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EVOLUTION OF LIFE.
" /f7i
HENRY C. CHAPMAN, M.D.,
MEMBER OF THE ACADEMY OF NATURAL SCIENCES, PHILADELPHIA.
“ Full fathom five thy father lies ;
Of his bones are coral made ;
Those are pearls that were his eyes ;
Nothing of him that doth fade
But doth suffer a sea-change
Into something rich and strange.”
Shakspeare.
“If we were capable of following the progress of increase of the number of the
parts of the most perfect animal, as they first formed in succession, from the very
first to its state of full perfection, we should probably be able to compare it with some
one of the incomplete animals themselves, of every order of animals in the creation,
being at no stage different from some of the inferior orders.”
John Hunter.
PHILADELPHIA:
J. B. LIPPI NCOTT & CO.
1 873.
Entered according to Act of Congress, in the year 1872, by
J. B. Ljl PPI N COTT & CO.,
In the Office of the Librarian of Congress at Washington.
WELLCOME INSTITUTE
LIBRARY
Coll.
we'MOmec
Call
No.
mm:
1 mi
OAiU
... ^
TO
MRS. C. B. P.,
AS A
VERY SMALL ACKNOWLEDGMENT
OF THE
INTEREST EVINCED AND ENCOURAGEMENT EXTENDED
IN THE
COMPLETION OF THIS ESSAY.
HENRY C. CHAPMAN.
(in)
PREFACE.
Since 1858, the year in which appeared Mr. Darwin’s
famous book, the literary as well as the scientific world has
been deluged with works — great and small — on the subject
of the Origin of Species. Notwithstanding, however, the
great number of works that have been published in Eng-
land, Germany, France, and Italy treating of the Develop-
ment Theory, the Origin of Man, etc., there appears to be
still a great deal of misunderstanding in reference to these
subjects. It did not seem, therefore, superfluous to bring
together a condensed view of the evidences for the theory
that the animal and vegetal worlds have been very grad-
ually developed or evolved, as distinguished from the
hypothesis of their sudden special creation. We have
endeavored to place before the reader, in as popular a
manner as possible, the most important generalizations in
reference to the structure of plants and animals, their
petrified remains, and mode of development, and to point
out how the theory of the Evolution of Life follows from
the acts of Anatomy, Geology, and Embryology. While
we have little new to offer to those who are familiar with
the works of Lamarck, Darwin, Wallace, Spencer, Owen,
Huxley, Hooker, Lyell, Haeckel, Gegenbaur, Buchner,
(v)
VI
PREFA CE.
Vogt, Virchow, Moleschott, Muller, Rolle, Schleicher,
Bleek, Meigs, Gliddon, Leidy, Cope, Gray, etc., to the
medical and literary world generally, however, whose
acquaintance with the writings of the distinguished savans
just mentioned is necessarily superficial from the nature
of their pursuits, we offer a brief but, we hope, a sufficiently
detailed account of a subject which is not surpassed in
interest by any other. We take this opportunity of thank-
ing Prof. Hyrtl, Dr. Friedlowsky, Dr. Klein, of Vienna,
Prof. Owen, Mr. Flower, of London, and Prof. Gervais, of
Paris, for their kindness in furnishing many facilities for
study, as also of acknowledging our indebtedness to Profs.
Leidy and Aitken Meigs for their many favors and sug-
gestions, and to Dr. Nolan for materially assisting us in
seeing this essay through the press.
Henry C. Chapman.
Paris, June 21, 1872.
C O N T E N T S.
PACK
Introduction 9
Zoology 19
Botany 78
Geology 106
Embryology 125
Natural Selection 141
Anthropology 162
(vii)
INTRODUCTION.
By the Evolution of Life we mean the slow and gradual
development of life as distinguished from its special and
sudden creation ; that plants and animals are the modified
descendants of pre-existing organisms, not the unchanged
posterity of similar forms of life originally specially cre-
ated. Let us illustrate our meaning by considering the
origin of a common animal like the Horse. According to
the creation hypothesis, all horses are the descendants of a
pair of horses, originally, specially created. Supposing the
Evolution theory, however, to be true, the Horse is the
modified descendant of an extinct species of Horse, the
Hipparion. Preceding the Hipparion there lived the An-
chitherium, whose organization bears the same relation to
the Hipparion that the Hipparion's does to that of the
Horse; while in a still earlier period we find in the
Paleotherium the ancestor of the Anchitherium. But the
Rhinoceros and the Tapir are also nearly related to the
Paleotherium. We see, therefore, why all naturalists are
agreed in regarding the Horse, Rhinoceros, and Tapir as the
representatives of one group. Lor, if these animals are the
posterity of a common ancestor, it is natural that their
organization should have much in common. Through
extinct forms, like the Xiphodon and Anthracotherium, the
Ruminating animals, the Pig, and the Hippopotamus, are
linked with the Anoplotherium ; while glancing at Tree
VII. we see that the Paleotherium and Anoplotherium are
( 9 )
10
EVOLUTION OF LIFE.
i tgai dec! as the descendants of a common stock, represented
by extinct forms, like Coryphodon and Lophiodon. Basing
the investigation on the facts of Anatomy, Embryology, and
Geology, the genealogy of the animal and vegetal kingdoms
has, in this manner, been more or less made out, the indefi-
nitely remote ancestors of all plant and animal life being
represented by the Monera, structureless, infinitely small,
jelly-like beings, belonging neither to the animal nor to the
vegetal kingdom. This view of the gradual development
of existing forms of life from pre-existing ones is in har-
mony with the conclusions of other sciences. Most eth-
nologists are agreed that the different races of men have
descended from a common stock, notwithstanding- the
great differences exhibited in color, shape of the head,
and character of the hair. Philologists derive the various
languages from one of three or four roots. The history
of Art offers us interesting illustrations of the doctrine of
Evolution. Thus, the present perfection of music has been
attained only through very gradual additions from time to
time. Modern orchestration is so complicated that one
would hardly believe that it could have been developed
out of the simple jingle of barbarians. Astronomers think
it highly probable that our solar system was once a chaotic
mass, and that from this the planets were thrown off, the
central body becoming later the Sun. This theory, which is
commonly known as the Nebular Hypothesis of La Place,
naturally suggests the name of Kant, the famous philoso-
pher of Konigsberg, who first distinctly enunciated the view
of the gradual development of the solar system, and the
doctrine of Evolution in general. But as the differentiation
of the simple into the complex, of the homogeneous into
the heterogeneous, of which the development of race and
language is an example, has been fully discussed by Mr.
Herbert Spencer in his different works, we therefore pass
on to the consideration of the objection, that while the
INTR ODUC TION.
I I
origin of races, of languages, of the stars, etc. is a legitimate
object of study, the origin of plants and animals is an in-
quiry of an entirely different nature, — a subject about which
man can learn nothing. Those who are continually referring
to the mysteriousness of Life as an objection to its study,
seem to forget that the ultimate causes of all other phenom-
ena, such as the falling of an apple, the combining of elements,
the crystallization of a salt, etc., are equally mysterious.
The forces by which these phenomena are brought about
are studied in their effects; and the laws according to which
these effects are produced belong to Astronomy, Chemistry,
Crystallography. But of the cause or essence of gravitation
we know nothing. We can only say that bodies attract one
another according to a certain law. Equally unknown is the
ultimate cause of crystallization. We can only say that in
saline solutions, under favorable conditions, according to
law, geometrical forms are produced. Compare now the
growth of a crystal with that of a plant or an animal. If a
seed be sown and it attract certain elements from the soil,
a definite form, a plant, is produced; in the same way the
chick results from the embryo attracting the material of its
future body from the yelk. The laws governing the forces
by which these effects are brought about, the phenomena
of the growth of a plant or of an animal, are as legitimate
objects of study as the growth of a crystal. The nature of
the inquiry is the same : the study of the growth of a crystal
differing from that of a plant or an animal not in kind but
only in degree; the investigation being in each case the re-
distribution of matter, for there is nothing in the crystal that
did not pre-exist in the saline solution, nothing in the plant
that was not derived from the seed or the soil, nothing' in
the chicken that did not pre-exist in the egg or in the air.
The ultimate cause of the so-called Vital Force is as un-
knowable as the cause of all other kinds of Force. The
laws, however, by which the effects of the so-called Vital
12
EVOLUTION OF LIFE.
Force are brought about, will be worked out exactly as the
laws of other Forces have been. And as the difficulties ex-
perienced in the study of the so-called vital phenomena are
due to their complexity as compared with the simplicity of
the so-called physical ones, it is quite natural that the organic
sciences should be less advanced than the inorganic.
These terms, however, Organic and Inorganic, Vital and
Physical, Animate and Inanimate, Living and Dead, are
very unphilosophical, since their use implies an entirely
false view of Nature. The classification of objects into
Animal, Vegetal, and Mineral, is a good arrangement for
study ; but it is a-purely artificial one, no such distinction
existing in Nature. The usual tests for distinguishing
animals from plants, plants from minerals, have been ren-
dered perfectly worthless by the discoveries of late years.
Living beings like the Monera, representatives of a king-
dom intermediate between the animal and the vegetal, are
so structureless, so absolutely homogeneous, that crystals
are complex bodies as compared with them. Products like
sugar and alcohol, supposed at one time to be purely or-
ganic in their origin, to be produced only by the so-called
Vital Force, are now made in laboratories by the combina-
tion of their inorganic elements. There are no substances
in t'he Organic world whose elements are not resolvable into
those of the Inorganic, no Vital Forces which are not convert-
ible into Physical ones. In a word, no one can show where
the Inorganic world ends and the Organic begins, the transi-
tion being so gradual. The objection is therefore ground-
less that the study of life is entirely different from that of
all other phenomena, and that one can learn little about it.
On the contrary, we have every reason to expect that in
time we shall have a Science of Life, or Biology, a Science
which will bear the same relation to Zoology and Botany
that History does to mere Chronicle; that will tell us not
only what plants and animals live and have lived, but why
INTRODUCTION.
13
some died out and others survived; whether these sur-
vivors were modified, and, if so, by what means; why
certain plants and animals are found in places not best
suited to their structure ; why similar forms of life are not
always found under similar physical conditions, and why
dissimilar plants and animals are often found under similar
physical conditions ; why animals have organs of no use
to them ; why some animals are protected, why others
are not, etc. etc. We consider that these questions are
answered by the theory of the Evolution of Life, and that
this theory may be regarded as the fundamental truth of
Biology. We propose in this essay to bring together, in as
popular a manner as possible, some of the evidence in favor
of this theory, endeavoring to show that the different
plants and animals are linked together by transitional
forms ; that there has been a progress from the simple,
lowly organized, to the highly complex forms of life ; that
the transitional stages through which a plant or an animal
passes in the development from its primitive to its adult
condition are permanently retained in the lower forms of
life ; that the development of the higher forms of life from
the lower has been brought about by Natural Selection ;
and that Man has descended from a lower extinct form, of
which the Gorilla and the Chimpanzee are the nearest
living representatives.
Before discussing these different subjects, as there seems
to be still some misunderstanding in reference to the views
of the predecessors of Mr. Darwin, the most distinguished
of the advocates of the Evolution of Life, it may be perhaps
not superfluous to glance at the literature of the subject.
Here and there among the writings of the ancients, one
meets with passages, and even works, like those of Lucre-
tius, from which it is evident that at different times some
doctrine like that of the Evolution of Life was held by the
thinkers of antiquity. Passing by the speculations of
H
EVOLUTION OF LIFE.
De Mail let, the first attempt in modern times to bring
together the evidence in favor of the Evolution of Life,
with the causes sufficient to produce it, is to be found in
the writings of Lamarck, — the Philosophical Zoology (1809},
and the Plistory of Animals without Vertebrae (1815).
Lamarck was Professor of Zoology at the Garden of Plants,
in Paris, and, far from being a mere dreamer, was an emi-
nent naturalist, as every one admits, whatever may be
thought of his speculations. Many of these speculations,
however, are regarded by distinguished living Biologists
as profound truths, such as, that “there is no distinct vital
principle,” that “ life is only a physical phenomenon,” that
“ the nervous system produces ideas, and all the acts of the
intelligence,” etc.
In the works just alluded to, Lamarck, basing his views
on the structure of plants and animals, and their petrified
remains, develops the theory of there having been a pro-
gress in the organic world from the simpler forms of life
to the higher; that all organisms in the lapse of ages had
descended from pre-existing ones. As causes of the trans-
mutation of species, Lamarck held that the force of the
will, as exhibited in the use and disuse of organs, exercised
great influence in modifying the structure of animals ; he
attached also great importance to the facts of inheritance.
While it is admitted that there is a great deal in the writings
of Lamarck that cannot be maintained, still, he must be
considered as the first who attempted to develop in detail
the theory of the Evolution of Life, and one of its most
distinguished advocates. Noticing that Lamarck held that
the Monkey descent of Man, previously advocated by Mon-
boddo, was a necessary consequence of his theory, we pass
on to Geoffroy St.-Hilaire, the distinguished and constant
opponent of Cuvier in the discussions on the Origin of
Species at the Garden of Plants. Although for a long time
St.-Hilaire had thought as Lamarck, it was not till 1828
INTRODUCTION.
15
that in his essay “ On the Principle of the Unity of Organic
Composition” he openly defended the doctrine of the trans-
mutation of species. While in France Lamarck and St.-
Hilaire were studying the transmutation of species, Goethe
and Oken were investigating the same subject in Germany.
Goethe is famous as a poet, but is not so well known as
a man of science. He, however, made the capital dis-
covery of the intermaxillary bone in Man, which gives
him rank as an anatomist, while his theory of the “ Meta-
morphosis of Plants” has always been regarded as a most
important contribution to philosophical Botany. In this
work on Plants, Goethe develops the view of the different
parts of the flower being modified leaves. This theory,
which is a beautiful illustration of Evolution, had been pre-
viously promulgated by Wolff, but had fallen into perfect
oblivion. Goethe was always pointing out the “ unity of
Nature,” and advocating the doctrine of Development, and
must be considered one of the most distinguished of the
German Biologists. Oken was one of the most remarkable
men Germany has ever seen, not only for the extent of his
knowledge, but for the originality of his views. Although
his ideas are very often mystified by obscure language,
nevertheless it is certain that he had a clear perception
of some of the most important modern truths, such as
the mechanical theory of Heat, the doctrine of Cells, etc.
His idea of a “primordial mucosity” as the basis of life is
veiy much like that of the “protoplasmic” doctrine of the
present day. However this may be, there is no doubt that
Oken was a firm believer in the Development theory of
Lamarck.
Notwithstanding that the theory of the Transmutation
of Species was defended by men of such ability as Lamarck,
St.-Hilaire, Goethe, and Oken, it fell entirely into disrepute
after 1830, the year of the famous discussion between
Cuvier and St.-Hilaire at the Academy of Sciences. From
i6
EVOLUTION OF LIFE.
that time the question of the origin of species was con-
sidered transcendental, not a subject for inquiry. It seems
proper now to mention the influence of the “ Principles of
Geology,” by Sir Charles Lyell, published in 1832. The
doctrine of Catastrophes, or the supposition that at different
times all life had been destroyed by the convulsions through
which the earth had passed, and that a new life had been
cieated from time to time, was supported by the high
authority of Cuvier. Lyell, in the work just mentioned,
put forward the view that these catastrophes had been only
local, and that they had been brought about by the same
forces that are now modifying the earth; that life has
always existed, — new forms appearing, old forms passing
away; that disturbances have taken place at different
times in different places, just as at present we have earth-
quakes, volcanic eruptions, etc. This view is at present
accepted by most Geologists, very few believing any longer
in the Cuvierian theory of the “ Revolutions of the Globe.”
The effect of the “ Principles of Geology” on the progress
of the Development theory was very great, since one of the
objections to it, of life having been often extinct all over
the globe, was therein shown to be groundless. Although
the doctrine of Development was opposed by naturalists,
nevertheless from time to time it was advocated, as in 1837
by Dean Herbert, in 1844 by the anonymous author of the
Vestiges of Creation, in 1846 by D’Omalius d’Halloy, in
1852 by Naudin, in 1855 by the Rev. Baden Powell and by
Buchner, and from 1852 to 1858 by Mr. Plerbert Spencer.
Remembering the vast discoveries that had been made
since the days of Lamarck in Zoology, Botany, Geology,
that the study of Embryology had been raised to a science,
that of the Geographical Distribution of plants and animals
more was known, etc., let us now call attention to the famous
book on the Origin of Species, by Mr. Darwin. The two
great merits of this work are its bringing together in a con-
INTRODUCTION.
17
densecLform the evidences in favor of the Evolution of Life,
and its offering Natural Selection as a cause of this Evolution.
We will not dwell now on Natural Selection, as we endeavor
to explain it in a chapter devoted to that subject. It seems
proper, however, to mention that the discovery of Natural
Selection was made independently by Mr. Wallace, who,
having spent seven years in the Malay Archipelago, sent a
paper to London containing his views on the Origin of
Species. Following the advice of mutual friends, Mr.
Darwin brought forward an abstract of his views, and the
two papers appeared simultaneously in the publications
of the Linnsean Society. Since the publication of the
Origin of Species, many works have appeared in which this
subject is discussed more or less in detail, among which
may be mentioned the later ones of Messrs. Darwin and
Wallace; the General Morphology and Natural History of
Creation, by Prof. Haeckel ; the Principles of Biology, by
Mr. Herbert Spencer; the various works of Dr. Buchner;
the Origin of Species, etc., by Prof. Huxley; the Introduc-
tion to the Flora of Tasmania, by Sir William Hooker;
the Comparative Anatomy of Prof. Gegenbauer ; the Crus-
tacea of Fritz Muller; the different papers by Prof. Cope,
etc. etc.
Hoping now to have made clear the general object of
our essay, to have shown how gradual has been the devel-
opment of the theory of the Evolution of Life, and having
merely noticed some of the important literature on the
subject, we pass on to the consideration of the Evidences,
the Causes, and the Consequences of this Evolution.
.
B - .
' •
.
.
ZOOLOGY.
4
One cannot glance at the opening pages of any work
on Zoology without being struck with the difficulty that
naturalists experience in classifying the objects of their
study. This difficulty arises from the fact of there being
many animals whose organization presents characters which
combine the peculiarities of different families or orders.
The Flying Lemur (Galeopithecus volans) of the East Indies
was for a long time considered to be a bat ; modern anato-
mists place it among the monkeys, and yet, according to
some authorities, the grounds for its determination in the one
case are as good as in the other. If the Galeopithecus, the
monkeys and the bats originally appeared as we find them
now, why should there be such a difficulty in determining
their place in the Animal Kingdom ? If, however, there has
been an order of Galeopitheci, of which the present species
are the only surviving representatives, and we regard these
extinct forms as the common ancestors of the bats and the
monkeys, we have an explanation of the peculiarities which
are shared by these three orders:
Bats. Galeopithecus. Monkeys.
Ancestor.
If the theory of the gradual transformation of animals be
true, it is quite natural that we should find transitional
( i9 )
20
EVOLUTION OF LIFE.
forms, such as the Flying Lemur. There are many similar
examples : the Aye-Aye (Cheiromys) has teeth like a rat,
while in other respects it is a monkey. The Duck-bill
Platypus of Australia (Ornithorhynchus) combines the
organization of lizard in its breast-bone, crocodile in its
ribs, and bird in the skull and digestive apparatus, and yet
is a four-footed animal.
KINGDOM INTERMEDIATE BETWEEN ANIMALS AND PLANTS.
In modern times, through the assistance of the micro-
scope, many minute beings have been discovered which
have been successively classified as plants or animals,
according to the botanical or zoological tendencies of their
describers. As these microscopic beings present the life of
both plant and animal at different stages of their existence,
it is quite impossible to say to which kingdom they belong.
Many naturalists are, therefore, agreed to consider them as
a something apart, an intermediate original kingdom, out
of which the plant and the animal worlds have been evolved.
If life has been gradually developed, and there has-been a
progress from beings of low organization to higher, it is
natural that such a kingdom should exist, partaking in
its nature of animal and plant characters. The origin of
life is to be sought, therefore, in this main root, of which
animals and plants are the rising diverging branches. The
beings of this animal-plant kingdom* which still exist are
only the descendants of a larger kingdom long since extinct,
or perhaps some of the most simple are still formed through
spontaneous generation.
* The limits of this essay permit the noticing of only a few of the orders
of the intermediate kingdom.
amoebae
peridnium stages of gregarina
ZOOLOGY.
21
MONERA.
The simplest forms of life known are the Monera (Figs.
I, 2, 3), which may be defined as living jelly, — formless,
structureless, in every sense of the word. Their move-
ments are restricted to a gliding or crawling, a drawing in
or putting out of their jelly-like body ; their reproduction
is a simple splitting of their body into two halves, each half
becoming a new Monas. Such a living slime is seen in
Protogenes. The first sign of structure we xneet with
in this kind of being is where a wall has been exuded
inclosing the jelly-like body, as in Protomonas, or as in
Amoeba (Figs. 4, 5, 6, 7), where the slime has aggregated
in the middle, forming a nucleus. These two different
conditions, a nucleated slime and a walled slime, are com-
bined in Arcella, these last being undistinguishable from
the young of the simplest water-plants (Algae) and the un-
developed forms of certain jelly-fish (Siphonophorae). In
the springtime the ponds are often covered with a green
matter, which, when examined with a microscope, is found
to consist of Euglena (Fig. 8), minute flask-shaped bodies
with little tails ; when these bodies are covered with
hairs (cilia) they are known as Peridnium. They, like the
Arcella, cannot be distinguished from the young of the
simplest plants and animalcula (Infusoria). What conclu-
sions can be drawn from the existence of Monera, Amoebae,
Euglena ? How have they originated ? Either they have
come from pre-existing forms, or have arisen through
spontaneous generation. Where have the pre-existing
forms come from, is immediately suggested by the first
answer, which only waives the question, and is therefore no
answer at all. It will not suffice to say that they were
created; as well might an astronomer explain the motion
of the moon around the earth by saying it was created
so to move. What is meant by spontaneous generation ?
22
EVOLUTION OF LIFE.
Let. us illustrate by the example of the formation of a
crystal out of a simple solution. A nucleus first appears,
then increment after increment is added, according to
laws, until the crystal is formed. The case of the origin
of a Monad is a parallel one. We have a solution ; in
this solution appears the Monad. There is no more
necessity for the pre-existence of a Monad in the solution
than that there should have been a pre-existing parent
crystal. In both solutions exist the elements of which
the Monad and Crystal are formed ; the laws according
to which they are formed are as susceptible of study in
the one case as in the other. Theoretically, therefore, there
is no objection to the idea of Spontaneous Generation, the
laws of which must be investigated as any other mechanical
problem has been ; the problem being a question of the
redistribution of matter. In fact, according to the experi-
ments of Pouchet, Pennetier, Bastian, Wyman, and others,
Vibrios and Bacteria do appear in solutions where there
was not previously a trace of these minute beings.
Want of space prevents us from discussing this question
in detail. We can only say that at present the evidence
seems to us in favor of the view that Spontaneous Genera-
tion takes place at the present day under favorable condi-
tions. We turn now to the consideration of living Monera
and Amoebae. Whatever their present or remote origin may
have been, an Amceba is a Monas with a nucleus. The
Amcebae probably came originally from Monera, if they are
not now so produced, and in some cases colonize them-
selves, forming the Sponge, — this view being suggested by
the young of the Sponges, which cannot be distinguished
from Amcebae, — or the Amcebae gaining tails and hairs, like
the Euglena, gave rise to the Animalcula or Infusoria.
But as certain Amcebae and Euglena cannot be distinguished
from the spores or young of the simplest plants, the origin
of the vegetal world must be sought also in these minute
ZOOLOGY.
23
beings. If, now, Spontaneous Generation does not take
place, the Monera and Amoebae of the present day, and the
other orders of the Intermediate Kingdom also, are the
posterity of the long dead original forms, the ancestors of
the three kingdoms, — the animal, the vegetal, and the
intermediate world. (See Tree I., page 24.)
SPONGES.
The sponge of every-day use (Figs. 11, 12) is composed
of a horny, fibrous material, produced by a colony of
Amoebae, and if a section of the fresh-water Sponge
(Spongilla) be made, a glance will explain by what means
the currents of water are produced, which can be seen
under the microscope. The outer layer is composed of a
number of Amoebae, with little openings, through which
the water enters the cavity between the outer and inner
layers, this inner layer being also composed of Amoebae,
in the. deep substance of which are chambers lined with
fine hairs (cilia), which, working in the same direction, force
the water through them into a common outlet; in this
manner strong currents of water pass in and out of the
sponge, making a little whirlpool, into which minute par-
ticles of matter are dragged.
Sponges are found attached to all kinds of rocks, and
often to shells, both in the sea and on the beach, and are of
two kinds, soft and hard, of which the soft are probably the
ancestors of the hard. 'The Halisarca, or Slimy Sponge, is
found attached to the leathery sea-weed, and is composed
of slimy Amceba-like bodies, in which the canal system
just described is only imperfectly developed. From this
kind were derived the Gummy Sponges, so called from their
gumlike consistency; their canal system foreshadow-s the
homologous structure in tire Jelly-fish. Sponges like the
Halisarca were probably the ancestors of the first kind of
Animal. Intermediate. Vegetal,
24
EVOLUTION OF LIFE
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ZOOLOGY,
25
l
hard sponge, — the horny kind (common bathing sponge), —
which, when alive, has the interstices filled with these
Amoeba-like bodies. Some of the descendants of the Horny
Sponges were metamorphosed into the flinty kind, to which
our fresh-water sponge belongs, and the Venus’s flower-
basket (Euplectella), whose framework rivals in delicacy
the most beautiful lace. From the flinty kind were derived
most likely the Pitcher Sponges, in which the framework
takes the form of a goblet or pitcher. These are often
beautifully preserved in a fossil state (Ventriculites, Guet-
tardia); they are nearly allied in their structure to Corals
and Anemones. Still closer to the Corals are the calcareous
sponges in their affinities. The natural history of Sponges,
to those to whom it is known best, is full of evidences in
favor of the theory of Evolution.
TREE II.
Actinozoa.
Hydrozoa.
Jelly-Fish.
Anemones. Corals.
Calcareous. Pitcher.
Gummy.
Flinty.
Homy.
Slimy.
Hard Sponges.
Soft Sponges.
Original Sponge.
Amoeba.
Monas.
28
EVOLUTION OF LIFE.
upside down, and swims off, stomach hanging downward
from an umbrella or bell-shaped body; we would then have
a jelly-fish.
HYDROZOA.
Every one who has visited the sea-shore must have had
his attention called to the jelly-fishes (Fig. 20), as they
floated along by means of the pulsations of their disc-bear-
ing bodies, the animal looking somewhat like an umbrella,
and he remembers well the sensations suffered while bath-
ing when his skin came in contact with the long streamers
floating about, which are so characteristic of these organ-
isms. The stinging is due to a poison which is contained
in vesicles situated in the skin, often millions in number.
In the beautiful Blue Physalia, known to sailors as the
Portuguese man-of-war, this poison is so powerful that it
has been known to cause death. The jelly-fishes and Anem-
ones alike possess these poison-cells; but the Sponges,
although having the rudimentary canal system, are devoid
of the stinging structures. The most simple example of
the Hydrozoa is our common Green Hydra (Fig. 18), so
called from the fact that when cut in pieces each piece
becomes a new individual. It looks to the naked eye like
a piece of green silk thread. When magnified, it is seen
to be a simple tube, the digestive cavity and general cavity
of the tube being the same; its mouth is surrounded by a
circle of arms or tentacles, by means of which it seizes its
prey, paralyzing or destroying it by the poison just spoken
of. The importance of the Hydra, as part of the evidence
for the evolution of life, maybe seen in the development of
the so-called Hydroid jelly-fishes, such as the Campanularia
and Sertularia (Fig. 19), which look like little trees covered
with flowers. The branches of these tree-like beings are
little tubes, in which the flowers (Hydroid polyps) live ; the
tubes are all connected, so the colony has a common
ZOOLOGY.
2 9
digestive cavity. Such beings as the Campanula produce,
through budding, beautiful little jelly-fishes, which swim
freely about. They in their turn produce eggs, from which
spring the stationary colonies of Hydrae. There is an alter-
nate generation, Campanulariae producing jelly-fish, jelly-
fish producing Campanulariae. We see the Hydra living
as an independent organism — the Hydra of our fresh-water
ponds — and in a transitory stage, as the Campanula. Some-
times a colony of these Hydroids form a freely swimming
organism, as the Portuguese man-of-war. The Ctenophorae,
or comb-bearing jelly-fishes, pure as crystal and transparent
as glass, are characterized by their organs of motion, which
are eight delicate combs, by the graceful movement of
which the Beroes and Cydippe glide through the sea.
They are intermediate in some respects between the Anem-
ones and common jelly-fish (Aurelia). By glancing at
Tree II. we see the probable origin of the Anemones, Corals,
and Jelly-fish in the Sponges, the Anemones and Corals
coming from the hard sponges, the fossil forms of which,
like Ventriculites and Guettardia (Figs. 13, 17), closely re-
semble in the arrangement of their chambers those of the
Anemone and Coral. By comparing the transverse section
of a sponge (Fig. 22) with that of the jelly-fish (Fig. 21), we
see that the canals of the sponge are the same as those of
the jelly-fish, though more simple in their arrangement.
Though objections have been, and will be, raised to this
view of the origin of the Actinozoa and Hydrozoa, that they
have so descended from stationary beings the Anemones
and Hydroid polyps are the living proofs. That these
stationary ancestors were sponges, or beings allied to them,
is rendered very probable by the harmonious evidences of
the structure, development, and fossil remains of the entire
group.
We will now leave the Coelenterata, considered as a
distinct division of the animal kingdom on account of its
30
EVOLUTION OF LIFE.
simple and characteristic structure, and turn to the other
descendants of Amoebae, as seen in Tree I.
GREGARINAE.
In the alimentary canal of the earth-worm, of cockroaches,
etc., are often found sac-like bodies, called Gregarinae. (Fig.
10.) These simple creatures are nearly destitute of organs,
having simply in one part of their body a small nucleus and
nucleolus, and a delicate muscular fibre. Nourishing itself
by imbibing the juices of the animal in which it lives,
slowly narrowing or lengthening its body in different direc-
tions,- -this motion being probably caused by the delicate
muscular fibre just mentioned, — the Gregarina passes its
existence. At times, however, this motion ceasing, it takes
the shape of a sac. (Fig. io, b.) The nucleus and nucleolus
disappear. The substance of the body breaks up into
what have been called pseudo-navicellae, from their resem-
blance to the Navicula. The contents of the navicellae
(Fig. io, d) are changed under favorable circumstances into
Amceba-like bodies (Fig. io, e, f g, h), which, in their
turn, become Gregarinae. By looking at Tree I. we see
Amoebae, or their haired descendants most likely, divided
into four groups: — 1st, the Sponges, whose supposed
progeny we have treated of as Ccelenterata; 2d, Gregarinae,
whose Amoeba-like development clearly indicates their
ancestry, which we now leave ; 3d, Infusoria, whose young
show in a marked degree their affinity to the Amoebae and
to the Worms ; 4th, the Noctilucae, the animals (allied to the
Infusoria) causing the phosphorescence of the sea by the im-
mense numbers of them found together in tropical climates.
INFUSORIA.
The animalcula of ditches and ponds are made up, in a
great measure, of the microscopical beings called Infusoria,
ZOOLOGY.
31
from their being found in infusions. One of the most
common of these forms is known as Paramcecium ; and
its structure will serve to illustrate this group. The Para-
mcecium (Fig. 24) is often compared to a slipper-shaped
body of semi-fluid consistency (central substance), inclosed
in a rind (cortical layer) ; the rind running insensibly into
the semi-fluid substance. This rind is coated on its outside
with a delicate layer (cuticula), bearing on certain parts
hairs. (Fig. 24, h) If the animal remain quiet, we can
see a depression in the middle of the body, which leads
into the so-called mouth ; this opens into a kind of gullet.
(Fig. 24, g.) This is all the digestive system the Para-
mcecium possesses. In certain parts of the body one can
observe spaces opening and shutting (Fig. 24, c ), and
through these spaces certain canals are said to be visible,
filled most likely with water. It is said these canals or
vessels communicate with the exterior by means of holes in
the layers forming the walls of the body. If such a system
of vessels have really been found in the Infusoria (and
many competent observers are confident that they do exist),
they furnish an important proof of the derivation of the
Worms from the Infusoria, as this rudimentary water- vessel
system is much developed in the Worms. (See Aspidogaster.)
The hairs on the outer layer of the Paramcecium serve as
organs of movement, and, in making currents of water,
drag small particles of food, etc. into the body of the ani-
mal. These hairs (Fig. 24, Ji) are called cilia, and their
movement ciliary action. The Infusoria have been divided
according to the presence or absence of these hairs into
Ciliata and Acinetae (sucking) ; but the transition between
the two seems to be furnished by the bell-shaped Vorticellae,
which are said to produce Acinetae, while the Acinetae
produce Vorticellae. If this be correct, the Acinetae are
only a transition stage of Vorticellae, and all Infusoria are
Ciliata or haired.
EVOLUTION OF LIFE.
The Infusoria are not to be distinguished in their early
stages from Amcebae. Kolpoda-like forms, supposed at
one time to belong to the Infusoria, have since been shown
to be the young of Turbellarian Worms. The Infusoria
seem then to be essentially a transition group; so much so
that some naturalists have held that the group is not a dis-
tinct division of the animal kingdom, but simply a collec-
tion of the young of higher animals. It seems proper to
mention now the necessity of learning the condition of the
young, or embryonic stage of animals, whose origin we are
seeking. Supposing the animal kingdom is really repre-
sented by a tree, of which the main branches, twigs, and
leaflets are the orders, families, and species into which
animals are divided, common features of structure in
these groups must not be sought at the ends of the
branches which are far apart, but at the point where the
branches diverge. To make my meaning clear, take the
case of young babies, which look very much alike, but
owing to certain hereditary influences, and the effects of a
different mode of bringing up, can be readily distinguished
later in life. The origin of Worms is not to be sought in
comparing a highly-organized member of the group with
one of the Infusoria, but by placing side by side a simple
worm like the Planaria and one of the Animalcula. The
proofs of the Worms coming from Infusoria are furnished
by the resemblance of the young of the Soft Worms to
existing Infusoria, and the peculiarities of structure common
to both.
WORMS.
By looking at Tree III. we see the root of the Worms
divides into two branches, — the Soft Worms (Scolecida) and
Sac-worms, — the Soft Worms givingrise to the Articulated
Worms,, in which are seen the beginnings of the Echino-
dermata and Articulata, while the Sac-worms are the com-
Platyeiminthes. Neraatelminthes.
(Flat Worms.) (Round Worms.)
round worms
TRICHINA IN SAC
ECHINORHYNCHUS
TRICHINA FREE
F LAT WORMS
30
PLA MARIA
D ISTOM A
S’toma/ih'l
TAENIA
TAPE WORM
prorhynchu s
ZOOLOGY.
35
young Trichina is set free, and deposits eggs, the embryos
from which bore through the viscera of the unfortunate
one. The Trichina belongs to the family of thread-worms
or Nematoda. Associated with the horse-hair and thread-
worms is the Echinorhynchus, or Bristly-snout (Fig. 27), so
called from the proboscis or snout (Fig 27, a), armed with re-
curved hooks, being the most striking feature in its organiza-
tion. The three families of Round Worms live within other
animals, — the Trichina in the pig and man, the Echinorhyn-
chus in the flounder, the Gordius, or horse-hair worm, in
insects. They are sufficiently alike in their general organi-
zation to be the descendant of a common ancestor; their
modifications are due to their different modes of life.
Turning now to the Flat Worms, we see, according to Tree
III., that the Turbellaria are probably the oldest of this
group. They are arranged in two families, Dendroccela
and Rhabdoccela, according as the intestine is branched,
as in the Planaria (Fig. 28), or straight, as in the Prorhyn-
chus (Fig. 29) or Vortex. The Planaria are found prin-
cipally in fresh water, but also in the sea, adhering to
stones or stems of plants. In the haired covering of their
bodies, in their internal organization and embryo forms,
the Turbellaria are closely allied to the Infusoria, from
which, most likely, they have been derived. From the
Turbellaria have retrograded the Trematoda, of which the
liver fluke (Distoma) (Fig. 30) is a common example. By
retrograding, I mean that the Flukes have lost organs,
from want of use, which they would have retained had
they not lived as parasites in the viscera of other animals
The I lukes ai e found in almost every kind of animal
Imagine a long chain of Flukes living as one individual,
and we have the Tape-worm, or Taenia (big. 3 0 . repre-
sentative of the Cestoda. Either the Tape-worm has split
into Flukes, or the Flukes have colonized and made the
Tape-worm, or possibly they are both aborted Turbcllarians.
36
EVOLUTION OF LIFE.
The reproduction of the Tape-worm, long involved
in obscurity, is now known to be as follows. There
exists in the Pig at certain times a sac-like worm called
the Cysticercus ; this never progresses; but should the
part of the pig containing this worm be eaten by man, this
sac will be transformed into the Taenia, or Tape-worm.
The Leech and the Peripatus are so nearly allied to the Tre-
matoda that they may be regarded as offshoots of that stem.
Turning back now to the Turbellarian Worms with a straight
intestine (Rhabdoccela), while noticing that the family re-
presented by the Nemertes is given off here (see Tree IIP),
we see, in following the stem upwards, its importance, in
that it furnishes the origin of the Articulated, or Segmented
Worms, with their progeny, the Echinodermata and Articu-
lata. Before leaving the Soft Worms, attention must be
called to the system of vessels which is found in most, if
not all, of this group. It is well developed in the Aspido-
gaster Conchiola (Fig. 32), a Trematode worm found in the
heart-sac of the fresh- water mussel. The worm is shaped
somewhat like a vase. Coursing through its body is seen a
system of vessels, beginning as large tubes, which, getting
smaller, are finally lost as twigs. This system of vessels
is supposed to be the same as that observed in an unde-
veloped condition in the Paramoecium among the Infusoria,
and is found also in the Rotatoria, one of the divisions of
the Articulated Worms.
The Articulated Worms include the three groups of the
Gephyrea, Annelida, and Rotatoria. They are called articu-
lated or segmented, from the fact of their bodies being
composed of segments or pieces joined together. This
arrangement is carried to the furthest extent in the An-
nelida, the Nereids (Fig. 34) numbering as many as hundreds
in their segments. This segmentation is only just per-
ceptible in the Sipunculus (Fig. 33), one of the Gephyrea.
The bodies of the Rotatoria (Fig. 35) are inclosed in a
33
S1PUNCULUS
CHAETOGNATHIC
36
ARTICULATED WORMS
<3S
ROTirER(BRACHIONUS)
SAC WORMS.
BRYOZOA
SAGITTA
ZOOLOGY.
37
transparent case or hardened skin, which is slightly seg-
mented, and through which the jointed intestine may be
seen. The Sipunculus (Fig. 33 ) resembles somewhat our
earth-worm, and is found at low-water mark buried in the
sand. When the tide comes in, the Sipunculus, rising to
the surface, exhibits a circle of tentacles surrounding its
mouth: this can be drawn in by the animal and quite con-
cealed. They resemble slightly the Sea-cucumbers, ani-
mals included in the Echinodermata. Within a few years
a remarkable group of Gephyrea have been found well
preserved in a fossil condition. They have been called
Mailed Worms, or Phractelminthes, and are considered by
Haeckel as furnishing the link between the Worms and
the Star-fishes. We will refer to them again. The An-
nelida, or second division of Articulated Worms, are among
the most beautiful of living creatures, of every size and
color, sometimes seen as pretty little white or red worms
swimming about in our fresh-water streams and ponds, or
living, as sedentary organisms, in tubes constructed out of
the sand and other materials found near the sea-shore, or
swimming along by a kind of undulatory movement. The
Nereids (Fig. 34 ) are composed in some examples of many
hundred joints or segments; each segment is furnished with
a little paddle attached to the side. The blood, rushing -
into the little tufts of hair, which are seen on the upper
surface of each segment, gives the animal a brilliant appear-
ance,— the little hairs refracting the light make so many
rainbows. The whole effect of the Nereid gliding through
the sea is so beautiful that it has called forth the admira-
tion of the poets. The Annelida increase their length by
adding segments to those already formed. In this respect
they resemble the Centipedes, etc., which belong to the
Myriapoda, of which we will speak again. The Rotatoria
( F 'g- 35), or third division of the Articulated Worms, are
micioscopical. They live in fresh or salt water; they are
38
EVOLUTION OF LIFE.
composed of a head and a body ; sometimes the head and
body coalesce. The head is furnished with fine hairs ar-
ranged in different manners, and when these cilia are in
action they look like wheels. The other end of the body
terminates in a jointed foot. Both the wheel-organs and
foot can be drawn within the case in which the body of the
Rotifer is inclosed. This case resembles that of the Crabs.
The Rotatoria possess the water-vascular system of the
Worms, as described in Aspidogaster. The group is in-
termediate in its structure between the Soft Worms, the
Annelida, and the Crabs, — the Rotatoria having been con-
sidered to belong to each of these groups by different
naturalists. They represent very naturally that point of
the tree where the Soft Worms end and the Crabs begin.
Before leaving the Articulated Worms, the position of the
Artisca must be noticed. They have been called Tar-
digrada, from the slowness of their movement ; they are
usually considered as nearly related to the Spiders ; others
have looked upon them as Annelids, while some have con-
sidered them as the links between the Soft Worms and
Rotatoria. They are placed, therefore, near these groups,
without assigning to them a definite position. From the
difficulty experienced in their classification, the Rotatoria
and Artisca afford a striking proof of the truth of an evo-
lution of these worms in some such manner. Having
called attention briefly to the Soft and Articulated Worms,
we pass to the last division, the Sac-worms, which includes
the Bryozoa and Tunicata.
The Bryozoa resemble living moss, and are found both in
fresh and salt water. When observed under the microscope,
this moss is seen to be composed of minute tubes, in which
the Paludicella, a Bryozoon (Fig. 37), lives. Though this
creature is small, it is more complex than many of the
animals we have called attention to. The Paludicella has
a mouth, gullet, stomach, and intestine, which are entirely
ill >>
lil
ZOOLOGY.
39
shut off from the general cavity of the body : a great
advance in structure as compared to that of the Anem-
one and Jelly-fish. The Bryozoa are usually classed
with the Clams and Oysters (Mollusca); but, from their de-
velopment from worm-like embryos, they are more justly
considered as a group of worms. This view of the po-
sition of the Bryozoa is confirmed by the recent discov-
eries of the worm-like development of the Brachiopoda,
the first class of the Mollusca. The Bryozoa are probably
the root of the Mollusca, and the connecting link between
them and the Worms. The Tunicata, the other division
of the Sac-worms, are so called from the animals repre-
senting them being inclosed in a bag or tunic. They are
a very important group, as showing probably that point
where the stem of the Fishes originated. The young As-
cidian (Fig. 38, a), one of the Tunicata, resembles a tad-
pole, and in this condition has quite as much of a back-
bone (Fig. 38, C) as the Amphioxus (Fig. 39, 40, C), the
simplest vertebrate known. The Ascidian, when mature, is
like a double-necked vase. The arrangement of the ner-
vous system in the Tunicata differs from that of the Bryo-
zoa, and serves as a distinguishing mark. The curious
worm Sagitta (Fig. 36), the only representative of the
Chsetognathi, has certain affinities with the thread-worm as
well as with the simplest of the vertebrata ; it is therefore
placed between the two.
The Coelenterata are characterized by the want of speci-
alized stiuctures; that division of labor, so conspicuous
in the higher animals, begins to be seen in the Worms,
the digestive system in them being more or less developed,
together with a rudimentary heart, respiratory and excre-
tory apparatus, and the elements of a nervous system.
The Tree of Worms is essentially an intermediate one, — its
roots intimately connected with the simplest forms of life,
Gregarinae, Infusoria, etc., — its branches expanding into the
40
EVOLUTION OF LIFE.
rest of the animal kingdom. By looking at Tree IV. may
be seen the stem of the Gephyrea, giving origin to the
Star-fishes, the simplest of the Echinodermata. In the
Annelida will be found the roots of the Tracheate, or tube-
breathing Articulata, while the Rotatoria lead equally nat-
urally to the Crabs. The Articulated Worms furnish us
with the roots of the Echinodermata and Articulata, while
the Sac-worms contain the foreshadowing of the Verte-
brata and Mollusca.
ECHINODERMATA.
This division of the animal kingdom includes the Star-
fishes, Feather-stars, Sea-urchins, and Sea-cucumbers.
(Figs. 41, 43, 44, 45.) Every one who has visited the sea-
shore is familiar with the appearance of the star-fish. (Fig.
41.) From the mouth, which lies in the centre of the body,
fork out five arms, which run insensibly into each other, the
mouth lying in the middle of the space formed by the
union of the diverging or radiating arms. The number of
arms in some star-fishes is as many even as forty, but the
most common number in all the Echinodermata is five.
Each arm in the star fish is composed of movable segments.
There exists also a water-vascular system, which terminates
externally in suckers, serving as organs of locomotion.
There is a rudimentary blood-vessel system, beginning as a
tube in the body of the star-fish, and which courses out-
wards. On the under surface of the arm is found a fine
nervous thread, coming from a ring surrounding the mouth,
and, finally, at the free end of each arm eyes are found.
The arm of a star-fish is, in fact, a worm ; not simply resem-
bling one, but structurally the same, the segmentation, the
water-vascular system, the nervous cord in each arm of
the star-fish being exactly the same as that of an articulated
worm. The star-fish has probably been produced through
ZOOLOGY.
41
the union of five worms, the worms having united at their
posterior ends, since the eyes are seen at the free ends of
the star-fish. This interpretation of the structure of the
star-fish is not without a parallel among the worms. The
Botryllus, one of the sac-worms, is really composed of many
little Ascidians living as one individual. There is nothing
more extraordinary in five worms living together as a star-
fish, than in many little Ascidians living together as a Botryl-
lus. This view of the origin and the structure of the star-fish,
first proposed by Haeckel, is in perfect harmony, according
to the same author, with the facts of its development. The
egg of the star-fish is transformed into a larva, provided
with an intestine from the inner part of the body of the
larva. Around its mouth appear five distinct layers, which,
uniting at their posterior ends, form the body and arms
of the mature animal. The same kind of reproduction is
seen in the Sipunculi, which are supposed to be indirectly
the ancestors of the star-fish, and also in the Nemertian
worms, from which, or their allies, the Sipunculi and other
articulated worms have descended. Within a few years
there have been found a very well-preserved group of fossil
worms, — the Phractelminthes, or mailed worms. These are
considered by Haeckel to be intermediate between the
Sipunculus and the star-fish, they being scarcely distin-
guishable from the arms of the latter. Through the union
of worms, like the Phractelminthes, have the star-fishes
been produced. The origin of the Asteridai, or star-fishes,
from the worms, is in perfect harmony with the structure,
development, and petrified remains of the group. The
most striking facts of their economy are explainable on
such a theory, but are perfectly meaningless on any other.
The star-fishes are probably the ancestors of the remaining
Echinodermata. Passing over the Ophiuridae, which differ
but little from the star-fishes, we come to the Feather-stars,
or Comatula (Fig. 43), which, when young, live in a
42
EVOLUTION OF LIFE.
stationary condition, rooted by a stern ; in this immature
state it was supposed for a long time to be a distinct animal,
known as the Pentacrinus. (Fig. 42.) After a time, how-
ever, tlie stem disappears, and the little creature floats off
as the very pretty Comatula. The Comatula is very inter-
esting, as its early Pentacrinus stage is the only living
representative of the Crinoids, known commonly as lily
stones, and as St. Cuthbert’s beads, when segments of the
stem alone are preserved. The Crinoids are now extinct
but are preserved in great profusion in the fossil state. As
the star-fishes in one stage of their existence are more or
less fixed, and as the Crinoids have died out, save the only
living example, the young of the Comatula, it is possible that
the Crinoids are the earliest of the Echinodermata. Haeckel,
however, considers the Crinoids as a very ancient offshoot
of the star-fishes, adapted to the fixed state of living. Per-
haps the Crinoids and star-fishes are the diverging stems
of an intermediate group, partaking in its nature of the
peculiarities of both these classes. In either case the star-
fishes are the progenitors of the sea-urchins, and they of the
sea-cucumbers. Imagine the five arms of the star-fish bend-
ing down until their free ends, uniting in the middle, form
a ball-shaped figure ; suppose the empty spaces between
the arms to be filled up, and a sphere will be formed. Such
are the relations of the star-fish to the sea-urchin, or Echinus.
Many intermediate fossil forms have been found connecting
these extremes. The sea-urchins, or sea-eggs, are covered
with innumerable spines or bristles ; hence their name of
Echini. (Fig. 44.) These spines are movable, being loosely
articulated to little knobs covering the body. When one
watches a living Echinus, there may be seen protruding
between the spines sucker-like appendages, which serve as
a means of progression. If the spines be removed, the
body of the Echinus is seen to be a hollow sphere, com-
posed of arms (ambulacral plates) and intermediate arms
ZOOLOGY.
43
(interambulacral plates). The arms are pierced with holes,
hence their name of ambulacra ; through these holes or
ambulacra are protruded the sucker-like bodies just men-
tioned. There are ten ambulacral plates, arranged in pairs,
and between these ten interambulacral plates, also in pairs ;
so, starting from right to left, we have two ambulacral plates
united, then two interambulacral plates united, and so on
around the shell. The plates are composed of still smaller
pieces, these minute plates being formed through the
secreting power of the skin, which dips down between the
different plates. The shell of an Echinus, with its innumer-
able pieces, plates, spines, and suckers, is therefore quite a
complex organism. If we turn to the interior of the animal,
we find the intestine loosely attached, but possessing in its
jaws a most complicated apparatus, the so-called Lantern
of Aristotle. This lantern-shaped apparatus is composed
of five triangular pieces, united at their bases. Crowning
the apex of each triangle is seen a tooth, the sides of the
triangle being furnished with fine saw-like teeth. The five
triangles are kept firm by clamps, and movable through
delicate muscles, the whole forming a most efficient, though
delicate, arrangement. The nervous system is a simple
ring surrounding the mouth, with radiating threads ; the
organs of reproduction are arranged in a direction corre-
sponding to that of the arms. The structure of the Echinus
is essentially radiate. Suppose, however, that an Echinus
be drawn out until its length exceeds its breadth, and the
mouth be encircled by a wreath of tentacles, we would
have then a sea-cucumber, or Holothuria. (Fig. 45.) The
Echinodermata agree in the structure of their water-vascu-
lai locomotor system, in the peculiar lining or hardening
of the skin which incloses their bodies, and in many
other respects. They may be regarded, therefore, from
their structure and manner of development, as a distinct
division of the animal kingdom. The origin of the Echino-
44
EVOLUTION OF LIFE.
clermata from the Soft Worms, with which they are most
closely allied, is in harmony with the views of the most
eminent naturalists of the present day.
ARTICULATA.
We turn now to a consideration of the Articulata, so
called from their bodies being composed of distinct pieces
jointed or articulated together. They include the Centi-
pedes, known as the Myriapoda, from their numerous feet,
the Spiders, or Arachnida, with eight feet, and the Insects,
which have only six feet. We will pass over for the
present the Crustacea, or last order of Articulata, and con-
fine ourselves for the moment to the Centipedes, Insects,
and Spiders (Figs. 46, 48, 49), which agree in breathing by
means of fine tubes opening externally. These tubes pass
from the walls of the body, getting smaller and smaller, until
they are lost in a net-work. In the inside of these tubes,
arranged in the form of a spiral, is found a delicate wire,
which serves to keep the tubes expanded. This respiratory
system is known as the Tracheate: hence the Centipedes,
Insects, and Spiders are joined in one division, the Trache-
ata. A Myriapod, or Centipede (Fig. 46), is composed of
numerous segments resembling a Nereid ; in fact, it has
been observed that the Myriapoda are to the land what
the Annelida are to the water. In the Insect (Fig. 48) we
can distinguish only three segments, known as head, thorax,
and abdomen. There are seen usually in Insects two pairs
of wings, less often one pair, and in some cases none are
apparent. In the Spider (Fig. 49) the head and breast are
soldered into one piece, known as cephalo-thorax. So in
the Arachnida we find only two segments. While the
Myriapoda, Insecta, and Arachnida breathe by tracheae,
the Crustacea, including the Crabs, Lobsters, etc., breathe
by gills. They live in the water, and are of every size,
ZOOLOGY.
45
shape, and color. The question now arises, Do the Tra-
cheata come from the Crustacea, or are they modified An-
nelida? Plausible arguments have been advanced for the
first of these views ; but the second, or that of the Tracheata
coming from the Annelida, will be the one here adopted.
On seeing for the first time the minute worm resembling
an Annelid (Fig. 4 7), moving through the water, it would
surprise the observer to learn that it was the larva, or unde-
veloped young, of an Insect. The numerous segments of
which the immature Insect and Spider are composed grad-
ually coalesce, until finally the perfect Insect exhibits only
three pieces, the Spider two. In the young of the Ephemera,
or the one-day fly, and of the Libellula, small respiratory
tufts are found externally, exactly as in the Annelida, which
were alluded to in speaking of the brilliant colors of the
Nereis. The existence in the larva of these external respi-
ratory tufts, the manner of the development of the young
of Insects and Spiders, furnishes the clue to their origin.
The development, however, of the Myriapoda is just the
reverse of that of the Insects, the Centipedes, etc. increasing
instead of diminishing the number of their segments. Ori-
ginally the body is composed of a congeries of cells, segment
after segment being added, exactly in the same manner as
in the case of the Annelida, \^jth which in structure they
closely agree, being adapted, however, to live on land.
The Annelida seem then to be the ancestors of the Myria-
poda, Insects, and Spiders, the Myriapoda retaining much
of the Annelid structure through life, whereas the In-
sect is an Annelid or Myriapod only when in a larval or
undeveloped condition. That the development of the dif-
ferent kinds of insects has been gradual, Geology seems
to show, the evidences for which will be brought forward
in the chapter on that subject. By looking at Tree IV. the
Hymenoptera will be seen very high up; this family includes
the Bees, Ants, etc., whose economy has always been the
46
EVOLUTION OF LIFE.
subject of admiration on the part of naturalists. The Ar-
ticulata are the most complex in structure of the Inverte-
brata, or animals without a backbone. The nervous system
is highly developed, compound eyes are present, the digestive
system has various parts, excretory glands and ducts have
been discovered, respiration is carried on by the beautiful
system of tracheae, and of their powers of jumping, flying,
stinging, biting, and making noises every one is aware.
The remaining division of the Articulata, including the
Crabs, etc. (Fig. 51), though differing greatly in shape, size,
etc., are all alike in their early stages. The Nauplius (Fig.
50), or primitive stage of every Crustacean, seems to be
more nearly allied to the Rotatoria than any other group
of animals. Some of the microscopic forms of the Crus-
tacea, as Cypris, Daphnia, Cyclops, furnish the transitions
from the Rotatoria to the Crustacea ; indeed, the Rotatoria
have been considered as a group of the Crustacea by many
naturalists.
MOLLUSCA.
The most striking difference in the Mollusca, as com-
pared with the Articulata, is seen in the entire want of that
segmentation which is so apparent in the Insects or Centi-
pedes. The body of an Oyster, a molluscous animal, is a
soft mass, and, though possessed of organs, never exhibits
the slightest trace of joints, as seen in the higher worms,
insects, etc. The nervous system is composed of a few
scattered nervous masses or ganglia, there being no distinct
chain of ganglia running through the body from head to
tail. Indeed, some of the Mollusca have no head, being
known as the Acephala. For this reason the Acephala in-
clude the Brachiopoda and Conchifera. The Brachiopoda,
Lamp Shells', or Arm-foot Mollusca, are better called Spiro-
branchiae, as their branchiae, or gills, are arranged in the
Phractelminthes. Tracheata. Crustacea.
(Mailed Worms.) (Breathing by Tracheaa.) (Breathing by Gills.
ZOOLOGY.
47
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48
EVOLUTION OF LIFE.
form of a spiral. They are represented in the present seas
by very few genera, Lingula, Terebratula, etc. These spiral-
shaped gills were supposed to be used as arms or feet :
hence their common name of Arm-feet or Brachiopoda.
The Conchifera are better named Lamellibranchiata, from
the gills in this class being arranged in the shape of
plates or lamellae. This class includes the oysters, clams,
mussels. The remaining classes of the Mollusca, the Gas-
teropoda and Cephalopoda, differ from the Acephala not
only in having heads, but in many other respects. The
Gasteropoda, or Belly-feet, are so called from these creatures
moving on that part of their body. This class is repre-
sented by the Whelks (Fig. 52), most of the shells on the
sea-shore, and the Snails. The common garden-snail is
remarkable on account of the great number of teeth which
arise from the tongue : as many as twenty-five thousand
are said, according to competent authority, to have been
discovered. The Cephalopoda (Fig. 54) are distinguished
by having long arms or feet radiating from the head; hence
the name of this class, which includes the Cuttle-fish and the
Pearly Nautilus of the Indian Ocean. Gasteropoda like the
Dentalium are so rudimentary as regards the development
of the head, that they may be looked upon as offering the
transition from the Gasteropoda to the Lamellibranchiata.
The Spirobranchiata, or Brachiopoda, in their development
and structure are so closely allied to the Bryozoa that per-
haps they ought to be considered rather as part of the
Worms than as belonging to the Mollusca. The curious
affinities of the Brachiopoda, Bryozoa, and Worms are
striking proofs for the view that the Mollusca have come
from the Bryozoa, or animals allied to them, and they from
the Worms. That the Brachiopoda were the first Mollusca
that appeared on the earth is at once suggested from the
enormous number of fossil forms that are found in the
oldest rocks. They are so numerous that the name “Age
ZOOLOGY.
49
of Mollusca” has been given to the time during which
these creatures lived, there being found in great numbers
also representatives of the other classes of Mollusca,
though not in so great a profusion as Brachiopods. The
Brachiopoda of the present seas are restricted to a few
genera, the class having nearly died out. This is true, com-
paratively speaking, of the rest of the Mollusca, though
not in so great degree. This fact of the abundance of the
Mollusca in the oldest rocks, and of the Brachiopoda in
particular, harmonizes with the facts of their structure and
development in showing that the group must have branched
off from the main trunk (worms) very early in time, and that
of the Mollusca the Brachiopoda are the oldest. In some
Gasteropoda the feet appear modified as wings, as in Hyalsea
and Cleodora, constituting the Pteropoda, and offering the
transition to the Cephalopoda. Th’is view is confirmed by
the embryos of the Gasteropoda, Pteropoda, and Cepha-
lopoda (Fig. 53) being so very similar. The Gasteropoda
breathe both by gills and lungs; examples of the gill-breath-
ing kind are seen in the Whelks (Buccinum) (Fig. 52) often
picked up on the sea-shore while the garden-snail will repre-
sent the lung-breathing kind. The beautiful Carinaria, with
its delicate propeller, is a highly specialized gill-breather.
The Cephalopoda are the most highly organized of the
Mollusca. The Cuttle-fishes (Fig. 54), with their long arms,
are familiar to all who have read the “ Toilers of the Sea.”
In them we find the nervous system well developed, eyes
aic present, the viscera are large, while blood circulates
through arteries and veins. The Cuttle-fish is able to conceal
itself through emitting a very brownish-black fluid, which
is contained in the so-called ink-bag. They breathe’ by two
gills, but in one genus, the Pearly Nautilus, four gills are
piesent. The Nautilus is the only living representative of
myriads of fossil forms, the Ammonites, and is probably the
ancestoi of the two-gilled Cephalopods. The evidences of
4
5 °
EVOLUTION OF LIFE.
Invertebrata.
Vertebrata.
ANIMAL KINGDOM.
’ Protozoa.
Coelenterata.
Vermes.
Echinodermata.
Articulata.
Mollusca.
' Monads.
Amoebse.
- Gregarinte.
Infusoria.
Sponges.
r Corals.
\ Jelly-Fishes.
^ Worms.
’ Star-Fishes.
Feather- Stars.
Sea-Urchins.
Sea- Cucumbers.
V.
Crabs.
Centipedes.
Insects.
Spiders.
" Lamp Shells.
Oysters.
Snails.
Cuttle-Fishes.
' Fishes.
Batrachia.
- Reptiles.
Birds.
Mammals.
Terebratula. Lingula.
ZOOLOGY.
51
52
EVOLUTION OF LIFE.
Anatomy, Embryology, and Geology, when taken together,
make it most probable that the Tree of the Mollusca is
such as represented.
With the Mollusca we leave the Invertebrata, or animals
without a backbone, and turn to the Vertebrata.
VERTEBRATA.
This division includes — 1st, the Fishes; 2d, the Batrachia
(frogs, etc.) ; 3d, the Reptiles (snakes, etc.) ; 4th, the Birds;
5th, the Mammals (animals suckling their young). They
all possess a backbone, rudimentary in some fishes. This
backbone is composed of separate bony pieces known as
vertebrae; hence the name of Vertebrata given to the five
classes just mentioned. Running through this backbone,
spine, or vertebral column, as it is differently called, is seen
the marrow or spinal cord, — a nervous cord which expands
into the brain, which is inclosed by the skull-bones. Such
a structure is never seen in a star-fish, insect, or mollusk.
The Vertebrata never possess more than two pairs of
limbs. The muscles moving these limbs are attached to
bones, which, together with the skull and backbone, form
the skeleton. The skeleton is the most characteristic
feature of the Vertebrata, and nothing like it is met with in
the Invertebrata, called also Evertebrata, that is, without
vertebrae. There are apparent exceptions, such as the wing
of an insect, among the Invertebrates, which is used like
the wing of a bird; but the wing of the insect is only an
expansion of the skin, whereas the wing of a bird is always
supported by bone. The wing of the insect and that of the
bird are said to be analogous, because they are used for the
same purpose; they are not homologous, because they have
not the same structure. The jaws of a Vertebrate are always
parts of the head, never, as in many of the Crabs, modifica-
tions of the anterior limbs. There are found at different
ZOOLOGY.
53
stages of existence in the Vertebrata, behind the mouth,
o
thickenings ; they are known as the visceral arches. (Fig.
178, c.) The spaces between these thickenings finally dis-
1 appear, so that the interior of the mouth communicates
with the exterior. Such a condition is retained in fishes,
where we see the water entering the mouth and passing out
through the gills. The visceral arches are never seen
j among the Invertebrates. Such structures as those just
mentioned were often quoted as separating the Vertebrates
: entirely from the Invertebrates; and these differences, as
l well as others, were so great that they were considered as
offering an insuperable objection to the view that the Verte-
brata had been developed from the Invertebrata. Recently
it has been shown, however, that the Ascidia, one of the
Tunicate sac-worms, develops in the same manner as the
: Amphioxus, the simplest fish known. The young Ascidian
; (Fig. 38, a ) resembles a tadpole, and swims freely about by
1 means of its tail. In this state it has as much of a backbone
as the Amphioxus. After it matures it becomes stationary
| (Fig. 38), remaining attached to objects by means of a root-
like foot. The gulf between the Vertebrates and Inverte-
brates is now bridged over by this discovery of the identical
I development of the Amphioxus and Ascidia. The Am-
phioxus is the only living representative of a group probably
long since extinct. This group, allied to the sac-worms in
its structure, has in one direction retrograded, the Ascidians,
in another progressed, the Amphioxus.
The structure of the skull offers one of the most striking-
proofs for the common origin of the Vertebrata. If we
: compare in this respect a fish, turtle, bird, mouse, elephant,
and man, we shall find that, notwithstanding the great
difference in appearance of these animals, their skulls are
fundamentally composed of the same bones arranged in the
i same manner.
Remembering the different uses of the arm of man and
54
EVOLUTION OF LIFE.
monkey, the wing of bat and bird, the pectoral fins of
whale and Ichthyosaurus, the fore limb of horse and frog,
one would not believe that they are all identical structures.
Nevertheless, Comparative Osteology has shown that the
fore limb in every Vertebrate is composed of the same
bones, joined in the same way (Figs. 82 to 86), giving
attachments to the same kind of muscles, though serving
very different purposes, as in the cases just mentioned.
There seems to be but one explanation for the existence
of these similar parts with dissimilar uses, namely, that the
Vertebrata have descended from one common ancestor, and
that their posterity, subjected to different conditions of ex-
istence, have had their originally similar structures more
or less modified.
Embryology has shown that the early conditions of all
Vertebrata are alike, so much so that it is impossible to
distinguish the young turtle, chicken, dog, and man (Figs.
178 to 1 81) from one another at certain stages of their
existence; and that in proportion as the animals are alike
when mature, the longer will their young resemble each
other, whereas in those animals which are most unlike
when adult, it will be found that their young early indicate
difference; and that what is transitory in the higher
animals is retained permanently in the lower, — the higher
animals representing at some time the lower. These facts
can only be explained by the theory that the Vertebrata
are the descendants of a common ancestor. Geology has
shown that the earth has experienced great changes
through past time, — the sea washing away the land, the
land filling up the sea, together with other causes, changing
entirely the conditions of existence. Some of the animals
living at that day, not capable of resisting such changes,
perished, in many cases leaving their skeletons well pre-
served, as imperishable proof of their having lived. Such
are known as fossils, and the study of these ancient remains
ZOOLOGY.
55
constitutes Paleontology. This science has shown that
forms so different as the Horse and Rhinoceros are linked
together by the fossil forms of Coryphodon, Paleothcrium,
etc.; that the Pig and Hippopotamus represent another
group, connected by Anoplotherium and Dichotrum, etc. ;
that the Fishes and Batrachia form one great division, the
Reptiles and Birds another, — forms linking indissolubly
together these divisions of the Vertebrates having been
discovered in different parts of the world. The structure,
the development, and fossil remains all harmonize in prov-
ing without a doubt that they are only the modified posterity
of a class now extinct, which the Amphioxus nearly repre-
sents. That the Amphioxus came from Worms in their
structure allied to Ascidians, is highly probable. But, given
the Amphioxus, that the genealogy of the Vertebrata is
represented by a tree, like that provisionally offered in Tree
V., seems to us to follow, without doubt, from the facts of
Anatomy, Geology, and Embryology.
FISHES.
The Amphioxus, or Lancelet, is a little animal about two
inches long, found generally buried in the sand on the
coasts of different seas. It does not possess head, brain,
eyes, or limbs, and yet there exists a backbone in a rudi-
mentary condition (notochord), and marrow. Its gills are
not like those of fishes, but its branchial apparatus is that
of an Ascidian (Fig. 40), confirming the view of the origin
of the Amphioxus from the Ascidian Worms, suggested by
their identical development. What is the Amphioxus ? It
seems to be an intermediate animal, a link connecting the
Ascidian with the Fishes. The part of the body contain-
ing the mouth is usually regarded as the head, and is mem-
branous in structure, which condition is found in fishes at
certain penods of their existence. We may designate the
EVOLUTION OF LIFE.
5(3
class of fishes of which the Amphioxus is the representa-
tive, then, as Membranous Fishes. The first step in com-
plexity of structure is presented by the simplest of the
gristly (cartilaginous) fishes, Lamprey. They possess a
gristly skull, with brain, etc., but there is no lower jaw
attached to the skull, their mouth being of the sucking
kind (Cyclostomi). There are no traces of limbs as yet;
but the sucking fishes have a distinct heart, differing
from the Amphioxus, wherein we find only slight dila-
tations of the blood-vessels. The Myxine, or Hag-fish, and
the Petromyzon, or Lamprey, are representatives of this
order. In the Chimsera we find a lower jaw, but its sus-
pensorium is still immovable. It furnishes the transition
from the Lamprey kind to the Sharks. (Fig. 55.) The
Sharks and Rays (Devil-fish) are still gristly in structure,
but their jaws are very freely movable, and furnished with
numerous teeth, which are very characteristic in the differ-
ent kinds. These teeth are found fossil in great numbers in
the early rocks, and prove that the gristly fishes were among
the first Vertebrates that appeared in the seas. The Sharks
possess two pairs of fins, and their intestine is furnished
with valves arranged in a spiral or transversely. We come
next to a class of fishes known as Ganoids, that is, shining.
In some of these, as in the Sturgeon (Fig. 56), we have
the backbone still gristly, while in others, as in the Gar-
pike, it is bony. The outer part of the body is covered
either with shiny plates (Placoganoids), as in the Coccos-
teus, Sturgeon, or with shiny scales (Lepidoganoids), as in
the Gar-pike. It is by means of these shiny plates and
scales, as well as the whole fish, found in great profusion,
well preserved in the early rocks, that we know that the
Ganoids are very old fish, and that they existed in great
numbers in the early ages of the earth ; whereas at the
present day the Ganoids are represented only by half a
dozen kinds, the Sturgeon, Gar-pike, Polypterus, etc. The
ss
ICHTHYOSAURUS
ZOOLOGY.
57
Ganoids agree with the Sharks in the structure of their
heart and optic nerves, and Polypterus has the spiral intes-
tinal valve of the Sharks, but their skulls have true bones,
and they possess a gill-cover (opercular appendage). In
this respect they agree with the Teliosts, or bony fish,
of the present day. If we compare the tail of one of our
common fish, a Cod, or Shad, or Perch (Fig. 57), with the
tail of a Shark (Fig. 55) or a Sturgeon, we see that in the
Perch the end of the tail divides into two equal parts,
whereas in the Sturgeon (Fig. 56) the tail divides unequally.
The unequally-ending or heterocercal tail is characteristic
of these Ganoid fishes, and the equally-ending or homocer-
cal tail is equally characteristic of our common fishes ; but
the tail of the embryo of one of our common fishes ending
unequally is as heterocercal as the tail of the Sturgeon.
The embryo fish is composed also of gristle, as regards its
backbone and skull. Hence the transitory stage or em-
bryo condition of our common fish represents the perma-
nent stage of the Sharks and Sturgeons, — a striking proof
of the truth of the view that the Bony Fish, or Teliosts, are
the posterity of the Ganoids and Sharks. Fossil Ganoids,
like the Ccelacanthes, Holoptychii, Coccolepis, and Amia
of the present day, were probably the ancestors of fishes
in which the air-bladder has a duct, as seen in the Carp,
Herring, Salmon, while they were probably the progenitors
of those fishes in which the duct is absent or rudimentary, as
in the Perch, Cod, Sole. We turn now to a consideration of
the remaining order of fishes, known as Dipnoi, and repre-
sented by the Lepidosiren (Fig. 59) of South America and
the African rivers. During the rainy season in Africa,
large tracts of land are overflowed by the rising of the
rivers. With the retreating Waters are carried most of the
fish ; but the Lepidosiren remains, and, burrowing in the
mud (hence its name of mud-fish), constructs a hole, leav-
ing only a small opening for the passage of air. Exuding
\
53
EVOLUTION OF LIFE.
a sort of slime as a covering for its body, and remaining in
this torpid condition, it breathes by means of lungs until
the return of the water, when it rises to the surface and
breathes by its gills. Hence the Lepidosiren is both Fish and
Amphibian. As regards its respiration, it is truly an Amphi-
bian. It differs from the ordinary fish in the structure of
its heart, which is composed of three chambers in the
Lepidosiren and Amphibian (Siren, Frog, etc.), whereas in
the Fishes the heart is composed of only two. The Lepi-
dosiren and Polypterus both have the spiral valve in the
intestine, so characteristic of the Sharks. The air-bladder
in Polypterus, and the lungs of Lepidosiren, are the same
in their structure as regards the arteries of these parts and
the relations of their air-ducts. The form of the brain
is the same in Lepidosiren and Polypterus. The skull
of Lepidosiren is intermediate between the gristly and
the bony fishes. The backbone is gristly; in this re-
spect it agrees more with the Fishes than with the Am-
phibia. In the structure of the liver apparatus and the
limbs it agrees with the Amphibia. What is the Lepido-
siren ? Is it a Fish, or is it an Amphibian? The Lepido-
siren is the intermediate form linking the Fishes and
Amphibia together, and is more closely allied to the
Ganoid Polypterus than any living fish. Among the fossil
Ganoids the Coccosteus would represent the Lepidosiren
should its skeleton be fossilized. The Ganoid fishes,
although intermediate between the Sharks and common
bony fishes or Teliosts, have many affinities with the
Amphibia: thus, the Amia and Lepidosteus, among the
Ganoids, have the air-bladder filled with air-vesicles and re-
sembling strongly the lung of the Amphibia. So the back-
bone of the Lepidosteus in the ball-and-socket joint of the
pieces forming its spine differs from all Fishes, and agrees
with many of the Amphibia. The structure of the Ganoids,
Lepidosiren, and Amphibia seems to warrant the conclusion
early stage of TADPOLE
ZOOLOGY.
59
that they are but the links in a chain with the Fishes at
one end and the true Reptiles at the other.* Among the
most perfectly preserved fossils arc the Ichthyosauri (Fig. 58)
and Plesiosauri. They seem, on the whole, to be more allied
to Fishes in the structure of their paddles, backbone, etc.,
and Amphibia in other respects, than to true Reptiles, and
must have diverged early from the main fish stem. Their
position is somewhere near the Lepidosiren, Archegosaurus,
and Labyrinthodon stems.
BATRACHIA.
The Batrachia, or Amphibia, as they are often called,
include the Frogs, Salamanders, Siredons, Tritons, Ccecilia,
and the fossil Archegosaurus and extinct Labyrinthodons.
They breathe by gills, at least at some period of their ex-
istence, and in this respect agree with Fishes. Some of the
Batrachia, as the Siren, Proteus (Fig. 61), and Menobran-
chus, retain their gills throughout life, and for this reason are
called Perennibranchiata ; whereas others, as the Frog
(Fig. 64), lose them after passing through their tadpole
stage. (Figs. 62, 63.) The Batrachia present two types
for consideration : in the one we find the body covered
over with bony plates or scales, as in the extinct Archego-
saurus (Fig. 60), Labyrinthodons, and Coecilia; in the other,
the body is naked, as in the Siren, Salamander, and Frog.
A considerable advance in structure is seen on comparing
the Batrachia with Fishes ; but the Lepidosiren links
together the Ganoid Fishes with the Frog division of the
Batrachia, while the Archegosaurus leads up from the
Ganoids through the Labyrinthodon to the Ccecilia.
The Archegosaurus (Fig. 60), when first discovered, was
supposed to be a fish ; but more careful study has shown
* See page 61 for further proofs of this among the Amphibia.
6 o
EVOLUTION OF LIFE.
equal affinities with the Batrachia. The Labyrinthodon is
another extinct form, with a very large skull, sometimes three
feet in length and two in breadth. The bones of the skull
in Archegosaurus and Labyrinthodon recall strongly the
skull of the Gar-pike and Sturgeon. The persistence of a
gristly backbone in Archegosaurus is the same as in the
Sturgeon. The Lepidosiren and Archegosaurus agree in
the structure of their backbone, and the retention of the
branchial (gill) arches, and in the manner in which their
skulls are joined to the backbone (absence of occipital
condyles). The teeth are of the same kind (labyrinthic)
in the Gar-pike, Archegosaurus, and Labyrinthodon. The
large throat-plates in Archegosaurus are like those of
Megalichthys (fish) and the Gar-pike; whereas, in the struc-
ture of the jaws (Fig. 60, E), certain bones called hyoid,
and in the shoulder-girdle and extremities (Fig. 60, C, D),
we see striking proofs of the relation of Archegosaurus to
Batrachia like Proteus, whose jaws and extremities are
(Fig. 60, b, c, d) very like those of Archegosaurus. The
Archegosaurus form is the link between the Fishes and
Batrachia, on the one hand leading through the Labyrin-
thodon to the Coecilia, on the other to the Frogs through
Siredon forms. The Archegosaurus came either directly
from the Ganoids, or indirectly through the Lepidosiren.
Supposing the latter view to be the true one, then the
Ganoids divided into two branches, one being transformed
into the common fish, the other giving rise to Lepidosiren-
like forms, these leading insensibly to the Archegosaurus,
the earliest of the Amphibia, the long type represented
by Labyrinthodon and Coecilia forming one stem, the
Siredon and Frogs, naked Amphibia, the other. The naked
Batrachia are among the most striking proofs of the truth
of the Derivation theory, as the links are all living. The
Siredons and Proteus (Fig. 65, 61) strongly resemble the
Lepidosiren and Archegosaurus; they have tails and external
ZOOLOGY.
6 1
gills. In the next order, that of the Tritons and Salamanders,
the tails are retained, but the external gills are lost; finally,
the Frog has neither gills nor tail, but the tadpole or the
immature frog has both, so that in one stage of its exist-
ence (Fig. 62) the Frog is a Siredon, later it is more like a
Salamander, finally it (Fig. 63) resembles neither.
REPTILES.
Leaving the Fishes and Batrachia, and turning to the
Reptiles, we see that the Fishes and Batrachia breathe by
means of gills (the Batrachia at some stage of their exist-
ence), whereas the Reptiles always breathe by lungs, as a
bird or four-footed creature. The Vertebrates have been
divided by some naturalists, for this reason, into the two
divisions of the gill-breathing, Fish, Batrachia; and the lung-
breathing, Reptiles, Birds, Mammals. The reptiles, birds, and
mammals agree with each other in possessing, during embryo
life, an amnion and an allantois (see Embryology) ; the fishes
and batrachia never, at any stage of their existence, possess
either. The amnion is a transparent sac filled with a fluid
(liquor amnii) in which the young bird or reptile floats. The
allantois is a vesicle starting from the under part of the
body of the bird or reptile, and filling up the interior of
the egg. The allantois is filled with blood-vessels; and as
the porosity of the egg-shell permits the passing out of the
pernicious carbonic acid, and the passing in of the life-
sustaining oxygen, it is by means of the allantois that
respiration is effected. The visceral arches in the young
bird and reptile (Figs. 179, 178 c) are converted through
growth into part of the jaws and part of the organ of hear-
ing; the visceral arches in the fishes are modified into gills.
We see, therefore, that a great progress has been made on
comparing the structure of the gill- and lung-breathing
division of Vertebrates.
62
EVOLUTION OF LIFE.
The Reptiles of the present day include, 1st, the Lacer-
tilia (Monitors, Chameleons, Wall-lizards); 2d, the Ophidia
(Snakes); 3d, the Crocodilia (Crocodile, Alligator); 4th,
the Chelonia (Turtles); and numerous extinct forms. As
the reptiles that live at the present day are but a small
portion left of those that have once lived, and as these
extinct forms are not always entirely preserved, and from
the nature of petrifaction very little of their soft parts can
be known except from analogy, naturally the ancestors of
the reptilian class have not been positively determined.
Premising that the tree of the Reptiles, like all other such
trefes, is only a provisional one, the following line of descent
is offered with diffidence. As long ago as 1710 the Prote-
rosaurus — which, when translated, means “first lizard” —
was described by Spener, a physician of Berlin. Since
that time other reptiles, allied to Proterosaurus, have been
discovered, as Belodon, Paleosaurus, etc., which have been
classed together as Thecodonts. The skeleton of Prote-
rosaurus resembles most closely, among living reptiles,
that of the Varanus, the large African lizard; but among
the Thecodonts have been found also scales of a crocodilian
nature, so that the Thecodont group seems to be the fore-
runner in the Proterosaurus of the lizards and crocodiles,
while the Paleosaurus and Belodon are the first of a series
leading to the Dinosauria. The Snakes are probably an
offshoot of the Lizard, to which they are closely allied; the
Sepidse (Fig. 68), among the Lacertilia, leading to the
Anguidae (Fig. 67) among the Snakes. The Anemodonts,
of which the Pterodactyle is a remarkable representative,
lead to the Turtles through forms like Rhynchosaurus. The
Dinosauria were represented by huge reptiles like Iguano-
don and Hadrosaurus, of which some were more than thirty
feet long. They are very interesting on account of their
affinities to birds. The different orders of Reptiles seem
to have branched off from a common stock represented by
ZOOLOGY.
63
Thecodont forms, which are allied to the Salamanders
among the Batrachia. Until some better theory of the
origin of Reptiles is offered, this one will be provisionally
accepted.
TREE VI.
Oscines. Raptores.
(Singers.) (Birds of Prey.)
Clamatores. Scansores.
(Crow, etc.) (Climbers.)
Doves.
Pigeons.
Leaving egg blind.
Dodo.
L_
Grallatores.
(Waders.)
Rasores.
(Scratchers.)
Penelopidse.
Natatores.
(Swimmers.)
Oslrich.
Rhea.
Emeu.
Saurophalli.
(Birds leaving egg seeing.)
(Reptile-like Birds.)
Archeopteryx.
(Most ancient Bird.)
(Bird-like Reptiles.)
Compsognathus.
Dinosaurian Reptiles.
Apteryx.
. I .
Dinorms.
I
Cassowary.
BIRDS.
Although the class of Birds presents great variety as
regards differences in shape, color, manner of -living, etc.,
they can be represented by the types of swimming (Fig. 74)
(duck), wading (Fig. 75) (snipe), scratching (Fig. 76)
(chicken), singing (Fig. 78) (lark), flying (humming-bird),
unvsoNia
ZOOLOGY.
65
we find the bones of the foot (first series of tarsal bones)
soldered together and with the tibia as in birds, whereas in
most reptiles these bones remain distinct. The Compso-
gnathus in this, as well as in other respects, is a very bird-
like reptile. The Compsognathus is considered by some
anatomists to belong to the order of Dinosaurian reptiles.
The Dinosauria agree in many respects with the Ostrich
family, perhaps being more nearly allied to them than to
any other order of birds. They used their hind limbs only
as a means of progression ; in this respect they resembled
birds more than reptiles; their feet were terminated with
claws (Fig. 70), and the curious arrangement by which the
bones of the leg (tibia and fibula) are united to those of the
foot (astragalus) in birds seems to have been exactly the
same in these huge reptiles. The bones of the leg of the
embryo bird (Fig. 72) are like those of the adult Dinosau-
rian and Reptile. (Figs. 70, 69.) There is good evidence
for supposing that the muscles moving the foot had the
same disposition in some of the Dinosauria as exhibited in
the chicken. According to a high authority on this subject,
“ if the whole hind quarters from the ilium (haunch bone)
to the toes of a half-hatched chicken could be suddenly
enlarged, ossified, and fossilized as they are, they would
furnish us with the last step of the transition between birds
and reptiles, for there would be nothing in their characters
to prevent us from referring them to the Dinosauria.” And
according to the same high authority (Prof. Huxley), if
certain bones of the Hypsilopodon had been found alone,
they would have been certainly described as belonging to
a bird. The idea of these huge Dinosaurs having so
much in common with birds is not a mere theory, but a
truth, whatever inferences may be drawn from it, as the
bones of some of them (the Megalosaurus, etc.), at least in
reference to the posterior extremities, are absolutely the
same as those of a bird. The Compsognathus, in the
5
66
EVOLUTION OF LIFE.
great number of neck-bones (cervical vertebrae), in the light
character of the bones of the head, together with the
structure of the foot, is probably the most bird-like of
reptiles, and is to be considered together with the Megalo-
saurus, Hypsilopodon, and other Dinosauria, as the repre-
sentative of the ancestors of birds. It is not possible to
say exactly which Dinosaur was the progenitor of birds,
but as the Compsognathus is the most bird-like of reptiles,
we take it as our example. The idea of birds coming from
reptiles is suggested by the following facts: ist, existing
birds have much in common with existing reptiles ; 2d, birds
and reptiles, at an early period of their existence, cannot be
distinguished from one another, as in the case of the embryo
chicken and turtle; 3d, the most ancient bird (Archeop-
teryx) is very reptilian, while certain extinct reptiles (Dino-
sauria) are very bird-like. These statements are facts accepted
by naturalists, whether they are evolutionists or not ; they
seem to us to harmonize in warranting the conclusion that
birds are modified reptiles. Among existing birds the
Ostrich family is particularly interesting, as they seem to
be the representatives of a class once much larger. The
Ostrich is found in Africa, the Rhea in South America, the
Emeu in New Holland, and the Cassowary in the East
Indies. They are known as the running birds, their wings
being quite rudimentary. With the Ostrich family is
generally placed the Apteryx of New Zealand. It is a
little bird, the miniature of the gigantic Dinornis, which
stood nearly twice as high as the Ostrich. The Dinornis
has died out very recently, if it be indeed extinct. This
very wide distribution of the Ostrich family suggests
that the order was once much larger, extending all over
the earth, and that the present representatives are the sole
survivors. This seems more natural than to suppose that
the Ostrich, Rhea, and Cassowary appeared independently
in parts of the earth so remote. If this view be correct, then
ZOOLOGY.
67
the running birds are older than the ordinary birds ; this
harmonizes with the fact that the running birds are of
existing birds the most nearly allied to the Dinosauria, the
supposed ancestors of birds. The birds called Penelope
(Cranes) are generally classed with the scratching birds, but
they seem to be more nearly allied to the Rhea, Emeu,
and Cassowary, and are joined with them, and called by
Haeckel Saurophalli. The tree of descent would be then
Dinosaurian reptiles, represented by Compsognathus, etc.
Changed into Archeopteryx-like forms, the most ancient
of birds, the modified posterity of the Archeopteryx would
be represented by the Penelope, Rhea, Emeu, Cassowary,
having three toes. The African Ostrich, having only two
toes, is probably more modern than the three-toed South
American kind, or Rhea. The Cassowary, through the
Dinornis, leads up to the Apteryx, while the Emeu and its
posterity seem to have remained unchanged. The Penelo-
pidae are probably the ancestors of the scratching birds, to
which are nearly allied the recently extinct Dodo of the
Mauritius, and the doves and pigeons. The ducks seem
to form the transition between the Saurophalli and the
swimming birds, though it must be remembered that the
Penguin in its separated metatarsals (bones of the foot)
would indicate an ancient bird. The swimming birds gave
rise probably to the wading birds. All these birds, except-
ing the doves, leave the egg in a condition fitted to nourish
themselves; whereas the doves, pigeons, etc., and their
descendants, leave the egg blind, and are nourished by
their parents. The pigeons and doves, descending through
the Pteroclidae from the scratching birds, probably divided
into two branches, the Clamatores (crows, etc.) and the
Climbers (woodpecker, etc.); the Clamatores were gradually
improved into our singing birds, and the climbing birds
into birds of prey.
68
EVOLUTION OF LIFE.
SUB-CLASS.
Ornithodelphia.
Didelphia.
Monodelphia.
MAMMALIA.
ORDER.
Monotremata.
-[ Marsupialia.
f Carnivora.
Cetacea.
Prosimiae.
Simiae.
Rodentia.
Hyracoidea.
Proboscidea.
Cheiroptera.
Insectivora.
Edentata.
Ungulata.
Sirenia.
EXAMPLE.
Ornithorhynchus.
Opossum.
Dog.
Whale.
Lemur.
Man, Monkey.
Beaver, Rat.
Hyrax.
Elephant.
Bat.
Hedgehog.
Sloth.
Horse, Pig.
Sea-Cow, Dugong.
MAMMALIA.
The class Mammalia is so called from the females suck-
ling their young, and includes the domestic animals as well
as many other less well-known forms. The mammals
differ from the reptiles and birds in many important char-
acters, as in the manner in which the skull and backbone
are joined together (two condyles instead of one), in the
simple structure of the lower jaw, it being composed of
only one piece on each side in the Mammalia, whereas in
the reptiles and birds it is made up of several. The skin
of the mammals is covered more or less with hairs, never
with feathers, as in birds. They bring their young into the
world living, and nourish them for a longer or shorter time
with milk. These peculiarities, as well as others, separate
the birds and reptiles from the mammals. The Mamma-
lia can be divided into three sub-classes, each of which
offers well-marked peculiarities, which serve to distinguish
Monotremata.
TREE VII.
Cow. Sheep. Deer. Musk-Deer. Horse.
70
EVOLUTION OF LIFE.
readily these sub-classes. They have been called Ornitho-
delphia, Didelphia, Monodelphia. The first sub-class is
so called from the terminal arrangement of the abdominal
viscera being the same as that of Birds and Reptiles.
The Ornithorhynchus and Echidna are the only represent-
atives of the Ornithodelphia, and are limited to Australia
and Tasmania. They seem to be the survivors of a class
once much larger, and now extinct. The Didelphia include
the Kangaroos (Fig. 80), Wombats, Opossums, etc. With
the exception of the Opossums, they are also confined to
Australia and the adjacent isles. The most striking feature
in this sub-class is the pouch in which the young are pro-
tected in their helpless condition. The third sub-class of
Mammalia, the Monodelphia, contains as many as twelve
orders, of which the following will serve as examples: Dog,
Whale, Lemur (a sort of Monkey, one of the Prosimiae),
Ape, Man, Beaver, Hyrax, Elephant, Bat, Hedgehog, Sloth,
Horse, Pig, and Sea-cow. The names of the orders of
which these animals are examples may be seen in the
accompanying diagram. It is to be understood that there
are many other examples of each order, which want of
space prevents us from inserting. Of all Mammalia, the
Ornithorhynchus (Fig. 79) and Echidna approach nearest
the Birds and Reptiles, not only in the characteristic
arrangement of the abdominal viscera, but also in the
skeleton. The collar-bone (clavicle), the breast-bone
(sternum), and the coracoid process of the shoulder-blade
(scapula) form together a fork-shaped bone similar to that
of Birds and Lizards. This fork-shaped bone is not present
in the other Mammalia. The ribs in the Ornithorhynchus
offer the same arrangement as seen in the Crocodile, while
the skull is very bird-like in the articulations of its bones,
and in the arrangement of the organs of hearing (semi-
circular canals) and the nerve of smell.
While, therefore, there can be little doubt that the class
ft As
bat bird deer
ZOOLOGY.
71
represented by the Ornithorhynchus is the posterity of the
Sauropsida (birds and reptiles), yet the imperfect knowl- .
edge of the development of the Ornithorhynchus, and the
total absence, so far, of fossil remains, make it impossible
to designate which particular order of Sauropsida ought to
be considered as the progenitor of the Ornithorhynchus,
and through it of the rest of the Mammalia. In seeking
the origin of the pouch-bearing mammals, we meet with
the same difficulties, though not in the same degree. The
Marsupialia are intermediate, in many respects, between the
Monotremata (Ornithorhynchus) and the ordinary Mam-
malia. In the present state of our knowledge, it seems
more advisable to regard simply some of the Monotremata
as the ancestors of the Marsupialia than to attempt to des-
ignate which particular one was that ancestor, or exactly
the manner of their development. That the Marsupialia
came after the Monotremata (Ornithorhynchus, etc.) seems
most probable, from the fact of their young, in their transi-
tory condition, offering the arrangement of the viscera so
characteristic of the Ornithorhynchus, while in their adult
condition they agree with the ordinary Mammalia. The
pouch-bearing Mammalia offer examples of meat and
vegetal feeders, as well as of the leaping, burrowing, and
climbing kinds.
So striking is the parallel between the different kinds of
pouch-bearing mammals and the different orders of the
ordinary Mammalia that many naturalists seem disposed to
consider the different orders of the ordinary mammals as
having come directly or indirectly from the corresponding
kinds of pouch-bearers; that is, extinct Marsupials, like the
grazing and browsing Kangaroo, were the ancestors of the
orders represented at the present time by the Pig and Horse.
Pouch-bearers like the Opossums, using their big toe as
a thumb, gave rise to Monkeys, improperly called four-
handed; while the meat-eaters (Dog) are the posterity of
7 2
EVOLUTION OF LIFE.
extinct Marsupials allied to the Thylacinus. This view
• has much in its favor, as the transition from the pouch-
bearers to the ordinary mammals is very gradual, as, for
example, the smaller Opossums lead up to the Insectivora
(Hedgehog), the Wombat to the Beaver, etc. The fact of
. Australia, with few exceptions, containing only the reptile-
bird-like and pouch-bearing mammals at the present day
seems to confirm the view of the ordinary mammals com-
ing from the pouch-bearers in some such way; for while
we find in other parts of the world fossil remains of
Marsupials, with the exception of the Opossums, the living
pouch-bearers are found only in Australia and the adjacent
islands, the fossil remains being Marsupials, but of a much
larger size. Australia seems to offer us a living picture
of what Europe once has been. Just as in Europe and
other places, among the ordinary mammals, we have vari-
ous kinds preying on each other, so we find the same thing
among the existing pouch-bearers in Australia; and this
relation existed ^also in past time. The Diprotodon (a
gigantic Kangaroo) was warred upon by the Thylacoleo, a
meat-eater of the size of a lion. Supposing this view of
the origin of the ordinary Mammalia to be correct, the
number of branches descending from the pouch-bearers
will depend on the view taken by naturalists of the affini-
ties of the different orders. Although there are twelve
orders in the ordinary Mammalia, some of them seem
directly or indirectly to be more nearly related than others.
Thus, the order of odd-toed (Rhinoceros, Tapir, Horse) and
that of even-toed (Pig, Hippopotamus, Sheep, Deer) are
joined in one group, the Ungulata, or hoofed animals: they
would represent one stem. The Half-Apes, the gnawing ani-
mals, with the Hyrax and Elephant, the insect-eaters, the
bats, and true Apes, with man, would make a second stem.
The meat-eaters (Lion, Fig. 8 1 , Dog, Seal, etc.) may repre-
sent a third stem; while the Edentata, or animals without
ZOOLOGY.
73
incisor (front) teeth, like the Sloth and Ant-eaters, which
have no teeth at all, seem to make a fourth stem.
Without attempting a detailed account of these orders, we
will try to call attention to the most important peculiarities
connected with their organization and possible origin. The
group of odd-toed (Perissodactyla) is so called from its
representatives having an uneven number of toes, the
Rhinoceros three, the Tapir three (at least in hind foot),
the Horse one. These animals, however different in appear-
ance externally, agree further in the structure of the skull
and teeth, the number of pieces in the backbone (not less than
twenty-two dorso-lumbar vertebra), the simple stomach,
and the peculiar character of the intestine (caecum). These
animals are linked together by fossil forms, the whole series
forming a very natural group, the odd-toed, of which the
Paleotherium (Fig. 15 i) is the oldest. ‘The Artiodactyle or
even-toed group — the Hippopotamus, etc., having four toes,
the Cow, Sheep, Deer, etc., two — agree in the structure of the
skull and teeth, and in the number of dorso-lumbar vertebra
(nineteen), while some of them in the complex digestive sys-
tem form the sub-group of the Ruminants, in which there
exist three or four stomachs, one of which serves to hold the
food until it is chewed a second time, while in the Camel
and Llama the second stomach is modified to hold water.
The living even-toed animals, linked together by extinct
forms, make the second natural order of the Ungulata. The
oldest even-toed is the Anoplotherium (Fig. 152). In the
age preceding that in which the Anoplotherium and Paleo-
therium appeared there lived the Lophiodon, Coryphodon,
Pliolophus, etc., animals which, in their dentition, seem to have
combined the peculiarities of both the even- and the odd-
toed orders. They are considered to be the common ances-
tors of the Ungulata, and the posterity of the Diprotodon
and Nototherium, animals allied to the browsing Kangaroo.
The line of descent would be: Marsupials like the Diproto-
7 4
EVOLUTION OF LIFE.
don gave rise to the Lophiodon-like animals; they divided
into the Paleotherium and Anoplotherium, the roots of the
odd- and even-toed orders. The Rhinoceros, of living even-
tofcd, is the most ancient, the Horse the most modern, the
Tapir being intermediate. The links binding the Horse
and its ancestor, the Paleotherium, are furnished by the
Hipparion and Anchitherium ; these extinct animals, in
the structure of their teeth and feet, offering us a picture
of what we see now in the Horse only in an embryonic
condition: that is, the Horse, at one stage of its existence,
is an Hipparion, while still earlier it is an Anchitherium.
While the Paleotherium, descending from the Lophiodon,
originated the odd-toed order, the Anoplotherium, coming
from the same stock, divides into the Xiphodon and
Anthracotherium branches. The Xiphodon, together with
the Dichodon and Dichobune, were the earliest of Rumi-
nants, of which there are the branches of the hollow-
horned, Cow, Sheep, Goat, Antelope; the solid-horned, Deer,
Giraffe; while the Camel and Llama, resembling each other
in many respects, are represented by a separate stem. The
Anthracotherium, the other branch coming from the Ano-
plotherium, divides into the stems of the Pig and Hippo-
potamus; nearly allied to the latter are the Sea-cow and
Dugong, large herbivorous animals, found in bays and at
the mouths of large rivers.
Leaving now the stem of the hoofed animals, or Ungulata,
and turning to that of the Monkeys, etc., we find that many
of the Prosimiae or Half-Apes are found in Madagascar,
from which island the order spreads to the East Indies and
Africa. These Half-Apes were regarded for a long time
as Monkeys, but they differ from the true Monkeys in the
number and structure of their teeth, as well as being char-
acterized by the claw on the second toe. The different
kinds of Idalf-Apes indicate and are the transitions to the
beginnings of other orders. Thus, the Galeopithecus, flying
ZOOLOGY.
75
'Lemur, is a perfect link between the Half-Apes and Bats,
the Cheiromys foreshadows the order of gnawers, resembling
in appearance, as well as in the structure of the teeth, the
gnawers (Rat, Squirrel) more than the Half-Monkeys. The
short-footed Lemurs (Makis and Loris) are more like the
true Monkeys, while the long-footed Tarsius is allied to
the Insect-eaters (Cladobates, Hedgehog). A century ago
the half-apes, gnawers, bats, and apes, with man, were joined
together by Linnaeus, and called Primates; and modern
research seems but to have confirmed his generalization.
Strange as it may at first appear, the Elephant is more nearly
allied to the gnawers (Rodentia) in its skeleton, as well as in
many other respects, than to any other order of the Mam-
malia. One can hardly conceive of a mouse and an elephant
having anything in common ; but it must be remembered
that size has nothing to do with community of structure,
and that there are Rodents, like the Capybara, as large as a
dog. The position of the little Hyrax in the animal kingdom
has been a constant subject for discussion since the days of
i Cuvier. According to some authorities, it stands near the
Elephant and Rodentia, while others place it near the
Tapir, among the odd-toes. I follow Haeckel in placing
it near the Elephant. The true apes have descended from
are not to be separated, we reserve for a separate chapter
the consideration of the Simiae, the highest order of the
Mammalia. The half-apes are probably the posterity of
extinct Marsupials allied to the opossums. The Carnivora
or meat-eaters include the lion (Fig. 81), dog, cat, bear,
walrus, seal, as well as other animals. They have so many
characters in common, and differ so much from all other
orders, that we regard them as a distinct stem, descending-
from Marsupials like the Thylacinus or dog-headed opos-
sum. The transition from the seals to the whales (Cetacea)
is made through the extinct Zeuglodon, which combines
;6
EVOLUTION OF LIFE.
perfectly the peculiarities of both these orders. It must
be mentioned, however, that Haeckel considers the whales,
etc. as being more nearly allied to the Sea-cow, etc. With
the exception of the Ant-eater of South Africa and the
Pangolin common to Asia and Africa, the Edentata, so
called from many of them having no front or incisor teeth,
and some no teeth at all, are confined to South America,
represented there by the Sloths, Armadillos, and Ant-eaters.
The Sloths differ from all other Mammalia in having more
than seven bony pieces in the neck, there being nine cer-
vical vertebrae in the three-toed Sloth, and in the great
number of ribs (twenty-three) in the two-toed Sloth, as well
as in the bird-reptile arrangement of the viscera, agreeing
in this peculiarity with the Ornithorhynchus ; in many
other respects the Edentata show a low grade of organi-
zation. IAom the wide geographical distribution, the grad-
ual extinction, and the reptile-bird-like organization of the
Edentata, we consider them as the survivors of an order
which must have diverged very early from the main stem
of the Mammalia. Gigantic fossils belonging to this order,
like the Megatherium, Megalonyx, Mylodon, have been
found in remote parts of the earth, showing the extent and
size of the order in past time. The Megatherium (twenty-
two feet in length) combines the head of the Sloth with the
backbone and extremities of the Ant-eater. In the present
state of Paleontology and Embryology, it is impossible to
indicate the progenitors of these extinct Edentates.
With the Edentata we leave the Mammalia, and, for the
present, the structure of the animal kingdom. We have
endeavored to show — following principally Haeckel — that
there is a main trunk of life, beginning in the Monads,
ending in Man ; here and there large branches are given
off, terminating in twigs and leaflets. Allusions have been
made to extinct animals, often forming an essential part of
these branches. The relation, in time, that these extinct
ZOOLOGY.
77
animals bear to each other, and to those now living, will
be treated of in the chapter on Geology, while the Devel-
opment or Embryology of the groups will be more detailed
in the chapter on that subject. Though Geology and
Embryology confirm the view of the gradual production
of a tree of life, it seems to us that the structure of
animals, without any other evidence, suggests such a con-
clusion, though we were never able to show the cause of
it. Few astronomers after the time of Kepler doubted that
the orbits of planets were ellipses : it remained for Newton
to show that the attraction of gravitation was the cause of
the ellipse ; Lamarck and others have been to Biology
what Kepler was to Astronomy; if future biologists con-
firm Darwin’s views as to the cause of the evolution of life,
as Laplace, Lagrange, D’Alembert, and Euler placed the
Newtonian theory on a more secure foundation, then
Darwin will be, as he has been already called, the Newton
of Natural History.
BOTANY.
While plants, in their external appearance, present every
variety of size, shape, and color, their internal structure
does not offer the same amount of difference as is observed
in the divisions of the animal kingdom. The old dogma |
that plants live, but animals live and feel, still holds true; I
there not having been found in the vegetal kingdom a trace j
of a nervous system. Some other basis for the classifica-
tion of plants must therefore be chosen. More than a
century ago, Linnaeus divided the vegetal kingdom into
Cryptogamia and Phanerogamia, which may, for the pres- ]
ent, be translated Flowerless and Flowering plants. Modern
science has offered nothing better than the classification of
Linnaeus, it being a natural one. The Flowerless plants,
or the Cryptogamia, include: 1st, the Algae, or the greenish
matter covering bricks, stones, etc., the green thread-plants 1
of ponds and ditches, and the red and black sea-weed ; 2d,
the Fungi, or toadstools, mushrooms, etc.; 3d, the Lichens,
or the parchment-like growths seen covering fence-rails, I
etc.; 4th, the Mosses; 5th, the Ferns. The Flowering plants,
or Phanerogamia, are represented by: 1st, the Cycadae,
bread ferns, etc.; 2d, the Coniferse, pine, cypress; 3d, the
Monocotyledons (one-seed lobe), lily, banana, palm ; 4th,
the Dicotyledons (two-seed lobes), elms, mulberry, gera- (
nium, rose. The first three classes of the Cryptogamia
differ from the Phanerogamia in the absence of flowers,
and in wanting roots, stem, and leaves ; the Mosses and
( 73 )
BOTANY.
79
Ferns, while cryptogamic in their flowerless condition,
agree with the Phanerogamia in having stems and leaves;
they are therefore intermediate in their structure; the tran-
sition forms leading from the simple water-plants, mush-
rooms, etc., to the pines and oaks.
ALGA3.
No class of plants is more interesting than the Algae.
Notwithstanding their very simple structure, they offer
every variety of shape, size, and color. While many of
them are very minute, the beauty of their form, the deli-
cacy of their structure, and their exquisite coloring, never
have failed to attract the attention of the microscopist. The
Confervoidse, or green Algae, are widely distributed, every
pond, ditch, spring, and stream having representatives.
The greenish matter seen on old trees, that found in bogs,
the slime on stones in ponds, the silk-like threads of troughs,
the sea-weed usually seen in marine aquaria, as well as
innumerable other examples which might be given, serve
to illustrate the green Algae, or Confervoidae. Among the
green Algae we find the simplest and smallest of plants,
the Chlorococcus viridis (Fig. 87), which, when aggregated
in hundreds of millions,- composes the greenish matter
clothing in layers old trees, wood palings, etc. The Chlo-
rococcus is a simple cell filled with granular contents.
Under favorable circumstances each cell divides into halves
(Fig. 88), each half becoming a new individual; this pro-
cess may be continued indefinitely: such is the simple
manner of reproduction in this very minute plant. Among
the unicellular green Algae are included the Desmidiacese,
which are found most often in open situations, as in the
pools of bogs and moors. They are among the most
beautiful of microscopic objects. Their most characteristic
feature is that of bilateral symmetry, giving the impression
So
EVOLUTION OF LIFE.
that their body is composed of two cells, as seen in
Euastrum, Cosmarium, Closterium (Figs. 89, 90, 92), or of
many cells, as in Hyalotheca (Fig. 91), but they are really
one-celled plants, as proved by the fact of all the green
contents escaping if the cell-wall be broken, the indenta-
tions and constrictions being only superficial. The con-
striction of Cosmarium indicates the place where the body
will divide into two halves, each half becoming a new
individual. In some forms, as Pediastrum (Fig. 97), the
green contents of the cell are transformed into ciliated
bodies, or zoospores, which escape, the cell-wall breaking,
and move about for some time (Fig. 98), then settle, coa-
lesce, and finally take on the appearance of the parent
plant. The green, thread-like plant of horse-troughs, etc.
is generally composed of the Alga known as Spirogyra
(Fig. 93). Each Spirogyra is a chain of cells, the green
matter of the cells being disposed in the form of a spiral.
At certain seasons of the year, adjacent Spirogyrae are seen
to push out the walls of their cells towards each other
until a communication is formed. (Fig. 94.) The green
contents of one individual, leaving its cell, pass through
the communicating process, and mix with the contents
of its neighbor : this is later the beginning of a future
Spirogyra. This kind of reproduction is known as conju-
gation, and is the simplest type of sexual reproduction, i.c.,
the union of two distinct germinal masses to form a spore.
The Nostochaceae (Fig. 95) attached to stones are composed
of a row of cells or beads, making filaments imbedded in
a gelatinous kind of matter which is inclosed by a mem-
brane ; the membrane breaking, the gelatinous matter
escapes into the water, carrying the filaments with it.
The Nostochaceae have been considered by some botanists
as an undeveloped form of Lichen. With the exception
of the Ulvaceae (Fig. 96), which are marine in their habitat,
the green Algae are confined to fresh water. The Ulva,
BOTANY.
8 I
from which the group takes its name, is the green plant
which usually adorns marine aquaria. It is composed of
layers of cells bound together, and its reproduction is
effected by zoospores, such as we noticed in Pediastrum.
FUCOID/E.
The brown or olive-colored Algae, or Fucoidae, differ not
only in their color from the green Algae, of which we have
just spoken, but equally as regards their size and manner
of reproduction. They are confined to the sea, and are
found generally on submarine rocks, which are exposed,
however, at low tide, to heat, light, and atmospheric influ-
ences. This seems to be necessary for the healthy growth
of the brown Algae, since the specimens that are brought *
up from greater depths do not exhibit so hardy a structure
as those that live at the surface. The Fucoidae are com-
monly known as sea-wrack ; but that generally picked up
at the sea-shore gives no idea of the immense size which
some of the brown Algae attain, the Macrocystis of the
Californian coasts reaching a length of four hundred feet.
Among the Fucoidae are included the Laminaria, or leath-
ery sea-weed; the Fucus (Fig. 99), or bladder-wrack, so
called from floating on the surface of the sea by means of
air-bladders. This bladder-like arrangement in the Sargas-
sum, or gulf-weed, takes the form of a bunch of berries,
and is the most characteristic fpature of the plant. The
importance of the brown Algae may be estimated from the
fact that forty thousand square miles of the Atlantic Ocean
are covered with a kind of oceanic forest of Sargassum.
(Fig. 100.) The presence of this plant gave Columbus
vain hopes of being near land. The reproduction of the
brown Algae has not as yet been perfectly made out. It
is known, however, that the process is sometimes carried
on by zoospores, as in Pediastrum, or by the intervention
6
82
EVOLUTION OF LIFE.
of distinct germinal masses, which unite whilst free in the
water, to form a spore, a process corresponding to the
so-called conjugation of the Spirogyra.
FLORID/E.
The red or rose-colored Algae, though much smaller
than the Fucoidae, surpass them greatly in beauty of color-
ing and delicacy of form. They are commonly known as
red sea-weed, and, when dried and arranged on paper, they
are often offered for sale. The Floridae (Fig. 1(A), or Red
Algae, are from six inches to two feet high, offering in their
coloring different shades of red, rose-red, and purple. Their
form varies from that of a filament or stalk to that of a
leaf or feather. To see them in perfection, they must be
studied in a tropical climate. The reproduction of the
Floridae is still involved in some mystery. There are in
many species tetraspores (Fig. 102), which are formed by
the division of the so-called perispore into four spores,
which appear to correspond with the zoospores of the
lower Algae. Besides these tetraspores, other reproductive
bodies arise in some species from the union of two germs,
which may be looked upon as the representatives of dis-
tinct sexes. While the Green, Brown, and Red Algae
differ greatly in their size, form, coloring, and reproduction,
they all agree in their cellular structure. When we com-
pare a single individual of the Chlorococcus — so minute
that hundreds of thousands might rest on the head of a
knitting-needle — with the gigantic Macrocystis, notwith-
standing minor differences, we find the essentially cellular
structure of both to be the same. The group of Algae is,
therefore, a natural one, the extremes being connected by
innumerable links, offering a gradual transition from micro-
scopic forms to the largest of plants. In the preceding
chapter we have given reasons for supposing it probable
BOTANY.
83
that Monera in past time divided into animal and vegetal
Monera, and endeavored to show how the animal kingdom
may have descended from animal Monera. Although
the precise time and exact manner in which the vegetal
kingdom appeared may never, perhaps, from the nature
of the case, be demonstrated, still, Prof. Haeckel’s view of
vegetal Monera having been the remote ancestors of the
vegetal kingdom has so much in its favor that it may be
accepted as a near approximation to the truth. Following,
then, Prof. Haeckel, the vegetal Monera must be regarded
as the ancestors of the Protophyta, or primitive plants,
those most simple, unicellular Algae, like the Chlorococcus,
etc., while the Green, Brown, and Red Algae represent the
three diverging branches of a stem whose roots originate in
the Protophyta.
FUNGI.
Mushrooms, puff-balls, smuts, mildews, truffles, moulds,
although offering in minor points variety of structure, still
agree in so many important respects, and differ so essen-
tially from all other plants, that they are always associated
by naturalists, and are regarded as forming the very natural
group of Fungi. One of the most general laws of Biology
is that while animals derive their nutriment solely from the
organic world, plants, on the contrary, are nourished by
inorganic matter; in other words, while plants by their
life-processes change inorganic into organic matter, animals
by their life-processes reconvert organic into inorganic
matter. Fungi, in feeding solely on organic matter,
agree with animals, and differ from all other plants. Amy-
lum, or starch-flour, is one of the most constant products
of the vegetal kingdom, yet no trace of this important
principle is found among the Fungi. The green color
so characteristic of plants, due to the presence of
8 4
EVOLUTION OF LIFE.
chlorophyll, is never seen in any Fungi. With some ex-
ceptions, the Fungi nourish themselves on organic matter,
whereas plants combine inorganic matter, such as water,
carbonic acid, ammonia, phosphates, etc., assimilating these
principles in their growth. The life-processes, the absence
of amylum and chlorophyll, are such important facts in the
economy of the Fungi that some naturalists deny that they
are plants at all, and wish to place them in the intermediate
kingdom referred to in the preceding chapter. The repro-
duction of the Fungi, and the many transitional forms
hardly distinguishable from Algae and Lichens, influence
most botanists in regarding them as very aberrant, but still
members of the vegetal kingdom.
Most Fungi are parasitic in their mode of existence, living
at the expense of the plant or animal on which they are
found.
The disease known as scald-head is due to the presence
of a fungus, the Achorion ; the thrush, a throat trouble, is
caused by 7 a fungus, the Oidium. Quite a flora has been
described by Leidy and Robin as existing in the intestines
of different animals, consisting principally of Fungi. The
Fungi are found, however, in the greatest profusion on
decaying vegetal matter, stumps of trees, etc. being con-
verted into powder by them. When half-eaten fruit is
allowed to stand, soon it is seen to be covered with a
whitish film, which, when examined under the microscope,
is found to be made up of the filaments of a Fungus. A
Fungus, while essentially cellular, consists of two parts, the
mycelium, or threads, and the colorless spores, or fruit:
the threads are elongated cells, and resemble in position
the stems of higher plants; the spores are seen at the end
of the threads. (See Fig. 103, Grape Fungus.) The
spores are sometimes free (stylospores), or they are inclosed
in what is called an ascus. (See figure of Stilbospora and
\ Sphaeria, Fig. 104, b, c.) The arrangement of the spores
00 !
r
BOTANY.
35
or fruit, and the proportion of the size of the fruit to the
mycelium or threads, have served as the basis of a classifi-
cation of the Fungi. The mushroom, the puff-ball, the
smut, the mildew, the truffle, and mould, are familiar ex-
amples of the different orders of Fungi. This classification,
like all similar attempts, suffices, so long as types so differ-
ent as a mushroom and mildew are compared. What are
commonly collected as mushrooms are only the fruit of the
fungus Agaricus : the greater part of the mildew examined
show only the mycelium or threads of the fungus Botrytis.
The mushrooms belong to the order Hymenomycetes, so
called from the hymenium, or part supporting the fruit,
being so prominent, the threads being inconspicuous. The
mildew (Fig. 105) illustrates the Hyphomycetes, which
derive their name from the Hyphi, or threads, being so much
developed, the fruit dropping off.
The difficulty of classification arises from the fact that
from time to time individuals are discovered which do not
present such striking contrasts as the mushroom and mildew,
their characters being so little defined as to make it im-
possible to say to what groups they belong. All such
intermediate forms, the source of so much trouble in the
arrangement of an herbarium, are most important proofs
of the truth of the theory of the gradual transformation
of plants. Not only is it true that in the Fungi the orders
pass insensibly into each other, but there are also forms of
which it is doubtful whether they are Fungi, some botanists
still regarding them rather as Algae. Thus, the Peronospora
(Fig. 106), differing from Botrytis (mildew) in its continuous
cells, the partitions of Botrytis (Fig. 105) being absent, is,
according to Prof. Haeckel, a transitional form which links
the Algae through Vauchcria (Fig. 107) with the Fungi,
though the Peronospora is usually regarded as a Fungus,
it having no chlorophyll. The Achlya, sometimes called
Saprolegnia, formerly considered an Alga, seems to be only
86
EVOLUTION OF LIFE.
an aquatic form of the Sporendonema, the common fly
fungus. It was long ago observed by Carus that the
portions of a salamander which were above the surface of
the water produced a Mucor (fungus), while those immersed
gave rise to an Achlya (alga). While the Algae pass very
gradually into the Fungi through intermediate forms like
Vaucheria, Peronospora, Achlya, and Sporendonema, the
transition from the Fungi to the Lichens is equally easy.
LICHENS.
Lichens are dry plants, covering stones and rocks, or
creeping over trees, walls, and fences. They are found as
gray, brown, yellow patches; as wrinkled, leathery, horny
crusts (Fig. 108); and however unattractive, as a general rule,
in appearance, are of great importance in the economy of
nature, and therefore of interest to the botanist. The
Lichens are widely distributed, being found in the icy
recesses of Mont Blanc, amidst the recently poured-out
lava of Vesuvius, and crowning the summits of most
barren rocks. The Lichens, being aerial in habit, and more
insensible to changes in climate than any other plants,
survive and flourish where all other vegetation would
perish. The decaying parts of their bodies furnish the
subsoil in which future mosses, ferns, and flowering plants
can take root. Their importance, therefore, cannot be
over-estimated. A Lichen (Fig. 109) is made of threads,
and colorless and green spores. The threads resemble the
mycelium, or threads of a Fungus; the green spores
(gonidia) are like the spores of the Algae (the spores of
Fungi, being colorless, resemble the other spores). Most
Lichens derive their nourishment from the air. This
peculiarity is usually regarded as distinguishing them from
Fungi, which live parasitically on plants and animals. But
as certain forms of Fungi (according to Berkeley) are
BOTANY.
87
found on iron, lead, etc., certainly not living at the expense
of these metals, the distinction of the aerial nutrition of
Lichens from the parasitical of Fungi evidently docs not
hold good in all cases. The presence of green spores is
very constant, but their absence in forms like Alrothallus
makes Lichens of this kind undistinguishable from Fungi.
Lichens, as a rule, are aerial plants ; yet some forms are
always immersed in water, as in most Algae. The early
stages of many Lichens resemble so closely certain Algae
that botanists cannot separate them. The Lichens are
considered by most naturalists as standing between the
Algae and Fungi. According to Haeckel (“ Natural History
of Creation,” p. 416), “each Lichen is composed essentially
of two different plants, of a low form of Alga (Nostoc,
Protococcus) (Fig. Ill) and of a parasitic Fungus (Asco-
mycetes) (Fig. no), which is parasitic on the first, and lives
off the assimilated material which this furnishes. The green
chlorophyll-holding cells (gonidia), which one finds in every
Lichen, belong to the Alga. The colorless threads (hyphi),
on the contrary, which, thickly woven, form the principal
mass of the body of the Lichen, belong to the parasitic
Fungus. But always are both plant-forms — Fungus and
Alga, which are considered as belonging to different classes
— so firmly bound with one another, and so intimately
grown together, that every one regards the Lichen as a
single organism.”
Notwithstanding the differences in size, color, form,
reproduction, and habitat seen in this brief survey, the
structure of Algae, Fungi, and Lichens has always appeared
to be the same, cellular. When we compare plants appar-
ently so distinct as mushrooms, mildews, encrusting matter
of rocks, greenish layers of ponds, sea-weed, etc., the
closest examination rarely reveals more than a combination
of cells, no Alga, Fungus, or Lichen offering us the dis-
tinction of stem, leaves, vessels, or flowers observed in the
88
EVOLUTION OF LIFE.
higher plants. Botanists join, therefore, these three groups
in one division, the Thallophytcs or Cellular plants, a thallus
being an expansion of cells.
With the Thallophytes we leave the first division of the
vegetal kingdom.
CHARACE/E.
The Characeae are unique plants, including the Nitella
and Chara, which differ only in the structure of their tubes,
the Chara having a cortical layer in addition to the simple
tubes of Nitella. The Chara is found in ponds and ditches,
being composed of elongated tubes giving off at intervals
whorls of branches which look very much like small green
candelabra. The Chara (Fig. 112) is always an object of
interest to the microscopist, as exhibiting the circulation
of the chlorophyll, or green matter, the globules of which
may be seen ascending and descending along the sides of
the tubes. The Characeae in their structure and general
appearance resemble the Green Algae, while their repro-
ductive apparatus is more like that of the Mosses. This
consists of an orange-colored globule and an oval-shaped
nuclule. The globule (Fig. 112, C) bursting, a number of
spiral filaments come forth, which move about in the water;
the nuclule (Fig. 112, D), falling off in time, gives rise to a
new Chara. The globule and nuclule are supposed to be
the homologues of the reproductive organs of the higher
plants. The Characeae are isolated plants, seeming to be
the only remnant of a group once more numerous : they
stand on a boundary-line, so to speak, separating the Green
Algae from the Hepaticae. Probably extinct plants allied
to the Chara gave rise to the Hepaticae, and indirectly
through them to the Mosses and Ferns.
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BOTANY.
S 9
IIEPATICZE.
The Hepaticse, commonly known as Liverworts, are small
plants of varied forms found on damp ground, moist parts
of trees, or floating on the water. The lowest representa-
tives consist simply of a single layer of cells forming a
green membrane or patch, as in Anthroceros (Fig. 113), or
there is a double layer of cells, as seen in Sphaerocarpus.
In Marchantia (Fig. 114) the layers of cells are more
numerous and thicker than in the lower forms just men-
tioned, and the upper and lower surfaces are clothed with
a skin or epidermis, on the upper surface of which stomata
are seen; stomata are holes in the epidermis through
which air can pass from the outside of the plant to the
inside. In the middle of the frond or body of the Riccia
a distinct line or midrib is seen. This line in the Junger-
mannia (Fig. 1 16) becomes a well-defined stem, with leafy
appendages on each side. The Jungermanniae are therefore
the first plants in which we meet with the structures so
characteristic of higher plants, viz., the stem and leaves;
the apparent stems of the Fucoidae and Floridae being
composed only of a greater number of denser cells, not
essentially different from the adjacent parts either in struc-
ture or function. While the higher forms of Liverworts, in
having stems and leaves, exhibit a marked progress, the
lower forms in their cellular structure differ in no way from
the Green Algae. The structure of the reproductive appa-
ratus, however, in all Liverworts is much more complex
than that of the Algae. In the concave receptacles, sup-
ported by stalks, as seen in Marchantia (Fig. 114), are
found oval cellular bodies, the so-called Antheridia (Fig.
120, C ), which contain spiral filaments (Fig. 120, D) capable
of moving after having escaped from the Antheridia. The
convex-lobed bodies terminating the stalks of the same
plant (Fig. 1 15) contain flask-shaped bodies, the Archegonia
90
EVOLUTION OF LIFE.
(Fig. 120, A), inside of which will be found the embryo-
cell (Fig. 120, B). The embryo-cell, after the contact of
the spiral filament, is changed into the Sporangium, or case
which contains the spores, from which the new plant will
be developed.
The Hepatica;, or Liverworts, seem to be transitional
plants, leading up from the Green Algae and Characeae to
the Mosses and Ferns, they representing, probably, the
common stem from which the roots of the Mosses and
Ferns have diverged.
MOSSES.
The beautiful green velvety carpeting of woods com
monly known as Mosses (Figs. 1 1 8, 1 19), growing most
luxuriantly in damp, shady places, so useful from freely
absorbing and retaining moisture, to be given out in time
of drought, is made up of small delicate plants, each indi-
vidual consisting of a stem and leaves, exhibiting under a
low magnifying power a great variety and beauty of form.
While Mosses, in the arrangement of their stem and leaves,
differ greatly from the Jungermanniae, one group of them,
the Hypoterygiae (Fig. 1 17) furnish perfectly the transition ;
the erect stem and leaves of the Hypoterygiae agreeing in
structure with the procumbent one of Jungermanniae. The
reproductive apparatus of the Hypoterygise, however, is
like that of Mosses generally. This consists, as in Hepaticae,
of Archegonia and Antheridia. The Archegonia are flask-
shaped bodies containing the embryo-cell. The Anther-
idia (Fig. 120, C) are oval cellular bodies, having inside
the spiral filament. (Fig. 120, D.) The embryo-cell (Fig.
120, B), by the contact of the spiral filament, is changed in
Mosses, however, into a stalk supporting an urn-shaped
body. In this urn are produced the spores, which do not
at once reproduce the new Moss, but protrude a confervoid
growth, the so-called Protonema, a structure very like that
FERN GROWING FROM PROTHALLUS
BOTANY.
91
of an Alga or Fungus. In its Protonema stage the Moss
is only a cellular plant, a Thallophyte. Later, out of the
Protonema is developed the true Moss, with its stem,
leaves, and reproductive organs.
The Mosses have probably descended, through forms like
the Hypoterygiae, from the Jungermannise.
FILICALES.
The so-called Horse-tails of ditches, etc., our common
Ferns, the aquatic plants known as Pillwort and Club-
moss, are generally considered by botanists as representing
four different orders of the class Filicales. While Ferns,
etc. are as highly organized as Mosses, in having stems
and leaves, the vascularity of their stem exhibits a consid-
erable advance as compared with the same structure in
Mosses. The Fern and Horse-tail, though differing in
appearance, are usually associated, since their reproduction
is the same. The Pillwort and Club-moss, agreeing in
their reproduction, differ, however, from that observed in
the Horse-tail and Fern: hence their frequent union. The
Filicales of the present day play an inferior part as com-
pared with those of past time. Tropical climates even do
not give us an idea of what the class once was, as regards
their size, variety, and importance in the economy of nature.
They are sometimes called Acrogens, or summit-growers.
We will examine now a little more closely the living
Filicales, leaving for the chapter on Geology the account
of those forms that have died out.
EQUISETACE/E.
The Horse-tail, or Equisetum (Fig. 121), is a very com-
mon plant, abounding in ditches, woods, marshes, etc., and
is readily distinguished by its very characteristic appear-
92
EVOLUTION OF LIFE.
ancc: though small in temperate regions, in the tropics it
attains a size of fifteen or sixteen feet. The Horse-tail is
composed of a series of hollow tubes joined end to end,
the articulations being separable, and these tubes are
marked externally by furrows running longitudinally. In
place of leaves, the Equisetum exhibits green-colored
branchlets; it has also rhizomes, or underground stems,
sometimes extending to the depth of many feet. The
spores are contained in a spike-shaped or conical cap, ter-
minating the stem of the plant ; the spores produce a
cellular structure, the Prothallus, from which the new
Equisetum will be developed: this kind of reproduction is
seen in the Ferns, of which we will presently speak. There
is found in all parts of the Horse-tail such a large amount
of silex that the plant becomes important in a commercial
point of view, it being much used for polishing.
FILICES
Ferns are not only interesting to botanists on account
of their structure and reproduction, but also equally attract-
ive to the laity, their graceful stems and exquisite leaves
furnishing specimens for the greenhouse and ornaments
for the parlor. These beautiful plants are abundantly
found in damp, shady places, though a damp soil and moist
climate seem more necessary than shade for their luxuriant
growth. If an oblique section (Fig. 123) of the stem of a
Fern be magnified, the most important features observed are
the vessels or ducts running down the middle of the stem,
which have in them some woody tissue. So characteristic
is the presence of vessels in the higher flowering plants,
that Ferns, from having these organs, are often associated
with them. At certain seasons there are seen, generally
on the under surface of the leaf of a Fern, small bodies
usually supported on stems, known as Sori. (Fig. 124, a.)
BOTANY.
93
Each sorus, when magnified, is seen to consist of numerous
capsules (theefe); these capsules contain the spores. The
spores are angular-shaped bodies (Fig. 125, a), with an
external coat of a brownish color, which is variously marked,
like the pollen of higher plants. The spores, when placed
in a damp surface and exposed to the proper influences of
heat and light, germinate; that is, the angles of the spore
are rounded off, the internal coat of the spore is then pro-
truded, becoming the root-fibre (Fig. 125, /;); the outer coat
of the spore bursting, the inner coat grows in an opposite
direction to that of the root-fibre as an elongated filament
(Fig. 125, e); cell after cell is added in a longitudinal
direction, the plant soon resembling an Alga. After a
time, however, the cells are produced transversely as well
as longitudinally, resulting in the formation of a flattened
leaf-like expansion (Fig. 125, d), a cellular structure, the
so-called Prothallus, which can scarcely be distinguished
from a young Marchantia. In this Prothallus are developed
Archegonia and Antheridia : the union of the embryo-cell
of the Archegonia and the spiral filament of the Antheridia
gives rise to the new Fern, which may be seen growing
out of the Prothallus (Fig. 126), which soon passes away.
These two stages in the life of a Fern represent two distinct
plants. The Prothallus stage is a cellular plant closely
resembling a young Marchantia, which is later transformed
into a stem- and leaf-bearing plant. The growth of the
Horse-tail offers the same metamorphosis; spores pro-
ducing a Prothallus from which the Horse-tail is developed.
While the Mosses are probably the posterity of Junger-
mannia-like plants, the Ferns have most likely descended
from forms allied to Marchantia ; this view being based
on the fact of the Fern passing through a Marchantia-like
stage, with similar reproductive organs.
94
EVOLUTION OF LIFE.
RHIZOCARP/E.
The Rhizocarpae, a group of minute water-plants, are
represented by four genera found in different parts of the
world, of which the Pillwort and Pepperwort are probably
the best-known, these plants being rather botanical curiosi-
ties than objects of every-day attention. They are incon-
spicuous plants, growing in the mud at the edges of pools,
or floating about in stagnant water. A plant of this group
(Marsilea) (Fig. 127) consists of a creeping stem; from the
upper side rise stalks ending in leaves, from the lower hang
roots; at the base of the stalks, near the roots, are seen the
spore-cases (sporocarps) : hence the name of this order,
Rhizos- (root) carpae (fruit). The spore-cases of the Pill-
wort (Pilularia) and Pepperwort (Marsilea) contain both
small and large spores. In Salvinia and Azolla the large
and small spores have each their special spore-case. The
importance of this arrangement of the reproductive appa-
ratus in Salvinia and Azolla will appear when speaking
of the flowering plants. The development of the future
Rhizocarp from the large and small spores is the same as
that observed in the Club-mosses, to which we will now turn.
LYCOPODIACE^E.
The Lycopodiaceae(Fig. 1 28), or Club-mosses, are delicate
creeping plants, producing leafy-like branches, resembling
in their general appearance Mosses, though differing from
them in structure and manner of reproduction. The Club-
mosses of the present day are small plants ; this was not
always the case, the order being represented in past time
by trees, attaining the height of sixty feet, with gigantic
roots, giving the vegetation of that period a very charac-
teristic appearance. The stem of the Lycopodiacem exhibits
the same vascular and cellular structure noticed in the
BOTANY.
95
Ferns. In the Isoetes (a Lycopod) we see, for the first time
in our brief survey of the vegetal kingdom, a stem present-
ing woody layers one inside of the other, one of the distin-
guishing features of trees like the Oak, Walnut, Chestnut,
Pine, Fir, Cycas. This fact is an important one, as will
appear later. The reproduction of the Lycopodiaceae and
Rhizocarpae differs from that of any plants of which we
have yet spoken. There are found in the Lycopodiaceae
both large and small spore -cases, of which the former
(Fig. 128) contain only four large spores, the latter (Fig.
128) many small ones. In Selaginella the leaves are spike-
shaped, and at the base of the leaf is found either a large
or small spore-case. Each spore of the large spore-
case may produce within its cavity a Prothallus like that
of the Fern ; but it will be remembered that the Prothallus
of the Fern is produced outside of the spore, whereas the
Prothallus of the Lycopod is developed inside the large
spore. In the Prothallus of the Lycopod, Archegonia, with
their embryo-cells, alone are found ; the Antheridia, with
their spiral filaments, coming only from the small spores.
Finally the large spore bursts, freeing its Prothallus. The
spiral filament of the Antheridium of the small spore,
coming in contact with the embryo-cell in the Archegonium
in the Prothallus of the large spore, gives rise to the new
Lycopod, which, in Selaginella, is a little stem supporting
two leaves, one on each side. (Fig. 129.) This kind of
reproduction is seen in the Rhizocarpae. By comparing
the reproduction noticed in the Fern, Horse-tail, Rhizocarp,
and Lycopod, the following series becomes apparent: the
Ferns and Horse-tails produce one kind of spore; from
this spore is developed a Prothallus containing both Arche-
gonia with their embryo-cells, and Antheridia with their
spiral filaments. The Rhizocarpae and Lycopodiaceae
produce two kinds of spores, large and small ; in the
Pillwort and Pepperwort the large and small spores are
96
EVOLUTION OF LIFE .
found in the same spore-case, but in the Salvinia and Azolla
the large and small spores have their special spore-cases,
as in the Ly copod iaceae; the large spore alone develops the
Prothallus with Archegonia and embryo-cells, the small
spores alone producing Antheridia with spiral filaments.
The reproduction, however, of the Horse-tail, Fern, Rhizo-
carp, or Lycopod is always due to the contact of the spiral
filament of the Antheridium with the embryo-cell of the
Archegonium, the new plant growing always from a Pro-
thallus. The Lycopodiacese appeared on the earth later
than the Ferns, and have probably come from them, being
closely related at the present time by intermediate forms
(Opioglossae). The Rhizocarpai may be regarded as aquatic
Lycopods. The structure of the stem and reproductive
apparatus, and the form of the embryo, are striking proofs
of the truth of the view that the Lycopodiaceae are the inter-
mediate forms, the links uniting the Flowerless and Flow-
ering plants. The importance of the facts just mentioned
will be better appreciated when the Lycopodiaceae are com-
pared with the simplest of flowering plants. We leave now
the Flowerless plants, or Cryptogamia, and turn to the
Flowering plants, or Phanerogamia.
PHANEROGAMIA.
Flowers, among the most beautiful of nature’s works,
are always interesting to the laity and the botanist, offering
objects of ornament and beauty to the one, and subjects for
study and admiration to the other. The flower is the
reproductive apparatus of the higher plants, made up of
the organs by which the seed is produced, fertilized, and
converted into the embryo plant. If we examine the
flower of the Violet (Yellow Violet) (Fig. 130), the green
cup-like arrangement of leaves first deserves our at-
tention; this is known as the calyx, and the leaves com-
DICOTYLEDON MONOCOTYLEDON
BOTANY.
97
posing it are called sepals. Within the calyx is seen
another whorl of yellow leaves, known as petals; their
union forms the corolla. Springing from the middle of the
calyx and corolla, and standing erect, is seen a delicate
tube, the pistil. Surrounding the pistil, and differing from
it in appearance, are found the stamens. If the pistil is
examined separately (Fig. 132), it is seen to be composed
of the following parts : the head or stigma, the stalk or
style, and the ovary. The ovary contains the ovule, or
future seed, and if the ovule be magnified it is seen to con-
tain the embryo-sac, and within the embryo-sac is found
the germinal vesicle. The germinal vesicle is the rudiment
of the future plant. The stamens, or stalks, surrounding
the pistil, are composed of the stems or filaments support-
ing- the anthers or little heads. The anthers contain the
pollen, or fertilizing principle. Suppose the supreme power
of Turkey to be a woman, and the Sultana to have a harem
of men, such a condition of social life would represent
what is seen in the Violet, or better in a section of the
Morning-glory (Fig. 1 3 1 ), where the imaginary Sultana is
realized in the pistil, the harem of men in the stamens.
The pollen produced in the anthers finds its way to the
stigma, or head of the pistil; from the head it passes down
through the style, or tube of the pistil, until it reaches the
ovary. Piercing successively the ovary, ovule, and embryo-
sac, it finally comes in contact with the germinal vesicle.
From this moment the life of the new plant begins in the
formation of the embryo. The flowers of the Violet and
Morning-glory serve to illustrate the reproductive apparatus
of many plants. If, however, the flower of the Goose-foot
(Chenopodium) (Fig. 133) be compared with that of the
Violet, the absence of the corolla at once strikes the atten-
tion ; and if the flowers of the Bread-tree, Pine, etc. (Fig.
I35> a , b) be now examined, calyx and corolla are both
found wanting. Further, in trees like the Pine, etc. there
7
9 8
EVOLUTION OF LI FIT
is no ovary, the ovule being exposed to view resting on the
edge of the leaf (Fig. 135, a ) ; the ovule is fertilized by the
falling of the pollen, style and stigma being absent as well
as ovary. Plants of this kind are called, therefore, Gym-
nospermse, or naked seeds; whereas those having an ovary
are known as Angiospermae, or seed-vessels. The flower-
ing plants divide naturally, therefore, into these two groups.
To the Gymnospermae, or plants with naked seeds, belong
the Bread-tree, Zamia, and Cycas (Cycadae), the Pine, Kir,
Cypress, Juniper, Cedar, and Yew (Coniferae). Among the
Angiospermae, or plants whose seeds are contained in seed-
vessels, are found the forest-trees, fruit-trees, grasses, roses,
violets, etc.
CYCAD./E.
The Cycadae are small palm-like trees (Fig. 137), or
shrubs with unbranched stems, found principally in the
tropical regions of Asia and America. The Bread-tree
belongs to this order, supplying the Caffre bread; the
Cycas of Japan produces, in its stem, a starchy matter,
which is collected and eaten like sago. The Cycadae are
sometimes called Palm-ferns, from their resembling Ferns
as well as Palms. In past time the order was much more
numerous than at present. The so-called flower of the
Cycadae is very simple. The naked ovules are attached to
the bases of contracted leaves: these leaves in some cases
overlap each other. The stamens are found on separate
leaves, which overlap each other, forming a cone. The
leaves containing the ovules and stamens are found on
separate plants, the series being quite distinct in the Cycadae
The reproductive apparatus of the Cycadae agrees essen-
tially with that of the Salvinia, noticed in speaking of the
Rhizocarpse, the ovule of the Cycas being homologous
with the -large spore of Salvinia, the pollen corresponding
to the small spores. As the reproduction of the Cycas
BOTANY.
99
from the ovule, so far as known, is the same as that of the
Coniferae, we turn now to that order.
CONIFERS.
The Coniferae, or cone-bearing trees, are so called from
their fruit being in the form of cones, as in the Pines;
“these cones are made up of flat scales regularly over-
lapping each other, and pressed together in the form of a
spike or head ; each scale bears one or two naked seeds in
its inner face.” “The pollen is contained in the substance
of a body that retains in some degree its leafy type, and an
assemblage of such bodies forms the ‘catkin.’” In the
Cypress we have cells (corresponding to stamens) at the
edge of the leaf. The leaves of Selaginella (a Cycopod),
with their large and small spores (Figs. 136, 137), are as
much flowers as the leaves of Coniferae with their organs.
The Coniferae are invaluable to man, as including the most
important of the timber-trees of cold countries, and furnish-
ing the turpentines, resins, pitch, tar, and Canada Balsam.
Among the Coniferae are found the Pines, Fir, Spruce,
Cypress, Cedars, Larch, and Juniper. At certain seasons the
ovule of Coniferae develops in its interior a mass of cells,
the Endosperm ; later in this Endosperm appear Corpuscles;
within the Corpuscle is developed the Embryonic vesicle.
The Ovule, Endosperm, Corpuscle, and Embryonic vesicle
are to the Coniferae and Cycadae what the Large Spore,
Prothallus, Archegonium, and Embryo -cell are to the
Lycopods, the pollen of the Gymnospermae corresponding
to the small spores of the Lycopodiaceae : the reproductive
organs of Lycopodiaceae and Gymnospermae are, therefore,
essentially the same. The higher plants differ from these
orders in that the embryo-sac contains the embryo-cell only;
whereas, in Lycopodiaceae and Gymnospermae, a Prothallus
or Endosperm with Archegonia or Corpuscles is produced.
IOO
EVOLUTION OF LIFE.
the embryo-cell appearing in the Archegonia or Corpuscles,
to which there is nothing to correspond in the higher
plants, which necessarily want the Prothallus or Endosperm
as well. After the contact of the germinal vesicle and the
pollen, the life of the new Gymnosperm begins in the
formation of the embryo, which consists of a stem or
radical supporting two or more leaves (Figs. 139, 138, a),
called cotyledons. The embryo of the Cypress in its two
cotyledons recalls that of Selaginella (a Lycopod). Those
plants whose embryos have only one leaf (Fig. 140, a) or
cotyledon are called Monocotyledonous, while those hav-
ing two are known as Dicotyledonous. The Dicotyledonous
plants further offer in their stem the destruction of pith,
wood, and bark, and increase the diameter of their stem by
layer after layer (Fig. 141, 1, 2, 3) of wood being added,
the new layer being deposited between the old layer and
the bark, this new layer growing at the expense of the
Cambium, a layer (Fig. 141, C) found always between the
last and most external layer of wood and the bark. Such
plants are called outside growths, or Exogens. The Mono-
cotyledonous plants, however, do not present, in their stem,
the difference of pith, wood, and bark so w r ell defined as in
Exogens; the new wood being added in bundles inter-
mingling with the old, and deposited principally towards
the centre of the plant. (Fig. 142.) Such forms are* called
inside growths, or Endogens. The wood of an Exogen is
oldest and hardest in the centre, whereas the wood of an
Endogen is newest and softest towards the centre. The
increase in the diameter of the trunk of an Exogen, as in
the Oak, is indefinite; the stem of the Endogen, as in the
Palm, is limited as regards its diameter, the tendency being
rather to grow upwards. In speaking of the Lycopodiaceze.
Cycadae, and Coniferze, we have noticed they have important
features in common: the reproductive apparatus is essen-
tially the same; the form of the embryo in some genera
BOTANY.
lOI
(Selaginella, Cypress) is two-leaved, or dicotyledonous ;
finally, there must be added to these facts the additional one
of the Cycadae and Coniferae being outside growers, and of
a similar exogenous mode of growth being seen in Isoetes
among the Lycopodiaceae. The Lycopodiaceae are, therefore,
so closely and intimately allied with the Cycadae and Coniferae
that the question naturally arises, Does there really exist in
Nature such a distinction as that of Flowerless and Flower-
ing plants? The reproductive apparatus of the Lycopo-
diaceae is so similar to that of the Cycadae and Coniferae
that it is impossible to say where the Flowerless plants
end and the Flowering begin. In the first page of this
chapter we used purposely the expression, translating
Cryptogamia “ flowerless,” Phanerogamia “ flowering.” The
word cryptos , literally translated, is “obscure,” “concealed;”
phaneros , “apparent,” “evident;” gamos referring to the
organs of reproduction. Translating literally, the Crypto-
gamic plants are those in which the reproductive organs
are not absent, but only obscure; the Phanerogamia, those
in which the reproductive organs are very evident in the
form of flowers. The difference between the higher Crypto-
gamia and Phanerogamia is not one of kind, but only of
degree, the apparent gulf between these two divisions being
bridged over by the Lycopodiaceae, Cycadae, and Coniferae.
The Linnsean classification is the best yet offered, express-
ing the real nature of plants. The Angiospermae, as pre-
viously stated, are those flowering plants whose seeds have
a seed-vessel: their embryo is either Monocotyledonous or
Dicotyledonous. The one-leaved or Monocotyledonous
form of embryo is universally associated with the endogen-
ous, or inside mode of growth, usually with a threefold
arrangement of leaves. The Dicotyledonous or two-leaved
embryo, on the contrary, characterizes all outside growers
or Exogens, accompanied usually with a fivefold arrange-
ment of leaves. The Monocotyledons include the Palms
102
EVOLUTION OF LIFE.
(Fig. 143), Bananas, Orchids, Lily, and the Grasses. Among
the Dicotyledons are found the Oaks, Elms, the fruit-trees,
and the most beautiful flowers. The flower of the different
kinds of Dicotyledons offers an interesting ascending series.
The flower of the Spurge, or Euphorbia, consists of only a
stamen or a pistil, kno^n as Achlamydeous, the flower
being called accordingly staminate or pistillate. A slight
progress is seen in the flower of the Goose-foOt, Fig, Mul-
berry, Elm, etc., in which, however, the corolla is still
undistinguishable from the calyx. Such flowers are called,
therefore, Apetalae: the flowers of the Monocotyledons are
of this kind. In the Bean, Clover, Violet, Geranium, etc.,
the corolla and calyx are distinct, but the petals forming
the corolla are still more or less separated, hence they
are known as Diapetalae ; in the Gentian, Elder, Ash,
Morning-glory, etc., the petals have united; they are known,
therefore as Gamopetalae. How the different orders of the
Phanerogamia are related to each other is the last ques-
tion which yet remains . unanswered. The structure and
reproductive apparatus of the Cycadse and Coniferse would
lead us to suppose that they appeared on the earth before
the Monocotyledons or Dicotyledons. This view is con-
firmed by geological evidence, since the fossil Cycadse and
Coniferae are found in great profusion at a much earlier
period than that in which the Monocotyledons or Dicoty-
ledons first appeared. The Cycadae and Coniferae are
probably the posterity of a common ancestor nearly allied
to the Lycopodiacese. Among the Coniferae there is an
order, the Gnetacese, or the jointed Firs, whose structure
links them on to the Monocotyledons and Dicotyledons.
Some extinct Conifer, allied to the jointed Fir, was the
probable common progenitor of these two orders, of which
the Dicotyledons are the most complex, both as regards
the structure of the stem and flower.
BOTANY.
103
RESUME.
Beginning with the most minute and simplest of plants,
such as are found in every pond and ditch, and comparing
them with the different sea-weed, Fungi, etc., we found,
notwithstanding minor differences, that their structure was
essentially the same, cellular; offering no trace in their
organization of stem and leaves. Passing from the cellular
plants, through transitional forms, to the Liverworts, we
noticed that the lower forms of this are still cellular, while
the higher exhibit the beginning of a separation into stem
and leaves. Forms like these lead the way to the Mosses,
in which the stem and leaves are well defined. The Ferns,
while agreeing with the Mosses in having stem and leaves,
offer an advance in their organization, since their stem
contains vessels with more or less woody tissue. Passing
from the Ferns to the closely allied Club-mosses, we found
in them the links binding the Flowerless with the Flower-
ing plants. Taking up next the Cycadse and Coniferm,
we saw how naturally they preceded the Endogens and
Exogens. Finally, in the different kinds of Exogens we
saw an ascending series, as illustrated in the flower of the
Spurge, Goose-foot, Violet, Morning-glory. Our brief
survey of plants may be expressed in the following conclu-
sion : The vegetal kingdom may be represented by a tree,
of which the stems and branches are the classes, orders,
etc. The trunk of this tree, being composed of the simplest
forms, grows gradually upwards into more complex ones,
finally developing the noblest >of trees, the most beautiful
of flowers. We hope to show in our next chapter that the
petrified remains of the animal and vegetal kingdoms offer
such a progress from lower to higher forms.
VEGETAL KINGDOM.
104
EVOLUTION OF LIFE.
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BOTANY.
105
TREE OF VEGETAL KINGDOM.
Monocotyledons.
I
Pal race.
I
Cycadae.
Rliizocarpae.
Lycopodiaceae.
Musci.
Gamopetalae.
I
Diapetalae.
I
Apetalae.
I
Achlamydeae.
I
Dicotyledons.
I
Gnetaceae.
.1
Coniferse.
Filices.
Equisetaceae.
Hepaticae.
I
Characeae.
Florida;.
Fucoidae.
Lichenes.
Confervoidae.
I
Protophyta.
I
Vegetal Monera.
Fungi.
GEOLOGY.
No study illustrates better than Geology not only the
advantage but the absolute necessity of general knowledge
for the thorough understanding of any particular subject.
Geology means literally a discourse on the earth. The
student of so vast a theme ought naturally therefore to be
familiar with at least the general conclusions offered by
Astronomers, Physicists, Chemists, Mineralogists, Botanists,
and Zoologists, so far as they relate to the history of this
planet, since by astronomical data we picture our earth as a
once gaseous, chaotic mass. The study of the cooling of
heated bodies under pressure, implying a knowledge of the
laws of Heat and Chemistry, furnishes the clue to the ex-
planation of the origin of many formations. Mineralogy
distinguishes the different rocks of which the crust of the
earth is composed, while Botany and Zoology supply the
means by which the life of bygone days is revivified,
enabling us to interpret the structure and relations of plants
and animals long since extinct. Geology, therefore, is not
a separate science, since it consists only of the conclusions
of many sciences applied to the investigation of the past
and present history of the earth. As three-fourths of the
earth are covered with water, with our present resources
only a very small portion is susceptible of geological ex-
amination. And notwithstanding the great number of
surveys and scientific expeditions which have been made
during the present century, with the exception of Great
( i°6 )
GEOLOGY.
107
Britain, Canada, parts of Europe and the United States,
the geology of the accessible portion, even, of the earth is
still very little known, large parts of Africa, Asia, and
South America being as yet, comparatively speaking, un-
explored. Civilization, through its railroad-building, tunnel-
ing, canal-making, and mining operations, furnishes a large
amount of the material on which the Geologist bases his
science. Through agencies of this kind, rocks have been ex-
posed which otherwise would have perhaps remained forever
concealed from view. Through the excavating incidental
to mining and tunneling, there have been discovered the
remains of plants and animals long since extinct, the relics
of an indefinitely remote past, the existence of which had
not been previously even dreamed of. The detritus brought
down by rivers, and the consequent filling up of their
mouths, as seen in the deltas of the Mississippi and the Nile,
with the preservation in the mud, etc. of the coral stones,
shells, skeletons of fish, etc. which lived and died in the
vicinity, give one a good idea of the manner in which
petrified organic remains or fossils may have been preserved
in the rocks. While in certain rocks of this kind the fossils
are found in great profusion and in a very excellent state
of preservation, in others very few occur, or only a frag-
ment may have escaped destruction. This is often, how-
ever, so characteristic that the comparative anatomist
can reconstruct the whole skeleton from a single bone,
a knowledge of the correlation of forms enabling the
osteologist to infer from the structure of the foot the
nature of the jaws, teeth, etc., of the extinct animal. Many
such inferences might be mentioned, all of which, while
commanding praise as illustrating the osteological knowl-
edge of the anatomist, scarcely merit the astonishment
which they invariably excite. While many rocks seem
to have experienced but little disturbance since their origi-
nal deposition, the different layers or strata of which they
ioS
EVOLUTION OF LIFE.
are composed being easily distinguishable, the convulsions
to which others have been subjected have been so great,
and the effects of heat so intense, that no sign of such
stratification is visible, if it ever existed. The old Geologists
resembled the knights who fought about the color of the
shield. The early German school, influenced by the char-
acter of the rocks in that part of the world, attributed a
great deal to the action of water ; while the Scotch school,
equally impressed by the features of the formations in their
country, attached great importance to the effects' of heat.
Hence arose the sects of the Neptunists and Plutonists.
Both were right in attributing the formation of the rocks
in their respective countries to the action of water and heat
Both were wrong in applying to the whole world conclu-
sions drawn from such local data. Modern Geologists
steer a middle course, — avoiding these extremes, — consider-
ing the effects of the combined action of water and heat,
as well as admitting the influence exerted by these agents
separately. Rocks the origin of which is supposed to be
due to the gradual deposition under water, in layers or
strata, of the materials composing such formations, are called
Aqueous Rocks ; while those of which the structure clearly
testifies to the action of heat in producing them are known
as Plutonic Rocks. Finally, the Metamorphic Rocks illus-
trate the alternate action of water and heat. Geologists
classify rocks according to their mineral composition, their
organic remains, and the order in which they follow or
overlie one another. The Geologist, starting in Canada,
and traveling through New York and Pennsylvania, notices
continually as he advances southward the change in the
minerals composing the rocks, and the different aspects of
their organic remains. Thus, in Canada and the east of
New York, granite, gneiss, and syenite are common minerals.
These rocks were originally called Azoic, or without life;
improperly, however, as within a few years the Eozoon, or
GEOLOGY.
109
Morning being, was discovered, so called from representing
the very simple beings which first appeared on our con-
tinent during the dawn of life. The term Azoic is still
retained by Geologists as meaning a scarcity of life, not
implying, as formerly, entire absence of it. Continuing his
journey, our Geologist soon reaches the Potsdam Sand-
stone, abounding in characteristic fossils, of which the
Brachiopod shells and Trilobites, extinct Crustaceans, are
very common. Passing by the town of Oriskany, he comes to
what is known as the Schoharie Grit, in which the remains
of fishes are first found. Finally, he reaches Pennsylvania,
abounding in coal, with its ferns and traces of reptiles. If he
goes over to New Jersey, he finds in the chalks the reptiles
more abundant. To see the higher forms of life in pro-
fusion, he must turn to the West, Nebraska and Dakota
having furnished the remains of deer, rhinoceros, hyena,
lion, etc. The rocks of Canada and New York are the
successive beaches left dry by a retreating ocean. This is
very evident from the manner in which the rocks follow
each other, the ripple-marks still visible on them, and their
marine remains. The animals and plants found in the rocks
of New York and Pennsylvania, from bearing the stamp of
age, are called Paleozoic, or old beings, and the age in
which they lived is known as the Primary. The fossils of
New Jersey, though still old, are more modern in their
appearance than those of New York; they are called,
therefore, Mesozoic, or middle-aged beings ; the rock con-
taining them forming, with some others not well represented
on our continent, the Secondary Age. The Cenozoic, or
recent beings, those of Nebraska, for example, lived during
the Tertiary Age. Not only are the fossils invaluable to
the Zoologist and Botanist, as representing the life of the
past, but they are equally important to the Geologist, as
we have just seen ; his classification of the rocks is princi-
pally based on the extinct remains which they contain. The
I 10
EVOLUTION OF LIFE.
Primary, Secondary, and Tertiary Ages, with their charac-
teristic fossils, according to many Geologists, were not
confined to America, but extended all over the globe ; the
whole earth having passed at the same time successively
through the Primary, Secondary, and Tertiary Ages. Some
few Geologists do not accept this onion-coat hypothesis,
which supposes that similar rocks, with similar remains,
were deposited at the same time all round the earth, like
the layers in the coat of an onion. With all deference to
Geologists, let us examine the tests used for determining
the time of the deposition of foreign rocks as compared
with our own. The test of having similar minerals, when
applied to elucidating the age of foreign rocks as compared
with those on this continent, is worthless, since the chalk,
sandstone, etc. of which the rocks are composed are form-
ing in all ages; while a determination of the age of rocks,
based on the order in which they follow or overlie one
another, — when applied, for example, to New York and
England, separated by an ocean, — to say the least, is very
unreliable. The third test, that rocks having similar
organic remains are of the same age, considered by most
Geologists as settling the question, whenever such com-
parisons are possible, may be as fruitful a source of error
as the view that similar minerals deposited in the same way
are of the same age. Nor does, the reverse of this propo-
sition hold good, that rocks are of a different age because
they contain different fossils. Suppose, for example, that the
western part of North America and Australia were gradually
to sink into the sea, as parts of the world are now doing,
and then slowly to rise again, the Geologist of an indefinitely
remote future might argue, because he found many fossil
pouch-bearing animals in Australia, and the bones of an
extinct human race in America, that the Kangaroo was not
contemporaneous with the Indian. From the distribution
of plants and animals at the present time, we know that
GEOLOGY.
1 1 1
remote parts of the earth have very different animals ;
the preservation of organic remains at the mouth of the
Mississippi being no index of what is going on at the
mouth of the Ganges. While it is possible, it is certainly
not proved by the structure of the rocks, their deposition,
and organic remains, that the whole earth has passed at
the same time successively through the Primary, Secondary,
and Tertiary Ages. The limits of this essay do not admit
of the further discussion of this subject; nor, indeed, is it
necessary, as the question has been thoroughly argued
by Herbert Spencer in his “ Illogical Geology.” The dis-
putes of the Neptunists and Plutonists ought to be a
warning to Geologists not to apply generalizations, drawn
from limited data, to the whole earth. In the present state
of Geology we should receive all conclusions with great
caution, being prepared at any moment to have them
modified or even disproved by future research. Notwith-
standing the difficulty of obtaining fossils, the injuries they
often have received in being removed from the rocks, that
many are lost or destroyed through the ignorance of the
workmen who are often the first to find them, together
with the fact that the chance of plants and animals being
preserved is very small, remembering how the remains of
an animal, dying at the present day, are picked to pieces, get
separated, and are often finally destroyed, — yet the museums
in different parts of the world contain numerous organic
remains on which is based the science of extinct plants
and animals, or Paleontology, the conclusions of which
science are important proofs of the truth of the theory of
the evolution of the higher forms of life from the lower.
The opponents of the transmutation of species argued
fifty years ago, If the higher forms have descended from
the lower, where are the missing links ? Paleontology has an-
swered that objection by supplying the missing links, such as
the intermediate forms which bind together the Rhinoceros
I 12
EVOLUTION OF LIFE.
and the Horse, the Hippopotamus and the Pig, the Whale
and the Seal, the Reptiles and Birds, the Ganoid fishes and
Batrachia, etc. Not only are the fossils invaluable, there-
fore, to the Evolutionist without reference to their age, but
the order in which they have appeared, and their relative
age so far as it is possible to determine it, are in perfect
harmony with the conclusions we have drawn from the
structure of living plants and animals. Remembering the
uncertainty attached to the absolute and relative age of
rocks, let us examine the Primary, Secondary, and Tertiary
Ages through which North America has probably succes-
sively passed, without reference to the relation these Ages
bear in time to the corresponding parts of Europe, etc.
Geologists subdivide the Primary, Secondary, and Tertiary
Ages into periods (epochs) more or less characterized by
their fossils.
AGE OF MOLLUSCA AND ALGA2.
Passing from the Azoic rocks, in the northern part of the
State of New York, through the Potsdam region, to Tren-
ton Falls, southwardly to the Helderberg Mountains near
Albany, and eastwardly to Niagara, the immense number
of fossil shells, particularly Brachiopods (Fig. 145), attracts
the attention of the traveler. The Brachiopods of the
present seas are few and far between, whereas the sea of
that most ancient period was characterized by shells of
this order; the remains of other Mollusca are found, but
much less abundantly as compared with those of Brachio-
pods. The seas of this period must have swarmed with
Crinoids, from the great number of them found petrified,
their broken stems being known as Lily Stones (Fig. 146)
and St. Cuthbert beads. The young of the Comatula, long
supposed to be a distinct animal, the Pentacrinus (Fig. 42),
is the only known representative of the Crinoids at the
present time. With the Crinoids are also found abundantly
GEOLOGY.
”3
Star-fish. Associated with Brachiopods, etc., in great
profusion, and in an admirable state of preservation, are
the characteristic Trilobites (Fig. 144), an extinct order of
Crustacea, to which the nearest approach at the present
time is seen in minute Crustaceans like Cypris, favorite
objects with the Microscopist, or like the larva of Limulus.
In some genera of Trilobites, the different stages of their
existence have been very well followed out, the fossils
having been found perfect and in great profusion. The
rocks furnish evidence of the existence of worms at this
period, though, from the delicate nature of their bodies,
their remains are few and obscure. Certain impressions or
casts found in these rocks, known as Graptolites, are sup-
posed to have been made by animals allied to the Sertularia
of the present day, while the Niagara limestone consists
almost entirely of Coral. The period characterized by the
profusion of the remains of Brachiopods, Crinoids, and
Trilobites is known as the Silurian, called after that of
England and Wales, which derived its name from the
ancient tribe of Silures, once inhabiting those parts. The
plants of this period are Fucoidae, or brown sea-weed.
What conclusions can be drawn from the life of the Silurian
period in favor of the theory of the higher forms having
descended from the lower? We have seen that the animals
of this period were aquatic. Now, animals living in the
water are more simply and lowly organized than those living
on land. An animal subjected to the ever-changing
conditions of a land-existence needs a more complex
organization to fulfill its requirements than one living in
the comparatively unchanging sea. If the Development
theory be true, the water-animals, then, should have pre-
ceded the land-animals, the water-plants the land-plants.
Such has been the order of their appearance, according to
the testimony of the rocks. In the chapter on Zoology
we gave reasons for supposing that the Crinoids and Star-
8
EVOLUTION OF LIFE.
I 14
fish were the oldest of the Echinodermata, the Brachiopoda
of Mollusca, the Entomostraca of Crustacea, and that the
Worms preceded the Insects, etc. We have just seen that
the life of the Silurian, the most ancient period except the
Azoic, was characterized by these very orders, which are
the most simply organized of the respective divisions of
the animal kingdom, while the Fucoidae, or brown sea-
weed, found fossil in rocks of this period, belong to the
Algae, the simplest division of the vegetal kingdom.
Geological evidence confirms, therefore, not only in a
general way, but to an extent in detail not to be hoped for
from the nature of the subject, the view of the development
of the animal and vegetal kingdoms deduced from their
structure. The Silurian period is sometimes called the
Age of Mollusca and Algae.
AGE OF FISHES.
Passing from the Silurian period to the Devonian, so
called from the rocks of this formation having; been first
studied in Devonshire, England, we notice that while the
first half of the Devonian agrees in its main features with
the latter half of the Silurian, the latter half of the Devo-
nian, often called the Old Red Sandstone, offers evidence of
a progress in life, since its rocks contain the remains* of
fish, together with a few Ferns, Lycopods, and Conifers. The
remains of these plants are, however, only rarely found in
the Devonian ; the flora of this period, as well as that of the
Silurian, being more generally characterized by the presence
of Algae. The Fishes found in the Devonian period are
Sharks and Ganoids (Fig. 147). The Sharks belong to
the order of Cestraphori, or weapon-bearers, so named from
their dorsal fin being armed with a long spine; these spines
* Fish-remains found in the Silurian of England.
GEOLOGY.
1 1 5
are found fossil in great numbers; the teeth are in the form
of plates, giving the appearance of a pavement. The only
Shark at the present day having such teeth is the Ces-
tracion, or Port Jackson Shark, confined to the Australian
and China seas. The Ganoids, so called from their shining
plates or scales, must have abounded in the Devonian seas,
from the numerous fossil genera and species that have been
described. The only living examples of Ganoids at the
present time are the Sturgeons, Gar-pike, Amia of North
America, and the Polypterus of the Nile. In the chapter
on Zoology we argued, from their structure, that the Sharks
and Ganoids were not so highly organized as the Teliosts,
or bony fish of the present day, and concluded that there-
fore the Sharks and Ganoids had preceded the Teliosts in
their appearance on the earth. This view is confirmed by
what we have just seen, that the fishes that first appeared
were Sharks and Ganoids. Further, we noticed that the
Ganoids, while intermediate in many respects between the
Sharks and Teliosts, have many striking affinities with the
Batrachia and Reptilia. The fact of the Ganoids appearing
before the Bony Fish and Batrachia is a striking confirma-
tion of the truth of the view proposed, that the Ganoids
were the common stock from which the stems of the
Teliosts and Batrachia diverged. Calling attention to the
fact of the Silurian period, or Age of Mollusca, preceding
the Devonian period, or Age of Fishes, being in harmony
with the view of the higher forms of life coming from the
lower, we pass on to the Carboniferous period.
AGE OF ACROGENS AND BATRACHIA.
Pennsylvania, the great coal State, was principally formed
during the Carboniferous period, often called the Age of
Acrogens or Summit-growers, from eight-tenths of its
plants belonging to that order of the vegetal kingdom.
EVOLUTION OF LIFE.
1 16
Some years ago it was estimated, by Brown, that of the
one thousand species of plants found in the rocks of the
Primary Age, especially of the Carboniferous period, not
less than eight hundred and seventy-two were Fern-like,
the remaining species including about seventy-seven
Coniferae and Cycadae, forty Thallophytes, mostly Algae,
and about twenty undetermined plants. We see from this
estimate that the Fern-like plants were the characteristic
feature of the Carboniferous period, and must have flour-
ished in a much greater profusion than at the present day,
the Tree-ferns of tropical climates, even, giving one no
idea of the luxuriance of their growth in those ancient
days. Indeed, whole orders have passed away : the Cala-
mites and Asterophyllites, resembling the Horse-tails,
having no living representatives, while the Sigillariae and
Lepidodendrons have degenerated into the Club-moss of
our forests. As commonly known, the Lycopod of the
woods is a delicate moss-like plant: that of the Sunda
Islands is often twenty-five feet high. The Lepidodendrons
of the Carboniferous period, closely allied to living Club-
moss, attained, however, a height of from forty to sixty feet,
while their diameter at the roots was as much as twelve to
fifteen feet. The Sigillariae are similar in many respects to
the Lepidodendrons, often as high, though more slender.
The general aspect of the Carboniferous period was that of
a great Fern forest and a jungle of gigantic Club-mosses,
with some Coniferae and Cycadae; these, however, but
rarely seen, comparatively speaking. The gradual decom-
position of these plants resulted in the formation of the
vast coal-fields so characteristic of this period. In the
marshes of these forests first appeared the Batrachia
(Frogs, etc.), together with the Centipedes, the May-fly,
Locust, and Beetle orders among Insects. We see, there-
fore, that the tree of the development of life, as proposed
in the chapters on Botany and Zoology, is in perfect
GEOLOGY.
II 7
harmony with what we know of the Carboniferous fossils.
The gorgeous Ferns, in great variety, the Lycopod-like
plants, having attained the full maturity of their luxuriant
growth after this period, give way to the Cycadae and
Coniferae. The Ganoid fishes die out, their posterity, the
Batrachia, having appeared, soon to be replaced, how-
ever, by the Reptilia, while the Insects are still represented
by the lowest orders just mentioned. Following the Car-
boniferous rocks of the West in this country, and closely
resembling the Carboniferous period in its general features,
we meet the Permian, called after the ancient kingdom of
Permia in Russia. It is interesting to the Evolutionist as
furnishing the remains of the simplest reptiles, the Protero-
saurus having been found in the Permian rocks of Germany.
By looking at the tree of the development of the Reptilia,
it will be seen that the Proterosaurus is regarded as the
common ancestor of that group. The Silurian, Devonian,
Carboniferous, and Permian periods, taken together, con-
stitute the Primary Age, or age of most ancient beings.
AGE OF CYCAD/E AND REPTILIA.
The Secondary, like the Primary Age, is subdivided into
three periods, the Triass ic, Jurassic, and Cretaceous. These
three periods, while differing considerably in minor respects,
agree essentially in their plants and animals, being princi-
pally represented by Cycadae and Reptilia.
TRIASSIC PERIOD.
This period derives its name from the formation in
Germany being composed of three kinds of rock ; the
name, however, is one of only local application, the period
being often called in England and America the New Red
Sandstone, as distinguished from the Old Red, or Devonian.
The absence of Lepidodendrons and Sigillariae in this period,
i is
EVOLUTION OF LIFE.
so striking a feature of the Carboniferous, is to be noticed
as an important fact for the Evolutionist, the Cycadae and
Coni ferae completely replacing them. Among the Batrachia
of the Trias are to be noticed the immense Labyrinthodons,
the skull in one species measuring three feet long by two
wide; remains of these animals have been found near
Gwynedd, in the Triassic of Pennsylvania. The Connecticut
Sandstone is famous for its tracks, supposed to have been
made by large Reptiles, of which more than fifty species
have been described. During this period the Birds first
appeared, and, from their tracks left in the sandstone, they
are thought to have resembled the Running-birds of the
present day, though much larger, the Brontozoon (Fig. 148)
of the Connecticut valley being four times as large as the
Ostrich. The existence of such large birds may be doubted
by those who are not familiar with fossils. Those, however,
who have seen the gigantic Dinornis of the British Museum
are quite satisfied with Prof. Owen’s statement, that they
are “ equal to the formation of tridactyle impressions as
large as those of the Connecticut Sandstones.” (Pal., p. 331.)
In the Triassic the remains of Mammals are first found.
The fossil remains Microlestes and Dromatherium (Fig.
149) are usually regarded as Marsupials, or pouch-bearing
Mammalia. The Dromatherium, according to Prof. Owen,
“would appear to find its nearest analogue in the Myrme-
cobius,” a little Marsupial living at the. present day in
Australia. These fossil Mammals have been supposed by
some authors to be Monotremata, though that order have
no teeth, as in the Duck-bill, etc. This perhaps, however,
was not the primitive condition of the order, the first
Monotremata having teeth, which their descendants have
lost through adaptation to their peculiar mode of life.
Whether this view be or be not confirmed by future
research, the important fact to be noticed is that in either
case the Mammals which first appeared on the earth were
GEOLOGY.
1 1 9
the lowest of the order. The existence of such large birds
as the Brontozoon, at this period, is in harmony with the
view of the Reptiles being the progenitors through the
Ostrich family of the Birds, while the fact of both Birds
and Mammals appearing about the same time confirms the
theory that they are the diverging stem of a common stock,
the Reptilia.
JURASSIC PERIOD.
This period is called after the Jura Mountains of Swit-
zerland, and is remarkable for the variety of its Reptiles,
which were of great size. Conspicuous were the “terrible
reptiles,” or Dinosauria, of which the carnivorous Megalo-
saurus and herbivorous Iguanodon were upwards of thirty
feet long. Very curious flying Reptiles existed in the
Jurassic period, such as the Pterodactyle and Dimorphodon
(Fig. 150).- Equally characteristic were the Ichthyosauri
(Fig. 58) and Plesiosauri, upwards of thirty feet long, whose
organization united reptilian with batrachian and piscine
characters. Their fin- or paddle-like extremities would
indicate that they had diverged from the stem of Fishes
rather than from that of the Batrachia. Their structure,
however, is so peculiar as to make it extremely difficult to
determine their exact position in the animal kingdom.
Crocodiles and Turtles appear now for the first time,
together with Sharks of the cutting-teeth kind, like the
modern gray Shark (Notidanus), which will soon replace
the Cestracions, so striking a feature of the ancient forma-
tions, while the Insects are represented by the high order
of Hymenoptera. The Compsognathus (delicate jaw), a
very bird-like Reptile, and the Archeopteryx (ancient bird),
a reptile-like Bird, both Jurassic fossils, are extremely
interesting to the Evolutionist, as almost bridging over the
gap between existing reptiles and birds. The Mammals
of this period are still of the Marsupial order.
120
EVOLUTION OF LIFE.
CRETACEOUS PERIOD.
This name is given to rocks occurring in various parts
of the world, which contain well-marked and characteristic
forms of animal and vegetal life, though the rocks them-
selves may be composed of very different minerals. Thus,
the chalk-cliffs of England are so striking as to give her
the name of Albion, while up to the present time no chalk
has been found in America. The formation in New Jersey,
etc., supposed to correspond to the Cretaceous of England,
consists principally of marl, much used for fertilizing
purposes. The apparently simple and generally unobserved
phenomena of one’s fireside are often really so complex
that lives have been spent in investigating, volumes written
in explaining them. The burning of a candle forms the
subject of an interesting little book by the late Prof. Fara-
day; while Prof. Huxley observes, “The man who should
know the true history of the bit of chalk which every
carpenter carries about in his breeches-pocket, though
ignorant of all other history, is likely to have a better con-
ception of this wonderful universe, and of a man’s relation
to it, than the most learned student who is deep-read in the
records of humanity and ignorant of those of Nature.’’ It
would be superfluous to attempt to show the justice of this
profound remark, as those who care to follow the reason-
ings by which such a conclusion is reached can find them
in the essay on a “Piece of Chalk,” from which the above
quotation is taken. While the Reptiles of the Cretaceous
period still include huge creatures like the Hadrosaurus
and Mososaurus, the Fishes and Plants are becoming more
modern in their appearance, Bony Fishes first appearing in
this period, among which are to be mentioned the Herring,
Salmon, etc., and the vegetal kingdom being represented
by modern trees, like the Palms, Oaks, and PopTars, ac-
companied by a marked decline in the Cycada;. With the
GEOLOGY.
I 2 I
Cretaceous period we leave the Secondary Age, and pass
on to the Tertiary.
AGE OF PALMS, EXOGENS, AND MAMMALS.
The Tertiary Age is subdivided into the Eocene, Miocene,
and Pliocene periods. These names were chosen to express
the result of a comparison made between the shells found
in the rocks of the Tertiary formation and those living at
the present day, the object in view being to determine
whether many living shells are found petrified in the
Tertiary rocks. Thus, in Sicily, of one hundred petrified
shells, from seventy to ninety are found in existing seas ;
hence the name Pliocene, or most recent, was given to
rocks containing such a large proportion of living shells.
Those parts of the Tertiary formation known as Miocene,
or less recent, have from forty to fifty per cent., while only
the dawn of recent shells is expressed by the term Eocene.
The subdivision of the Tertiary Age into these three periods,
originally based on the proportion between the fossil and
living shells, was afterward applied to Tertiary plants and
animals generally, it being supposed that a proportion
similar to that of fossil and living shells existed between
Tertiary plants and animals and those of the present day.
These periods often, however, pass so gradually into one
another, the lines of demarkation not being very well
defined, that this classification is not always applicable.
The Tertiary Age, notwithstanding the minor differences
of its periods, is essentially an age of Mammals, Palms,
and Exogens. There is no necessity of describing the
details of its animal and vegetal life, since Asia and Africa,
with their Hippopotami, Rhinoceroses, Elephants, Lions,
and Tigers, living amidst the characteristic tropical plants,
give one an excellent idea of what America, Great Britain,
etc. were during their Tertiary Ages. To the Evolutionist the
122 EVOLUTION OF LIFE.
Paleotherium (Fig. 15 1) and Anoplotherium (Fig. 152),
living during the early part of this age, are extremely
interesting, being regarded as the progenitors of the odd-
and equal-toed Mammalia. The conclusions of Cuvier as
to the nature of the Paleotherium, based only on fragment-
ary remains, were perfectly confirmed by the discovery of
an almost entire skeleton. Since that time many allied
forms have been described, principally by Prof. Owen, some
of which, uniting the Rhinoceros, Tapir, and Horse, make
the group of odd-toed, while others, associated with the
Hog, Hippopotamus, etc., form that of the equal-toed.
Prof. Leidy has described many kinds of horses found fossil
in the western part of the United States, etc. (these dis-
coveries are confirmed by those of Owen and Rutimeyer),
which represent the transient stages 'through which the
modern horse passes, so that the descent of the Horse
from some paleotheroid form is completely made out. As
regards the Flora of the Tertiary Age, as compared with
that of the Cretaceous and Modern periods, according to
Brown, the Apetalae (Fig. 133) were greatly in excess
during the Cretaceous period, the Diapetalae were repre-
sented by a few species, while the Gamopetalse (Fig. 13 1)
had not appeared. In the Tertiary Age the Diapetalse
exceed the Apetalm, the Gamopetalae being comparatively
well represented ; while at the present day the great
number of Gamopetalous genera seems to indicate that
this order of plants is increasing most rapidly. These
facts are very significant when compared with what is said
of the structure of these plants. The age following the
Tertiary, that in which we live, is known as the Age of
Man, whose early condition, etc. will be treated of in the
chapter on Anthropology. Repeating that great caution
must be exercised in accepting the generalization of Geolo-
gists as to the relative and absolute age of rocks, a
resume of their fossil remains seems to exhibit the following
GEOLOGY.
123
progress of the higher forms of life from the lower. The
Brachiopods, the lowest of Mollusca, the Crinoids and
Star-fish, the lowest of Echinodermata, and the Trilobites,
among the lowest of Crustacea, abounded in the Paleozoic
Age. The Crinoids and Brachiopods lived on through
Secondary time, playing, however, an inferior role, and
now have almost passed away, a few Brachiopods only and
one Crinoid living at the present day. The Age of Mol-
lusca, we have seen, was followed by an Age of pishes,
thus exhibiting a progress in the animal life of the globe.
The fact of these fishes being Sharks and Ganoids is very
significant : the important point to be noticed is, that what-
ever view be taken of the rank of the Ganoids among fish,
they preceded the Teliosts and Batrachia, and that
the Sharks with pavement teeth came before those with
cutting teeth. The next two periods offer a further pro-
gress in the life of the globe, since we find the Batrachia
(Frogs, Labyrinthodons) appearing in the Carboniferous,
followed by the Reptiles (Proterosaurus) in the Permian,
while the Insects are represented by the lower orders, of
which the Neuroptera (May-flies) were very abundant in
the Carboniferous. In the Secondary Age the Reptiles
reach their climax, while the Bony Fishes, Mammals, and
Birds are just appearing. The gradual unfolding of the
vegetal kingdom during the Primary and Secondary Ages
is as marked as that of the animal kingdom. An Age of
Algae was followed by an Age of Acrogens ; these gave
way to Cycadae and Coniferae ; the Cycadae, in their turn
dying out, were replaced by the Palms of the Tertiary,
associated with which are the Poorest trees, among which
the great Mammals lived, and the flowering plants offered
then as now a resting-place for butterflies, which first
appeared in this age.
Modern Geologists do not believe that life, since it first
appeared, has ever been extinct all over the globe at the
124
EVOLUTION OF LIFE.
same time. The earth has, no doubt, from time to time
experienced great changes, its life being more or less
destroyed by the effects of earthquakes, volcanoes, etc.
These catastrophes were, however, local in their effects,
as at the present day. If living plants and animals be
compared with those whose remains have been preserved
in the rocks, we see that, while many species and genera
have passed away, comparatively few orders have become
extinct, — that is, there are very few fossils which have
not their modern representatives. Further, where the
rocks overlie or follow each other, plants and animals
appear in the later formation which did not pre-exist in
the earlier, and usually exhibit a more complex structure.
So that the “ persistent types of life” seem to have been
more or less modified from time to time. These general
conclusions are in perfect harmony with the doctrine of
the gradual development of the higher forms of life from
the lower. We turn now to Embryology, which confirms,
in the most remarkable way, the tree of life deduced from
the structure and fossil remains of the animal and vegetal
kingdoms.
CLASSIFICATION OF ROCKS ACCORDING TO THEIR ORGANIC
REMAINS.
time. period. age.
, Silurian.
-{ Mollusca, Algce.
Primary. J Devonian.
-j Fishes.
t Carboniferous.
-j Batrachia, Acrogens.
Triassic.
I
Secondary. -j Jurassic.
>- Reptiles, Cycadax
(. Cretaceous.
J
, Eocene.
Tertiary. ) Miocene.
[■ Mammals, Palms, Exogens.
! Pliocene.
J
Quaternary. -{ Modern.
-{ Man.
EMBRYOLOGY.
The study of the transitional stages through which plants
and animals pass from the early to the mature condition is
not only of immense importance to the Physiologist, but
equally so to the Zoologist, Botanist, and Geologist. Not-
withstanding that some knowledge, at least, of Embryology
is demanded in the study of Biology, the subject is com-
paratively little cultivated, owing, probably, to the limited
means of obtaining material, and the difficult manipulation
required in this kind of work. Nevertheless, since 1759,
the year in which Wolff published his “ Theoria Genera-
tion^, ’’there have appeared from time to time Embryologists
like Von Baer, Schleiden, Schwann, Coste, Remak, Rathke,
etc., who, after overcoming the difficulties inherent to the
nature of their studies, left treatises which will always be
models of scientific work and philosophic thought. Our
prescribed limits only permit of briefly calling attention to
some of the conclusions of Embryology, pointing out the
manner in which they confirm the theory of the evolution
of life as deduced from the structure and petrified remains
of the vegetal and animal kingdoms. Those who are
ignorant of the early stages of plants and animals will
hardly believe that beings so different as sea-weed, oaks,
star-fishes, mollusca, guinea-pigs, rabbits, dogs, and men
begin their life in the same way; yet Fig. 160 represents
equally well the cell, or primitive stage, of any of the
plants or animals just mentioned. Confining ourselves for
( I2 5 )
126
EVOLUTION OF LIFE.
the present to the animal kingdom, let us examine the cell,
or the egg, of a mammal, — that of a rabbit (Fig. 160),
guinea-pig, or man, for example. The egg of a mammal,
about the of an inch in diameter, when magnified, is
seen to consist of a cell-wall or Vitelline membrane (Fig.
160), inclosing cell-contents, or the Vitellus, in which is
found the nucleus (Fig. 160, n), or Germinal vesicle, with
its nucleolus, or Germinal spot. Let us observe what takes
place, supposing the conditions to be favorable to the
development of the egg. According to some observers,
the Germinal vesicle and spot disappear; equally good
observers, however, state that the Germinal vesicle and
spot divide into two. While there is some doubt as to the
disappearance of the Germinal vesicle and spot, all observers
agree that the Vitellus, or cell-contents, divide into two
segments (Fig. 1 6 1 ), and that each segment has its nucleus
and nucleolus. As the segments are the halves of the
Vitellus, probably the nuclei and nucleoli are formed
through the division of the Germinal vesicle and spot.
However this may be, the Vitellus divides into two seg-
ments, each segment having a nucleus with its nucleolus.
These two segments subdivide into four balls (Fig. 162),
the four into eight (Fig. 163), the eight into sixteen (Fig.
164), and so on. Through this process of cell-division, or
segmentation, as it is called, the Vitellus is divided into a
number of little balls, and assumes the shape of a mulberry.
Finally, the superficial balls of the mulberry are transformed
into cells, and so arrange themselves as to present the
appearance of a mosaic pavement (Fig. 165); as the deeper
balls become cells, they pass to the surface and increase
the thickness of this mosaic -like membrane. In this
manner the Vitellus is converted into a vesicle ; within this
vesicle there shortly appears a second vesicle ; these two
vesicles are usually called the Germinal layers, or the
External and Internal blastodermic membranes. If the
turtle chicken DOG
EMBRYOLOGY.
12 7
egg in a slightlytmore advanced stage be now examined
from a horizontal point of view, there will be seen a light
oval space, the area pellucida, surrounded by a dark space,
the area opaca (Fig. 1 66) ; within the area pellucida will
be noticed an oval body, the Primitive trace, so called from
indicating the position of the embryo, the furrow in the
Primitive trace being known as the Primitive groove. A
little later the Primitive trace and area pellucida become
guitar-shaped (Fig. 167), and if a longitudinal section of
the egg be examined (Fig. 168) it will be seen to consist
of the External and Internal blastodermic membranes, and
a third membrane lying between these two. The partial
fusion of these membranes makes the Primitive trace.
While these three membranes are consolidating into the
\
Primitive trace, the Middle membrane splits into two
layers : the Upper terminates in the External blastodermic
membrane, the Lower grows gradually around, the In-
ternal blastodermic membrane, finally inclosing it. The
embryo at this period is a guitar-shaped body (Fig. 177),
consisting simply of three membranes lying over one
another, narrowly bound together. The question may be
asked by some of our readers, What relation does so
minute a structure as the egg of a mammal bear to that of
a bird ? Does the development of a rabbit resemble that
of the chick? The egg of a chicken (Fig. 174), as all the
world knows, is composed of a shell inclosing a semi-liquid
substance, in which is suspended a yolk. If a freshly-laid
egg be carefully examined, however, supposing the condi-
tions to have been favorable to development, there will be
found lying on the top of the yolk a delicate sheath (Fig.
174, b), which is composed of two membranes; while the
yolk itself, if laid open, exhibits in its interior a whitish
body (Fig. 174, a), which, narrowing into a thread, runs
upwards towards the membrane composing the sheath.
This whitish substance is called the white yolk, as distin-
128
EVOLUTION OF LIFE.
guished from the yellow yolk surrounding it. We have
tried to explain how, by a continued process of cell-division,
the contents of the egg of a mammal assume a mulberry-
shaped form, and the gradual conversion of this mulberry
into the External and Internal blastodermic membranes.
If the yolk of the chicken be examined before it is sur j
rounded by the semi-fluid substance (Fig. 173) and shell,
there will be found lying on the top of the yellow yolk a
membrane (Fig. 173, b ) in which may be seen the Germinal
vesicle and Germinal spot; by a process of cell-division,
known as partial segmentation, this membrane is trans-
formed into a heap of balls which gradually assume the
form of the two membranes which, we have stated, are found
lying upon the yellow yolk of the freshly-laid egg. In the
course of development a third membrane appears between
these two. The partial fusion of these membranes makes
the Primitive trace, which passes from the oval to the
guitar-shaped form (Fig. 177). The Middle membrane
splits into two layers (Fig. 175), the Upper uniting with
the External blastodermic membrane, the Lower bend-
ing down on the Internal blastodermic membrane (Fig.
1 76, c). The Middle and Internal blastodermic membranes
now grow gradually downward around the yellow yolk,
and finally inclose it. At this stage the embryo chick
corresponds to Fig. 177, representing the embryo of a
mammal. We see, therefore, that the development of the
chick and the mammal is the same, while the difference
between their eggs is not an essential one, — the nutriment
for the mammalian egg being furnished from time to time,
while that for the bird’s egg is supplied at once in the form
of yolk. A homely illustration of this difference is that
of a man who receives his yearly food from day to day,
and of one who receives his yearly food at once. The
only part of the chicken’s egg which corresponds to the
mammal’s egg is the membrane with its Germinal vesicle
EMBRYOLOGY.
129
and Germinal spot, lying upon the yellow yolk of the
unlaid egg.* Whatever view be taken of the relations of
the eggs of the Vertebrata, the important point to be
noticed is that the embryo of a fish, batrachian, reptile, bird,
or mammal, including man at an early stage of life, is a
guitar-shaped body (Figs. 177, 167), consisting of three
membranes lying over one another, and narrowly bound
together (Fig. 168); and if we were ignorant of the animal
whose egg had been transformed into such a body, it would
be very often impossible to say what would result from its
development. These membranes are called blastodermic,
or tissue germinating from the organs of the future animal
growing in them.f
The skin and central nervous system are developed in
the External, or upper membrane; the osseous, muscular,
vascular, reproductive, and urinary systems, the walls of
the alimentary canal, and its appendages, are produced in
the Middle membrane; while the epithelium, which lines
the alimentary, canal and its appendages, the lungs, liver,
etc., is derived from the Internal or lower membrane.
In speaking of the Primitive trace, at page 127, we called
attention to the furrow known as the Primitive groove. As
development proceeds, this furrow deepens, and if the
* We have called attention to the distinction of white and yellow yolk, as
the white yolk, or part of it, is supposed by Peremesko to form the Middle
layer of the chick; his view being that the balls of the white yolk, by an
amcebiform movement, pass up and between the External and Internal
blastodermic membranes, coalesce, and so form the Middle membrane.
f By many Physiologists the embryo is stated as consisting of two layers,
the External and Internal germinal layers, or blastodermic membrane, from
which the future animal is developed. The view of the embryo consisting
of three germinal layers was distinctly enunciated by Remalc as long ago as
1852, “ Comptes Rendus,” tome xxxv., and even earlier. Since that time
Remak’s views have been confirmed by Rathke, Kolliker, Strieker, Waldeyer,
Klein, and others. We, therefore, give in the text what may be called the
German theory of Embryology.
9
130
EVOLUTION OF LIFE.
embryo be viewed in transverse section (Fig. 175), this
deepening is seen to be produced through the rising up of
the External blastodermic membrane (Fig. 175, a) in two
heaps, called Laminae Dorsales (Fig. 175, L), which, grow-
ing towards each other, finally coalesce, thus converting
the Primitive groove into a tube (Fig. 176, K). This tube
is the rudimentary central nervous system. Directly under-
neath this tube, in the Middle membrane, however, is seen
a cylindrical rod of cells, the Chorda Dorsalis (Fig. 176, v),
in which are developed the bodies of the vertebrae (segments
of spine). By looking at Figs. 169 to 172 (Dog or Man),
we see how, by a continually constructing process, the
upper portion of the Internal blastodermic membrane (Fig.
169, /), with that part of the Middle membrane lying upon
it, is gradually pinched off from the lower (Fig. 169, a),
until, finally, only a narrow pedicle connects the two. The
upper pinched-off portion is the primitive alimentary canal
(Fig. 170, /), the lower the umbilical vesicle, or yolk-bag.
The umbilical vesicle (Figs. 169 to 172, a), in the course
of development, passes away, the time of its disappearance
varying in different animals: thus, in the Trout it is retained
till the sixtieth day. By referring to Figs. 169, 172, it will
be seen that the alimentary canal and umbilical vesicle are
composed of two layers. The inner layer, or the Internal
blastodermic membrane, develops the epithelium or the
mucous membrane ; the outer layer, or the lower half of the
Middle membrane, makes the wall of the alimentary canal.
This is a very important distinction, since the lower lungs,
etc., which first appear as buds sprouting from the aliment-
ary canal, exhibit the same structure. In the Batrachia
(Frog), and some Fishes, however, the whole of the Inter-
nal blastodermic membrane, with that part of the Middle
membrane lying upon it, is used up in the formation of
the alimentary canal, which is developed in a different
manner from that of the dog or man ; there is, therefore, no
EMBR YOLO GY.
131
umbilical vesicle or yolk-bag. The gelatinous mass which
surrounds the egg of the Frog furnishes the nutriment for
the embryo. The development of the Reptile, Bird, and
Mammal offers a striking contrast as compared with that
of the Fish and Batrachian in the formation of the Amnion
and Allantois. The External blastodermic membrane,
at that point where the upper part of the Middle mem-
brane unites with it, rises up into two folds (Fig. 169, d).
These folds grow towards each other, arching over the
embryo, and finally unite (Fig. 170). The inner fold then
separates from the outer, and forms the Amnion (Fig.
17 1, d ), while the outer fold recedes from the Amnion until
it reaches the Vitelline membrane, with which it unites.
These united membranes are known as the Chorion
(Fig. 1 7 1, Cli). The Amnion becomes filled with the
Amniotic fluid, in which the embryo is suspended.
During the formation of the Amnion there buds out from
the posterior portion of the embryo a sac (Figs. 169 to
172), which, in expanding, finally comes in contact with
the Chorion. This sac is called the Allantois, and serves
in Birds and Reptiles as a respiratory organ, the porosity
of the egg-shell allowing the oxygen to pass in and the
carbonic acid to pass out. In the Mammals, through the
Allantois, the embryo is put in communication with the
mother. We have now explained as briefly as possible
the development of a vertebrate.
In the hatching process the Chorion, Allantois, and
Amnion break, they being only temporary structures. It
will be seen, therefore, that the animal is formed of but
a portion of the three blastodermic membranes. - Beginning
alike in the form of a cell or egg, the Invertebrata and Verte-
brata grow for some time in the same manner. As devel-
opment advances, characteristic structures appear in the
embryo, and the division, class, or order to which the future
animal will belong becomes evident. Figs. 178 to 1 8 1 , repre-
132
EVOLUTION OF LIFE.
senting the embryo Turtle, Chicken, Dog, and Man, illustrate
the resemblance of vertebrate animals at an early stage of
their existence. Not only, however, does man at such a
period resemble a Turtle, and is undistinguishable from a
Dog, but the transitory stages of his internal organization
are also more or less represented as permanent structures
in the lower animals. This generalization, which is one of
the most important in Biology, may be expressed in the
statement, that the structures which are transitory in the
higher animals are retained permanently in the lower.
Thus, for example, the spine of the higher animals is com-
posed of a number of bony segments or vertebrae. These
are represented in the embryo, however, by a cylindrical
rod of cells, the Chorda Dorsalis, and by a few quadrate
masses lying on each side of the central nervous system.
The Chorda Dorsalis, which is only the 'rudimentary con-
dition of the bodies of the vertebrae, is retained permanently,
however, in the Amphioxus and Myxinoid fishes. The
Chorda Dorsalis, until recently, was supposed to charac-
terize the Vertebrata, and as it is a very important structure,
its apparent absence in the Invertebrata (animals without a
backbone) was often urged as an insuperable objection to
the view of the higher forms of life having come from the
lower. The free-swimming embryos of the Ascidian worms,
however, according to Kowalebsky and others, exhibit, in
their organization, a Chorda Dorsalis (Fig. 38 a, C) and a
Central nervous system, which develop in the same manner
as that observed in the Amphioxus, thesimplest of fishes. The
importance of this discovery cannot be exaggerated, as the
embryo Ascidian furnishes the transition from the Inverte-
brata to the Vertebrata. We have seen that the Central
nervous system is formed through the conversion of the
Primitive groove into a tube. The tube is originally pointed
at both ends, and this rudimentary condition is retained
permanently in the spinal marrow of the Amphioxus (Fig.
EMBRYOLOGY.
133
40), — the fish without skull or brain. In all other Verteb rata,
however, the anterior part of the spinal marrow, in the
course of development, expands into a vesicle, which sub-
divides into three; the anterior of these three vesicles
divides into two, and the posterior into two, the middle
remains undivided; thus five vesicles (Fig. 177, I, 2, 3, 4,
5) are formed out of the swelling of the anterior portion
of the spinal marrow. These vesicles are called, translating
their German names literally, the Fore brain, Between
brain, Middle brain, Hind brain, and Hindmost brain, the
different parts of the brain being developed from them.
The brain of adult man, although highly complex in its
organization, is nevertheless represented, at an early period
of life, by five vesicles, being undistinguishable from those
of an embryo dog, rabbit, bird, or fish. In fishes like the
Myxine and Lamprey the brain remains in this undevel-
oped condition, thus exhibiting permanently the stages of
the brain that are transitory in the higher animals. Every
one knows that in breathing the air passes through the
windpipe to the lungs, and that the food goes to the
stomach through a separate and distinct tube. If, however,
a Garpike be examined, its lung-like air-bladder is seen
to communicate with the alimentary canal by a tube, the
air-duct. This arrangement represents perfectly the rudi-
mentary condition of the lungs in the human being, or in the
embryo of the higher animal, as in these the lungs are devel-
oped as buds from the alimentary canal, the pedicle by which
they are attached to it becoming later the windpipe, which
corresponds to the air-duct of the Gar. The organs of
Respiration naturally suggest those of Circulation. The
successive stages through which the heart and blood-vessels
of mammals pass in the course of development are more
or less well represented by the vascular apparatus of the
fish, batrachian, reptile, and bird. The termination of the
Digestive, Reproductive, and Urinary apparatus in a Cloaca,
/
134
EVOLUTION OF LIFE.
exhibited in the embryo of man, is a permanent arrange-
ment in the Sloth, Monotremata, Birds, and Reptiles.
Finally, the development of the Skull and Extremities
illustrates the same principle of the lower forms of life,
representing the undeveloped stages of the higher. Has
the Biologist any theory to offer as an explanation of these
facts? One may reasonably ask, Why do the flipper of the
seal, the foot of the turtle, the wing of the bird, the hoof
of the horse, the claw of the lion, the hand of man, etc.,
develop from a bud ? Why are these structures, used for
such different purposes, constructed on essentially the same
plan ? Is there any explanation of the fact that man and
the lower animals are undistinguishable in the early stages
of their existence, and that the transitory phases through
which man passes in the course of development are more or
less permanently represented in the lower animals, — that
is, that man is not absolutely at any time a Reptile or
Dog, etc., but at a certain period exhibits an organization
which is undistinguishable from that which later becomes
a Turtle or Dog, etc.? It seems to us that the theory of
the higher animals having descended from the lower ex-
plains perfectly all these facts. We will try to illustrate
this view by noticing the effects supposed to be produced
on the posterity of a family by their dispersion. After the
lapse of ages, subjected to different conditions of soil, food,
and climate, the races descending from this family would
differ so greatly as regards their appearance, language, and
customs that an Ethnologist might doubt if indeed they
had come from one stock. If, however, he compared young
individuals of these races, and found they resembled one
another, and at an extremely early period of life were even
undistinguishable, and, further, that sometimes individuals
appeared that differed greatly from the race from which
they descended, resembling rather a remote, often more
barbarous, one; and, finally, that the individuals of a bar-
EMBR YOLOG Y.
135
barous race, when subjected to more favorable conditions,
in becoming more civilized, begin to resemble those more
advanced, — considering these facts together, the view might
be suggested to the Ethnologist that the different races
had come from one stock. An important fact to be
remembered in reference to the origin of races is that
peculiarities which appear in the parent reappear in the
offspring at the same age in which the parent was affected.
Thus, the parent at a certain age develops a disease: his
child grows up apparently healthy; suddenly the same
disease appears in the child, and at the same age at which
the parent was affected. Though the causes of peculiarities
appearing in the parent, and the inheriting of them by the
offspring, are still unknown, or very obscure, nevertheless
we know it to be a fact that peculiarities — good or bad —
affecting a parent may, and often do, reappear in the
offspring in the manner just illustrated. Suppose, now, in
a remote past, two animals, the descendants of the same
parent, grew for some time alike, but that gradually they
began to differ, acquiring certain peculiarities. These, if
transmitted to posterity, would appear at the same age
in which they were acquired by the parents. This hypo-
thetical case illustrates what we suppose to have been the
development of the Bird and Mammal from a common
ancestor, the Reptile. This reptilian ancestor had two
descendants; one acquired the peculiarities of the Bird, the
other those of the Mammal : the Bird and Mammal of the
present day ought, therefore, to develop in a reptilian
manner until they attain the age at which their progenitors
acquired the characteristic of the Bird and Mammal; from
that time their development ought to be different-. Our
brief resume of development shows that the facts perfectly
confirm such a theory. By the same reasoning we con-
clude that the Reptiles and Batrachia have diverged from
a form like that of the Lepidosiren, or Mud-fish, the Bony
136
EVOLUTION OF LIFE.
fi.sh and Lepidosiren from the Ganoids, the Fish and
Ascidians from some Sac-worm, the Echinodermata and
Articulata from the Articulated Worms; finally, that the
animal and vegetal kingdoms are the diverging stems of
an intermediate kingdom, arising through spontaneous
generation, or whose origin is unknown. This theory of
the gradual descent of the higher animals from the lower
explains perfectly why the phases exhibited in the develop-
ment of man should be more or less permanently repre-
sented by lower animals, or, as John Hunter expressed it,
“If we were to take a series of animals from the most
imperfect to the perfect, we should probably find an imper-
fect animal corresponding with some stage of the most
perfect.” This view of nature throws light on the presence
of rudimentary organs, such as the wings of birds and
insects who never fly, the eyes of fish who, living in dark
caves, never see, and the teeth of young birds and of
certain whales who, when adult, do not have a tooth in
their head. In the lung-breathing Vertebrata a right and
left lung are usually present; the organization of the snakes
and snake-like lizards exhibits the peculiarity of only one
lung being developed, the other being rudimentary. Of
the egg-sacs, or ovaries, of most birds, only the left is
developed, the right being without function. Assuming
the theory of the transmutation of species to be true, these
rudimentary organs have a meaning, as indicating the
ancestry of the animals exhibiting them. Important to the
Evolutionist are, therefore, such structures as the plica
semilunaris of the human eye, the representative of the
third eyelid of lower animals, the external muscles of the
human ear, the coccygeal bones composing the short tail
of man, the vermiform appendix, etc. The monstrosities
of the animal and vegetal kingdom are explainable from
this point of view, the monstrosity usually consisting in
the excessive development or deficiency of one or more
EMBRYOLOGY.
137
organs, the abnormal in one animal being normal in
another. Occasionally we find animals so badly organized
as to make it incredible that they should have appeared on
the earth as such originally. In speaking of the Sloth,
Cuvier observes, “One finds them so little related to ordi-
nary animals, the general laws ofliving organizations apply
so little to them, the different parts of their body seem to
be so much in contradiction with the rules of co-existence
that we find established in the whole animal kingdom, that
one could really believe that they are the remains of
another order of things.” Cuvier then continues by saying
that in most forms the disadvantages are compensated by
advantages, “but in the Sloth each singularity of organiza-
tion seems to result only in feebleness and imperfection,
and the inconveniences belonging to the animal are not
compensated by any advantage.”*
The only explanation, at present, of the existence of such
a wretched animal as the Sloth is that it is the degenerated
representative of some extinct animal who lived at the
same time as the Megatherium, which it resembles in the
form of its head. The limbs and backbone of the Mega-
therium are, however, represented by the Great Ant-eater.
The Sloths and Great Ant-eater are confined to South
America, and it is there that the Megatherium remains
have been found in great abundance.
The development of the flower through the gradual
metamorphosis of the leaf is a beautiful illustration of the
evolution of different forms from a common type. In the
words of Prof. Gray, “The leaves of the stem, the leaves
or petals of the flower, and even the stamens and pistils,
are all forms of a common type, only differing in their
special development; and it may be added that, in an
early stage of development, they all appear nearly alike.
* Cuvier, “ Oasemens fossiles.”
133
EVOLUTION OF LIFE.
That which, under the ordinary laws of vegetation, would
have developed as a leafy branch, here develops as a flower;
its several organs appearing under forms some of them
slightly and others extremely different in aspect and in
office from the foliage. But they all have a common nature
and a common origin, or, in other words, are homologous
parts. When, therefore, the floral organs are called modified
or metamorphosed leaves, it is not to be supposed that a
petal has ever actually been a green leaf, and has subse-
quently assumed a more delicate texture and hue, or that
stamens and pistils have previously existed in the state
of foliage, but only that what is fundamentally one and
the same organ develops, in the progressive evolution of
the plant, under each or any of tl]ese various forms.” The
visceral arches of the Vertebrata are among the many illus-
trations of this idea offered by the animal kingdom. The
visceral arches (Figs. 178 to 18 1, c) consist of thickenings
or papillae situated behind the primitive eye, and below
the primitive ear. They are present in the early stages of
all Vertebrata, and are much modified in the course of
development. The branchial arches supporting the gills
in Fishes represent best their primitive condition, while
in remaining Vertebrata they are used partly in the
formation of the lower jaws, partly in the formation of
the organs of hearing.
The subject of Embryology is as intimately related to
Geology as to that of Anatomy, for the changes through
which plants and animals pass in the course of develop-
ment are essentially the same changes through which life
in general has passed from its first appearance to the pres-
ent time, for not only are the transitory stages of the
higher animals permanently represented by the lower, but
they are also permanently represented by the fossils. In
other words, the development of the most complex plant,
and of the most highly-organized animal, is an epitomized
EMBRYOLOGY.
139
history of vegetal and animal life in general. Let us illus-
trate by a few examples. We stated in the chapter on
Zoology that the Horse, Tapir, and Rhinoceros formed a
natural group, they being connected through intermediate
forms, the series beginning with the Paleotherium (Fig.
1 5 1 ). In the chapter on Geology we called attention to
the fact that the Paleotherium appeared before the Horse,
etc. The embryo Horse, however, in his three toes and
the structure of his teeth, represents the Paleotherium (Fig.
154), while the transitory stages through which the Horse
passes from the Paleotheroid condition to its adult state are
permanently retained in the Anchitherium and Hipparion.
(Fig. 155). In Ruminating animals, like the Gazelle, Sheep,
and Ox, the upper jaw is without incisor and canine teeth
(Fig. 157); these exist, however, in a rudimentary condition
in the embryos of these animals. The embryos also exhibit
two distinct metacarpal and metatarsal (Fig. 158) bones,
which, in the course of development, fuse into the so-called
cannon-bone of the fore and hind leg (Fig. 159). Now, in
the early part of the Tertiary period there lived animals like
the Dichobune, Dichodon, and Anoplotherium (Fig. 152),
whose adult organization represents very well the transitory
stage of the hollow-horned Ruminants, the Anoplothe-
rium having well-developed canine and incisor teeth, and
retaining the condition of two distinct metacarpal and
metatarsal bones (Fig. 158). The stages through which
one of our hollow-horned Ruminants passes give thus a
picture of the transitional stages through which the Rumi-
nant order in general has passed. The molar teeth of
these animals, as well as those of the Rhinoceros, Horse,
etc., are very interesting from the Evolution point of view.
The type of tooth characteristic of the Paleotherium runs,
more or less modified, through the Rhinoceros, Tapir (Fig.
I 53 )i ar, d Horse, while that of the Anoplotherium can be
traced through the Hog, Hippopotamus, Sheep, Deer, etc.;
140
EVOLUTION OF LIFE.
but in still earlier forms, like Coryphodon, Pliolophus, and
Lophiodon, we find teeth combining the characteristics of
the Paleotherium and Anoplotherium. So that just as the
Rhinoceros and Horse are specialized forms of the Paleo-
therium, the Pig and Sheep of the Anoplotherium, so the
Paleotherium and Anoplotherium are specialized forrtis of
the Coryphodon. Accepting the theory of the specialized
higher forms of life having descended from a more general
lower form, we have an explanation of the harmony offered
by the anatomy, embryology, and petrified remains of
these animals. But the theory of Evolution explains not
only the most important facts in reference to this particular
order of animals, but we hope to have shown that it is
equally applicable to the whole vegetal and animal king-
dom. The question now naturally arises, Are there any
natural causes sufficient to effect the development of the
animal and vegetal kingdoms out of a monad ?
To that subject we now turn.
NATURAL SELECTION.
In his introduction, Mr. Darwin tells us that “when on
board H. M. S. Beagle as naturalist, I was much struck
with certain facts in the distribution of the organic beings
inhabiting South America, and in the geological relations
of the present to the past inhabitants of that continent.
These facts seemed to throw some light on the origin of
species.” In the chapter on Geographical Distribution, he
says that “neither the similarity nor the dissimilarity of
the inhabitants of various regions can be accounted for
by their climatal and other physical conditions.” Thus, the
plants and animals of South America, between latitudes
25 ° and 55 0 , are very different from those of Australia and
South Africa; and yet the physical conditions of these three
countries, within these limits, are very similar, while, not-
withstanding the great differences of the physical conditions
north of 25 0 and south of 35 0 , the plants and animals of
these parts of South America are very similar. The
existence of lofty mountain-chains, great deserts, etc. acts
as a barrier to the free dispersion of plants and animals, and,
therefore, is of great importance in reference to Geograph-
ical Distribution; thus, the life of opposite mountain-chains
is often quite different. This is equally true of the ocean
life on opposite sides of a continent: thus, the marine
animals of the north side of the Isthmus of Panama are
very different from those of the south side, whereas similar
fishes are found in as remote waters as the Pacific and Indian
( 141 )
142
EVOLUTION OF LIFE.
oceans, — there being no obstacle to their free dispersion.
The relation of the living animals to those found fossil in
the same countries is very significant in this respect, the
Apteryx of New Zealand representing the gigantic Dinor-
nis, the Armadillo and Sloth the extinct Glyptodon and
Megatherium. Further, in reference to Geographical Dis-
tribution, the fact of the plants and animals of islands being
like those of the nearest island or mainland is as important
to the Geologist as to the Botanist and Zoologist. Thus,
Mr. Wallace explains the similarity of the plants and
animals of Sumatra, Java, Borneo, etc. to those of southern
Asia by supposing that these islands once formed part
of that continent, being connected with it by Malacca;
while the Celebes, Moluccas, New Guinea, resembling in
their flora and fauna Australia, are regarded as forming
with it another continent, the islands of Bali and Lombok
indicating the limits of these ancient continents. Mr.
Wallace says, in crossing over the straits separating these
islands, “we may pass in two hours from one great divi-
sion of the earth to another, differing as essentially in their
animal life as Europe does from America.” The study of
South America and the Malay Archipelago suggested to
Messrs. Darwin and Wallace their explanation of the
Geographical Distribution of plants and animals through
what Mr. Darwin calls Natural Selection, which may be
expressed as follows :
Plants and animals struggle for existence. The imme-
diate descendants are never absolutely like their parents;
while remote posterity often differs considerably from them.
Those plants and animals whose modified organization
gives them an advantage over those not so favored survive,
or are naturally selected, and transmit their modifications
to posterity.
Let us examine these statements, and try to explain how
the conclusion follows.
NATURAL SELECTION.
143
STRUGGLE FOR EXISTENCE.
Every one knows that the life of an individual plant or
animal depends on a proper supply of food, is affected by
changes of climate, and is constantly endangered by dis-
ease and enemies ; few are, however, aware of the extent
to which individual life is dependent on the existence of
some other kind of life, and of the extremely complex
nature of the struggle for existence. Thus, according to
Prof. Haeckel, “ There are small oceanic islands whose
inhabitants live essentially on a species of Palm. The
fructification of these Palms is effected principally through
Insects, who carry the pollen from the male to the female
Palm. The existence of these useful Insects is endangered
through Insect-feeding birds, who in turn are pursued by
Rapacious birds. But the Rapacious birds often succumb
under the attacks of a small parasitic Mite, which develops
by millions in their feathery coats. These small, dangerous
Parasites can be killed through parasitic Fungi. Fungi,
Rapacious birds, and Insects in this case would favor, Bird-
mites and Insect-feeding birds, on the contrary, would
endanger, the growth of the Palms, and consequently of
men.” Thus the existence of entire populations may be
indirectly dependent on the presence of a highly insignifi-
cant plant or animal form. If one considers the millions
of eggs laid by fishes, avid that a pair of elephants, the
slowest of breeders, would reproduce in five hundred years
fifteen millions, the importance of the struggle for existence
in checking over-population will be appreciated. Accord-
ing to Mr. Darwin, the red clover never produces seed if
the humble-bees be prevented from visiting it. For the
bee, in sucking the honey out of the flower, brings the
pollen in contact with the pistil, and by this means the
clover is fertilized. Now, it is well known that the bees
are destroyed by the field-mice, and that the number of
144
EVOLUTION OF LIFE.
mice depends on the number of cats; hence, if the cats
were destroyed the field-mice would increase and destroy
the bees, in which case the clover would produce no seed,
and the cattle would soon be deprived of a most important
article of food. The same author calls attention to the
fact of cattle determining the existence of trees: “Here
there are extensive heaths, with a few clumps of old Scotch
firs, on the distant hill-tops: within the last ten years large
spaces have been inclosed, and self-sown firs are now
springing up in multitudes, so close together that all
cannot live. When I ascertained that these young trees
had not been sown or planted, I was so much surprised at
their numbers that I went to several points of view whence
I could examine hundreds of acres of the uninclosed
heath, and, literally, I could not see a single Scotch fir,
except the old planted clumps. But on looking closely
between the stems of the heath, I found a multitude of
seedlings and little trees, which had been perpetually
browsed down by the cattle. In one square yard, at a
point some hundred yards distant from one of the old
clumps, I counted thirty-two little trees; and one of them,
with twenty-six rings of growth, had, during many years,
tried to raise its head above the stems of the heath, and
had failed. No wonder that, as soon as the land was
inclosed, it became thickly clothed with vigorously grow-
ing young firs. Yet the heath was so extremely barren,
and so extensive, that no one would ever have imagined
that cattle would have so closely and effectually searched
it for food. Here we see that cattle absolutely determine
the existence of Scotch fir. But in several parts of the
world insects determine the existence of cattle. Perhaps
Paraguay offers the most curious instance of this; for here
neither cattle nor horses nor dogs have ever run wild,
though they swarm southward and northward in a feral
state'; and Azara and Rengger have shown that this is
NA TURAL SELECTION
145
caused by the greater number in Paraguay of a certain fly
which lays its eggs in the navels of these animals when
first born,” the new-born dying in consequence of these
inroads. As illustrating the struggle for existence, Prof.
Haeckel calls attention to the effect of placing goats or
pigs on one of the isolated oceanic islands uninhabited by
man. These animals ran wild, and meeting no enemies, and
finding at first plenty of food, increased in such surprising
numbers that they killed the other animals and plants.
Thus, in the course of time, the whole island was nearly
depopulated, the goats or pigs even dying out for want
of food. In some cases dogs were let loose, after the
island had been overrun by goats or pigs. The dogs,
finding an abundance of food at first, increased so rapidly
that their very numbers made food so scarce that they
finally died out.
Many other interesting examples of the struggle for
existence might be mentioned; those just noticed suffice,
however, to call attention to the important relation exist-
ing, in this respect, between plants and animals. We
turn now to a consideration of the facts of Inheritance
and Variation.
INHERITANCE.
Not only does the offspring resemble the parent in the
manner of its growth, in the form of its body and general
appearance, but, as is well known, mental peculiarities are
also inherited, the development of particular talents for
music, painting, etc. being conspicuous in certain families :
thus, the Bach family have numbered twenty distinguished
musicians, the family of Weber upwards of forty. Less
pleasant peculiarities, as those of diseases of all kinds, are
well known to reappear in posterity both at the same time
and in the same place as they first appeared in the parent.
In a word, generally speaking, “Like begets like.” This
10
146
EVOLUTION OF LIFE.
expression, however, is not absolutely correct, since the
members of every family differ more or less in the color
of their eyes and hair, in their complexion, dispositions,
etc. The same species of trees differ as regards the size
of their stem, number of their branches, leaves, flavor of
their fruit, etc. Let us examine now, a little in detail, some
of these variations, and attempt to indicate their probable
causes.
VARIATIONS.
The quantity and quality of the food are known to mod-
ify animals and plants. Thus, what a marked difference is
produced in the habit of our domestic animals, who are fed
daily, and of wild ones, whose means of subsistence are so
precarious 1 The quality of the food modifies, as well as
the quantity, the tissues: thus, richly azotized food develops
little fat, poorly azotized food, on the contrary, a great deal.
The farmer requiring fine wool supplies his sheep with
different food from that which he gives wishing to obtain
good meat. Notice the effects of a rice diet as seen on
the Chinese, and of a beef one on the English. Climate
is an important element in the production of variations:
thus, plants growing in dry, warm, and sunny places offer
a very different aspect from those of moist, cool, and shady
spots. Plants that at the sea-side exhibit thick, fleshy
leaves, in hot, dry places develop haired ones. The crowd-
ing of trees has the effect of making the stem tall, while it
diminishes the foliage; whereas the foliage of the isolated
tree expands, the stem being comparatively short. We
see, therefore, that the social state, so to speak, is of im-
portance in modifying forms. The use and disuse of
organs produce most marked effects: thus, the wings of
the domestic duck are lighter than those of the wild one,
whereas the legs of the domestic duck are heavier; the
difference being caused undoubtedly by the different habits
NA TURAL SELECTION.
147
of these animals. The rudimentary condition of the muscles
moving the external ear, in domestic animals, is no doubt
due to their disuse ; domestic animals not being, like wild
ones, continually on the watch for prey or enemies. Gym-
nasts illustrate well the effect of using the muscles, seden-
tary persons of their disuse. The development of the
mental faculties by their use is well seen in the domesticated
Dog and Horse as compared with these animals when in
a wild condition; while their degeneration through want
of use has been noticed in the domesticated Rabbit, whose
senses are not so keen as those of the wild one. Parasites
are interesting in this respect: thus, the young of many
parasites lead a free, active life, exhibiting often a complex
organization. In the course of time, however, in adopting
a parasitic mode of life they lose many organs, or retain
them only in a rudimentary condition. The greater develop-
ment of the bones, muscles, and nerves of the right hand
as compared with the left, is due, no doubt, originally to
greater use. This variation, like many others, has been
inherited by posterity, since the new-born child offers the
same difference in its hands. The thickened skin on the
soles of the feet and the palms of the hand (seen also in the
new-born child) has no doubt been acquired in the same
way. The eye which is most used in microscopy becomes
near-sighted, the other eye far-sighted. It must be borne
in mind, also, that variations beget variations; the different
organs of a plant or animal being so correlated that it is
impossible to modify one organ without sooner or later
some other organ becoming affected: thus, the increased
flow of blood to a part, through continual and violent
muscular action, may finally produce hypertrophy of the
heart. There are many variations, however, arising through
the correlation of organs, which cannot be so readily
explained: thus, certain Pigs and Dogs, who lose their hair
when taken to warmer climates, have their teeth affected.
148
EVOLUTION OF LIFE.
The Edentata are so called from the peculiar character of
their teeth; but the skin-covering of many of them, like the
Armadillo and Pangolin, is equally remarkable. Short and
compressed heads accompany short limbs, as seen in Pigs
and Cattle. The horned animals are without incisor and
canine teeth, as seen in the Ruminants, etc. ; while those
that have these teeth (like Pigs and the Musk-deer) never
exhibit horns. With the long legs of Wading-birds (Heron
and Stork) are associated long beaks. Dark-skinned, dark-
haired, and brown-eyed Europeans are less susceptible to
tropical diseases, and therefore more easily acclimatized, than
those with light skin, blond hair, and blue eyes. These
examples illustrate the important principle of one variation
entailing another through the correlation of organs. The
different modifications that we have mentioned are varia-
tions appearing in the parent, and often transmitted to the
offspring. But there are also variations which first appear
in the posterity, such as monstrosities, the difference of the
sexes, etc. Of these variations it is often difficult to say
whether they are produced by causes acting directly on the
parents, or directly on posterity, or indirectly through the
parents on posterity. While the causes of many variations
as well as their transmission to posterity are obscure or
unknown, it seems very probable that changes in Nutri-
tion are the causes of all variations, the term Nutrition
including the effects of Food, Climate, Social Relations, Use
and Disuse, Correlation of Organs, etc. ; while the facts of
Inheritance are to be explained by the laws of Generation,
of which as yet few are known. No doubt at some future
day Nutrition and Generation will be shown to be simply
physical and chemical phenomena. However that maybe,
the important fact is that “all organic individuals become
in the course of their life, through adaptation to different
conditions of existence, unlike one another, although the
NA TURAL SELECTION.
149
individuals of one and the same species remain mostly very
similar.”
SURVIVAL OF THE FITTEST.
Every one is aware that favorite breeds of cattle, many 1
beautiful flowers, particular kinds of horses, such as the
dray-horse, race-horse, etc., are not found in a wild state,
but that these forms have been gradually produced. Let
us examine the means by which this end has been accom-
plished. Suppose, for example, a gardener wishes so to
modify some particular white flower that in time it will ex-
hibit a striking scarlet color. He looks carefully among the
particular flowers until he finds one which offers a trace of
red; he plants the seeds of this flower, and from their pos-
terity he selects the reddest flowers. Continuing to select
the reddest flowers, and planting their seeds alone, finally the ^
gardener succeeds in obtaining one of a scarlet color. The
success of the gardener’s operation depends upon the fact
of there appearing, among the flowers which are usually
white, one exhibiting a faint red color, and upon the fact
of posterity inheriting from their parents a variation which
they transmit in turn to their offspring, this variation be-
coming more marked as it is transmitted from generation to
generation. An equally good illustration of this principle
is the often-quoted instance of Seth Wright, the Massachu-
setts farmer, who, noticing that one of his rams, with a long-
body and short bandy legs, could not jump over the fences,
concluded that it would be a good thing to breed with this
tram alone, and to his great satisfaction soon obtained a race ^
of sheep characterized by the peculiarity of a long body
and short bandy legs. Indeed, although the subject of
inheritance is still theoretically obscure, practically it is so
well understood that Sir John Sebright “ can produce in
three years a given feather, but that he requires six years in
order to obtain a particular kind of head and beak.” Now we
r
EVOLUTION OF LIFE.
150
know that variations appear among wild animals, and that
these variations are transmitted to their posterity. Is there
then also a selection in nature which brings about the same
results as that produced by man’s selection? Suppose, for
example, a number of plants are growing in a dry place,
it is evident that those plants whose leaves are most thickly
haired will be favored in the struggle for water, since the
hairs are useful in taking up moisture. These plants will
therefore survive and reproduce their kind, while those whose
leaves are deficient in hairs will die out. But in the next
generation some of the plants will be characterized by still
thicker hairs ; these will therefore be preserved and pro-
create ; but in the course of generations plants are produced
through this Natural Selection which differ very considera-
bly from the parent stock, not only in the hairing of the
leaves, but in other peculiarities, as one variation sooner or
later entails another. Thus the moisture taken up by the
hairs furnishes a large amount of nutriment, but if the nu-
triment is increased the flowering organs diminish ; but this
effect in the struggle for existence will bring about other
variations, and so on indefinitely. “The wingless condi-
tion of so many Madeira beetles is mainly due to the action
of natural selection, but combined probably with disuse.
For during many successive generations, each individual
beetle which flew least, either from its wings having been
ever so little less perfectly developed, or from indolent habit,
will have had the best chance of surviving from not being
blown out to sea ; and, on the other hand, those beetles which
most readily took to flight would oftenest have been blown
to sea, and thus have been destroyed.” Through the Sur-
vival of the Fittest, by Natural Selection, we see why animals
resemble in color, etc. their surroundings or the places they
live in. Thus, the Plant-lice and many insects are green,
like the leaves they live upon. The Jumping Mouse, Fox,
Lion, and Gazelle are yellow or yellowish-brown, like the
NA TURAL SELECTION.
15 I
sands of the desert they frequent. The Polar Bear, living
on ice and snow, is white or gray; but as the summer ad-
vances and the snow passes away, leaving the dark ground
exposed to view, the Bear changes his skin to a brown or
black, assuming again, as winter returns, its whitish hue.
Mr. Darwin explains these striking facts by showing that
the harmonizing of the color of an animal with its sur-
roundings is useful to it. For those animals being unob-
served are favored in the struggle for existence, seizing
more easily their prey, or escaping from their enemies more
readily, than those not so favored. Mr. Wallace, speaking
of the butterfly Kallima parapleta, says, “At length I was
fortunate enough to see the exact spot where the butterfly
settled, and, though I lost sight of it for some time, I at
length discovered that it was close before my eyes, but
that in its position it so closely resembled a dead leaf
attached to a twig as almost certainly to deceive the eye
even when gazing full upon it.” In reference to this sub-
ject, Prof. Haeckel notices the Helmichthys, fishes whose
bodies are so transparent that one can read a book through
them. The Carinaria among the Mollusca, the Salpa
among the Worms, many of the Jelly-fishes, are either bluish
or colorless as the water they live in. The transparent
glass-like color of these animals who live on the surface of
the open sea is evidently of service to them in catching the
objects of their prey or avoiding their enemies. Suppose
now the remote ancestor of one of these animals to have
been slightly transparent, a little more so than the indi-
viduals of the same species, it would have been favored in
the struggle for existence, and would have survived. Trans-
mitting this useful peculiarity, its posterity would be still
more transparent. Finally, in the course of generations,
almost perfectly transparent animals would be produced.
Prof. Cope observes, “The gray sand hue so well adapted
for concealment is universal, with few variations, in the
152
EVOLUTION OF LIFE.
reptiles of the Tartar and Arabian deserts, the Great Sahara,
and the sands of Arizona and California. There is also a
tendency to produce spiny forms in such places; witness
the Stellios and Uromastix and Cerastes of the Sahara, the
Phrysonomas and Horned Rattlesnake of Southwestern
America. The vegetation of every order, we are also in-
formed, is in these situations extremely liable to produce
spines and thorns.”
Every one is aware of the great difference in size and
color exhibited by the male and female of birds, butterflies,
etc., of male animals being armed with weapons, like the
horns of deer, the cock’s comb, etc. Mr. Darwin supposes
these organs to have arisen through what he calls Sexual
Selection. Thus, at breeding-time the number of male
deer exceeds that of the female; hence there is invariably a
fight, and the deer with the biggest horns gets the better of
his rivals : naturally their posterity will be characterized
by large horns. This process, continued through genera-
tions, finally results in the production of the antlers of the
male deer. But, as Mr. Herbert Spencer observes, large
horns require large muscles to move the head, large mus-
cles must be supplied with sufficient nutriment, which is
brought to them by large arteries, which necessitates a
powerful heart, and so on indefinitely. The voice of the
singing birds is supposed to have arisen in the same way,
for of the male birds those who sing best are chosen by
the females for their mates. The voice is therefore con-
tinually improved from generation to generation. The
male Crickets, Grasshoppers, Katydids are equally remark-
able for the noise they can make. The incessant “ Katydid
she didn’t” is produced by one wing being played on by the
other wing, like a fiddle and bow. “All observers agree
that the sounds serve either to call or excite the mute
females ;” and Mr. Darwin quotes Mr. Bates as stating that
the male of the European field-cricket “ has been observed
NA TURAL SELECTION.
153
to place itself in the evening at the entrance of its burrow,
and stridulate until a female approaches, when the louder
notes are succeeded by a more subdued tone, whilst the
successful musician caresses with his antenna; the mate he
has won.” Ornaments of the male animal, like the cock’s
comb, the peacock’s tail, the gorgeous plumage of the
paradise bird, the brilliant color of the male butterfly, are
made use of, like the weapons and musical tones just men-
tioned, in obtaining the female. The old Spartan principle
of killing the deformed and sickly, which resulted in the pro-
duction of a magnificent race of men, is the action of Sexual
Selection applied to man. Necessarily the offspring will
exhibit marked improvement in beauty of form, develop-
ment of talent, and powers of defense, if the fathers are
always selected from those who approach nearest the
standard of excellence.
Having illustrated now, we hope sufficiently well, the
selection brought about by man and nature, let us see
how they differ and in what they agree. Man selects
knowingly, with an object ; making use of variations,
he modifies for his own advantage. Nature eliminates
blindly, without an object, the organisms surviving being
better fitted for existence through some advantage. Thus
the Massachusetts farmer knowingly made use of the
variation of a long body and short bandy legs, exhibited
by one of his .rams, to produce a particular race of sheep.
But suppose the conditions of existence had been such
that the short-legged sheep had some advantage over
the long-legged ones in the struggle for existence, the
favored ones would have survived, and nature blindly
would have done in the long run what the farmer did
in a few generations. A similar case would be that of a
farmer who, having black and white pigs, wanted black
pigs only. To attain this object he would knowingly sepa-
rate the pigs, and breed from the black pigs alone. But if
1 54
EVOLUTION OF LIFE.
the farmer lived in Florida, and would turn his pigs in the
woods, nature would blindly bring about the same result,
since the white pigs would soon die, it being well known
that pigs eat “ the paint roots (Lachnanthes , which color
their bones pink, and which cause the hoofs of all but
the black varieties to drop off hence the squatters say
“we select the black members of a litter for raising, as they
alone have a good chance of living.” Suppose man to be
heartless enough to abolish all hospitals, almshouses, etc.,
soon nature would eliminate, as Sparta got rid of. the sickly
and deformed, the result being the survival of the fittest.
We have seen that there is a most complex struggle for
existence, that while like begets like, plants and animals
vary in their organization ; it follows, necessarily, that those
organisms whose variations give them an advantage in the
struggle for existence will survive, or be naturally selected,
while those not so favored will die out. We see, therefore,
that Natural Selection neither implies the existence of a
Natural Selector nor is the Survival of the Fittest effected
by chance. The facts of Inheritance are to be explained
by the laws of Generation, those of Variation by Nutrition.
The Struggle for Existence is caused by the number of
individuals that are born being out of all proportion to
the size of the earth they live in. The ever-changing
conditions of Nature have the effect of eliminating the
conservative kinds of life, while the pla c tic organisms sur-
vive and transmit their peculiarities to posterity. These
variations become more marked from generation to gener-
ation, until finally, in the course of ages, there result very
different forms of plant and animal life.
A good illustration of this whole subject is the history
of the Siredon and Amblystoma. The Siredon lichenoides
(Fig. 65) is a perennial gill-breathing Batrachian reproduc-
ing Siredons; the Amblystoma mavortium (Fig. 66) breathes
by lungs and reproduces Amblystomas. These forms were
NA TURAL SELECTION.
155
naturally supposed to be distinct kinds of Batrachians ; but
the experiments of Prof. Marsh and Prof. Dumeril have
demonstrated that changing the conditions of existence
has the effect of metamorphosing the Siredon into an
Amblystoma. The importance of these experiments may
bd appreciated by supposing that Tadpoles reproduced
Tadpoles in Nebraska or Mexico, and Frogs reproduced
Frogs in New Haven or Paris, and that anatomists regarded
the Tadpole as an entirely distinct Batrachian from the Frog;
but removing the Tadpoles to New Haven or Paris, and
changing the conditions of existence, the Tadpole turned
into a Frog: our hypothetical case is exactly that of the
Siredon and Amblystoma. As Professors Marsh and Du-
meril developed a lung-breather, the Amblystoma, from a
gill-breather, the Siredon, so we believe nature to have
developed the lung-breathing Frogs from gill-breathing
tadpole-like animals. Thus, in remote time, the condi-
tions of existence changing, some of these tadpole-like
animals changed into Frogs, while others remained un-
modified and reproduced tadpole-like animals. But as the
development of the individual Frog is the epitomized history
of the race to which it belongs, the developing Tadpole,
or the transitional stages of the Frog, are permanently
represented by animals like the Salamander and Proteus.
An important consequence of the Struggle for Existence
is the Division of Labor so characteristic of man, the
higher animals, and plants. Savages supporting them-
selves by hunting and fishing, while often acting in concert,
are, however, not dependent upon one another, so that the
sudden death of even many individuals does not cause any
inconvenience to the rest of the tribe. But in the civilized
state, where the crowding together of people diminishes the
means of subsistence and increases the number of rivals,
the Struggle for Existence soon differentiates the population
into growers of corn, hewers of wood, and carriers of water,
156
EVOLUTION OF LIFE.
as every one cannot work at the same trade, and the de-
pendence of one upon another becomes very great. This is
immediately seen if we consider the confusion that would
arise in a city if the butchers and bakers were suddenly to
die. But the community in general is not only differentiated
by the Struggle for Existence into divers interests, but, sooner
or later, the individuals are affected in the same way. For
the individual whose organization is most specialized and
whose functions are many is better fitted to maintain him-
self against the changing conditions of life than one whose
organization is more simple. But we have seen that one
variation entails another, and that the peculiarities of the
parents are transmitted to their offspring : hence in the
course of generations the organization becomes extremely
complex. Thus the Division of Labor is carried out to
such an extent in the organization of the human body that
it requires volumes to describe the anatomy of man. The
Division of Labor, or a complex organization, does not
necessarily follow from the Struggle for Existence; for there
are animals who, when young, lead a free active life, and
have quite a complex organization, but, growing older,
they adopt a parasitic mode of life, and then lose many of
their organs through disuse. Prof. Haeckel aptly observes,
“The traveler lightens his journey who throws away his
pack.” So of many parasites : the one who first gets rid
of any useless muscles or nerves will have the best chance
of surviving; complex conditions of existence bring about,
sooner or later, complex organization, while simple struc-
tures are the result of simple conditions of existence. Sup-
posing this view of Nature to be correct, the plants and
animals that first appeared on the earth ought to have
been simply and lowly organized, the later ones highly
complex. In our chapter on Geology we have shown that
such is the case, — that there has been a progress from
the lower to the higher forms of life, accompanied at the
NATURAL SELECTION.
IS 7
same time by retrograding metamorphoses, as seen in
parasites, etc.
While Natural Selection is generally admitted to be a
sufficient cause for the production of unimportant variations,
it is often objected that important structures, such as the
skeleton, could never be modified by such a process. Mr.
Darwin, however, has shown that the skeleton is as sus-
ceptible to modification as any other part of the organization.
Thus, the different kinds of pigeons, supposed unanimously
by “ fanciers” to have descended from different ancestors,
but which are now known to be the posterity of the Rock
Pigeon, offer great variations in their skeleton, as in the
number of their vertebrae and ribs, in the character of the
breast-bone, merry-thought, lower jaw, and bones of the
face. All zoologists admit that the various kinds of rabbits
have descended from a common stock ; and yet the greatest
difference is seen in the size, shape, and form of the skull,
in the character of the backbone, etc. But not only have
the changing of conditions and the domestication of animals
modified the skeleton, which is regarded by anatomists as
one of the most constant of characters, but the viscera and
all other parts of the organization have been affected. We
do not regard, therefore, the objection of Natural Selection
not being a sufficient cause of change as of any weight.
The fact of Hybrids often not breeding is regarded by
many as an important objection. The case of the mule not
breeding is usually referred to. This objection does not
seem to us to amount to much, as it is well known that the
Porto Santo rabbit, which is the offspring of the European
rabbits placed on that island in 1419, will not breed now
with the posterity of its European ancestor. Further, it
does not follow, because mules are unreproductive, that all
other hybrids have been, and will be. Thus, the Lepus
Darwinii, originally resulting from the crossing of the
Rabbit and Hare, now reproduces its kind, the animal
153
EVOLUTION OF LIFE.
being half Hare half Rabbit. According to Prof. Haeckel,
the pairing of the male Goat and female Sheep is very
common in Chili, their progeny being fertile; while the Ram
and female Goat rarely pair, and then without offspring. It
is well known that some animals when confined in menage-
ries, etc. will not breed. We see, therefore, upon what slight
differences reproduction depends.
The absence of links between the different forms of plants
and animals is often urged as an objection to the theory of the
Evolution of Life. The not finding of links is due very often
to not looking for them in the right place. Thus, a pigeon-
fancier, not finding a link between the Carrier and Pouter,
might have argued some years ago that they had descended
from the primitive Carrier and Pouter, of whose origin he
knew nothing. But it is well known now that these pigeons
are the posterity of a common ancestor, the Rock Pigeon.
Hence the transitional forms are between the Rock Pigeon
and the Carrier, between the Rock and the Pouter. We
have tried to show that the Struggle for Existence pro-
duces a divergence of character, so that in the course of
time the posterity differs greatly from the parent stock.
Now, if the intermediate animals die out, forms are left
which have little in common with existing animals. In
this manner may be explained the existence of such isolated
unique forms as the Elephant, Sloth, Giraffe, so readily
distinguished by their striking peculiarities. The Capu-
chins, among the South American monkeys, on the con-
trary, exhibit such a number of varieties, species, and genera
that it is almost impossible to classify them, the transitional
forms being so numerous. Many have argued that too
much time is required in the development of the animal
and vegetal kingdoms through the Survival of the Fittest.
Physical and Geological science cannot at present assign
any definite age to the Earth; and, from the rate at which
deposits are formed at the present day, millions and mil-
NA TURAL SELECTION.
159
lions of years would have passed away in the formation of
the Aqueous Rocks. So that, while admitting the loose-
ness of the data, we feel that we are less likely to err in
assuming an amount of time practically unlimited for the
development of life than if we attempt to fix a definite
limit. It is often asked, How could the instincts of animals
and man arise through a process like Natural Selection?
The manner in which the young uneducated Pointer ac-
quired the instinct of pointing explains the origin of all
instincts. The original Pointer was taught to point, and
in the course of generations, this peculiarity being inherited,
the pointing became instinctive. All of our ideas have
arisen in the same way, mind being the impressions of the
brain derived from the external world through the medium
of the senses. If there really be what metaphysicians call
“ a priori ideas,” originally they have been derived a pos-
teriori ; that is, these ideas were originally derived by the
parent organism, and later inherited by posterity. Finally,
to many persons, complex structures like the eye and ear
are insuperable objections to the theory of Natural Selec-
tion, it seeming incredible to those who are unacquainted
with Comparative Anatomy that such organs could have ,
arisen through the Survival of the Fittest caused by the ,
action of a blind, objectless, working Nature. The eye is
usually studied in a most developed state, as in man, for
example; but the visual organ of some of the lower animals
is only a pigment spot, more or less sensitive to the rays
of light, but incapable of forming the image of an external
object. As we ascend in the scale of life, we notice there
is added to this pigment spot a sensitive nerve, and as we
gradually progress there appears the lens, a light-refracting
organ, which, collecting the rays of light in a focus, deline-
ates the image of an external object. Still more highly
organized animals exhibit additional media of service in
transmitting the light, a complex retina for receiving the
?
iuo
EVOLUTION OF LIFE,
image, and special arrangements for the accommodation
of the eye to distances. By glancing, therefore, at different
animals, we see the eye in different stages of perfection.
But the gradual development of the eye of man offers a
series of transitional stages, which are permanently repre-
sented by the eyes of the lower animals. Now, if the eye
has gradually been perfected through the Survival of the
Fittest, we understand why the transitional stages in the
development of the eye of man have permanent represent-
atives in the eyes of the lower animals; but if the eye has
been created for the purpose of seeing, we neither under-
stand why such an extraordinary method is adopted in its
formation nor why it is not a perfect optical instrument.
The same reasoning will apply to the human ear as well
as to the eye, they both beginning as depressions in the
skin, which later, closing, form the primitive eye and ear
vesicles.
RESUME.
We tried to show in the chapters on Zoology, Botany,
Geology, and Embryolog-y, that the structure of plants and
animals, their petrified remains, and their manner of develop-
ment, are explained by supposing that life has* evolved, that
there has been a gradual development of the higher forms
of life from the lower, accompanied here and there by a
retrograding metamorphosis. In the early part of this
chapter we called attention to the facts of Geographical
Distribution not being consistent with a theory that sup-
posed plants and animals had been created for special
localities, but that they could be explained by supposing
that life migrated from place to place, being more or less
modified from time to time by the new conditions of exist-
ence, natural barriers being often the cause of the great
difference exhibited by plants and animals living under
similar conditions. The conclusion of an Evolution of Life,
NATURAL SELECTION.
161
arrived atby a comparison of many'biological generalizations,
we then tried to show was the necessary consequence fol-
lowing from the Struggle for Existence combined with the
effects of Inheritance and Variation : the resultant of
these three forces being what Mr. Darwin calls Natural
Selection. It must be remembered that Natural Selection
does not explain the facts of Inheritance and Variation, but
follows from them and the Struggle for Existence. The
facts of Inheritance and Variation seem to depend upon
Generation and Nutrition, which are chemical and physical
phenomena still involved in much obscurity. Before leav-
ing the subject, it seems proper to mention, as it does not
appear to be generally understood, that the theory of the
Evolution of Life may be accepted as true, and yet Natural
Selection not be considered as a sufficient explanation.
Suppose, now that the attention of naturalists has been
drawn to the theory of Evolution, that most careful obser-
vations are made in reference to this subject, and that all
biologists become convinced in time that plants and animals
gradually change, the flora and fauna of a remote future
differing very considerably from those of the present day, —
the theory of the Evolution of Life might be demonstrated,
and yet it might be shown that Natural Selection did not
entirely produce it, or indeed the cause might still remain
unknown. Let us repeat, then, that whatever may be
thought of the causes advanced, as sufficient to bring about
a development of life, the theory of Evolution remains
the only explanation of the most important generalization
of the comparative anatomy of plants and animals, their
Paleontology, Embryology, and Geographical Distribution.
IX
ANTHROPOLOGY.
If it be admitted that the different kinds of existing ani-
mals are the modified descendants of pre-existing animals,
then it follows necessarily that if man is an animal he
must have descended from some pre-existing animal. Sup-
posing the theory of the Evolution of Life to be true, the
important question to be decided is not whether there are
any transitional forms or links between man and this or
that kind of animal, — though of course the discovery of such
links would be weighty additional evidence, — but whether
man is an animal, whether the difference between man and
the members of the animal kingdom is one of kind or only
of degree. Since man has a backbone, he is a vertebrate,
and, as he is suckled when young, he is a mammal. Thus
far naturalists are agreed as to man’s place in Nature. The
question, however, of determining the particular order of
mammals to which man belongs, has given rise to much
discussion. Linnaeus united in one group the half Mon-
keys (Lemurs), the Bats, the true Monkeys, and Man, call-
ing them Primates. Blumenbach, however, joined the true
Monkeys with the half Monkeys, calling them Quadrumana,
or the four-handed order, while he regarded Man as the
representative of a distinct order, the Bimana, or two-
handed; the term four-handed was adopted by Blumen-
bach from the older writers. This classification was ac-
cepted by Cuvier and most contemporary anatomists, though
always regarded as incorrect by Geoffroy St. Hilaire, who
( 162 )
785 786 787
GYNOCEPHALUS
ANTHROPOLOGY.
163
considered the higher apes to be more nearly allied to man
than to the lower monkeys. The untenability of Blumen-
bach’s classification becomes at once evident, on reflecting
that no one would argue that the Chinese boatmen and
Bengalese artisans are four-handed because they can row
and weave with their feet. We would only say these
people use their feet as hands. No one regards the hands
of the Colopus and Ateles as feet because in these mon-
keys the thumb is so rudimentary (or absent) that its
opposability to the hand is impossible. We see, therefore,
that if the mobility of the thumb or big toe be accepted as
a test of an extremity being a hand or a foot, we should
have to admit the existence of four-handed people, and of
monkeys having feet where their hands usually are, and
vice versa. Prof. Huxley has, however, shown that there
is as much difference anatomically between the foot and
hand of the monkeys as between the foot and hand of man.
The essential difference of a hand, as compared with a foot,
consists in the characteristic arrangement of the bones in
the two members, and the presence or absence of certain
muscles. Accepting this test as the correct one, monkeys
as well as men are two-handed and two-footed. Prof.
Huxley has also demonstrated “that the structural differ-
ences which separate Man from the Gorilla and the Chim-
panzee are not so great as those which separate the Gorilla
from the lower Apes.” This is at once seen on comparing
Figs. 182 to 193, representing the skull, teeth, hand, pelvis,
and foot of a Man, of a Gorilla, and of some other monkey.
While it is admitted that there are gaps between Man and
the Gorilla, between the Gorilla and the Orang, between
the Orang and lower monkeys, the differences, however,
are not sufficiently great to admit of making distinct
orders : hence Man and the Gorilla, etc. must be considered
as members of the order of Monkeys.
We concluded our chapter on Zoology by noticing the
164
EVOLUTION OF LIFE.
half monkeys, represented by the Galeopithecus, Cheiromys,
and Lemurs, stating of this group that the Loris seemed
to furnish the transition to the true monkeys. Let us
now consider these a little. The true monkeys are
usually divided into the Catarhines, or the monkeys of
the Old World, including the Gorilla, Chimpanzee, Orang,
Gibbon, Magots, Macaques, Baboons, etc., and the Platy-
rhines, or those of the New World (confined to South
America), among which are found the Howlers, Spiders,
Capuchins, and Marmosets. The terms Catarhine and Platy-
rhine refer to the nostrils, which in the Catarhine look
downward, but in the Platyrhine are flattened. In the
peculiarity of the downward nostrils Man agrees with the
Catarhine monkeys. Further, all Catarhines have thirty-
two teeth, which is also the dental formula of Man ; whereas
the Platyrhines have thirty-six, the Marmosets excepted,
in which the third true molar is rudimentary. These little
monkeys offer also the peculiarity of having claws on their
fingers and toes. We see, therefore, of the two groups of
monkeys that Man, from the position of his nostrils and
the number of his teeth, belongs to the Catarhine.
Having briefly called attention to some of the peculiarities
of the human skeleton, etc., as compared with that of the
Gorilla and other monkeys, let us now compare the brain
and mental powers of Man with those of the lower animals.
While no one understands how the physical impression of
an external object conveyed to the brain through the senses
gives rise to an idea, or becomes thought, every one admits
that without the brain there can be no thought; and by a
comparison of the mental powers in different kinds of
animals, we conclude that the relative perfection of mind
depends on the relative perfection of brain. Thus, in Bees
and Ants, which have long been famous for their intelli-
gence, the nervous system is more highly developed than
in any other members of the Articulata. In speaking of
ANTHROPOLOG V
165
Ants, Mr. Darwin says they “communicate information to
each other, and several unite for the same work, or games
of play. They recognize their fellow-ants after months of
absence. They build great edifices, keep them clean, close
the doors in the evening, and post sentries. They make
roads, and even tunnels under rivers. They collect food
for the community, and when an object too large for
entrance is brought to the nest they enlarge the door, and
afterwards build it up again. They go out to battle in
regular bands, and freely sacrifice their lives for the com-
mon weal. They emigrate in accordance with a precon-
certed plan. They capture slaves. They keep aphides as
milch cows. They move the eggs of their aphides, as well
as their own eggs and cocoons, into warm parts of the nest,
in order that they may be quickly hatched ; and endless
similar facts could be given.” It is incredible to suppose
that animals could accomplish such feats without mind of
some kind.
The brain of the Fish is small compared to the spinal
cord of which it is the continuation, and the parts of which
it is composed are so arranged that no one part obscures
the other. In Reptiles the brain is larger, and the Cerebral
Hemispheres, the seat of the higher mental activities,
slightly predominate over the other parts of the brain.
This peculiarity becomes more marked in the Birds; while
the Cerebral Hemispheres of the lower mammalia, like
the Ornithorhynchus and the Opossum, quite overlap parts
perfectly visible in the Fish. Ascending through the orders
of the Mammalia, the Cerebral Hemispheres continue to
overlap the other parts of the brain, until finally in the
higher Apes and Man they entirely cover the Cerebellum,
Medulla Oblongata, etc. By comparing the mental powers
of the different Vertebrata, we see that the gradual develop-
ment of the brain is accompanied by a corresponding de-
velopment of mind. The low grade of intelligence of the
EVOLUTION OF LIFE.
1 66
Fish depends on its low cerebral organization, the mental
activity of the Dog is due to its comparatively highly com-
plex brain. Every sportsman can give numerous illus-
trations of dogs reasoning. Mr. Darwin quotes Colonel
Hutchinson as his authority for the following example:
“ Mr. Colquhoun winged -two wild ducks, which fell on the
opposite side of a stream ; his retriever tried to bring over
both at once, but could not succeed. She then, though
never before known to ruffle a feather, deliberately killed
one, brought over the other, and returned for the dead
bird.” The every-day fact of a dog hiding a bone implies
Prudence, Anticipation, and Memory. According to Mr-
Darwin, the muleteers in South America say, “ I will not
give you the mule whose step is easiest, but la mas racional,
the one that reasons best.” Those who are familiar with
' the habits of Monkeys are always impressed by their intel-
ligence. Buchner, quoting many reliable authorities, says
of the Orangs, living tame on board ship, that they will
wear clothes, uncork bottles, assist the sailors in fixing the
sails and unloading cargoes, will sew with them, dust the
furniture, and even light the fire and help cook. It seems
impossible that these Apes could learn through imitation,
or be taught so much, without having reasoning powers.
That the Orang should be so intelligent is not at all
extraordinary when we remember that his brain is so much
like that of Man. A glance at the brain of the Orang,
the Hottentot Venus, and Gauss the mathematician (Figs.
194, 195, 196) demonstrates that the brain of the Hottentot
was more like the Orang’s than that of the mathematician.
According to Vulpian, “the real differences which exist
between the brain of Man and that of the superior monkeys
are very small. One must not have any illusions in this
respect. Man is much nearer the Anthropoid Apes in the
anatomical character of his brain than these are, not only
to other mammals, but even to certain quadrumana, like
PROFILE VIEW OFTHE BRAIN OF THE ORANGOUTANG
/95
196
PROFILE VIEW OFTHE BRAINOFTHE HOTTENTOT VENUS
PROFILE VIEW OFTHE BRAIN OF GAUSS
A NTHR O POLO GY
1 67
the Guenons and Macaques.” Prof. Huxley calls attention
to the differences between the cranial capacity of different
races of mankind being far greater than between the lowest
Man and the highest Ape. Thus, the highest human skull
measured by Morton, containing one hundred and fourteen
cubic inches, compared with the lowest, containing only
sixty-three cubic inches, gives us a difference of fifty-
one cubic inches; while a Gorilla’s skull, containing
thirty-four and a half inches, compared with the lowest
human skull just mentioned, gives us a difference of only
twenty-nine and a half cubic inches.
Let us consider now briefly the habits and mental powers
of some of the barbarous races of mankind. Among these
probably stand lowest the Australians and the inhabitants
of the adjoining islands, the Bushmen, the Hottentots, and
some of the Negro races. The languages of these races are
among the poorest known, they having no abstract words,
like animal, plant, color, sound, each animal and each plant
being designated by a particular name. The mind of
these people is so little developed that there are no abstract
ideas of which such abstract words are the corresponding
expression. As quoted by Buchner, De la Gironniere says
of the Ayetas of the Philippine Islands, “ that they gave
him the impression of being a great family of monkeys :
their voice recalled the short cry of these animals, and
their movements strengthened the analogy.” According to
Buchner, “the language of the savages of Borneo is rather
a kind of warbling or croaking than a truly human mode
of expression and Sir Emerson Tennent relates of the
., Veddahs of Ceylon “that they communicate among them-
selves almost entirely by means of signs, grimaces, guttural
sounds, resembling generally very little, true words, or true
language.” Some of these races, as the Australians, for
example, cannot count over four or five. Many barbarous
tribes live in trees, eating fruits, roots, worms, flies, etc. ; they
i68
EVOLUTION OF LIFE.
herd together, having no idea of marriage or family life.
As quoted by Buchner, Krapf, the missionary, in speaking
of one of the Abyssinian tribes, says, “ The Dokos are
human pygmies ; they are not more than four feet high;
their skin is of an olive-brown. Wanderers in the woods,
they live like animals, without habitations, without sacred
trees, etc. They go naked, nourishing themselves by roots,
fruits, mice, serpents, ants, honey ; they climb trees like
monkeys. Without chief, without law, without arms,
without marriage, they have no family, and mate by chance
like animals; they also multiply rapidly. The mother,
after a very short lactation, abandons her child to itself.
They neither hunt, nor cultivate, nor sow, and they never
have known the use of fire. They have thick lips, a flat-
tened nose, little eyes, long hair, hands and feet with
great nails, with which they dig the soil.” Lallemand,
in speaking of the Botocudos, a tribe of Brazil, says, “ I
am sadly convinced that there are monkeys with two
hands.” The Negritoes, a race inhabiting the Philippine'
Islands, are regarded by those who live in Manilla as
monkeys. According to Buchner, “ the toes of these
savages, who live partly in grottoes, partly on trees, are
very mobile, and more separated than ours, especially
the great toe. They use them in maintaining themselves
on branches and cords as with fingers.” As we would
naturally expect, the unanimous testimony of those who
have lived among these races is that all attempts at civiliz-
ing such beasts have utterly failed. As these statements
may appear somewhat exaggerated to those who are not
familiar with the results of ethnological research, we content
ourselves with referring such to the works of Lyell, Lub-
bock, Rolle, Haeckel, and Buchner, on Man. Buchner quotes
no less than twenty-five well-known writers, including mis-
sionaries, naturalists, philologists, travelers, as entirely con-
firming his statements respecting the low mental state ot
ANTHROPOLOGY.
169
savages. If we now compare the mental powers of the
higher animals, such as those of the Horse, Dog, Elephant,
Monkeys, with those of such savages as we have mentioned,
and these with the most cultivated of men, we come to the
conclusion that the difference is certainly much less between
the higher animals and the lower races of mankind than
between these and men like Shakspeare, Newton, Hunter,
Voltaire, La Place, Cuvier, Goethe, Gauss, Muller. *
We hope now to have shown that the difference between
Man and the other members of the animal kingdbm is not
one of kind, but only one of degree. Notwithstanding the
great differences exhibited by the races of mankind in color,
hair, skin, skull, teeth, mental and moral powers, every one
admits that the civilized have descended from the bar-
barous races; the Australian of the present day, for ex-
ample, representing pretty well the ancient Briton. But
we hope to have shown that the difference between a New-
ton and an Australian is much greater than that between
an Australian and the higher Apes. It follows, therefore,
that if a Newton could be developed from an ancient Briton,
or his living representative an Australian, an Australian
could be developed from an Ape.
We began this chapter by stating that supposing the theory
of the Evolution of Life to be true, the animal descent of
man was a necessary consequence, and therefore the absence
or presence of transitional forms was comparatively unim-
portant. In trying, however, to show that man differs
from animals only in degree, not in kind, we hope to have
made out a series of transitional forms, beginning with the
lower monkeys and ascending from them, through the
higher apes and the lower races of mankind, to the higher.
Thus, the skulls of the Chimpanzee, Idiot, Negro, and Cal-
muck, offer a series of ascending forms. By comparing Figs.
197, 198, 199, 200, it will be seen that the receding fore-
head, which is a striking feature in the skulls of Negroes
170
EVOLUTION OF LIFE.
and of the lower races, is still more marked in the Idiot
and Chimpanzee. This type of skull is known as the long
head, or dolichocephalic ; that of the Calmuck, in which
the forehead is developed, as the short head, or brachy-
cephalic. Further, in the Negro the teeth are not set
straight (orthognathous) as in the Calmuck, but the teeth
of the upper jaw make an acute angle with those of the
lower jaw (prognathous). The receding of the forehead
and the angular arrangement of the teeth are accompanied
by a receding of the lower jaw (see Figs. 201, 203, 204), and
great development of jaws. In these peculiarities, the lower
races resemble the apes, and differ from the higher races
of mankind. The beastly and ferocious appearance of some
savages and apes is principally due to this excessive devel-
opment of the jaws. The large size of the canine teeth is also
a striking feature in the skull of apes; but, as Prof. Haeckel
observes, in comparing many human skulls, one always
notices that the canine teeth project in some more than
others ; and Mr. Darwin aptly says, “ he who rejects with
scorn the belief that the shape of his own canines, and
their occasional great development in other men, are due
to our early progenitors having been provided with these
formidable weapons, will probably reveal, by sneering, the
line of his descent ; for, though he no longer intends,
nor has the power, to use these teeth as weapons, he will
unconsciously retract his ‘ snarling muscles’ (thus named
by Sir C. Bell) so as to expose them ready for action, like a
dog prepared to fight.” The different size of the molar teeth,
according to Buchner, is also important : in civilized men, of
the three last teeth or molars the first is the largest, whereas
in the Chimpanzee the last is the largest; the lower races
o' mankind are intermediate in this respect, the three
molars being equally developed. Now, it is an interesting
fact that, in the milk teeth, the last molar is the largest, as
in the Chimpanzee, illustrating the law which we have had
JAW OF MODERN PARISIAN
JAW OF LA NAULETTE
JAW OF CHIMPANZEE
JAW OFMtLANESIAN
204
ANTHROPOLOGY.
171
occasion so often to mention, that the lower animals retain
permanently forms that are only transitory in the higher.
We see further examples of this principle in the receding
of the forehead and jaws, which are only exhibited by
the skulls of the higher races in their embryonic or un-
developed condition, in the learning of the child to walk, and
in the development of speech. The erect position of man
is often regarded as an objection to his having descended
from a lower animal. But as it is evidently an advantage
for man to use his hands for grasping, etc., but his feet to
stand and walk upon, we can understand how, through the
Struggle for Existence, etc., this division of labor was
brought about. The view of the erect position having been
gradually assumed by man is confirmed by such facts as
the creeping on all-fours of the baby and the shuffling
unsteady gait of the young child. The baby, at the first
month, uses its foot like a hand, and it is well known that
some savage people retain the mobility of the big toe, using
it as a thumb and the other toes as fingers; further, the
unsteady sidelong step of the child learning to walk is
seen in the semi-erect gait sometimes assumed by the
Gibbon and Gorilla. The young Chimpanzee, walking along
hand-in-hand with his keeper, resembles so strongly a little
negro learning to walk, that it is impossible not to recog-
nize their distant cousinship. In a word, the transitory
stages through which an individual man passes in learning
to walk represent the stages through which man in general
has passed in assuming the erect position, the transitory
stages being permanently retained in the lower animals.
It is admitted by all that articulate speech is peculiar to
Man. The possession of this faculty, however, does not
seem to be inconsistent with the view of his animal descent.
It is well known that animals communicate their ideas by
means of touch, sounds, etc.: thus, the Dog barks in differ-
ent ways, expressive of pain, anger, joy, despair, entreaty.
172
EVOLUTION OF LIFE.
Cows, cats, pigeons, chickens, give vent to their feelings by-
sounds. Language, or the expression of one’s thoughts, is
therefore common to man and the lower animals. Let us
see now what light is thrown on the origin of articulate
speech, or the peculiar language of Man, by comparing its
development in the child with the languages of different
races. It must be remembered that intelligent speech de-
pends as much on the development of the brain as of the
vocal organs, for Parrots and Ravens can talk. Naturally,
then, words are wanting if there are no ideas to give rise to
them. Hence the poorness of the languages of savage
races, and the simple talk of the child. Further, one hears
few verbs, prepositions, or conjunctions, in listening to the
prattle of young children : their expressions are almost
entirely composed of nouns and adjectives, — thus, “ sugar
good,” “ toy nice,” and so on. The language of savage nations
is equally simple, often not rivaling even that of the children
of the civilized. Hence celebrated philologists, like Grimm,
Schleicher, Bleek, regard language as progressive, consid-
ering the most ancient languages as much more simple than
the modern ones. They maintain that language is not an
art, but a natural growth arising from the necessity felt by
man of having some means of communicating his ideas.
According to Schleicher, the most simply constructed lan-
guages have been slowly developed out of the natural cries
that Man has in common with animals. He considers that,
in the lapse of ages, languages experience great modifica-
tions, some, indeed, altogether dying out, others becoming
so changed that their origin cannot be certainly determined;
that, comparatively speaking, language is a recently acquired
faculty depending on development of brain and vocal organs ;
primitive Man having no language excepting the natural
cries inherited from his Ape ancestors. Accepting this
theory, we have an explanation of the fact that the roots in
the languages of the lowest races of mankind resemble the
ANTHROPOLOGY.
173
sounds made by monkeys. Indeed, according to some
authorities, the language of the Papuans is much more
like that of the Monkeys than that of Shakspeare. Philo-
logical facts like those here only briefly mentioned lead us
to the conclusion that the development of language in an
individual of the higher races is the history of the develop-
ment of language in general. It is sometimes said that
the faculty of speech entirely separates Man from the
Monkeys. But this difference, like all others, is only one
of degree, not one of kind. The vocal organs are well
developed in Apes, the Gibbons shouting to each other as
they swing through the woods. To take Mr. Darwin’s
example, one might as well argue that the Crow is not a
bird, because it croaks, whereas the Nightingale sings.
Having mentioned some of the peculiarities of the structure
and development of man in reference to his animal descent,
let us now call attention to the importance of certain
human remains in this respect. Through modern discov-
eries made in France, Belgium, Germany, etc., the remains
of races of men have been brought to light, which without
doubt have long since been extinct. Now, it is a very
significant fact that the skulls of these primitive races ex-
hibit a very low type of organization. According to Prof.
Schaffhausen, “ the form of the forehead of the Neanderthal
skull (Fig. 205), the dentition and form of the jaw of La
Naulette (Fig. 202), the prognathism of some infantile jaws
of the stone period of Western Europe, exceed, as regards
their animal form, that observed in living savages.” Further,
according to the same high authority, “ these characters
must not be considered as accidental exceptions from the
normal form, which was the common theory on meeting
with such finds ; for these peculiarities in the organization
of the pre-historic man do not occur as exceptions, but as
a rule ; and what is decisive is the circumstance that they
mostly present a foetal character, and thus exhibit an early
174
EVOLUTION OF LIFE.
stage of development. They also frequently stand in
reciprocal dependence; one character determines the
other, according to the law of harmony or coexistence which
governs the form of all living bodies. With the flying
forehead, we find, as a rule, a projecting jaw, large teeth,
a high temporal line, a strongly developed occipital ridge,
simple cranial sutures, small cranial capacity.” Mr. Carter
Blake, in describing the jaw of La Naulette (Fig. 202), so
called from being found in the hole of the same name,
says, “ Its undoubted resemblance to the jaw of a young
ape I shall not venture to deny.” In speaking of the molar
teeth we stated that they were of equal size in the lower
races of man, but that the last molar was the largest in the
milk teeth of man and in the adult Chimpanzee. In reference
to these facts, the jaw of La Naulette is extremely interest-
ing, since its last molar is the largest, agreeing in this
respect with that of the Chimpanzee and milk teeth of
Man ; the tooth also exhibits the remarkable peculiarity
of having five roots, as is the case with the last molar of
the Gorilla and Orang. Further, in the great size of the
canine teeth, and the absence of the chin, the jaw of La
Naulette resembles in a marked degree that of the Chim-
panzee. An important distinction between the molar and
premolar teeth in man is that the molar teeth have three
roots, while the premolars have only two ; but a very ancient
human skull found at Olmutz exhibits, according to Schaff-
hausen, the peculiarity of the second premolar having
three roots, as is the case in the premolars of the Apes.
According to the same author, this is also seen in two
human skulls belonging to the Gottingen collection. In
comparing the human bones and cranium brought from the
cave of Neanderthal with other specimens, Prof. Schafifhausen
says they “ exceed all the rest in those peculiarities of con-
formation which lead to the conclusion of their belonging
to a barbarous and savasre race,” and at the conclusion of
ANTHROPOLOGY.
175
his address on the primitive form of the skull, translated
in the Anthropological Review, we find “ it follows further
that we must place the primitive man lower in the scale
than the rudest savage. The Neanderthal skull and the La
Naulette jaw present characters of a low organization such
as we do not find in any living race.”
Want of space prevents us from dwelling further on this
subject. Suffice it to say that what is known of the re-
mains of primitive man confirms the view of his animal
descent. From the transitory stages through which man
passes in his development being more or less permanently
retained in the lower animals, from his organization exhib-
iting in a rudimentary condition structures which are fully
developed in the lower animals, from abnormal characters
such as certain muscles appearing in man which are usually
only present in monkeys, we concluded in our chapter on
Embryology that man had descended from some animal
form. That this animal form, or the remote ancestor of
man, was an ape, we have tried to show in this chapter by
comparing the higher apes with the barbarous and the
civilized races of men, the result of this comparison being
that the barbarous races are more nearly allied to the
higher apes than to the civilized man.
While accepting the theory that man has descended
from an ape, it is impossible, however, to designate any
particular ape as his remote ancestor. The apes that most
resemble man are the Gorilla, Chimpanzee, Orang, and
Gibbon, hence called Anthropoid Apes. Their features
are very like those of the lower human races. (See plates
of faces of men and monkeys.) No evolutionist, however,
so far as we are aware, supposes man to have descended
from one of these apes. For while each of these apes has
something in common with man, each differs from him
very considerably. Thus, the Gibbon resembles man in the
thorax ; the Orang, in the brain ; the Chimpanzee, in the
176
EVOLUTION OF LIFE.
\
EXPLANATION OF PLATES
OF
FACES OF MONKEYS AND MEN.
NATIVE COUNTRY.
Fig.
1.
Baboon
tt
2.
Pig-faced Baboon
it
3-
Macaque
ft
4-
Semnopithecus
tt
5-
Nasalis
a
6.
Gibbon
tt
7-
Orang, young (female)
tt
8.
Orang, old “
tt
9-
Chimpanzee, young (female)...
tt
IO.
Chimpanzee, old “
tt
II.
Gorilla, young (female)
ft
12.
Gorilla, old “
ft
13-
Papuan (female)
ft
14.
Hottentot “
ft
15-
Cadre “
ft
16.
Negro “
ft
17-
Australian (male)
ft
iS.
Malay (female)
ft
19.
Mongolian (male)
tt
20.
Arctic (female)
ft
21.
American (male)
ft
22.
Drave “
ft
23-
Nubian “
ft
24.
European “
4
\
1
206 207 20 # 209
J
gibbon orang chimpanzee gorilla man
ANTHROPOLOGY.
1 77
skull; the Gorilla, in the hand and foot. Further, these
apes have a rudimentary tail, like that of man. (Figs. 206
to 210.) By comparing the skeletons of man and the apes,
the differences will be found to be also very striking. (See
Figs. 206, etc.) The more probable theory of the relation-
ship of man to the Anthropoid Apes is that they are very
distant cousins, the posterity of a common ancestor of
some extinct form whose remains have not as yet been dis-
covered.
The birthplace and antiquity of man, like his genealogy,
are still involved in obscurity. Many geologists and
naturalists, however, suppose that there once existed a
continent where the Indian Ocean now rolls, which
stretched from the Sunda Islands to Madagascar. This
sunken land is called by Sclater, Lemuria, from the half
monkeys, the Lemurs and their allies, being so characteristic
of Madagascar and the Indian Archipelago. This view of
a land of Lemuria having once existed harmonizes veiy
well with the evidences of Ethnology, Philology, etc.,
which point to some intermediate spot between Southern
Asia and Eastern Africa, like Lemuria, as the birthplace
of the human species. As regards the antiquity of man,
the data are so imperfect that it is impossible to give an
estimate. Some authors think man appeared in the latter
period of the Tertiary Age ; according to others, still
earlier. However this may be, it is certain that immense
periods of time must have elapsed since the appearance
of man.
Those who are impressed with the poetical idea of a
Golden Age, from which man has fallen, no doubt find
it difficult to admit that he has descended from an ape.
The explorations of the last forty years, however, have
proved that so far from there having been a Golden Age,
the first age was that of Stone (the implements being made
jut of stone, hence the name of the age), followed by one
i 7 8
EVOLUTION OF LIFE.
I of Bronze, a further progress being exhibited in the Age
of Iron. Ethnologists consider the primitive man to have
been lower than the lowest of existing savages, more ape-
like even than the extinct human races, whose remains we
have briefly noticed. According to philologists, the primi-
tive man was speechless, and the earliest languages babble.
All kinds of evidence negative the idea of man having
fallen from a high estate, but support the view of his having
i developed from a lower one. The descent of man is indeed
an ascent.
It does not seem out of place to briefly call attention
to the probable spreading of the human species over the
earth, which, according to Prof. Haeckel, was as follows.
Starting in Lemuria (see plate on distribution of races),
the posterity of the primitive men diverged towards Africa,
Australia, the Indian Archipelago, and Asia ; the Hot-
tentots, Caffres, and Negroes being the descendants of
those who came to Africa, while the Papuans, Australians,
and Malays are equally the posterity of three stems.
Diverging from the Malay stem appeared the Drave and
Mongolian races. The Draves, peopling India, passed
towards Arabia, and 'divided into the stems of the North
African races and Europeans; while the Mongolians, passing
through China and spreading over Northern and Eastern
Asia, finally crossed over Behring Straits and peopled the
Americas. This view of the gradual spreading of the races
of men from a common point situated between Asia and
Africa seems to be a fair conclusion from what is known
of Ethnology and Philology.
While admitting that the different races have descended
from a common stock, it does not necessarily follow that
the primitive men came from a single pair. Thus, possibly,
different apes may have been the ancestors of the Malay
and South African races. It is interesting in this respect
to observe that the Orang, who is found in the Malay
A NTHR O POLO GY.
179
Archipelago, is of a yellowish color, and is brachycephalic
in the form of the skull, like the Malays, whereas the Chim-
panzee, found in Africa, is black and dolichocephalic, like
the Negroes. At present it seems to us impossible to say
which is the more probable, whether the primitive men
came from one pair of apes, or many. In either case,
however, they had a common origin, since the apes are the
posterity of a common ancestor.
The kindred question of the origin of the different languages
from one or many roots depends on the period at which the
primitive men first acquired language. For if language
was acquired by the primitive men before their posterity
had dispersed, then the different languages would have had
a common origin ; whereas if the races had dispersed be-
fore their ancestors had acquired a language, then the
languages of these races would have arisen independently.
In conclusion, it seems proper to mention that the de-
scent of man from some ape-like form is perfectly consistent
with the development of morality. As we noticed in the
last chapter, among barbarous tribes there is no dependence
of individuals upon each other, the character of the daily
life of savages being such as not to offer much chance of
their mutually benefiting each other; while the uniting of
barbarians, for the purpose of attacking some other tribe, is
unfavorable to the development of sympathy and kind
feelings towards mankind, since war encourages murder,
robbery, and crime of all kinds. We have shown, how-
ever, that in the social state the relations of man to man
are so complex that no one is independent of his fellow-
men. To such an extent is the division of labor carried
out in highly civilized countries that even distant nations
have many interests in common. This is so true of some
countries that war is dreaded and has been avoided by them,
every one knowing that the effects would be very injurious
to both the victorious and conquered. Notwithstanding
i8o
EVOLUTION OF LIFE.
that the effect of the social state is the restraining of men’s
evil passions, nevertheless crimes and outrages are com-
mitted even among the most civilized, — simply, in the
words of Mr. Spencer, because man “partially retains the
characteristics that adapted him for an antecedent state.
The respects in which he is not fitted to society are the
respects in which he is fitted for his original predatory life.
His primitive circumstances required that he should sacri-
fice the welfare of other beings to his own ; his present
circumstances require that he should not do so; and in as
far as his old attribute still clings to him, in so far is he
unfit for the social state. All sins of men against each
other, from the cannibalism of the Carib to the crimes and
venalities that we see around us, have their causes com-
prehended under this generalization.” The same author
then argues that as the gratification of passions increases,
whereas the restraining of passions lessens, desire, and that
the faculties develop through use, but diminish through
disuse, man must improve, as his organization is becom-
ing continually better fitted to his surroundings, “ all evil
resulting from the non-adaptation of constitution to condi-
tions.” We see, therefore, that progressive morality is a
necessary consequence of the Evolution of Life.
RESUME.
We conclude, from the general theory of the Evolution
of Life, from the facts brought forward in this chapter and
in the two preceding ones, that man has descended from
an animal ; that the remote progenitor of man was an ape,
resembling the Gorilla and Chimpanzee ; that the birthplace
of man was situated somewhere between Southern Asia
and Eastern Africa, in Lemuria, if such a continent existed ;
that myriads of years have rolled by since man appeared
on the earth; that the primitive men exhibited a grade of
I
A NTHR O POLO GY 1 8 I
organization lower than the lowest of existing savages ; that
the different races of men have descended from a common
stock; and that the physical, mental, and moral improve-
ment of man is the necessary consequence of the Evolution
of Life.
The doctrine of the Evolution of Life has this, then, in its
favor : that it is a comprehensive theory of Life, — a theory
on which can be based a scientific Ethics and a scientific
Politics; and as all happiness depends on duty to one’s
self (Ethics), and therefore duty to one’s neighbor (Politics),
it follows that a theory which offers a basis for the develop-
ment of these social sciences must immeasurably benefit
mankind.
“To thine own self be true ;
And it must follow, as the n'ght the day,
Thou canst not then be false to any man.
Farewell ; my blessing season this in thee.”
I
IGUR
I
2
3
4
S
6
7
8
9
io
ii
12
13
14
i5
16
17
18
19
20
21
22
24
25
26
27
28
29
list of authorities.
zoology.
Author from
WHOM TAKEN.
Haeckel.
a
it
tt
tt
a
a
it
Micrographic Dictionary.
Huxley.
Cuvier.
Huxley.
Owen.
Cuvier.
Gegenbaur.
a
Owen.
Carpenter.
Rymer Jones.
No. OF
Figure.
3 °
31
32
33
34
35
3 6
37
38. 38*
39
40
41
42
43
44
45
46
47
48
ti tt
Gegenbaur.
it
Huxley.
Micrographic
ti
Dujardin.
Gegenbaur.
ti
Dictionary.
If
49
5 °
51
52
53
54
55
56
57
Author from
WHOM TAKEN.
Rymer Jones.
« <<
Gegenbaur.
Rymer Jones.
Quatrefages.
Ehrenberg.
Huxley.
Gegenbaur.
Haeckel.
it
it
it
Rymer Jones.
Haeckel.
Rymer Jones.
Haeckel.
Brown.
tt
it
it
Muller.
Rymer Jones.
a a
Gegenbaur.
Cuvier.
Vienna Pop. Nat. Hist.
Vienna Atlas.
Brown.
(183)
1 84
LIST
OF A UTII ORITIES.
No. OF
Author from
No. OF
Author from
Figure.
WHOM TAKEN.
Figure.
WHOM TAKEN.
58
Brown.
72
Gegenbaur.
59
Vienna Atlas.
73
Brown.
60
Owen.
74
Cuvier.
61
Vienna Atlas.
75
it
62
Brown.
76
it
63
it
77
a
64
it
78
ti
65
Marsh.
79
Brown.
66
1 C
80
a
67
Vienna Atlas.
81
Owen.
6S
it it
82
Brown.
69
Huxley.
83
a
70
it
84
a
7i
it
85
a
86
tt
BOTANY.
87
Micrographic Dictionary.
hi
M i crograph ic Di ctionary
88
tt
it
1 12
a 11
89
it
it
”3
a a
90
a
ti
114
a tt
9i
a
it
115
a a
92
((
11
1 16
Hooker.
93
a
a
117
Micrographic Dictionary
94
a
a
11S
Hooker and Taylor.
95
a
a
119
(( ti
96
11
a
120
Berkeley.
97
a
it
121
Balfour.
98
a
a
122
<<
99
Harvey.
123
ft
100
il
124
ll
IOI
H
125
it
102
Micrographic Dictionaiy.
126
il
103
it
a
127
ll
104
(i
tt
12S
it
105
it
tt
129
Berkeley.
106
ll
tt
130
ti
107
Hassal.
131
Dalton.
108
Micrographic Dictionary.
132
Balfour
109
it
tt
133
C«
1 10
it
a
134
tt
LIST OF A UTHORITIES.
185
No. OF
Author from
No. OF
Author from
Figure.
WHOM TAKEN.
Figure.
WHOM TAKEN.
135 . l 35 a
Wood.
140
Balfour.
1 36
Balfour.
141
a
i 37
it
142
a
13S
it
143
a
i 39
tt
GEOLOGY.
144
Dana.
152
Cuvier.
145
ii
153
Owen.
146
ii
154
<<
147
it
155
ii
148
ii
156
ii
149
ii
157
ii
150
Owen.
158
Cuvier.
151
Carpenter.
159
Gegenbaur
EMBRYOLOGY.
160
Haeckel.
171
Kolliker.
161
ii
172
U
162
it
173
it
163
i i
174
Von Baer.
164
({
175
Kolliker.
165
Kolliker (slightly
176
<<
altered).
177
Haeckel.
166
Kolliker.
17S
it
167
<<
179
a
168
((
180
a
169
((
1S1
a
170
(C
ANTHROPOLOGY.
1S2
Huxley.
190
Huxley.
183
it
191
ii
184
it
192
it
185
it
193
ii
1 86
ii
194
Vogt.
187
if
I 9 S
it
188
ii
196
ii
189
ii
1 97
Huxley.
1 86
No. i
Figui
I9S
199
200
201
202
203
204
205
LIST OF AUTHORITIES.
Author from
WHOM TAKEN.
No. of Author from
Figure. whom taken.
Huxley.
it
Plates of Men and ^ u aec k e i
Monkey Faces. J
it
206 Huxley.
Buchner.
a
207 “
208 “
it
209 “
a
210 “
Vogt.
Plate of Diffusion of 1 jj aec j ce j
Races of Men. /
INDEX
Acephala, 46.
Achlamydeous flower, 102.
Acblya, 85.
Achorion, 84.
Acinetse, 31.
Acrogens, 91.
age of, 115.
Actinozoa, 26.
tree of, 25.
Africa, rainy season in, 57.
Agaricus, 85.
Age, golden, 177.
of bronze, 178.
of stone, 177.
Algae, 78.
age of, 1 14.
description of, 79.
Allantois, 61, 13 1.
Alrothallus, 87.
Alternate generation, 29.
Amblystoma mavortium, 1 54.
Amia, 57, 1 15.
Ammonites, 49.
Amnion, 61, 131.
Amoeba, 21.
Amphibia, 59.
Amphioxus, 39.
relation to Ascidia, 53.
structure of, 55.
Anchitherium, 9, 139.
Anemodonts, 62.
Anemone, 26.
description of, 27.
Angiospermai, 98.
Anguidae, 62.
Animal kingdom, table of, 50.
Animals, growth of, 11.
Cenozoic, 109.
Mesozoic, 109.
Palaeozoic, 109.
Annelida, 36.
Anoplotherium, 73, 122, 140.
descent of, 9.
Ant-eater, 76, 137.
Antheridia, 89, 90, 93.
Anthers, 97.
Anthracotherium, 9.
Anthroceros, 89.
Anthropology, 162.
Ants, economy of, 165.
Ape, 70.
the ancestor of Man, 175.
Apetalte, 102.
Apteryx, 66, 142.
Arachnida, 44.
Arcella, 21.
Archegonia, 89, 90, 93.
Archegosaurus, 59.
skull of, 60.
Archeopteryx, 64, 119.
Armadillo, 142.
Articulata, 44.
structure of, 46.
Artiodactyla, structure of, 72.
Artisca, position of the, 38.
Ascidian, development of, 53.
structure of, 39.
Ascomycetes, 87.
Ascus, 84.
Aspidogaster, 36.
Asterophyllites, 116.
Aurelia, 29.
Australia, fauna of, 72.
Aye-aye, peculiarities of, 20.
Azolla, 96.
Bat, 70.
Batrachia, development of, 130.
fossil, 1 16.
two types of, 59.
Beaver, 70.
Beetles, natural selection among, 150.
Belodon, 62.
Beroe, 29.
Birds, agreement with reptiles. 64.
classification of, 63.
t 187 )
1 88
INDEX.
Birds, development of, 131.
fossil forms, 118.
growth of, 61.
voices of, 152.
Botocudos, character of the, 168.
Botryllus, 41.
Botrytis, 85.
Brachiopoda, 112.
affinities of, 48.
fossil forms abundant, 49.
Brain, comparative size of, 165.
development of, 133.
Branchial arches, 13S.
Bread-tree, 97, 98.
Brontozoon, 118.
Bryozoa, 38.
relation to Mollusca, 39.
Buccinum, 49.
Buchner, 16.
Calamites, 116.
Calyx, 96.
Cambium, 100.
Capybara, 75.
Campularia, 28.
Carboniferous period, 115.
Carinaria, 49.
Carinata, 64.
Carnivora, 75.
Carus, 86.
Cassowary, 66.
Cell, 126.
Cenozoic animals, 109.
Centipedes, 44.
Cephalopoda, 48.
structure of, 49.
Cestracion, 115,1 19.
Cetacea, 75.
Chara, 88.
Chenopodium, 97.
Chicken, development of, 127.
Chimera, 56.
Chlorococcus, 79.
Chorda dorsalis, 130.
Ciliata, 31.
Clamatores, 67.
Classification, artificial, 12.
difficulties of, 19.
Climate as a cause of variation, 146.
Closterium, 80.
Clover, fertilized by bees, 143.
Club-Moss, 91, 94.
Coccolepis, 57.
Coccosteus, 58.
Cod, 57.
Coecilia, 59.
Coelacanthes, 57.
Coelenterata, 26.
characters of, 39.
Color, adaptation of, 151.
Comatula, 41, 1 12.
Compsognathus, 65, 119.
Conchifera, 46.
Coniferre, 78, 98, 99.
Conjugation in Algae, 80.
Connecticut sandstone, 118.
Coral reefs, 27.
Corolla, 97.
Coryphodon, to, 73, 140.
Cosmarium, 80.
Cotyledons of Cypress, 100.
Cretaceous period, 1 1 7, 120.
Crinoids, 42, 1 12.
Crocodiles, fossil, 119.
Crustacea, 44.
Cryptogamia, 78.
definition of, 101.
Crystals, growth of, II.
Ctenoplioras, 29.
Cycadae, 78, 98.
Cyclops, 46.
Cydippe, 29.
Cypris, 46, 113.
Cysticercus, 36.
Daphnia, 46.
Darwin, Charles, merits of his work,
17 -
the Newton of Natural History,
76.
Deer, 139.
De Maillet, 14.
Dendroccela, 35.
Desmidiaceae, 79.
Devonian formation, 114.
D’Halloy, D'Omalius, 16.
Diapetalfe, 102.
Dichobune, 74.
Dichodon, 74.
Dicotyledons, 78.
Dicotyledonous plants, 101.
Didelphia, 70.
Dimorphodon, 119.
Dinomis, 66, 11S, 142.
Dinosauria, 62, 119.
structure of, 65.
Dipnoi, 57.
Diprotodon, 72, 73.
Dog, 70.
Dokos, character of the, 16S.
INDEX.
189
Draves, migrations of, 178.
Dromatherium, 11S.
Dugong, 74.
Ear, development of, 159.
Earthquakes, 124.
Echidna, 70.
Echinorhynchus, 35.
Echinus, 42.
organization of, 43.
Edentata, 72, 14S.
Egg, development of, 127.
of Mammal, 126.
Elephant, 70.
approaching Rodentia, 75.
Embryology, growth of, 125.
Embryos, necessity of studying, 32.
of the Vertebrata, 54.
Emeu, 64, 66.
Endogens, 100.
Endosperm, 99.
Eocene period, 121.
Epithelium, 129.
Equisetum, 92.
Euastrum, 80.
Euglena, 21.
Euphorbia, 102.
Exogens, 100.
Eye, development of, 159.
Fauna of Tertiary Age, 122.
Feet, relation of, to hands, 163.
Ferns, 78, 91.
development of, 93.
fossil forms, 116.
Filicales, 91.
Filices, 92.
growth of, 93.
Fishes, age of, 1 1 5.
brain of, 165.
development of, 130.
fossil forms, 114, 120.
membranous, 56.
Flora of Tertiary Age, 122.
Flovidae, 82.
Flower, description of, 96.
development of, 137.
of Cycas, 98.
Flukes, 35.
Forces studied in their effects, 11.
Frog, 59, 61.
Fucoidas, 81.
Fungi, 78, 83.
classification of, 85.
nutriment of, 84.
Galeopithecus, relationship, 19.
Gamopetalae, 102.
Ganoids, 57, 115.
affinities of, 58.
Gar-pike, 56, x 15.
Gasteropoda, 48.
Gegenbaur, 17.
Generation, spontaneous, meaning of,
21.
evidences of, 22.
Geographical distribution, 141.
Geological changes, 54.
Geolog}', study of, 106.
Gephyrea, 36.
Germinal vesicle, 126.
of plant, 97.
Glyptodon, 142.
Gnetaceae, 102.
Goethe, 14.
Golden Age, 177.
Gonidia, 87.
Gordiaceae, 34.
Gordius, 35.
Graptolites, 1 13.
Gregarinae, 30.
Gymnospermae, 98.
Hadrosaurus, 62, 120.
Haeckel, 17.
on struggle for existence, 143,
145-
Halisarca, 23.
Hands, relation of, to feet, 163.
Hedgehog, 70.
Hepaticae, 89
Herbert, Dean, 16.
Herring, 57.
Hipparion, 9, 139.
Hippopotamus, 9, 139.
Hog, 139.
Holoptychii, 57.
Iiolothuria, 43,
Hooker, 17.
Horse, descent of, 74, 139.
origin of, 9.
Horse-tails, 91.
description of, 92.
Huxley, Thos., 17, 120.
Hyalotheca, 80.
Hybrids, breeding of, 1 cy.
Hydra, 28.
Hydrozoa, 28.
tree of, 25.
Hymenomycetes, 83.
Hymenoptera, 45.
INDEX.
190
Hymenoptera, fossil, 119.
I'lyphi. 85. 87.
llyphomycetes, 85.
Ilypoterygire, 90.
Hypsilopodon, 65.
Hyrax, 70, 72.
position of, 75.
Ichthyosaurus, 59, 119.
Jguanodon, 62, 119.
Infusoria, 30.
a transition group, 32.
Inheritance, 145.
Insects, 44.
fossil, 1 16.
sounds made by, 152.
Intelligence, in animals, 166.
in savages, 167.
relation to brain, 165.
Intermaxillary bone, 14.
Iscetes, 95.
Jaw of La Naulette, 173.
Jungermannia, 89.
Jurassic period, 117, 119.
Kallima parapleta, 151.
Kangaroo, 70.
Kant, 10.
Labyrinthodon, 59, 118.
skull of, 60.
Lamarck, opinions held by, 14.
Lamellibranchiata, 48.
Laminte Dorsales, 130.
Lamprey, 56.
La Naulette, jaw of, 173.
Language of savages, 167.
Leech, 36.
Lemur, 70.
opinions regarding, 19.
Lemuria, 1 77.
Lepidodendrons, 116.
Lepidoganoids, 56.
Lepidosiren, double character of, 58.
habits of, 57,
Lichens, 78.
description of, 86.
position of, 87.
Life, intermediate 24.
origin of, 20.
tree of, 24.
Lily stones, 1 12.
Limbs of vertebrata, 54.
Lingula, 48.
Links, absence of, 158.
Lophiodon, 10, 73, 140.
Lucretius, 13.
Lungs, development of, 136.
Lycopodiaceas, 94.
reproduction of, 95.
Lyell, Sir Charles, 16.
Macrocystis, 81.
Mammal, development of, 131.
Mammalia, definition of, 68.
divisions of, 70.
origin of, 72.
Man, 13, 70.
age of, 122, 177.
birth place of, 177.
difference of origin, 179.
erect position of, 171.
migrations of, 178.
position of, 162.
prehistoric, 173.
progenitors of, 169, 1 75.
Marchantia, 89, 93.
Marsilea, 94.
Marsupialia, fossil, 118.
position of, 71.
Megalonyx, 76.
Megalosaurus, 119.
Megatherium, 76, 137, 142.
Membranes, blastodermic, 127.
vitelline, 126.
Membranous Fishes, 56.
Menobranchus, 59.
Mental faculties, development of, 147.
Mesozoic animals, 109.
Microlestes, 118.
Mildews, 83.
Miocene period, 121.
Mollusca, 46.
age of, 1 14.
Monera, 10.
definition of, 21.
v vegetal, S3.
Monocotyledonous plants, xoi.
Monocotyledons, 78.
Monodelphia, 70.
Monotremata, fossil, 11S.
M onstrosities, explanation of, 136.
Morals, growth of, 179.
Morning-glory, 97.
Moso6aurus, 120.
Mosses, 78, 90.
Moulds, 83.
Mucor, 86.
Muller, 17.
INDEX.
I 9 I
Muscular system, development of,
129.
Mushrooms, S3.
Mycelium of Fungi, 84.
Mylodon, 76.
Myriapoda, 44.
development of, 45.
Myxine, 56.
Naudin, 16.
Nauplius, 46.
Nautilus, 49.
Navicellre, change of, 30.
Neanderthal skull, 173.
Nebular hypothesis, 10.
Negritoes, character of the, 16S.
Nematelminthes, 34.
Nemertes, 36.
Neptunists, ill.
Nervous system, development of, 129.
Niagara limestone, 113.
Nitella, 88.
Noctilucse, 30.
Nostoc, 87.
Nostochacete, 80.
Notidanus, 119.
Nototherium, 73.
Oidium, 84.
Oken, 14.
Opossum, 70.
Organic products manufactured, 12.
Omithodelphia, 70.
Ornithorhynchus, peculiarities of, 20.
structure of, 70.
Osseous system, development of, 129.
Ostrich, 64, 66.
Ovary of plant, 97.
Ovule of plant, 97.
Paleontology, teachings of, ill.
Paleosaurus, 62.
Paleotherium, 9, 72, 122, 140.
Paleozoic animals, 109.
Palms, fructification of, 143.
Paludicella, 38.
Pangolin, 76.
Paramcecium, 30.
Peculiarities, inherited, 135.
Pediastrum, 80.
Penelope, 67.
Penguin, 67.
Pentacrinus, 42.
Pepperwort, 94.
Perch, 57.
Peripatus, 36.
Perissodactyla, structure of, 72.
Peronospora, 85.
Petals, 97.
Petromyzon, 56.
Phanerogamia, 78, 96.
definition of, 101.
Phenomena, ultimate causes of, II.
Phractelminthes, 37.
relationship of the, 41.
Physalia, 28.
Physical conditions, 141.
Pig. 9. 70-
Pigeons, selection among, 158.
Tillwort, 94.
Pine, 97, 98.
Pistil, 97.
Placoganoids, 56.
Planaria, 35.
Plants, classification of, 78-
growth of, 11.
natural selection among, 150.
nutriment of, 83.
progression in, 103.
Platyelminthes, 34.
Plesiosaurus, 59, 1 19.
Plica semilunaris, 136.
Pliocene period, 121.
Pliolophus, 140.
Plutonists, in.
Pollen, 97.
Polypterus, 57, 115.
relationship, 58.
Potsdam region, 112.
Powell, Rev. B., 16.
Primaiy age, 1 10.
Primitive groove, 129.
trace, 128, 129.
Prorhynchus, 35.
Prosimiee, classification of, 75.
habitat, 74.
Prolerosaurus, 62, 117.
Proteus, 59, 60.
Prothallus, 92, 93, 95.
Protococcus, 87.
Protonema, 90.
Protophyta, origin of, 83.
Pteroclidac, 67.
Pterodactyles, 119.
Puff-balls, 83.
Quadrumana, classification of, 162.
Rays, 56.
Reproduction of plants, 80.
INDEX.
192
Reproductive organs, development of,
129.
Reptiles, affinities, 63.
classification of, 62
development of, 131.
growth of, 61.
Rhabdoccela, 315.
Rhea, 66.
Rhinoceros, 9, 139.
Rhizocarpse, 94.
Riccia, 89.
Rocks, age of, no.
aqueous, 108.
Azoic, 109.
classification of, 124.
Paleozoic, 109.
Plutonic, 108.
study of, 107.
Rotatoria, 36.
structure of, 38.
Ruminants, 148.
developments of, 139.
stomachs of, 73.
Sagitta, 39.
Salamander, 59, 61.
Salmon, 57.
Salvinia, 96, 98.
Sandstone, New Red, 1 1 7.
Saprolegnia, 85.
Sargassum, 81.
Saurophalli, 67.
Sauropsida, 71.
Savages, intelligence of, 167.
life of, 155, 168.
Schoharie Grit, 109.
Scolecida, 34.
Scotch fir, 144.
Sea-cow, 70.
Sea-cucumbers, 42.
Sea-urchins, 42.
Sea-weed, red, 82.
Sebright, Sir John, 149.
Secondary Age, 109.
Selaginella, 95.
leaves of, 99.
Selection, artificial, 149.
sexual, 153.
Sepals, 97.
Sepidse, 62.
Sertularia, 28.
Sex, difference in, 152.
Sexual selection, 153.
Shad, 57.
Sharks, 56.
Sharks, fossil 115,119.
Sheep, 139.
Sigillarije, 116.
Silurian formation, 113.
Sipunculus, 36.
Siredon, 60, 154.
Siren, 59.
Skeleton, modifications of, 157.
Skin, development of, 129.
Skull, characters of, 170.
Neanderthal, 173.
structure of, 53.
Sloth, 70, 142.
organization of, 137.
peculiarities of, 76.
Smuts, 83.
Snake, relationship of, 62.
Soft Worms, vessels of, 36.
Sounds of Birds and Insects, 152.
Speech, articulate, 171.
growth of, 172.
Spencer, Herbert, 10, nr.
Spener, 62.
SpliEerocarpus, 89.
Spiders, 44.
Spines, production of, 152.
Spirobranchire, 46.
Spirogyra, 80.
Sponge, 23.
Spontaneous generation, meaning of,
21.
Sporangium, 90.
Sporendonema, 86.
Sporocarps, 94.
Stages, transitional, 13.
Stamens, 97.
Star-fish, description of, 40.
origin of, 41.
Stigma, 97.
Stomata, 89.
St. Cuthbert’s beads, 42, 112.
St. Hilaire, 14.
Structures, transitory, 132, 134.
Struggle for existence, 143.
examples of, 144, 145.
Sturgeon, 56, 115.
Style, 97.
Stylospores, 84.
Survival of the fittest, 149.
Tasnia, 35.
Tape-worm, history of, 36.
Tapir, 9, 139.
Tardigrada, 38.
Teeth, 170.
INDEX.
193
Teliosts, 57.
Terebratula, 48.
Tertiary Age, no, 121.
Thallophytes, 88.
Thecodonts, 62.
Thrush, 84.
Thylacinus, 72.
Trematoda, 35.
Trenton Falls, 1 12.
Triassic period, 117.
Trichina, history of, 34.
Trilobites, 109, 113.
Triton, 61.
Truffles, 83.
Tunicata, 39.
Turbellaria, 35.
Turtles, fossil, 119.
Ulvacese, 80.
Umbilical vesicle, 130
Ungulata, 73. >
affinities of, 74.
Urinary system, development of, 129.
Variations, causes of, 148.
entailing others, 148.
production of, 146, 147.
Vascular system, development of, 129.
Vaucheria, 85.
Vegetal kingdom, 78.
Vegetal kingdom, tree of, 105.
Vertebrata, characters of the, 52.
division of, 61.
embryos of similar, 54.
Visceral arches, 138.
Vestiges of Creation, 16.
Vital Force, laws of, 12.
Vitelline membrane, 126.
Vitellus, 126.
Vortex, 35.
Vorticellae, 31.
Wallace, independent enunciation of
doctrine, 17.
on geographical distribution,
142.
Whale, 70.
Wings of insects and birds, 52.
Wolff, 14.
Wombat, 70.
Worms, 32.
articulated, 36, 37.
tree of, 33.
Wright, Seth, 149.
Xiphodon, 74.
Zamia, 98.
Zeuglodon, 75.
Zoophyte, meaning of, 20.
THE END.
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