurate as applied to the
anteaters, but not to the others. The ground
sloths, now all extinct, but living within com-
paratively recent times, were immense ani-
mals, comparable in size with elephants and
rhinoceroses. There is evidence that a species
of these animals was contemporaneous with
man in South America, and pieces of its skin,
with hair attached, have been discovered in
a cave. The armadillos are remarkable for
408
ZOOLOGY
Photograph by E. R. Sanborn, N. Y. Zool. Soc.
FIG. 183. Sloth (Cholcepus ho/manni) ; Central America. Called the two-
toed sloth, because the anterior limbs have only two functional toes with claws;
but the hind limbs have three claws, as the picture shows.
Photograph by E. R. Sanborn, N. Y. Zool. Soc.
FIG. 184. Great ant-eater (Myrmecophagajubata); tropical America.
MAMMALS
409
\
and man
Photograph by E. R. Sanborn, N. Y . Zool. boc.
FIG. 185. Nine-banded armadillo (Dasypus novemcinctus) ; Southern Texas
and southward.
their mode of reproduction ; a single fertilized
egg gives rise to several individuals, an ex-
aggeration of twinning known as polyembryony.
(/) Primates. Lemurs, monkeys, and man ; mostly Monkeys
tree-inhabiting
animals, with
nails on the
fingers and toes,
instead of claws
or hoofs. The
lemurs today
principally in-
habit Madagas-
car, but primi-
tive species once
existed in North
America, as
shown by their
fossil remains.
The monkeys
are divided into
the Platyrrhine
(broad-nostril)
and Catarrhine
Photograph by E. R. Sanborn,
N. Y. Zool. Soc.
FIG. 186. Lemur (Lemur -oarius) ;
Madagascar.
4io
ZOOLOGY
Hoofed
mammals
Photograph by E. R. Sanborn,
N. Y. Zool. Soc.
FIG. 187. Orang-utan (Simia satyrus) ;
Sumatra and Borneo.
(narrow-nostril)
group, — the for-
mer peculiar to
the New World,
the latter to the
Old World. The
higher apes and
"men are to be
associated with
the Old World
group. The tail
in many of the
South American
monkeys is prehensile ; that is, it can be used
to hold on to a branch, as the animal swings
and leaps through the forest. In the Old
World no monkeys have a prehensile tail, and
in the anthropoid (manlike) apes or Simiidcz
there is no tail at all.
(g) Artiodactyla, or even-toed ungulates (hoofed
animals). The (morphologically) third and
fourth toes are almost equally developed, the
others small or absent. This order includes
the following important families :
(i) Suidce. Pigs, na-
tives of the Old
World.
(ii) Tayassuidce. Pec-
caries, the
American rep-
resentatives of
the pigs.
(iii) Hippo-potamidce. _
?r J FIG. 188. African bush pig (Pota-
HippOpOtamUS mochosrus porcus). Family Suidse.
Photograph by E. R. Sanborn,
N. Y. Zool. Soc.
MAMMALS 411
(the name means "river horse"), now
found in Africa, but formerly extend-
ing to Europe and Asia.
(iv) Camelidce. Camels, found in Central Asia
and North Africa ; and llamas, found in
South America. This discontinuous dis-
tribution of the family would be aston-
ishing, did we not know from fossils
that camels of many genera formerly
abounded in North America.
(v) Giraffidce. Giraffes and the okapi (Ocapia),
now confined to Africa.
(vi) Cervida. Deer, including the reindeer,
caribou, and moose. The name elk
(Alces) properly belongs to the moose,
and is wrongly applied to the American
.wapiti, which is a close relative of the
Photograph by S. S. Flower
FIG. 189. Hippopotamus (Hippopotamus amphibius) in the
Giza Zoological Gardens, Egypt.
412
ZOOLOGY
Photograph by E. R. Sanborn, N. Y. Zool. Soc.
FIG. 190. Axis deer (Axis axis') ; India. Family Cervidae.
Photograph by E. R. Sanborn, N. Y. Zool. Soc.
FIG. 191. Pronghorn antelope (AntUocapra americana)
MAMMALS
red deer of Europe. On the other hand,
the black-tail and white-tail deer of the
United States represent a genus not
found in the Old World.
(vii) AntilocapricUz. The pronghorn antelope
of our Western plains, peculiar to North
America, and not closely related to the
African antelopes.
(viii) Bovidce. Oxen, sheep, goats, musk oxen,
chamois, and true antelopes. The
African and Indian buffaloes are allied
to the oxen, but are quite different from
the American buffalo, properly called
the bison. The latter animal, differing
little in structure from the domestic ox,
though of very characteristic appear-
ance, is represented by a similar species
K-. . Photograph by E. R. Sanborn,
N. Y. Zool. Soc.
FIG. 192. Alpaca (Auchenia pacos)',
Andes of Peru and Bolivia. Family
Camelidae.
P Holograph by E,. R. Sanborn,
N. Y. Zool. Soc.
FIG. 193. Rocky mountain goat
(Oreamnos montanus). Family Bovidae.
414 ZOOLOGY
in Europe. In both cases the inter-
vention of man has been necessary to
preserve the animal from complete
extinction at the hands of man himself.
The mountain sheep of our Western
states are true sheep (Ovis), and are
closely allied to others found in Asia
and the region of the Mediterranean.
The true goats (Capra) belong to the
Old World ; the Rocky Mountain goat
is quite different, and is more nearly
related to the chamois of European
mountains.
(h) Peris sodactyla. Odd-toed ungulates, including
the horses, tapirs, and rhinoceroses. The
rhinoceros group, now confined to the Ethio-
pian and Oriental regions, was once richly
represented in America.
(i) Proboscidea. Elephants, including mastodons
and mammoths.
(/) Sirenia, which are aquatic derivatives of the
ungulate type, as the seals are of the carniv-
orous group. The living forms are the mana-
tee and dugong.
Whales (k) Odoritoceti, or toothed whales, including dolphins
and porpoises.
(/) Mystacoceti, the whalebone whales.
The arrangement of the orders of mammals, as here
given, does not represent the course of evolution in any
accurate way, nor is it possible to do so in a single series.
The evolution of the. mammals has been treelike or
fanlike, the several orders diverging along their own
paths, and not as a rule giving rise to any other. This
can be readily demonstrated by a study of the struc-
MAMMALS
415
Photograph by E. R. Sanborn, N. Y. Zool. Soc.
FIG. 194. Persian wild ass; showing the dorsal stripe which appears to be a
primitive character in the Equidae.
Photograph by E. R. Sanborn, N. Y. Zool. Soc.
FIG. 195. Grant's zebra (Equw burchelli granti).
416 ZOOLOGY
tural features ; thus the rodents, with modified teeth and
the canines lost, could not possibly give rise to;carnivora,
primates, or artiodactyla. The artiodactyta and peris-
sodactyla, with their modified feet^ could not be
ancestral to primates, carnivora, or rocffiits. Although
the details of evolution, and consequently of classifi-
cation, are to be determined only by minute and per-
sistent research, or may elude us altogether, many 0f
the broad features are so obvious that they may be
appreciated by any beginner.
References
FLOWER and LYDEKKER. Mammals, Living tind Extinct. A. and C. Black.
OSBORN, H. F. The Age of Mammals. The Macmillan Company.
CHAPTER FIFTY
THE EVOLUTION OF THE HORSE AND THE ELEPHANT
1. WERE the horse not a common animal, to be seen structure of
any day on the streets, it would be regarded with wonder thehori
and amazement. The Mammalia in general, including
man, have five toes or digits. This number is never
increased, except in monstrosities, but it may be de-
creased. In the horse, only a single toe is left on each
foot, and the greatly enlarged toenail is the hoof. The
teeth of the horse are scarcely less remarkable. Adapted
for grinding hard food, they are very long, with an ex-
tremely complicated enamel pattern. The surfaces are
ground down during life, and as the appearance differs
at different levels, it is possible to tell the age of a horse
by its teeth. The mane and tail are also peculiar, and
there are many other interesting structural features.
Added to all these are the psychological characteristics,
- the wonderful combination of intelligence with docil-
ity, which makes the animal useful to man. A well-
known breeder and lover of horses was so moved by all
these excellences, that he declared that the one great
error in evolution was the derivation of man from a mis-
chievous, ill-behaved creature of the monkey group, in-
stead of a majestic, sagacious beast such as the horse !
2. In any dispute over the fact of evolution, it would Ancestors of
be natural to cite the horse as presenting special difficul-
ties. How could it be that an animal so peculiar had
been derived from any other type ? Fortunately, how-
ever, it is in this very group that we have one of the most
complete evolutionary series, preserved in the form of
fossil bones. Going back to a period fully three million
years ago, we find in the Eocene strata of the Rocky
Mountain states remains of an animal barely a foot
417
418
ZOOLOGY
high at the shoulder, and having rather the appearance
of a small dog. This little beast is named Eohippus,
which literally means "the horse of the dawn," — the
From Lull's " Yale Collection of Fossil Horses"
FIG. 196. Sketches showing the evolution of the horse from the primitive four-
toed ancestor to the last American species. Restored by Dr. R. S. Lull from speci-
mens in the collection of Yale University, i, Eohippus, Lower Eocene; 2, Oro-
hippits, Middle Eocene; 3. Mesohippus, Oligocene; 4, Merychippus, Miocene;
5, Ptiohippus, Pliocene ; 6, Equus scotti, Pleistocene.
EVOLUTION OF THE HORSE AND THE ELEPHANT 419
beginning of horse life. It is often called the first horse,
but of course it was not a horse at all, in any proper
meaning of that word. The toes were already reduced
from the primitive number, but there were four on the
front foot, three on the hind. The teeth were short-
crowned, without a complicated enamel pattern. Such
an animal was well adapted to the warm, moist climate
of the period, feeding on soft food and traveling on soft
ground. Had conditions remained unchanged, there
would presumably have been no evolution of the horse.
3. In the Rocky Mountains the rocks of the Ter- Lines of de-
tiary period have been unusually well preserved, and vel°Pment
from them it has been possible to obtain a remarkably
complete series of fossils. Thus it is that the history
of the horse has been made out, and although the family
belongs today to the Old World, we feel assured that it
developed in the New. Without going into many de-
tails, it will suffice to say that in successive deposits we
can trace a series of forms leading from the small
Eohippus to the horse of modern times. In the foot
there is a gradual reduction of the toes. In the teeth
the enamel pattern becomes increasingly complex, and
the crowns are lengthened. There is a steady, almost
regular increase in size. Thus the species of the horse
family, when found as fossils, are especially valuable to
the geologist as time markers. They indicate relative
time only, of course, — like a clock the hands of which
moved, but on the face of which were no marks to indi-
cate the seconds, minutes, or hours.
4. Naturalists, recording evolutionary processes such The theory
as that just described, have sometimes postulated what
they called orthogenesis, the first part of the word mean-
ing "straight" or "regular," as in orthodox. This im-
plies that evolution follows a predetermined path, which
420 ZOOLOGY
was laid out for it in the beginning. Thus, the horse
group was to increase in size, decrease the number of its
toes, etc. It actually behaved as if following out a
program planned in advance. The idea is not inher-
ently absurd, since this is the course of individual devel-
opment ; and it may well be imagined that there is some-
thing in the nature of a particular kind of protoplasm,
that will lead it to vary in a certain direction. Indeed,
we know that it does not vary in all directions ; thus we
cannot get a genuinely blue rose. It is to be noted,
however, that the evolution of the horse group is also
strictly along the lines of adaptation. The climate be-
came cooler and drier ; the animal became an inhabitant
of the plains. The solid hoof is adapted for running on
hard ground, for receiving the impact of the heavier
body ; also for kicking the carnivorous enemies which
had in the meanwhile evolved to prey upon the horse.
The long-crowned, hard teeth are adapted for feeding on
the vegetation to be found in open, dry places, and what
might be regarded as a difficulty has been so completely
overcome that the animal now needs the 'type of food
for which it is specially fitted. The whole history is one
of adjustment to conditions, and the evolutionary
process could not have taken place in the Eohippus en-
vironment, for the simple reason that the changes would
all have been detrimental, leading eventually to ex-
tinction. In the case of the elephant group, as we shall
presently see, there was the same apparent orthogenesis,
until a certain structure became useless, when the whole
process was reversed.
African 5* Eventually the horse group reached the Old World,
horses undoubtedly by way of the land bridge to Asia which
then existed in the north. During much earlier times
the primitive horselike types had existed on both sides
EVOLUTION OF THE HORSE AND THE ELEPHANT 421
of the world, the American Eohippus being represented
in Europe by an animal called Hyracotherium, or coney
beast. It is therefore uncertain where the group
actually originated. Nevertheless, the development of
the true horse can be traced in America, and in pre-
historic times numerous kinds of horses, large and small,
existed in this country. One of them, found in Texas,
had teeth larger than those of the largest living race.
In northern Texas and the adjacent parts of New
Mexico was a type of horse which has been named Equus
scotti, after the palaeontologist W. B. Scott, who has con-
tributed much to our knowledge of fossil mammals.
This species is known by very complete skeletons, so
that it is possible to form an excellent idea of its char-
acters. Its bones are remarkably like those of the
domestic horse, but it was relatively long-bodied and
short-legged, with a large head. Why it became extinct,
we do not know. Certainly the climate was not unfa-
vorable, as horses ran wild in vast numbers when later
introduced by the Spaniards. Man could hardly have
been responsible, for aboriginal man did not destroy the
game animals of this continent. Possibly some disease
destroyed the horse in America, leaving no proof of its
existence.
6. In the Old World the genus Equus (Latin, a horse) Old World
presents a number of very distinct types, including the
horses proper, the asses, and the zebras. The typical
or true horses formerly abounded in Europe and Asia,
but today only one wild species exists. This animal,
found in western Mongolia, was named Equus przewal-
skii, after the well-known Russian explorer, Przewalski,
who obtained the first specimen nearly 40 years ago.
It is a pony with a relatively large head (here suggesting
the Equus scotti), a short, erect mane, and a tail with
422
ZOOLOGY
Origin of
the domestic
horse
Photograph by E. R. Sanborn, N. Y. Zoiil. Soc.
FIG. 197. Przewalski wild horse (Equus przevalskii).
rather short hair basally, though ending in a long tuft.
The general color is dun, and there is a distinct stripe
down the back, while shoulder stripes and barring on the
upper parts of the legs may frequently be observed. It
is an interesting fact that these same markings may
often be found on broncho ponies of the southwestern
United States, derived from the old Spanish stock which
formerly ran wild.
7. The domestic horse was named by Linnaeus Equus
caballus (from caballus, an old name for the horse, per-
petuated today in the Spanish caballo ; note also cabal-
lero, a gentleman, i.e., a man who rides a horse). It did
not occur to Linnaeus that more than one species was
involved, but, as in the case of dogs and cats, it appears
that the domesticated animal is derived through cross-
ing from two or more originally wild forms. Evidence
of this is found in the prehistoric drawings on the walls
of caves in France and Spain, made by the Cro-Magnon
man; These drawings, while not very exact, are clever
EVOLUTION OF THE HORSE AND THE ELEPHANT 423
and evidently characteristic, and -suggest that even in
those remote times the straight-faced and "Roman-
nosed" types were perfectly distinct. This idea is also
supported by the skulls of various extinct horses which
have been found in Europe. How the horse first came
to be domesticated, we do not know, but some of the
prehistoric drawings appear to indicate its use as a pack
animal. Some adventurous individual, who had per-
haps employed a horse in this manner, one day con-
ceived the idea that it might also carry him, and leaped
astride. The astonishment of his fellows at this feat
appears to be preserved in ancient legends of a being
half horse and half man.
8. In many ways opposite to the Przewalski horse is The Celtic
the Celtic pony, or Equus celticus. This small animal, pony
now known especially^ from Iceland, exists only in a
state of domestication, but it has marked peculiarities.
In color it is similar to the Przewalski horse, but the
mane is long and consists of a central and a lateral por-
tion. The tail, instead of being short-haired at the base,
is there covered by a great tuft. Professor J. C. Ewart
of Edinburgh, who first clearly distinguished the Celtic
pony, observed that the bunch of hair at the root of the
tail served to protect that region from rain and snow.
In a storm, while other horses made for shelter, the Cel-
tic ponies simply turned their hind quarters to the blast
and went on feeding unconcernedly. Were they not
able to do this, they would scarcely be able to prosper in
the damp and stormy regions which they inhabit.
On the legs of horses may be seen certain callosities or
pads, the upper ones being called "chestnuts," the
lower, "ergots." The latter seem to represent rudi-
ments of the hind foot pad ; but the former, on the inner
side of the leg, must apparently be explained in some
424
ZOOLOGY
other way. It has been suggested that the chestnuts
represent glands which exist in deer, which function as
scent organs. The habits of the horse would make such
glands superfluous, but they were perhaps functional in
an ancestor. The Celtic pony has entirely lost the er-
gots and the hind chestnuts, and hence Professor Ewart
regards it as a specialized member of the genus.
9. Another -very distinct, type is the Arab, which is
the most beautiful and interesting of all horses. It has
been named Equus asiaticus. Whether it originated in
Asia or northern Africa is much disputed, but the Lib-
yan tribes appear to have possessed such an animal at a
time when the Arabs were quite without horses. The
Arab is long-legged, with the head held high and the
tail raised when in motion, as may usually be seen in
Photograph by Professor J. C. Ewart
FIG. 198. " Sherkieh," an Arab of the
Hamdani Simri strain.
Photograph by Professor J. C. Ewart
FIG. 199. " Romano," a type of horse simi-
lar to that figured by prehistoric men in
the Combarelles cave, France.
EVOLUTION OF THE HORSE AND THE ELEPHANT 425
equestrian statues. The profile of the face is distinctly
concave, and the short skull is broad between the eyes.
The tail vertebrae are reduced, and there are only five
instead of six lumbar vertebrae. The English thorough-
bred horse, remarkable for its speed, owes much of its
quality to Arab blood.
EVOLUTION OF THE ELEPHANT
I. The evolutionary history of the elephant was long Discovery of
unknown, but in comparatively recent years the Fayum
desert of Egypt has yielded a series of fossil animals Egypt
which serve to connect the highly specialized elephant
of today with much more primitive types. Dr. C. W.
Andrews of the British Museum, who obtained most of
these fossils, has given a full discussion of the subject.
The oldest known member of the series .is called Mceri-
therium, after the ancient Lake Mceris, near which it was
discovered. It was more or less tapirlike, very small in
comparison with the elephants, with extremely short
tusks.- Its relationships with still earlier forms cannot
be made out, but there are certain resemblances to the
living manatee in the details of structure, though not at
all in appearance. After a time this type gave place to
the Palczomastodon (old mastodon), a larger animal with
longer tusks, and the lower jaw extended outward, ap-
parently for digging. Next we have the Trilophodon,
still larger, with long, slightly curved tusks, and enor-
mously lengthened lower mandible, which must have
served as a regular plow. This type of animal was so
successful that it spread far and wide, and even invaded
North America. The arrival of the Proboscidea, or
elephant group, in America took place in the Miocene,
and marks an important date in the geological series.
426
ZOOLOGY
Lines of de-
velopment
Mastodon
and mam-
moth
2. So far, evolution was apparently orthogenetic,
the size steadily increasing, while the tusks grew longer
and the trunk doubtless developed. Although the
trunk is of course lacking in the fossils, some idea of its
development may be gained by a study of the surfaces
for muscular attachment. Now, however, while the
tusks became still larger, and curved upward, the lower
jaw or mandible reversed its former development and
became very short. It appears certain that the mode
of securing food had changed. The animal no longer
gained its food principally by digging or uprooting
plants, but used its long trunk to secure branches from
the trees or "gather in" the long herbage. The mandi-
ble of Tetrabelodon, if retained, would have been a use-
less luxury, or indeed a detriment. The teeth, now re-
duced in number, became extraordinarily massive, with
eventually a very complicated pattern of transverse
ridges of enamel. More powerful grinding organs could
hardly be imagined. The great tusks, used by the males
in fighting and also employed in digging, are composed
mainly of solid dentine, furnishing to man the familiar
substance ivory. The skull is short and of great height,
with an enormous development of the frontal sinuses or
air spaces. In consequence of this structure, blows on
the front of the head do not kill the animal, and bullets
fired at the forehead rarely reach the brain. The brain,
though small for such a large animal, is actually much
larger than that of man. The mental development of
the elephant is also noteworthy and, as in man^ may be
connected with the ability to handle objects. Had the
elephant two trunks instead of one, as a man has two
hands, who can say what it might become ?
3. The mastodon and mammoth are extinct ele-
phants. The mastodon is especially distinguished from
EVOLUTION OF THE HORSE AND THE ELEPHANT 427
From Lull's "Evolution of the Elephant "
FIG. 200. Evolution of the group of elephants, e, Moerilherium (middle Eocene
of Egypt); d, Palceomastodon (upper Eocene of Egypt); c, Trllophodon (or
Tetrabelodori) angustidens (Miocene) ; 6, Mastodon (or Mammuf) americanus
(Pleistocene) ; a, Elephas columbi, the Columbian Mammoth (Pleistocene), related
to the living Indian elephant.
428 ZOOLOGY
the modern elephants by the structure of its teeth,
which have not nearly so many transverse ridges and
are thus more primitive. The mammoth, on the other
hand, is a veritable elephant, belonging to the same
genus (Elephas) as the Indian species. The Indian ele-
phant is hairy at birth, and the mammoth was coated
with long hair at maturity. Not only do the drawings
of ancient man show the mammoth as a hairy beast, but
frozen bodies of these animals have been found in
Siberia, preserved in cold storage so perfectly that the
flesh was still edible. Even the contents of the stomach
have been secured, showing that the food consisted of
such plants as still exist in those northern regions.
These discoveries illustrate the possible mistakes which
may be made in reasoning about past climates from
fossil remains. Modern elephants being tropical, one
would naturally infer that wherever these animals ex-
isted, tropical conditions prevailed.
North America, in Pleistocene time, had three dis-
tinct species of elephants or mammoths. Of these the
true mammoth, Elephas primigenius, was not the larg-
est. The other two are named Elephas columbi (after
Columbus) and Elephas imperator (emperor). Their
remains are widely scattered over the country.
Living 4. Living elephants belong to two groups. The
elephants Indian elephant is familiar as a domestic animal in
oriental countries. The African elephants, remark-
able for the extremely large ears, have been placed in a
distinct genus, Loxodonta. There are several distinct
types, but authorities differ greatly in their judgment
as to the number of species. It is naturally difficult to
secure a good collection of elephants, and consequently
opinions have been based on inadequate materials.
CHAPTER FIFTY-ONE
THE EVOLUTION OF MAN
1. IT is impossible for any of us, unless we happen to our igno-
be kings or their kindred, to trace our ancestry back rance of
J human
many generations. In any group of Americans gathered ancestry
together, it will be found that few know the family
names of their grandmothers, and almost none those of
their great grandmothers. We all know, of course, that
the stream of life has been continuous, that one family
is not any older than another, — that all are of incalcu-
lable antiquity. If it is thus difficult or impossible to
trace our human ancestry, how can we expect to succeed
with -the prehuman, and recover traces of those beings
whose existence millions of years ago was necessary in
order that we should be here today ?
2. No biologist supposes that it will ever be possible Deveiop-
1 to ascertain all the details of human evolution. Yet the ment.ofj<
man indi-
general outline of the process is recognizable. First of cates the
all, the human individual, in his development, appears of^s^
to repeat more or less the history of animal life, — to evolution
climb, as Huxley said, his own family tree. Thus all
animals, including man, begin as a single cell, agreeing
in its general features with the lowest forms of life
known, the permanently one-celled organisms called
Protozoa and Protophyta. All many-celled creatures
can be traced back to the one-celled condition at the
beginning of their existence, and we can hardly doubt
that the evolutionary process began in a similar manner.
Thus the first stage of human evolution may be de-
scribed as protozoan.
3. Development proceeds through segmentation. Early stages
Numerous cells are formed, which, instead of separating oi^t*i£~
and becoming isolated individuals, as in the Protozoa, evolution
429
430
ZOOLOGY
remain together to form a cooperative unit. In course
of time a cavity is formed within the developing organ-
ism or embryo, communicating with the outside by a
a single opening, called the blastopore. In a general
way this stage may be said to correspond with that of
the adult medusa or jellyfish, or with the sea anemone.
These lowly animals are shaped more or less like a bottle,
with a large cavity opening only at one end. It thus
The coeien- appears probable that our very remote ancestors passed
terate stage tnrough a ccelenterate stage, though of course this can-
not be demonstrated as a fact. The blastopore, which
is situated at what becomes the hind end of the body,
presently closes, and the permanent anterior and pos-
terior openings of the alimentary canal are formed by
new depressions or pits, which meet and become con-
tinuous with the ends of the central cavity. When this
has occurred, the embryo has reached what is in effect
a worm stage ; and although there is no close resem-
blance to any particular kind of worm, we can hardly
doubt that we have passed through a wormlike condi-
tion in the course of our evolution.
All this may seem highly speculative, but from Our
knowledge of animal structure and development it ap-
pears impossible to imagine any other path of evolution
than the one suggested. Thus, for example, while a
non-scientific person might ask whether the first animal
was not after all wormlike, or fishlike, the so-called
lower forms resulting from degeneration and disinte-
gration, the biologist readily perceives so many difficul-
ties in the way of such a theory that he cannot even class
it among the possibilities.
4. When we leave the worm stage, our principal diffi-
culties begin. From this point until the vertebrate
type is distinctly formed, the path of evolution is ob-
Evolution
from a
wormlike
stage
THE EVOLUTION OF MAN 431
scure, and great differences of opinion prevail. The
Amphioxus does indeed illustrate a prevertebrate stage,
but of course this animal, now living in shallow seas,
must be quite different in detail from our actual ances-
tor. We can hardly hope that fossils will be found
which will throw much light on this question, but the
patient study of existing animals may give us additional
clews. At all events our more or less wormlike ances-
tor developed a notochord, a dorsal nerve cord, and a
system of breathing (in water, of course) by means of
gill arches. In a dramatic treatment of the event, we
have supposed this primitive creature to say :
We are not much to look at, but we are
All in the way of progress.
Our backs are stiffened by a notochord, and all above
A slender nerve cord runs from fore to aft,
Prophetic of a brain. This tiny spot, this little speck of black,
Will some day be a pair of eyes, to knowingly survey the world,
While these grll slits, ranged on each side, already serve
To liven us with oxygen, gleaned from the waters flowing through them.
All in the way of progress to be vertebrates, and in days to come
Perchance, some creature with a soul.
5. Reaching the vertebrate stage, we cannot doubt Early
that the first forms were fishlike, and lived in water. vertebrates
The human embryo, at an early stage, shows structures
corresponding to the gill bars, though no longer func-
tioning as such. One of these ultimately becomes the
mandible or lower jaw. Although we thus postulate a
fish stage in our ancestry, we do not suppose that this
includes anything resembling the higher fishes of today.
In the modern fishes of highly specialized type, such as
the perch, the posterior paired fins have come to lie close
to or even beneath the anterior or pectoral pair; and
many other developments have taken place which lead
altogether away from the human type of structure.
432
ZOOLOGY .
Discovery of
the land
by man's*
ancestors
Egg-laying
mammals
The amphibian, the next step in the path of evolution
toward man, unquestionably arose from a relatively
primitive type of fish.
6. With the appearance of amphibians came the dis-
covery of the land by vertebrates, as we have already
indicated. Next came the reptiles, capable of repro-
ducing without recourse to water. From these arose the
mammals, but not from anything like the modern rep-
tile. As in the case of the fishes, the higher reptiles,
with their single occipital condyle and other peculiari-
ties, have gone off on a path which cannot possibly lead
to anything mammalian. It is only by reference to
very ancient fossil forms that we can get any accurate
clew to the course of events. This we seem to find in
the cynodont or dog-toothed reptiles of the South
African Mesozoic, — animals which possessed paired
occipital condyles, and the teeth differentiated into in-
cisors, canines, premolars, and molars.
7. The first true mammals, or Prototheria, were
warm-blooded, hairy, egg-laying creatures. The mod-
ern Australian duckbill (Ornithorhynchus) is a special-
ized member of this group. The principal food of these
animals was probably insects, and it is perhaps a fact
that the development of the mammalian type was
largely aided and made possible by the increasing de-
velopment and variety of insect life. Still in the Meso-
zoic age, primitive marsupial mammals arose, now
viviparous, but producing the young in a very under-
developed condition, so that they had to be nourished
in the maternal pouch. Such animals, represented
today by the opossums, were probably also insect
feeders, like the South American Marmosa. They were
also probably arboreal, living in trees ; and in accord-
ance with these habits certain changes took place in the
THE EVOLUTION OF MAN 433
structure of the shoulder girdle, which profoundly in-
fluenced subsequent developments. Thus the coracoid
bone, so prominent in birds, became reduced to a mere
rudiment, forming in man the coracoid process of the
scapula (shoulder blade).
8. From the primitive marsupials the most natural Origin of the
step is to some form of tree-living insectivore, — such a Pnmates
creature as the Tupaia or tree shrew of the Oriental
Region. At about this stage the bats branched off, tak-
ing to the air and thus losing all chance of developing
tool-making hands. From the primitive arboreal in-
sectivore, somewhere about the beginning of the Ter-
tiary age, we may derive the early Primates, more or
less lemurlike forms. It may be worth while to ask why
we have omitted all the other great groups of mammals
from the possible line of descent. The answer is, that
each one of them has specialized in a direction wholly
divergent from a possible human stem. Thus the Ro-
dents, in their teeth, and the Ungulates, in their feet,
have gone to extremes which preclude the subsequent
development of the human type of dentition or digital
structure. Parts lost will not be regained, and parts
extremely specialized and modified will not return to a
relatively primitive condition.
9. From the long-nosed Primates, or lemurs, we may Develop-
readily pass to the true monkeys and monkeylike forms. ™^°yS
Here we come to a division, for although lemurlike ani- and man
mals were formerly spread over both hemispheres, the
monkeys developed quite distinct types on the two
sides of the world. Man, in his structure, is related to
the Old World monkeys, not to those of South and
Central America. Thus the traditional Old World ori-
gin of mankind is confirmed by zoological researches.
No existing type of monkey can be said to resemble very
434
ZOOLOGY
Recapitula-
tion of
stages of
human
evolution
closely man's probable ancestor, each genus and species
having developed along special lines since the time when
the Hominidse branched off. Man, as we have already
noted, acquired an upright posture, going with a return
to terrestrial life. His hands developed for the making
and using of tools, and the brain to guide the hands.
Yet for long ages, in spite of these advantages, man re-
mained in a primitive condition, scarcely as prosperous
as many of the animals prowling in the vicinity of his
caves or shelters. Weak in many respects, his special
endowments seemed to hardly more than make up for
his failings and prevent him from perishing in the
struggle for existence. It was not until many tens of
centuries had passed that man assumed his dominant
position as lord of the earth.
10. To recapitulate, the principal stages in the evolu-
tion of the human type appear to have been : (i) Proto-
zoan stage, (2) ccelenterate stage, (3) wormlike stage,
(4) prevertebrate stage, (5) fish stage, (6) amphibian
stage, (7) cynodont reptilian stage, (8) marsupial stage,
(9) arboreal insectivorous stage, (10) lemurid stage,
(n) monkeylike stage, (12) Hominidae, or family in-
cluding Homo, which is man. Perhaps some ingenious
maker of moving pictures will one of these days project
this evolution on the screen, so that in an hour the audi-
ence may see the protozoan develop by successive stages,
to culminate in a human animal, disguised in the very
latest fashions.
CHAPTER FIFTY-TWO
THE CHARACTERS OF HOMO
I. LINNAEUS, when giving names to all known ani- Manre-
mals, designated man as Homo sapiens. The generic
name, Homo, is of course derived from the Latin.. The bratesin
. ,, . r . structure
specific term sapiens, irom the same source, means
"knowing" or "wise"; we use the word "sapient" in
English. The genus Homo is placed in a family Ho-
minidse, which is only one of several families constitut-
ing the order Primates, of the class Mammalia. When
we come to consider the characters of man, we find
that they are mostly such as are also possessed by
numerous animals. Thus the vertebral column is found
in all vertebrates ; the warm blood and hair. on the body
are common to Mammalia in general, to cat and dog,
squirrel and mouse. On closer inspection we observe
that the tissues of the body — the striated and un-
striated muscle, the nerve tissue, the connective tissue,
fat, cartilage, bone, epithelium, gland tissue, lymph,
and blood — are all closely similar to those found in
other vertebrates, and in many cases even in inverte-
brates. The organs or parts, made up of these tissues,
— the eyes, nose, ears, heart, lungs, liver, etc., — all cor-
respond to parts readily discernible in other mammals.
So also the embryology, the order of development, is
like that of other creatures. Certainly man does not
represent an entirely new plan of creation, so far as his
physical nature goes.
2. Yet, in the midst of all these points of resemblance, special
we have no difficulty in observing differences ; we recog-
nize a human being at once. There are, indeed, more of
these peculiarities than the non-anatomical person can
discern. Here is a list of the more striking characters
of Homo :
435
436 ZOOLOGY
(a) The large brain, the cerebrum very large and
much convoluted ; that is to say, the apparatus
After Huxley
FIG. 201 . Man and the higher apes : a, orang ; b, chimpanzee ; c, gorilla ; d, man.
for receiving and storing impressions is very
greatly developed.
(b) The face is shortened, so that the profile, at least
in the higher types, is practically vertical.
(c) The lower jaw presents a distinct angle, the chin,
at least in the best-developed races and individ-
uals.
(d) The premaxilla, or anterior portion of the upper
jaw, is not a separate bone, except at an early
^
(e) There is no distinct space (diastemma) between
the incisor and canine teeth.
(/) The canine teeth are not appreciably larger than
those next to them ; that is, there are no dis-
tinct tusks.
(g) The spinal column has four curves, an adaptation
to upright posture.
(h) The arms are not so long as the legs.
(i) A small bone, the os centrale, has disappeared
from the carpus or wrist.
THE CHARACTERS OF HOMO 437
(/) The muscles of the thumb are better developed,
giving free play to that member, and the index
finger is freely movable independently of the
others.
(k) The bones of the lower arm (radius and ulna) are
so constructed that the arm may be rotated,
as in turning a screw. This is of the utmost
importance in connection with the use of tools.
(/) The leg and foot are adapted for walking, and the
whole surface, from the ends of the phalanges
to the base of the tarsus, is applied to the
ground.
(m) The great toe is not freely movable, and is no
longer readily used for grasping.
Other characters may be described as negative, being
due to the loss of parts or functions :
(n) The tail is lost, being represented only by the
coccygeal bones beneath the skin. This is, of
course, not peculiar to man.
(o) The greater part of the hair has been lost from the
body.
(p) Certain muscles of the head and neck have ceased
to function, at least normally. Such are those
which move the ear, and that which wrinkles
the posterior part of the scalp. Some people,
however, can use these muscles.
(q) The point of the ear is lost, being represented only
by a small tubercle. On the other hand, the
lobule has developed.
(r) There exists in the throat a small sinus or space
which appears to represent the vestige of a
howling sac, such as is so well developed in
certain South American monkeys. The sac
disappeared long before 'college yells were in-
438 ZOOLOGY
vented ; Nature could not anticipate a possible
later function.
These characters are numerous, and others could be
added, but it will readily be seen that from the stand-
point of morphology they are quite unimportant in
comparison with the resemblances. Many of them are
not absolute or invariable. The great characters of man
are mental ; his brain, while similar in structure to that
of his animal relatives, is capable of lifting him to a new
plane of thought and action, whereby he stands apart
from all other living things. A sufficient difference in
degree becomes a difference in kind. Is man, then,
isolated in his splendid powers ? Is his a voice crying
in the wilderness, with no possibility of an answer ? It
is the function of religion, rather than of science, to
answer this insistent question.
Extinct 3. Although the family Hominidae at present includes
v< only the genus Homo, there are indications of one or
more other genera existing in former times. In 1894
the Dutch naturalist Dubois described the remains of an
From Keane's "Ethnology"
FIG. 202. Profiles of the crania of various manlike skulls : a, ordinary Irish skull ;
b, the Spy skull; c, the Neanderthal skull; d, Pithecanthropus erectus; e, skull of a
gorilla.
THE CHARACTERS OF HOMO 439
animal which he discovered in the island of Java, and
which seemed to possess the characters of the long-
sought "missing link." He named it Pithecanthropus
erectus, which means "the monkey-man walking erect."
Only the upper part of the skull, a couple of teeth, and a
femur or thigh bone were found. The structure of the
latter was held to establish the erect attitude, but the
skull showed very primitive characters. The brain
must have been intermediate in size between that of the
highest monkey and the lowest man. It is, perhaps,
not absolutely certain that the thigh bone belonged to
the same animal as the skull, and as the remains are
very incomplete, we can only say that we have evidence
of a type of Hominidae so primitive that it may be re-
garded as constituting a distinct genus. The teeth are
more like those of an orang than of a man, and it is
possible that Pithecanthropus should be excluded from
the Hominidae altogether.
4. In 1913 Dr. A. Smith Woodward of the British ThePUt-
Museum described the remains of a manlike creature downman
found in gravel near Piltdown, Sussex, in the south of
England. The fossils consisted of an imperfect skull
and a mandible or lower jaw. The skull is very thick,
but decidedly human in character, though relatively
primitive. The jaw, on the other hand, is like that of
a chimpanzee. This strange combination of characters
led Dr. Woodward to regard the animal as a distinct
genus of Hominidae, to which he gave the name Eoan-
thropus, or " man of the dawn." More recently it has
been maintained by able naturalists that two different
things have- been mixed together, and there is apparently
little doubt that the jaw really belonged to an extinct
species of chimpanzee, living at the same time as the
man whose skull was found associated with it.
440 ZOOLOGY
The Heidei- 5. The remaining fossil men or manlike animals have
been referred to the genus Homo, but two extinct
species have been recognized in Europe. The oldest of
these, dating from the second interglacial period in
the Pleistocene, is the Heidelberg man, Homo heidel-
bergensis, of Schoetensack. This species is known only
by a massive and very peculiar jaw, without any dis-
tinct angle marking the chin. It was found in a sand
i pit at Mauer, near Heidelberg, in Germany, along with
bones of the lion, extinct horse, rhinoceros, elephant,
etc. As the oldest fossil Homo this specimen acquires
the greatest significance, especially as it has very marked
primitive characters, unquestionably indicating an ex-
tinct type of man. Roughly speaking, the Heidelberg
man may be supposed to have lived about 250 thousand
years ago.
The 6. The other extinct Homo, living perhaps 50 to 100
Neanderthal thousand years ago, is the Neanderthal man, Homo
neanderthalensis, of King. This rather unfortunately
named being was widespread in Europe, and quite
numerous remains have been found. The head was
relatively large, but low-browed, and the brain was
smaller than in modern man. The limbs were very^
robust and the shoulders broad, while the head and
neck were bent forward rather than held erect. The
knees appear to. have been habitually bent, and the
customary position when not in motion was .presumably
a scjuatting one. This powerful species of man, highly
developed for the time in which he lived, was doubtless
incapable of becoming civilized or of competing suc-
cessfully with the true Homo sapiens,:.-. . . ,:\
7. Finally, we have abundant evidence in Europe of'
a race of cave dwellers, which, probably coming from the
Orient, supplanted the^ Neanderthal man and took pos-
THE CHARACTERS OF HOMO 441
session of the country. This race, the Cro-Magnon, Beginnings
was veritable Homo sapiens. In his bodily structure,
his skull, and presumably his brain, he was like modern
Europeans. His lineal descendants are probably still
living in France. For many thousands of years this
race lived in caves, the walls of which it ornamented
with remarkable drawings, sometimes in colors. Thus
it is possible to look upon sketches of the hairy mam-
moth, made by men who hunted this now extinct ani-
mal. It is strange to contemplate the life of Cro-
Magnon man, so primitive and barbarous, yet showing
flashes of genius prophetic of the future. How could
he know or imagine the forces latent within him, — his
tremendous powers for good and evil, his capacity for
invention and discovery ? Could he have contemplated
the future of his race, would he have rejoiced in the
splendid coming developments, or would he have re-
coiled from the baseness and wickedness which he, the
barbarian, could never have supposed possible? After
all, we of today stand midway in the stream of human
progress. Like the Cro-Magnon man, we are capable
of much more than we know, and are destined to go
forward to a future in the light of which the present
will seem miserably inadequate. Unlike the Cro-
Magnon man, we know that our feet are set on a path
of progress, and that it is for us to decide where that
path shall lead. Driven from our paradise of primitive
simplicity, we have the choice of good and evil, but no
longer the option of deciding whether to choose.
References
OSBORN, H. F. Men of the Old Stone Age, 1915. •
MILLER, G. S. The Jaw oj the Piltdown Man. Smithsonian Institution, 1915.
DUCKWORTH, W. L. H. "Prehistoric Man." Cambridge Manuals of Science
and Literature, 1912.
CHAPTER FIFTY-THREE
Environ-
mental and
historic
factors
How the
past affects
the present
THE GEOGRAPHICAL DISTRIBUTION OF LIFE
i. IT is well known to all that the various forms of
animal and plant life are not distributed uniformly over
the earth's surface. When we seek to determine why
the range of different species is limited, we find that the
factors involved may be sorted out into two great
groups, which may be termed the environmental and
historic. The environmental factors are those which
determine the possibility of existence in a given locality.
Thus a fish cannot live on land ; a tropical bird, trans-
ported to the arctic regions, would probably die in half
an hour. These are .the simplest cases, depending on
physical conditions of the most obvious sort, but many
other factors also must be classed as environmental.
Thus the chestnut tree cannot exist in regions invaded
by the chestnut-blight fungus ; mice perish in the
presence of a sufficient number of cats. In these ex-
amples the death-dealing causes may be directly ob-
served, but many others escape our notice. Causes of
death or failure to reproduce (which biologically comes
to the same thing) frequently result in extermination
only after a long period, and then the process is too slow
to be conspicuous to the casual observer.
2. Historic factors have to do, not with the effects of
the environment, but with the ability of the organism to
reach given localities. The question is not, Can you
live here ? but, Were you able to get here ? Humming
birds would presumably flourish in tropical Asia and
Africa, but they have never been able to cross the
Atlantic or Pacific. Many European insects and weeds
prosper exceedingly in America after being accidentally
brought over by man, but in pre-Columbian times they
442
THE GEOGRAPHICAL DISTRIBUTION OF LIFE 443
were all absent. We ourselves were excluded from
America until navigation reached a certain stage of de-
velopment. It is of course true that the so-called
historic factors are also in a broad sense environmental ;
the restricting ocean, mountain, or desert is part of the
environment. It is, however, the peripheral environ-
mental, — the outer wall, not the medium in which the
organism lives and has its being.
3. On further examination it appears that, these Themuiti-
broad distinctions, while useful, are very crude. We Jj^fs°aiid
like to point out the "cause" of this or that, forgetting the inter-
that life is subject to a vast multitude of "causes." events
Tennyson had this in mind when he wrote :
Flower in the crannied wall,
I pluck you out of the crannies,
I hold you here, root and all, in my hand,
Little flower — but if I could understand
What you are, root and all, and all in all,
I should know what God and man is.
It required the combined forces of the universe to pro-
duce the flower, and to ask why it was in the crannied
wall is ultimately to raise more questions than any man
can hope to answer. Nevertheless, we may by search-
ing determine many things, and the study of geograph-
ical distribution leads us through winding paths to
many remarkable conclusions.
4. To illustrate the methods of biogeography, we may Methods of
take any small area of ground on which plants are ge0graphy
growing. We shall suppose that the plants found are
the following : sunflower, dandelion, prickly-pear cac-
tus, thistle, burdock, and snowberry. Determine the
species, and then look up the known distribution of the
genera and species. We find that they can be classified
as follows :
444 ZOOLOGY
(a) Genus-exclusively Old World, except when spread
by man : burdock.
(b) Genus native in America as well as Old World,
(1) Species native in America : thistle (if it is
one of the American species, as will prob-
ably be the case).
(2) Species introduced into our region from
Europe : dandelion.
(c) Genus and species native only in America :
cactus ; snowberry ; sunflower.
So far, we are concerned with the historic factors.
How did these plants come there ? When a plant or
animal is found native only in a given region, we say
that it is endemic; so the cactus and snowberry are
endemic in America. We may ask, however, whether
it originated in the country where we now find it, or
came from somewhere else. In the former case it is
endemic in the strict sense, in the latter it may be
called precinctive, if we wish to note the distinction.
For example, the brightly colored snails of the Hawaiian
Islands are certainly endemic ; they are wholly different
from those found elsewhere, and from their number and
variety have evidently undergone considerable evolu-
tion on the islands. The redwood is now confined to
California, but fossil redwoods are found in many
other regions. There is no special reason for thinking
that California, where the tree is making its last stand,
was its original home. The distinction thus made is a
real and interesting one, but very often we are unable
to come to a definite decision. Even so, it may be
worth while to try to estimate the probabilities.
5. Having now discussed our plants from one point
of view, we may take up the environmental factors.
Perhaps there is a marsh or wet meadow not far away,
f THE GEOGRAPHICAL DtSTRIBUTION OF LIFE 445
and in this none'oi:our. plants- are found. As we go- influence of
from one environment to another, we observe -that OUP envi™n'
ment, and
plants differ in their ability to exist in them, though the develop-
there is no doubt that their seeds have reached these adaptations
places. The dandelion is able to endure surroundings
quite impossible for the sunflower. It also spreads
more easily on account of its parachutelike fruits, and
when once established lasts a long while, being a
perennial. Thus we find ourselves discussing all the
characters of the plants in their relation to the sur-
roundings ; the study of distribution becomes a broad
study of dynamic botany, of forces rather than of mere
structures. As in the other case, we find that precise
answers to our questions are often impossible. They
could be reached only through the knowledge of facts
which we perhaps have neither time nor ability :to
ascertain. This must not prevent us from doing our
best; the human mind must always face the unknown
in the process of education.
From time to time we shall be rewarded by discoveries
which will reveal the wonderful machinery of Nature.
Thus it was found out that the spread of the Spanish
bayonet or Yucca was strictly limited by the range of a
little white moth which carries the pollen and brings
about fertilization. Conversely, of course, the range
of the moth is limited by that of the Yucca. These two
partners have to go together ; they cannot spread inde-
pendently of each other. The Eastern United States,
and particularly the Mississippi Valley, are remarkable
for the great abundance and variety of large fresh-water
clams. We know from fossils that similar shells were
once more widely distributed, as they occur abundantly
, in certain deposits of the Rocky Mountain region. It
might appear that they could live wherever there was
446
ZOOLOGY
sufficient water, but it has been determined that many
of them require the presence of certain kinds of fishes.
They produce a larval form called the glochidium.
The glochidia attach themselves to the gills of particular
fishes, where they become covered or encysted (in the
manner of a gall), and when at length sufficiently de-
veloped they break away and resume independent life.
Thus the mussel Lampsilis luteolus requires the presence
of basses or perches; Oboraria ellipsis is temporarily
parasitic on the sturgeon. One species, Hemilastena
ambigua, infests the gills of an amphibian, the Necturus
or mud puppy.
Distribution 6. The study of distribution may be made to throw
feo^aphf C much Hght on the Past history of the earth. Thus, the
of the past marine fishes on the two sides of the Isthmus of Panama
are so much alike that we are quite sure that the Isthmus
was formerly submerged. This is now confirmed by the
discovery of many fossil sea shells in the course of dig-
ging the canal. When islands, such as the British Isles,
have a biota1 nearly identical with that of the neighbor-
ing continent, we infer land connections in the past.
Oceanic islands, which were never connected with any
mainland, have only creatures of a type which might
have crossed the sea. For example, they never have
any truly native frogs, since these animals cannot en-
dure salt water. When we are sure that two lands
have formerly been united or separated, the degree of
resemblance in the products is an index to the length of
time which has elapsed since the change to present
conditions occurred.
1 Biota = fauna + flora ; the total life of the country.
CHAPTER FIFTY-FOUR
THE BIOLOGICAL REGIONS OF THE WORLD
1. GEOGRAPHERS divide the land regions of the world Theconti-
into continents : Europe, Asia, Africa, North and
South America, Australia. Biologists, investigating the
distribution of life, long ago found that these divisions spend with
were unnatural, in the sense that they failed to agree *
with any definable life areas. For example, when we go
from western Europe to northern Japan, crossing two
continents, we find the plants and animals very similar
throughout. Very many of the species differ at the
extremes of this long area, but the general similarity is
sufficient to impress even an unscientific traveler. On
the other hand, if we pass from Tibet to the plains of
India, all in Asia, we meet with an entirely new set of
organisms. In America, the highlands of Mexico differ
extremely in their products from the lowlands along the
coast, the tierra calient e or hot country.
2. In 1857 an English naturalist, P. L. Sclater, made Thebio-
a detailed study of the distribution of birds, and came
to the conclusion that it was possible to define a series Sciaterand
Wallace
of great zoological regions, each of which would be
found to possess a fairly similar fauna throughout.
Sclater's regions were studied by A. R. Wallace, who
found that they were equally valid for practically all
groups of land animals. Later investigations showed
that they applied to plants also. These regions are so
"natural," — that is to say, so recognizable by their
products, — that any competent zoologist or botanist,
transported blindfolded to a point within one of them,
could tell which it was after half an hour's investigation.
Difficulty would be likely to arise only in places on or
near the boundary of two regions.
447
448 ZOOLOGY
Definition of 3. The Sclater-Wallace regions are named and de-
logicaT fined as follows :
regions (a) Nearctic, or northern region of the New World.
North America, excluding all tropical portions
except the southern end of Florida.
(b) Neotropical. South America, and all tropical
parts of Mexico and Central America, as well
as the West Indies.
(c) Palcearctic, or northern region of the Old World.
Europe, Africa north of the Sahara Desert, and
the temperate parts of Asia.
(d) Ethiopian. All Africa except the northern tem-
perate portion.
(e) Oriental. Tropical Asia (Indian Region of
Sclater).
(/) Australian. Australia, New Guinea, and ad-
jacent islands.
Oceanic Tfee Oceanic islands j such as the Hawaiian Islands,
cannot properly be attached to any of the great regions.
The Antarctic 'continent also is to be considered sepa-
rately, but it has very little terrestrial life at the
present time, though it is known to have been warm
and fertile in remote geological periods. It is es-
pecially distinguished today by the penguins, a very
ancient type of birds existing in great numbers along
•the coast (see page 380).
It is possible to criticize the names given to some of
the regions, but they are so well established that they
cannot now be altered. From a scientific point of
view, of course, the two sides of the world are not
"new" and "old" ; and, on the other hand, the popular
use of the word "arctic" is for far northern, not tem-
perate, regions. The original meaning of "arctic" was
simply northern, — the region where the " arctos," or
THE BIOLOGICAL REGIONS OF THE WORLD
450
ZOOLOGY
Holarctic
region
The circum-
polar biota
Distinctions
between
Nearctic and
Palaearctic
regions
Neotropical
Region
constellation of the Great Bear, which we call the
Dipper, may be seen in the sky. Sclater's use of it is,
therefore, philologically correct.
4. The proposal has been made to combine the
Nearctic and Palcearctic regions, making a single im-
mense Holarctic Region. It is true that the northern
regions of the two hemispheres have in many respects
similar products, and when we go far north, or examine
the summits of the higher mountains, we find a circum-
polar biota, with identical species on the two sides of the
world. Nevertheless, there are very marked differ-
ences, which justify the separation of the Nearctic from
the Palaearctic. Thus, for example, the numerous
North American mice and related animals mostly
represent genera distinct .from those of the Old World.
In America we find skunks, raccoons, the pronghorn
antelope, the mountain goat, the prairie dogs, the
opossum, and many other animals quite distinct from
those of Europe and Asia. So also we observe many
distinctive birds, from the turkey to the humming bird,
the mocking bird, and the turkey buzzard, the snowbird
and the vireos, a multitude of warblers, etc., etc.
Similar differences exist among reptiles, amphibians,
and fresh-water fishes. Recent studies have shown
that some of the fishes supposed to belong to European
genera are in fact quite different. Among the flowering
plants the North American flora is rich in special types,
found nowhere else in the world. There are also
numerous genera of plants, such as the sunflowers,
which are exclusively American, but occur in both the
Nearctic and Neotropical regions.
5. The Neotropical Region is universally recognized
as one of the most distinct, as might be expected from
its relatively isolated position. Its animals include a
THE BIOLOGICAL REGIO.NS OF THE WORLD 451
special group of monkeys with prehensile tails, llamas
(which are related to the camels), sloths, armadillos,
anteaters, guinea pigs or cavies, the chinchilla, the
capybara, and many others. Humming birds are
extremely numerous, and Wallace says : "There is
no other continent or region that can produce such
an assemblage of remarkable and perfectly distinct
groups of birds ; and no less wonderful is its richness in
species, since these fully equal, if they do not surpass,
those of the two great tropical regions of the Eastern
Hemisphere combined."
6. The Palczarctic Region shows resemblances to the Paiaarctlc
Oriental, just as the Nearctic does to the Neotropical. Region
It is, however, a purely temperate region, in most re-
spects contrasting strongly with the tropical areas to
the south. Among its characteristic animals may be
enumerated the hedgehog, dormouse, chamois, and a
number of peculiar mice. The birds include a long and
varied series belonging to the thrush family, many larks
and starlings, pheasants and their relatives, etc. There
are numerous special types of amphibians, including
newts and salamanders, frogs and toads.
7. The Ethiopian Region is remarkable for the num- Ethiopian
ber of large animals, such as the African elephant, eglon
hippopotamus, giraffe, okapi, zebra, many genera of
antelopes, gorilla, chimpanzee, etc. Among the birds
we think first of the ostrich. Madagascar is included
in the Ethiopian Region, but its biota is peculiar — so
much so that some have wished to set it apart by itself.
It lacks the characteristic large animals of the African
mainland, and has a great variety of lemurs, strange
animals related to the monkeys but relatively primitive.
8. The Oriental Region is most nearly related to the Oriental
Ethiopian. Its most characteristic creatures are the Reglon
452
ZOOLOGY
Australian
Region
New Zea-
land
Indian, elephant, tiger, orang-utan, peacock, various
hornbills, etc.; From this region comes the original
type of the domes tic fowl. The desert parts of north-
western India have an essentially Palaearctic fauna,
continuous with that of Persia. The limits of the
Oriental in the direction of Australia have been much
discussed, but it is universally agreed that the Philip-
pines, Borneo, and Java are to be included ; while New
Guinea, with its birds of paradise, is classed with the
Australian Region.
9. The Australian Region is the most peculiar and
isolated, and its three principal parts, Australia, New
Zealand, and New Guinea, differ radically among them-
selves. The mammals are mainly marsupials, a very
primitive group including the kangaroo and a variety of
other types of diverse habits and appearance, one even
having the appearance and mode of life of a mole. The
egg-laying mammals (monotremes), including the duck-
bill and echidna, are even more archaic than the mar-
supials. Among the birds are the emeu, cockatoo, and
many others of remarkable appearance and habits.
The plants include the eucalpytus trees, now so widely
planted in California and elsewhere.
New Zealand lacks all the characteristic Australian
mammals, etc., but possessed very recently the extraor-
dinary giant birds known as Dinornis, and still has
the much smaller kiwis (Apteryx). These birds are
wingless, and could hardly exist in a country where
there were many predatory animals. The species of
Dinomis, or moa, were hunted by the Maoris or native
people of New Zealand, but were exterminated before
the arrival of the white man. The peculiarity of New
Zealand is further emphasized by the existence of a re-
markable lizardlike reptile (Sphenodon)-, constituting
an order not found elsewhere.
THE BIOLOGICAL REGIONS OF THE WORLD 453
10. The biological regions, as defined above, have Distribution
not always been separated as we find them today. The and^iants
study of fossils shows that in former geological epochs in past ages
the climates of various parts of the world were very
different from those now found, while both animals and
plants have migrated freely. For example, the mar-
supials, now characteristic of Australia, were once
common over the greater part of the world. The
American opossum, a true marsupial, is a relic of this
once wide distribution of the group. The camel family
was once abundant in North America. The redwood
tree, now native only in California, was formerly wide-
spread. Thus the biological regions, as we now under-
stand them, are valid only for the present epoch ; when
we go back to earlier times they must be redefined and
limited in quite other ways. Naturally our information
concerning the past is not nearly so complete as that for
the present, hence the limitations of former regions can-
not be exactly stated.
References
WALLACE, A. R. Island Life. For the differences between the Palaearctic
and Nearctic regions, see Natural Science, June, 1894.
CHAPTER FIFTY-FIVE
The life
zones of
North
America
Isotherms
LIFE ZONES
1. EVERY one knows that there are in North America
very different regions1, producing special kinds of plants
and animals. Not only do the native or wild products
of these regions differ, but of course also the crops and
conditions affecting human life. Thus we have the
corn belt and the cotton belt, the wheat country and
the grazing country, etc. Many years ago Dr. C.
H. Merriam, then of the United States Department of
Agriculture, undertook to make a careful study of this
subject, in order to determine general principles or
laws which might be of scientific and practical value.
He found out that, broadly speaking, the whole country
could be divided into a number of belts or zones, which
he called life zones, each distinguished by its fauna and
flora. This was not in itself a new idea, but it had
never before been worked out in detail, with such a
mass of data. The several zones did not, of course,
differ entirely in their products ; but when the observer
took note of a number of different plants or animals
in any locality, he usually had little difficulty in de-
termining its zonal position. Sometimes the transi-
tion was quite abrupt, as for instance at the limit of
trees in the north or on mountains, and less con-
spicuously in the limitation northward of tropical
plants which cannot endure frost.
2. These zones owe their biological differences almost
entirely to climate. From south to north, and from
lower to higher altitudes, the climate becomes colder.
The isotherms are lines running across the country,
marking the same temperature for the year or any
particular part of it. It seems at first very simple
454
LIFE ZONES 455
to define the zones by these isotherms, but the matter
is actually much more complicated. In the first place,
temperature is not the only factor ; moisture is ex-
ceedingly important. The desert and forest may have
the same mean annual temperature, may be on the
same isotherm, yet they differ entirely in their life,
perhaps hardly possessing a single species in common.
Then again, it makes a great deal of difference when the
moisture falls, and when the cold and warm weather
occur. Dr. Merriam laid special emphasis on the
total amount of heat received during the growing
season of plants, and on the other hand the minimum
winter temperature is a decisive factor for many kinds.
Even the variations between day and night are very
important. Thus in cloudy localities the temperature
in the spring may differ comparatively little during
the twenty-four hours ; but in the arid Southwest,
where the skies are clear, the rapid loss of heat at night
may give rise to killing frosts, following uncomfortably
warm days. The amount of evaporation is a factor
which cannot be ignored, and it depends upon the
moisture in the atmosphere and the movement of the
air, as well as on the actual temperature. Finally, in
some places we find what is called inversion of tempera- inversion of
ture, the tops 6f the hills or sides of the valleys being
actually warmer than the lowlands. In such a locality
as Salt River Valley, Arizona, this is due to the fact
that cold air is heavier than warm, and so sinks, dis-
placing the warmer air much as water would. Growers
of oranges know that the sides of the valley are less
liable to injurious frosts, and the value of land is,
affected by these considerations. In the vicinity of
San Francisco, California, the same general result is
brought about by the sea^ fogs. Thus the summit of
456
ZOOLOGY
Practical
value of
study of
life zones
The zones
denned
Boreal
Mount Tamalpais is drier and warmer than the Muir
Woods immediately below, and the normal relation-
ship of the zones is reversed.
3. From the above considerations it may well ap-
pear that the whole subject is so complex as to make the
definition of zones impossible. We are, indeed, warned
against a too rigid application of Dr. Merriam's prin-
ciples ; but the experience of years has shown that the
life-zone theory is not only essentially sound, but of
very great practical importance. Nature has been
experimenting for ages past ; her records are far more
complete than those of the meteorologists, and she has
determined by severe processes of selection what life
may exist in each locality. Consequently, if we study
the native biota, — that is, the wild life of a region, -
and determine that it exists under a given set of con-
ditions, then the appearance elsewhere of the same
biota comes to be an indicator of climate. Such an
indicator does not take account of single factors alone,
such as temperature, but includes everything which
is significant. Reasoning in such ways, we are able
broadly to indicate in advance what crops will be
likely to succeed in new localities, — something of
peculiar importance in a country like ours, where
agriculture and horticulture are continually extending
their boundaries.
, 4. The life zones in North America may be denned
as follows, beginning with the northernmost :
A. BOREAL (borealis, northern). This may be
divided into three zones, as follows :
(a) Arctic-alpine Zone. In the arctic regions, beyond
the limit of trees, and on mountains above
timber line. The arctic and alpine parts differ
in one important particular. Arctic regions
LIFE ZONES 457
have continuous though not intense light in
summer, and a long winter night ; but alpine
summits are lighted by day and dark by night,
as are the lowlands. Alpine heights are dis-
tinguished by the extreme beauty and great
abundance of the flowers, which are large in
proportion to the often mosslike plants which
bear them. The fauna includes such animals
as the mountain sheep and the ptarmigan, —
the latter a grouselike bird which turns white
in the winter, the color of the snow which
everywhere surrounds it.
(b) Hudsonian Zone. So called because it is well
developed in the vicinity of Hudson Bay.
It is a zone of dense coniferous forests, with
here and there a flowery meadow. In the
west it is of importance as the recipient and
conservator of the moisture which ultimately
finds its way into the streams and irrigates
the varied crops of the plains. The soil,
largely composed of vegetable debris, and
sheltered from the rays of the sun, acts as a
sponge and provides for a continual stream
flow instead of roaring but transitory torrents.
(c) Canadian Zone. A zone of mixed vegetation,
with aspens, various conifers, and small fruits
such as blackberries, raspberries, and cran-
berries. This is the first zone in which we
find crops, unless timber is regarded as a crop.
The potato, timothy grass, and some of the
more hardy cereals are regularly grown. The
glades and meadows are filled with tall and
luxuriant herbaceous plants, of the type of
vegetation known as mesophytic, — that is,
458
TJOOWGV
LIFE ZONES 459
"middle plants," of neither very wet nor very
dry ground.
B. TRANSITION. This is the most difficult to de- Transition
fine, because it is in fact a meeting place of the boreal
and austral (southern) elements. Here will be found
biological tension lines, where northern and southern,
mountain and plain, organisms press outward from
their center of distribution, and meet one another.
The Transition may be divided into three areas :
(a) Alleghanian Area. The humid Transition of the
country east of the hundredth meridian. It is
especially prominent in Minnesota, Wiscon-
sin, Michigan, New York, Pennsylvania, On-
tario, New England, and the Alleghany region.
It is a region of mixed forests : chestnut,
walnut, oak, beech, maple, etc. The decid-
uous fruit trees are highly successful : apples,
pears, plums, etc. It is a region of hops and
potatoes also.
(b) Coloradian or Arid Transition Area. This oc-
cupies large parts of Colorado, Utah, New
Mexico, Wyoming, Nevada, and the North-
west, and is for the greater part rather barren
when not irrigated. It is characterized es-
pecially by the yellow pine and the so-called
sagebrush (Artemisia). Under irrigation it
NOTE ON ZONE MAP. The Arctic or Arctic- alpine Zone, extending northward
beyond the limit of trees and on mountains above timber line, is not shown
on the map, nor are the subdivisions of the Transition Zone and the Sonoran
Area.
The diagonally shaded line marks the eastern border of the Great Plains and
divides the Austral Region into an eastern, more humid portion and a western, more
arid portion. East of the line the divisions are known respectively as the Alleghanian,
Carolinian, and Austroriparian Areas. The western portions of the same Zones are
known as the Transition, Upper Sonoran, and Lower Sonoran Areas. The Middle
Sonoran is not distinguished from the Lower Sonoran on the map.
460 ZOOLOGY
produces abundant crops, both fruits and
cereals, and also sugar beets.
(c) Columbian or Humid Northwestern Area. In the
extreme northwestern part of the United
States and adjacent parts of British Columbia,
along the coast, the climate is excessively
humid. In places the annual rainfall amounts
to 100 inches. The forests are most luxuriant,
and the country is full of life. The tempera-
ture is much more uniform than that of the
Coloradian, and there is less sunshine. Many
fruit trees do well, and roses and other flowers
grow to perfection.
Upper C. UPPER AUSTRAL.
(a) East of the Hundredth Meridian.
(1) Carolinian Area. Here the traveler from the
north first meets with the sassafras, tulip
tree, hackberry, and persimmon. It is the
great corn belt, and is in every way of prime
agricultural and horticultural importance.
One may travel in it through the states of
Ohio, Indiana, Illinois, Missouri, and Kan-
sas, reaching the limit in western Kansas.
(b) West of the Hundredth Meridian.
(2) Upper Sonoran Zone. The western zone
corresponding to the Carolinian, but very
different on account of the arid climate.
It is nearly all open country, with com-
paratively scanty vegetation. Under irri-
gation it is very prolific, and one may see
luxuriant orchards and fields, separated
only by a wire fence from desert or semi-
desert. The word "Sonoran" is derived
from Sonora, a Mexican state.
LIFE ZONES 461
(3) Middle Sonoran Zone. This combines the
crops of the Upper Sonoran with many of
the wild plants and animals of the lower
Sonoran. It is subject to severe frosts in
winter and spring, rendering it quite un-
suited to the orange, olive, and other Lower
Sonoran fruit trees. The native trees
and shrubby plants delay coming into
leaf and flower, notwithstanding the warm
days, and so escape injury. The cul-
tivated plants, coming from other regions,
have not developed this peculiarity.
Southern New Mexico is typical of this
zone.
D. LOWER AUSTRAL. Lower
(a) East of the Hundredth Meridian. Austral
(1) Austro-riparian Area. This is the cotton
belt, occupying most of the Southern
states. From it may be separated the
following :
(2) Semitropical or Gulf Strip. Along the coast
from Texas to Florida ; the region of the
palmetto and the sugar cane.
(b) West of the Hundredth Meridian.
(3) Lower Sonoran Zone. The desert region of
the extreme Southwest, characterized by
mesquite, cactus, yucca, and many other
peculiar plants, as well as a remarkable Tropical
set of animals. There is a flora of "winter
annuals," appearing in late winter and
early spring, and rapidly going to seed.
The cultivated trees, of course irrigated,
include the date palm, orange, olive,
walnut, peach, etc,
462 ZOOLOGY
E. TROPICAL. The region without frost at any
time of year. It reaches the mainland of the United
States only at the southern extremity of Florida.
Parts of southern Arizona and California, in the
valley of the Colorado River, have a mean annual
temperature which would entitle them to be considered
tropical, but they must be excluded, as they have
winter frosts. The most characteristic plant of the
tropics is, perhaps, the coconut palm, which fringes
tropical shores all round the world.
References
Cyclopedia of American Agriculture, Vol. I (1907), page 20. For details
concerning the distribution of life in North America see especially the
Bulletins of the Biological Survey, United States Department of Agri-
culture, Washington, D. C.
CHAPTER FIFTY-SIX
LIFE IN THE TROPICS
1. WITHIN the tropical zone are many different The tropical
climates. The humid forest contrasts with the grassy
uplands or mountain peaks, and the desert with both.
It is in the dense forest that we think of tropical life
as being most typically developed, and here it is that
conditions are most strikingly different from those of
the temperate zones. In such a forest we note at once
the immense size of the trees, and their closeness to
one another. Where the forest is thickest it may be
perpetual twilight on the ground. Then we observe
that the herbaceous plants so characteristic of sylvan
spots in the north are almost or quite wanting under
the trees. In any enumeration of a tropical flora, the
ground-living small plants are relatively few, and the
number of 'species of trees is astonishing. There are,
however, many woody climbing plants, and high up
in the trees one perceives the epiphytes, plants which
live on the trunks and limbs, never reaching the ground
below. Many of these latter are orchids, some of
them with magnificent flowers. Yet the general im-
pression gained is that of greenness, without much
color. The bright flowers are dotted here and there,
often so far aloft that they cannot be seen. There is
nothing like the gay carpet of color to be seen any
spring in a European or American glade, or on the
summits of high mountains during the short summei
season.
2. In temperate regions it is common to find forests Diversity of
consisting mainly of one kind of tree — pine or oak,
beech or chestnut. In the tropics there is amazing
diversity, and when a specimen of a particular tree has
463
464 ZOOLOGY
been found, -it may be necessary to go half a mile to
find another. A Dutch botanist records finding 600
species of arborescent plants in an area of about i£
square miles in the Malay Archipelago. When Pro-
fessor Beccari was building a small house in the Bornean
forest, he found three small trees in such a position
as to be exactly suitable for corner posts. So he cut
off the tops, and secured a fourth post for the remaining
corner. On looking at the tops he had removed, he
found that his three trees were all of different genera
and all represented species new to science. It will
readily be understood that under the conditions de-
scribed the "struggle for existence" is extreme. Each
plant produces a multitude of seeds, but few of these
ever grow into mature plants. The two most necessary
things are room and light. There is no space for new
trees until the old ones die. Then they are rapidly
destroyed by insects, fungi, and bacteria, and there
is a scramble to secure the open space. Epiphytes,
living far aloft, may secure access to light which they
could not have lower down. Certain trees of the fig
group, called "malo palo" or bad tree in Guatemala,
by means of their great aerial roots surround great
trunks in the forest and eventually strangle and destroy
their victims, — trees of other species, — in order to
take their place.
3. Such luxuriance and variety of vegetation makes
possible a corresponding variety of animal life. In-
sects, in particular, are extremely numerous and varied.
All those creatures which feed on vegetation become
adapted to particular kinds of trees and other plants.
Thus a given tree will have its special fauna, feeding
on the roots, trunk, branches, leaves, or visiting the
flowers. The creepers which ascend the trunk will
LIFE IN THE TROPICS 465
likewise support a series of small creatures ; so also
the epiphytic orchids and Tillandsias. Thus a single
tree, with its accompanying smaller plants, supports
a great population of insects, snails, centipedes, etc.
When the trees are so varied, jt will readily be under-
stood that the fauna must be enormous. A Colorado
high school teacher, a few years ago, secured a leave of
absence from her school to visit Guatemala. She was
away six weeks, two of which were occupied by the
journeys, coming and going. In the month she had
in the country she was able to discover 78 species and
varieties new to science, including a large and beautiful
tree, a snail, several protozoa, and a great number of
insects.
4. One might suppose that the study of tropical Tropical
life, owing to its variety and complexity, would be usuaUy
extremely difficult. It is anything but easy, but the defined
naturalist who has struggled with the poorly defined
species of temperate regions turns with relief to the
tropical biota, where the different forms commonly
possess recognizable or even conspicuous characteris-
tics. In the tropics it appears that conditions must
have remained substantially the same during long ages,
while the intense struggle for existence has hewed,
as it were, each species very closely to the line of
optimum efficiency. Thus characters have become
stereotyped, species fit exactly into their niche in the
architecture of nature, and general variability is likely
to be suppressed. In temperate regions we are re-
covering from the last glacial period, species are still
plastic and in the making, at least in many genera, and
it is difficult to define them exactly, for the reason that
Nature has not done it. In large collections from the
tropics, for example of wild bees, it often appears that
466 ZOOLOGY
certain species are extremely variable ; but on closer
examination this seems to be illusory. There are, in
fact, very numerous allied species, each occupying its
own area and uniform within it. *
special 5. Certain parts of t^he tropics are famous for the
abundance of particular groups of creatures, as all
collectors know. Thus for snails we go especially to
the Philippine Islands, the Hawaiian Islands, Cuba,
or Jamaica ; for ferns, to Jamaica. Butterflies are ex-
cessively numerous in South America. If we care for
rats, the Malay Archipelago will supply almost un-
limited numbers of species. In general, continental
areas are much richer in species than are islands, if
we except certain groups. There is no part of the
tropics which will not reward an industrious collector
with numerous novelties, and many generations of men
must pass before the biota of the richest regions of the
world is adequately catalogued. The best treatment
of a single tropical area is found in the series of volumes
on the Fauna of British India, published by the British
Government, but this is still very incomplete. The
Biologia Centr all- Americana is a great work on the
animals and plants of Mexico and Central America, —
a splendid contribution to science, but very costly, and
enumerating only a fraction of the life really existing
there.
References
WALLACE, A. R. The Malay Archipelago.
RODWAY, JAMES. In the Guiana Forest. Second Edition, 1912.
ROOSEVELT,. THEODORE. Through the Brazilian Wilderness. 1914.
SPRUCE, RICHARD. Notes of a Botanist on the Amazon and Andes. 1908.
CHAPTER FIFTY-SEVEN
LIFE IN THE ARCTIC AND ANTARCTIC REGIONS 1
I. THE frozen north, and the still more frozen south, The struggle
are in most respects ill-suited for the development of ^^ent1"
terrestrial life ; yet they are of special interest to the
biologist. In the moist tropics, where life is most
abundant, it is its own chief enemy. Plant struggles
with plant, animal with animal, animal and plant
together. In the arctic, as in the desert, the principal
struggle is with the environment. There is generally
room enough, but how to endure the climate, to sur-
vive under such hard conditions, is the real problem.
Nature, however, makes the most of every opening, and
develops types which are so well adapted to seemingly Adaptation
adverse conditions that they cannot get along without
them. Thus the polar bear, accustomed to a world of
ice, looks hot and mise.rable in the London Zoological
Gardens, during the very temperate English summer.
2. The north polar regions are radically different Life in the
from the south, in that the north pole is covered by a
frozen sea, whereas the south is in the middle of a great
area of elevated land. We might at first imagine that
land would be more favorable to animal life than sea,
but this is not the case. The sea, even in the extreme
north and south, is full of animal life, — whales,
fishes, and invertebrates'. The fishes may feed on
minute Crustacea or worms, the seals on fishes, the
polar bears on seals. Aquatic plants, mostly of
minute size, serve as food for the smaller animals.
Thus the sea is a source of food for so-called terrestrial
animals, which may live mainly upon the ice. In
1 The word "arctic" comes from arctos, Greek for "bear." Hence the
careless spelling "artic," a prevalent vice of students and others, is es-
pecially to be condemned.
467
468
ZOOLOGY
the midst of the antarctic continent there is no such
source of food, and consequently life is practically
confined to areas near the coast. Were the tempera-
ture of the whole earth to fall to that of the polar
regions, life would persist in the oceans and along the
coasts of the continents, but the interior uplands would
be barren and desolate.
3. Nansen tells us how he found the arctic ice
teeming with thousands of millions of microscopic
organisms. The sun melts the snow, forming pools
on the ice, and these soon show yellowish-brown spots,
at first small, but gradually increasing in size. These,
under the microscope, are seen to consist of minute
plants, principally diatoms. Each spot represents an
enormous population, a little city of these simple
organisms. Also present, feeding on the plants, are
many different kinds of protozoa. Thus the frozen
north, apparently so barren, is really full of life, —
life which prospers and finds no hardship in the con-
ditions which exist. Under the ice, in the sea, are many
other creatures.
4. The higher, more conspicuous life of the north is
much better known. Every one has heard of the
polar bear, the walrus, the arctic fox, and the musk ox
of Greenland. So also there are many birds, some of
them common visitors to more southern regions in the
winter. The beautiful Ross's gull, with rosy breast,
is called by Nansen a "rare and mysterious inhabitant
of the unknown north, only occasionally seen, and
no one knows whence it cometh or whither it goeth."
Some of the arctic animals are white, like their surround-
ings, others quite the reverse. To be white is to escape
observation, as when the polar bear creeps soft-footed
toward the seal ; but the musk oxen, living in herds,
LIFE IN THE ARCTIC AND ANTARCTIC REGIONS 469
and quite well able to take care of themselves, would
gain little from inconspicuousness. Indeed, it is doubt-
less an advantage, if an animal chances to get lost,
that it can easily see and be seen by its fellows.
5. In Siberia and Alaska there is a profusion of Arctic in-
insect life in the summer, especially of mosquitoes, flowers*
All travelers in these regions agree in describing the
clouds of mosquitoes, which make it necessary to wear
a veil, and render life almost unendurable at times.
Wallace points out that no less than 173 species of
birds breed in the arctic regions, and that a principal
source of food for the young must be these insects,
which thus become a very important factor in support-
ing a large number of valuable and interesting birds.
Also, the arctic tundra is gay in summer with beautiful
flowers, and many wild fruits exist, affording further
nourishment to the hosts of birds. These things, of
course, are found only on the land areas, and only
where the summer temperature is high enough to stim-
ulate growth. There is nothing of the kind in the south
polar lands, which support only very simple organisms,
aside from those living in the sea or getting their living
out of the sea.
6. Although the south polar region has no bears, Southern
foxes, or musk oxen, there are plenty of seals. There vertebrates
are also penguins in great numbers. In the account of
Scott's expedition these birds are described at length,
with illustrations from photographs. In 1911 several
members of Scott's party made an extremely difficult
and hazardous journey to secure the eggs of the Em-
peror Penguin. They were away from the main camp
from June 27 to August i, which is the middle of the
antarctic winter. They found the birds sitting on
their eggs in a temperature 20 to 30 degrees below
470
ZOOLOGY
Resem-
blances
between the
arctic and
antarctic
biota
Former
warm
climates in
the polar
regions
zero, and secured the specimens necessary for the
study of the early stages. This was particularly im-
portant, since the Emperor Penguin is perhaps the
most primitive of all living birds. That any species
of bird should reproduce in the middle of the long
winter night, with the temperature far below zero,
would seem incredible were it not proved by the most
reliable testimony. The species of penguins occupy
the shores of far southern lands, and find their food in
the sea.
7. Arctic and antarctic life differ very conspic-
uously, especially as regards the larger animals. When
we come to the smaller forms, and especially those
found in the sea, there are many resemblances which
have caused surprise. Separated by a broad tropical
zone, it would not seem likely that any species could
pass from one polar region to the other. Hence it
has been suggested that perhaps the similarity might
be due merely to the likeness of the environment,
causing similar forms to develop independently. It has
been remarked, however, that even under the equator
the depths of the sea are cold, and currents flowing
along the ocean floor might carry cold-water organisms
right across the tropical belt.
8. At one time, or indeed at more than one time,
in the past, the arctic and antarctic regions were rela-
tively warm and supported luxuriant vegetation. This
is shown by the numerous fossil plants found in Green-
land and Spitzbergen, and by the remains more recently
collected in Antarctica. On the return from the south
pole, Dr. Edward A. Wilson found fossil plants far
in the interior, and the party, with the greatest pluck,
dragged the specimens, under almost incredible diffi-
culties, to the camp where they finally perished. The
LIFE IN THE ARCTIC AND ANTARCTIC REGIONS 471
specimens were found with the bodies of the explorers,
and serve to prove that even this frigid country once
enjoyed a mild climate.
References
NANSEN, FRIDTJOF. Farthest North. A. Constable & Co. 1897.
Scott's Last Expedition. Dodd, Mead & Co. 1913.
WALLACE, A. R. The World of Life. Moffat, Yard & Co. 1911. Pages
HS-I59-
CHAPTER FIFTY-EIGHT
The sea the
Marine and
terrestrial
life con-
trasted
LIFE IN THE SEA
1. THE sea occupies the greater part of the world's
surfacej anj teems with varied forms of life. The
oldest known fossils appear to be exclusively marine,
but these have gone far along the path of evolution.
The beginnings of life were certainly associated with
water, but they may have been in the soil, which is
still occupied by a great variety of organisms scarcely
known even to naturalists. However this may have
been, the sea is nevertheless the great mother of life,
the source of many great groups, some of which have
emerged from the waters to occupy the land. The
reverse process, the adaptation of land groups to marine
existence, is much less common. The whales and
porpoises are mammals, certainly with terrestrial
ancestors. A few species of mollusks, living near the
shore, show characters indicating their relationship
to land snails. Some true snakes, not the sea serpents
of fable, are sea dwellers. There are hemipterous
insects which skim the surface of the open ocean, but
are related to inland forms. All such instances,
taken together, are relatively few, whereas the whole
arthropod phylum, for example, appears to have first
developed in the sea.
2. There is, however, the strongest contrast between
the character and evolution of marine and terrestrial
life. In particular, the plant and animal kingdoms
occupy very different relative positions. At first sight
it might well appear that the sea is the home of animals,
the land of plants. Plant life in the sea consists almost
wholly of lowly forms, — sometimes gigantic, as the
kelp of the Pacific coast, but flowerless and anything
472
LIFE IN THE SEA 473
but highly organized. Such an exception as the Zostera,
which really has minute flowers, obviously represents
a modified form of inland ancestry. Closer examina-
tion shows that the conspicuous seaweeds are confined
to the coast belt and certain areas where floating
species exist. The greater part of the ocean is without
noticeable plant life, though the upper layers are full
of minute diatoms and other equally inconspicuous
though by no means insignificant types. The sunless
depths have no plants at all. Every part of the sea,
on the other hand, 'supports animal life. It abounds in
the far north and south, where land life is scarce. It
exists in the abyssal depths, which occupy nearly half
the earth's surface. It includes great numbers of
groups, such as the starfishes,* crinoids, and lamp
shells, which have no terrestrial or even fresh-water
analogues. In the past it was the same. The rocks,
dating back millions of years, are full of marine shells,
echinoderms, fishes, and the rest, but we rarely find
recognizable plants in sea deposits.
The land, on the other hand, is often covered with
forests. The higher plants are all terrestrial. Animal
life on land, in spite of its high development, seems
almost secondary to the flora. Only in towns do the
animals (principally Homo sapiens) appear to exceed
the plants. Rocks formed inland often contain plant
remains in great .variety, without a single animal.
3. Looking out upon the ocean, we get the impres- The littoral
sion of extraordinary uniformity. North, south, east,
and west, wherever the sea extends, we find a waste
of waters, — without mountains, without valleys, with-
out forests or rivers. It is only after close study that
we appreciate the erroneousness of this superficial
view. There are currents in the sea, flowing like
474 ZOOLOGY
rivers ; the most famous is the Gulf Stream. The
surface conditions are very different from those below,
and the coasts are unlike deep waters. The zone along
the coasts, known as the littoral zone, is narrow, some-
times very narrow. It may be defined as that area
in which a considerable amount of light penetrates to
the bottom. There is the region between the highest
and lowest tide marks, and a variable extension
beyond the level of the lowest tide, until we reach
really deep water. Here the large red and brown sea-
weeds grow in abundance, and animals are often
brightly colored. Here, in the tropics, are the coral
reefs. Organisms belonging properly *to the littoral
zone are confined to singularly narrow limits, as if in a
gigantic river. Most of the long coast lines extend
north and south, and consequently the littoral fauna
is blocked in its migrations north and south by climatic
changes. These changes may be quite abrupt, owing
to the meeting of warm and cold currents ; thus the
faunas north and south of Cape Cod and- on the
Pacific coast, of Point Concepcion are markedly dif-
ferent. This confinement to a relatively narrow area
makes the species of marine animals more local in their
distribution than we might at first expect. In many
cases, however, the animals have free-swimming early
stages, which are carried out to sea by the currents,
and may reach remote islands or other continents. Of
such larvae, setting out for the unknown, nearly all
perish, but a few survive and establish their kind on
other shores. Nature, as the poet said, is careless of
the single life, but careful of the race.
4. The floating organisms of the open sea, or even
of the surface layers of a lake, are known collectively
as the plankton. Properly speaking, the plankton in-
LIFE IN THE SEA 475
eludes those creatures which are more or less passively
carried by the movement of the water, and are not far
from the surface. At first sight it might seem that
such forms were few and of little interest. From the
deck of a vessel one sees an occasional jellyfish, frag-
ment of seaweed, or, if fortunate, a "Portuguese man-
o'-war" (Physalia). Better indications of the abun-
dance of the plankton are obtained at night, when the
wake of the ship glows with the phosphorescent light
of small organisms. If, however, the fine-meshed
plankton net is used, dragged not* too rapidly along in
the surface waters, it is found to contain a whole popu-
lation of animals and microscopic plants. These, on
being sorted out, are found to belong to many different
phyla, classes, orders, and families. Some are very
young forms of littoral or bottom species, others are
permanent inhabitants of the plankton layers. Many
are transparent, or delicately tinted with blue, so as to
be almost invisible, though of fair size.
5. At various levels between the surface and the bed The nekton
of the ocean will be found a number of free-swimming
animals, mostly fishes. These are collectively known
as the nekton. Unlike the typical plankton, they
move freely through the water, and are not drifted
hither and thither by the currents and tides. Much
of this nekton fauna is hard to catch, and our knowl-
edge of it is correspondingly imperfect. We know,
however, that there are great diurnal and seasonal
migrations of many species, so that they may appear
near the surface at certain hours, and at others be far
below ; or they may travel from one locality to another.
These movements are of the greatest importance for
the fishing industry, and in Europe an international
organization was investigating these and other prac-
476 ZOOLOGY
tical problems with great success, until the war put a
stop to the cooperative plans. In the efforts to trace
the migrations of fishes, very elaborate methods have
been devised. Thus it has been possible to learn much
about the mackerel and herring by carefully measuring
thousands of individuals, in order to distinguish the
slightly different races. Also, especially in the case
of the salmon, the seasonal markings on the scales have
afforded a clew to the habits and movements of the
fish. The movements of the smaller animals, such as
the Crustacea, also prove to be important, since these
furnish food to fishes.
The benthos 6. On the floor of the ocean is the assemblage of
organisms called the benthos. It occupies different
levels and environments, according to the depth. The
deep-sea animals feed on one another, but existence on
this basis alone would be as difficult as that in the
mythical island where all the inhabitants got a living
FIG. 205. Foraminifera tests from the bottom of the North Atlantic Ocean;
magnified about 10 diameters.
LIFE IN THE SEA 477
by taking in each other's washing. Ultimately, the
source of food is the plant life of the plankton, or the
organic materials washed from the littoral zone or the
rivers. There is a continual rain of minute organic
particles from above, slowly sinking to the bottom.
Along with this falls the multitude of shells or tests of
radiplaria, foraminifera, and diatoms. Thus the open
ocean comes to have its floor composed of such material
as the radiolarian ooze, composed of millions of minute
tests of these Protozoa. In the deeper seas, life at the
bottom exists under peculiar circumstances. It is very
cold, and entirely dark, except for the phosphorescence
of the animals themselves. The pressure of the water
is enormous, but the animals do not feel it, since
their internal fluids have a density to correspond. On
being quickly drawn to the surface, however, they
tend to explode as it were, to fall to pieces. It is not
always easy to determine whether fishes have been
caught on the bottom, or were captured as the net was
being drawn up. Thus, for example, the fish Alepo-
cephalus has been taken by many deep-sea expeditions,
and was regarded as a typical example of the benthos
of the depths ; but on one occasion a tow net was
dragged about a thousand meters above the bottom,
and an Alepocephalus was captured.
7. The fauna of the sea affords endless opportunities Ourimper-
to the naturalist who wishes to solve scientific and edge of sea
economic problems. Even the easily accessible littoral Ufe
fauna of our own shores is still imperfectly known ;
thus many new mollusks have been described from
the coasts of California in recent years. The life
histories of innumerable forms remain to be investi-
gated. When we come to the deep sea, the extent of
the problem is almost appalling. So far, we have
ZOOLOGY
been able to glean only about as much as we might of
the land if a few balloons dragged nets over the sur-
nd
From Perrier's " Traite de Zoologie "
FIG. 206. Two deep-sea fishes, Thaumatostomias atrox (lower) and Stomias boa
(upper) : o, eye ; k, luminous placques ; /, luminous spots ; c, canine teeth ; b,
barbels ; Ig, tongue ; np, pectoral fins ; nd, dorsal fin ; na, anal fin ; nv, ventral fin.
face of the country on dark nights. How poorly the
small collections of miscellaneous fragments thus ob-
tained would represent the life of the earth ! In the
case of the sea bottom, especially of the greater depths,
dredging is so expensive and laborious that it can hardly
be undertaken except by governments. Even with
public funds, it is possible to explore only an infini-
tesimal part of the ocean bed within a lifetime.
There is thus an endless fascination and mystery about
the sea, and the wonders of the deep will probably
continue to furnish materials for investigation as long
as mankind exists.
References
MURRAY and HIORT. The Depths of the Ocean. Macmillan, 1912.
JOHNSTONE, JAMES. "Life in the Sea," Cambridge Manuals of Science and
Literature, 1911,
CHAPTER FIFTY-NINE
LOUIS PASTEUR
I. IT is related that one of the Paris newspapers, Pasteur's
service to
mankind
many years ago, asked its readers to vote on the ques- semceto
tion : Who is the greatest living Frenchman ? When
the ballots were counted, it was found that the choice
had fallen, not on a soldier or politician, but on a plain
man of science. It was Louis Pasteur who thus appar-
ently held the first place in the hearts of his countrymen
- Pasteur, who had killed no one, but had been the
means of saving thousands ; who had accumulated no
riches, but had enriched whole departments. Probably
at no other time, and in no other country, could science
have thus been recognized by the people. Neverthe-
less, as Pasteur himself would have insisted, she con-
stantly deserved such recognition. Pasteur was one of
a multitude of investigators, preeminent but not iso-
lated. He stood as the purest example of a type which
existed in all civilized countries.
2. Louis Pasteur was born at Dole, France, in 1822. Early life
His father was a tanner, a man of quite moderate J£Jne uca"
means. As a boy at school, Louis was at first con-
sidered rather slow, because he never hastened to con-
clusions or affirmed what he did not know. Scientific
caution seems to have been part of his nature. He
early developed a taste for drawing, and after a time
his pastel portraits of local celebrities gained him in the
vicinity of his home quite a reputation as an artist. At
the age of eighteen he became an assistant master in the
college at Besancon, with a very small salary. At the
same time he continued his studies, looking forward to
the Ecole Normale in Paris, which he entered in 1843.
Here he came in contact with eminent scientific men,
and soon became absorbed in the study of chemistry.
479
480 ZOOLOGY
Researches 3. It was during this period that Pasteur made his
first scientific discovery. There is an instrument called
the polariscope, which may be used to test the strength
of various substances in solution, such as sugar or tar-
taric acid compounds. The rays of light, passing
through the apparatus, are deflected to the right or left,
according to the nature of the substance used. The
chemists had worked out a theory of polarization, but
there remained a stumbling-block, which no one had
been able to remove. Paratartrate solutions, quite con-
trary to expectation, were neutral, deflecting the light
neither this way nor that. We said that Pasteur early
exhibited scientific caution, but this means only that
he worked carefully, making sure of each step. He had
little or none of that so-called caution which frightens
a man away from a difficult task. The fact that
others had failed was for him a reason for attacking a
problem. So he took up the paratartrate puzzle, and
presently discovered that when the substance crystal-
lized out, the crystals were not all alike. They were
asymmetrical, and one set was the reverse or looking-
glass image of the other. Did this mean anything ?
Separate solutions were made of the two kinds, and
immediately the problem was solved. One kind rotated
the light to the right, the other to the left, and when
they were mixed, they neutralized "each other! How
very simple ! — but none of the chemists who had
previously investigated the subject had thought of it.
Pasteur and 4. There was an old and eminent chemist in Paris,
named J. J. Biot. On hearing of Pasteur's discovery
he expressed incredulity, and wished to see the thing for
himself. So one day the young man called at the
College de France, and was admitted into Biot's labora-
tory. Biot himself prepared the materials ; he would
LOOTS PASTEUR
48l
take no risk of being deceived. In his presence Pasteur
picked out the crystals, and stated the expected results.
FIG. 207. Louis Pasteur.
When it all came out exactly as he said, Biot took
Pasteur's arm and said : "My dear boy, I have loved
science so much during my life, that this touches my
very heart!" Thenceforth Pasteur had a faithful
friend and supporter in this influential old man.
5. In 1849 Pasteur went, as professor of chemistry, to Marriage
the academy or college at Strasburg, which was then in
French territory.1 He had not been there long, when
he fell in love with Mademoiselle Marie Laurent, the
1 As a result of the recent war, it is once more a French city.
482 ZOOLOGY
daughter of the rector of the academy. In a formal
letter to M. Laurent, he outlines his prospects, and an-
nounces that unless his tastes should completely change,
he will give himself up entirely to chemical research.
Fortune he has none ; what should come to him from
the family estate he gives to his sisters. His father will
come to Strasburg to make the formal proposal of mar-
riage. At the same time, Pasteur ventures to send a
more intimate note to the girl's mother. "I am afraid
that Mile. Marie may be influenced by early impres-
sions, unfavorable to me. There is nothing in me to
attract a young girl's fancy. But my recollections tell
me that those who have known me very well have loved
me very much." In due course of time they were
married, and we are told that Mme. Pasteur was from
the first willing to spell science with a capital S.
Deanat 6. In 1854 Pasteur became dean of the new faculty of
sciences at Lille. He entered upon his new work with
great enthusiasm, developing the then novel plan of
laboratory instruction. He made an opening address
to the parents and students, in which he exclaimed :
"Where will you find a young man whose curiosity and
interest will not immediately be awakened when you
put into his hands a potato, when with that potato he
may produce sugar, with that sugar alcohol, with that
alcohol ether and vinegar ? Where is he that will not
be happy to tell his family in the evening that he has
just been working out an electric telegraph ? . . .
Your sons will not forget what the air we breathe con-
tains when they have once analyzed it, when in their
hands and under their eyes the admirable properties of
its elements have been resolved !"
spontaneous J. With all this zeal for teaching, Pasteur did not
generation negject his own researches. He presently attacked
LOUIS PASTEUR 483
what was then supposed to be an insoluble puzzle, that
of "spontaneous generation." Did life, in the form of
corpuscles or germs, come into existence without having
any parents, any ancestors ? Many had debated the
matter, and wise men had set it aside as incapable of
solution, — a subject for cranks, like perpetual motion.
This did not discourage Pasteur, nor was he willing to
desist when his old friend Biot warned him earnestly
that he was wasting his time. After a series of simple
but brilliant experiments he was able to prove that the
organisms of fermentation and decay,' which were sup-
posed to originate in liquids containing organic matter,
actually came from the air. Boil the liquids and then
exclude the air, and no fermentation takes place, no
organisms appear. Thus, after years of futile debate,
the matter of spontaneous generation was settled by
experiment. Many years before, one Spallanzani, an
Italian, had reached similar conclusions, but Pasteur's
experiments were far more varied and decisive. The
matter was not of merely theoretical interest : the fact
demonstrated by Pasteur makes possible the canning
industry of modern times.
8. On the same principle, Pasteur was now able to Diseases of
investigate the "diseases" of wines, which cause them wmes
to spoil on keeping. The exportation of French wines
had seriously fallen off on account of the difficulty of
keeping them in various climates. The trouble was due
to parasitic plants, germs, or corpuscles ; or, as we should
now say, yeasts or bacteria. These could be destroyed
by heating, and thus the difficulty was overcome.
9. In 1865 a new calamity was ruining the silk in- Silkworm
dustry in France. The silkworms perished from two dlseases
different diseases. Pebrine caused the worms to become
spotted (the word signifies "peppered") and dry up like
484 ZOOLOGY
mummies. In flacherie, on the contrary, they dis-
solved into a liquid mass. In either case they perished,
and others, brought to replace them, went the same
way. J. B. Dumas, a senator of France, was begged to
find some one to investigate the matter, and he had no
hesitation in choosing Pasteur.. People said, who is
this chemist, brought here to save the silkworms, of
which he knows nothing ? Pasteur had, in fact, never
seen a silkworm cocoon, and was astonished when the
entomologist Fabre explained to him that it would pro-
duce a moth. Nevertheless, he knew a great deal
about germs of diseases and fermentation, and had no
difficulty in perceiving that there existed epidemic,
contagious diseases. The proper methods were fairly
obvious in the light of what he knew, — to get rid of all
diseased insects, and start afresh, with all sanitary pre-
cautions. Yet people would not believe in this com-
paratively simple solution, and Pasteur wished to
demonstrate his method on a large scale. He obtained
control of an estate belonging to the Emperor Na-
poleon III, and was able to show the practical value of
his ideas in a manner sufficiently public to attract gen-
eral attention. The silk industry was saved, and with
it the livelihood of thousands of peasants.
Pasteur and io. The Emperor interviewed Pasteur, and expressed
the Emperor surprise tnat ne did not make money out of his dis-
coveries. One who could save silk and wine from de-
struction might well be a millionaire. No, said Pasteur,
it is impossible. As soon as one task is accomplished,
he must turn to something else, trying to do as much as
possible in a short human life. To think of profit would
be ruinous to all this. It was sufficient to benefit France,
but he did wish to have the means of doing this to the
utmost. Carrying out the same idea, we find him begging
LOUIS PASTEUR 485
the government to build new laboratories. At length a Antiseptic
building was in course of erection, when Pasteur fell ill,
and many thought he would die. The work stopped, for
without him there seemed no object in continuing. It
was necessary to appeal to the Emperor to have the build-
ing operations resumed, and in the meanwhile Pasteur
gradually recovered and was able to return to his labors.
ii. During the Franco-Prussian War of 1870, Pas-
teur noted with distress the frightful mortality among
the wounded. Even slight injuries produced fatal
results. Operations in certain hospitals were commonly
followed by death. With all his experience in dealing
with putrefactive changes, Pasteur fully realized that
the trouble was due to bacteria or germs. He could
reason from the silkworms to mankind, and recommend
the proper sanitary measures. He could see how the
surgeons, coming to save life, carried the cause of death
on their hands and their clothes. Pasteur, however,
was not a medical man, and could not carry out his
ideas in practice. Neither could he convince the
medical profession, which was by no means ready to
take advice from an outsider. It remained for an
English surgeon, Joseph Lister, to adopt Pasteur's
ideas, and develop in a practical way a system of anti-
septic surgery. Lister revolutionized surgical practice,
though not without meeting a good deal of opposition,
and he never failed to express his debt to Pasteur. The
saving of life through the new methods has been in-
calculable. Not only do the wounded recover in large
numbers, but operations which formerly would have
been deemed impossible are now easy. For example,
the operation for appendicitis, now considered hardly
dangerous if done in time, would before the time of
Lister have been only a last desperate resort.
486
• ZOOLOGY
Anthrax
The
vaccination
of sheep
12. In 1877 Pasteur undertook to combat the
anthrax or charbon disease, which was killing great
numbers of cattle and sheep. There were places where
half the sheep in a flock perished. Even human beings
were occasionally attacked. No one knew what to do.
The disease was due to a relatively large bacillus, very
difficult to destroy. This organism was isolated and
described by Dr. Koch of Germany. Pasteur de-
veloped a method of vaccination, following the general
plan employed for smallpox. It is not necessary here
to describe his methods of preparing the "attenuated
virus," which he injected into the animals to be pro-
tected. The theory of vaccination is based on the fact
that the body is able to develop substances which com-
bat or neutralize the poison, and that if it is warned by
a weak dose, it will be ready to withstand a strong one.
The function of vaccination, then, is not unlike that of
the Scotch thistles or the geese at Rome, famous in his-
tory. The notion of vaccinating sheep did not com-
mend itself to the veterinarians, and, as in the case of
the silkworm disease, Pasteur sought a public demon-
stration. The Melun Agricultural Society put sixty
sheep at his disposal. Twenty-five were to be vacci-
nated twice, and later inoculated with virulent anthrax.
Twenty-five others were to be inoculated without vacci-
nation. Ten, untreated, remained to show that the
flock was normal. Now, said Pasteur, the unvacci-
nated sheep, on being inoculated, will perish. The
vaccinated ones, also inoculated, will remain healthy.
After anxious days, during which even Pasteur feared
that something would go wrong, the experiment proved
successful, and the whole population joined in applause.
Once more an important industry had been saved from
destruction.
LOUIS PASTEUR 487
13. One more great task remained. The disease Hydro-
called rabies or hydrophobia, communicated by the bite phobia
of a dog, had resisted all attempts at treatment. It not
only caused perhaps the most frightful death known to
medical science, but was the source of terrible anxiety.
After being bitten, an individual did not know for many
months whether he would get the disease, so slow was
its development. The cause, now understood to be a
minute protozoan, was not. known in Pasteur's time.
Pasteur saw, however, that the problem was analogous
to that of the other germ-produced diseases, and won-
dered whether a vaccination method could succeed.
Obviously, one could not vaccinate the whole popula-
tion, of whom only a minute fraction would be likely
to be bitten by a rabid dog. It was possible, by using
rabbits, to prepare attenuated virus and thus carry out
the plan of vaccination. Why not vaccinate after the
bite, and get ahead of the slowly developing virus,
which gradually made its way to the central nervous
system ? This might succeed, if too much time had not
elapsed and the bite was not too near the brain. The
method was worked out successfully with animals, but
Pasteur dreaded applying it to a human being, not
knowing whether the reactions would be the same. In
July, 1885, there came to the laboratory a little Al- Joseph
satian boy, Joseph Meister, accompanied by his mother. Meister
The child had been bitten in fourteen places by a mad
dog, and could not be expected to escape the disease.
Friends, knowing of Pasteur's experiments, had advised
Mme. Meister to appeal to him. He did not know
what to say, but after a consultation with his colleagues,
resolved to attempt the new treatment. The inocula-
tions, by means of a hollow needle, were at first very
mild, but increased in virulence as time went by. Pas-
488 ZOOLOGY
teur, dreading evil consequences, spent sleepless nights.
It was impossible to draw back ; the experiment must
be brought to its conclusion. Finally, amid the en-
thusiasm of all, Joseph Meister was pronounced safe,
Closing and the Pasteur treatment for hydrophobia was proved
as sound in practice as it had appeared in theory.
Money was subscribed, and facilities were provided for
the treatment of all bitten persons. The movement
eventually spread to other, countries, and now almost
every part of the civilized world has some laboratory or
institute devoted to this and similar work.
14. Some years still remained to Pasteur, but toward
the end his health failed, and he could work no more.
He was surrounded by his colleagues and pupils, who
were carrying on the work he had begun, and extending
it in every direction. On one occasion they organized
a celebration, when Pasteur, seated by the fire and un-
able to move, received the old students of the Ecole
Normale. In the laboratory, on tables, were arranged
the little flasks which Pasteur had used in his experi-
ments on spontaneous generation, little tubes used in
the investigation of wines, various preparations of in-
fectious germs. At about noon they carried Pasteur
into the laboratory, and Dr. Roux, his most brilliant
student, showed him the. newly discovered bacillus of
plague. "There is still a great deal to do !" said Pas-
teur, as he looked at these things, thinking of the
disciples who had gone out from his laboratory to all
parts of the world. After this, his strength gradually
ebbed away, and he died on September 28, 1895.
Reference
VALLERY-RADOT, RENE. The Life of Pasteur. Doubleday, Page & Co.
CHAPTER SIXTY
DISEASE IN RELATION TO HUMAN EVOLUTION
1. IT is well known that the rate of evolution in The slow
various groups of animals differs greatly. Thus the
insects have changed much more rapidly than the Pro-
tozoa, the mammals more than the insects. Man being
a highly specialized mammal, we might naturally expect
to find some evidence of evolution in the many thou-
sands of years of his existence. It is true that the
Neanderthal man, of extremely remote times, is so dis-
tinct that he is regarded as a separate species ; but his
successor, the Cro-Magnon man, still belonging to the
prehistoric period, was a being like ourselves. The
finely formed skull is -in no way inferior to that of
modern races, — is, in fact, superior to some of them.
Within historic times new races have arisen, like the
English, from the mingling of old ones ; but there has
been no apparent forward evolution in physical struc-
ture. The most we can say is that there has been a
shuffling of characters, and probably among civilized
nations a slight increase in average size, owing to better
nutrition. Man is a variable animal, and his funda-
mental constancy of type during such a long period may
well be used as an argument against the existence of any
inherent tendency to progressive modification.
2. Is it a fact, then, that man has remained exactly Evolution in
what he was, except for the mingling of races ? Dr.
Archdall Reid remarked some years ago that if we
wished to determine the direction of modification, we
should look for the causes of death. In other words,
such modification as may occur is not due to inherent
tendencies to change, but to a selective agency acting
in the presence of heritable variations. Since individ-
489
490 ZOOLOGY
uals who leave no offspring are the true dead from the
evolutionary standpoint, the selective agencies must be
various. Yet it is evident that the most important
factor is disease, particularly the group of diseases due
to bacteria. Throughout the centuries, consumption,
smallpox, measles, and the rest have attacked mankind
and carried off those unable to resist. It is well known
to all that the susceptibility to particular forms of
disease varies greatly, and while this is partly due to
physical condition resulting from environment, it is
largely a matter of inherited constitution. This is so
true that it used to be supposed that consumption was
inherited, whereas we now know that what is inherited
is susceptibility to that disease. Even among plants
the same rule holds ; thus a particular strain of wheat
is readily attacked by the rust fungus, while another
is practically immune. The consequence of these
selective processes is the survival of those individuals
whose heredity is favorable for resistance, and the pro-
duction of a relatively immune type. If there are no
resistant individuals to be selected, the species may of
course become extinct.
3. The races of mankind afford abundant evidence
of adaptation, which we can suppose to have arisen
only in the manner described. Thus in tropical Africa
the negroes suffer very much less from malaria than the
white man, while in the north the white man is more
resistant to consumption than the black. There are
two different types of adaptation: a race may be im-
mune or tolerant. If immune, it does not take the
disease, does not harbor the parasite. If tolerant, it
may readily become infected but suffers little in conse-
quence. In West Africa the negro children carry in
their blood the parasite of pernicious malaria, and thus
DISEASE IN RELATION TO HUMAN EVOLUTION, 491
are a menace to Europeans, to whom it is carried by
mosquitoes. In New York State the expectation of
life for a negro is very much less than that for a member
of the white race. This is doubtless due in part to
differences in susceptibility to cold and other climatic
factors, as well as to differences in power to resist par-
ticular diseases.
4. It is a singular fact that in the struggle between Bacterial
allied species or races, the existence of a bacterial
disease brought by one of the participants may mean of races
the destruction of the other. This appears to be equally
true among plants, animals, and man. Thus the
chestnut-blight disease, tolerated by the chestnut of
Japan, threatens the extinction of the American tree.
Civilized man has destroyed the native tribes of the
West Indies, Tasmania, and parts of Polynesia mainly
by communicating his diseases. His measles may be
more dangerous than his firearms. The adaptive
process described above may not take place if the
attack is too sudden, or if there is no resistant strain
within the population. The groups which now exist
have so far been able to leave sufficient survivors in the
presence of epidemic disease, but many others have
doubtless become extinct.
(For additional details, see the next chapter.)
CHAPTER SIXTY-ONE
History an
aspect of
biology
The com-
plexity of
mankind
HISTORY FROM A BIOLOGICAL POINT OF VIEW
1. HUMAN history is only a special aspect of "natural
history," dealing with the succession of events having
to do with the species Homo sapiens. It continually
asks, What has man been through the long ages of his
existence ? — and the answer, whatever it may be, is
also in some measure an answer to that still more
interesting question, What may he become ? Modern
biological research teaches us that particles of living
material, having a quite definite composition, pass from
generation to generation unchanged. This does not
mean that the actual atoms of which they consist are
the same, but only that the molecular structure is un-
altered, and consequently that these little machines
may be expected to act in a like manner under like
conditions.
2. We also learn that the human individual is ex-
tremely complex, is made up of materials whkh, how-
ever much they may derive their character from
ancestral germ plasm, are arranged in new ways, so
that it is rarely possible for two individuals to come
into the world with the same inheritance of living stuff.
Just as a newly written poem may consist only of quite
common words, derived unchanged from the language,
so the man may be thought of as containing no kind of
material which has not existed in many other persons.
In spite of this, both the poem and the man are unique,
and their value to us depends far more upon the par-
ticular sort of combination they represent than upon
the elements entering into it. This, at least, if we value
them highly ; but either may be ruined by unfortunate
inclusions, lame words or characters.
492
HISTORY FROM A BIOLOGICAL POINT OF VIEW 493
3. History, then, records the behavior of human Environ-
beings, so constituted, under different environmental {H1emannd
conditions. It has consequently two aspects, the his- nature
torical in the broad sense, and the biographical. In the
first, it seeks to determine the effects of the environment
on mankind in general, or on races of mankind. At the
same time it asks, What is the duty of man ? What is
to be expected of this particular sort of creature in this
world of ours ? Such investigations emphasize the
continuity of the germinal substance, the sameness in
the midst of diversity.
4. On the other hand, the biographical method
emphasizes the peculiarities of the individual. The
common characters are forgotten, and all the emphasis
is laid upon the uniqueness of the heroes or villains who
people the stage. This uniqueness appears to spread
beyond themselves and to color the lives of their fellows,
so that a whole nation partakes of certain characteristics
because it has within it an outstanding personality.
5. It is a common fault of historians to overempha- Thesig-
size the importance of individuals and events, con-
sidered as causes of what follows. Just as we all have events
a vague idea that certain simple propositions were first
formulated in the Bible or by Shakespeare, because we
there find the classical expression of them, so the his-
torian is too liable to see a new birth in a salient event.
On the other hand, he is likely, from no fault of his own,
to be unaware of the time and place of the genuine
mutations in human thought and deed. However the
stars in their courses may have been moving toward the
birth of a new idea, there is a specific moment of time
when that idea emerges into the field of human con-
sciousness ; and that is a genuinely historic event,
possibly tingeing and changing the lives of subsequent
494
ZOOLOGY
generations during the rest of man's existence. Legis-
lative enactments, political disturbances, wars, all the
chief materials of historic research, are secondary to
these psychological phenomena. Through "social in-
heritance," whereby the thoughts and experiences of
one generation are made known to those following, the
thinker becomes the dynamic force in social evolution.
It is because of this fact that progress is possible and
inevitable, and that the future cannot be accurately
predicted from the past. In spite of the continuity
of the germ plasm, the sameness of the molecular
composition of the human stuff, mankind has learned
how to break his bounds and set forth on a journey to
which he sees no end.
6. When did history begin ? In one sense, with the
first germ of life ; but we are concerned with a more
limited point of vi^w. The ancient man of the Stone
Age lived in the caves of France and Spain for many
thousand years, without appreciable progress. The
emergence of new ideas, the discovery of new methods,
additions to his knowledge of the world, were all so few
and rare that he could hardly have had any sense of
progress. At any given time he was probably unaware
of any important change in human affairs, and quite
without any suspicion of the fact that he possessed a
mind capable of dealing with complex systems of
thought and managing miraculous machines. He had
no history, in our sense, — much as the moon, within
the period of human observation, may be said to have
no history. True history begins with events suffi-
ciently important to alter the status of human affairs,
and especially when these follow each other fast enough
to give a sense of progress, to arouse the expectation of
a future different from the past. According to this
HISTORY FROM A BIOLOGICAL POINT OF VIEW 495
interpretation the beginnings of history are coincident
with the awakening of the specific powers of man, and
do not depend upon the existence of records. The wild
men of certain remote regions of the Amazon are still
in the prehistoric period.
7. The fact of social inheritance — that is to say, of Tradition
tradition — complicates in many ways the historian's
problem. He must always be asking, is a certain trend
of events, a certain way of doing things, due primarily
to tradition or to the nature of the human mind ? Thus,
for example, the remarkable Maya monuments in Cen-
tral America, dating from a period long before Colum-
bus, appear to show Asiatic influence. They certainly
possess characters in common with the monuments of
Oriental lands, though in detail quite distinct. Is the
degree of resemblance such as may be traced to the
common mental characteristics of humanity, or must
we explain it by postulating an early discovery of Amer-
ica by Asiatics crossing the Pacific Ocean ? Or again,
certain stories and legends, such as those of Uncle
Remus, appear in various forms on opposite sides- of
the world, among peoples who have apparently not
been in communication. Are they the naive imaginings
of man, in the presence of the universal facts of exist-
ence, or have they their root in a widespread tradition
having a single place of origin ?
8. History being concerned primarily with the phe- intra-
nomena of human progress, it follows that events within
the tribe or nation are more important than struggles factors
between nations. It is within the group that true de-
velopment occurs, and it is rarely that the beginnings
of important advances are spectacular. Wars are de-
structive and retrograde, but the reconstruction periods
following them, or even during their progress, may
496 ZOOLOGY
possess the greatest historical importance. Thus a
description of what went on behind the lines may pos-
sess more value, may mean more in relation to the
future, than one of the heroic acts in battle. From the
point of view of general history there is a rather close
parallel between wars and epidemics, in that both are
destructive, and both necessitate a process of recon-
struction during which new tendencies are likely to
develop. Both, also, may be so severe and so pro-
longed that a sort of historic fatigue sets in, and ade-
quate reactions become impossible. Both, again, may
select for destruction particular groups of individuals in
a mixed population, and thus alter the average quality
of the germ plasm of the nation or nations concerned.
The Black 9- As an example of the effects of an epidemic, we
Death may take the history of the Black Death, the great
plague which devastated Europe in the fourteenth cen-
tury. It will readily be seen that it resembles in some
of its effects that other great European disaster, the
war in our own times. The Black Death or Plague is
an Asiatic disease, which has at different times invaded
Europe. The last epidemic in England of first-class
importance was the Plague of London, shortly after
the middle of the seventeenth century. The Black
Death of the fourteenth century is said to have de-
stroyed half the population in many parts of Europe.
F. A. Gasquet, who has given us a vivid account of it,
thus describes the reaction of the English in the presence
of this great disaster and following it :
"In dealing with this subject it is difficult to bring
home to the mind the vast range of the great calamity,
and duly to appreciate how deep was the break with
then existing conditions. The plague of 1349 simply
shattered them. . . . The tragedy was too grave to
HISTORY FROM A BIOLOGICAL POINT OF VIEW 497
allow of people being carried over it by mere enthu-
siasm. . . . It was essentially a crisis that had to be
met by strenuous effort and unflagging work in every
department of human activity. . . . Many a noble
aspiration which, could it have been realized, and many
a wise conception which, could it have attained its true
development, would have been most fruitful of good to
humanity, was stricken beyond recovery. . . . Time,
however, and the power of effort and work remained to
those that survived. . . . What gives, perhaps, the
predominant interest to the century and a half which
succeeded the overwhelming catastrophe of the Black
Death is the fact of the wonderful social and religious
recovery from a state almost of dissolution."
In the course of this recovery, through periods of re- Social and
bellion and acute distress, the foundations of better ^guitsof
social ideals and conditions were laid, and even the the Plague
language underwent a change. It had been customary
for the educated classes to use Norman-French, which
emphasized their distinctness as a social group. A
movement existed for the substitution of English in the
schools, and Gasquet believes that it succeeded because
so many "ancient pedagogues," of conservative tenden-
cies, were removed by the Plague. Thus was laid the
foundation of modern English as a basis for literature,
and thus were the plays of Shakespeare made possible.
Notwithstanding all these great events and funda-
mental changes due to the Black Death, the ordinary
writers of history have chosen almost to ignore them
and to write of the spectacular deeds of the battlefield,
of Edward III and his war with France, of Crecy and
Calais, and military renown. This, according to them,
was the glory of England ; but such glory passed away,
and the glory which remained was that of the stout
498
ZOOLOGY
Epidemic
Racial sus-
ceptibmty
hearts and keen minds which wrought weal out of the
very elements of woe.
io. It would be quite erroneous to emphasize epi-
demies and military struggles alone, forgetting the
tremendous significance of endemic disease and of
economic forces in society. These slower processes are
hard to grasp, because they are only imperfectly or not
at all known to those who are affected by them;' the
"original sources," the contemporary chronicles, are
silent concerning them. Thus there seems to be reason
for thinking that the Golden Age of Greece passed
away, never to return, not so much on account of wars
and invasions, as because of the selective action of
malaria. Conquests had brought to the Grecian shores
captives of dusky hue, contrasting with the fair folk
of aristocratic Greece. The malaria organism, existing
in the blood of the conquered, caused them little
trouble ; they had acquired "tolerance" from long ages
of selection. Transmitted to the northerners, the
disease killed or debilitated, and gradually the darker
races, variously intermarrying with the lighter, came
to dominate the civilization. The chances for success in
life were in inverse proportion to the amount of north-
ern blood, when malaria became universal. In similar
ways we may explain how the northmen, the Normans,
firmly established themselves in northern France, but
have left no impression on the population of Sicily. All
these matters are of course largely speculative, viewed
after so great a lapse of time ; but we can at least show
that similar effects are being produced today, in Africa
and Alaska and in the islands of the Pacific.
In the struggle for existence between races, the
existence of a mild disease in one is often the undoing
of the other. The disease is mild to those races which
HISTORY FROM A BIOLOGICAL POINT OF VIEW 499
have long experienced it, but severe to those who first
come in contact with it. Among ourselves, for ex-
ample, all those strains or groups which could not en-
dure measles have long ago perished, leaving those to
whom it is a light matter. To the Indians of Alaska it
is a different case ; they have undergone no such selec-
tive process. To the negroes of West Africa the
pernicious forms of malaria, which kill so many Euro-
peans, are not pernicious at all. The negro children
run about with the parasites in their blood, and are a
menace to white people, to whom these parasites are
conveyed by mosquitoes.
II. Great changes in the character of a population Results of
will result from differences in the birth or mortality
rates, and yet these may be so gradual as to escape
observation. Thus if one part of a population produces
two children for every pair of parents, and another three,
and each starts with 1000 members, the first group at
the seventh generation will have 1000 descendants, the
second, 11,391. This assumes that the children grow
up and become parents ; it takes no account of those
who fail to do this, so that the total number of children
born is no exact criterion of the vitality of a race. It is
easy to see from considerations of this sort that, quite
apart from conquests and migrations, changes are going
on within the nations themselves. We may pride our-
selves on belonging to an ancient people, without realiz-
ing that perhaps little is left of that people in those who
now bear the name. The biologist will therefore not
conclude too hastily that differences in the course of
history, in the reactions to environment, are wholly due
to external circumstances or the effects of education;
they may be due in part to actual changes in the heredi-
tary make-up of the group concerned.
CHAPTER SIXTY-TWO
EUGENICS
Objections i. THE word eugenics, proposed by Francis Gallon
of England, is used to designate the science and art of
human breeding, whereby it is supposed that the race
may be improved, or prevented from deteriorating.
This idea arouses strong prejudice in the minds of
many people, because they associate it with animal
breeding, in which practical ends are sought without
reference to the desires of the animals themselves. Such
people also recall that animal breeders follow fashions,
and produce or conserve the most grotesque creatures,
such as the pug dog or the poodle. They do not wish
to see human equivalents of the pug dog or the poodle,
and they fully understand that many of the most
valuable human qualities are intangible, and in-
capable of being accurately measured or tested. The
excellent human being is such because in him are united
many qualities, in a happy combination ; and to at-
tempt to create such a one by breeding seems as gro-
tesque as an effort to write poetry by- an application
of the rules of grammar.
Eminence of 2. It may further be objected by the student of
invalids history and biography that many of the most valuable
men, from a social standpoint, have been invalids, who
could never have survived under Spartan rules. Thus,
Darwin was a lifelong invalid, Keats was a consump-
tive, Milton was blind, and so forth. It is a peculiarity
of human society, that its success and efficiency depend
largely on the existence of individuals who in many cases
are personally ill-fitted for the struggle for existence.
3. Even the student of genetics may point out that
human beings, especially in civilized countries, are
500
EUGENICS
5OI
strongly heterozygous (cross-bred), so that it is very Heterozy-
difficult to say, from the life record of an individual, J£ ^a*atur
what kinds of descendants he is likely to have. Since
he will be united with another of diverse character,
the matter becomes still more complicated. Numerous
instances will occur to most people, in which the
children, or some of them, differed greatly from ex-
pectation based on the appearance of the parents.
4. Nevertheless, although the word eugenics is rela- Ancient
tively new, the thing itself is no more new than appen- eugemcs
dicitis. Every one has heard of Spartan methods,
crude eugenic efforts dating from remote times. The
elimination of the weak has in earlier times and among
savage peoples been taken as a matter of course ;
"but," says Darwin, "we civilized men, on the other
hand, do our utmost to check the process of elimina-
tion ; we build asylums for the imbecile, the maimed,
and the sick ; we institute poor-laws ; and our medical
men exert their utmost skill to save the life of every one
to the last moment." If it is a fact that in such ways
undesirable characteristics are perpetuated, and the
number of incapable persons is increased, the matter
is serious enough. While it may be true that a few
individuals of great merit have poor constitutions, it
is no less true that multitudes have the inadequate
inheritance without the merit.
5. Although the laws of inheritance have been little Blue blood
understood in the past, we are all familiar with the
idea that some persons belong to especially "good
families," and that their descent from able ancestors
is a matter for boasting. Heraldry would have little
meaning apart from this. Considerations of this sort
have always had great weight in reference to marriage,
and the desire to unite persons of "blue blood" may
502
ZOOLOGY
Ideals of
love and
marriage
Classifica-
tion of
eugenic
measures
be called eugenic. Many romantic stories are base
on the supposition that the prince, stolen perhaps as an
infant, and raised in a hovel, will still manifest the
princely qualities which his heredity has given him.
Thus the intuition of a biological fact, forcing itself
on the human mind without the aid of formal science,
has become the basis of aristocratic claims. Lacking
the check of critical investigation, it has been exag-
gerated to the point of absurdity. Yet there is a
background of truth.
6. Those who are most prejudiced against eugenics
would nevertheless consider it exceedingly reprehen-
sible to marry without any regard to the ability of
the parents to take care of their offspring. We should,
as a matter of course, consider health and income.
Even sordid financial considerations, in so far as they
carry with them ability to make a living, may serve
eugenic ends. Most of us would probably even admit
that the process of "falling in love" is not wholly
independent of considerations of the type mentioned.
Indeed, natural selection and sexual selection combined
must have brought it about that the qualities we admire
or love are in general also those valuable to the race.
Were the reverse true, the species would have failed
in the struggle for existence.
7. We see, then, that eugenics is a new name for a
very old idea, and that in addition to deliberate and
planned eugenic practices, there have been innumerable
other ones attaining the same ends, usually more or
less unconsciously. These latter supplement and grade
into the operations of natural selection itself. Roughly,
we may classify the agencies making toward the im-
provement of the genetic qualities of the human race
as follows :
EUGENICS 503
A. "Natural," i.e., independent of human volition.
B. Due to human volition, but not deliberately
eugenic.
C. Purposeful eugenic efforts.
It becomes, therefore, not a question whether in-
fluences modifying the race shall exist, but whether,
since they do and will exist, we desire to control them
in any way. It is difficult to escape our responsibility
in this matter. We have to a considerable extent the
choice of good and evil, and must perforce choose.
8. It is not possible, and were it possible, not de- Thein-
sirable, to extend our scientific operations over the defects
whole field, bringing all the influences affecting the
race under the group C. It is a matter for careful
consideration, how much we wish deliberately to
control. In future ages the increased knowledge and
intelligence of man may justify him in attempting
what would now be wholly unwise. Nevertheless,
enough evidence has accumulated in the last ten or
twenty years to prove that certain physical and mental
defects are inherited, and are connected with particular
determiners in the germ plasm. Thus, two persons
having a certain type of feeble-mindedness will cer-
tainly have only feeble-minded or mentally defective
children. It does not appear very radical or extreme
to postulate that no one has the right deliberately to
bring feeble-minded offspring into the world. To be
sure, those doing this are not capable of judging of
their actions ; but society is capable, and society may
well put forth a restraining hand. Proper institu-
tional care of the mentally defective thus becomes not
merely an act of kindness and justice to these un-
fortunates, but also a most important protection to
society itself.
504
ZOOLOGY
Recessive
characters
Scientific
heraldry
9. It has been suggested that whereas many of the
inherited human defects are recessive, it does not matter
if one possessing them marries a normal person. The
children will be cross-bred, to be sure, but they will
appear normal. They in turn will probably marry
normal individuals, and the pernicious determiners will
never lead to any recurrence of the objectionable
characters. With regard to this it must be said, in the
first place, that such cross-bred individuals may not
be wholly normal. In some cases the heterozygous
individuals may be decidedly different from homozy-
gous (pure-bred) dominants, and experienced breeders
say that among plants and animals they can often pick
them out by critical inspection. More serious, how-
ever, is the fact that the recessive qualities do not dis-
appear from the stream of inheritance ; their deter-
miners go from generation to generation, ready to
produce effects as soon as a chance combination brings
them together. Thus they are a trap laid for posterity,
and after perhaps one or several hundred years two
persons may come together, each with an unknown
determiner for feeble-mindedness. One fourth of the
offspring will then, on the average, be feeble-minded,
and people will wonder at the inscrutable ways of
Providence.
10. To what extent may group C include measures
taken to increase good qualities ? This is a far more
difficult problem, since the complexity of human in-
heritance is so great. Yet it may be desirable and
prudent to pay more attention to the family record,
as well as to the personal attainments of individuals.
Strong objections would be raised to the publication
of a mass of unfavorable data, but we can imagine a
new sort of heraldry, by which families would be
EUGENICS 505
allowed to indicate in some manner their total achieve-
ment. Judgments might be difficult, yet not at all
impossible. Galton, in his work on Hereditary Genius,
has clearly demonstrated the great worth of certain
families, and the presumptive value of any individual
belonging to them. No one would be obliged to favor
the groups thus indicated, or pay any attention to
family merit; yet it cannot be doubted that if the
facts were known in each case they would carry weight.
Naturally, the whole procedure would imply the keep-
ing of accurate records, and the government would
probably be justified in compiling a "Who's Who"
for the entire population.
ii. Speaking broadly, we may say that it should be Environ-
the aim of society to create an environment favorable
to individuals of high social efficiency. For example,
those entering the professions should not have to wait
as long as they do at present before possessing the
material means to justify marriage. We see today
numerous able young men with small incomes, and
fewer old ones with ample resources. It cannot be
said, from the standpoint of eugenics, that the wealth
of the country is well distributed. It is useless to
criticize the small size of the families of college graduates
as long as economic conditions are unfavorable. Hard
facts will outweigh theoretical or sentimental considera-
tions. - It is of course true that the standard of living
of the educated groups is high, but it would appear
a doubtful advantage to lower it, since competition
would tend to lower wages correspondingly. It is
also necessary to maintain a high standard to give the
socially valuable all the advantages of education and
other forms of "nurture," without which their powers
will be diminished.
506
ZOOLOGY
Value of
prophets
Sexual
selection
Eugenics
and disease
12. It must be remembered that we are concerned
not so much with immediate benefits (which must be
attained by other than eugenic means), as with the
welfare of the race in the long run and the course of
time. Hence we should be alive to the value of in-
dividuals whose work takes a long time to bear fruit,
such as reformers of various kinds and many scientific
investigators. William James well said that Saint
Paul was poorly adapted to the environment of his
day, since he was executed ; but he is magnificently
adapted to the larger environment of history.
We can make the more subtle and precious human
qualities count plus in the struggle for existence only
by ourselves appreciating them. Hence the effort to
cultivate good morals and good taste is indirectly
eugenic, and may become a powerful factor for racial
betterment.
13. Sexual selection must be considered an important
eugenic force. It has been objected that sexual selec-
tion is of small avail in man, because there is nothing
to prevent the marriage of all grades of inferior people.
This is not a valid objection, since the union of good
qualities conserves them, and in this way the race is
provided with a larger number of highly efficient
persons, who become very valuable even to the less
efficient, when engaged in socialized work. Hence the
economic independence of women, and coeducational
institutions for higher learning, both serve .eugenic
ends.
14. We may now return to Darwin's criticism of the
preservation of the unfit in civilized countries. We
have seen that the propagation of those possessing
serious inherited defects should be and can be largely
prevented. The warfare against infectious disease,
EUGENICS . 507
however, is eugenic in so far as it substitutes profitable
for unprofitable selection. Smallpox, for example, is
strongly selective, but the individuals preserved have
no other common merit than that of being able to
resist smallpox, which is not in itself a valuable social
faculty. The ancient saying, "Those whom the gods
love, die young," bears testimony to the lack of corre-
lation between the ability to resist disease and any
other merit. In so far as useless forms of selection are
eliminated, useful ones gain added significance.
The idea of sexual selection in man and the economic
emancipation of women give new meaning to Coventry
Patmore's beautiful lines :
Ah, wasteful woman, she who may
On her sweet self set her own price,
Knowing he cannot choose but pay : —
How she hath cheapened paradise !
How given for naught the priceless gift,
How spoiled the bread and spilled the wine,
\ Which, spent with due respective thrift,
Had made brutes men, and men divine!
CHAPTER SIXTY-THREE
The reputa-
tion of
Agassiz
Early years
in Switzer-
land
LOUIS AGASSIZ
1. PERHAPS the most picturesque figure in the
history of biology is that of Louis Agassiz. Equally
famous in Europe and America, combining a re-
markable intellect with much of the nai've simplicity
of a child, he appealed to the public in a way which
has rarely been approached in the annals of science.
While he was professor at Harvard University, his
popularity led to a certain amount of natural jealousy.
Why is it, people said, -that every one talks of Agassiz ?
Is his work so tremendously important that everything
he does must be immediately reported and discussed,
while the profound researches of other men go un-
noticed ? It was not Agassiz' s fault. He was one
of the greatest of naturalists, but whatever he might
have been, people would have been fascinated by his
presence, his tremendous enthusiasm. Few have such
gifts, but those who have them may do great things
for science and education.
2. Louis Agassiz was born at Motier, in Switzer-
land, in 1807. His father was the pastor of the village.
Louis, like other Swiss boys, was keenly interested in
the life of the meadows and lakes, forests and moun-
tains. He early accumulated collections of specimens,
and also had many pets. At the age of ten he was sent
away to a school at Bienne. Here he remained for
four years, and toward the end of that period wrote
out a statement of his future plans, — rather remark-
able ones for a fourteen-year-old boy! "I wish," he
wrote, "to advance in the sciences.
I should like
to pass four years at a University in Germany, and
finally finish my studies at Paris, where I could .stay
508
LOUIS AGASSI Z 509
about five years. Then, at the age of twenty-five, I
could begin to write." The parents had intended
FIG. 208. Louis Agassis.
Louis for a commercial life, but the boy's hopes and
ambitions led in other directions, and medicine was
substituted. After two years at the College of Lau-
sanne, he went to the Medical School at Zurich, and
in 1826, at the age of nineteen, to the University of
Heidelberg in Germany.
3. The four years of university life in Germany were University
divided between Heidelberg and Munich. The new Germany
university at Munich had opened under brilliant
510 ZOOLOGY
auspices, with a remarkable faculty, and was attracting
many students. So, after a year at Heidelberg,
Agassiz decided to migrate, and with him went his
greatest friend among the students, Alexander Braun.
Many records exist, showing the intensity of Agassiz's
life in the university. With his friends Braun and
Schimper he seemed able to attack every difficult
problem. The three were so closely associated that
the students called them the "Clover leaf." After
the day's work these men, with a few others, would
meet and deliver lectures. The association thus formed
came to be known as the " Little Academy," and
eminent men would often look in upon it, with ex-
pressions of interest and sympathy. The young
lecturers deemed all this valuable experience, "since,"
they said, "we all desire nothing so much as sooner or
later to become professors in very truth, after having
played at professor in the university." Their poverty
was no check to their activities, and their life was
picturesquely bohemian. Braun, in his letters home,
gave some graphic descriptions : "A live gudgeon with
beautiful stripes is wriggling in Agassiz's washbowl, and
he has adorned his table with monkeys. We stay
together in his room or mine by turns, so as not to
need heat in two rooms, and not to burn twice as
much for light. . . . Under Agassiz's new style of
housekeeping, the coffee is made in a machine
which is devoted during the day to the soaking of
all sorts of creatures for skeletons, and in the even-
ing again to the brewing of our tea." More and
more, zoology became the passion of Agassiz's life,
and the studies in medicine, ostensibly the occasion
of his presence at the university, were increasingly
neglected. »
LOUIS AGASSIZ 511
4. Several years earlier the King of Bavaria had The fishes
sent an expedition to Brazil, to collect specimens of
natural history. The. results of this journey were in
course of publication in a number of sumptuous volumes,
but in 1826 the author of the zoological series died.
This left the fishes undescribed, and when the editor
looked around for a suitable man to deal with this sub-
ject, he decided upon the young student Agassiz.
This was an extraordinary compliment, and although
it meant still further encroachments upon the time
devoted to medical studies, the task was gladly ac-
cepted. In due time the book appeared, and Agassiz,
justly proud, writes with enthusiasm to his sister
Cecile : "Will it not seem strange when the largest and
finest book in papa's library is one written by his
Louis?"
5. Having duly graduated at Munich, Agassiz re- Fossil fishes
turned to Switzerland, where he made a certain pre-
tense of setting up a medical practice. He was, how-
ever, now filled with ideas of writing great works on
fishes, and particularly on fossil fishes, a subject then
greatly neglected. So we find • him going to Paris,
approximately carrying out the plans he made when a
boy. Here he sought the acquaintance of Cuvier, an cuvierand
aristocratic genius, the first zoologist of his time and Humboldt
one of the greatest leaders of French science. Cuvier
received him politely, and soon began to take a strong
personal interest in his work. After a time, when
thoroughly satisfied of the young man's ability, Cuvier
produced a portfolio of notes and drawings of fossil
fishes. This he placed in Agassiz's hands, saying that
he had himself intended to prepare just such a work as
Agassiz had in view, but he now saw that his young
friend was the proper man to do it. Would he, there-
512 ZOOLOGY
fore, accept these accumulated materials to use in any
manner he thought best ? Agassiz, communicating the
news to his grandfather, writes: "You can imagine
what new ardor this has given me for my work ; . . . I
work regularly at least fifteen hours a day, sometimes
even an hour or two more ; but I hope to reach my
goal in good time." Even after this, Agassiz was
almost compelled to abandon his labors and return
prematurely to Switzerland, on account of lack of
means. Fortunately another great scientific man,
Alexander von Humboldt, learned of his distress and
generously supplied him with a considerable sum of
money.
6. Agassiz went to Neuchatel, Switzerland, in 1832,
anj remamej untji 184$. During this time he taught
and wrote, and although he had great difficulty in
making a living, this was the period of his most brilliant
and important scientific work. In 1833 he married
Cecile Braun, the sister of his greatest friend. From
1833 to 1844 the great work on Fossil Fishes (Recherches
sur les Poissons jos sites) appeared in parts, with hun-
dreds of plates. Agassiz had developed a classifica-
tion which depended largely on the character of the
scales, but it subsequently appeared that some of his
groups were unnatural, and his methods were aban-
doned. In quite recent years the scale work has been
taken up again, and the result has been to confirm
fully the value of scales for classification, though the
interpretations of Agassiz prove in some cases unsound.
Much work was done on fresh-water fishes also, on
fossil echinoderms, and other subjects, the titles of
books and papers issued during the Neuchatel period
numbering about 1 50. The most remarkable new work,
however, was on a subject wholly unconnected with
LOUIS AGASSIZ 513
zoology, though it afterwards came to have a very
important bearing on all theories of the distribution of
animals and plants. The Swiss naturalist Charpentier
had observed that many boulders scattered over the
meadows and valleys of Switzerland consisted of rock
which did not occur in place in the vicinity. The
herders called them roches moutonnees, or "sheep rocks,"
because they resembled resting sheep and sometimes
deceived those in search of their lost animals. As
early as 1815 a mountaineer named Perraudin had
called attention to these rocks, and had suggested that
they had been brought by glaciers which had since
melted away. This view was supported by the en-
gineer Venetz, and finally was brought before the scien-
tific world by Charpentier, who presented convincing
evidence.
Agassiz, then, did not originate this idea; but he The glacial
saw that if Charpentier was right, much more followed eory
than that able man imagined. If Switzerland had once
been buried in ice to the extent claimed, how could
the climate producing such an effect be restricted to
this small area ? Must not all northern Europe, and
even North America, show similar phenomena ? Thus
was developed the great glacial theory, which is now a
commonplace of geological science. In many countries
"erratic boulders," as they are called, were found, and
also scratches on the rock left by the grinding masses of
ice. Naturally such an astonishing conception was
not accepted unchallenged. People said, Why does
not Agassiz stick to his fishes, which he understands,
instead of setting forth such crazy notions, belonging
to a field in which he is no expert ? Gradually, how-
ever, the facts came to notice, and geologists were
compelled to accept the theory practically as Agassiz
ZOOLOGY
le teacher
American
ologists
presented it. Today we recognize several periods of
glaciation, with warmer intervals ; and any one travel-
ing across America in a train can recognize the gla-
ciated areas by their topography.
7. As time passed, Agassiz's financial condition got
worse and worse, until it was really desperate. Some-
thing had to be done. At this juncture the king of
Prussia, through Humboldt, offered Agassiz some three
thousand dollars to be spent in scientific travel ; and
the Lowell Institute at Boston asked him to deliver a
course of lectures. Consequently, in October, 1846,
Agassiz arrived in Boston, and gave his first series of
lectures, on "The Plan of Creation." He had little
experience in speaking English, but he could illustrate
his meaning by drawings in chalk ; and from the first
his audiences were not merely sympathetic, they were
charmed. No one in this country had ever been able
to make natural history so interesting. Agassiz, on
his part, was amazed and delighted at the warmth of
his welcome and the amount of money he was able to
make. At last the burden of debt was lifted, and he
was square with the world. He meant to return, of
course, but he had not been long in America when he
learned of his wife's death, and gradually the home ties
seemed to weaken, as those connecting with the New
World strengthened. In 1848 he was offered a pro-
fessorship at Harvard University, and in view of the
then disturbed state of Europe, he was glad to accept.
The following year he married an American lady,
Elizabeth Cabot Cary.
8. From 1848 to the time of his death in December,
1873, Agassiz devoted himself to the development of
American zoology. In this quarter of a century he
did much work of his own and planned much more,
LOUIS AGASSIZ 515
but his researches were not equal to those carried
out during the brilliant thirteen years in Switzerland.
There were perhaps too many distractions, and whereas
he had formerly struggled bravely against difficulties,
he now seemed to suffer from a surplus of opportunities.
In America, however, he is remembered chiefly as the
great teacher, — the one who, whatever he did himself,
stimulated others as no one else could do. No doubt
all the ablest men in the country with zoological
leanings flocked to him ; he had before him the best
material America could furnish ; but all those who
labored successfully under his guidance united in their
tribute to his power as a teacher. Others there were
with whom he could do nothing ; he made no conces-
sions to laziness or want of zeal, but expected to find
industry and enthusiasm resembling his own.
9. In 1857 Agassiz was offered a professorship in Longfellow
Paris, a position which earlier in his life would have Agassiz
seemed to represent the very pinnacle of his aims.
Amid much enthusiasm in America, he declined, though
the offer was renewed and pressed upon him. It was
in this year, on the occasion of his fiftieth birthday,
that Longfellow wrote the charming verses :
It was fifty years ago,
In the pleasant month of May
In the beautiful Pays de Vaud,
A child in its cradle lay,
And Nature, the old nurse, took
The child upon her knee,
Saying, "Here is a story book
Thy Father has written for thee —
"Come wander with me," she said,
"Into regions yet untrod;
And read what is still unread
In the manuscripts of God."
Si6
ZOOLOGY
And he wandered away and away
With Nature, the dear old nurse,
Who sang to him night and day
The rhymes of the Universe.
And whenever the way seemed long,
Or his heart began to fail,
She would sing a more wonderful song
Or tell a more marvelous tale.
Evolution
The Agassiz
Museum
At Cambridge Agassiz's warmest friends were the
great New England writers, Longfellow, Lowell,
Holmes, Emerson, and the rest. With the purely
scientific men he was somewhat less in accord, partly
on account of differences in temperament, and partly
because they were becoming disciples of Darwin, whose
theory of evolution he could never bring himself to
accept. His students who afterwards became eminent
naturalists, men such as Jordan, Scudder, Dall, Shaler,
Packard, Hyatt, Verrill, Morse, Garman, and the rest,
all accepted evolution ; but they were of a later genera-
tion. Agassiz, in 1859, could not make over his bio-
logical philosophy.
10. During the last fourteen years of Agassiz's
life, his interests centered around his museum, the
corner stone of which was laid in 1859. Officially it
is the Museum of Comparative Zoology of Harvard
University, but every one calls it the Agassiz Museum.
It is not one of the largest museums of the world,
such as the British Museum, but it is devoted to the
exhibition, in compact form, of the whole animal
kingdom. It is designed for teaching and research,
not for a great national storehouse. In its strength
and its limitations it is a typical university museum,
with scarcely an equal anywhere. Agassiz obtained
for it not only private legacies and gifts, but actually
LOUIS AGASSI Z 517
induced the legislature of Massachusetts to grant a
large measure of support. Legally, it might belong to
the Harvard Corporation, but it was in all essentials
a public insitution, free to those who cared to make use
of it.
11. In 1848 Agassiz visited the shores of Lake Journeyto
Superior, and in 1850 the Florida reefs. In 1865-1866
he went with his wife and a company of young natural-
ists to Brazil, to explore the waters of the Amazon and
other rivers, and meet in life the fishes he had de-
scribed so long ago at Munich. One of his assistants
on this expedition was William James, afterwards
famous as a psychologist. Thanks largely to the aid
of Dom Pedro, the Emperor of Brazil, the expedition
was extremely successful, and the collection of fishes
made was enormous. Agassiz thought he had about
1800 new fishes from the basin of the Amazon, but he
never found the time and strength to describe them.
They are still preserved at the Museum of Compara-
tive Zoology, and have been studied by many ichthy-
ologists.
In 1871-1872 Agassiz went in the Coast Survey Hassier
vessel Hassier to California by way of Cape Horn. exped
It was a long voyage, and his health had been poor,
but he was delighted with the opportunity to see so
much marine life. He thought that in the deep sea
he would find a fauna resembling that of early geo-
logical epochs. In .spite of his enthusiasm, however,
the state of his health could not be forgotten, and when
they finally reached San Francisco, Agassiz was brought
home without attempting to see the wonders of Cali-
fornia or the Rocky Mountains.
12. It seemed, indeed, that he was a broken man,
but once more his splendid energy declared itself. He
518 ZOOLOGY
Summer had long wished to carry on his teaching by the sea,
Penikese where marine life could be studied in its natural envi-
ronment. A plan was formed for a summer school
of natural history, a biological station. Today the
idea is commonplace, but then it was a wonderful new
experiment. The island of Penikese, off the coast of
Massachusetts, was offered for his use, together with
a considerable sum of money. On July 8, 1873,
surrounded by a carefully chosen group of students,
men and women, Agassiz opened the Penikese school.
Mrs. Agassiz relates that "as he looked upon his
pupils gathered there to study nature with him, by an
impulse as natural as it was unpremeditated, he
called upon them to join in silently asking God's
blessing on their work together." Whittier has im-
mortalized this moment in a poem :
On the isle of Penikese,
Ringed about by sapphire seas,
Fanned by breezes salt and cool,
Stood the Master with his school.
Said the Master to the youth :
"We have come in search of truth,
Trying with uncertain key
Door by door of mystery ;
*****
We are groping here to find
What the hieroglyphics mean
Of the Unseen in the seen,
What ,the Thought which underlies
Nature's masking and disguise,
What it is that hides beneath
Blight and bloom and birth and death.
By past efforts unavailing,
Doubt and error, loss and failing,
Of our weakness made aware,
On the threshold of our task
Let us light and guidance ask,
Let us pause in silent prayer!"
LOUIS AGASSIZ 519
Then the Master in his place
Bowed his head a little space,
And the leaves by soft airs stirred,
Lapse of wave, and cry of bird
Left the solemn hush unbroken
Of that wordless prayer unspoken,
While its wish, on earth unsaid,
Rose to heaven interpreted.
Returning from Penikese, Agassiz looked forward Last days
to renewed activities of all sorts, but his time was
drawing to a close. As late as the 2d of December he
delivered one of his characteristic lectures, but from
that time he rapidly failed, and died on December
14, 1873. He was buried in Mount Auburn Cemetery,
and his tombstone is a boulder from the glacier of the
Aar, not far from the place where so long ago he studied
the movements of the ice.
The island of Penikese is now a leper settlement;
but at Woods Hole, on the coast of the mainland, is
a large and important biological station and summer
school, where Agassiz' s plans and hopes are realized
in the fullest manner. Not only this, but on many
other coasts such schools have been founded, and
throughout the world the impetus given to the study of
natural history by Agassiz is still a living force
References
GOULD, ALICE BACHE. Louis Agassiz. (Beacon Biographies.)
AGASSIZ, ELIZABETH GARY. Louis Agassiz, His Life and Correspondence.
MARCOU, JULES. Life, Letters, and Works of Louis Agassiz.
CHAPTER SIXTY-FOUR
SPENCER FULLERTON BAIRD AND THE UNITED STATES
NATIONAL MUSEUM
Early life I. SPENCER FULLERTON BAIRD Was bom at Reading,
Pennsylvania, in 1823. His ancestry was mixed, -
English, Scotch, and German. He early lost his father,
and his mother, with her seven children, moved to
Carlisle, Pennsylvania. Spencer Baird and his brother,
William, began in their early "teens" to collect birds.
As in the case of Darwin and many other famous
naturalists, the love of collecting was the founda-
tion of a scientific career. With the specimens, data
or facts were also collected, and all had to be set in
order. This gathering of materials and arranging them
is the method of science ; further developments merely
result from the growth of experience and opportunity,
inborn traits Baird's diary at the age of sixteen shows some of the
qualities which distinguished him through life. On
May 25, 1839, he writes :
About one A.M. gust came up ; light wind — some thunder — rained
violently for one quarter hour. Very warm all day. About two P.M. went
out to creek with gun. Shot some small birds, principally flycatchers.
Home at seven. Skinned and opened birds until ten.
These are unimportant details, but they show a love
of precision, a quality fundamental for good scientific
work. In later years this attribute had an important
bearing on the development of American ornithology.
Dr. D. S. Jordan says of Baird :
He taught us to say, not that the birds from such and such a region show
such and such peculiarities, but that "I have the following specimens, which
indicate the presence of certain peculiarities in the birds of certain regions.
The first was taken on such and such a day of such a month, at such a place,
by such a person, and is numbered so and so on the National Museum
records." Thus it was always possible to distinguish between the things
Baird knew and those he surmised, and to refer to the very specimens on
which he based his opinion.
. 520
SPENCER FULLERTON BAIRD 521
2. It was not long before Baird made a genuine dis- Audubon
covery, of a bird entirely new to science. We find him andBaird
After a woodcut in " Science "
FIG. 209. Spencer Fullerton Baird, from a photograph taken about 1865.
timidly writing about it to the great naturalist Audu-
bon : "You see, sir, that I have taken (after much
hesitation) the liberty of writing to you. I am but a
boy and very inexperienced, as you no doubt will
observe from my description of the flycatcher." To
this letter Audubon replied :
On my return home from Charleston, South Carolina, yesterday, I found
your kind favor of the 4th instant, in which you have the goodness to inform
522 ZOOLOGY
me that you have discovered a new species of flycatcher, and which, if the
bird corresponds to your description, is, indeed, likely to prove itself hitherto
undescribed; for, although you speak of yourself as being a youth, your
style and the descriptions you have sent me prove that an old head may from
time to time be found on young shoulders !
The bird was in due time described and named by the
brothers Baird, and is everywhere recognized today as
a valid and distinct species. This was only the first of
a series of such discoveries.
Medical 3. Baird graduated from Dickinson College, at Car-
lisle, and it became necessary for him to consider a
career. He wished to be a naturalist, but that occupa-
tion was hardly likely, it then seemed, to lead to fame
or fortune. After much discussion in the family, in
which young Baird found a strong supporter in his
grandmother, it was decided to send him to a medical
school in New York. There he would continue his
scientific studies, and the profession of medicine would
suitably combine biology with breadwinning. As with
Baird, so also with Agassiz, Darwin, Huxley, and others :
medicine was sooner or later abandoned for pure science,
but the knowledge gained in the medical school was by
no means wasted. On going to New York, Baird soon
made the personal acquaintance of Audubon, and be-
came closely associated with him. He also sought
out all the other notable zoologists of that part of
the country and of Philadelphia. During the holi-
days he continued his field work; in 1843 his diary
states that he had walked about 1400 miles during the
year.
Professor 4. On his return to Carlisle, Baird did not take up
College^ l tne practice of medicine ; indeed, he had not even taken
his medical degree. Instead, he was appointed profes-
sor of natural history in Dickinson College, when only
SPENCER FULLERTON BAIRD 523
22 years of age. As a teacher he was indefatigable and
resourceful. He had nothing resembling the luxurious
laboratories of today, and it was often necessary for
him to manufacture his own apparatus. Whenever
he could, he took his classes for long rambles, — botaniz-
ing, geologizing, and collecting the birds, mammals,
fishes, and reptiles of the neighborhood. However,
this professional period was short, lasting hardly five
years, new opportunities and duties calling Baird to
Washington.
5. The Smithsonian Institution, in Washington, had The Smith-
been founded for the diffusion of knowledge. It took
its name from that of Smithson, an Englishman, who
had left a sum of money to the United States Govern-
ment for the establishment of such an institution.
Professor Henry, an eminent physicist, was in charge.
The funds were limited, and there was much discussion
as to how they should be spent. The terms of the
Smithson bequest were vague enough to allow much
latitude of choice, and advice was offered from all
quarters. It was quite plain to Henry that he could
not do all the things proposed, that he would dissipate
his funds and accomplish nothing of value. He there-
fore tried to restrict his activities as much as possible,
and especially sought to avoid duplicating what was
being done elsewhere. He did not wish to establish a
museum, knowing well the enormous cost, but he found
himself the custodian of certain collections belonging
to the government, for which no other place was avail-
able. He therefore asked for an assistant, to take care
of these materials and otherwise aid in the work of the
Smithsonian. When his request was granted, he at
once selected Baird, who entered upon his duties with-
out delay.
524 ZOOLOGY
Founding 6. Henry dreaded the growth of a great museum,
Museum because he knew that the available money was quite
inadequate to support it properly. Baird went to
Washington full of the idea of building up a museum,
ardently wishing to see a National Museum which
should eventually rank with those in London, Berlin,
and Paris. There was here a conflict of purpose, which
might easily have led to difficulties, but the relationship
between the two men was always ideal, without a cloud.
Baird was one of those tireless, ingenious, persuasive
men who always get what they wish, and make people
glad to give it. Thinking always of his cause, never
asking anything for himself, he captivated congressmen
and others by his sincerity and honesty. Financial
support was granted, and when Henry saw that the
Museum was to be taken care of by the nation, and
would not have to depend on the slender resources of
the Smithsonian, he was readily won over to Baird's
point of view. The efforts made by Baird to increase
the collections were innumerable. Government ex-
peditions were always expected to return with valuable
materials, but he also sought and obtained the aid of
private persons. He would correspond with any and
all who could possibly help, doing all kinds of personal
services for them in return for their contributions.
There was a very able naturalist, Robert Kennicott,
who had a plan to explore the little-known country*
about Hudson Bay. Baird sat down and wrote to
numerous naturalists in these terms: "We are sending
Kennicott to Hudson Bay, I am myself subscribing
$50, and we expect great results. Will not you simi-
larly subscribe, and take your share of what is ob-
tained?" In this way about $500 was collected, and
Kennicott set forth. The results were excellent, and
SPENCER FULLERTO N BAIRD
52S
Photograph by Smithsonian Institution
FIG. 210. The Smithsonian Institution.
Photograph by Smithsonian Institution
FIG. 211. The new building of the United States National Museum. j
today one may find references to them scattered through
the literature of American zoology. About the same
time there appeared another naturalist, John Xantus,
526
ZOOLOGY
Encourage-
ment to
young
naturalists
Baird and
Mason
who wished to visit the Peninsula of Lower California,
a region even less known to zoologists than that of
Hudson Bay. Baird knew that he could not very well
raise a second $500 subscription, and so he hunted
around for another way. He found that the United
States Coast Survey had planned to send a man to that
region to investigate the tides, for the safety of the
merchant vessels which passed up the Pacific Coast
after doubling Cape Horn. Why not send Xantus ?
So it was arranged, and today the name of Xantus is
inseparably associated with Lower Californian zoology.
7. Devoted as he was to the Museum, Baird never
lost sight of the fact that it was not an end in itself ; he
and it existed to serve the American people. So we
find him aiding and encouraging every budding natu-
ralist, every boy who might show the slightest interest
in science. Letters on all sorts of topics poured in upon
him and were always courteously answered, the infor-
mation desired being given whenever possible. Some
who afterwards became famous were thus stimulated
by Baird, when young and unknown. One evening a
week his house was thrown open to scientists, young and
old, and those who gathered about him became his
devoted friends, ready to serve him in return for the
kindness he had shown. In the Museum, as it came to
have a considerable staff of workers, Baird daily made
the rounds of the rooms, giving sympathy and en-
couragement to all.
8. As an example of Baird's attitude toward young
men, we may cite a story told by Dr. O. T. Mason.
Long years ago, when Mason was a youth, he heard that
the Smithsonian had received some Semitic inscriptions
which had lain without being unpacked for some time,
nobody taking much interest in them. Mr. Mason
SPENCER FULLERTON BAIRD 527
hastened to the Museum, for he had already become
much interested in Semitic ethnology and expected to
make it the chief study of his life. Professor Baird
received him most cordially, and placing his hand on
his shoulder said, "These things have been waiting for
you for six months." So they were unpacked and set.
out where they could be seen ; Professor Henry came in,
and the three went over them carefully, the young man
explaining them as well as he could in the light of his
studies. When it was all over and Mr. Mason was
about to go, Baird turned to him and said, "Now I want
you to give all this up." While the young man almost
gasped in astonishment, Baird continued: "If you
devote your life to such a subject as this, you will have
to take the leavings of European workers. It will not
be possible for you here in America to obtain the ma-
terial for important researches ; but — I give you the two
Americas!" Dr. Mason, telling the story when an old
and distinguished man, said, "I was born again that
day."
9. In the meanwhile Baird undertook gigantic Monographs
researches of his own. His activities covered the whole
field of North American vertebrate life. As early as
1857 he published a great work of over 800 pages on the
American mammals, and a year later a still larger
monograph on the birds. So great was his influence
on American ornithology that Dr. Coues, writing on
the history of the subject, sets aside a period of almost
thirty years as the "Bairdian Period." Not only was
Baird's work influential in his own country, but across
the water, in Europe, men took note of his exact
methods and followed them. As the Museum grew, Secretary of
executive duties became heavier and more numerous ;
and in 1878, when Professor Henry died, Baird became
528 ZOOLOGY
head of the Smithsonian. The result was the aban-
donment of Baird's personal researches, and his total
absorption in the work of managing and helping others.
Much of his energy went into efforts to secure funds for
a new building, — efforts which were finally successful,
• thanks in part to the numerous workers who enthusi-
astically came to his aid. Today, still another and
larger National Museum building has been erected, and
it is already crowded.
The Fish io. Toward the end of Baird's life another great
Commission oppOrtunity came to him, and he hastened to meet it,
overburdened with duties as he already was. President
Grant was authorized to appoint a competent man to
inquire into the state of the fisheries, and devise means
for the increase or protection of the fish supply. Baird
was appointed, and instead of making a superficial
inquiry and issuing a report, he took up the whole
problem in a scientific spirit, and undertook to establish
the foundations of a new and fruitful policy which
should govern the fisheries, both marine and fresh-
water. He established a permanent organization,
which is still in existence, and built a biological labora-
tory by the sea, at Wood's Hole, on the coast of Massa-
chusetts. The results exceeded all expectations, and
European workers in the same field, at first incredulous,
were presently enthusiastic followers of Bairdian
methods. Although since Baird's time the Commission
or Bureau of Fisheries has unfortunately suffered from
political influences, the scientific basis of all the work
has never been lost sight of, and the publication of
important theoretical and practical results has con-
tinued without a break.
II. At length the incessant work told upon Baird's
originally robust health, and he was advised to rest.
SPENCER FULLERTON BAIRD 529
Reluctantly he accepted the decision of the doctors, Last days at
but it was too late. The end of his life, at Wood's Hole
Hole, is thus described by Major Powell :
For many long months he contemplated the day of parting. Labor that
knew no rest, responsibility that was never lifted from his shoulders, too soon
brought his life to an end. In the summer of 1887 he returned to his work
by the seaside, that he might die in its midst. There at Wood's Hole he had
created the greatest biologic laboratory of the world ; and in that laboratory,
with the best results of his life work all about him, he calmly and philo-
sophically waited for the time of times. Three days before he died he asked to
be placed in a chair provided with wheels. On this he was moved around
the pier, past the vessels which he had built for research, and through the
laboratory, where many men were at work at their biologic investigations.
For every one he had a word of cheer, though he knew it was the last. At
the same time, along the pier and through the laboratory, a little child was
wheeled. "We are rivals," he said, "but I think that I am the bigger
baby." In this supreme hour he was playing with a child. Then he was
carried to his chamber, where he soon became insensible and remained so
until he was no more.
References
DALL, WILLIAM H. Spencer Fullerton Baird, A Biography. J. B. Lippincott
Company, Philadelphia.
Popular Science Monthly, January, 1906, pages 63-83.
CHAPTER SIXTY-FIVE
The scien-
tific basis
Thought
and action
SOCIOLOGY FROM A BIOLOGIST'S POINT OF VIEW
1. A PURELY objective sociology, regarding dis-
passionately the phenomena of human society, is
scarcely desirable. It may be considered more
"scientific" or "academic" to review the subject as
we might the natural history of snails ; but one who is
trained to study humanity unmoved does not make a
very good citizen. There is an optimum state of mind
somewhere between the extremes of cold scientific
analysis and irresponsible emotionalism. The natural-
ist Wallace said in his old age that he had come to
believe that no one deserved credit for his opinions,
but only for the acts resulting from them. Faith
without works is sterile, even though it be scientific
faith.
2. We must, however, guard ourselves against the
assumption that "pure science" is valueless, when it
appears to have no practical outcome. The study of
snails, or of any other phase of natural history, con-
tributes to that basic philosophy which underlies the
conduct of civilized man. Our sense of security, our
reliance on the order of the Universe, whether we call
it God or by some other name, depends upon our
assurance that system prevails rather than chaos. It
is the task of science to study the book of nature, and
demonstrate that the letters in it spell words, the words
make sentences, and the sentences embody the law
which all must obey. Thus no scientific work is sterile,
provided it really interprets or reveals natural order.
3. Why, then, should not sociology be treated as a
"pure science"? It may be so treated by a certain
number of specialists ; but whereas many studies con-
530
SOCIOLOGY FROM A BIOLOGIST'S POINT OF VIEW 531
tribute to our general idea of nature without suggesting
practical applications, it is impossible for a sensitive
and thoughtful person to study his species without
wishing to act. It is also difficult or impossible for
him to believe that the methods of scientific investiga-
tion cover the whole field. He will never assent to the
proposition that those whom he loves can be described
or defined wholly in terms of anatomy and physiology,
physics and chemistry. In his reaction against such
conceptions, he is likely to make the serious mistake
of undervaluing the contributions of biology and their
meaning for society. The young, however, are at once
relatively plastic and callous, — plastic because their
lives are developing, and many choices are still open ;
callous because experience has not yet filled the imagi-
nation, and many things consequently possess little
suggestive significance. The educational process in-
evitably works an injury when it creates the habit of
thinking without acting, where action should naturally
follow. It is apparently only too possible almost or
quite to eliminate the desire to act. It is for. this reason
that sociology, as an educational subject, should be
something more than "pure science," — should be
dynamic and purposeful, though it stirs the waters of
discontent.
4. The biologically trained individual sees in society Adaptation
a persistent attempt, more or less unconscious, to attain
harmonious relations with the environment. This
environment changes from year to year, largely through
the actions of man himself; hence progress is inevitable.
The growth of human law, "from precedent to prece-
dent," typifies the accumulation of experience, trans-
lated into rules of action. Athwart all this comes
modern science, with her novel discoveries, and com-
532
ZOOLOGY
Socializa-
tion
mands attention with an authority rising above that of
legislatures. The scientific man is the modern prophet,
bearing a message from on high, — truly such, with
little metaphor. When Pasteur revealed the connection
between wound fever and bacteria, it did not matter if
all surgeons prior to his time had acted on a different
supposition. Truth rose above custom, and the denial
of her message cost innumerable lives. Now it may
always be said, not without some measure of justifi-
cation, that the scientific dictum is based on a narrow
point of view, — that the total experience of mankind,
derived from untold centuries of history, may indicate
truths not appreciable in the laboratory. It may be
so, doubtless is so in some measure ; but mankind can
no longer afford to neglect or disobey the word of
science.
5. Thus the student of society has to contemplate
on the one hand an inspiring record of progress, and on
the other a disastrous chronicle of failures. His prac-
tical task is to determine what causes have led to the
one and to the other. How can the good be increased,
the inevitable error and evil diminished ? If he is
scientifically trained, he does not look for his answers
in the writings of the past, any more than he seeks
guidance for himself in some chronicle of his childhood.
We, who live today, are the mature people, who must
think and act in accordance with the stature to which
we have risen. The new point of view, if fully adopted,
would make over our whole system of government and
would enable us really to take advantage of the powers
of the human mind.
6. Having thus gained a point of view, we may dis-
cuss a few practical applications. At the outset it
appears that the application of scientific methods
SOCIOLOGY FROM A BIOLOGISTS POINT OF VIEW 533
demands increased socialization. That is to say, new
social activities are needed, and must be met by taxa-
tion. The water supply, the public health, education,
and many other things come under social direction.
Experts are employed to do things which could not be
intelligently done by the average citizen. The in-
creased burden of taxes, which naturally becomes a
cause of complaint, does not necessarily involve greater
expenditure per capita. Private functions have become
public ones, and the actual amount expended may be
decreased. Still the social standard of living rises, and
such things as public parks, which would formerly have
been considered luxuries, come to be regarded as
necessities. In the educational field higher education
is more and more taken as a matter of course.
7. Yet it becomes evident that even with expert Possibilities
guidance the whole is limited by the condition of its progress
parts. Scientific discovery has today gone far beyond
scientific application. Without an educated and in-
telligent community, the dreams of sociologists can
never be realized. It may be said of some projects, that
they postulate a population of angels or supermen ; that
the limitations of humanity forever render them im-
possible. While this may be true, one who studies the
history and nature of man must be convinced that he is
capable of enormous advances. We have never yet
tried the plan of giving every one the best chance which
society can afford. In our blind and reckless way we
have always sacrificed the prosperity and happiness of
untold numbers in order to attain ends having little or
no social value. The new sociology, rightly applied,
suggests at once the wickedness of past methods and
the way out. But it never can be intelligently applied
by ignorant people.
534
ZOOLOGY
Infant
mortality
The slow
progress of
reform
8. It is useful to make a study of some particular
field of endeavor, and perhaps none is more instructive
than that which deals with infant mortality. Dr. G.
B. Mangold shows that in 10 years the death rate of
infants under one year in New York City declined 31
per cent. In Los Angeles the improvement, according
to published statistics, was actually 43 per cent. For
the states included in the registration area in 1900, the
decline from 1900 to 1911 was 22 per cent. To what is
this due ? Broadly to education and the liberalization
of public opinion, both going back to scientific research
for the facts on which to proceed. Organization on the
one hand, and individual initiative on the other, have
worked this marvel. The public will has decreed that
houses shall be improved, that the milk supply shall be
guarded, that medical advice shall be provided, and so
forth. Yet it has all come through a process of gradual
reform, and history will record no dramatic events, no
groups of revolutionists defending barricades for the
sake of the babies. Most people have no idea what has
happened.
CHAPTER SIXTY-SIX
SOME GENERAL RESULTS
I. FROM our survey of the field of biology we observe : Lawsofiife
a. That life processes are governed by natural laws ;
that is, events follow each other in certain sequences,
which can be observed and classified, and the results
used as guides in estimating probabilities for the future.
b. These "laws," -in reality simply statements of
what happens, — in all their more fundamental aspects,
apply equally to animals and plants. We must there-
fore conclude that they began to operate at the dawn
of life, and will do so while life exists. In other words,
they represent the necessary activities of protoplasm.
c. Science does not reveal all these laws, and prob-
ably never will do so. The conscious mind transcends
the phenomena in such a way that it is able to survey
them as though from a place apart. It is a marvelous
instrument, yet with limitations of many kinds, and it
is impossible for it to know or understand more than a
small part of nature.
d. Nevertheless, great advances in knowledge have Limitations
been made, and greater will be made in the future. °dge°Wl"
Reality is boundless, but truth is reality made manifest ;
the boundaries of truth are ever being enlarged. We
speak of the physical universe, that which may be appre-
ciated by our senses, may be observed and recorded, or
made the subject of experiment. This is the subject
matter of science. Beyond this is the metaphysical
realm, into which we enter by reason of our imagination,
postulating the unknown from the known. Here be-
long what William James called our "over-beliefs,"
which form the basis of our religion. The meta-
physical field, as knowledge grows, is conquered by the
535
536
ZOOLOGY
Duty to use
the knowl-
edge we
have
Harmony
physical, and what was formerly incapable of "proof"
is annexed by the outposts of science. Will meta-
physics some day be abolished, dissolved in the ocean
of positive knowledge ? Will religion come to be wholly
based on the rock of scientific truth ? Not so ; for
outside of and beyond the area of metaphysics is a
greater and wider realm of mttapsy chics, of reality which
at present is beyond the reach of thought. This is easy
to understand, when we think how much of the field of
human thought is metapsychic for the dog, how much
of the dog's for the jellyfish. As science extends its
boundaries, so also the metaphysical field invades the
metapsychical ; and the human imagination, having
gained the heights with a solid footing, uses this advan-
tage to soar farther heavenward.
e. Appreciating all our limitations, we yet see that
the knowledge we have gained is sufficient to guide us
in many ways, and give us innumerable advantages not
possessed by people of earlier days. The failure to
accept and utilize the gospel of modern knowledge is
the great and deadly sin. For example, much of the
misery and death of past centuries was due to causes
beyond human control, but the recurrence of such
events is today preventable. Our ancestors were not
to blame for what they could not help ; but we, who
often could help and will not, must share in the con-
demnation of Cain.
2. The purpose of such activities as we call religious,
ethical, or progressive is to bring about greater harmony
in the world of human affairs. This includes :
a. Harmony between human beings.
b. Harmony between man and his environment, or
correct adjustment to environmental conditions.
The consciousness of harmony attained is happiness.
SOME GENERAL RESULTS 537
which is thus in a broad sense the object of our existence. Happiness
It must be noted that harmony is a positive thing, not
merely the absence of friction or discomfort. Hence
man, having the maximum power of feeling, is capable
of realizing the highest and greatest harmony, or
happiness. By the same token, however, he is capable Piaythe
of the greatest amount of misery ; hence he is compelled game!
to play his game, as it were, to the utmost of his
strength, in order to realize the purpose of his existence.
In the past, man suffered frightfully from his ignorance
of the rules of the game ; that is, of the processes of
nature. His attempts to correct the evils he so keenly
felt were valiant and persistent, but largely wasted
through ignorance. He did not understand that he
was to use his mind to ascertain how things happened ;
he was slow to learn by experience, because he did not
understand his experiences. That intellectual and
moral striving is the price of happiness is not the fanci-
ful idea of some poet or philosopher, but a fact. Hu-
man life is necessarily dynamic. Error and sin consist
in failing to play our part according to the rules of
the game, either by breaking the rules or by failing to
play up.
538 ZOOLOGY
THE LAST LECTURE
Our course is run, our harvest garnered in,
And taking stock of what we have, we note how life,
This strange, mysterious life which now we hold .and now
eludes our grasp,
Is governed still by natural law, and its events
Tread on each other's heels, each one compelled to follow
where the first has led.
Noting all this, and judging by the past,
We form our plans, until we know at last
The treasure in the future's lap.
The man, the plant, the beast, must all obey this law,
Since in the early dawn of this old world
The law was given, and the stuff was made
Which still alone can hold the breath of life :
Whereby we know that grass and man are kin,
The bond a common substance which within
Controls their growth.
Can we know all ? Nay, but the major part
Of all that is must still elude our grasp,
For life transcends itself, and slowly noting what it is,
Gathers but fragments from the stream of time.
Thus what we teach is only partly true.
Not knowing all, we act as if we knew,
Compelled to act or die.
Yet as we grow in wisdom and in skill
The upward path is steeper and each step
Comes nigher unto heaven, piercing the clouds
Which heretofore have hid the stars from view.
The new-gained knowledge seems to fill the air,
It seems to us the soul of truth is there.
Our quest is won.
THE LAST LECTURE 539
Bold climber, all that thou hast won
Lies still in shadow of the peaks above;
Yet in the morning hours the sun
Rewards thy work of love,
Resting a moment on thy lesser height,
Piercing the vault with rays too bright to face,
Strengthens thy soul and gives thee ample might
To serve thy human race.
INDEX
Aberrations, 119.
Acanthocephala, 234.
Acanthopterygii, 356-357.
Accommodation, 378.
Acetabulum, 331.
Achatina, 245.
Achatinellidae, 142.
Adaptation, 31, 35, 81, 184, 420, 445,
49°> S31; immunity, 490; toler-
ance, 490.
Affinity, chemical, 32.
Agapema anona, 291.
Agassiz, Elizabeth Gary, 514, 519.
Agassiz, Louis, 139, 508-519, 522;
early life, 508; zoological interest,
510; authorship, 511; marriages,
512, 514; research on fishes, 512;
glacial theory, 513-514; life in
America, 514-519; Agassiz Mu-
seum, 516; foreign explorations,
517; Penikese summer school,
518; death, 519.
Aglossa, 362.
Agramonte, Dr., 203.
Ailanthus tree, 161.
Albatross (Proellariiformes), 385.
Alces, 411.
Alcohol, effects of, 33, 34, 118, 120-
128.
Alepocephalus, 477.
Algae, 149, 217.
Algonkian Era, 148, 149.
Alimentary canal, 30, 334.
Alleghanian Area, 459.
Allelomorphic characters, 45, 84, 117.
Alligator (Crocodilia), 369-370; A.
mississippiensis, 370.
Alluvial Epoch, 148.
Alopex lagopus, 403.
Amber, 293.
American Museum Journal, 163.
Amia calva, 347.
Amiba, 14, 29, 188, 191, 200.
Amino-acids, 8.
Ammonites, 250.
Amoeba ; see Amiba.
Amphibia, 36, 182, 320, 340, 358-363,
432; see Anura; Apoda; Urodela.
Amphicoelous vertebrae, 329.
Amphididae, 302.
Amphineura, 248.
Amphioxus, 36, 3 21, j 25, 354, 431.
Amphitrite edwardsii, 238.
Anabolic process, 18, 34.
Anaerobic bacteria, 31.
Andrews, C. W., 425.
Angiosperm, 68.
Anguis fragilis, 364.
Animalcule, 17, 192.
Animalia, phyla of, 178-185; charts
of, 183, 185.
Animikian Period, 148.
Annelida, 181, 237-242; see Oli-
gochaeta; Polychaeta.
Annuli, 351.
Anopheles, 203, 205.
Anseriformes, 386.
Ant (Formicidae), 95, 299-307; "ant
lovers," 302; characters, 299;
food, 303; honey a., 304; nests,
301 ; slaves, 305 ; socialists, 306.
Ant, white (Isoptera), 271.
Anther, 77.
Anthidium, 282, 296.
Anthocyanin, 53.
Anthophora, 295.
Anthophysa, 186.
Anthozoa, 211, 213, 216-217.
Anthrax, 486.
Antilocapridae, 413 ; A. americana,
412.
Antiseptic surgery, 485.
Anura, 361-363.
Aorta, 338.
Apatosaurus, 153.
Aphididae, 276-277.
Apis, 296, 297; A. mellifera, 295.
Apoda, 353-354, 359-36o.
Apoidea (Bee), 293-298; adaptation,
294 ; comb, 296 ; fossils, 293 ;
functions, 295-296; habits, 294-
295 ; structure, 297-298.
541
542
INDEX
Appendicularia, 323.
Appendix vermiformis, 139.
Aptera (Protura), 267.
Apteryx, 385.
Arachnida, 182, 202, 255, 261-262.
Arachnoidea, 259-263.
Archseopteryx, 379, 380.
Archeozoic Era, 148.
Archiannelida, 237.
Archiptera, 35, 269-270.
Arctic and Antarctic Regions, 467-
471.
Arctic-alpine Life Zone, 456.
Areas, 459-461.
Arid Transition Area, 459.
Aristotle, 219; A.'s lantern, 219.
Armadillo, 38, 409.
Artemisia, 459.
Arthropoda, 180, 182, 191, 202, 218,
237, 238, 243, 253-279, 472; see
Arachnoidea ; Chilopoda ; Crus-
tacea; Diplopoda; Insecta;
Myriapoda ; Prototracheata.
Artiodactyla, 410, 416.
Ascaris, 234.
Ascidians (Tunicata), 321, 322, 323.
Aspidiotus perniciosus, 310.
Asteroidea, 218, 222.
Asterozoa, 221, 222.
Atom, 6, 14, 37, 46; complexity of,
6; determiner of heredity, 46;
in protoplasm, 14; individuality
of life in, 37; instability of, in
protoplasm, 6; stability of, in
water, 6.
Auchenia pacos, 413.
Audubon, 521-522.
Aulacaspis rosse, 79.
Auricles, 338, 340.
Austral Life Zones, 460-461.
Australian Region, 448, 452.
Austro-riparian Area, 459, 461.
Aves, 182, 340, 341, 373-395-
Axis axis, 412.
Babesia, 206.
Bacteria, 26-27, 3*, 126, 131, 134,
H9, 338, 464, 483, 485, 490, 49i;
anaerobic, 3 1 ; bacillus, 278, 486.
Baird, S. F., 520-529; early life,
520-521; teacher, 523; appoint-
ment to Smithsonian, 523; merg-
ing Smithsonian into U. S. Na-
tional Museum, 524-528; founding
Wood's Hole Biological Labora-
tory, 528; death, 529.
Baker, F. C., 252.
Balanoglossus, 321, 324.
Barnacles (Cirripedia), no, 218.
Barramunda (Neoceratodus), 344,
345-
Barrell, Joseph, 148, 156.
Bates, H. W., 290, 291, 292.
Batesian mimicry, 291.
Bateson, 49.
Batrachia Salientia, 361.
Bears (Ursidae), 402.
Beaujeu, Quinqueran de, 308.
Beccari, 464.
Beddard, F. E., 241.
Bee (Apoidea), 293-298; adaptation,
294; comb, 296; fossils, 293;
functions, 295-296; habits, 294-
295 ; structure, 297-298.
Beebe, C. W., 374, 395- -
Beetle (Coleoptera), 276.
Benthos, 476, 477.
Bergson, 12.
Binney, W. G., 252.
Biologia Centrali-Americana, 466.
Biology: history, 492-499; life-
regions, 447-453; sociology, 530-
534; study's results, 535-537-
Biot, J. J, 480, 483.
Biota, 446; circumpolar, 450.
Birds (Aves), 182, 340, 341, 373~395 5
anatomy, 377; feathers, 374, 377;
moulting, 376; senses, 378; see
Anseriformes ; Apterygiformes ;
Casuariiformes ; Charadriiformes ;
Ciconiiformes ; Colymbiformes ;
Coraliiformes ; Cuculiformes ;
Falconiformes ; Galliformes ; Grui-
formes; Passeriformes ; Proellarii-
formes ; Rheiformes ; Spenisci-
formes ; Struthioniformes.
Bisexual reproduction, 75 ; see also
Generation.
INDEX
543
Blastoids, 22.
Blastopore, 430.
Blatchley, W. S., 319.
Blattidae, 319.
Blood, 25-27, 34, 337-340; arterial,
34; circulation of, 338-340; com-
position of, 26, 34, 337; structure
of, 25 ; venous, 34.
Boerhaave, Dr., 168.
Boreal Life Zone, 456-459.
Bovidae, 413.
Brachiopoda, 180, 227-228; see aiso
Bryozoa.
Brain, 334-336; cerebellum, 336;
hemispheres, 336; medulla ob-
longata, 336; olfactory lobes, 336;
optic lobes, 336.
Branchiostoma (Amphioxus), 36, 321,
325, 354; B. canceolatum, 325.
Branta canadensis, 387.
Braun, Alexander, 510.
Bridges, C. B., 71, 83, 116.
Brontosaurus, 153.
Brues, C. T., 279.
Bryozoa, 180, 226-227, 261; see also
Brachiopoda.
Budding, 40.
Burne-Jones, Edward, 52.
Butler, Samuel, 18.
Butterflies ; see Lepidoptera.
Caddis-fly (Trichoptera), 273, 289.
Calcium, 20.
Caliroa cerasi, 275.
Cambrian Period, 147, 148, 149, 150,
253, 257.
Cambridge Natural History, 24.1.
Camel (Camelidse), 142, 411.
Campodea, 269.
Canadian Epoch, 148.
Canadian Life Zone, 457.
Cancer, 15.
Canidae, 402.
Capra, 414.
Carapace, 368.
Carbohydrates, 31.
Carbon, 19, 31, 32.
Carboniferous times, 150, 202, 260,
313, 316; see also Palaeozoic Era.
Carex aquatilis, 65.
Carnivora, 401-402, 416; see
Canidae ; Felidae ; Hyaenidae ;
Mustelidae ; Procyonidae ; Ur-
sidae; Viverridae.
Carolina Area, 459, 460.
Carpus, 332.
Carroll, Dr., 203.
Castor, 407.
Casuariiformes, 384.
Catarrhine, 409.
Caterpillars (Larvae), 288; see also
Metamorphosis.
Catocala, 289.
Catostomidae, 354.
Cats, lions, tigers; see Felidae.
Cavia, 407.
Cecropia, 289.
Cells, 5, 9-10, 13-21, 31, 37, 63;
columnar, 23 ; continuity of life
of, 16-18; evolution of, 15;
functions of, 13-16; marginal
and submarginal, 298; Mendelism
vs., 50; metabolism of, 18-21;
reproduction of, 15; squamous,
23 ; structure of, 13.
Cellulose, 13, 186.
Celsius, 167.
Cenozoic Era, 148, 152, 154.
Centipedes ; see Diplopoda.
Centrum, 329.
Cephalopoda, 250-252.
Cephalothorax, 259.
Cercariae, 231.
Cerceris, 283.
Cerebellum, 336.
Cerebral hemispheres, 336.
Cervidae, 411.
Cestoda, 229, 231-232, 234.
Chaetae, 237.
Chaetognatha, 181.
Chamberlin, T. C., 15.
Champlainian Epoch, 148.
Characters : allelomorphic, 45 ;
dominant, 44, 47; in inheritance,
43-48; "laws of chance," 48;
recessive, 44, 47, 504; retention
of, 7; specific, 64.
Charadiiformes, 389.
544
INDEX
Charpentier, 513.
Chelone, 369; C. imbricata, 368.
Chelonia, 368.
Chemistry: affinity of carbon and
oxygen, 32; inorganic and or-
ganic, 7; of protoplasm, 5.
Chico Cretaceous, 353.
Chilopoda, 182, 202, 266.
Chimseras (Holocephali), 343.
Chiroptera, 399.
Chitin, 253.
Chitons, 248-249.
Chlorophyll, 53.
Cholaepus hoffmanni, 408.
Chondrostei, 347.
Chordata, 182.
Chorions, 87.
Chromatin, 62.
Chromodoris, 248 ; C. porterae, 248.
Chromosomes, 62-72, 74, 81, 82, 116;
chromatin, 62; cytoplasm, 62;
fertilization, 66-68; linkage, 69;
maturation, 64 ; mitosis, 65 ; mu-
tation, 64 ; numbers, 63 ; synap-
sis, 69; variability, 72.
Chrysalis, 288.
Chrysopa, 271.
Cicada ; see Rhynchota.
Ciconiiformes, 385-386.
Cilia, 23, 180, 190, 192, 193.
Ciliata (Infusoria), 192-193, 201.
Cincinnatian Epoch, 148.
Circulatory system, 338-340.
Circuli, 351.
Cirrepedia, no, 218.
Clams ; see Mollusca.
Clark, A. H., 212.
Classification, principles of, 175-177;
Linnaean, 169-173; natural, 171.
Clavicle, 330.
Clupea, 353.
Clypeus, 85.
Cobb, Dr. M. A., 234, 235.
Coccidae, 302, 308-312.
Cochinilla (cochineal), 308, 309.
Cockroach (Blattidae), 319.
Ccelenterata, 73, 95, 180, 210-217,
218, 430; quardripartite, 212; see
Anthozoa; Hydrozoa; Scyphozoa.
Ccelom, 211.
Coleoptera, 276.
Collembola, 267, 268.
olloids, 9-12.
olonization, 95.
bloradian Area, 459.
Coloradian Epoch, 148.
Coloration: protective, 289, 291,
292; warning, 290, 372.
Columba livia, 389.
Columbian Area, 460.
Columbiformes, 385.
Comanchian Period, 148.
Combustion, 33.
Compositae, 51, 392.
Compounds, 7.
Comstock, A. B., 279.
Comstock, J. H., 279.
Conjugation, 17, 80 ; see also Genera-
tion.
Consciousness, 29-30.
Continuity of life, 16-17; °f proto-
plasm, 17.
Conus arteriosus, 338.
Cooperation, 94.
Coraciiformes, 391-392.
Coracoid process, 330; c. bone,
330-
Coral animals (Polyps), 217; reefs,
217.
Corbicula, 294.
Corns, 24.
Corpuscles, blood, 337-338; red and
white, 26; haemoglobin, 34; leu-
cocytes, 14, 26.
Correns, 49.
Corrodentia, 272.
Coues, Dr., 389, 527.
Crabs ; see Crustacea.
Crampton, Dr. G. C., 257.
Cretaceous Period, 148, 151, 153, 154,
379-
Cricket (Orthoptera), 269, 313-319;
Italian c., 281.
Crinoids, 221, 222.
Crocodilia, 369-370; see Reptilia.
Cro-Magnon man, 422, 441, 489.
Croixian Epoch, 148.
Crossopterygii, 346.
INDEX
545
Crustacea, 182, 224, 237, 255, 256
C. isopod, 256, 257-259, 263, 467.
• Crystalloids, 9-10.
Ctenoid fish scales, 349.
Ctenophora, 180.
Cuvier, 511.
Cuvierian organs, 224.
Cycads, 294.
Cycloid fish scales, 349.
Cyclostomes, 320-321, 326-327, 340.
Cylaelurus jubatus, 40x3.
Cynomys, 407.
Cyprinidae, 354.
Cysticercus, 232.
Cystoids, 221.
Cytology vs. Mendelism, 50.
Cytoplasm, 62, 66, 81.
Dahlia, 59.
Dall, 516, 529.
Danaus archippus, 289.
Darwin, Charles, n, 49, 101-114,
131, 132, 141, 142, 217, 240, 290,
500, 501, 506, 516, 520, 521; early
life, 101 ; college life, 103 ; trip
on Beagle, 104; invalidism, 105,
112, 500; influence of Malthus,
107; marriage, 108; scientific
labors, no; evolution, works on,
110-114; death, 114.
Darwin, Dr. Erasmus, 101.
Darwin, Francis, no, 112.
Dasypus novemcinctus, 409.
Davis, W.M., 217.
De Vries, Hugo, 49, 64, 143.
Dearborn, N., 395.
Death vs. life, 17.
Dentalium, 249.
Determiners, of sex, 45-46, 116, 196.
Devonian Period, 148, 150.
Dianthidium, 296.
Diatoms, 477.
Diatryma, 379, 381.
Dickerson, M. C., 363.
Didymium, 189, 190.
Difflugia, 191, 192; D. acuminata,
191; D. capreolata, 191; D.
rubescens, 191.
Digits, 332.
Dimorphism, 79, 299; sexual d., 312.
Dinonys branicki, 406.
Dinornis, 383, 352; D. maximus, 383.
Dinosaur, 152, 365-367, 397; D.
diplodocus, 152, 266, 367.
Diplodocus, 152, 266, 367.
Diplopoda, 265, 266.
Dipneusti, 344.
Diptera, 204, 267, 278-279.
Disease : eugenics vs., 506-507 ;
evolution vs., 489-491 ; history
vs., 496-498; insecta vs., 279;
protozoa vs., 199-206.
Distribution, geographical, 141, 442-
446.
Divisions, geological, 148.
Dobson flies ; see Neuroptera.
Dogs, foxes, wolves ; see Canidae.
Dominants, 44, 117.
Dragon flies ; see Odonata.
Drosera, n.
Drosophila, 69, 70, 71, 83, 84, 116.
Ducks ; see Anseriformes.
Duckbill, 152.
Duckworth, W. L. H., 441.
Dufour, Leon, 283.
Dumas, J. B., 484.
Eagles ; see Falconiformes.
Earthworms ; see Oligochseta.
Echidna (Tachyglossus), 396; E.
acleata, 397.
Echiniscus, 254.
Echinodermata, 39, 180, 212, 218-
225,325; see Asterozoa; Echino-
zoa; Pelmatozoa.
Echinoidea, 222.
Echinozoa, 221, 222.
Echinus, 37, 219, 223.
Ectoderm (Epiblast), 210, 329.
Edentata, 407.
Eicherax, 278.
Elasmobranchii, 340, 342-344.
Electron, 6.
Elephant; see Elephas.
Elephas, 425-428; E. columbi, 427,
428 ; E. imperator, 428 ; E. primi-
genius, 428.
Ellis, Max M., 242.
546
INDEX
Eltringham, 292.
Embryo, 68, 87, 139, 430.
Emerson, 516.
Emeu, 383, 384.
Endemism, 444. .
Endoderm (Hypoblast), 210.
Endoskeleton, 328.
Endosperm, 68.
Energy, 314; kinetic, 4, 32; "libera-
tion" of, 3-4; oscillation between
kinetic and potential, 4; potential,
4, 32; translation of, 4.
Entamoeba, 200.
Entomostraca, 259.
Environment, life vs., 89-93, I][8,
195,442,490, 505, 506, 531.
Eoanthropus, 439.
Eocene Epoch, 148, 155, 244, 378,
417, 418, 427.
Eohippus, 418, 419, 420, 421.
Ephemeroidea (Plectoptera), 269.
Epiblast (Ectoderm), 210.
Epidermis, 23, 24.
Epiphytes, 464, 465.
Epithelium, 22, 30.
Epochs, geological, 148.
Equus (horse), 417-425 ; E. asiaticus,
424; E. burchelli granti, 415; E.
caballus, 422 ; E. celticus, 423 ;
E. przewalskii, 421, 422, 423; E.
scotti, 418, 421.
Eras, geological, 148.
Erinaceus europaeus, 399.
Esocidae, 355.
Ethiopian Region, 448, 451.
Eucrustacea, 257-259.
Eugenics, 500-507; disease vs., 506-
507 ; education vs., 505 ; environ-
ment vs., 505; ideals vs., 502; in-
heritance vs., 501-503 ; invalidism
vs., 500; man's heterozygous na-
ture vs., 501 ; objections to,
500; recessive characters vs.,
504; sexual selection vs., 502, 506.
Euglena, 186; E. viridis, 188.
Euplectella aspergillum, 208.
Euproops danse, 260.
Eurypauropus, 266.
Eurypterids, 321, 322.
Eutheria, 396, 397-414; see Mar-
supials ; Placentals.
Evolution of life, 15-16, 43, 92;
arguments for, 137-143; disease
vs., 489-491 ; history vs., 492-499.
Ewart, J. C., 423, 424.
Excretions, 20, 30.
Exoskeleton, 253.
Fabre, J. Henri, 280-285 ; early life,
280-281; spirit of, 280; teacher,
282-283; author, 283; festival
at Serignan, 284; death, 284.
Falconiformes (Raptores), 386.
Fauna, 140, 150, 302, 365, 447, 452,
474, 477; of British India, 466.
Feathers of birds, 373, 374-377.
Feeblemindedness, 121.
Felidae, 401 ; felis leo, 400.
Femur, 332.
Fermentation, 31.
Fertilization, 63, 65, 66, 73-76; con-
jugation, 73 ; cross- and self-f., 75-
76; development, 75; division,
73; egg and sperm cells in, 74;
parthenogenesis, 74; see also
Generation.
Fibula, 332.
Filaria, 234.
Fischer, Emil, 8.
Fishes (Pisces), 182, 340, 342-357,
431,467; see Dipneusti ; Elasmo-
branchii ; Ganoids ; Teleostomi.
FitzRoy, Captain, 104.
Flacherie, 484.
Flagellates, 187-189; flagellum, 187.
Flatworms ; see Platyhelminthes.
Flavone, 54.
Fleas (Siphonaptera), 278.
Flies (Diptera), 204, 267, 278-279.
Flora Lapponica, 168.
Florissant shales, 157-163, 206.
Flower (author}, 416.
Flowers, 77.
Flukes (Trematoda), 180.
Foods, oxidation of, 33-34.
Foramen ovale, 340.
Foraminifera, 187, 192, 476, 477.
Forel, 172.
INDEX
547
Forma ("Form"), 119.
Formica fusca, 305; F. rufa, 300;
F. sanguinea, 305.
Formicidse (ant), 95-96, 299-307;
honey-ant, 304; polyergus, 96.
Fossils, 144-156, 243, 293, 313, 365,
366, 379, 425, 428, 432, 440, 446;
formation of, 158; geologic time-
table of, 147-148 ; types of, 144.
Fowl (Galliformes), 388.
Fringillidae, 395.
Gadow, H., 362, 363, 368, 372.
Galapagos Islands, 107, 141 ; tor-
toise of, 369.
Galliformes, 388.
Callus gallus, 388.
Galton, Francis, 500, 505; Galton
Laboratory of National Eugenics,
IOI.
Gamete, 55, 63, 66, 67, 74, 77, 81, 116.
Gametophytes, 68.
Ganglia, 334.
Ganoids, 345-347.
Gardner, G., 205.
Garman, 516.
Gasquet, F. A., 496, 497.
Gastric juice, 30.
Gastropoda, 243-248, 249.
Gastrotricha, 181.
Gelation, 10, 12; reversible and
irreversible, 10.
Gels, 10.
Generation (reproduction) : breeding,
46-48 ; characters in, 44-45 ; chro-
mosomes in, 62-72; determiners
of sex, 45; division, 38-40; of
defectives, 505-507 ; of individuals,
38; of monsters, 38; of twins, 38;
parental and filial, 45 ; poly-
embryony, 38; spontaneous, 483.
Genus, 170.
Geographical distribution, 141, 442-
446.
Geologic Time Table, 147-148.
Geophilus, 266.
Germ, continuity of life in, 17.
Gila (Heloderma), 370, 371.
Giraffidse, 411.
Girdles: pectoral and pelvic, 329,
330-33L
Glacial Period, 148.
Gland tissue, 29-30; function of,
29-30; structure of, 30.
Glochidium, 446.
Glossina, 161, 162, 204; G. morsitans,
205, 206; G. palpalis, 205, 206;
G. (tsetse), 161, 204, 279.
Glowworm, phosphorescence of, 33.
Goddard, Dr. H. H., 121, 128.
Goniodes falcicornis, 272.
Goose (Anseriformes), 386.
Gordius, 234.
Gould, Alice Bache, 519.
Graellsia isabellae, 290.
Grant, President, 528.
Grasshoppers (Orthoptera), 313-319.
Green plants, 31; see also Chloro-
phyll.
Gregarines, 191, 202.
Gregory, W. K., 341.
Gruiformes, 389.
Guinea pigs, experiments with, 121.
Gulf Stream, life in, 474.
Gulf Strip Area, 461.
Guyer, 10.
Gymnogyps californianus, 384.
Gynandromorphs, 85.
Haeckel, Professor (of Jena), 187.
Haemoglobin, 34, 239, 337.
Hagfishes ; see Cyclostomes.
Haliaetus leucocephalus, 386.
Halicti, 280, 294.
Hall, Maurice C, 241.
Haplomi, 355-356.
Harring, H. K., 236.
Hartog, Marcus, 236.
Hawaiian Islands, life on, 142.
Heart, 338.
Heat, 33.
Helianthus (sunflower), 51-61; as
typical of Mendelian phenomena,
51-61; collarette of, 59; H.
annuus, 51, 59; H. cucumeri-
folius, 59; H. tortuosus, 59;
see also Mendel, G. J. ; Mendelism.
Heliozoa ("sun animalcules"), 192.
548
INDEX
Helix nemoralis, 115.
Heloderma (Gila), 370, 371; H.
suspectum, 371.
Hemilastena ambigua, 446.
Hemiptera (Homoptera) (Rhyn-
chota), 64, 276, 277.
Hemoglobin; see Haemoglobin.
Hemosporidia, 201.
Henry, 523-527-
Henslow, John Stevens, 104.
Heredity: alcohol vs., 120-128;
>nature and nurture vs., 89-93 ;
protozoa vs., 194-198.
Hermaphrodites, 78.
Hernandez, Francisco, 308.
Hesperornis, 154, 379.
Heteroptera (Hemiptera), 277.
Heterozygous (cross-bred) individ-
uals, 46, 57-61, 67, 72, 84, 85, 127,
133, 134, 5OI> 504-
Hiort, 478.
Hippopotamidse, 410; hippopotamus
amphibius, 411.
Hirudinea, 181, 237, 241; hirudo
medicinalis, 241.
History, of life, 144-156; vs. biology,
492-499; see also Life.
Holarctic Region, 450.
Holland, W. J., 292.
Holmes, 516.
Holocephali (Chimaeras), 343.
Holothuroidea, 222, 224; see also
Synapta.
Holt, Caroline M., 63.
Hominidae, 175-176, 434, 435, 43§;
Homo, 175, 176; H. Cro-Magnon,
422, 441; "H. diluvii testis,"
360; H. heidelbergensis, 440;
H. neanderthalensis, 440; H.
sapiens europseus : see below.
Homo sapiens europaeus (man), 175,
176, 341; ancestry, 429; char-
acters of, 435-438; diseases vs.
development of, 489-491 ; eu-
genics vs., 500-507; evolution of
(protozoan to hominidcsan stages},
429-434; history vs., 492-4995
relatives of, 438-441; sociology
vs. biological viewpoint, 530-534.
Homology of organs, etc., 138.
Homonyms vs. synonyms, 174.
Homoptera, 277.
Homozygous (pure-bred) individuals,
46, 56-61, 67, 117, 127, 134, 504.
Honey ants, 304.
Honeybees, 296.
Hooker, Sir Joseph, in.
Hookworm ; see Nematoda.
Hormones, 87.
Horns, 23.
Horse (Equus), 417-425; Equus
asiaticus, 424; E. burchelli granti,
415; E. caballus, 422; E. celticus,
423; E. przewalskii, 421, 422,
423; E. scotti, 418, 421.
Hosts, of parasites, 201-206, 231.
Howard, L. O., 279.
Hudsonian Life Zone, 457.
Humblebees, 296.
Humboldt, Alexander v., 512, 514.
Humerus, 332.
Humid Northwestern Area, 460.
Huronian Period, 148.
Huxley, T. H., 112, 341, 429, 522.
Hyatt, 516.
Hybridization, 42-44, 119; see also
Mendel, G. J. ; Mendelism.
Hydatina senta, 236.
Hydra, 73, 212; H. oligactis, 213.
Hydrochloric acid, 20.
Hydrogen, 31.
Hydromedusae ; see Hydrozoa.
Hydrophobia (rabies), cure for, 487.
Hydrotheca, 214, 215.
Hydrozoa (Hydromedusae), 213-215;
. Hydra, 73, 212; hydrotheca, 214,
215.
Hyaenidae, 401.
Hyenas ; see Hyaenidae.
Hylidse, 363.
Hymenoptera, 95, 274-275, 276, 282;
ant, 299-307; bee, 293-298; see
also Ant ; Bee.
Hypoblast (Endoderm), 210.
Hypsodon (Portheus), 348.
Hyracotherium, 421.
Icerya purchasi, 309.
INDEX
549
Ichneumon flies ; see Hymenoptera.
Ichthyophis, 360.
Ichthyornis, 379.
Ichthyosaur, 365.
Identity retention, 7.
Iguana tuberculata, 371.
Iguanodon, 331.
Ilium, 331.
Imago, 288.
Impulses, of nerves, 33.
Individuality, 37-40; complexity of,
492; generation of, 37-38, 420;
uniqueness of, 493.
Infusoria (ciliates), 192-193.
Inheritance, 494-495, 501-503.
Insecta (Arthropoda), 182, 202, 237,
255,267-279,308-319; see Archip-
tera ; Coleoptera ; Collembola ;
Corrodentia ; Diptera ; Hemip-
tera (Rhynchota) ; Hymenoptera ;
Isoptera ; Lepidoptera ; Mallo-
phaga ; Mecaptera (Panorpatas) ;
Neuroptera ; Odonata ; Orthop-
tera ; Protura ; Siphonaptera ;
Siphunculata ; Thysanoptera ;
Thysanura ; Trichoptera.
Insectivora, 399.
Invertebrates, 178, 467.
Irritability, 10.
Isocrania, 227.
Isopoda, 258.
Isoptera, 271.
Isospondyli, 352-353.
Isotherm, 454, 455.
James, William, 506, 517, 535.
Jellyfish (Ccelenterata), 95.
Jennings, H. S., 80, 138, 194, 195,
197, 198, 219, 220.
Johannseri, O. A., 279.
Johnstone, James, 478.
Jordan, David Starr, 341, 357, 516,
520.
Jurassic Period, 148, 379.
Kalm, Peter, 169.
Kalmia, 169.
Kangaroo; see Marsupials.
Katabolic process, 18, 20, 34.
Katydids , see Orthoptera.
Keats, 500.
Keep, Josiah, 252.
Keeweenawan Period, 148.
Kellicott, W. E., 341.
Kellogg, V. L., 279-
Kennicott, 524.
Kermes, 308, 309.
Kewatin Period, 148.
Kidneys, 30.
King, Homo neanderthalensis of, 440.
Kinorhyncha, 181.
Kiwis ; see Apteryx.
Knight, C. R., 153, 155.
Knowlton, F. H., 159, 395.
Koch, 486.
Kollar, 41.
Lac, 309.
Lacerta vivipara, 364.
Lacertilia, 370.
Lace-wing fly ; see Chrysopa.
Lagena Marine, 192.
"Lake" (coloring), 309.
Lamarck, 64, 143.
Lamellae, 246.
Lamellibranchiata, 249-250.
Lampreys ; see Cyclostomes.
"Lampshells," 180, 227.
Lampsilis luteolus, 446.
Lance Epoch, 148.
Larvacea, 323.
Larvae, of insects, 288.
Lasius, 302.
Laurel ; see Kalmia.
Laurent, M., 482.
Laws- of life, I, 48, 535.
Lazear, J. W., 203.
Leadership, 98.
Leeches (Hirudinea), 181, 237, 241.
LeGros, C. V., 285.
Lemur varius, 409.
Lepidoptera, 273, 274, 286-292;
see Microlepidoptera ; Rhopalo-
cera; Saturniidae.
Lepidosiren, 345.
Lepisma, 268.
Leucocytes, 14, 26.
Lice: Biting lice (on birds); see
550
INDEX
Mallophaga ; Book lice ; see Cor-
rodentia; Plant lice; see Rhyn-
chota ; True lice (on man) ; see
Siphunculata.
Life, 2-4, 5-12, 94-100, 144-156,
442-478 ; colonization of, 95 ;
continuity of, 16; cooperation of,
94; death vs., 17; distribution
of, 442-446; energy of, 11-12;
evolution of, 15-16, 43, 92;
geographical conditions vs., 447-
453; happiness in, 537; harmony
of, ' 536; history of, 144-156;
influences on, 442-446; laws of,
i, 48, 535; leadership in, 98;
• manifestations of, 3-4; origin of,
3 ; protoplasm the vital element
of, 5-6; rhythm of, 12; socialism
of, 94-100; specialization of, 99;
symbiosis, 94; uniqueness of, 2;
zones of, 454-478 ; see also Evolu-
tion; Man; Protozoa; etc.
Light, 33.
Lilium canadense, 63, 69.
Lillie, Frank R., 87.
Limax, 246.
Limbs, of vertebrates, 329, 332-334.
Limulus polyphemus, 260.
Lineus, 233.
Lingula, 227, 228.
Linkage, 69, 70.
Linnsea borealis, 168.
Linnsean classification, 169-173.
Linnaeus, Carolus (Carl v. Linne),
164-174, 422, 435; boyhood, 164-
165; college life, 166; "privat
decent," 167; explorer, 167;
physician, 169; professor of
botany, 169; system of classi-
fication, 169-173 ; death, 173-174.
Lions, tigers (cat family) ; see
Felidse.
Lister, Joseph, 485.
Litchfield, Henrietta, 114.
Littoral Zone, 473, 474, 477.
Liver, 30.
Lizards (Reptilia), 39, 364.
Llama (Camelidae), 142.
Locusts (Orthoptera), 313-319.
Loeb, Jacques, 37, 75, 76.
Longfellow, H. W., 516.
Lowell, J. R., 516.
Loxodonta, 428.
Lucilia, 278.
Lull, R. S., 418.
Luna, 289.
Lungs, 36.
Lutz, F. E., 279.
Lycaon, 404.
Lydekker, Richard, 416.
Lyell, Sir Charles, in.
Lymnaea, 231, 247.
Lysophiuroida, 222.
Macropus giganteus, 398.
Maistro, Xavier de, 281.
Malacostraca, 259.
Malaria, parasite of, 191, 203.
Mallophaga, 272.
Malthus, "On Population," 107.
Mammals (Mammalia), 182, 340,
34i, 373, 396-4i6> 432, 435;
characteristics, 396; see Eutheria;
'Prototheria.
Mammoth, 426.
Man (Homo sapiens europseus), 175,
176, 341; ancestry, 429; char-
acters of, 435-438; diseases vs.
development of, 489-491 ; eu-
genics vs., 500-509; evolution of
(protozoan to hominideean stages),
429-434; history vs., 492-499 ;
relatives of, 438-441; sociology
vs. biological viewpoint, 530-534.
Mandible, 329-330.
Mangold, G. B., 534.
Mantidse, 318; mantis religiosus,
281, 318.
Marcou, Jules, 519.
Marmosa, 432.
Marmota, 407.
Marriage vs. eugenics, 500-507; set
Eugenics.
Marsh, 155.
Marshall, A., 363.
Marsupials, 397-398, 433-
Mason, Dr. O. T., 526.
Mastax, 235.
INDEX
551
Mastigophora (Flagellates), 187-189.
Mastodon, 425, 426; M. ameri-
canus, 427.
Matter, 3; inorganic and organic,
7; living substance, 5-12; see
also Life.
Matthew, W. D., 156, 372.
Maturation, 64, 65.
May flies ; see Odonata.
Mecaptera (Panorpatse), 274.
Medulla oblongata, 336.
Medusae, 212.
Megachile, 296, 297.
Megilla, 276.
Meister, Joseph, 487.
Melander, A. L., 279.
Melicerta, 236.
Melipona, 297.
Melissodes, 85.
Memory, 29.
Mendel, Gregor Johan, 41-50; early
life, 41 ; priesthood, 41 ; teacher,
41; scientific interest, 42; work
with peas, 42-45 ; death, 49 ; see
also Mendelism.
Mendelism, 42-50, 51, 57, 117, 133;
applications of, 49-50; characters
in inheritance, 44-45; cytology
vs., 50; determiners, 45-46 ; domi-
nant and recessive strains, 44-45 ;
formulae, 45, 46, 47, 48 ; hybridiza-
tion, 42-44; inheritance, 46-48;
"Three-to-one" ratio, 45; see also
Mendel; Red Sunflower (Helian-
thus).
Mental defectives, 121.
Merriam, C. H., 454, 455, 456.
Merychippus, 418.
Mesoblast (Mesoderm), 210, 329.
Mesoderm (Mesoblast), 210, 329.
Mesogloea, 210.
Mesohippus, 418.
Mesophytic vegetation, 457.
Mesozoic Era, 140, 148, 151, 152, 154,
222, 348, 365, 366, 380, 396, 432.
Metabolism, 18-19; anabolism and
katabolism, 18, 34; assimilation
of food, 19-21; excretions and
secretions, 20.
Metacarpals, 332.
Metamorphosis, 267, 269, 272, 274,
275, 276, 277, 278, 357, 358.
Metaphysics, 535.
Metapsy chics, 536.
Metatarsals, 334.
Metazoa, 180, 210.
Microlepidoptera, 289.
Miller, G. S., 441.
Mimicry, 291; Batesian m., 291;
Miillerian m., 291.
Miocene Epoch, 148, 155, 157, 162,
163, 418, 425, 427.
Mississippian Period, 148, 150.
Mitosis, 65.
Moa ; see Dinornis.
Modern Era, 148.
Moeritherium, 425, 427.
Moisture vs. life, 455.
Molds, slime, 189.
Molecule, 6, 14, 37.
Mollusca, 182, 225, 239, 243-252;
see Amphineura ; Cephalopoda ;
Gastropoda ; Lamellibranchiata.
Momotus, 377.
Mongoose ; see Viverridae.
Monotremata, 396.
Monstrosities, 38.
Montanian Epoch, 148.
Moore, Anne, 121.
Moore, J. P., 242.
Moquin-Tandon, 282.
Morgan, T. H., 69, 84, 86, 87.
Morse, 516.
Mortality, infant, 534.
Mosquitoes (Nematocera), 278.
Moths ; see Lepidoptera.
Moulting, 376-377.
Movement, 33.
Miiller, Fritz, 292, 293; Miillerian
mimicry, 291.
Murex, 247.
Murray, 478.
Muscles, 27-28; contractions of, 33;
functions of, 27; striated and un-
striated m. cells, 27; structure of,
27-28.
Mustelidae, 401, 403; Mustek ni-
gripes, 403.
552
INDEX
Mustelus, 343.
Mutation, 64, 90, 143.
Mycetozoa, 186, 187, 189-190.
Myotomes, 326.
Myriapoda, 182, 202, 255, 265.
Myrmecophaga jubata, 408.
Myrmecophiles, 302.
Mystacoceti, 414.
Nacre (pearl), 250.
Nagana, 201, 206.
Nageli, 49.
Nansen, Fridtjof, 468, 471.
Nature, I ; nature and nurture vs.
heredity and environment, 89-93.
Nautilus, 251.
Neanderthal man, 440, 489.
Nearctic Region, 448, 450.
Necturus, 320, 446.
Nekton, 475.
Nemathelminthes, 180, 233-235.
Nematocera, 278.
Nematoda, 234, 235.
Nematomorpha, 234; the Gordius,
234-
Nemertinea, 180, 233.
Neoceratodus (Barramunda), 344,
345 ; N. forsteri, 344.
Neo-Laurentian (Proterozoic) Era,
148.
Neotoma cinerea orolestes, 405.
Neotropical Region, 448, 450.
Nereis, 238.
Nerves, u, 28-29, 334~3375 a^~
ferent and efferent n., 336; func-
tion of, 28; impulses, II, 33;
structure, 29; system, nervous,
10, 334-337-
Neural arch, 329.
Neuroptera, 271, 273, 274.
Newman, H. H., 38.
Newton, Alfred, 395.
Newton, Sir Isaac, 114.
Nicholson, 232.
Nictitating membrane, 379.
Nitrogen, 31.
Noctiluca, 189.
Nomenclature, botanical and zoolog-
ical, 170.
Notochord, 320, 326, 431.
Notophthalmus viridescens, 360.
Notoryctes, 398.
Notropis cornutus, 349.
Novius cardinalis, 309.
Nucleoplasm, 62.
Nucleus, 62, 65.
Nudibranchs, 246-248.
Nurture, nature and, 89-93.
Nyctereutes procyonides, 404.
Nymphs, 35, 270.
Obelia commissuralis, 214.
Oboraria ellipsis, 446.
Ochotona saxatilis, 405.
Octopus, 251.
Odobaenus, 404.
Odontoceti, 414.
CEnothera gigas, 64.
Oleander hawk moth, 287.
Olfactory lobes, 336.
Oligochaeta, 237, 239-241.
Oligocene Epoch, 148, 418.
Olor olor, 387.
Ontogeny vs. phylogeny, 140.
Onychophora (Prototracheata), 255,
263.
Oocyte, 66, 67.
Oogenesis, 67.
Ooze, ocean, 477.
Opalina, 201.
Operculum, 248.
Ophidia, 364, 372.
Ophiuroidea, 222.
Opossum (Marsupial), 142.
Optic lobes, 336.
Ordovician Period, 148, 150.
Oreamnos montanus, 413.
Organs, 22-24, 138; structure of,
22-24.
Oriental Region, 448, 451, 452.
Ornithorhynchus, 396, 432.
Orohippus, 418.
Orthogenesis, 419-425.
Orthoptera, 269, 276, 281, 3I3-3J9;
coloration, protective, 315-316;
music of, 314-315; see Blattidse;
Mantidae; Phasmidse; Protor-
thoptersu
INDEX
S53
Os calcis, 334.
Os centale, 332.
Osborn, H. F., 153, 156, 184, 416,
441.
Ostariophysi, 354-355.
Ostrich (Rheiformes), 107, 384.
Ostrocoderms, 322.
Ovalipes ocellatus, 258.
Ovis, 414.
Ovules, 77.
Owen, Professor, 107.
Oxidation, 32-34.
Oxygen, 19, 31, 32, 34.
Oxyuris, 234.
Oysters ; see Mollusca.
Ozarkian Epoch, 148.
Packard, 115, 516.
Pseciliidae, 355.
Palsearctic Region, 448, 450, 451, 452.
Palaemonetes, 259.
Palaeocampa, 265.
Palaeo-Laurentian (Archeozoic) Era,
148.
Palaeomastodon, 425, 427.
Palaeontology, 140, 147.
Palaeospondylus, 327.
Palaeozoic Era, 148, 150, 151, 221,
222, 227, 228, 322, 358, 359.
Pancreas, 30.
Panorpa, 274.
Panorpatae (Mecaptera), 274.
Paramecium, 17, 73, 80, 193, 194,
195, 196, 197-
Parapodia, 253.
Parasites, 199-206, 250; parasitism,
199-
Parthenogenesis, 74; artificial, 75.
Passeriformes, 392.
Pasteur, Louis, 479-488, 532; early
life, 479; service to mankind,
479 ; first scientific discovery, 480 ;
marriage, 482; dean of science,
482; death, 488; research and
results : antiseptic surgery, 485 ;
perpetual motion, 483; polari-
scope, 480; silkworm disease cure,
484 ; spontaneous generation, 483 ;
vaccination, anthrax and hydro-
phobia, 486-487; see also Genera-
tion.
Patmore, Coventry, 507.
Patriofelis ferox, 155.
Patten, Professor, 321.
Pauropoda, 266; Pauropus, 266.
Pavo, 388.
Pea, 42-48 ; hybridization of, 42 ;
see also Mendel, G. J. ; Mendelism.
Peacock (Pavo), 388.
Pearl, Raymond, 124.
Pearls (Nacre), 250.
Pearson, Karl, 128.
Pebrine, 483.
Peckham, Elizabeth G., 285.
Peckham, George W., 285.
Pedicellariae, 223.
Pediculus capitis, 272.
Pelmatozoa, 221.
Pelseneer, Paul A., 252.
Penguins (Sphenisciformes), 381, 382;
P. emperor, 469-470.
Pennsylvanian Period, 148, 150, 342.
Periods, geological, 148.
Peripatopsis, 263, 264.
Peripatus, 263-264; P. capensis, 264.
Perisoreus canadensis capitalis, 393.
Perissodactyla, 414.
Perloidea (Plecoptera), 269.
Permian Period, 148, 150.
Perpetual motion, theory of, 483.
Perraudin, 513.
Perrier, Edmond, 236, 239, 284, 478.
Phagocytosis, 26.
Phalanges: of foot, 334; of hand,
332-
Phasianidae, 388.
Phasmidae, 318.
Pheidole, 300, 303.
Phenacolestes mirandus, 160.
Phenomena of life, 4, 6, 13, 115; see
also Life.
Philonthus, 276.
Phoberoblatta reticulata, 151.
Phoronidea, 181.
Phosphorescence, 33, 475.
Phyla, of animals, 178-185; charts,
183, 185.
Phylogeny vs. ontology, 140.
554
INDEX
Physa, 247.
Physalia, 475.
Pigeons (Charadriiformes), 389.
Pilsbry, H. A., 115.
Piltdown man (Eoanthropus), 439.
Pinnipedia, 402.
Pisces, 182, 340, 342-357, 431, 467-
Pisiform, 332.
Pistils, 77.
Pithecanthropus erectus, 438.
Placentals, 397, 398-414; see Artio-
dactyla ; Carnivora ; Chiroptera ;
Edentata ; Insectivora ; Mystaco-
ceti ; Odontoceti ; Perissodactyla ;
Primates ; Proboscidea ; Rodentia ;
Sirenia.
Planarian, 180.
Planesticus migratorius propinquus,
394-
Plankton, 474, 477.
Plant-breeding, 60-6 1 ; green, 31;
see also Chlorophyll.
Plasm, 17, 67, 115, 124, 132.
Plasma, of blood, 25.
Plasmodium, 190, 203, 204.
Plastron, 368.
Plathemis, 270.
Platyhelminthes, 180, 229^-232; see
Cestoda; Temnocephaloidea ; Tre-
matoda ; Turbellaria.
Platyrrhine, 409.
Plecoptera (Ephemeroidea) (Per-
loidea), 269.
Pleistocene Epoch, 148, 381, 418, 427,
428, 440.
Plesiosaur, 365, 366, 369.
Pliocene Epoch, 148, 418.
Pliohippus, 418.
Polariscope, 480.
Pollen, 77.
Polychsetae, 237, 238-239, 241.
Polyembryony, 38, 409; see also
Generation.
Polyergus, 305, 306.
Polymorphism, 299.
Polyp, 40.
Polypeptids, 8.
Polyphemus moths, 289.
Polyphyletic organisms, 179.
Polypterus, 345, 346.
Polyxenus, 265.
Pomolobus, 353.
Popular Science Monthly, 163, 529.
Population, Malthus on, 499.
Porana cockerelli, 159.
Porifera, 180, 207-209, 225.
Portheus (Hypsodon), 348.
Potamochaerus porcus, 410.
Poulton, C. B., 1 14.
Powell, Major, 529.
Pratt, H. S., 242, 341.
Primates, 409-410, 416, 433.
Priority, 174.
Proboscidea, 414, 425.
Prochordata, 182, 320-326; see
Amphioxus ; Balanoglossus ; Tuni-
cata.
Procyonidae, 402.
Proellariiformes, 385.
Proglottids, 231.
Propagation ; see Generation.
Propterus, 345.
Proteins, 8; amino-acids of, 8;
complexity of, 8.
Proterozoic Eras : Early Period, 148 ;
Late Period, 148.
Proteus, 191.
Prothallium, 78.
Protophyta, 179, 186, 429.
Protoplasm, 5-7, 37-38, 137; col-
loidal nature of, 9; complexity
of atoms of, 6 ; composition of, 5 ;
continuity of life of, 17; in-
stability of atoms of, 6; retention
of identity of, 7; structure of, 6;
see also Life.
Prototheria, 396-397.
Protorthoptera, 313.
Prototracheata, 255, 263-265.
Protozoa, 13, 14, 16, 17, 73, 138,
179-180, 186-193, 235, 254, 429,
465, 477, 487, 489; vs. disease,
199-206; vs. heredity, 194-198.
Protracheata (Prototracheata), 255,
263-265.
Protura, 267-268.
Przewalski, 421.
Pseudopodia, 29, 191.
INDEX
555
Psychology, 15.
Psychozoic Era, 148.
Pterodactyl, 367.
Pteronarcys, 269.
Pterosauria, 365, 366, 367.
Pulmonates, 245.
Pupa, 279, 288.
Pure lines, in heredity, 194.
Pycnogonida, 261.
Pyramidula ralstonensis, 244.
Quadrulella, 192.
Quaternary (Cenozoic) Era, 148.
Quercus fendleri, 160; Q. ramaleyi,
160.
Rabies (hydrophobia), 487.
Raccoons ; see Procyonidae.
Radiolaria, 187, 192, 477.
Radius, 332.
Ratio, three-to-one, 45 ; see also
Mendelism.
Reality, i.
Reason, 30.
Recessives, 44, 133.
Reduction division, 66-67; see also
Generation.
Reed, Walter, 203.
Reflexes, 336.
Reform, 534.
Regeneration, 39.
Regions and Zones, Life, 454-478.
Reid, Archdall, 489.
Renilla, 39.
Repletes, 304.
Reproduction ; see Generation.
Reptilia, 182, 340, 364-372, 373,
432; see Chilonia; Crocodilia;
Dinosaurs ; Lacertilia ; Ophidia ;
Plesiosaurs.
Respiration, 31-36; adaptation to
atmosphere, 3 1 ; apparatus of,
35-36; function of, 35; oxida-
tion, 31-34.
Reticularia lycoperdon, 190.
Rhabdocoelida, 230.
Rheiformes, 384; Rhea darwinii, 107,
3.84. L
Rhinoceros, 367; see Perissodactyla.
Rhizopoda, 191-192, 197, 200.
Rhopalocera, 288.
Rhynchota (Hemiptera), 64, 276-
277.
Rhythm of life, 12; of insects, 315.
Ribs, 329.
Rickets, 20.
Ridgway, R., 395.
Riley, W. A., 279.
Ritchie, J. W., 23, 24.
Rockefeller Sanitary Commission,
235-
Rodentia, 404-407, 433.
Rodway, James, 466.
Rogers, Julia E., 252.
Roosevelt, Theodore, 466.
Ross's gull, 468.
Rotatoria, 181, 235-236, 254.
Rothmann, 165.
Rotifers; see Rotatoria.
Roundworms ; see Nemathelminthes.
Rousseau, Jean-Jacques, 281.
Roux, 488.
Sagenodus, 344.
Saint-Pierre, Bernardin de, 281.
Saliva, 30.
Saturniidae, 289, 291.
Sawflies ; see Hymenoptera.
Scale insects ; see Rhynchota.
Scaphopoda, 249.
Scapula, 330.
Schimper, 510.
Schneider, E. C., 35.
Schoetensack, Homo heidelbergensis of,
440.
Schuchert, Charles, 147, 156.
Sciurus, 407.
Sclater, P. L., 447, 448, 449, 450.
Sclerostomum, 234-235.
Scolex, 232.
Scolopendra, 266.
Scolopendrella, 266.
Scopa, 293.
Scorpion flies ; see Mecaptera (Panor
patse).
Scott, W. B., 421, 469, 471.
Scudder, S. H., 292, 319, 516.
Scutigerella, 266.
556
INDEX
Scyphocrinites, 221.
Scyphomedusae (Scyphozoa), 213,
215.
Scyphozoa (Scyphomedusae), 213,
215-
Sea, life of the, 472-478.
Sea anemones ; see Coelenterata.
Sea cucumbers ; see Synapta.
Sea squirt ; see Tunicata (Ascidians).
Sea urchins ; see Echinus.
Seabright bantam, 87.
Seals ; see Pinnipedia.
Seaweeds ; see Algae.
Secretions, 20, 30.
Sedgwick, Adam, 149.
Selection, natural, 129-136, 502-
506; Darwinian theory, 132;
determiners, 134; life-length, and
checks on, 129; Mendelism, 133;
natural vs. man's, 132; struggle
for existence, 131; survival of
fittest, 131; types, 134; varia-
tions, 135; see also Darwin;
Eugenics ; Evolution ; Genera-
tion ; Mendel ; Mendelism.
Semigigas, 64.
Semitropical Area, 461.
Septa, 251.
Serignan, festival of, 284.
Serpulidae, 239.
Serum, 26, 30.
Sex, 77-88 ; characters, primary and
secondary, 78; conjugation, 80 ;
determinators of, 81, 86; dimor-
phism, 312; gynandromorphs, 85 ;
hermaphrodites, 78 ; limitation of,
84; linkage, 84; monstrosities,
38; selection, 129-136, 502-506;
twins, 87; two sexes, 77; varia-
tions in life by, 8 1 ; see also
Selection.
Shaler, N. S., 516.
Sharp, D., 279.
Siamese twins, 38.
Silkworm disease and cure, 484.
Silurian Period, 148, 150, 253.
Silvestri, 268.
Simiidae, 410; Simia satyrus, 410.
Sinus venosus, 338.
Siphonaptera, 278.
Siphunculata, 272.
Sipunculoidea, 181.
Siren, 360.
Sirenia, 414.
Skeleton (Endoskeleton), of verte-
bra ta, 328.
Skull, 329-330.
Smith, Frank,. 242.
Smith, J. B., 279.
Snails (Gastropoda), 78, 142.
Snakes (Ophidia), 364, 372.
Sociology vs. biology, 530-534.
Solenodon, 399.
Sonoran Areas, 459, 460, 461.
Soothsayers ; see Mantidae.
Spallanzani, 483.
Sparrows ; see Passeriformes.
Specialization, 99.
Species, 170.
Species plantarum, 174.
Spermatogenesis, 67.
Spermatocyte, 66, 67.
Spermatozoon, 66.
Sphargis, 368.
Sphenisciformes, 381.
Sphenodon (Tuatera), 365, 452.
Spiders ; see Arachnida.
Spillman, W. J., 198.
Spilochalcis mariae, 275.
Spinal cord, 329, 334.
Spiracles, 36.
Spirorbis, 239.
Spizella monticola ochracea, 395.
Sponges (Porifera), 180, 207-209,
225.
Spongin, 209.
Spontaneous generation, 483 ; see
also Generation.
Sporangium, 189, 190.
Sporophore, 190.
Sporozoa, 190-191, 201, 202.
Sport, 119.
Springtails ; see Collembola.
Spruce, Richard, 466.
Spumaria, 189.
Stamens, 77.
Starfish (Asteroidea), 218, 222
Statoliths, 214, 215.
INDEX
557
Stein, W., 381.
Stejneger, L., 372.
Stegocephalia, 359.
Stegomyia, 203.
Sterility, 87.
Sternum, 329.
Stevens, 102.
Stigma, of bees, 298.
Stimulus, 10.
Stobseus, 166.
Stockard, Charles R., 121, 123.
Stomata, 31.
Stomias boa, 478.
Stone flies ; see Perloidea.
Storks ; see Ciconiiformes.
Strepsiptera, 276.
Strongylus, 234.
Struthioniformes, 383.
Styela, 322.
Stylocephalus, 192.
Subspecies, 119.
Substance ; see Matter.
Suctoria, 193.
Sudburian Period, 148.
Suidae, 410.
Sumner, 119.
Sun animalcules (Heliozoa), 192.
Sundew (Drosera), n.
Sunflower, red (Helianthus), 51-61;
as typical of Mendelian phenom-
ena, 51-61; collarette of, 59; see
also Mendel; Mendelism.
Susceptibility, 490.
Sweat, 30.
Symbiosis, 94.
Symphyla, 266.
Synapsis, 69, 71, 72.
Synapta, 218, 225.
Synonyms vs. homonyms, 174.
Synthetic amino-acids, 8.
Systema Naturee, 172.
Tachyglossus (Echidna), 396.
Tsenia, 231; T. solium, 232.
Tapeworms ; see Cestoda.
Tardigrada, 254.
Tarsus, 332.
Tayassuidae, 410.
Taylor, J. W., 115.
Teleostomi, 345; Teleostei, 349-357.
Temnocephaloidea, 229.
Temperature vs. life, 455.
Tennesseian Epoch, 148.
Termes flavipes, 271.
Termites ; see Isoptera.
Tertiary (Cenozoic) Era, 140, 148,
154-
Testudo vicina, 368.
Tetrabelodon (Trilophodon), 425,
426, 427.
Thaumatostomias atrox, 478.
Thompson, 373.
Thrassetus harpyia, 388.
Threadworms ; see Nemathelminthes.
Three-to-one ratio, 45; see also
Mendelism.
Thrips ; see Thysanoptera.
Thysanoptera, 273.
Thysanura, 268-269, 286.
Tibia, 332.
Tibicina septendecim, 277.
Ticks, disease carriers, 206.
Tierra caliente, 447.
Tillandsias, 465.
Tipula, 279; T. maclurei, 162.
Tissues, 22-30, 94, 138, 186; blood,
25; connective, 24; function of,
25, 27, 28; muscle, 27; nerve, 28;
skin, 23 ; structure of, 22-24.
Tortoise ; see Chilonia.
Trachea, 23, 36.
Transition Life Zone, 459.
Trematoda, 229, 230-231.
Triassic Period, 148, 151.
Trichia, 189.
Trichinella, 235.
Trichinosis, 235.
Trichoptera, 273, 289.
Trigona, 297.
Trilobita, 257.
Trilophodon (Tetrabelodon), 425,
426, 427.
Trimorphism, 299.
Trochelminthes, 181, 235.
Tropical Life Zone, 462, 463-466.
Truth, 2.
Trypanosoma, 189, 200, 204, 206;
T. brucei, 205 ; T. gambiense, 205.
558
INDEX
Tschermak, 49.
Tsetse fly (Glossina), 161, 204, 279.
Tuatera (Sphenodon), 365, 452.
Tumor, 25.
Tundra, 469.
Tunicata (Ascidians), 321, 322, 323.
Tupaia, 433.
Turbellaria, 229-230, 233.
Turtle ; see Chilonia.
Twins, 38, 87; identical, 38;
Siamese, 38.
Types, 171.
Typhlomolge, 361.
Ulna, 332.
Ungulates, 433.
Universe, the physical, 1-4, 530,
535^; ^energy, 3-4; life, 2-4;
limitations of mind, I ; matter,
3; nature, laws of, i, 48, 535;
phenomena, 4 ; reality, I ; truth,
2 ; see also Matter.
Urodela, 360-361.
Ursidse, 402.
Vaccination : for anthrax, 486 ; for
hydrophobia, 487.
Vallery-Radot, Rene, 488.
Van Dyck (Vandyke), Anton, 52.
Variation, 72, 80, 115-119, 134;
combinations, 117; environment,
118; forms of, 118; kinds of,
115; universality of, 115.
Variety, botanical and zoological,
172.
Venetz,-si3.
Ventricles, 338, 340.
Vermes, 181, 430; see Annelida;
Nemathelminthes ; Nemertina ;
Platyhelminthes ; Rotatoria.
Vermilion (coloring), 309.
Verrill, 516.
Vertebrae, 329; amphiccelus v., 329.
Vertebrata, 86, 178, 182, 320, 321,
328-341, 432; evolution of, 340;
structure of, 328-341; see Am-
phibia ; Birds ; Cyclostomes ;
Fishes ; Mammalia ; Reptilia.
Vestigial structures, 139.
Vilmorin wheat, 196.
Virus, 200.
Viverridse, 401.
Vries, Hugo de, 49, 64, 143.
Walcott, Charles D., 149, 156.
Walden, B.H., 319.
Waldheimia, 227.
Wallace, Alfred Russel, no, 136,
290, 292, 447, 448, 449, 451, 453,
466, 471, 530.
Wapiti, 411.
Ward, 235, 242.
Warren, 393.
Wasps ; see Hymenoptera.
Water, 31.
Water bear (Tardigrada), 254.
Waverlian Epoch, 148.
Wax, 309.
Weed, C. M., 395.
Weismann, 17, 132.
Whale, 369, 467-
Wheeler, W. M., 303, 307.
Whipple, 235, 242.
Whittier, 518.
Wilson, Edward A., 470.
Wilson, E. B, 64.
Woodruff, 1 6.
Woodward, A. Smith, 439.
Work, 32.
Worms ; see Vermes.
Xantus, John, 525.
Xenia, 68.
Xenorhynchus asiaticus, 385.
Xiphosura, 260; X. polyphemus, 260.
Xylocopa, 296.
Yeasts, 31, 483.
Yucca, 445.
Zaglossus, 396-397.
Zoaria, 226.
Zones, Life, 454-478.
Zooecium, 226.
Zoophytes, 40, 95, 21 1.
Zostera, 473.
Zygote, 38, 55, 58, 67, 69, 82, 83, 85,
116, 126.
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