Methods of study in natural history

B M EM3

METHODS OF STUD!

NATURAL HISTORY.

BY L. AGASSIZ.

BOSTON:
FIELDS, OSGOOD, & CO.,

SUCCESSORS TO TICKNOR AND FIELDS.
I87I.

Ml

Entered according to Act of Congress, in the yew 1863, by

TICKNOR AND FIELDS,
to the Clerk'B Office of the District Court of the District of Masswshi

SEVENTH EDITION.

UNIVERSITY PRESS:

WELCH, BIGELOW, AND COMPANY,

CAMBRIDGE.

PREFACE.

THE series of papers collected in this volume
may be considered as a complement or commen-
tary to my " Essay on Classification," since I
have endeavored to present here in a more pop-
ular form the views first expressed in that work.
And although the direct intention of these pages
has been, as their title indicates, to give some
general hints to young students as to the meth-
ods by which scientific truth has been reached,
including a general sketch of the history of sci-
ence in past times, yet I have also wished to
avail myself of this opportunity to enter my ear-
nest protest against the transmutation theory,
revived of late with so much ability, and so
generally received. It is my belief that natural-
ists are chasing a phantom, in their search after
some material gradation among created beings,
by which the whole Animal Kingdom may have
been derived by successive development from a

v PREFACE.

single germ, or from a few germs It would
seem, from the frequency with which this notion
is revived, — ever returning upon us with hydra-
headed tenacity of life, and presenting itself
under a new form as soon as the preceding one
has been exploded and set aside, — that it has a
certain fascination for the human mind. This
arises, perhaps, from the desire to explain the
secret of our own existence ; to have some sim-
ple and easy solution of the fact that we live.

I confess that there seems to me to be a repul-
sive poverty in this material explanation, that is
contradicted by the intellectual grandeur of the
universe ; the resources of the Deity cannot be so
meagre, that, in order to create a human being
endowed with reason, he must change a monkey
into a man. This is, however, merely a personal
opinion, and has no weight as an argument ; nor
am I so uncandid as to assume that another may
not hold an opinion diametrically opposed to mine
in a spirit quite as reverential as my own. But I
nevertheless insist, that this theory is opposed to
the processes of Nature, as far as we have been
able to apprehend them ; that it is contradicted
by the facts of Embryology and Paleontology,
the former showing us norms of development as

PREFACE. T

distinct and persistent for each group as are
the fossil types of each period revealed to us by
the latter ; and that the experiments upon domes-
ticated animals and cultivated plants, on which
its adherents base their views, are entirely foreign
to the matter in hand, since the varieties thus
brought about by the fostering care of man are
of an entirely different character from those ob-
served among wild species. And while their
positive evidence is inapplicable, their negative
evidence is equally unsatisfactory, since, however
long and frequent the breaks in the geological se-
ries may be in which they would fain bury their
transition types, there are many points in the
succession where the connection is perfectly dis-
tinct and unbroken, and it is just at these points
that new organic groups are introduced without
any intermediate forms to link them with the
preceding ones. In another series of papers, I
shall endeavor to show the futility of the argur
ment so far as it is founded upon the imperfec-
tion of the geological record.

I would add one word upon the way in which
this volume has been prepared, since it has some
features requiring explanation, if not apology.
These chapters were first embodied in a course

VI PREFACE.

of lectures delivered at the Lowell Institute in
Boston, without any thought of their subsequent
publication. Notes were, however, taken of
them at the time, and I very willingly assented
to the suggestion of some of my listeners, that
they should be recorded in the form of articles
for the Atlantic Monthly. They still retain some-
thing of the repetition which is needed in a
public course of scientific lectures in order to
keep the connection of the subjects clearly before
the mind of a popular audience. An attempt
to change this character would have amounted
to writing the whole course anew, — a task for
which I had neither time nor inclination. I have
endeavored to avoid technicalities as far as pos-
sible in dealing with subjects many of which
are quite unfamiliar to the general mind ; and the
closing chapter of the book, which has been in-
corporated in the volume, but did not appear in
the Atlantic Monthly, is the only one especially
addressed to the professional naturalist.

L. AGASSIZ.

NAHAXT, August 22, 1863.

CONTENTS.

CHAPTEB I.

GENERAL SKETCH OF THE EARLY PROGRESS IN NATURAL

HISTORY ........ • . • 1

CHAPTER II.

NOMENCLATURE AND CLASSIFICATION ..... M

CHAPTEB III.

CATEGORIES OF CLASSIFICATION ...... 80

CHAPTEB IV.

CLASSIFICATION AND CREATION ...... 41

CHAPTEB V.

DIFFERENT VIEWS RESPECTING CRDEBft . • • • . 72

CHAPTEB VI.

GRADATION AMONG ANIMALS ...•••• M

CHAPTEB VII.

ANALOGOUS TYPES

CHAPTEB VIII.

FAMILY CHARACTERISTICS ..... . . 109

Vlll CONTENTS.

CHAPTER IX.

TOE CHARACTERS OF GENERA 136

CHAPTER X.

SPECIES Alto BREEDS 184

CHAPTER XI.

FORMATION OF CORAL REEFS , 148

CHAPTER XII.

AGE OF CORAL REEFS AS SHOWING PERMANENCE OF SPECIES 175

CHAPTER XIII.

HOMOLOGIES 201

CHAPTER XIV.

ALTERNATE GENERATIONS ....... 233

CHAPTER XV.

THE OVARIAN EGG 269

CHAPTER XVI.

EMBRYOLOGY AND CLASSIFICATION ...... 296

METHODS OF STUDY IN NATURAL
HISTORY.

CHAPTER I.

GENERAL SKETCH OF THE EARLY PROGRESS IN
NATURAL HISTORY.

IT is my intention, in this series of papers, to
give the history of the progress in Natural His-
tory from the beginning, — to show how men
first approached Nature, — how the facts of Nat-
ural History have been accumulated, and how
these facts have 'been converted into science. In
so doing, I shall present the methods followed
in Natural History on a wider scale and with
broader generalizations than if I limited myself
to the study as it exists to-day. The history of
humanity, in its efforts to understand the Crea-
tion, resembles the development of any individ-
ual mind engaged in the same direction. It
has its infancy, with the first recognition of
surrounding objects ; and, indeed, the early ob-
servers seem to us like children in their first at-
tempts to understand the world in which they

2 EARLY PROGRESS

live. But these efforts, that appear childish to us
now, wore the first steps in that field of knowl-
edge which is so extensive that all our progress
seems only to show us how much is left to do.

Aristotle is the representative of the learning
of antiquity in Natural Science. The great mind
of Greece in his day, and a leader in all the in-
tellectual culture of his time, he was especially a1*
naturalist, and his work on Natural History is
a record not only of his own investigations, but
of all preceding study in this department. It
is evident that even then much had been done,
and, in allusion to certain peculiarities of the
human frame, which he does not describe in full,
he refers his readers to familiar works, saying,
that illustrations in point may be found in ana-
tomical text-books.*

Strange that in Aristotle's day, two thousand
years ago, such books should have been in gen-
eral use, and that in our time we are still in
want of elementary text-books of Natural His-
tory, having special reference to the animals of
our own country, and adapted to the use of
schools. One fact in Aristotle's " History of
Animals " is very striking, and makes it diffi-
cult for us to understand much of its contents.
It never occurs to him that a time may come
when tho Greek language — the language of all

* See Aristotle's Zoology, Book I, Chapter XIV.

IN NATURAL HISTORY. 3

culture and science in his time — would not be
the language of all cultivated men. He took,
therefore, little pains to characterize the animals
he alludes to, otherwise than by their current
names ; and of his descriptions of their habits
and peculiarities, much is lost upon us from
their local character and expression. There is
also a total absence of systematic form, of any
classification or framework to express the divis-
ions of the animal kingdom into larger or lesser
groups. His only divisions are genera and spe-
cies : classes', orders, and families, as we under-
stand them now, are quite foreign to the Greek
conception of the animal kingdom. Fishes and
birds, for instance, they considered as genera,
and their different representatives as species.
They grouped together quadrupeds also, in con-
tradistinction to animals with legs and wings,
and they distinguished those that bring forth
living young from those that lay eggs. But
though a system of Nature was not familiar
even to their great philosopher, and Aristotle
had not arrived at the idea of a classification on
general principles, he yet stimulated a search
into the closer affinities among animals by the
differences he pointed out. He divided the ani-
mal kingdom into two groups, which he called
Enaima and Anaima, or animals with blood and
animals without blood. We must remember,

4 EARLY PROGRESS

however, that by the word blood he designated
only the red fluid circulating in the higher ani-
mals ; whereas a fluid akin to blood exists in all
animals, variously colored in some, but colorless
in a large number of others.

After Aristotle, a long period elapsed without
any addition to the information he left us.
Borne and the Middle Ages gave us nothing, and
even Pliny added hardly a fact to those that
Aristotle recorded. And though the great nat-
uralists of the sixteenth century gave a new
impulse to this study, their investigations were
chiefly directed towards a minute acquaintance
with the animals they had an opportunity of
observing, mingled with commentaries upon the
ancients. Systematic Zoology was but little ad-
vanced by their efforts.

We must come down to the last century, to
Limiaeus, before we find the history taken up
where Aristotle had left it, and some of his sug-
gestions carried out with new freshness and vigor.
Aristotle had already distinguished between gen-
era and species ; Linnaeus took hold of this idea,
and gave special names to other groups, of dif-
ferent weight and value. Besides species and
genera, he gives us orders and classes, — con-
sidering classes the most comprehensive, then
orders, then genera, then species. He did not,
however, represent these groups as distinguished

IN NATURAL HISTORY 5

by their nature, but only by their range ; they
were still to him, as genera and species had been
to Aristotle, only larger or smaller groups, not
founded upon and limited by different categories
of structure. He divided the animal kingdom
into six classes, which I give here, as we shall
have occasion to compare them with other clas-
sifications : — Mammalia, Birds, Reptiles, Fishes,
Insects, and Worms.

That this classification should have expressed
all that was known, in the last century, of the
most general relations among animals, only shows
how difficult it is to generalize on such a sub-
ject ; nor should we expect to find it an easy task,
when we remember the vast number of species
(about a quarter of a million) already noticed
by naturalists. Linnaeus succeeded, however, in
finding a common character on which to unite
most of his classes ; but his definition of the
class of Mammalia, that group to which we our-
selves belong, remained very imperfect. Indeed,
in the earlier editions of his classification, he
does not apply the name of Mammalia to this
class, but calls the higher animals Quadrupedia,
characterizing them as the animals with four legs
and covered with fur or hair, that bring forth
living young and nurse them with milk. In
thus admitting external features as class char-
acters, he excluded many animals which by their

6 EARLY PROGRESS

mode of reproduction, as well as by their res-
piration and circulation, belong to this class as
much as the Quadrupeds, — as, for instance, all
the Cetaceans (Whales, Porpoises, and the like),
which, though they have not legs, nor are their
bodies covered with hair or fur, yet bring forth
living young, nurse them with milk, are warm-
blooded and air-breathing. As more was learned
of these animals, there arose serious discussion
and criticism among contemporary naturalists
respecting the classification of Linnaeus, all of
which led to a clearer insight into the true re-
lations among animals. Linna3us himself, in his
last edition of the " Systema Nature," shows us
what important progress he had made since he
first announced his views ; for he there substi-
tutes for the name of Quadrupedia that of Mam-
malia, including among them the Whales, which
he characterizes as air-breathing, warm-blooded,
and bringing forth living young which they nurse
with milk. Thus the very deficiencies of his
classification stimulated naturalists to new criti-
cism and investigation into the true limits of
classes, and led to the recognition of one. most
important principle, — that such groups are
founded, not on external appearance, but on
internal structure, and that internal structure,
therefore, is the thing to be studied. The group
of Quadrupeds was not the only defective one

IN NATURAL HISTORY. 7

in this classification of Linnaeus; his class of
"Worms, also, was most heterogeneous, for he
included among them Shell-Fishes, Slugs, Star-
Fishes, Sea-Urchins, Corals, and other animals
that bear no relation whatever to the class of
Worms as now defined.

But whatever its defects, the classification of
Linnaeus was the first attempt at grouping ani-
mals together according to certain common struc-
tural characters. His followers and pupils en-
gaged at once in a scrutiny of the differences
and similarities among animals, which soon led
to a great increase in the number of classes ; in-
stead of six, there were presently nine, twelve,
and more. But till Cuvier's time there was no
great principle of classification. Facts .were ac-
cumulated and more or less systematized, but
they were not yet arranged according to law ;
the principle was still wanting by which to gen-
eralize them and give meaning and vitality to the
whole. It was Cuvier who found the key. He
himself tells us how he first began, in his investi-
gations upon the internal organization of animals,
to use his dissections with reference to finding the
true relations between animals, and how ever
after his knowledge of anatomy assisted him in
his classifications, while his classifications threw
new light again on his anatomical investigations,
— each science thus helping to fertilize the other.

8 EARLY PROGRESS

He was not one of those superficial observers
who are in haste to announce every new fact that
they chance to find, and his first paper * special-
ly devoted to classification gave to the world the
ripe fruit of years of study. This was followed
by his great work, "Le Regne Animal." He
said that animals were united in their most
comprehensive groups, not on special characters,
but on different plans of structure , — moulds, he
called them, in which all animals had been cast.
He tells us this in such admirable language, that
I must, to do justice to his thought, give it in his
own words:— T-

" Si Ton considere le rSgne animal d'apr£s les
principes que nous venons de poser en se d£bar-
rassant des pre'juge's e*tablis sur les divisions an-
ciennement admises, en n'ayant e*gard qu'a 1'or-
ganisation et a la nature des animaux, et non
pas & leur grandeur, a leur utilite*, an plus ou
moins de connaissance que nous en avons, ni a
toutes les autres circonstances accessoires, on
trouvera qu'il existe quatre formes principales,
quatre plans ge'ne'raux, si Ton peut s'exprimer
ainsi, d'apres lesquels tous les animaux semblent
avoir e*td modeles, et dont les divisions ulteVieures,
de quelque titre que les naturalistes les aient de*-
cordes, ne sont que des modifications assez l£g£rer

* " Sur un nouveau rapprochement a e'tablir entre les Cuv2«*
qui composent le Regne Animal." — Arm. Mus., Vol. XIX,

IN NATURAL HISTORY.

fondles sur le deVeloppement ou 1'addition de
quelques parties, qui ne changent rien a Pessence
du plan."*

The value of this principle was soon tested by
its application to facts already known, and it was
found that animals whose affinities had been
questionable before were now at once referred
to their true relations with other animals by as-
certaining whether they were built on one or
another of these plans. Of such plans or struc-
tural conceptions Cuvier found in the whole ani-
mal kingdom only four, which he called Verte-
brates, Mollusks, Articulates, and Radiates.

With this new principle as the basis of investi-
gation, it was no longer enough for the naturalist
to know a certain amount of features character-
istic of a certain number of animals, — he must
penetrate deep enough into their organization to

* If we consider the animal kingdom according to the princi-
ples advanced above, — freeing ourselves at the same time from
prejudices founded on previously established divisions, and look-
ing at animals only with reference to their nature and or-
ganization, excluding their size, their utility, our greater or less
familiarity with them, and all other accessory circumstances, —
we shall find that there exist four principal forms, four general
plans, if we may so express it, in accordance with which all
animals seem to have been modelled, and the ulterior divisions
of which, by whatever title naturalists may have dignified them,
are only comparatively light modifications, founded on the de-
velopment or the addition of some parts not affecting the
tial elements of the plan.
1*

10 EARLY PROGRESS

find the secret of their internal structure. Till
he can do this, he is like the traveller in a strange
city, who looks on the exterior of edifices entirely
new to him, but knows nothing of the plan of
their internal architecture. To be able to read
in the finished structure the plan on which the
whole is built is now essential to every naturalist.
Each of these plans may be stated in the most
general terms. In the Vertebrates there is a
vertebral column terminating in a prominent
head ; this column has an arch above and an
arch below, forming a double internal cavity."
The parts are symmetrically arranged on either
side of the longitudinal axis of the body. In the
Mollusks, also, the parts are arranged according
to a bilateral symmetry on either side of the body,
but the body has but one cavity, and is a soft,
concentrated mass, without a distinct individual-
ization of parts. In the Articulates there is but
one cavity, and the parts are here again arranged
on either side of the longitudinal axis, but in
these animals the whole body is divided fiom end
to end into transverse rings or joints movable
upon each other. In the Radiates we lose sight
of the bilateral symmetry so prevalent in the
other three, except as a very subordinate element
of structure ; the plan of this lowest type is an
organic sphere, in which all parts bear definite
relations to a vertical axis.

IN NATURAL HISTORY. 11

It is not upon any special features, then, that
these largest divisions of the animal kingdom are
based, but simply upon the general structural
idea. Striking as this statement was, it was cold-
ly received at first by contemporary naturalists :
they could hardly grasp Cuvier's wide generaliza-
tions, and perhaps there was also some jealousy
of the grandeur of his views. Whatever the
cause, his principle of classification was not fully
appreciated ; but it opened a new road for study,
and gave us the key-note to the natural affinities
among animals. Lamarck, his contemporary,
not recognizing the truth of this principle, dis-
tributed the animal kingdom into two great di-
visions, which he calls Vertebrates and Inverte-
brates. Ehrenberg also, at a later period, an-
nounced another division under two heads, —
those with a continuous solid nervous centre,
and those with merely scattered nervous swell-
ings.* But there was no real progress in either of
these latter classifications, so far as the primary
divisions are concerned ; for they correspond to
the old division of Aristotle, under the head of
animals with or without blood, the Enaima and
Anaima.

This coincidence between systems based on

* For more details upon the systems of Zoology, see Agassiz's
Essay on Classification in his "Contributions to tho Natural
History of the United States," Vol. I. ; also printed separately.

12 EARLY PROGRESS

different foundations may teach us that every
structural combination includes certain inherent
necessities which will bring animals together on
whatever set of features we try to classify them ;
so that the division of Aristotle, founded on the
circulating fluids, or that of Lamarck, founded on
the absence or presence of a backbone, or that of
Ehrenberg, founded on the differences of the ner-
vous system, covers the same ground. Lamarck
attempted also to make the faculties of animals a
basis for division among them. But our knowl-
edge of the psychology of animals is still too
imperfect to justify any such use of it. His
divisions into Apathetic, Sensitive, and Intelligent
animals are entirely theoretical. He places, for
instance, Fishes and Reptiles among the Intelli-
gent animals, as distinguished from Crustacea
and Insects, which he refers to the second division.
But one would be puzzled to say how the former
manifest more intelligence than the latter, or why
the latter should be placed among the Sensitive
animals. Again, some of the animals that he
calls Apathetic have been proved by later investi-
gators to show an affection 'and care for their
young, seemingly quite inconsistent with the epi-
thet he has applied to them. In fact, we know
so little of the faculties of animals that any classi-
fication based upon our present information about
them must be very imperfect.

IN NATURAL HISTORY. 13

Many modifications of Cuvier's great divisions
have been attempted ; but though some improve-
ments have been made in the details of his
classification, all departures from its great funda-
mental principle are errors, and do but lead us
away from the recognition of the true affini-
ties among animals. Some naturalists, for in-
stance, have divided off a part of the Radiates
and Articulates, insisting upon some special fea-
tures of structure, and mistaking these for the
more important and general characteristics of
their respective plans. Subsequent investiga-
tions have shown these would-be improvements
to be retrograde movements, only proving more
clearly that Cuvier detected in his four plans
all the great structural ideas on which the vast
variety of animals is founded. This result is
of greater importance than may at first appear.
Upon it depends the question, whether all such
classifications represent merely individual im-
pressions and opinions of men, or whether there
is really something in Nature that presses upon
us certain divisions among animals, certain affin-
ities, certain limitations, founded upon essen-
tial principles of organization. Are our systems
the inventions of naturalists, or only their read-
ing of the Book of Nature ? and can that book
have more than one reading ? If these clas-
sifications are not mere inventions, if they are

14 EAELY PROGRESS IN NATURAL HISTORY.

not an attempt to classify for our own con-
venience the objects we study, then they are
thoughts which, whether we detect them or not,
are expressed in Nature, — then Nature is the
work of thought, the production of intelligence,
carried out according to plan, therefore premedi-
tated, — and in our study of natural objects wo
are approaching the thoughts of the Creator,
reading his conceptions, interpreting a system
that is his and not ours.

All the divergence from the simplicity and
grandeur of the division of the animal kingdom
first recognized by Cuvier arises from an ina-
bility to distinguish between the essential fea-
tures of a plan and its various modes of execu-
tion. We allow the details to shut out the plan
itself, which exists quite independent of special
forms. I hope we shall find a meaning in all
these plans that will prove them to be the parts
of one great conception and the work of one
Mind.

NOMENCLATURE AND CLASSIFICATION. 15

CHAPTER II.

NOMENCLATURE AND CLASSIFICATION.

PROCEEDING upon the view that there is a close
analogy between the way in which every individ-
ual student penetrates into Nature and the pro-
gress of science as a whole in the history of hu-
manity, I continue my sketch of the successive
steps that have led to our present state of knowl-
edge. I began with Aristotle, and showed that
this great philosopher, though he prepared a
digest of all the knowledge belonging to his
time, yet did not feel the necessity of any sys-
tem or of any scientific language differing from
the common mode of expression of his day. He
presents his information as a man "with his eyes
Open narrates in a familiar style what he sees.
As civilization spread and science had its repre-
sentatives in other countries besides Qreece, it
became indispensable to have a common scien-
tific language, a technical nomenclature, combin-
ing many objects under common names, and
enabling every naturalist to express the results
of his observations readily and simply in a man-

10 NOMENCLATIVE

ner intelligible to all other students of Natural
History.

Linnaeus devised such a system, and to him
we owe a most simple and comprehensive scien-
tific mode of designating animals and plants.
It may at first seem no advantage to give up the
common names of the vernacular and adopt the
unfamiliar ones, but a word of explanation will
make the object clear. Perceiving, for instance,
the close relations between certain members of
the larger groups, Linnaeus gave to them names
that should be common to all, and which are
called generic names, — as we speak of Ducks,
when we would designate in one word the Mal-
lard, the Widgeon, the Canvas-Back, etc. ; but to
these generic names he added qualifying epithets,
called specific names, to indicate the different
kinds in each group. For example, the Lion,
the Tiger, the Panther, the Domestic Cat consti-
tute such a natural group, which Linnaeus called
Felis, Cat, indicating the whole genus ; but the
species he designates as Fells catus, the Domestic
Cat, — Fells leo, the Lion, — Felis tigris, the
Tiger. — Felis panthera, the Panther. So he
called all the Dogs Canis ; but for the different
kinds we have Canis familiaris, the Domestic
Dog, — Canis lupus, the Wolf, — Canis vulpes,
the Fox, etc.

In some families of the vegetable kingdom we

AND CLASSIFICATION. 17

can appreciate better the application of this no-
menclature, because we have something corre-
sponding to it in the vernacular. We have, for
instance, one name for all the Oaks, but we call
the different kinds Swamp Oak, Red Oak, White
Oak, Chestnut Oak, etc. So Linnaeus, in his
botanical nomenclature, called all the Oaks by
the generic name Quercus, (characterizing them
by their fruit, the acorn, common to all,) and
qualified them as Quercus bicolor, Quercus
rubra, Quercus alba, Quercus castanea, etc.,
etc. His nomenclature, being so easy of ap-
plication, "became at once exceedingly popular,
and made him the great scientific legislator of
his. century. He insisted on Latin names, be-
"cause, if every naturalist should use his own
language, it must lead to great confusion, and
this Latin nomenclature of double significance
was adopted by all. Another advantage of this
binominal Latin nomenclature consists in pre-
venting the confusion frequently arising from
the use of the same name to designate different
animals in different parts of the world, — as, for
instance, the name of Robin, used in America to
designate a bird of the Thrush family, which is en-
tirely different from the Robin of the Old World,
one of the warblers, — or of different names for
the same animal, as Perch or Chogset or Burgall
for our Gunner. Nothing is more to be depre

18 NOMENCLATURE

cated than an over-appreciation of technicalities,
valuing the name more highly than the thing;
but some knowledge of this scientific nomencla-
ture is necessary to every student of Nature.

While Linnaeus pointed out classes, orders,
genera, and species, other naturalists had de-
tected other divisions among animals, called fam-
ilies. Lamarck, who had been a distinguished
botanist before he began his study of the an-
imal kingdom, brought to his zoological re-
searches his previous methods of investigation.
Families in the vegetable kingdom had long
been distinguished by French botanists ; and
one cannot examine the groups they call by
this name, without perceiving, that, though they
bring them together and describe them accord-
ing to other characters, they have been un-
consciously led to unite them from the general
similarity of their port and bearing. Take, for
instance, the families of Pines, Oaks, Beeches,
Maples, etc., and you feel at once, that, besides
the common characters given in the technical
descriptions of these different groups of trees,
there is also a general resemblance among them
that would naturally lead us to associate them
together, even if we knew nothing of the special
features of their structure. By an instinctive
recognition of this family likeness between
plants, botanists have been led to seek for

AND CLASSIFICATION. 19

structural characters on which to unite them,
and the groups so founded generally correspond
with the combinations suggested by their ap-
pearance.

By a like process Lamarck combined animals
into families. His method was adopted by
French naturalists generally, and found favor
especially with Cuvier, who was particularly
successful in limiting families among animals,
and in naming them happily, generally selecting
names expressive of the features on which the
groups were founded, or borrowing them from
familiar animals. Much, indeed, depends upon
the pleasant sound and the significance of a
name ; for an idea reaches the mind more easily
when well expressed, and Cuvier's names were
both simple and significant. His descriptions
are also remarkable for their graphic precision,
— giving all that is essential, omitting all that
is merely accessory. He has given us the key-
note to his progress in his own expressive lan-
guage : —

" Je dus done, et cette obligation me prit un
temps considerable, je dus faire marcher de front
1'anatomie et la zoologie, les dissections et le
classement ; chercher dans mes premieres re-
marques sur 1'organisation des distributions
meilleures ; m'en servir pour arriver a des re-
vnarques nouvelles ; employer encore ces re-

20 NOMENCLATURE

marques & perfectionner les distributions ; faire
sortir enfin de cette fdcondation mutuclle des
deux sciences, 1'une par Fautre, un syst£nie
zoologique propre a servir d'introducteur et de
guide dans le champ de Fanatomie, et un corps
de doctrine anatoinique propre a servir de d6-
veloppement et d'explication au systdme zoolo-
gique." *

It is deeply to be lamented that so many nat-
uralists have entirely overlooked this significant
advice of Cuvier's, with respect to combining
zoological and anatomical studies in order to
arrive at a clearer perception of the true affilii-
ties among animals. To sum it up in one word,
he tells us that the secret of his method is
" comparison," — ever comparing and compar-
ing throughout the enormous range of his
knowledge of the organization of animals, and
founding upon the differences as well as the
similarities those, broad generalizations under

* " I therefore felt myself obliged, and this obligation cost me
no little time, to make my studies in anatomy and zoology, dissec-
tion and classification, keep pace with each other ; to seek in m j
earlier investigations upon organization a better distribution ol
groups ; to employ these again as a means of perfecting my
classification ; to arrive, in short, by this mutual fecundation of
the two sciences at a zoological system which might serve as a
pioneer and guide in the field of anatomy, and an anatomical
method which would aid in the development and explanation ot
the zoological system."

AND CLASSIFICATION. 21

which he has included all animal structures.
And this method, so prolific in his hands, has
also a lesson for us all. In this country tTiere
is a growing interest in the study of Nature ;
but while there exist hundreds of elementary
works illustrating the native animals of Europe,
there are few such books here to satisfy the de-
mand for information respecting the animals of
our land and water. We are thus forced to
turn more and more to our own investigations
and less to authority ; and the true method of
obtaining independent knowledge is this very
method of Cuvier's, — comparison.

Let us make the most common application of
it to natural objects. Suppose we see together
a Dog, a Cat, a Bear, a Horse, a Cow, and a
Deer. The first feature that strikes us as com-
mon to any two of them is the horn in the Cfow
and Deer. But how shall we associate either of
the others with these ? We examine the teeth,
and find those of the Dog, the Cat, and the Bear
sharp and cutting, while those of the Cow, the
Deer, and the Horse have flat surfaces, adapted
to grinding and chewing, rather than cutting
and tearing. We compare these features of
their structure with the habits of these animals,
and find that the first are carnivorous, that they
seize and tear their prey, while the others are
herbivorous or grazing animals, living only on

22 NOMENCLATURE

vegetable substances, which they chew and
grind. We compare further the Horse and
Cow, and find that the Horse has front teeth
both in the upper and lower jaw, while the Cow
has them only in the lower; and going still
further, and comparing the internal with the ex-
ternal features, we find this arrangement of the
teeth in direct relation to the different structure
of the stomach in the two animals, — the Cow
having a stomach with four pouches, adapted to
a mode of digestion by which the food is pre-
pared for the second mastication, while the
Horse has a simple stomach. Comparing the
Cow and the Deer, we find that the digestive
apparatus is the same in both ; but though they
both have horns, in the Cow the horn is hollow,
and remains through life firmly attached to the
bone, while in the Deer it is solid and is shed
every year. With these facts before us, we can-
not hesitate to place the Dog, the Cat, and the
Bear in one division, as carnivorous animals,
and the other three in another division as her-
bivorous animals, — and looking a little further,
we perceive, that, in common with the Cow and
the Deer, the Goat and the Sheep have cloven
feet, and .that they are all ruminants, while the
Horse has a single hoof, does not ruminate, and
must therefore be separated from them, even
though, like them, he is herbivorous.

AND CLASSIFICATION. 23

This is but the simplest illustration, taken
from the most familiar objects, of this compar-
ative method ; but the same process is equally
applicable to the most intricate problems in an-
imal structures, and will give us the clew to all
true affinities between animals. The education
of a naturalist now consists chiefly in learning
how to compare. If he have- any power of
generalization when he has collected his facts,
this habit of mental comparison will lead him
up to principles, and to the great laws of combi-
nation. It must not discourage us, that the pro-
cess is a slow and laborious one, and the results
of one lifetime after all very small. It might
seem invidious, were I to show here how small
is the sum total of the work accomplished even
by the great exceptional men, whose names are
known throughout the civilized world. But I
may at least be permitted to speak disparagingly
of my own efforts, and to sum up in the fewest
words the result of my life's work. I have de-
voted my whole life to the study of Nature, and
yet a single sentence may express all that I have
done. I have shown that there is a correspond-
ence between the succession of Fishes in geologi-
cal times and the different stages of their growth
in the egg, — this is all. It chanced to be a
result that was found to apply to other groups
and has led to other conclusions of a like nature.

2"4 NOMENCLATURE

But, such as it is, it has been reached by this
system of comparison, which, though I speak
of it now in its application to the study of Nat-
ural History, is equally important in every other
branch of knowledge. By the same process the
most mature results of scientific research in
Philology, in Ethnology, and in Physical Sci-
ence are reached. And let me say that the
community should foster the purely intellect-
ual efforts of scientific men as carefully as
they do their elementary schools and their
practical institutions, generally considered so
much more useful and important to the public.
For from what other source shall we derive the
higher results that are gradually woven into the
practical resources of our life, except from, the
researches of those very men who study science,
not for its uses, but for its truth ? It is this that
gives it its noblest interest : it must be for truth's
sake, and not even for the sake of its usefulness
to humanity, that the scientific man studies Na-
ture. The application of science to the useful
arts requires other abilities, other qualities, other
tools than his ; and therefore I say that the man
of science who follows his studies into their
practical application is false to his calling. The
practical man stands ever ready to take up the
work where the scientific man leaves it, and to
adapt it to the material wants and uses of daily
life.

AND CLASSIFICATION. 25

The publication of Cuvier's proposition, that
the animal kingdom is built on four plans, how-
ever imperfectly understood and appreciated at
first, created, nevertheless, an extraordinary ex-
citement throughout the scientific world. All
naturalists proceeded to test it, and some among
them soon recognized in it a great scientific
truth, — while others, who thought more of
making themselves prominent than of advan-
cing science, proposed poor amendments, that
were sure to be rejected on further iiivestiga
tion. Some of these criticisms and additions,
however, were truly improvements, and touched
upon points overlooked by Cuvier. Blainville,
especially, took up the element of form among
animals, — whether divided on two sides, wheth-
er radiated, whether irregular, etc. He, how-
ever, made the mistake of giving very elaborate
names to animals already known under simpler
ones. Why, for instance, call all animals with
parts radiating in every direction Actinomorpha
or Actinozoaria, when they had received the
significant name of Radiates? It seemed to
be a new system, when in fact it was only a new
name. Ehrenberg, likewise, made an important
distinction, when he united the animals accord-
ing to the difference in their nervous systems ;
but he also encumbered the nomenclature un-
necessarily, when he added to the names Anaima

2

26 NOMENCLATURE

and Enaima of Aristotle those of Myeloneura
and Ganglioneura.

But it is not my object to give all the classifica-
tions of different authors here, and I will there-
fore pass over many noted ones, as those of Bur-
meister, Milne-Edwards, Siebold and Stannius,
Owen, Leuckart, Vogt, Van Beneden, and others,
and proceed to give some account of one investi-
gator who did as much for the progress of Zoology
as Cuvier, though he is comparatively little known
among us.

Karl Ernst von Baer proposed a classification
based, like Cuvier's, upon plan ; but he recognized
what Cuvier failed to perceive, — namely, the
importance of distinguishing between type (by
which he means exactly what Cuvier means by
plan) and complication of structure, — in other
words, between plan and the execution of the
plan. He recognized four types, which corre-
spond exactly to Cuvier's four plans, though he
calls them by different names. Let us compare
them.

Cuvier. Baer.

Radiates, . Peripherie,

Mollusks, Massive,

Articulates, Longitudinal,

Vertebrates. Doubly Symmetrical.

Though perhaps less felicitous, the names of Baer
express the same ideas as those of Cuvier. By
the Peripherie type he signified those animals in

AND CLASSIFICATION. 27

which all the parts converge from the periphery
or circumference of the animal to its centre.
Cuvier only reverses this definition in his name
of Radiates, signifying the animals in which all
parts radiate from the centre to the circumfer-
ence. By Massive, Baer indicated those animals
in which the body is undivided, soft and concen-
trated, without a very distinct individualization
of parts, — exactly the animals included by Cu-
vier under his name of Mollusks, or soft-bodied
animals. In his selection of the epithet Longitu-
dinal, Baer was less fortunate ; for all animals
have a longitudinal diameter, and this word was
not, therefore, sufficiently special. Yet his Lon-
gitudinal type answers exactly to Cuvier's Articu-
lates, — animals in which all parts are arranged
in a succession of articulated joints along a lon-
gitudinal axis. Cuvier has expressed this jointed
structure in the name Articulates ; whereas Baer,
in his name of Longitudinal, referred only to the
arrangement of joints in longitudinal succession,
in a continuous string, as it were, one after an-
other, indicating thus the prevalence of length as
the predominant diameter of the body. For the
Doubly Symmetrical type his name is the better
of the two ; since Cuvier's name of Vertebrates
alludes only to the backbone, — while Baer, who
is an embryologist, signifies in his their mode of
growth also. He knew what Cuvier did not

28 NOMENCLATURE

know, when he first proposed his classification,
that in its first formation the germ of the Verte-
brate divides in two folds ; one turning up above
the backbone, to form and enclose all the sensitive
organs, — the spinal marrow, the organs of sense,
all those organs by which life is expressed ; the
other turning down below the backbone, and en-
closing all those organs by which life is main-
tained,— the organs of digestion, of respiration,
of circulation, of reproduction, etc. So there is in
this type not only an equal division of parts on
either side, but also a division above and below,
making thus a double symmetry in the plan, ex-
pressed by Baer in the name he gave it. Baer
was perfectly original in his conception of these
four types, for his paper was published in the very
same year with that of Cuvier. But even in Ger-
many, his native land, his ideas were not fully
appreciated: strange that it should be so, — for,
had his countrymen recognized his genius, they
might have earlier claimed him as the compeer
of the great French naturalist.

Baer also founded the science of Embryology,
under the guidance of his teacher, Db'llinger.
His researches in this direction showed him that
animals were not only built on four plans, but
that they grew according to four modes of devel-
opment. The Vertebrate arises from the egg
differently from the Articulate, — the Articulate

AND CLASSIFICATION. 29

differently from the Mollusk, — the Mollusk dif-
ferently from the Radiate. Cuvier only showed
us the four plans as they exist in the adult ; Baer
went a step further, and showed us the four plans
in the process of formation.

But his greatest scientific achievement is per-
haps the discovery that all animals originate from
eggs, and that all these eggs are at first identical
in substance and structure. The wonderful and
untiring research condensed into this simple
statement, that all animals arise from eggs, and
that all those eggs are identical in the beginning,
may well excite our admiration. This egg con-
sists of an outer envelope, the vitelline membrane,
containing a fluid more or less dense, and various-
ly colored, the yolk ; within this is a second en-
velope, the so-called germinative vesicle, contain-
ing a somewhat different and more transparent
fluid, and in the fluid of this second envelope
float one or more so-called germinative specks.
At this stage of their growth all eggs are micro-
scopically small, yet each one has such tenacity
of its individual principle of life that no egg was
ever known to swerve from the pattern of the
parent animal that gave it birth.

30 CATEGORIES OF CLASSIFICATION.

CHAPTER III.

CATEGORIES OF CLASSIFICATION.

FROM the time that Linnaeus showed us tho
necessity of a scientific system as a framework for
the arrangement of scientific facts in Natural
History, the number of divisions adopted by zo-
ologists and botanists increased steadily. Not
only were families, orders, and classes added to
genera and species, but these were further multi-
plied by subdivisions of the different groups. But
as the number of divisions increased, they lost in
precise meaning, and it became more and more
doubtful how far they were true to Nature.
Moreover, these divisions were not taken in the
same sense by all naturalists: what were called
families by some were called orders by others,
while the orders of some were the classes of oth-
ers, till it began to be doubted whether these
scientific systems had any foundation in Nature,
or signified anything more than that it had
pleased Linnaeus, for instance, to call certain
groups of animals by one name, while Cuvier
had chosen to call them by another.

CATEGORIES OF CLASSIFICATION. 31

These divisions are, first, the most comprehen-
sive groups, the primary divisions, called branches
by some, types by others, and divided by some
naturalists into so-called sub-types, meaning only
a more limited circumscription of the same kind
of group ; next we have classes, and these also
have been divided into sub-classes; then orders
and sub-orders ; families and sub-families or
tribes ; then genera, species, and varieties. With
reference to the question whether these groups
really exist in Nature, or are merely the expres-
sion of individual theories and opinions, it is
worth while to study the works of the early natu-
ralists, in order to trace the natural process by
which scientific classification has been reached ;
for iii this, as in other departments of learning,
practice has always preceded theory. We do the
thing before we understand why we do it : speech
precedes grammar, reason precedes logic ; and so
a division of animals into groups, upon an in-
stinctive perception of their differences, has pre-
ceded all our scientific creeds and doctrines. Let
us, therefore, proceed to examine the meaning
of these names as adopted by naturalists.

When Cuvier proposed his four primary di-
visions of the animal kingdom, he added his
argument for their adoption, — because, he said,
they are constructed on four different plans.
All the progress in our science since his time

32 CATEGORIES OF CLASSIFICATION.

confirms this result ; and I shall attempt to
show that there are really four, and only four,
such structional ideas at the foundation of the
animal kingdom, and that all animals are in-
cluded under one or another of them. But it
does not follow, that, because we have arrived
at a sound principle, we are therefore unerring
in our practice. From ignorance we may mis-
place animals, and include them under the
wrong division. This is a mistake, however,
which a better insight into their organization
rectifies ; and experience constantly proves, that,
whenever the structure of an animal is perfectly
understood, there is no hesitation as to the head
under which it belongs. We may consequently
test the merits of these four primary groups on
the evidence furnished by investigation.

It has already been seen that these plans may
be presented in the most abstract manner with-
out any reference to special animals. Radiation
expresses in one word the idea on which the
lowest of these types is based. In Radiates we
have no prominent bilateral symmetry, such as
exists in all other animals, but an all-sided
symmetry, in which there is no right and left,
no anterior and posterior extremity, no above
and below. It is true that in some of them
there are indications of that bilateral symmetry
which becomes a law in the higher animals ; but

CATEGORIES OF CLASSIFICATION. 33

wherever such a tendency is perceptible in the
Radiates it is subordinate to the typical plan on
which the whole group is founded. They are
spheroidal bodies ; yet, though many of them
remind us of a sphere, they are by no means
to be compared to a mathematical sphere, but
rather to an organic sphere, so loaded with life,
as it were, as to produce an infinite variety of
radiate symmetry. The mathematical sphere
has a centre to which every point of the sur«
face bears identical relations ; such spheres do
not exist in the Animal Kingdom. A sphere
of revolution, in consequence of its rotation up-
on its axis, presents equally flattened poles with
meridians of equal value ; this also is no organic
character. A living sphere has unequal poles
as well as unequal meridians, however much it
may resemble a perfectly spheroidal body, and
the whole organization is arranged, not neces-
sarily around a centre, but always around a
vertical axis, to which the parts bear equal re-
lations.

In Mollusks there is a longitudinal axis and
a bilateral symmetry ; but the longitudinal
axis in these soft concentrated bodies is not,
very prominent, except in the highest class ;
and though the two ends of this axis are dis-
tinct from each other, the difference is not so
marked that we can say at once, for all of
2* c

84 CATEGORIES OF CLASSIFICATION.

them, winch is the anterior and which the pos-
terior extremity. In this type, right and' left
have the preponderance over the other diame-
ters of the body. The sides are the prominent
parts, — they are loaded with the most impor-
tant organs, or with those peculiarities of the
structure that give it character. The Oyster
is a good instance of this, with its double valve,
so swollen on one side, so flat on the other.
There is an unconscious recognition of this in
the arrangement of all collections of Mollusks ;
for, though the collectors do not put up their
specimens with any intention of illustrating this
peculiarity, they instinctively give them the po-
sition best calculated to display their distinctive
characteristics, and to accomplish this they ne-
cessarily place them in such a manner as to
show the sides.

In Articulates there is also a longitudinal axis
of the body and a bilateral symmetry in the
arrangement of parts ; the head and tail are
marked, and the right and left sides are dis-
tinct. But the prominent tendency in this type
is the development of the dorsal and ventral
region ; here above and below prevail over right
and left. It is the back and the lower side that
have the preponderance over any other part of
the structure in Articulates. The body is divided
from end to end by a succession of transverse

CATEGORIES OF CLASSIFICATION. 35

constrictions, forming movable rings ; but the
striking features of the animal are always above
or below, and especially developed on the back.
Any collection of Insects or Crustacea is an
evidence of this ; being always instinctively ar-
ranged in such a manner as to show the pre-
dominant features, they uniformly exhibit the
back of the animal. The profile view of an
Articulate has no significance ; whereas in a
Mollusk, on the contrary, the profile view is
the most illustrative of the structural char-
acter.

In the highest division, the Vertebrates, so
characteristically called by Baer the- Doubly
Symmetrical type, a solid column runs through
the body with an arch above and an arch below,
thus forming a double internal cavity. In this
type, the head is the prominent feature ; it is,
as it were, the loaded end of the longitudinal
axis, so charged with vitality as to form an in-
telligent brain, and rising in man to such pre-
dominance as to command and control the whole
organism. The structure is arranged above and
below this axis, the upper cavity containing, as
we have seen above, all the sensitive organs,
and the lower cavity containing all those by
which life is maintained.

While Cuvier and his followers traced these
four distinct plans, as shown in the adult ani-

36 CATEGORIES OF CLASSIFICATION.

mal, Baer opened to us a new field of investi-
gation in the embryology of the four types,
showing that for each there was a special mode
of growth in the egg. Looking at them from
this point of view, we shall see that these four
types, with their four modes of growth, seem to
fill out completely the plan or outline of the
animal kingdom, and leave no reason to expect
any further development or any other plan of
animal life within these limits. The eggs of all
animals are spheres, such as I have described
them ; but in the Radiate the whole periphery is
transformed into the germ, so that it becomes,
by the Kquefying of the yolk, a hollow sphere.
In the Mollusks, the germ lies above the yolk,
absorbing its whole substance through the under
side, thus forming a massive close body instead
of a hollow one. In the Articulate, the germ
is turned in a position exactly opposite to that
of the Mollusk, and absorbs the yolk upon the
back. In the Vertebrate, the germ divides in
two folds, one turning upward, the other turning
downward, above and below the central backbone.
These four modes of development seem to ex-
haust the possibilities of the primitive sphere,
which is the foundation of all animal life, and
therefore I believe that Cuvier and Baer were
right in saying that the whole animal kingdom
is included under these four structural ideas.

CATEGORIES OF CLASSIFICATION. 37

Leuckart proposed to subdivide the Radiates in-
to two groups : the Ccelenterata, including Polyps
and Acalephs or Jelly-Fishes, — and Echino-
derms, including Star-Fishes, Sea-Urchins, and
Holothurians. His reason for this distinction
is the fact, that in the latter the organs or
cavities of the body have walls of their own,
distinct from the body-wall; whereas in the
former they are formed by internal folds of the
outer wall of the body, as in the Polyps, or are
hollowed out of the substance of the body, as
in Jelly-Fishes. This implies no difference in
the plan, but merely a difference in the execu-
tion of the plan. Both are equally radiate in
their structure ; and when Leuckart separated
them as distinct primary types, he mistook a
difference in the material expression of the
plan for a difference in the plan itself.

So some naturalists have distinguished Worms
from the other Articulates as a separate prime
division. But the structural plan of this type is
a cylinder divided by transverse constrictions or
joints ; and whether those joints are uniformly
arranged from one end of the body to the other,
as in the Worms, or whether the front joints
are soldered together so as to form two regions
of the body, as in Crustacea, or divided so as
to form three regions of the body, as in winged
insects, does not in the least affect the typical

88 CATEGORIES OF CLASSIFICATION.

character of the structure, which remains the
same in all, being, in fact, an articulated cylin-
der with variously combined rings and more or
less complicated tubular appendages.

Branches or types, then, are natural groups
of the animal kingdom, founded on plans of
structure or structural ideas. What now are
classes ? Are they lesser divisions, differing only
in extent, or are they founded on special charac-
ters ? I believe the latter view to be the true
one, and that class characters have a signifi-
cance quite different from that of their mere
range or extent. These divisions are founded
on certain categories of structure ; and were
there but one animal of a class in the world,
if it had those characters on which a class is
founded, it would be as distinct from all other
classes as if its kind were counted by thousands.

Baer approached the idea of the classes when
he discriminated between plan of structure or
type and the degree of perfection in the struc-
ture. But while he understands the distinction
between a plan and its execution, his ideas re-
specting the different features of structure are
not quite so precise. He does not, for instance,
distinguish between the complication of a given
structure and the mode of execution of a plan,
both of which are combined in what he calls
degrees of perfection. And yet,, without this

CATEGORIES OF CLASSIFICATION. 39

\

distinction, the difference between classes and
orders cannot be understood; for classes and
orders rest upon a just appreciation of these two
categories, which are quite distinct from each
other, and have by no means the same signifi-
cance.

Again, quite distinct from both of these is the
character of form, not to be confounded either
with complication of structure, on which orders
are based, or with the execution of the plan, on
which classes rest. An example will show that
form is no guide for the determination of classes
or orders. Take, for instance, a Beche-de-Mer,
a member of the highest class of Radiates, and
compare it with a Worm. They are both long
cylindrical bodies ; but one has parallel divisions
along the length of 'the body, the other has the
body divided by transverse rings. Though in
external form they resemble each other, the one
is a worm-like Kadiate, the other is a worm-like
Articulate, each having the structure of its own
type ; so that they do not even belong to the
same great division of the animal kingdom, much
less to the same class. We have a similar in-
stance in the Whales and Fishes, — the Whales
having been for a long time considered as Fishes,
on account of their form, while their structural
complication shows them to be a low order of the
class of Mammalia, to which we ourselves belong,

40 CATEGORIES OF CLASSIFICATION.

that class being founded upon a particular mode
of execution of the plan characteristic of the Ver-
tebrates, while the order to which the Whales
belong depends upon their complication of struc-
ture, ae compared with other members of the
same class.

We may therefore say that neither form nor
complication of structure distinguishes classes,
but simply the mode of execution of a plan. In
Vertebrates, for instance, how do we distinguish
the class of Mammalia from the other classes of
the type ? By the peculiar development of the
brain, by their breathing through lungs, by their
double circulation, by their bringing forth living
young and nursing them with milk. In this
class the beasts of prey form a distinct order,
superior to the Whales or the herbivorous ani-
mals, on account of the higher complication of
their structure ; and for the same reason we
place the Monkeys above them all. But among
the beasts of prey we distinguish the Bears, as a
family, from the family of Dogs, Wolves, and
Cats, on account of their different form, which
does not imply a difference either in the compli-
cation of their structure or in the mode of execu-
tion of their plan.

t

CLASSIFICATION AND CREATION. 41

CHAPTER IV.

CLASSIFICATION AND CREATION.

So close is the connection between classifica-
tion and the plan of creation, the former being, so
far as it is accurate, the literal interpreter of
the latter, that the efforts of men to detect the
natural affinities among animals, and to express
them in clear, condensed forms, have always been
recognized as the highest creations of scientific
genius. Creations they were not, since the only
valid classification is already recorded in organic
forms, and a classification which is true to nature
cannot be original ; but works of genius some of
them have unquestionably been, embodying the
laborious, life-long investigations of men whose
powerful imaginations vitalized anew the dead
facts they collected. Such are the systems of
classification of Linnasus, of Cuvier, of von Baer.
And while in presenting classification as the
subject of a series of papers in the "Atlantic
Monthly," I am aware that I am drawing largely
upon the patience of its readers, since the tech-
nical nature of the topic renders many details

42 CLASSIFICATION AND CREATION.

necessary which cannot be otherwise than dry to
any but professional naturalists ; yet believing,
as I do, that classification, rightly understood,
means simply the creative plan of God as ex-
pressed in organic forms, I feel the importance
of attempting at least to present it in a popular
guise, divested, as far as possible, of technical-
ities. I would therefore ask the indulgence of
my readers for such scientific terms and details
as cannot well be dispensed with, begging them
to remember that a long and tedious road may
bring us suddenly upon a glorious prospect, and
that a clearer mental atmosphere and a new in-
tellectual sensation may well reward us for a
little weariness in the outset.

Besides, the time has come when scientific
truth must cease to be the property of the few,
when it must be woven into the common life of
the world ; for we have reached the point where
the results of science touch the very problem of
existence, and all men listen for the solving of
that mystery. When it will come, and how,
none can say ; but this much at least is certain,
that all our researches are leading up to that
question, and mankind will never rest till it is
answered. If, then, the results of science are of
such general interest for the human race, if they
are gradually interpreting the purposes of the
Deity in creation, and the relation of man to all

CLASSIFICATION AND CREATION. 43

the past, then it is well that all should share in
its teachings, and that it should not be kept, like
the learning of the Egyptians, for an exclusive
priesthood who may expound the oracle accord-
ing to their own theories, but should make a part
of all our intellectual culture and of our com-
mon educational systems. With this view, I will
endeavor to simplify as far as may be my illus-
trations of the different groups of the Animal
Kingdom, beginning with a more careful analysis
of those structural features on which classes are
founded.

I have said that the Radiates are the lowest
type among animals, embodying, under an infinite
variety of forms, that plan in which all parts bear
definite relations to a vertical central axis. The
three classes of Radiates are distinguished from
each other by three distinct ways of executing
that plan. I dwell upon this point ; for we shall
never arrive at a clear understanding of the dif-
ferent significance and value of the various
divisions of the Animal Kingdom, till we appre-
ciate the distinction between the structural con-
ception and the material means by which it is
expressed. A comparison will, perhaps, better
explain my meaning. There are certain archi-
tectonic types, including edifices of different
materials, with an infinite variety of architec-
tural details and external ornaments; but the

44 CLASSIFICATION AND CREATION.

flat rovf and the colonnade are typical of all
Grecian temples, whether built of marble or
granite or wood, whether Doric or Ionic or
Corinthian, whether simple and massive or light
and ornamented ; and, in like manner, the steep
roof and pointed arch are the typical characters
of all Gothic cathedrals, whatever be the material
or the details. The architectural conception re-
mains the same in all its essential elements, how-
ever the more superficial features vary. Such
relations as these edifices bear to the architec-
tural idea that includes them all, do classes bear
to the primary divisions or branches of the Ani-
mal Kingdom.

The three classes of Radiates, beginning with
the lowest, and naming them in their relative
order, are Polyps or Sea-anemones and corals,
Acalephs or Jelly-Fishes, and Echinoderms or
Star-Fishes, Sea-Urchins and the like. In the
Polyps the plan is executed in. the simplest
manner ; the body consists of a sac, the sides
of which are folded inward, at regular intervals,
from top to bottom, so as to divide it by vertical
radiating partitions, converging from the periph-
ery toward the centre. These folds do not meet
in the centre, but leave an open space, which is
the main cavity of the body. This open space,
however, occupies only the lower part of the
body; for in the upper there is a second sac

CLASSIFICATION AND CREATION.

45

hanging to a certain distance within the first.
This inner sac has an aperture in the bottom,
through which whatever enters it passes into the
main cavity of the body. A central opening in

Vertical section of a contracted Sea-Anemone or Actinia : o, mouth ; *, ten-
tacles ; *, inner sac or stomach ; b, main cavity ; ff, reproductive organs ;
g, radiating partition ; e e e, radiating chambers ; c c, circular openings
in the partitions ; a a, lower floor. The tentacles are drawn in.

the top forms a kind of mouth, around which
are radiating tentacles connecting with the open
chambers formed by the partitions within. Cut-

Sea-Anemone or Actinia, moderately expanded.

ting such an animal across in a transverse sec-
tion, we shall see the radiation of the partitions

46 CLASSIFICATION AND CREATION.

from the centre to the circumference, showing

Transverse section of a Sea- Anemone or Actinia.

still more distinctly the typical structure of the
division to which it belongs.

The second class is that of Jelly-Fishes or
Acalephs ; and here the same plan is carried out

Staurophora seen in profile.

in the form of a hemispherical gelatinous disk,
the digestive cavity being 'hollowed, or, as it

Hippocrene seen in profile.

were, scooped, out of the substance of the body,
which is traversed by tubes thai radiate from

CLASSIFICATION AND CREATION. 47

the centre to the periphery. Cutting it across
transversely, or looking through its transparent
mass, the same radiation of the internal structure
is seen again ; only that in this instance the radi-
ating lines are not produced by vertical partition-
walls, with open spaces between, as in the Polyps,
but by radiating tubes passing through the ge-
latinous mass of the body. At the periphery is a

Melicertum seen from above, with the tentacles spreading : o o, radiating tubes
with ovaries ; m, mouth ; 1 1 1 1, tentacles.

circular tube connecting them all, and the tenta-
cles, which hang down when the animal is in its
natural position, connect at their base with the
radiating tubes, while numerous smaller tentacles
may form a kind of fringe all round the margin.

The third and highest class includes the Star-
Fishes, Sea-Urchins, and Holothurians or Beches-
de-Mer. The radiation is equally distinct in each
of these ; but here again the mode of execu-
tion differs from that of the two other classed.

48

CLASSIFICATION AND CREATION.

The internal cavity and the radiating tubes, in-
stead of being connected with the outer wall of

Common Sea-Urchin, Echinus, seen from above.

the body as in Polyps, or hollowed out of the
substance of the body as in Jelly-Fishes, are here
enclosed within independent walls of their own,

ubhinarachnius, opened by a transverse or horizontal section, and showing
the internal arrangement : o, mouth ; e e e e e, ambulacra, with their rami-
fications cmcmcm ; wwww, interambulacra.

quite distinct from the wall of the body. But
notwithstanding this difference, a transverse sec-

CLASSIFICATION AND CREATION. 49

tion shows in these animals, as distinctly as in all
the rest, the radiating structure typical of the
whole branch. In these three classes we have
no difference of plan, nor even any modification
of the same plan, — for either one of them ex-
presses it as clearly as any other, — but simply
three different ways of executing one and the
same structural idea.

To those already familiar with these animals
some technical details showing the absolute iden-
tity of structural plan in these three classes of
Radiates may not be uninteresting.

Let us therefore return to the Polyps, and look
at the Sea-Anemone in a new aspect. Sup-
pose the inner sac to be turned out; it will
then present the appearance of a bottle-shaped
body, with a row of hollow projections around
the base of the neck ; the neck itself being the
stomach turned outward, so that its inner surface
becomes its outer surface. If we now compare
this with the Jelly-Fish, placing both in the same
attitude, with the mouth either downward or
upward, it becomes apparent that the so-called
arms surrounding the mouth of the Jelly-Fish
correspond exactly to the neck of our bottle-
shaped animal, with the sole difference that it
is split into lobes in the Jelly-Fish, instead of
remaining tubular as in the Polyp. There are,
however, many Jelly-Fishes in which it is strictly
s P

50 CLASSIFICATION AND CREATION.

tubular as in the Polyps. To carry the com-
parison further, widen the partitions between the
chambers of the Polyps, and the chambers are then
reduced to narrow tubes, which completes the ho-
mology. In Echinoderrns the difference consists,
as we have seen, in the fact that the various cav-
ities of the body, instead of being simply scooped
out of its substance, have walls of their own ;
these walled cavities being enclosed as intestines
by the outer wall of the body. I shall return to
this subject again, when I explain the homolo-
gies of Radiates more in detail, but have thought
it well to allude to it here in connection with
this more general sketch of their structure.

I have mentioned only three classes of Radi-
ates. Cuvier had five in his classification ; for
he had placed among them the Intestinal Worms
and the Infusoria or Animalcules. The Intes-
tinal Worms are much better known now than
they were in his day. Their anatomy and em-
bryology have been traced, and it has been shown
that the essential features of these parasites are
the same as those of all Articulates, their whole
body being divided into successive movable joints
or rings. Cuvier was misled by the circular ar-
rangement of certain parts around the mouth,
and by the presence of a wreath of feelers around
the head of some of these Worms, resembling the
tentacles of many Radiates. This is, however,

CLASSIFICATION AND CREATION. 51

no indication of radiate structure, but a super-
ficial feature in no way related to the internal
organization ; and therefore the Intestinal Worms
must be removed from the branch of Radiates,
and referred to that of Articulates.

We must carefully distinguish between affinity
and analogy among animals. The former is
founded on identity of plan ; the latter only upon
external resemblance. This may be produced by
similar features, which, when intimately connected
with the whole internal organization, as in some
groups, may be considered as typical characters,
but when only grafted, as it were, in a superficial
manner on animals of another type, have no re-
lation to the essential elements of structure, and
become at once subordinate and unimportant.
Such is the difference between the tentacles in a
Radiate and the wreath of feelers in a Worm ; —
the external effect may be much the same ; but
in the former every tentacle opens into one of
the chambers, as in a Polyp, or connects with one
of the radiating tubes, as in Acalephs, or with the
locomotive suckers, as in Star-Fishes, and is there-
fore closely linked with the whole internal or-
ganization ; whereas the feelers in the latter are
only external appendages, in no way connected
with the essential structural elements. We have
a striking illustration of this superficial resem-
blance in the wings of Birds and Insects. In

52 CLASSIFICATION AND CREATION.

Birds, wings are a typical feature, corresponding
to the front limbs in all Vertebrates, which are
constructed in the same way, whether they are
arms as in Man, or fore-legs as in Quadrupeds, or
pectoral fins as in Fishes, or wings. as in Birds.
The wing in an Insect, on the contrary, is a
flattened, dried-up gill, having no structural re-
lation whatever to the wing of a Bird. They
are analogous only, because they resemble each
other in form and in function, being in the same
way subservient to flight; but as organs they
are entirely different. The wings of Birds are
homologous to the limbs of other Vertebrates,
notwithstanding their great apparent difference ;
they are only analogous to the wings of Insects,
notwithstanding their great external resemblance.
In adding Infusoria to the Radiates, Cuvier
was false to his own principle of founding all
classification on plan. He was influenced by
their seeming simplicity of structure, and placed
them in the lowest division of the Animal King-
dom on that account. But even this simplicity
was only apparent in many of them. At cer-
tain seasons of the year myriads of these little
Animalcules may be seen in every brook and
road-side pool. They are like transparent little
globules, without any special organization, appar-
ently ; and were it not that they are in constant
rotation, exhibiting thus a motion of their own,

CLASSIFICATION AND CREATION. 53

one would hardly suspect that they were endowed
with life. To the superficial observer they all
look alike, and it is not strange, that, before they
had been more carefully investigated, they should
have been associated together as the lowest divis-
ion of the Animal Kingdom, representing, as it
were, a border-land between animal and vegeta-
ble life. But since the modern improvements in
the microscope, Ehrenberg, the great master in
microscopic investigation, has shown that many
of these little globules have an extraordinary
complication of structure. Subsequent investi-
gations have proved that they include a great
variety of beings : some of them belonging to the
type of Mollusks ; others to the type of Articu-
lates, being in fact little shrimps ; while many
others are the locomotive germs of plants, and so
far from forming a class by themselves, as a dis-
tinct group in the Animal Kingdom, they seem
to comprise not only representatives of all types,
except Vertebrates, but to belong also in part to
the Vegetable Kingdom.

Siebold, Leuckart, and other modern zoolo-
gists, have considered them as a primary type,
and called them Protozoa ; but this is as great a
mistake as the other. The rotatory motion in
them all is produced by an apparatus that exists
not only in all animals, but in plants also, and is
a most important agent in sustaining the fresh-

54 CLASSIFICATION AND CREATION.

ness and vitality of their circulating fluids and
of the surrounding medium in which they live
It consists of soft fringes, called vibratile cilia.
Such fringes cover the whole surface of these
little living beings, and by their unceasing play
they maintain the rotating motion that carries
them along in the water.

The Mollusks, the next great division of the
Animal Kingdom, also include three classes.
With them is introduced that character of bilat-
eral symmetry, or division of parts on either side
of a longitudinal axis, that prevails throughout
the Animal Kingdom, with the- exception of the
Radiates. The lowest class of Mollusks has been
named Acephala, to signify the absence of any
distinct head ; for though their whole organiza-
tion is based upon the principle of bilateral
symmetry, it is nevertheless very difficult to
determine which is the right side and which the
left in these animals, because there is so little
prominence in the two ends of the body that the
anterior and posterior extremities are hardly to
be distinguished. Take the oyster as an exam-
ple. It has, like most Acephala, a shell with two
valves united by a hinge on the back, one of these
valves being thick and swollen, while the other is
nearly flat. If we lift the shell, we find beneath
a soft lining skin covering the whole animal, and
called by naturalists the mantle, from the inner

CLASSIFICATION AND CREATION. 55

surface of which arises a double row of gills,
forming two pendent folds on the sides of the
body. At one end of the body these folds do
not meet, but leave an open space, where is the
aperture we ^all the mouth. This is the only
indication of an anterior extremity ; but it is
enough to establish a difference between the
front and hind ends of the body, and to serve as
a guide in distinguishing the right and left sides.
If now we lift the mantle and gills, we find the
principal organs beneath : the stomach, with a

Common Fresh-water Mussel, Unio, cut transversely : o, foot ; b &, gills ;
c, mantle ; d, shell ; e, heart ; /, main cavity, with intestines.

winding alimentary canal ; the heart and liver ;
the bloodvessels, branching from either side of
the heart to join the gills ; and a fleshy muscle
passing from one valve of the shell to the other,
enabling the animal by its dilation or contraction
to open and close its shell at will. A cut across

56 CLASSIFICATION AND CREATION.

an animal of this class shows very distinctly the
bilateral arrangement of the parts. In such a
section we see the edge of the two shells on either
side ; within these the edge of the mantle ; then
the double rows of gills ; and in the middle the
alimentary canal, the heart, and the bloodvessels
branching right and left. Some of these animals
have eye-specks on the edge of the mantle ; but
this is not a constant feature. This class of
Acephala includes all the Oysters, Clams, Mus-
sels, and the like. When named with reference
to their double shells, they are called Bivalves ;

Common Hen-Clam, Mactra, in motion.

and with them are associated a host of less con-
spicuous animals, known as Ascidians, Brachio-
pods, and Bryozoa.

The second class in this type is that of Gas-
teropoda, so named from the fleshy muscular
expansion on which they move, and which is
therefore called a foot: a very inappropriate
name ; since it has no relation or resemblance to
a foot, though it is used as a locomotive organ.
This class includes all the Snails, Slugs, Cockles,

CLASSIFICATION AND CREATION. 57

Conchs, Periwinkles, Whelks, Limpets, and the
like. Some of them have no solid covering ; but
the greater part are protected by a single shell,
and on this account they are called Univalves,
in contradistinction to the Acephala or Bivalves.
These shells, though always single, differ from
each other by an endless variety of form and
color, — from the flat simple shell of the Limpet

Limpet, Patella, cut transversely : -a, foot ; d, gills ; c, mantle ; d, shell ;
e, heart ; /, main cavity, with intestines.

to the elaborate spiral and brilliant hues of the
Cones and Cowries. Different as is their ex-
ternal covering, however, if we examine the
internal structure of a Gasteropod, we find the
same general arrangement of parts that prevails
in the Acephala, showing that both belong to the
same great division of the Animal Kingdom.
The mantle envelops the animal, and lines its
single shell as it lined the double shell of the
Oyster ; the gills are placed on either side of it ;
the stomach, with the winding alimentary canal,
is in the centre of the body ; the heart and liver
are placed in the same relation to it as in the
Acephala ; and though the so-called foot would
seem to be a new feature, it is but a muscular

3*

58 CLASSIFICATION AND CREATION.

expansion of the ventral side of the body, already
well developed in the Mussels and Clams. There
is an evident superiority in this class over the
preceding one, in the greater prominence of the
anterior extremity, where there are two or more
feelers, with which eyes more or less developed
are connected ; and though there is nothing that
can be properly called a head, yet there can be
no hesitation as to the distinction between the
front and hind ends of the body.

Margarita arctica, of the coast of New England.

The third and highest class of Mollusks has
been called Cephalopoda, in reference again to a
special feature of their structure. They have
long arms or feelers around the head, serving as
organs of locomotion, by which they propel them-
selves through the water with a velocity that is
quite extraordinary, when compared with the
sluggishness of the other Mollusks. In these
animals the head is distinctly marked, — being
separated, by a contraction or depression behind
it, from the rest of the body. The feelers, so
prominent on the anterior extremity of the Gas-
teropoda, are suppressed in Cephalopoda, and
the eyes are consequently brought immediately

CLASSIFICATION AND CREATION. 59

on the side of the head, and are very large in
proportion to the size of the animal. A skin
corresponding to the mantle envelops the body,
and the gills are on either side of it ; — the
stomach with its winding canal, the liver, and
heart occupy the centre of the body, as in the
other two classes. This class includes all the
Cuttle-Fishes, Squids, and Nautili, and has a

a

Common Squid, Loligo, cut transversely : a, foot or siphon ; &, gills ; e, man-
tle ; d, internal shell ; e, heart ; /, main cavity, with intestines.

vast number of fossil representatives. Many of
these animals are destitute of any shell ; and,

Common Squid, Loligo, in a swimming attitude.

with a single exception, when they have a shell,
it is not coiled from right to left or from left
to right, as in the spiral of the Gasteropoda, but
from behind forwards, as in the Nautilus. These
shells are usually divided into a number of
chambers, — the animal, as it grows, building a
wall behind it at regular intervals, and always
occupying the external chamber, retaining,

60 CLASSIFICATION AND CREATION.

however, a connection with his past home by a
siphon that runs through the whole succession
of chambers. The readers of the "Atlantic
Monthly " cannot fail to remember the exquisite
poem suggested to the Autocrat of the Break-
fast-Table by this singular feature in the struc-
ture of the so-called Chambered Shells.

Cuvier divided the Mollusks also into a larger
number of classes than are now admitted. He
placed the Barnacles with them, on account of
their shells ; and it is only since an investigation
of the germs born from these animals has shown
them to be Articulates that their true position is
understood. They give birth to little Shrimps
that afterwards become attached to the rocks
and then assume the shelly covering that has
misled naturalists about them. They ought
therefore to be referred to the class of Crus-
tacea, in which they are now generally included.
Brachiopods formed another of his classes ; but
these differ from the other Bivalves only in
having a network of bloodvessels upon their
mantle, in the place of free gills, and this is
merely a complication of structure, not a differ-
ence in the general mode of execution, for the
posftion and relation of these organs to the rest
of the structure are exactly the same in both.
Pteropods constituted another class in his divis
ion of the type of Mollusks ; but these animals,

CLASSIFICATION AND CREATION. 61

again, form only an order in the class of Gas-
teropoda, as Brachiopods form an order in the
class of Acephala.

In the third division of the Animal Kingdom,
the Articulates, we have again three classes:
Worms, Crustacea, and Insects. The lowest of
these three classes, the Worms, presents the
typical structure of that branch in the most
uniform manner, with little individualization of
parts. The body is a long cylinder divided
through its whole length by movable joints,
while the head is indicated only by a difference
in the front joints. There is here no concentra-
tion of vitality in special parts of the structure,
as in the higher animals, but the nervous force is
scattered through the whole body, — every ring
having, on its lower side, either two nervous
swellings, one on the right, the other on the left
side, connected by nervous threads with those
that precede and those that follow them, or these
swellings are united in the median line. It is to
this equal distribution of nervous force through
the whole system that these animals owe their
extraordinary power of repairing any injured
part, so that, if cut in two, the front part may
even reconstruct a tail for itself, while the hind
part produces a new head, and both continue to
live as distinct animals. This facility of self-
repair, after a separation of the parts, which is

62 CLASSIFICATION AND CREATION.

even a normal mode of multiplication in some of
them, does not indicate, as may at first appear, a
greater intensity of vital energy, but, on the con-
trary, arises from an absence of any one nervous
centre such as exists in all the higher animals,
and is the key to their whole organization. A
serious injury to the brain of a Vertebrate de-
stroys vitality at once, for it holds the very
essence of its life ; whereas in many of the lower
animals any part of the body may be destroyed
without injury to the rest. The digestive cavity
in the Worms runs the whole length of the body ;
and the respiratory organs, wherever they are
specialized, appear as little vesicles or gill-like
appendages either along the back or below the
sides, connected with the locomotive appen-
dages.

This class includes animals of various degrees
of complication of structure, from those with
highly developed organizations to the Worms
that float in fresh water like long hairs and
hardly seem to be animals, and to those still
lower representatives of the class that live in the
cavities of other animals. Yet even creatures
so low in the scale of life as the Gordius, that
long thread-like Worm found often in brooks
and called Horsehair by the common people, are
not devoid of some instincts, however dim, of
feeling and affection. I remember a case in

CLASSIFICATION AND CREATION. 63

point, that excited my own wonder at the time,
and may not be uninteresting to my readers.

I had received from Detroit, through the kind-
ness of Messrs. Higby and Stearns, one of these
singular animals. When I first saw it, it was
coiled up in a close roll at the bottom of a
bottle filled with fresh water, and looked more
like a little tangle of black sewing-silk than any-
thing else. Wishing to unwind it, that I might
examine its entire length, I placed it in a large
china basin filled with water, and proceeded very
gently to disentangle its coils, when I perceived
that the animal had twisted itself around a bun-
dle of its eggs, holding them fast in a close em-
brace. In the process of unwinding, the eggs
dropped away and floated to a little distance.
Having finally stretched it out to its full length,
perhaps half a yard, I sat watching to see if this
singular being that looked like a long black
thread in the water would give any signs of life.
Almost immediately it moved towards the bun-
dle of eggs, and, having reached it, began to sew
itself through and through the little white mass,
passing one end of its body through it, and then
returning to make another stitch, as it were, till
the eggs were at last completely entangled again
in an intricate network of coils.

It seemed to me almost impossible that this
care of offspring could be the result of any in-

64 CLASSIFICATION AND CREATION.

stinct of affection in a creature of so low an
organization, and I again separated it from the
eggs, and placed them at a greater distance,
when the same action was repeated. On trying
the experiment a third time, the bundle of eggs
had become loosened, and a few of them dropped
off singly into the water. The efforts which the
animal then made to recover the missing ones,
winding itself round and round them, but failing
to bring them into the fold with the rest, because
they were too small and evaded all efforts to
secure them when once parted from the first
little compact mass, convinced me that there was
a definite purpose in its attempts, and that even
a being • so low in the scale of animal existence
has some dim consciousness of a relation to its
offspring.

I afterwards unwound the tnass of eggs, which,
when coiled up as I first saw it, made a roll of
white substance about the size of a coffee-bean,
and found that it consisted of a string of eggs,
measuring more than twelve feet in length, the
eggs being held together by some gelatinous
substance that cemented them and prevented
them from falling apart. Cutting this string
across, and placing a small section under the
microscope, I counted on one surface of such a
cut from seventy to seventy-five eggs ; and, esti-
mating the entire number of eggs according to

CLASSIFICATION AND CREATION. 65

the number contained on such a surface, I found
that there were not less than eight millions of
eggs in the whole string. The fertility of these
lower animals is truly amazing, and is no doubt
a provision of Nature against the many chances
of destruction to which these germs, so delicate
and often microscopically small, must be exposed.
The higher we rise in the Animal Kingdom, the
more limited do we find the number of progeny,
and the care bestowed upon them by the parents
is in proportion to this diminution.

The subsequent adventures of these germs
form so odd a sequel to their early history, that
I will add it here. The eggs are hatched in the
water, the embryos first making their appearance
as little transparent bodies, moving about by
means of verbratile cilia. Their only appen-
dages are minute horns attached to one end of
the body. Strange to say, their next step in life
is to creep into the legs of grasshoppers and bur-
row their way into the abdominal cavity of these
animals, where they undergo their further develop-
ment as Worms, sometimes growing to be two or
three inches in length before they are freed.
When they have grown so large that the grass-
hopper becomes distended by the size of its
strange inhabitant, it bursts, the Worm is re-
leased, and returns to its aquatic life. When
familiar with the vicissitudes in the life of these

66 CLASSIFICATION AND CREATION.

animals, one ceases to wonder that Nature should
make large provision against the many chances
of destruction that beset them, and one may
readily believe, that, of the eight millions of eggs
born from one individual, a comparatively small
number survive.

The next class in the type of Articulates is
that of Crustacea, including Lobsters, Crabs, and
Shrimps. It may seem at first that nothing can
be more unlike a Worm than a Lobster ; but
a comparison of the class-characters shows that
the same general plan controls the organization
in both. The body /of the Lobster is divided into
a succession of joints or rings, like that of the
Worm ; and the fact that the front rings in the
Lobster are soldered together, so as to make a
stiff front region of the body, enclosing the head
and chest, while only the hind rings remain
movable, thus forming a flexible tail, does not
alter in the least the general structure, which
consists in both of a body built of articulated
rings. The nervous swellings, which were even-
ly distributed through the whole body in the
Worm, are more concentrated here, in accord-
ance with the prevalent combination of the rings
in two distinct regions of the body, the larger
ones corresponding to the more important or-
gans ; but their relation to the rest of the organ-
ization, and their connection by nervous threads

CLASSIFICATION AND CREATION. 67

with each other, remain the same. The respi-
ratory organs, which in most of the Worms were
mere vesicles on the lower part of the sides of
the body, are here more highly organized gills ;
but their general character and relation to other
parts of the structure are unchanged, and there
is a connection between the gills and the legs
in Crustacea, corresponding to that between the
respiratory organs in Worms and their locomo-
tive appendages. The alimentary canal consists
of a single digestive cavity passing through the
whole body, as in Worms, the anterior part of
which is surrounded by a large liver. What is
true of the Lobsters is true also, so far as class-
characters are concerned, of all the Crustacea.

Highest in this type are the Insects, and among
these I include Spiders and Centipedes as well as
Winged Insects. It is true that the Centipedes
have a long uniform body like Worms, and the
Spiders have the body divided into two regions
like the Crustacea, while the body in true Insects
has three distinct regions, head, chest, and hind-
body ; but, notwithstanding this apparent differ-
ence, both the former share in the peculiar
class-character that places them with the Winged
Insects in one class, distinct from all the other Ar-
ticulates. We have seen that in the Worms the
respiratory organs are mere vesicles, while in the.
Crustacea they are more highly organized gills ;

68 CLASSIFICATION AND CREATION.

but iii Centipedes, Spiders, and Winged Insects
the breathing-apparatus is aerial, consisting of
air-holes on the sides of the body, connected
with a system of tubes and vessels extending into
the body and admitting air to all parts of it.
In the winged Insects this system is very elabo-
rate, filling the body with air to such a degree as
to render it exceedingly light and adapted to easy
and rapid flight. The general arrangement of
parts is the same in this class as in the two oth-
ers, the typical character being alike in all.

We come now to the highest branch of the An-
imal Kingdom, that to which we ourselves be-
long,— the Vertebrates. This type is usually di-
vided into four classes, Fishes, Reptiles, Birds,
and Mammalia ; and though many naturalists be-
lieve that it includes more, and I am myself of
that opinion, I shall allude here only to the four
generally admitted classes, as they are sufficient
for my present purpose, and will serve to show
the characters upon which classes are based.
In a former paper I have explained in general
terms the plan of structure of this type, — a
backbone, with a solid arch above and a solid
arch below, forming two cavities that contain all
the systems of organs, the. whole being surround-
ed by the flesh and skin. Now whether a body
£O constructed lie prone in the water, like a
Fish, — or be lifted on imperfect legs, like a

CLASSIFICATION AND CREATION. o9

Reptile, — or be balanced on two legs, while the
front Hints become wings, as in Birds, — or be
raised upon four strong limbs terminating in paws
or feet, as in Quadrupeds, — or stand upright
with head erect, while the limbs consist of a pair
of arms and a pair of legs, as in Man, — does not
in the least affect that structural conception un-
der which they are all included. Every Verte-
brate has a backbone ; every Vertebrate has a
solid arch above that backbone and a solid arch
below it, forming two cavities, — no matter
whether these arches be of hard bone, or of carti-
lage, or even of a softer substance ; every Verte-
brate has the brain, the spinal marrow or spinal
cord, and the organs of the senses, in the upper
cavity, and the organs of digestion, respiration,
circulation, and reproduction, in the lower one ;
every Vertebrate has four locomotive appendages
built of the same bones and bearing the same re-
lation to the rest of the organization, whether
they be called pectoral and ventral fins, or legs,
or wings and legs, or arms and legs. Notwith-
standing the rudimentary condition of these limbs
in some Vertebrates and their difference of ex-
ternal appearance in the different groups, they
are all built of the same structural elements.
And even where they seem wanting, as in Ser-
pents, a minute study of the gradual reduction
of the locomotive appendages in various groups

70 CLASSIFICATION AND CREATION

of Reptiles will show that they too are true to
this structural plan. These are the typical char-
acters of the whole branch, and exist in all its
representatives.

What now are the different modes of express-
ing this structural plan that lead us to associate
certain Vertebrates together in distinct classes ?
Beginning with the lowest class, — the Fishes arc
cold-blooded, they breathe through gills, and they
are egg-laying ; in other words, though they havo
the same general structure as the other Verte-
brates, they have a special mode of circulation,
respiration, and reproduction. The Reptiles are
also cold-blooded, though their system of circula-
tion is somewhat more complicated than that of
the Fishes ; they breathe through lungs, though
part of them retain their gills through life ; and
they lay eggs, but larger and fewer ones than the
Fishes, diminishing in number in proportion to
their own higher or lower position in their class.
They also bestow greater care upon their offspring
than most of the Fishes. The Birds are warm-
blooded and air-breathing, having a double cir-
culation ; they are egg-laying, like the two other
classes, but their eggs are comparatively few in
number, and the young are hatched by the moth-
er and fed by the parent birds till they can pro-
vide for themselves.

The Mammalia are also warm-blooded and

CLASSIFICATION AND CREATIOX. 71

breathe through lungs ; but they differ from all
other Vertebrates in their mode of reproduction,
bringing forth living young, which they nurse
with milk. Even in the lowest members of this
highest group of the Vertebrates, at the head
of which stands Man himself, looking heaven-
ward it is true, but nevertheless rooted deeply in
the Animal Kingdom, we have the dawning of
those family relations, those intimate ties between
parents and children, on which the whole social
organization of the human race is based. Man
is the crowning work of God on earth ; but
though so nobly endowed, we must not forget
that we are the lofty children of a race whose
lowest forms lie prostrate within the water, hav
ing no higher aspiration than the desire for food ,
and we cannot understand the possible degrada-
tion and moral wretchedness of Man, without
knowing that his physical nature is rooted in all
the material characteristics that belong to his
type and link him even with the Fish. The
moral and intellectual gifts that distinguish him
from them are his to use or to abuse ; he may, if
he will, abjure his better nature and be Verte-
brate more than Man. He may sink as low as the
lowest of his type, or he may rise to a spiritual
height that will make that which distinguishes
him from the rest far more the controlling ele-
ment of his being than that which unites him
with them.

72 MEANING OF ORDERS.

CHAPTER V.

DIFFERENT VIEWS RESPECTING ORDERS.

IT is in the search after the true boundaries
and characteristics of orders that we may expect
the greatest advance by the naturalists of the
present day ; and yet there is now much discre-
pancy among them, some mistaking orders for
classes, others raising families to the dignity of
orders. This want of agreement in their results
is not strange, however ; for the recognition of
orders is indeed exceedingly difficult. If they
are, as I have denned them, groups in Nature
founded upon a greater or less complication- of
structure, they must, of course, form a regular
gradation within the limits of their class, since
comparative perfection implies comparative rank,
and a correct estimate of these degrees of com-
plication requires an intimate and extensive
knowledge of structure throughout the class.
There would seem to be an arbitrary element
here, — that of our individual appreciation of
structural character. If one man holds a certain
kind of structural characters superior to another,

MEANING OF ORDERS. 73

ne will establish the rank of the order upon that
feature, while some other naturalist, appreciating
a different point of the structure more highly,
will make that the test character of the group.
Let us see whether we can eliminate this arbitra-
ry element in our estimate of these groups, and
lind any mode of determining orders that shall
be unquestionable, and give us results as positive
as a chemical analysis according to quantitative
elements. I believe that there are such absolute
tests of structural relations. It is my conviction,
that orders, like all the other groups of the
Animal Kingdom, have a positive existence in
Nature with definite limits ; that no arbitrary
element should enter into any part of our classi-
fications; and that we have already the key by
which to solve this question about orders.

To illustrate this statement, I must return to
the class of Insects. We have seen that they
are divided into three orders : the long cylindri-
cal Centipedes, with the body divided throughout
in uniform rings, like the worms; the Spiders,
with the body divided into two regions ; and the
Winged Insects, with head, chest, and hind body
distinct from each other, forming three separate
regions. In the first group, the Centipedes, the
nervous system is scattered through the whole
body, as in the Worms ; in the Spiders it is con-
centrated in two nervous swellings, as in Crusta-

74 MEANING OF ORDERS.

cea, the front one being the largest ; and in the>
Insects there are three nervous centres, the larg-
est in the head, a smaller one in the chest, and
the smallest in the hind body. Now according
to this greater or less individualization of parts,
with the corresponding localization of the ner-
vous centres, naturalists have established the rel-
ative rank of these three groups, placing Centi-
pedes lowest, Spiders next, and Winged Insects
highest. But naturalists may, and indeed they
actually do, differ as to this estimation of tho
anatomical structure, for the Spiders are placed
above Insects by some naturalists, and many even
consider them a distinct class. Have we, then,
any means of testing its truth to Nature ? Let us
look at the development of these animals, taking
the highest order as au illustration, that we may
have the whole succession of changes.

All know the story of the Butterfly with its
three lives, as Caterpillar, Chrysalis, and Winged
Insect. I speak of its three lives, but we must
not forget that they make after all but one life,
and that the Caterpillar is as truly the same be-
ing with the future Butterfly, as the child is the
same being with the future man. The old signifi-
cance of the word metamorphosis — the fabled
transformation of one individual into another, in
which so much of the imagination and poetical
culture of the ancients found expression — still

MEANING OF ORDERS. 75

clings to us ; and where the different phases of
the same life assume such different external
forms, we are apt to overlook the fact that it is one
single continuous life. To a naturalist, metamor-
phosis is simply growth ; and in that sense the
different stages of development in animals that
undergo their successive changes within the egg
are as much metamorphoses as the successive
phases of life in those animals that complete their
development after they are hatched.

But to return to our Butterfly. In its most
imperfect, earliest condition, it is Worm-like, the
body consisting of thirteen uniform rings ; but
when it has completed this stage of existence, it
passes into the Chrysalis state, during which the
body has two regions, the front rings being sol-
dered together to form the head and chest, while
the hind joints remain distinct ; and it is only
when it bursts from its Chrysalis envelope, as a
complete Winged Insect, that it has three distinct
regions of the body. Do not the different periods
of growth in this highest order explain the rela-
tion of all the orders to each other? The earliest
condition of an animal cannot be its highest con-
dition,— it does not pass from a more perfect to
a less perfect state of existence. The history of
its growth is, on the contrary, the history of its
progress in development; and therefore, when
we find that the first stage of growth in the

76 MEANING OF ORDERS.

Winged Insect transiently represents a struct ura*
character that is permanent in the lowest order
of its class, that its second stage of growth tran-
siently represents a structural character that is
permanent in the second order of its class, and
that only in the last stage of its existence does
the Winged Insect attain its complete and perfect
condition, we may fairly infer that this division
of the class of Insects into a gradation of orders,
placing Centipedes lowest, Spiders next, and
Winged Insects highest, is true to Nature.

This is not the only instance in which the em-
bryological evidence confirms perfectly the ana-
tomical evidence on which orders have been dis-
tinguished, and I believe that Embryology will
give us the true standard by which to test the
accuracy of our ordinal groups. In the class of
Crustacea, for instance, the Crabs have been
placed above the Lobsters by some naturalists, in
consequence of certain anatomical features ; but
there may easily be a difference of individual
opinion as to the relative value of these features.
When we find, however, that the Crab, while un-
dergoing its changes in the egg, passes through
a stage in which it resembles the Lobster much
more than it does its own adult condition, we
cannot doubt that its earlier state is its lower one,
and that the organization of the Lobster is not as
high in the class of Crustacea as that of the

MEANING OF ORDERS. 77

Crab. While using illustrations of this kind,
however, I must guard against misinterpretation.
These embryological changes are never the pass-
ing of one kind of animal into another kind of
animal ; the Crab is none the less a Crab during
that period of its development in which it resem-
bles a Lobster ; it simply passes, in the natural
course of its growth, through a phase of ex-
istence which is permanent in the Lobster, but
transient in the Crab. Such facts should stimu-
late all our young students to embryological
investigation, as a most important branch of
study in the present state of our science.

But while there is this structural gradation
among orders, establishing a relative rank be-
tween them, are classes and branches also linked
together as a connected chain ? That such a
chain exists throughout the Animal Kingdom
has long been a favorite idea, not only among
naturalists, but also in the popular mind. Lam-
arck was one of the greatest teachers of this
doctrine. He held, not only that branches and
classes were connected in a direct gradation, but
that within each class there was a regular series
of orders, families, genera, and species, forming
a continuous chain from the lowest animals to
the highest, and that the whole had been a grad-
ual development of higher out of lower forms.
I have already alluded to his division of the

78 MEANING OF ORDERS.

Animal Kingdom into the Apathetic, Sensitive,
and Intelligent animals. The Apathetic were
those devoid of all sensitiveness except when
aroused by the influence of some external agent.
Under this head he placed five classes, includ-
ing the Infusoria, Polyps, Star-Fishes, Sea-Ur-
chins, Tunicata, and Worms, — thus bringing
together indiscriminately Radiates, Mollusks, and
Articulates. Under the head of Sensitive he
had also a heterogeneous assemblage, including
Winged Insects, Spiders, Crustacea, Annelids,
and Barnacles, all of which are Articulates, and
with these he placed in two classes the MolluSks,
Conchifera, Gasteropoda, and Cephalopoda. Un-
der the head of Intelligent he brought together a
natural division, for he here united all the Ver-
tebrates.

He succeeded in this way in making out a
series which seemed plausible enough, but when
we examine it, we find at once that it is perfectly
arbitrary ; for he has brought together animals
built on entirely different structural plans, when
he could find characters among them that seemed
to justify his favorite idea of a gradation of qual-
ities. Blainville attempted to establish the same
idea in another way. He founded his series on
gradations of form, placing together in one divis-
ion all animals that he considered vague and in-
definite in form, and in another all those that he

MEANING OF ORDERS. 79

considered symmetrical. Under a third head he
brought together the Radiates ; but his symmet-
rical division united Articulates, Mollusks, and
Vertebrates in the most indiscriminate nlanner.
He sustained his theory by assuming intermediate
groups, — as, for instance, the Barnacles be-
tween the Mollusks and Articulates, whereas
they are as truly Articulates as Insects or Crabs.
Thus, by misplacing certain animals, he arrived
at a series which, like that of Lamarck, made a
strong impression on the scientific world, till a
more careful investigation of facts exposed its
fallacy.

Oken, the great German naturalist, also at-
tempted to establish a connected chain through-
out the Animal Kingdom, but on an entirely
different principle ; and I cannot allude to this
most original investigator, so condemned by some,
so praised by others, so powerful in his influence
on science in Germany, without attempting to
give some analysis of his peculiar philosophy.
For twenty years his classification was accepted
by his countrymen without question ; and though
I believe it to be wrong, yet, by the ingenuity
with which he maintained it, he has shed a flood
of light upon science, and has stimulated other
naturalists to most important and interesting in-
vestigations.

This famous classification was founded upon

80. MEANING OF OHDERS.

the idea that the system of man, the most perfect
created being, is the measure for the whole Ani-
mal Kingdom, and that in analyzing his organi-
zation we have the clew to all organized beings.
The structure of man includes two systems of
organs : those which maintain the body in its in-
tegrity, and which he shares in some sort with
the lower animals,- — the organs of digestion, cir-
culation, respiration, and reproduction ; and that
higher system of organs, the brain, spinal mar-
row, and nerves, with the organs of sense, on
which all the manifestations of the intelligent
faculties depend, and by which his relations to
the external world are established and controlled :
the whole being supported by a solid bony frame
and surrounded by flesh, muscles, and skin. On
account of this fleshy envelope of the hard parts
in all the higher animals, Oken divided the Ani-
mal Kingdom into two groups, the Vertebrates
and Invertebrates, or, as he called them, the
" Eingeweide und Fleisch-Thiere," — which we
may translate as the Intestinal Animals, or those
that represent the intestinal systems of organs,
and the Flesh Animals, or those that combine all
the systems of organs under one envelope of
flesh. Let us examine a little more closely this
singular theory, by which each branch of the In-
vertebrates becomes, as it were, the exponent of
a special system of organs, while the Vertebrates,

MEANING OF ORDERS. 81

with man at their head, include all these sys-
tems.

According to Oken, the Radiates, the lowest
type of the Animal Kingdom, embody digestion.
They all represent a stomach, whether it is the
simple sac of the Polyps, or the cavity of the
Acalephs, with its radiating tubes traversing the
gelatinous" mass of the body, or the cavity and
tubes of the Echinoderms, enclosed within walls
of their own.

The Mollusks represent circulation; and his
division of this type into classes, according to
what he considers the higher or lower organ-
ization of the heart, agrees with the ordinary
division into Acephala, Gasteropoda, and Cepha-
lopoda.

The Articulates are the respiratory animals in
this classification : they represent respiration.
The Worms, breathing, as he asserts, through the
whole surface of the skin, without special breath-
ing organs, are the lowest ; the Crustacea, with
gills, or aquatic breathing organs, come next;
and he places the Insects highest, with their
branching tracheae, admitting air to all parts of
the body.

The Vertebrates, or Flesh Animals, with their
four classes, represent the Bones, the Muscles,
the Nerves, and the Organs of Sense, the Fishes
being par excellence the bony animals, the Rep-

4* F

82 MEANING OF ORDERS.

tiles representing especially the muscular system
the Birds the nervous system, while in the Mam-
malia the organs 'of the senses are most highly
developed.

This theory, according to which there are as
many great divisions or classes as there are
structural systems or combinations of systems in
the Animal Kingdom, seemed natural and signifi-
cant, and there was something attractive in the
idea that man represents, as it were, the syn-
thetic combination of all these different systems.
Oken also, in his exposition of his mode of
classification, showed an insight into the struct-
ure and relations of animals that commended it
to the interest of all students of Nature, and en-
titles him to their everlasting gratitude. Never-
theless, his theory fails, when it is compared with
facts. For instance, there are many Worms that
have no respiration through the skin, while his
appreciation of the whole class is founded on that
feature ; and in his type representing circulation,
the Mollusks, there are those that have no heart
at all.

It would carry me too far into scientific details,
were I to explain all the points at which this
celebrated classification fails. Suffice it to say,
that there is no better proof of the discrepancy
bet-ween the system and the facts than the con-
stant changes in the different editions of Oken's

MEANING OF ORDEKS. 83

own works and in the publications of his follow-
ers founded upon his views, showing that they
were themselves conscious of the shifting and
unstable character of their scientific ground.

84 GRADATION AMONG ANIMALS.

CHAPTER VI.

GRADATION AMONG ANIMALS.

WHAT, then, is the relation of these larger
groups to each other, if they do not stand in a
connected series from the lowest to the highest ?
How far are each of the branches and each of
the classes superior or inferior one to another ?
All agree, that, while Vertebrates stand at
the head of the Animal Kingdom, Radiates are
lowest. There can be no doubt upon this point ;
for, while the Vertebrate plan, founded upon a
double symmetry, includes the highest possibili-
ties of animal organization, there is a certain mo-
notony of structure in the Radiate plan, in which
the body is divided into a number of identical
parts, bearing definite relations to a central verti-
cal axis. But while all admit that Vertebrates
are highest and Radiates lowest, how do the Ar-
ticulates and Mollusks stand to these and to each
other ? To me it seems, that, while both are de-
cidedly superior to the Radiates and inferior to
the Vertebrates, we cannot predicate absolute
superiority or inferiority of organization of either

GRADATION AMONG ANIMALS. 85

group as compared with the other ; they stand
on one structural level, though with different
tendencies, — the body in Mollusks having always
a soft, massive, concentrated character, with
great power of contraction and dilatation, while
the body in Articulates is divided by transverse
articulations, and has nothing of this compact-
ness and concentration, but, on the contrary, is
usually marked by a conspicuous external dis-
play of limbs and other appendages, and by a re-
markable elongation of the body, — that feature
characterized by Baer when he called them the
Longitudinal type. There is in the Articulates
an extraordinary tendency toward outward ex-
pression singularly in contrast to the soft, con-
tractile body of the Mollusks. We need only
remember the numerous Insects with small bod-
ies and enormously large wings, or the Spiders
with little bodies and long legs, or the number
and length of the claws in the Lobsters and
Crabs, as 'illustrations of this statement for the
Articulates, while the soft, compact body of the
Oyster or of the Snail is equally characteristic of
the Mollusks ; and though it may seem that this
assertion cannot apply to the highest class of
Mollusks, the Cephalopoda, including the Cuttle-
Fishes with their long arms or feelers, yet even
these conspicuous appendages have considera-
ble power of contraction and dilatation, and in

86 GRADATION AMONG ANIMALS.

the Nautili may be drawn completely within the
shell. If this view be correct, these two types
occupy an intermediate position between the
highest and the lowest divisions of the Animal
Kingdom, but stand on equal ground when com-
pared with each other.

Another, though a less direct, evidence that
there is np absolute structural superiority or in-
feriority between these two types as a whole
maybe found in the fact that the most pro-
found naturalists who have attempted a serial
arrangement of the whole Animal Kingdom have
differed in their estimate of these two divisions,
some placing the Mollusks highest, while others
have given the ascendency to the Articulates.

But is there a transition from Radiates to
Mollusks, or from Articulates to Vertebrates, or
from any one of these divisions into any other ?
Let us first consider the classes as they stand
within their divisions. We have seen that there
are three classes of Radiates, — Polyps, Acalephs,
and Echinoderms; three classes of Mollusks, —
Acephala, Gasteropoda, and Cephalopoda ; three
classes of Articulates, — Worms, Crustacea, and
Insects ; and, according to the usually accepted
classification, four classes of Vertebrates, —
Fishes, Reptiles, Birds, and Mammalia. If there
is indeed a transition between all these classes,
it must become clear to us, when we have accu-
rately interpreted their relative standing.

GRADATION AMONG ANIMALS. 87

Taking first, then, the lowest branch, how do
the classes stand within the limits of the type of
Radiates ? I think I have said enough of these
different classes to show that Polyps as a whole
are inferior to the Acalephs as a whole, and that
Acalephs as a whole are inferior to Echinoderms
as a whole. But if they are linked together as a
connected series, then the lowest Acaleph should
stand next in structure above the highest Polyp ;
and the lowest Echinoderm next above the high-
est Acaleph. So far from this being the case,
there are, on the contrary, many Acalephs which,
in their specialization, are unquestionably lower
in the scale of life than some Polyps, while
there are some Echinodernis lower in the same
sense than many Acalephs.

This remark applies equally to the classes
within the other types ; they stand, as an average,
relatively to each other, lower and higher, but,
considered in their diversified specification, there
are some members of the higher classes that are
inferior in organization to some members of the
lower classes. The same is true of the great di-
visions as compared with each other. Instead of
the highest Radiates being always lower in organ-
ization than the lowest Mollusks, there are many
Star-Fishes and Sea-Urchins -higher in organiza-
tion than some Mollusks ; and so when we pass
from this branch to the Articulates, if we assume

88 GRADATION AMONG ANIMALS.

for the moment, as some naturalists believe, that
the Mollusks are the inferior type, the Cuttle-
Fishes are certainly very superior animals to
most of the Worms ; and passing from Articu-
lates to Vertebrates, not only are there Insects of
a more complex organization than the lowest
Fishes, but we bring~ together two kinds of ani-
mals so remote from each other in structure that
the wildest imagination can scarcely fancy a tran-
sition between them.

A comparison may make my meaning clearer
as to the relative standing of these groups. The
Epic Poem is a higher order of composition than
the Song, — yet we may have an Epic Poem
which, from its inferior mode of execution,
stands lower than a Song that is perfect of its
kind. So the plan of certain branches is more
comprehensive and includes higher possibilities
than that of others, while at the same time there
may be species in which the higher plan is exe-
cuted in so simple a manner that it places their
organization below some more highly developed
being built on a lower plan. It is a poor com-
parison, because everything that God has made
is perfect of its kind and in its place, though rel
atively lower or higher ; yet it is only by compar-
ison of what is, after all, akin, — of mind with
mind, — even though so far apart as the works
of the divine and the human reason, that we

GRADATION AMONG ANIMALS.

89

may arrive at some idea, however dim, of the
mental operations of the Creative Intellect.

It is, then, in their whole bulk that any of
these groups is above any other. We may repre-
sent the relative positions of the classes by a dia-
gram in which each successive class in every type
starts at a lower point than that at which the
preceding class closes. Taking the Polyps as the
lowest class of Radiates, for instance, its highest
animals rise above the lowest members of the
Acalepbs, but then the higher members of the
class of Acalephs reach a point far above any of
the Polyps, — and so on.

RADIATES. MOLLUSKS. ARTICULATES. VERTEBRATES.

Ech

no-

Cepl

derma.

pod

Acal

phs.

Gas

pod

.ero-
a.

Polv

ps. Acej

hala.

Crus

Inse
acca.

cts.

Via

Kept

Bir

ilca.

If this view be correct, it sets aside the possi-
bility of any uninterrupted series based on abso-
lute superiority or inferiority of structure, on
which so much ingenuity and intellectual power
have been wasted.

But it is not merely upon the structural rela-
tions established between these groups by ana-

90 GRADATION AMONG ANIMALS.

tomical features in the adult that we must decide
this question. We must examine it also from
the embryological point of view. Every animal
in its growth undergoes a succession of changes :
is there anything in these changes implying a
transition of one type into another ? Baer has
given us the answer to this question. He has
shown that there are four distinct modes of de-
velopment, as well as four plans of structure ;
and though we have seen that higher animals of
one class pass through phases of growth in which
they transiently resemble lower animals of the
same class, yet each one of these four modes of
development is confined within the limits of the
type, and a Vertebrate never resembles, at any
stage of its growth, anything but a Vertebrate,
or an Articulate anything but an Articulate, or a
Mollusk anything but a Mollusk, or a Radiate
anything but a Radiate.

Yet, although there is no embryological transi-
tion of one type into another, the gradations of
growth within the limits of the same type and the
same class, already alluded to, are very striking
throughout the Animal Kingdom. There are
periods in the development of the germ in the
higher members of all the types, when they
transiently resemble in their general outline the
lower representatives of the same type, just as we
have seen that the higher orders of one class

GRADATION AMONG ANIMALS. 91

pass through stages of development in which they
transiently resemble lower orders of the same
class. This gradation of growth corresponds to
the gradation of rank in adult animals, as estab-
lished upon comparative complication of struct-
ure. For instance, according to their structural
character, all naturalists have placed Fishes low-
est in the scale' of Vertebrates. Now all the
higher Vertebrates have a Fish-like character at
first, and pass successively through phases in
which they vaguely resemble other lower forms
of the same type before they assume their own
* characteristic form ; and this is equally true of
the other great divisions, so that the history of
the individual is, in some sort, the history of its
type.

There is still another aspect of this question,
— that of time. If neither the gradation of
structural rank among adult animals nor the
gradation of growth in their embryological de-
velopment gives us any evidence of a transition
between types, does not the sequence of animals
in their successive introduction upon the globe
afford any proof of such a connection ? In this
relation, I must briefly allude to the succession
of geological formations that compose the crust
of our globe. The limits of this article will not
allow me to enter at any length into the geologi-
cal details connected with this question; but I

92 GRADATION AMONG ANIMALS.

will, in the most cursory manner, give a sketch
of the great geological periods, as generally ac-
cepted now by geologists.

The first of these periods has been called the
Azoic or lifeless period, because it is the only one
containing stratified deposits in which there are
no remains of organic life, and it is therefore
supposed that at that early stage of the world's
history the necessary conditions for the mainte-
nance of animals and plants were not yet estab-
lished. After this, every great geological period
that follows has been found to be characterized
by a special set of animals and plants, differing
from all that follow and all that precede it, till
we arrive at our own period, when Man, with the
animals and plants that accompany him on earth,
was introduced.

There is, then, an order of succession in time
among animals ; and if there has been any tran-
sition between types and classes, any growth of
higher out of lower forms, it is here that we
should look for the evidence of it. According to
this view, we should expect to find in the first
period in which organic remains are found at all
only the lowest type, and of that type only the
lowest class, and, indeed, if we push the theory
to its logical consequences, only the lowest forms
of the lowest class. What are now the facts?
This continent affords admirable opportunities for

GRADATION AMONG ANIMALS. 93

the investigation of this succession, because, in
consequence of its mode of formation, we have,
in the State of 'New York, a direct, unbroken se-
quence of all the earliest geological deposits.

The rjdge of low hills, called the Laurentian
Hills, along the line of division between Canada
and the States was the first American land lifted
above the ocean. That land belongs to the Azoic
period, and contains no trace of life. Along the
base of that range of hills lie the deposits of the
next great geological period, the Silurian ; and
the State of New York, geologically speaking,
belongs almost entirely to this Silurian period,
with its lowest Taconic division, and the Devon-
ian period, the third in succession of these great
epochs. I need hardly remind those of my read-
ers who have travelled through New York, and
have visited Niagara or Trenton, or, indeed, any
of the localities where the broken edges of the
strata expose the buried life within them, how
numerous this early population of the earth must
have been. No one who has held in his hand one
of the crowded slabs of sandstone or limestone,
or slate full of Crustacea, Shells, and Corals,
from any of the old Silurian or Devonian beaches
which follow each other from north to south
across the State of New York, can suppose that
the manifestation of life was less multitudinous
then than now.

94 GRADATION AMONG ANIMALS.

Now, what does this fossil creation tell us ? It
says this: that, in the Silurian period, taken in
its most comprehensive sense, the first in which
organic life is found at all, there were the three
classes of Radiates, the three classes of Mollusks,
two of the classes of Articulates, and one class of
Vertebrates. In other words, at the dawn of life
on earth, the plan of the animal creation with its
four fundamental ideas'was laid out, — Radiates,
Mollusks, Articulates, and Vertebrates were pres-
ent at that first representation of life upon our
globe. If, then, all the primary types appeared
simultaneously, one cannot have grown out of
another, — they could not be at once contempo-
raries and descendants of each other.

The diagram on the opposite page represents
the geological periods in their regular succession,
and the approximate time at which all the types
and all the classes of the Animal Kingdom were
introduced ; for there is still some doubt as to the
exact period of the introduction of several of the
classes, though all geologists are agreed respect-
ing them, within certain limits, not very remote
from each other, according to geological esti-
mates of time.

If such discussions were not inappropriate here
from their technical character, I think I could
show, upon combined geological and zoological
evidence, that the classes which are not present

GRADATION AMONG ANIMALS.

95

PBIMABT.

SECONDARY.

S I I

? J

96 GRADATION AMONG ANIMALS.

with the others at the beginning, such as Insects
among Articulates, or Reptiles, Birds, and Mam-
malia among Vertebrates., are always introduced
at the time when the conditions essential to their
existence are established, — 'as, for instance, Rep-
tiles, at the period when the earth was not fully
redeemed from the waste of waters, and exten-
sive marshes afforded means for the half-aquatic,
half-terrestrial life even now characteristic of all
our larger Reptiles, while Insects, so dependent
on vegetable growth, make their appearance with
the first forests ; so that we need not infer, be-
cause these and other classes come in after the
earlier ones, that they are therefore a growth out
of them, since it is altogether probable that they
would not be created till the conditions necessary
for their maintenance on earth were established.
From a merely speculative point of view it
seems to me natural to suppose that the physical
and the organic world have progressed together,
and that there is a direct relation between the
successive creations and the condition of the
earth at the time of those creations. We know
that all the beings of the Silurian and Devonian
periods were marine ; the land, so far as it existed
in their time, consisted of great beaches, and along
those shores, wherever any part of the continent
was lifted above the level of the waters, the Silu-
rian and Devonian animals lived. Later in the

GRADATION AMONG ANIMALS. 97

marshes and the fern-forests of the Carboniferous
period, Reptiles and Insects found their place ;
and only when the earth was more extensive,
when marshes had become dry land, when islands
had united to form cpntinents, when mountain-
chains had been thrown up to make the inequali-
ties of the surface, were the larger quadrupeds
introduced, to whose mode of existence all these
circumstances are important accessories.

But while all the types and most of the classes
were introduced upon the earth simultaneously
at the beginning, these types and classes have
nevertheless been represented in every great geo-
logical period by different sets or species of ani-
mals. In this sense, then, there has been a gra-
dation in time among animals, and every succes-
sive epoch of the world's physical history has had
its characteristic population. We have found
that there is a correspondence between the grada-
tion of structural complication among adult ani-
mals as known to us to-day, which we may call
the Series of Rank, and the gradation of embry-
ological changes in the same animals,- which we
may call the Series of Growth ; and there is
also a correspondence between these two series
and the order of succession in time, that estab-
lishes a certain gradation in the introduction of
animals upon earth, and which we may call the
Series of Time.

98 GRADATION AMONG ANIMALS.

Take as an illustration the class of Echino-
derms. The first representatives of this class
were a sort of Star-Fishes on stems ; then were
introduced animals of the same order without
stems ; in later periods come in the true Star-
Fishes and Sea-Urchins ; and the highest order
of the class, the Holothurians, are introduced
only in the present geological epoch. Compare
now with this the ordinal division of the class as
it exists to-day. The present representative of
those earliest Echinoderms on stems is an animal
that upon structural evidence stands lowest in
the class ; next above it are the Comatula3, cor-
responding to the early Echinoderms without
stems ; next in our classification are the Star-
Fishes and Sea-Urchins ; and the Holothurians
stand highest, on account of certain structural
features that place them at the head of their
class. The Series of Time and the Series of
Rank, then, accord perfectly, and investiga-
tions of the embryological development of these
animals have shown that the higher Echinoderms
pass through changes, during their growth, that
indicate the same kind of gradation, for the young
in some of them have a stem which is gradually
dropped, and their successive phases of develop-
ment recall the adult forms of the lower orders.

Take as another illustration the class of Pol-
yps. First in time among the early Reef-Build-

GRADATION AMONG ANIMALS. 99

ers, who wrought their myriad lives into the solid
crust of our globe then, as their successors do now,
we find a peculiar kind of Polyp Coral. Theso
old Corals have their representatives among the
present Polyps, and from their structure they
are placed lowest in their class, while the embry-
ological development of the higher ones recalls
in the younger condition of the germ the same
character. I might multiply examples, and
draw equally striking illustrations from the other
classes ; and though these correspondences can-
not be fully established while our knowledge of
the embryological growth of animals is so scanty,
and there remain so many gaps in our informa-
tion about their geological succession, yet wher-
ever we have been able to trace the connected
history of any group of animals in time, and to
compare it with the history of their embryologi-
cal development and their structural relations as
they exist to-day, the correspondence is found to
be so complete as to justify us in the belief that
it will not fail in other instances.

I may add that a gradation of exactly the same
character controls the geographical distribution
of animals over the surface of the globe. Here
again I must beg my readers to take much of the
evidence, which, if expanded, would fill many
volumes, for granted, since it would be entirely
inappropriate here. But I may briefly state that

100 GRADATION AMONG ANIMALS.

animals are not scattered over the surface of our
globe at random, but that they are associated to-
gether in what are called fauna, and that these
faunae have their homes within certain districts
called by naturalists zoological provinces. The
limits of these provinces are absolutely fixed, in
the ocean as well as on the land, by certain phys-
ical conditions connected with climate, with alti-
tude, with the pressure of the atmosphere, the
weight of the water, etc. ; and this is true even
for animals of migratory habits, for all such mi-
grations are periodical, and have boundaries as
definite and impassable as those that limit the per-
manent homes of animals. There is a certain
series established by the relations between differ-
ent kinds of animals, as thus distributed over the
globe, agreeing with the gradation in their rank,
their growth, and. their succession in time ; — the
law which distributes animals in adjoining faunae,
arid in accordance both with their relative superi-
ority or inferiority, and with the physical condi-
tions essential to their existence, being the same
as that which controls their structural relations,
their embryological development, and their suc-
cession in time.

What, then, does this correspondence between
the Series of Rank, the Series of Growth, the
Series of Time, and the Series of Geographi-
cal Distribution in the life of animals teach us ?

GRADATION AMONG ANIMALS. 101

Suicly not that the connection between animals
is a material one ; for the same kind of relation
exists between lower and higher animals of one
type or one class to-day, in their structural fea-
tures, in their embryological growth, and in their
geographical distribution, as we trace in their
order of succession in time ; and therefore, if
this kind of evidence proves that the later ani-
mals are the descendants of the earlier in any
genealogical sense, it should also prove that the
animals living in one part of the earth at present
grow out of animals living in another part,* and
that the higher animals of one class as it exists
now are developed out of the lower ones. The
first of these propositions needs no refutation ;
and with regard to the second, all our investiga-
tions go to show that every being born into the
world to-day adheres to its individual law of life,
and though it passes through transient phases of
growth resembling other beings of its own kind,
never pauses at a lower stage of development,
or passes on to a higher condition than the one
it is bound to fill.

If, then, this connection is not a material one,
what is it ? — for that such a connection does ex-
ist throughout the Animal Kingdon, as intimate,
as continuous, as complex, as any series which the
development theorists have ever contended for, is
not to be denied. What can it be but an intel-

102 GRADATION AMONG ANIMALS.

Icctual one ? These correspondences are corre-
spondences of thought, — of a thought that is
always the same, whether it is expressed in the
history of the type through all time, or in the life
of the individuals that represent the type at the
present moment, or in the growth of the germ of
every being born into that type to-day. In other
words, the same thought that spans the whole
succession of geological ages controls the struct-
ural relations of all living beings as well as their
distribution over the surface of the earth, and is
repeated within the narrow compass of the small-
est egg in which any being begins its growth.

ANALOGOUS TYPES. 103

CHAPTER VII.

ANALOGOUS TYPES.

I COME now to an obscure part of my subject,
very difficult to present in a popular form, and
yet so important in the scientific investigations
of our day that I cannot omit it entirely. I al-
lude to what are called by naturalists Collateral
Series or Parallel and Analogous Types. These
are by no means difficult to trace, because they
are connected by seeming resemblances, which,
though very likely to mislead and perplex the
observer, yet naturally suggest the association
of such groups. Let me introduce the subject
with the statement of some facts.

There are in Australia numerous Mammalia,
occupying the same relation and answering the
same purposes as the Mammalia of other coun-
tries. Some of them are domesticated by the na-
tives, and serve them with meat, milk, and wool,
as our domesticated animals serve us. Repre-
sentatives of almost all types, Wolves, Foxes,
Sloths, Bears, Weasels, Martens, Squirrels, Rats,
etc., are found there ; and yet, though all these

104 ANALOGOUS TYPES.

animals resemble ours so closely that the Eng-
lish settlers have called many of them by the
same names, there are no genuine Wolves, Foxes,
Sloths, Bears, Weasels, Martens, Squirrels, or
Eats in Australia. The Australian Mammalia
are peculiar to the region where they are found,
and are all linked together by two remarkable
structural features which distinguish them from
all other Mammalia and unite them under one
head as the so-called Marsupials. They bring
forth their young in an imperfect condition, and
transfer them to a pouch, where they remain
attached to the teats of the mother till their
development is as far advanced as that of other
Mammalia at the time of their birth ; and they
are further characterized by an absence of that
combination of transverse fibres forming the large
bridge which unites the two hemispheres of the
brain in all the other members of their class.
Here, then, is a series of animals parallel with
ours, separated from them by anatomical fea-
tures, but so united with them by form and ex-
ternal features that many among them have been
at first associated together.

Cuvier has already alluded to this, when he
speaks of subordination of characters, distinguish-
ing between those controlling the whole organ-
ization and those that play only a secondary
part in it. The skill of the naturalist consists

ANALOGOUS TYPES. 105

in detecting the difference between the two, so
that he may not take the more superficial features
as the basis of his classification, instead of those
important ones which, though often less easily
recognized, are more deeply rooted in the organ-
ization. It is a difference of the same nature
as that between affinity and analogy, to which I
have alluded before, when speaking of the in-
grafting of certain features of one type upon ani-
mals of another type, thus producing a superficial
resemblance, not truly characteristic. In the
Reptiles, for instance, there are two groups, —
those devoid of scales, with naked skin, laying
numerous eggs, but hatching their young in an
imperfect state, and the Scaly Reptiles, which lay
comparatively few eggs, but whose young, when
hatched, are completely developed, and undergo
no subsequent metamorphosis. Yet, notwith-
standing this difference in essential features of
structure, and in the mode of reproduction and
development, there is such an external resem-
blance between certain animals belonging to the
two groups that they were associated together
even by so eminent a naturalist as Linna3us.
Compare, for example, the Serpents among the
Scaly Reptiles with the Caecilians among the
Naked Reptiles. They have the same elongated
form, and are both destitute of limbs ; the head
in both is on a level with the body, without any

5*

106 ANALOGOUS TYPES.

contraction behind it, such as marks the neck in
the higher Reptiles, and moves only by the action
of the backbone ; they are singularly alike in
their external features, but the young of the Ser-
pent are hatched in a mature condition, while
the young of the type to which the Chilians
belong undergo a succession of metamorphoses
before their resemblance to the parent is clearly
denned. Or compare the Lizard and the Sala-
mander, in which the likeness is perhaps even
more striking; for any inexperienced observer
would mistake one for the other. Both are in
some respects superior to the Serpents and Cse-
cilians, for in them the head moves freely on the
neck, and they creep on short, imperfect legs.
But the Lizard is clothed with scales, while
the body of the Salamander is naked, and the
young of the former is complete when hatched,
while the Tadpole born from the Salamander has
a life of its own to live, with certain changes to
pass through before it assumes its mature con-
dition ; during the early part of its life it is even
destitute of legs, and has gills like the Fishes.

Above the Lizards and Salamanders, highest
in the class of Reptiles, stand two other collat-
eral types, — the Turtles at the head of the Scaly
Reptiles, the Toads and Frogs at the head of the
Naked Reptiles. The external likeness between
these two groups is perhaps less striking than

ANALOGOUS TYPES. 107

between those mentioned above, on account of
the large shield of the Turtle. But there are
Turtles with a soft covering, and there are some
Toads with a hard shield over the head and neck
at least, and both groups are alike distinguished
by the shortness and breadth of the body and
by the greater development of the limbs as com-
pared with the lower Reptiles. But here again
there is the same essential difference in the mode
of development of their young as distinguishes
all the rest. The two series may thus be con-
trasted : —

Naked Reptiles. Scaly Reptiles.
Toads and Frogs, Turtles,

Salamanders, Lizards,

Csecilians. Serpents.

Such corresponding groups or parallel types,
united only by external resemblance, and dis-
tinguished from each other by essential elements
of structure, exist among all animals, though
they are less striking among Birds on account
of the uniformity of that class. Yet even there
we may trace such analogies, — ,as between the
Palmate or Aquatic Birds, for instance, and the
Birds of Prey, or between the Frigate Bird and
the Kites. Among Fishes such analogies are
very common, often suggesting a comparison
even with land animals, though on account of
the scales and spines of the former the likeness

108 ANALOGOUS TYPES.

may not be easily traced. But the common
names used by the fishermen often indicate these
resemblances, — as, for instance,. Sea-Yulture,
Sea-Eagle, Cat-Fish, Flying-Fish, Sea-Porcupine,
Sea-Cow, Sea-Horse, and the like.

In the branch of Mollusks, also, the same
superficial analogies are found. In the lowest
class of this division of the Animal Kingdom
there is a group so similar to the Polyps, that,
until recently, they have been associated with
them, — the Bryozoa. They are very small ani-
mals, truly allied to the Clams by the plan of
their structure, but resembling the Polyps on
account of a radiating wpeath of feelers around
the upper part of their body: yet, when exam-
ined closely, this wreath is found to be incom-
plete ; it does not form a circle, but leaves an
open space between the two ends, where they
approach each other, so that it has a horseshoe
outline, and partakes of the bilateral symmetry
characteristic of its type and on which its own
structure is based. These series have not yet
been very carefully traced, and young natural-
ists should turn their attention to them, and be
prepared to draw the nicest distinction between
analogies and true affinities among animals.

FAMILY CHAKACTERISTICS 109

JHAPTER VIII.

FAMILY CHARACTERISTICS.

LET us. proceed to a careful examination of
the natural groups of animals called Families
by naturalists, — a subject already briefly alluded
to in a previous chapter. Families are natu-
ral assemblages of animals less extensive than
Orders, but, like Orders, Classes, and Branches,
founded upon certain categories of structure,
as distinct for this kind of group as are those
above specified for the other divisions in the
classification of the Animal Kingdom, which we
have thus far examined.

That we may understand the true meaning
of these divisions, we must not be misled by the
name given by naturalists to this kind of groups.
Here, as in so many other instances, a word
already familiar, and as it were identified with
the special sense in which it had been used,
was adopted by science, and received a new sig-
nification. When naturalists speak of Families
among animals, they do not allude to the proge-
ny of a known stock, as we designate, in com-

110 FAMILY CHARACTERISTICS.

mon parlance, the children or the descendants
of known parents ; they understand by this name
natural groups including different kinds of ani-
mals, having no genetic relations so far as we
know, but agreeing with one another clcrely
enough to leave the impression of a more or
less remote common parentage. The difficulty
here consists in determining the natural limits
of such groups, and in tracing the characteristic
features by which they may be denned; for in-
dividual investigators differ greatly as to the de-
gree of resemblance existing between the mem-
bers of many Families, and there is no kind of
group which presents greater diversity of circum-
scription in the classifications of animals pro-
posed by different naturalists than these so-called
Families.

It should be remembered, however, that, unless
a sound criterion be applied to the limitation of
Families, they, like all other groups introduced
into zoological systems, must forever remain arbi-
trary divisions, as they have been hitherto. A
retrospective glance at the progress of our sci-
ence during the past century, in this connection,
may perhaps help us to solve the difficulty.
Linnaeus, in his System of Nature, does not ad-
mit Families ; he has only four kinds of groups,
— Classes, Orders, Genera, and Species. It was,
as I have stated in a previous chapter, among

FAMILY CHARACTERISTICS 111

plants that naturalists first perceived those gen-
eral traits of resemblance existing everywhere
among the members of natural families, in con-
sequence of which they added this kind of group
to the framework of their system. In France,
particularly, this method was pursued with suc-
cess ; and the improvements thus introduced by
the French botanists were so great, and rendered
their classification so superior to that of Linnae-
us, that the botanical systems in which Families
were introduced were called natural systems, in
contradistinction especially to the botanical clas-
sification of Linnaeus, which was founded upon
the organs of reproduction, and which received
thenceforth the name of the sexual system of
plants. The same method so successfully used
by botanists was soon introduced into Zoology
by the French naturalists of the beginning of
this century, — Lamarck, Latreille, and Cuvier.
But, to this day, the limitation of Families among
animals has not reached the precision which it
has among plants, and I see no other reason for
the difference than the absence of a leading prin-
ciple to guide *us in Zoology.

Families, as they exist in Nature, are based up-
on peculiarities of form as dependent upon struc-
ture ; but though a very large number of them
have been named and recorded, very few are char-
acterized with anything like scientific accuracy.

112 FAMILY CHARACTERISTICS.

It has been a very simple matter to establish such
groups according to the superficial method that
has been pursued, for the fact that they are de-
termined by external outline renders the recogni-
tion of them easy and in many instances almost
instinctive ; but it is very difficult to characterize
them, or, in other words, to trace the connection
between form and structure. Indeed, many
naturalists do not admit that Families are based
upon form ; and it was in trying to account for
the facility with which they detect these groups,
while they find it so difficult to characterize
them, that I perceived them to be always associat-
ed with peculiarities of form. Naturalists have
established Families simply by bringing together
a number of animals resembling each other more
or less closely, and, taking usually the name of
the Genus to which the best known among them
belongs, they have given it a patronymic termi-
nation to designate the Family, and allowed the
matter to rest there, sometimes without even at-
tempting any description corresponding to those
by which Genus and Species are commonly de-
fined.

For instance, from Canis, the Dog, Canidce has
been formed, to designate the whole Family of
Dogs, Wolves, Foxes, etc. Nothing can be more
superficial than such a mode of classification ;
and if these groups actually exist in Nature, they

FAMILY CHARACTERISTICS. 113

must be based, like all the other divisions, upon
some combination of structural characters pecu-
liar to them. We have seen that Branches are
founded upon the general plan of structure,
Classes upon the execution of the plan, Orders
upon the greater or less complication of a given
mode of execution, and we shall find that form,
as determined by structure, characterizes Fami-
lies. I would call attention to this qualification
of my definition ; since, of course, when speak-
ing of form in this connection, I do not mean those
superficial resemblances in external features al-
ready alluded to in my remarks upon Parallel or
Collateral Types. I speak now of form as con-
trolled by structural elements ; and unless we
analyze Families in this way, the mere distin-
guishing and naming them does not advance our
science at all.

Compare, for instance, the Dogs, the Seals,
and the Bears. These are all members of one
order, — that of the Carnivorous Mammalia.
Their dentition is peculiar and alike in all (cut-
ting teeth, canine teeth, and grinders), adapted
for tearing and chewing their food ; and their in-
ternal structure bears a definite relation to their
dentition. But look at these animals with refer-
ence to form. .The Dog is comparatively slender,
with legs adapted for running and hunting his
prey ; the Bear is heavier, with shorter limbs ;

114 FAMILY CHARACTERISTICS.

while the Seal has a continuous uniform outline
adapted for swimming. They form separate
Families, and are easily recognized as such by the
difference in their external outline ; but what is
the anatomical difference producing the peculiar-
ity of form in each, by which they have been
thus distinguished ? It lies in the structure of
the limbs, and especially in that of the wrist
and fingers. In the Seal the limbs are short, and
the wrists are on one continuous line with them,
so that it has no power of bending the wrist or
the fingers, and the limbs, therefore, act like flap-
pers or oars. The Bear has a well-developed paw
with a flexible wrist, but it steps on the whole
sole of the foot, from the wrist to the tip of the
toe, giving it the heavy tread so characteristic of
all the Bears. The Dogs, on the contrary, walk
on tiptoe, and their step, though firm, is light,
while the greater slenderness and flexibility of
their legs add to their nimbleness and swiftness.
By a more extensive investigation of the anatom-
ical structure of the limbs in their connection
with the whole body, it could easily be shown
that the peculiarity of form in these animals is
essentially determined by, or at least stands in
the closest relation to, the peculiar structure of
the wrist and fingers.

Take the Family of Owls, as distinguished
from the Falcons, Kites, etc. Here the differ-

FAMILY CHARACTERISTICS. 115

ence of form consists in the position of the eyes.
In the Owl, the sides of the head are prominent,
and the eye-socket is brought forward. In the
Falcons and Kites, on the contrary, the sides 'of
the Jiead are flattened, and the eyes are set back.
The difference in the appearance of the birds is
evident to the most superficial observer ; but to
call the one Strigidse and the other Falconidae
tells us nothing' of the anatomical peculiarities
on which this difference is founded.

These few examples, selected purposely among
closely Dallied and universally known animals,
may be sufficient to show, that, beyond the general
complication of the structure which character-
izes the Orders, there is a more limited element
in the organization of animals, bearing chiefly
upon their form, which, if it have any general
application as a principle of classification, may
well be considered as essentially characteristic of
the Families. There are certainly closely allied
natural groups of animals, belonging to the same
Order, but including many Genera, which differ
from each other chiefly in their form, while that
form is determined by peculiarities of structure
which do not influence the general structural
complication upon which Orders are based, or re-
late to the minor details of structure on which
Genera are founded. I am, therefore, convinced
that form is the criterion by which Families may

116 FAMILY CHARACTERISTICS.

be determined. The great facility with which
animals may be combined together in natural
groups of this kind without any special investi-
gation of their structure — a superficial method
of classification in which zoologists have lately
indulged to a most unjustifiable degree — con-
vinces me that it is the similarity of form which
has unconsciously led such shallow investigators
to correct results, since upon close examination
it is found that a large number of the Families
so determined, and to which no characters at all
are assigned, nevertheless bear the severest criti-
cism founded upon anatomical investigation.

The questions proposed to themselves by all
students who^^ould characterize Families should
be these : What are, throughout the Animal
Kingdom, the peculiar patterns of form by which
Families are distinguished ? and on what struct-
ural features are these patterns based ? Only the
most patient investigations can give us the an-
swer, and it will be very long before we can write
out the formulae of these patterns with mathe-
matical precision, as I believe we shall be able to
do in a more advanced stage of our science.
But while the work is in progress, it ought to be
remembered that a mere general similarity of
outline is not yet in itself evidence of identity of
form or pattern, and that, while seemingly very
different forms may be derived from the same

FAMILY CHARACTERISTICS. 117

formula, the most similar forms may belong to
entirely different systems, when their derivation
is properly traced.

Our great mathematician, in a lecture delivered
at the Lowell Institute last winter, showed that
in his science, also, similarity of outline does not
always indicate identity of character. Compare
the different circles, — the perfect circle, in which
every point of the periphery is at the same dis-
tance from the centre, with an ellipse in which the
variation from the true circle is -so slight as to be
almost imperceptible to the eye ; yet the latter, like
all ellipses, has its two foci by which it differs from
a circle, and to refer it to the family of circles
instead of the family of ellipses would be overlook-
ing its true character on account of its external
appearance ; and yet ellipses may be so elongated,
that, far from resembling a circle, they make the
impression of parallel lines linked at their ex-
tremities. Or we may have an elastic curve in
which the appearence of a circle is produced by
the meeting of the two ends ; nevertheless it
belongs to the family of elastic curves, in which
may even be included a line actually straight, and
is formed by a process entirely different from that
which produces the circle or the ellipse.

But it is sometimes exceedingly difficult to
find the relation between structure and form in
Families. I remember a case which I had taken

118 FAMILY CHARACTERISTICS.

as a test of the accuracy of the views I enter-
tained upon this subject, and which perplexed
and baffled me for years. It was that of our
fresh-water Mussels, the Family of Unios. There
is a great "variety of outline among them, — some
being oblong and very slender, others broad with
seemingly square outlines, others having a nearly
triangular form, while others again are almost
circular ; and I could not detect among them all
any feature of form that was connected with any
essential element of their structure. At last,
however,. I found this test-character, and since
that time I have had no doubt left in my mind
that form, determined by structure, is the true
criterion of Families. In the Unios it consists
of the rounded outline of the anterior end of the
body reflected in a more or less open curve of
the shell, bending more abruptly along the lower
side with an inflection followed by a bulging.
This bulging corresponds to the most prominent
part of the gills, to which, in a large number of
American Species of this Family, the eggs are ex-
clusively transferred, giving to this part of the
shell a prominence which it has not in any of the
European Species. At the posterior end of the
body this curve then bends upwards and back-
wards again, the outline meeting the side occu-
pied by the hinge and ligament, which, when
very short, may determine a triangular form of

FAMILY CHARACTERISTICS. 119

the whole shell, or, when equal to the lower side
and connected with a great height of the body,
gives it a quadrangular form, or, if the height is
reduced, produces an elongated form, or, finally,
a rounded form, if the passage from one side to
the other is gradual. A comparison of the po-
sition of the internal organs of different Species
of Unios with the outlines of their shells will
leave no doubt that their form is determined by
the structure of the animal.

A few other and more familiar examples may
complete these remarks. Among Climbing Birds,
for instance, which are held together as a more
comprehensive group by the structure of their
feet and by other anatomical features, there are
two Families so widely different in their form
that they may well serve as examples of, this
principle. The Woodpeckers (Picidcz) and the
Parrots (PxUtacidat), once considered as two
Genera only, have both been subdivided, in con-
sequence of a more intimate knowledge of their
generic characters, into a large number of Gen-
era ; but all the Genera of Woodpeckers and all
the Genera of the Parrots are still held together
by their form as Families, corresponding as such
to the two old Genera of Picus and Psittacus.
They are now known as the Families of Wood-
peckers and Parrots ; and though each group in-
cludes a number of Genera combined upon a

120 FAMILY CHARACTERISTICS.

variety of details in the finish of special parts of
the structure, such as the number of toes, the pe-
culiarities of the bill, etc., it is impossible to over-
look the peculiar form characteristic of each. No
one who is familiar with the outline of the Par-
rot will fail to recognize any member of that
Family by a general form which is equally com-
mon to the diminutive Nonpareil, the gorgeous
Ara, and the high-crested Cockatoo. Neither
will any one, who has ever observed the small
head, the straight bill, the flat back, and stiff tail
of the Woodpecker, hesitate to identify the fam-
ily form in any of the numerous Genera into
which this group is now divided. The family char-
acters are even more invariable than the generic
ones ; for there are Woodpeckers which, instead
of the four toes, two turning forward and two
backward, which form an essential generic char-
acter, have three toes only, while the family form
is always maintained, whatever variations there
may be in the characters of the more limited
groups it includes.

The Turtles and Terrapins form another good
illustration of family characters. They consti-
tute together a natural Order, but are distin-
guished from each other as two Families very
distinct in general form and outline. Among
Fishes I may mention the Family of Pickerels,
with their flat, long snout, and slender, almost

FAMILY CHARACTERISTICS. 121

cylindrical body, as contrasted with the plump,
compressed body and tapering tail of the Trout
Family. Or compare, among Insects, the Hawk-
Moths with the Diurnal Butterfly, or with the so-
called Miller, — or, among Crustacea, the com
mon Crab with the Sea-Spider, or the Lobsters
with the Shrimps, — or, among Worms, the
Leeches with the Earth- Worms, — or, among
Mollusks, the Squids with the Cuttle-Fishes, or
the Snails with the Slugs, or the Periwinkles
with the Limpets and Conchs, or the Clam with
the so-called Venus, or the Oyster with the Mother-
of-Pearl shell, — everywhere, throughout the Ani-
mal Kingdom, difference of form points at differ-
ence of Families.

There is a chapter in the Natural History of
Animals that has hardly been touched upon as
yet, and that will be especially interesting with
reference to Families. The voices of animals have
a family character not to be mistaken. All the
Canidse bark and howl : the Fox, the Wolf, the
Dog have the same kind of utterance, though on
a somewhat different pitch. All the Bears growl,
from the White Bear of the Arctic snows to the
small Black Bear of the Andes. All the Cats
miau, from our quiet fireside companion to the
Lions and Tigers and Panthers of the forest and
jungle. This last may seem a strange assertion ;
but to any one who has listened critically to their

6

122 ' FAMILY CHARACTERISTICS.

sounds and analyzed their voices, the roar of the
Lion is but a gigantic miau, bearing about the
same proportion to that of a Cat as its stately
and majestic form does to the smaller, softer,
more peaceful aspect of the Cat. Yet, notwith-
standing the difference in their size, who can look
at the Lion, whether in his more sleepy mood, as
he lies curled up in the corner of his cage, or in
his fiercer moments of hunger or of rage, with-
out being reminded of a Cat ? And this is not
merely the resemblance of one carnivorous ani-
mal to another ; for no one was ever reminded
of a Dog or Wolf by a Lion.

Again, all the Horses and Donkeys neigh ; for
the bray of the Donkey is only a harsher neigh,
pitched on a different key, it is true, but a sound
of the same character, — as the Donkey himself
is but a clumsy and dwarfish Horse. All the
Cows low, from the Buffalo roaming the prairie,
the Musk-Ox of the Arctic ice-fields, or the Jack
of Asia, to the Cattle feeding in our pastures.

Among the Birds, this similarity of voice in
Families is still more marked. We need only re-
call the harsh and noisy Parrots, so similar in
their peculiar utterance. Or take as an example
the web-footed Family, — do not all the Geese and
the innumerable host of Ducks quack ? Does not
every member of the Crow Family caw, whether
it be the Jackdaw, the Jay, or the Magpie, the Rook

FAMILY CHARACTERISTICS. 123

in some green rookery of the Old World, or the
Crow of our woods, with its long, melancholy
caw that seems to make the silence and solitude
deeper ? Compare all the sweet warblers of the
Songster Family, — the Nightingales, the Thrush-
es, the Mocking-Birds, the Robins ; they differ in
the greater or less perfection of their note, but
the same kind of voice runs through the whole
group.

These affinities of the vocal systems among
animals form a subject well worthy of the deep-
est study, not only as another character by which to
classify the Animal Kingdom correctly, but as bear-
ing indirectly also on the question of the origin of
animals. Can we suppose that characteristics like
these have been communicated from one animal
to another ? When we find that all the members
of one zoological Family, however widely scat-
tered over the surface of the earth, inhabiting
different continents and even different hemi-
spheres, speak with one voice, must we not believe
that they have originated in the places where
they now occur with all their distinctive pecu-
liarities ? Who taught the American Thrush to
sing like his European relative ? He surely did
not learn it from his cousin over the waters.
Those who would have us believe that all ani-
mals have originated from common centres and
single pairs, and have been thence distributed

124 FAMILY CHARACTERISTICS.

over the world, will find it difficult to explain
the tenacity of such characters, and their recur-
rence and repetition under circumstances that
seem to preclude the possibility of any commu-
nication, on any other supposition than that of
their creation in the different regions where they
are now found. We have much yet to learn from
investigations of this kind, with reference not
only to Families among animals, but to nation-
alities among men also. I trust that the nature
of languages will teach us as much about the
origin of the races, as the vocal system of the
animals may one day teach us about the origin
of the different groups of animals. At all events,
similarity of vocal utterance among animals is
not indicative of identity of Species ; I doubt,
therefore, whether similarity of speech proves
community of origin among men.

The similarity of motion in Families is another
subject well worth the consideration of the nat-
uralist : the soaring of the Birds of Prey, — the
heavy flapping of the wings in the Gallinaceous
Birds, — the floating of the Swallows, with their
short cuts and angular turns, — the hopping of
the Sparrows, — the deliberate walk of the Hens
and the strut of the Cocks, — the waddle of the
Ducks and Geese, — the slow, heavy creeping of
the Land-Turtle, — the graceful flight of the
Sea-Turtle under the water, — the leaping and

FAMILY CHARACTERISTICS. 125

swimming of the Frog, — the swift run of the
Lizard, like a flash of green or red light in the
sunshine, — the lateral undulation of the Ser-
pent, — the dart of the Pickerel, — the leap of
the Trout, — the rush of the Hawk-Moth through
the air, — the fluttering flight of the Butterfly,

— the quivering poise of the Humming-Bird, —
the arrow-like shooting of the Squid through the
water, — the slow crawling of the Snail on the
land, — the sideway movement of the Sand-Crab,

— the backward walk of the Crawfish, — the
almost imperceptible gliding of the Sea- Anemone
over the rock, — the graceful, rapid motion of the
Pleurobrachia, with its endless change of curve
and spiral. In short, every Family of animals
has its characteristic action and its peculiar
voice ; and yet so little is this endless variety
of rhythm and cadence both of motion and
sound in the organic world understood, that we
lack words to express one half its richness and
beauty.

126 THE CHARACTERS OF GENERA.

CHAPTER IX.

THE CHARACTERS OF GENERA.

THE well-known meaning of the words generic
and specific may serve, in the absence of a more
precise definition, to express the relative impor-
tance of those groups of animals called Genera
and Species in our scientific systems. The Genus
is the more comprehensive of the two kinds of
groups, while the Species is the most precisely
defined, or at least the most easily recognized,
of all the divisions of the Animal Kingdom.
But neither the term Genus nor Species has
always been taken in the same sense. Genus es-
pecially has varied in its acceptation, from the
time when Aristotle applied it indiscriminately
to any kind of comprehensive group, from the
Classes down to what we commonly call Genera,
till the present day.

But we have already seen, that, instead of
calling all the more comprehensive divisions by
the name of Genera, modern science has applied
special names to each of them, and we have now
Families, Orders, Classes, and Branches above

THE CHARACTERS OF GENERA. 127

Genera proper. If the foregoing discussion upon
the nature of these groups is based upon trust-
worthy principles, we must admit that theyv are
all founded upon distinct categories of characters,
— the primary divisions, or the Branches, upon
plan of structure, the Classes upon the manner
of its execution, the Orders upon the greater
or less complication of a given mode of execu-
tion, the Families upon form ; and it now re-
mains to be ascertained whether Genera also
exist in Nature, and by what kind of character-
istics they may be distinguished.

Taking the practice of the ablest naturalists
in discriminating Genera as a guide in our esti-
mation of their true nature, we must, neverthe-
less, remember that even now, while their classi-
fications of the more comprehensive groups usu-
ally agree, they differ greatly in their limitation
of Genera, so that the Genera of some authors
correspond to the Families of others, and vice
versa. This undoubtedly arises from the absence
of a definite standard for the estimation of these
divisions. But the different categories of struct-
ure forming the distinctive criteria of the more
comprehensive divisions once established, the
question is narrowed down to an inquiry into the
special category upon which Genera may be de-
termined ; and if this can be accurately defined,
no difference of opinion need interfere hereaf-
ter with their uniform limitation.

128 THE CHARACTERS OF GENERA.

Considering all these divisions of the Animal
Kingdom from this point of view, it is evident
that the more comprehensive ones must be those
which are based on the broadest characters, —
the Branches, as united upon plan of structure,
standing of course at the head ; next to. these
the Classes, since the general mode of executing
the plan presents a wider category of characters
than the complication of structure on which Or-
ders rest; after Orders come Families, or the
patterns of form in which these greater or less
complications of structure are clothed ; and, pro-
ceeding in the same way from more general to
more special considerations, we can have no other
category of structure as characteristic of Genera
than the details of structure by which members
of the same Family may differ from each other,
and this I consider as the only true basis on
which to limit Genera, while it is at the same
time in perfect accordance with the practice of
the most eminent modern zoologists. It is in
this way that Cuvier has distinguished the large
number of Genera he has characterized in his
great Natural History of the Fishes, published
in connection with Valenciennes. Latreille has
done the same for the Crustacea and Insects ; and
Milne-Edwards, with the co-operation of Haime,
has recently proceeded upon the same principle in
characterizing a great number of Genera among

THE CHARACTERS OF GENERA. 129

the Corals. Many others have followed this ex-
ample, but few have kept in view the necessity of
a uniform mode of proceeding, or, if they have
done so, their researches have covered too limit-
ed a ground to be taken into consideration in a
discussion of principles.

It is, in fact, only when extending over a
whole Class that the study of Genera acquires a
truly scientific importance, as it then shows, in a
connected manner, in what way, by what features,
and to what extent a large number of animals
are closely linked together in Nature. Con-
sidering the Animal Kingdom as a single com-
plete work of one Creative Intellect, consistent
throughout, such keen analysis and close criti-
cism of all its parts have the same kind of inter-
est, in a higher degree, as that which attaches to
other studies undertaken in the spirit of careful
comparative research. These different categories
of characters are, as it were, different peculiari-
ties of style in the author, different modes of
treating the same material, new combinations of
evidence bearing on the same general principles.
The study of Genera is a department of Natural
History which thus far has received too little at-
tention even at the hands of our best zoologists,
and has been treated in the most arbitrary man-
ner ; it should henceforth be made a philosophical
investigation into the closer affinities which nat>

6* I

130 THE CHARACTERS OF GENERA.

urally bind all the representatives of a natural
Family in minor groups.

Genera, then, are divisions of a more restricted
character than any of those we have examined
thus far. Some of them include only one Spe-
cies, while others comprise hundreds ; since cer-
tain definite combinations of characters may be
limited to a single Species, while other combina-
tions may be repeated in many. We have strik-
ing examples of this among Birds : the Ostrich
stands alone in its Genus, while the number of
Species among the Warblers is very great.
Among Mammalia the Giraffe also stands alone,
while Mice and Squirrels include many Species.
Genera are founded, not, as we have seen, on
general structural characters, but on the finish of
special parts, as, for instance, on the dentition.
The Cats have only four grinders in the upper
jaw and three in the lower, while the Hyenas
have one more above and below, and the Dogs
and Wolves have two more above and two more
below. In the last, some of the teeth have also
flat surfaces for crushing the food, adapted es-
pecially to their habits, since they live on vegeta-
ble as well as animal substances. The formation
of the claws is another generic feature. There
is a curious example with reference to this in the
Cheetah, which is again a Genus containing only
one Species. It belongs to the Cat Family, but

THE CHARACTERS OP GENERA. 131

differs from ordinary Lions and Tigers in having
its claws so constructed that it cannot draw them
oack over the paws, though in every other re-
spect they are like the claws of all the Cats,
But while it has the Cat-like claw, its paws are
like those of the Dog, and this singular combina-
tion of features is in direct relation to its habits,
for it does not lie in wait and spring upon its
prey like the Cat, but hunts it like the Dog.

While Genera themselves are, like Families,
easily distinguished, the characters on which
they are founded, like those of Families, are
difficult to trace. There are often features be-
longing to these groups which attract the atten-
tion and suggest their association, though they
are not those which may be truly considered
generic characters. It is easy to distinguish the
Foxes, for instance, by their bushy tail, and
yet that is no true generic character ; the collar
of feathers round the neck of the Vultures leads
us at once to separate them from the Eagles, but
it is not the collar that truly marks the Genus,
but rather the peculiar structure of the feathers
which form it. No Bird has a more striking
plumage than the Peacock, but it is not the ap-
pearance merely of its crest and spreading fan
that constitutes the Genus, but the peculiar struc-
ture of the feathers. Thousands of examples
might be quoted to show how easily Genera may

132 THE CHARACTERS OF GENERA.

be singled out, named, and entered in our sys-
tems, without being duly characterized, and it is
much to be lamented that there is no possibility
of checking the loose work of this kind with which
the annals of our science are daily flooded.

It would, of course, be quite inappropriate to
present here any general revision of these groups ;
but I may present a few instances to illustrate
the principle of their classification, and to show
on what characters they are properly based.
Among Reptiles, we find, for instance, that the
Genera of our fresh-water Turtles differ from
each other in the cut of their bill, in the arrange-
ment of their scales, in the form of their claws,
etc. Among Fishes, the different Genera includ-
ed under the Family of Perches are distinguished
by the arrangement of their teeth, by the serra-
tures of their gill-covers and of the arch to
which the pectoral fins are attached, by the na-
ture and combination of the rays of their fins,
by the structure of their scales, etc. Among In-
sects, the various Genera of the Butterflies differ
in the combination of the little rods which sustain
their wings, in the form and structure of their
antennae, of their feet, of the minute scales
which cover their wings, etc. Among Crustacea,
the Genera of Shrimps vary in the form of the
claws, in the structure of the parts of the mouth,
in the articulations of their feelers, etc. Among

THE CHARACTERS OF GENERA. 133

Worms, the different Genera of the Leech Fam-
ily are combined upon the form of the disks by
which they attach themselves, upon the number
and arrangement of their eyes, upon the struc-
ture of the hard parts with which the mouth is
armed, etc. Among Cephalopods, the Family of
Squids contains several Genera distinguished by
the structure of the solid shield within the skin
of the back, by the form and connection of their
fins, by the structure of the suckers with which
their arms are provided, by the form of their
beak, etc. In every Class, we find throughout
the Animal Kingdom that there is no sound basis
for *the discrimination of Genera except the de-
tails of their structure ; but in order to define
them accurately an extensive comparison of them
is indispensable, and in characterizing them only
such features should be enumerated as are truly
generic ; whereas, in the present superficial meth-
od of describing genera, features are frequently
introduced which belong not only to the whole
Family, but even to the whole Class which in-
cludes them.

134 SPECIES AND BREEDS.

CHAPTER X.

SPECIES AND BREEDS.

THERE remains biit one more division of the
Animal Kingdom for our consideration, the most
limited of all in its circumscription, — that of
Species. It is with the study of this kind of
group that naturalists generally begin their inves-
tigations. I believe, however, that the study of
Species as the basis of a scientific education is a
great mistake. It leads us to overrate the value of
Species, and to believe that they exist in Nature
in some different sense from the other groups ; as
if there were something more real and tangible in
Species than in Genera, Families, Orders, Classes,
or Branches. The truth is, that to study a vast
number of Species without tracing the principles
that combine them under more comprehensive
groups is only to burden the mind with discon-
nected facts, and more may be learned by a faith-
ful and careful comparison of a few Species than
by a more cursory examination of a greater
number. When one considers the immense
number of Species already known, naturalists

SPECIES AND BREEDS. 135

might well despair of becoming acquainted with
them all, were they not constructed on a few
fundamental patterns, so that the study of one
Species teaches us a great deal for all the rest.
De Candolle, who was at the same time a great bot-
anist and a great teacher, told me once that he
could undertake to illustrate the fundamental
principles of his science with the aid of a dozen
plants judiciously selected, and that it was his
unvarying practice to induce students to make a
thorough study of a few minor groups of plants,
in all their relations to one another, rather than
to attempt to gain a superficial acquaintance with
a large number of species. The powerful influ-
ence he has had upon the progress of Botany
vouches for the correctness of his views. Indeed,
every profound scholar knows that sound learn-
ing can be attained only by this method, and the
study of Nature makes no exception to the rule.
I would therefore advise every student to select
a few representatives from all the Classes, and to
study these not only with reference to their spe-
cific characters, but as members also of a Genus,
of a Family, of an Order, of a Class, and of a
Branch. He will soon convince himself that
Species have no more definite and real existence
in Nature than all the other divisions of the An-
imal Kingdom, and that every animal is the rep-
resentative of its Branch, Class, Order, Family,

136 SPECIES AND BREEDS.

and Genus as much as of its Species. Specific
characters are only those determining size, pro-
portion, color, habits, and relations to surround-
ing circumstances and external objects. How
superficial, then, must be any one's knowledge of
an animal who studies it only with relation to its
specific characters ! He will know nothing of the
finish of special parts of the body, — nothing of
the relations between its form and its structure,

— nothing of the relative complication of its or-
ganization as compared with other allied animals,

— nothing of the general mode of execution of
its structure, — nothing of the general plan of
structure expressed in that mode of execution.
Yet, with the exception of the ordinal charac-
ters, which, since they imply relative superiority
and inferiority, require, of- course, a number of
specimens for comparison, his one animal would
tell him all this as well as the specific characters.

All the more comprehensive groups, equally
with Species, are based upon a positive, perma-
nent, specific principle, maintained generation
after generation with all its essential characteris-
tics. Individuals are the transient representa-
tives of all these organic principles, which cer-
tainly have an independent, immaterial existence,
since they outlive the individuals that embody
them, and are no less real after the generation
that has represented them for a time has passed
away, than they were before.

SPECIES AND BREEDS. 137

From a comparison of a number of well-known
Species belonging to a natural Genus, it is not
difficult to ascertain what are essentially specific
characters. . There is hardly among Mammalia a
more natural Genus than that which includes the
Rabbits and Hares, or that to which the Rats and
Mice are referred. Let us see how the different
Species differ from one another. Though we
give two names in the vernacular to the Genus
Hare, both Hares and Rabbits agree in all the
structural peculiarities constituting a Genus ;
but the different Species are distinguished by
their absolute size when full-grown, — by the na-
ture and color of their fur, — by the size and
form of the ear, — by the relative length of their
legs and tail, — by the more or less slender build
of their whole body, — by their habits, some liv-
ing in open grounds, others among the bushes,
others in swamps, others burrowing under the
earth, — by the number of young they bring
forth, — by their different seasons of breeding, —
and by still minor differences, such as the perma-
nent color of the hair throughout the year in
some, while in others it turns white in winter.
The Rats and Mice differ in a similar way : there
being large and small Species, — some gray, some
brown, others rust-colored, — some with soft,
others with coarse hair ; they differ also in the
length of the tail, and in having it more or less

138 SPECIES AND BREEDS.

covered with hair, — in the cut of the ears, and
their size, — in the length of their limbs, which
are slender and long in some, short and thick in
others, — in their various ways of living, — in the
different substances on which they feed, — and
also in their distribution over the surface of the
earth, whether circumscribed within certain lim-
ited areas or scattered over a wider range.

What is now the nature of these differences by
which we distinguish Species ? They are totally
distinct from any of the categories on which Gen-
era, Families, Orders, Classes, or Branches are
founded, and may readily be reduced to a few
heads. They are differences in the proportion of
the parts and in the absolute size of the whole
animal, in the color and general ornamentation
of the surface of the body, and in the relations
of the individuals to one another and to the
world around. A farther analysis of other Gen-
era would show us that among Birds, Reptiles,
Fishes, and, in fact, throughout the Animal King-
dom, Species of well-defined natural Genera dif-
fer in the same way. We are therefore justified
in saying that the category of characters on
which Species are based implies no structural
differences, but presents the same structure com-
bined under certain minor differences of size,
proportion, and habits. All the specific characters
stand in direct reference to the generic structure,

SPECIES AND BREEDS. 139

the family form, the ordinal complication of
structure, the mode of execution of the Class,
and the plan of structure of the Branch, all of
which are embodied in the frame of each individ-
ual in each Species, even though all these indi-
viduals are constantly reproducing others and
dying away ; so that the specific characters have
no more permanency in the individuals than
those which characterize the Genus, the Family,
the Order, the Class, and the Branch. I believe,
therefore, that naturalists have been entirely
wrong in considering the more comprehensive
groups to be theoretical, and in a measure arbi-
trary,— that is, an attempt of certain men to
classify the Animal Kingdom according to their
individual views, — while they have ascribed to
Species, as contrasted with the other divisions, a
more positive existence in Nature.

No further argument is needed to show that it
is not only the Species that lives in the individ-
ual, but that every individual, though belonging
to a distinct Species, is built upon a precise and
definite plan which characterizes its Branch, —
that that plan is executed in each individual in a
particular way which characterizes its Class, —
that every individual with its kindred occupies a
definite position in a series of structural compli-
cations which characterizes its Order, — that in
every individual all these structural features are

140 SPECIES AND BREEDS.

combined under a definite pattern of form which
characterizes its Family, — that every individual
exhibits structural details in the finish of its parts
which characterize its Genus, — and finally that
every individual presents certain peculiarities in
the proportion of its parts, in its color, in its size,
in its relations to its fellow-beings and the sur-
rounding objects, which constitute its specific
characters ; and all this is repeated in the same
kind of combination, generation after generation,
while the individuals themselves die. If we ac-
cept these propositions, which seem to me self-
evident, it is impossible to avoid the conclusion
that Species do not exist in Nature in any other
sense than the more comprehensive groups of the
zoological system.

There is one question respecting Species that
gives rise to very earnest discussions in our day,
not only among naturalists, but among all
thinking people. How far are they permanent,
and how far mutable ? With reference to the
permanence of Species, there is much to be
learned from the geological phenomena belong-
ing to our own period, in as far as they bear
witness to the invariability of types during hun-
dreds of thousands of years at least. I hope to
present a part of this evidence in a future article
upon Coral Reefs, but in the mean time I cannot
leave this subject without touching upon a point

SPECIES AND BREEDS. 141

which has been urged with great persistency in
recent discussions. I refer to the variability of
Species as shown in domestication.

The domesticated animals with their numer-
ous breeds are constantly adduced as evidence
of the changes which animals may undergo, and
as furnishing hints respecting the way in which
the diversity now observed among animals may
have been produced. It is my conviction that
such inferences are in no way sustained by the
facts of the case, and that, however striking the
differences may be between the breeds of our
domesticated animals, as compared with the wild
Species of the same Genus, they are of a peculiar
character, entirely distinct from the features pre-
vailing among the latter, and altogether incident
to the circumstances under which they appear.
By this I do not mean the natural action of phys-
ical conditions, but the more or less intelligent
direction of the circumstances under which they
live. The inference drawn from the varieties in-
troduced among animals in a state of domestica-
tion, with reference to the origin of Species, is
usually this : that what the farmer does on a
small scale Nature may do on a large one. It is
true that man has been able to produce certain
changes in the animals under his care, and that
these changes have resulted in a variety of breeds.
But in doing this, he has, in my estimation, in

142 SPECIES AND BREEDS.

no way altered the character of the Species, but
only developed its pliability under the will of man,
that is, under a power similar in its nature and
mode of action to that power to which animals owe
their very existence. The influence of man up-
on animals is, in other words, the action of mind
upon them ; and yet the ordinary mode of argu-
ing upon this subject is, that, because the intelli-
gence of man has been able to produce certain
varieties in domesticated animals, therefore phys-
ical causes have produced all the diversity exist-
ing among wild ones. Surely, the sounder logic
would be to infer, that, because our finite intel-
ligence may cause the original pattern to vary
by some slight shades of difference, therefore a
superior intelligence must have established all the
boundless diversity of which our boasted varieties
are but the faintest echo. It is the most intelli-
gent farmer who has the greatest success in im-
proving his breeds ; and if the animals he has so
fostered are left to themselves without that intel-
ligent care, they return to their normal condition.
So with plants : the shrewd, observing, thought-
ful gardener will obtain many varieties from his
flowers ; but those varieties will fade out, if left
to themselves. There is, as it were, a certain
degree of pliability and docility in the organiza-
tion both of animals1 and plants, which may be
developed by the fostering care of man, and with-

SPECIES AND BREEDS. 143

in which he can exercise a certain influence ; but
the variations thus produced are of a peculiar
kind, and do not correspond to the differences
of the wild Species. Let us take some examples
to illustrate this assertion.

Every Species of wild Bull differs from the
others in its size ; but all the individuals corre-
spond to the average standard of size characteris-
tic of their respective Species, and show none of
those extreme differences of size so remarkable
among our domestic Cattle. Every Species of wild
Bull has its peculiar color, and all the individuals
of one Species share in it : not so with our do-
mesticated Cattle, among which every individual
may differ in color from every other. All the in-
dividuals of the same Species of wild Bull agree
in the proportion of their parts, in the mode of
growth of the hair, in its quality, whether fine or
soft : not so with our "domesticated Cattle, among
which we find in the same Species overgrown
and dwarfish individuals, those with long and
short legs, with slender and stout build of the
body, with horns or without, as well as the great-
est variety in the mode of twisting the horns, —
in short, the widest extremes of development
which the degree of pliability in that Species
will allow.

A curious instance of the power of man, not
only in developing the pliability of an animal's

144 SPECIES AND BREEDS.

organization, but in adapting it to suit his own
caprices, is that of the Golden Carp, so frequently
seen in bowls and tanks as the ornament of draw-
ing-rooms and gardens. Not only an infinite
variety of spotted, striped, variegated colors has
been produced in these Fishes, but, especially
among the Chinese, so famous for their morbid
love of whatever is distorted and warped from its
natural shape and appearance, all sorts of changes
have been brought about in this single Species.
A book of Chinese paintings, showing the Golden
Carp in its varieties, represents some as short and
stout, others long and slender, — some with the
ventral side swollen, others hunchbacked, — some
with the mouth greatly enlarged, while in others
the caudal fin, which, in the normal condition
of the Species, is placed vertically at the end of
the tail, and is forked like those of other Fishes,
has become crested and arched, or is double or
crooked, or has swerved in some other way from
its original pattern. But, in all these variations,
there is nothing which recalls the characteristic
specific differences among the representatives of
the Carp Family, which, in their wild state, are
very monotonous in their appearance all the
world over.

Were it appropriate to accumulate evidence
here upon this subject, I could bring forward
many more examples quite as striking as those

SPECIES AND BREEDS. 145

above mentioned. The various breeds of our
domesticated Horses present the same kind of
irregularities, and do not differ from each other
in the same way as the wild Species differ from
one another. Or take the Genus Dog : the differ-
ences between its wild Species do not correspond
in the least with the differences observed among
the domesticated ones. Compare the differences
between the various kinds of Jackals and Wolves
with those that exist between the Bull-Dog and
Greyhound, for instance, or between the St.
Charles and the Terrier, or between the Esqui-
maux and the Newfoundland Dog. I need
hardly add, that what is true of the Horses,
the Cattle, the Dogs, is true also of the Donkey,
the Goat, the Sheep, the Pig, the Cat, the Rabbit,
the different kinds of barn-yard fowl, — in short,
of all those animals that are in domesticity the
chosen companions of man.-

In fact, all the variability among domesticated
Species is due to the fostering care, or, in its
more extravagant freaks, to the fancies of man ;
and it has never been observed in the wild Species,
where, on the contrary, everything shows the
closest adherence to the distinct, well-defined,
and invariable limits of the Species. It surely
does not follow, that, because the Chinese can,
under abnormal conditions, produce a variety of
fantastic shapes in the Golden Carp, therefore

7

146 SPECIES AND BREEDS.

water, or the physical conditions established in
the water, can create a Fish, any more than it
follows, that, because they can dwarf a tree, or
alter its aspect, by stunting its growth in one
direction, and forcing it in another, therefore the
earth, or the physical conditions connected with
their growth, can create a Pine, an Oak, a Birch,
or a Maple.

I confess that, in all the arguments derived
from the phenomena of domestication, to prove
that animals owe their origin and diversity to the
natural action of the conditions under which they
live, the conclusion does not seem to me to follow
logically from the premises. And the fact that
the domesticated animals of all the races of men,
equally with the white race, vary among them-
selves in the same way, and differ in the same
way from the wild Species, makes it still more
evident, that domesticated varieties do not ex-
plain the origin of Species, except, as I have -said,
by showing, that the intelligent will of man can
produce effects which physical causes have never
been known to produce, and that we must, there-
fore, look to some cause outside of Nature, cor-
responding in kind to the intelligence of man,
though so different in degree, for all the phe-
nomena connected with the existence of animals
in their wild state.

So far from attributing these original differ-

SPECIES AND BREEDS. 147

ences among animals to natural influences, it
would seem, that, while a certain freedom of
development is left, within the limits of which
man can exercise his intelligence and his inge-
nuity, not even this superficial influence is allowed
to physical conditions unaided by some guiding
power, since, in their normal state, the wild Species
remain, so far as we have been able to discover,
entirely unchanged, — maintained, it is true, in
their integrity by the circumstances established for
their support, but never altered by them. Nature
holds inviolable the stamp that God has set upon
his creatures ; and if man is able> to influence
their organization in some slight degree, it is
because the Creator has given to his relations
with the animals he has intended for his com-
panions the same plasticity which he has allowed
to every other side of his life, in virtue of which
he may in some sort mould and shape it to his
own ends, and be held responsible also for its
results.

The common sense of a civilized community
has already pointed out the true distinction, in
applying another word to the discrimination of
the different kinds of domesticated animals.
They are called Breeds, and Breeds among ani-
mals are the work of man : Species were created
by God.

148 FORMATION OF CORAL REEFS.

CHAPTER XI.

FORMATION OF CORAL REEFS.

AMONG the astounding discoveries of modern
science is that of the immense periods which
have passed in the gradual formation of our
earth. So vast were the cycles of tirne preceding
even the appearance of man on the surface of
our globe, that our own period seems as yester-
day when compared with the epochs that have
gone before it. Had we only the evidence of the
deposits of rock heaped above each other in regu-
lar strata by the slow accumulation of mate-
rials, they alone would convince us of the long
and slow maturing of God's work on the earth ;
but when we add to these the successive popu-
lations of whose life this world has been the
theatre, and whose remains are hidden in the
rocks into which the mud or sand or soil of what-
ever kind on which they lived has hardened in
the course of time, — or the enormous chains of
mountains whose upheaval divided these periods
of quiet accumulation by great convulsions, —
or the changes of a different nature in the con-

FORMATION OF CORAL REEFS. 149

figuration of our globe, as the sinking of lands
beneath the ocean, or the gradual rising of con-1
tincnts and islands above it, — or the wearing of
great river-beds, or the filling of extensive water-
basins, till marshes first and then dry land suc-
ceeded to inland seas,— -or the slow growth of
coral reefs, those wonderful sea-walls raised by
the little ocean-architects whose own bodies fur-
nish both the building-stones and the cement
that binds them together, and who have worked
so busily during the long centuries, that there
are extensive countries, mountain-chains, islands,
and long lines of coast consisting solely of their
remains, — or the countless forests that must
have grown up, flourished, died, and decayed,
to fill the storehouses of coal that feed the fires
of the human race to-day, — if we consider all
these records of the past, the intellect fails to
grasp a chronology for which our experience
furnishes no data, and the time that lies behind
us seems as much an eternity to our conception
as the unknown future that stretches indefinitely
before us.

The physical as well as the human history of
the world has its mythical age, lying dim and
vague in the morning mists of creation, like that
of the heroes and demigods in the early tra-
ditions of man, defying all our ordinary dates
and measures. But if the succession of periods

150 FORMATION OF CORAL REEFS.

that prepared the earth for the coming of man,
and the animals and plants that accompany him
on earth, baffles our finite attempts to estimate
its duration, have we any means of determining
even approximately the length of the period to
which we ourselves belong? If so, it may fur-
nish us with some data for the further solution
of these wonderful mysteries of time, and it is
besides of especial importance with reference to
the question of permanence of Species.

Those who maintain the mutability of Species,
and account for all the variety of life on earth
by the gradual changes wrought by time and
circumstances, do not accept historical evidence
as affecting the question at all. The relics of
those oldest nations, all whose history is pro-
served in monumental records, do not indicate
the slightest variation of organic types from the
earliest epoch to this day. The. animals pre-
served within their tombs or carved upon the
walls of their monuments by the ancient Egyp-
tians were the same as those that have their
home in the valley of the Nile to-day ; the
negro, whose peculiar features are unmistaka-
ble even in their rude artistic attempts to rep-
resent them, was the same woolly-haired, thick-
lipped, flat-nosed, dark-skinned being in the
days of the Rameses that he is now. The
Apis, the Ibis, the Crocodiles, the sacred Beetles,

FORMATION OF CORAL REEFS. 151

have brought down to us unchanged all the char-
,acters that superstition hallowed in those early
days. The stony face of the Sphinx is not more
true to its past, nor the massive architecture
of the Pyramids more unchanged, than they are.
But the advocates of the mutability of Species
say truly enough that the most ancient traditions
are but as yesterday in the world's history, and
that what six thousand years could not do sixty
thousand years might effect. Leaving aside, then,
all historical chronology, how far back can we
trace our own geological period, and the Species
belonging to it ? By what means can we deter-
mine its duration ? Within what limits, by what
standard, may it be measured ? Shall hundreds,
or thousands, or hundreds of thousands, or mil-
lions of years be the unit from which we start ?

I will begin this inquiry with a series of facts
which I myself have had an opportunity of in-
vestigating with especial care respecting the for-
mation and growth of the Coral Reefs of Florida.
But first a few words on Coral Reefs in general.
They are living limestone walls built up from
certain depths in the ocean by the natural growth
of a variety of animals, but limited by the level
of high water, beyond which they cannot rise,
since the little beings that compose them die as
soon as they are removed from the vitalizing
influence of the pure sea-water. These walls

152 FORMATION OF CORAL REEFS.

have a variety of outlines : they may be straight,
circular, semicircular, or oblong, according to the
form of the coast along which the little Reef-
Builders establish themselves ; and their height
is, of course, determined by the depth of the
bottom on which they cest. If they settle about
an island on all sides of which the conditions for
their growth are equally favorable, they will raise
a wall all round it, thus encircling it with a ring
of Coral growth. The Athols in the Pacific
Ocean, those circular islands enclosing sometimes
a fresh-water lake in mid-ocean, are Coral walls
of this kind, that have formed a ring around a
central island.

This is easily understood, if we remember that
the bottom of the Pacific Ocean is by no means
a stable foundation for such a structure. On
the contrary, over a certain area, already sur-
veyed with some accuracy by Professor Dana,
during the United States Exploring Expedition,
it is subsiding ; and if an island upon which
the Reef-Builders have established themselves

FORMATION OF CORAL REEFS. 153

be situated in that area of subsidence, it will,
of course, sink with the floor on which it rests,
carrying down also the Coral wall to a greater
depth in the sea. In such instances, if the rate

./^v

IMiwPP^ ^llillllTOlflllllllllll

of subsidence be more rapid than the rate of
growth in the Corals, the island and the wall
itself will disappear beneath the ocean. But
whenever, on the contrary, the rate of increase
in the wall is greater than that of subsidence in
the island, while the latter gradually sinks below
the surface, the former rises in proportion, and
by the time it has completed its growth the cen-
tral island has vanished, and there remains only
a ring of Coral Reef, with here and there a
break perhaps, at some spot where the more
prosperous growth of the Corals has been checked.

pH^^

If, however, as sometimes happens, there is no
such break, and the wall is perfectly uninter-
rupted, the sheet of sea-water so enclosed may
be changed to fresh water by the rains that are
poured into it. Such a water-basin will remain

7*

154 FORMATION OF CORAL REEFS.

salt, it is true, in its lower part, and the fact that
it is affected by the rise and fall of the tides
shows that it is not entirely secluded from com-
munication with the ocean outside ; but the salt
water, being heavier, sinks, while the lighter
rain-water remains above, and it is to all appear-
ance actually changed into a fresh-water lake.

I need not dwell here on the further history
of such a Coral island, or follow it through the
changes by which the summit of its circular wall
becomes covered with a fertile soil, a tropical
vegetation springs up upon it, and it is at last
perhaps inhabited by man. There is something
very attractive in the idea of these green rings
enclosing sheltered harbors and quiet lakes in
mid-ocean, and the subject has lost none of its
fascination since the mystery of their existence
has been solved by the investigations of several
contemporary naturalists, who have enabled us to
trace the whole story of their structure. I would
refer all who wish for a more detailed account
of them to Charles Darwin's charming little vol-
ume on " Coral Reefs," where their mode of
formation is fully described, and also to James
D. Dana's " Geological Report of the United
States Exploring Expedition."

Coral Reefs are found only in tropical regions :
although Polyps, animals of the same class as
those chiefly instrumental in their formation, are

FORMATION OF CORAL REEFS. 155

found in all parts of the globe, yet the Reef-
Building Polyps are limited to the Tropics. We
are too apt to forget that the homes of animals
are as definitely limited in the water as on the
land. Indeed, the subject of the geographical
distribution of animals according to laws regu-
lated by altitude, by latitude and longitude, by
pressure of atmosphere or pressure of water, by
temperature, light, &c., already alluded to in a
previous article, is exceedingly interesting, and
presents a most important field of investigation.
The climatic effect of different levels of al-
titude upon the growth of animals and plants
is the same as that of different degrees of lati-
tude ; and the slope of a high mountain in the
Tropics, from base to summit, presents in a
condensed form, an epitome, as it were, of the
same kind of gradation in vegetable growth that
may be observed from the Tropics to the Arctics.
At the base of such a mountain we have all the
luxuriance of growth characteristic of the tropi-
cal forest, — the Palms, the Bananas, the Bread-
trees, the Mimosas ; higher up, these give way
to a different kind of growth, corresponding to
our Oaks, Chestnuts, Maples, etc. ; as these wane,
on the loftier slopes comes m the Pine forest,
fading gradually, as it ascends, into a dwarfish
growth of the same kind ; and this at last gives
way to the low creeping Mosses and Lichen? of

156 FORMATION OF CORAL REEFS.

the greater heights, till even these find a foot-
hold no longer, and the summit of the moun-
tain is clothed in perpetual snow and ice. What
have we here but the same series of changes
through which we pass, if, travelling northward
from the Tropics, we leave Palms and Pome-
granates and Bananas behind, where the Live-
Oaks and Cypresses, the Orange-trees and Myrtles
of the warmer Temperate Zone come in, and
these die out as we reach the Oaks, Chestnuts,
Maples, Elms, Nut-trees, Beeches, and Birches
of the colder Temperate Zone, these again waning
as we enter the Pine forests of the Arctic bor-
ders, till, passing out of these, nothing but a
dwarf vegetation, a carpet of Moss and Lichen,
fit food for the Reindeer and the Esquimaux,
greets us, and beyond that lies the region of
the snow and ice fields, impenetrable to all but
the daring Arctic voyager?

I have thus far spoken of the changes in the veg-
etable growth alone as influenced by altitude and
latitude, but the same is equally true of animals.
Every zone of the earth's surface has its own
animals, suited to the conditions under which
they are meant to live ; and, with the exception of
those that accompany man in all his pilgrimages,
and are subject to the same modifying influences
by which he adapts his home and himself to
all climates, animals are absolutely bound by

FORMATION OF CORAL REEFS. 157

the laws of their nature within the range assigned
to them. Nor is this the case only on land,
where river-banks, lake shores, and mountain-
ranges might be supposed to form the impassa-
ble boundaries that keep animals within certain
limits ; but the ocean, as well as the land, has its
faunae and florae bound within their respective
zoological and botanical provinces ; and a wall of
granite is not more impassable to a marine ani-
mal than that ocean-line, fluid, and flowing, and
ever-changing though it be, on which is written
for him, " Hitherto shalt thou come, but no far-
ther." One word as to the effect of pressure on
animals will explain this.

We all live under the pressure of the atmos-
phere. Now, thirty-two feet under the sea dou-
bles that pressure, since a column of water of
that height is equal in weight to the pressure
of one atmosphere. At the depth of thirty-two
feet, then, any marine animal is under the press-
ure of two atmospheres, — that of the air, which
surrounds our globe, and of a weight of water
equal to it ; at sixty-four feet he is under the
pressure of three atmospheres, and so on, — the
weight of one atmosphere being always added
for every thirty-two feet of depth. There is a
great difference in the sensitiveness of animals to
this pressure. Some fishes live at a great depth,
and find the weight of water genial to them ;

158 FORMATION OF CORAL REEFS.

while others would be killed at once by the same
pressure ; and the latter naturally seek the shal-
low waters. Every fisherman knows that he
must throw a long line for a Halibut, while with
a common fishing-rod he will catch plenty of
Perch from the rocks near the shore ; and the
differently colored bands of sea-weed revealed
by low tides, from the green line of the Ulvas
through the brown zone of the common Fucus,
to the rosy and purple-hued sea-weeds of the
deeper water, show that the florae as well as the
faunae of the ocean have their precise boun-
daries.

This wider or narrower range of marine ani-
mals is in direct relation to their structure, which
enables them to bear a greater or less pressure of
water. All fishes, and, indeed, all animals hav-
ing a wide range of distribution in ocean-depths,
have a special apparatus of water-pores, so that
the surrounding element penetrates their struc-
ture, thus equalizing the pressure of the weight,
which is diminished from without in proportion
to the quantity of water they can admit into their
bodies. Marine animals differ in their ability to
sustain this pressure, just as land animals differ
in their power of enduring great variations of
climate and of atmospheric pressure.

Of all air-breathing animals, none exhibits a
more surprising power of adapting itself to great

FORMATION OF CORAL REEFS. 159

and rapid changes of external influences than the
Condor. It may be seen feeding on the sea-shore
under a burning tropical sun, and then, rising
from its repast, it floats up among the highest
summits of the Andes, and is lost to sight beyond
them, miles above the line of perpetual snow,
whore the temperature must be lower than that
of the Arctics. But everr the Condor, sweeping
at one flight from tropic heat to arctic cold,
although it passes through greater changes of
temperature, does not undergo such changes of
' pressure as a fish that rises from a depth of sixty-
four feet to the surface of the sea ; for the former
remains within the air that surrounds our globe,
and therefore the increase or diminution of press-
ure to which it is subjected must be confined
within, the limits of one atmosphere ; while the
latter, at a depth of sixty-four feet, is under a
weight equal to that of three such atmospheres,
which is reduced to one when it reaches the sea-
level. The change is proportionally greater for
those fishes that come from a depth of several
hundred feet. These laws of limitation in space
explain many facts in the growth of Coral Keefs
that would be otherwise inexplicable, and which I
now will endeavor to make clear to my readers.

For a long time it was supposed that the Reef-
Builders inhabited very deep waters, for they were
sometimes brought up on sounding-lines from a

160 FORMATION OF CORAL REEFS.

depth of many hundreds, or even thousands, of
feet, and it was taken for granted that they must
have had' their home where they were found;
but the facts recently ascertained respecting the
subsidence of ocean-bottoms have shown that the
foundation of a Coral wall may have sunk far
below the place where it was laid. And it is now
proved, beyond a doubt, that no Reef-Building
Coral can thrive at a depth of more than fifteen
fathoms, though Corals of other kinds occur far
lower, and that the dead Reef-Corals, sometimes
brought to the surface from much greater depths,
are only broken fragments of some Reef that has
subsided with the bottom on which it was grow-
ing. But though fifteen fathoms is the maximum
depth at which any Reef-Builder can prosper,
there are many which will not sustain even that
degree of pressure ; and this fact has, as we shall
see, an important influence on the structure of
the Reef.

Imagine now a sloping shore on some tropical
coast descending gradually below the surface of
the sea. Upon that slope, at a depth of from ten
to twelve or fifteen fathoms, and two or three or
more miles from the main land, according to the
shelving of the shore, we will suppose that one of
those little Coral animals, to whom a home in
such deep waters is genial, has established itself.
How it happens that such a being, which we

FORMATION OF CORAL REEFS. 161

know is immovably attached to the ground, and
forms the foundation of a solid wall, was ever
able to swim freely about in the water till it
found a suitable resting-place, I shall explain
hereafter, when I say something of the mode of
reproduction of these animals. Accept, for the
moment, my unsustained assertion, and plant
our little Coral on this sloping shore, some twelve
or fifteen fathoms below the surface of the sea.

The internal structure of such a Coral corre-
sponds to that of the Sea- Anemone. The body is
divided by vertical partitions from top to bottom,
leaving open chambers between ; while in the
centre hangs the digestive cavity, connected by
an opening in the bottom with all these cham-
bers. At the top is an aperture serving as a
mouth, surrounded by a wreath of hollow tenta-
cles, each one of which connects at its base with
one of the chambers, so that all parts of the ani-
mal communicate freely with each other. But
though the structure of the Coral is identical in
all its parts with that of the Sea-Anemone, it
nevertheless presents one important difference.
The body of the Sea-Anemone is soft, while
that of the Coral is hard.

It is well known that all animals and plants
have the power of appropriating to themselves
and assimilating the materials they need, each
selecting from the surrounding elements whatever

162 FORMATION OF CORAL REEFS

contributes to its well-being. Now Corals possess,
in an extraordinary degree, the power of assimi-
lating to themselves the lime contained in the salt
water around them; and as soon as our little
Coral is established on a firm foundation, a lime
deposit begins to form in all the walls of its body,
so that its base, its partitions, and its outer wall,
which in the Sea- Anemone remain always soft,
become perfectly solid in the Polyp Coral, and
form a frame as hard as bone.

It may naturally be asked where the lime
comes from in the sea which the Corals absorb in
such quantities. As far as the living Corals are
concerned, the answer is easy, for an immense
deal of lime is brought down to the ocean by
rivers that wear away the lime deposits through
which they pass. The Mississippi, whose course
lies through extensive lime regions, brings down
yearly lime enough to supply all the animals liv-
ing in the Gulf of Mexico. But behind this lies
a question not so easily settled, as to the origin of
the extensive deposits of limestone found at the
very beginning of life upon earth. This problem
brings us to the threshold of astronomy, for the
base of limestone is metallic in character, sus
ceptible therefore of fusion, and may have formed
a part of the materials of our earth, even in an
incandescent state, when the worlds were forming.
But though this investigation as to the origin of

FORMATION OF CORAL REEFS. 163

lime does not belong either to the naturalist or
the geologist, its suggestion reminds us that the
time has come when all the sciences and their
results are so intimately connected that no one
can be carried on independently of the others.
Since the study of the rocks has revealed a
crowded life whose records are hoarded within
them, the work of the geologist and the natural-
ist has become one and the same, and at that
border-land where the first crust of the earth was
condensed out of the igneous mass of materials
which formed its earliest condition, their investi-
gation mingles with that of the astronomer, and
we cannot trace the limestone in a little Coral
without going back to the creation of our solar
system, when the worlds that compose it were
thrown off from a central mass in a gaseous
condition.

When the Coral has become in this way per-
meated with lime, all parts of the body are
rigid, with the exception of the upper margin,
the stomach, and the tentacles. The tentacles
are soft and waving, projected or drawn in at
will ; they retain their flexible character through
life, and decompose when the animal dies. For
this reason the dried specimens of Corals preserved
in museums do not give us the least idea of the
living Corals, in which every one of the millions
of beings composing such a community is crowned

164 FORMATION OF CORAL REEFS.

by a waving wreath of white or green or rose-
colored tentacles.

As soon as the little Coral is fairly established
and solidly attached to the ground, it begins to
bud. This may take place in a variety of ways,
dividing at the top or budding from the base or
from the sides, till the primitive animal is sur-
rounded by a number of individuals like itself,
of which it forms the nucleus, and which now
begin to bud in their turn, each one surrounding
itself with a numerous progeny, all remaining,
however, attached to the parent. Such a com-
munity increases till its individuals are numbered
by millions ; and I have myself counted no less
than fourteen millions of individuals in a Coral
mass of Porites measuring not more than twelve
feet in diameter. The so-called Coral heads,

which make the foundation of a Coral wall, and
seem by their massive character and regular form

FORMATION OF CORAL REEFS. 165

especially adapted to give a strong, solid base to
the whole structure, are known in our classifica-
tions as the Astraeans, so named on account of
the star-shaped form of the little pits crowded
upon their surface, each one of which marks the
place of a single more or less isolated individual
in such a community.

Thus firmly and strongly is the foundation of
the reef laid by the Astraeans ; but we have seen
that for their prosperous growth they require a
certain depth and pressure of water, and when
they have brought the wall so high that they have
not more than six fathoms of water above them,
this kind of Coral ceases to grow. They have,
however, prepared a fitting surface for different
kinds of Corals that could not live in the depths
from which the Astraeans have come, but find
their genial home nearer the surface ; such a
home being made ready for them by their prede-
cessors, they now establish themselves on the top
of the Coral wall and continue its growth for a
certain time. These are the Meandrinas, or the
so-called Brain-Corals, and the Porites. The Me-
andrinas differ from the Astraeans by their less
compact and definite pits. In the Astraeans the
place occupied by the animal in the community
is marked by a little star-shaped spot, in the cen-
tre of which all the partition-walls meet. But in
the Meandrinas, although all the partitions con-

166

FORMATION OF CORAL REEFS.

verge toward the central opening, as in the As-
traeans, these central openings elongate, run into
each other, and form waving furrows all over
the surface, instead of the small round pits so

characteristic of the Astraeans. The Porites re-
semble the Astraeans, but the pits are smaller,

with fewer partitions and fewer tentacles, and
their whole substance is more porous.

FORMATION OF CORAL REEFS. 167

But these also have their bounds within the

sea: they in their turn reach the limit beyond
which they are forbidden by the laws of their na-

ture to pass, and there they also pause. But the

168 FORMATION OF CORAL REEFS.

Coral wall continues its steady progress ; for
here the lighter kinds set in, — the Madrepores
(p. 167), the Millepores, and a great variety of
Sea-Fans (p. 167, below) and Corallines, and the
reef is crowned at last with a many-colored
shrubbery of low feathery growth. These are
all branching in form, and many of them are
simple calciferous plants, though most of them
are true animals, resembling, however, delicate
Algae more than any marine animals ; but, on
examination of the latter, one finds them to be
covered with myriads of minute dots, each repre-
senting one of the little beings out of which
the whole is built, while nothing of the kind
is seen in Algae.

I would add here one word on the true nature
of the Millepores. long misunderstood by natu-

ralists, because this type throws light not only on
some interesting facts respecting Coral Beefs, es-
pecially the ancient ones, but also because it tells
us something of the early inhabitants of the globe,
and shows us that a class of Radiates supposed
to be. missing in the primitive creation had its
representatives then as now.

FORMATION OF CORAL REEFS. 169

In the diagram of the geological periods intro-
duced in a previous article, I have represented all
the three classes of Radiates, Polyps, Acalephs,
and Echinoderms as present on the first floor of
our globe which was inhabited at all. But it is
only recently that positive proofs have been found
of the existence of Acalephs or Jelly-Fishes, as
they are called, at that early period. Their very
name indicates their delicate structure ; and were
there no remains preserved in the rocks of these
soft, transparent creatures, it would yet be no
evidence that they did not exist. Fragile as they
are, however, they have left here and there some
faint record of themselves, and in the Museum
at Carlsruhe, on a slab from Solenhofen, I have
seen a very perfect outline of one which remains
undescribed to this day. This, however, does
not carry them farther back than the Jurassic
period, and it is only lately that I have satisfied
myself that they not only existed, but were
among the most numerous animals in the first
representation of organic life.

The earliest Corals correspond in certain fea-
tures of their structure to the Millepores. They
differ from them as all early animals differ from
the succeeding ones, every geological period hav-
ing its special set of representatives. But still
they are always true to their class, and have a
certain general correspondence with animals of

S

170 FORMATION OF CORAL REEFS.

like kind that follow them in later periods. In
this sense the Millepores are in our epoch the
representatives of those early Corals, called by
naturalists Tabulata and Rugosa, — distinguished
from the Polyp Corals by the horizontal floors,
waving in some, straight in others, whieh di-
vide the body transversely at successive heights
through its whole length, and also by the absence
of the vertical partitions, extending from top to
bottom of each animal, so characteristic of the
true Polyps.

Notwithstanding these differences, they were
for a long time supposed to be Polyps, and I had
shared in this opinion, till, during the winter of
1857, while pursuing my investigations on the
Coral Reefs of Florida, one of these Millepores
revealed itself to me in its true character of Aca-
leph. It must be remembered that they belong
to the Hydroid group of Acalephs, of which our
common jelly-fishes do not give a correct idea,
it is by their soft parts alone — those parts which
are seen only when these animals are alive and
fully open — that their Acalephian character
can be perceived, and this accounts for their
being so long accepted as Polyps, when studied
in the dry Coral stock. Nothing could exceed
my astonishment when for the first time I saw
such an animal fully expanded, and found it to
be a true Acaleph. It is exceedingly difficult to

FORMATION OF CORAL REEFS. 171

obtain a view of them in this state, for, at any
approach, they draw themselves in, and remain
closed to all investigation. Only once, for a
short hour, I had this opportunity ; during that
time one of these little creatures revealed to me
its whole structure, as if to tell me, once for all,
the story of its existence through all the succes-
sive epochs from the dawn of Creation till now,
and then withdrew. With my most patient
watching, I have never been able to see one of
them open again. But to establish the fact that
one of the Corals represented from the earliest
period, and indeed far more numerous in the
beginning than any other, was in truth no
Polyp, but an Acaleph, the glimpse I had was
all-sufficient. It came out as if to bear witness
of its class, — as if to say, " We, too, were
among the hosts of living beings with which
God first peopled his earth."

With these branching Corals the reef reaches
the level of high-water, beyond which, as I have
said, there can be no further growth, for want of
the action of the fresh sea-water. This depend-
ence upon the vivifying influence of the sea ac-
counts for one unfailing feature in the Coral
walls. They are always abrupt and steep on the
seaward side, but have a gentle slope towards the
land. This is accounted for by the circum-
stance that the Corals on the outer side of the

172 FORMATION OF CORAL REEFS.

reef are in immediate contact with the pure
ocean-water, while by their growth they partially
exclude the inner ones from the same influence,
— the rapid growth of the latter being also im-
peded by any impurity or foreign material washed
away from the neighboring shore and mingling
with the water that fills the channel between the
main-land and the reef. Thus the Coral Reefs,
whether built around an island, or along a straight
line of coast, or concentric to a rounding shore,
are always shelving toward the land, while they
are comparatively abrupt and steep toward the
sea. This should be remembered, for, as we
shall see hereafter, it has an important bearing
on the question of time as illustrated by Coral
Reefs.

I have spoken of the budding of Corals, by
which each one becomes the centre of a cluster ;
but this is not the only way in which they multi-
ply their kind. They give birth to eggs also,
which are carried on the inner edge of their par-
tition-walls, till they drop into the sea, where
they float about, little, soft, transparent, pear*
shaped bodies, as unlike as possible to the rigid
stony structure they are to assume hereafter.
In this condition they are covered with vibratile
cilia or fringes, that are always in rapid, unin-
terrupted motion, and by means of which they
swim about in the water. These little germs of

\ FORMATION OF CORAL REEFS. 173

the Corals, swimming freely about during their
earliest phases of life, continue the growth of
the reef, those that prosper at shallower depths
coming in at the various heights where their pre-
decessors die out ; otherwise it would be impossi-
ble to understand how this variety of building
material, as it were, is introduced wherever it
is needed. This point, formerly a puzzle to
naturalists, has become quite clear since it has
been found that myriads of these little germs
are poured into the water surrounding a reef.
There they swim about till they find a genial
spot on which to establish themselves, when they
become attached to the ground by one end, while
a depression takes place at the opposite end,
which gradually deepens to form the mouth and
inner cavity, while the edges expand to form
the tentacles, and the productive life of the little
Coral begins: it buds from every side, and be-
comes the foundation of a new community.

I should add, that, beside the Polyps and the
Acalephs, Mollusks also have their representa-
tives among the Corals. There is a group of
small Mollusks called Bryozoa, allied to the Clams
by their structure, but excessively minute when
compared to the other members of their class,
which, like the other Corals, harden in conse-
quence of an absorption of solid materials, and
contribute to the formation of the reef. Besides

174 FORMATION OF CORAL REEFS.

these j there are certain plants, limestone Algae,
— Corallines, as they are called, — which have
their share also in the work.

I had intended to give some account of the
Coral Reefs of Florida, and to show what bear-
ing they have upon the question of time and
the permanence of Species ; but this cursory
sketch of Coral Reefs in general has grown to
such dimensions that I must reserve a more
particular account of the Florida Reefs and Keys
for a future article.

AGE OF CORAL REEFS. 175

CHAPTER XII.

AGE OF CORAL REEFS AS SHOWING PERMANENCE OF
SPECIES.

A FEW miles from the southern extremity of
Florida, separated from it by a channel, narrow
at the eastern end, but widening gradually to-
ward the west, and rendered every year more
and more shallow by the accumulation of mate-
rials constantly collecting within it, there lies a
line of islands called the Florida Keys. They
are at different distances from the shore, stretch-
ing gradually seaward in the form of an open
crescent, from Virginia Key and Key Biscayne,
almost adjoining the main-land, to Key West, at
a distance of twelve miles from the coast, which
does not, however, close the series, for sixty miles
farther west stands the group of the Tortugas,
isolated in the Gulf of Mexico. Though they
seem disconnected, these islands are parts of a
submerged Coral Reef, parallel with the shore of
the peninsula and continuous underneath the
water, but visible above the surface at such points
of the summit as have fully completed their
growth.

176

AGE OF CORAL REEFS.

This demands some explanation, since I have
already said that no Coral growth can continue
after it has reached the line of high water. But

Fl.O RIDA,

w

we have not finished the history of a Coral wall,
when we have followed it to the surface of the
ocean. It is true that its normal growth ceases
there, but already a process of partial decay has
begun that insures its further increase. Here,
as elsewhere, destruction and construction go
hand in hand, and the materials broken or

AGE OF CORAL REEFS. 177

worn away from one part of the Beef help to
build it up elsewhere. The Corals forming the
Reef are not the only beings that find their home
there : many other animals — Shells, Worms,
Crabs, Star-Fishes, Sea-Urchins — establish them-
selves upon it, work their way into its interstices,
and seek a shelter in every little hole and cranny
made by the irregularities of its surface. In the
Zoological Museum at Cambridge there are some
large fragments of Coral Reef which give one a
good idea of the populous aspect that such a
Reef would present, could we see it as it actually
exists beneath the water. Some of these frag-
ments consist of a succession of terraces, as it
were, in which are many little miniature caves,
where may still be seen the Shells or Sea-Urchins
which made their snug and sheltered homes in
these recesses of the Reef.

We must not consider the Reef as a solid, mas-
sive structure throughout. The compact kinds of
Corals, giving strength and solidity to the wall,
may be compared to the larger trees in a forest,
giving it shade and density ; but beneath these
larger trees grow all kinds of trailing vines,
ferns, and mosses, wild-flowers, and low shrubs,
filling the spaces between them with a thick un-
derbrush. The Coral Reef also has its under-
brush of the lighter, branching, more brittle
kinds, filling its interstices, and fringing the sum-

8* i,

178 AGE OF CORAL REEFS.

mit and the sides with their delicate, graceful
forms. Such an intricate underbrush of Coral
growth affords an excellent retreat for many
animals that like its protection better than ex-
posure to the open sea, just as many land-animals
prefer the close and shaded woods to the open
plain. A forest is not more thickly peopled with
Birds, Squirrels, Martens, and the like, than is
the Coral Reef with a variety of animals which
do not contribute in any way to its growth, but
find shelter in its crevices, or in its near neigh-
borhood.

But these larger animals are not the only ones
that haunt the forest. There is a host of parasites
besides, principally Insects and their larvae, which
bore their way into the very heart of the tree,
making their home in the bark and pith, and not
the less numerous because hidden from sight.
These also have their counterparts in the Reef,
where numbers of boring Shells and marine
Worms work their way into the solid substance
of the wall, piercing it with holes in every direc-
tion, till large portions become insecure, and the
next storm suffices to break off the fragments so
loosened. Once detached, they are tossed about
in the water, crumbled into Coral sand, crushed,
often ground to powder by the friction of the
rocks and the constant acti9n of the sea.

After a time, an immense quantity of such

AGE OF CORAL REEFS. 179

materials is formed about a Coral Reef. Tides
and storms constantly throw them up on its sur-
face, and at last a soil collects on the top of the
Reef, wherever it has reached the surface of the
water, formed chiefly of its own debris, of Coral
sand, Coral fragments, even large masses of Coral
rock, mingled with the remains of the animals
that have had their home about the Reef, with
sea-weeds, with mud from the neighboring land,
and with the thousand loose substances always
floating about in the vicinity of a coast, and
thrown upon the rocks or shore with every wave
that breaks against them. Add to this the pres-
ence of a lime-cement in the water, resulting
from the decomposition of some of these mate-
rials, and we have all that is needed to make a
very compact deposit and fertile soil, on which a
vegetation may spring up, whenever seeds float-
ing from the shore, or dropped by birds in their
flight, take root on the newly formed island.

There is one plant belonging to tropical or sub-
tropical climates that is peculiarly adapted by its
mode of growth to the soil of these islands, and
contributes greatly to their increase. This is the
Mangrove-tree. Its seeds germinate in the calyx
of the flower, and, before they drop, grow to be
little brown stems, some six or seven inches long,
and about as thick as a finger, with little rootlets
at one end. Such Mangrove-seedlings, looking

180 AGE OF CORAL REEFS.

more like cigars than anything else, float in large
numbers about the Reef. I have sometimes seen
them in the water about the Florida Reef in such
quantities, that one would have said some vessel
laden with Havana cigars had been wrecked
there, and its precious cargo scattered in the
ocean.

In consequence of their shape, and the devel-
opment of the root, one end is a little heavier
than the other, so that they float unevenly, with
the loaded end a little lower than the lighter one.
When they are brought by the tide against such
a cap of soil as I have described, they become
stranded upon it by their heavier end ; the root-
lets attach themselves slightly to the soil ; the
advancing and retreating waves move the little
plant up and down, till it works a hole in Jhe
sand ; and having thus established itself more
firmly, steadied itself, as it were, it now stands
upright ; and, as it grows, throws out numerous
roots, even from a height of several feet above
the ground, till it has surrounded the lower part
of its stem with a close net-work of roots. Against
this natural trellis, or screen, all sorts of mate-
rials collect. Sand, mud, and shells are caught
in it. And as these Mangrove-trees grow in large
numbers, and to the height of thirty feet, they
contribute greatly to the solidity and compact-
ness of the shores on which they are stranded.

AGE OF CORAL REEFS. 181

Such caps of soil on the summit of a Coral
Reef are of course very insecure, till the/ are
consolidated by a long period of accumulation,
and they may even be swept completely away by
a violent storm. It is not many years since the
light-house, built on Sand Key for the greater
security of navigation along the Reef, was swept
away, with the whole island on which it stood.
Thanks to the admirably conducted investigations
of the Coast-Survey, this part of our seaboard,
formerly so dangerous on account of the Coral
Reefs, is now better understood, and every pre-
caution has been taken to insure the safety of
vessels sailing along the coast of Florida.

I cannot deny myself the pleasure of paying a
tribute here to the high scientific character of the
distinguished superintendent of this survey, who
has known so well how to combine the most im-
portant scientific aims with the most valuable
practical results in his direction of it. If some
have hitherto doubted the practical value of such
researches, — and unhappily there are always
those who estimate intellectual efforts only by
their material results, — one would think that
these doubts must be satisfied, now that the
Coast-Survey is seen to be the right arm of our
navy. Most of the leaders in our late naval ex-
peditions have been men trained in its service,
and familiar with all the harbors, with every

182 AGE OF CORAL REEFS.

bay and inlet of our Southern coasts, from hav-
ing been engaged in the extensive researches
undertaken by Dr. Bache, and carried out under
his guidance. Many even of the pilots of our
Southern fleets are men who have been employed
upon this work, and owe their knowledge of the
coast to their former occupation. It is a singular
fact, that at this very time, when the whole coun-
try feels its obligation to the men who have
devoted so many years of their lives to these
investigations, a proposition should have been
brought forward in Congress for the suspension
of the Coast-Survey on economical grounds.
Happily, the almost unanimous rejection of this
proposition has shown the appreciation in which
the work is held by our national legislature.
Even without reference to their practical useful-
ness, it is a sad sign, when, in the hour of her
distress, a nation sacrifices first her intellectual
institutions. Then, more than ever, when she
needs all the culture, all the wisdom, all the
comprehensiveness of her best intellects, should
she foster the institutions that have fostered
them, and in which they have been trained to do
good service to their country in her time of need.
Several of the Florida Keys, such as Key
West and Indian Key, are already large, inhabited
islands, several miles in extent. The interval
between them and the main-land is gradually

AGE OF CORAL REEFS. 183

filling up, by a process similar to that by which
the islands themselves were formed. The gentle
landward slope of the Reef and the channel be-
tween it and the shore, are covered with a growth
of the more branching lighter Corals, such as Sea-
Fans, Corallines, etc., answering the same pur-
pose as the intricate roots of the Mangrove-tree.
All the debris of the Reef, as well as the sand
and mud washed from the shore, collect in this
net-work of Coral growth within the channel,
and soon transform it into a continuous mass,
with a certain degree of consistence and solidity.
This forms the foundation of the mud-flats which
are now rapidly filling the channel, and must
eventually connect the Keys of Florida with the
present shore of the peninsula.

Outside the Keys, but not separated from them
by so great a distance as that which intervenes
between them and the main-land, there stretches
beneath the water another Reef, abrupt, like the
first, on its seaward side, but sloping gently to-
ward the inner Reef, and divided from it by a
channel. This outer Reef and channel are, how-
ever, in a much less advanced state than the
preceding ones. Only here and there a sand-flat
large enough to aiford a foundation for a bea-
con, or a light-house, shows that this Reef also
is gradually coming to the surface, and that a
series of islands corresponding to the Keys must
eventually be formed upon its summit.

184 AGE OF CORAL REEFS.

Some of my readers may ask why the Reef
does not rise evenly to the level of the sea, and
form a continuous line of land, instead of here
and there an island. This is accounted for by
the sensitiveness of the Corals to any unfavorable
circumstances impeding their growth, as well as
by the different rates of increase of their differ-
ent kinds. Wherever any current from the shore
flows over the Reef, bringing with it impurities
from the land, there the growth of the Corals
will be less rapid, and consequently that portion
of the Reef will not reach the surface so soon
as other parts, where no such unfavorable influ-
ences have interrupted the growth. But in the
course of time the outer Reef will reach the
surface for its whole length, and become united
to the inner one by the filling up of the channel
between them, while the inner one will long
before that time become solidly united to the
present shore-bluffs of Florida by the consolida-
tion of the mud-flats, which will one day trans-
form the inner channel into dry land.

What is now the rate of growth of these Coral
Reefs ? We cannot, perhaps, estimate it with
absolute accuracy, since they are now so nearly
completed ; but Coral growth is constantly spring-
ing up wherever it can find a foothold, and it
is not difficult to ascertain approximately the
rate of growth of the different kinds. Even this,

AGE OF CORAL REEFS. 185

however, would give us far too high a standard ;
for the rise of the Coral Reef is not in propor-
tion to the height of the living Corals, but to
their solid parts which never decompose. Add
to this that there are many brittle, delicate kinds
that have a considerable height when alive, but
contribute to the increase of the Reef only so
much additional thickness as their branches
would have if broken and crushed down upon
its surface. A forest in its decay does not add to
the soil of the earth- a thickness corresponding
to the height of its trees, but only such a thin
layer as would be left by the decomposition of
its whole vegetation. In the Coral Reef, also,
we must allow not only for the deduction of the
soft parts, but also for the comminution of all
these little branches, which would be broken
and crushed by the action of the storms and
tides, and add, therefore, but little to the Reef
in proportion to their size when alive.

The foundations of Fort Jefferson, which is
built entirely of Coral rock, were laid on the
Tortugas Islands in the year 1846. A very in-
telligent head-workman watched the growth of
certain Corals that established themselves on
these foundations, and recorded their* rate of
increase. He has shown me the rocks on which
Corals had been growing for some dozen years
during which they had increased vt tha rate ^

186 AGE OF CORAL REEFS.

about half an inch in ten years. I have col-
lected facts from a variety of sources and local-
ities that confirm this testimony. A brick placed
under water, in the year 1850, by Captain Wood-
bury of Tortugas, with the view of determining
the rate of growth of Corals, when taken up
in 1858 had a crust of Maeandrina upon it a little
more than half an inch in thickness. Mr. Allen
also sent me from Key West a number of frag-
ments of Ma3andrma from the breakwater at
Fort Taylor ; they had been growing from twelve
to fifteen years, and have an average thickness
of about an inch. The specimens vary in this
respect, — some of them being a little more than
an inch in thickness, others not more than half
an inch. Fragments of Oculina gathered at the
same place and of the same age are from one
to three inches in height and width; but these
belong to the lighter, more branching kinds of
corals, which, as we have seen, cannot, from their
brittle character, be supposed to add their whole
height to the solid mass of the Coral wall. Mille-
pore gives a similar result.

Estimating the growth of the Coral Reef ac-
cording to these and other data of the same
character, it should be about half a foot in a
century ; and a careful comparison which I have
made of the condition of the Reef as recorded
in an English survey made about a century ago

AGE OF CORAL REEFS. 187

with its present state would justify this conclu-
sion. But, allowing a wide margin for inaccu-
racy of observation or for any circumstances that
might accelerate the growth, and leaving out of
consideration the decay of the soft parts and the
comminution of the brittle ones, which would
subtract so largely from the actual rate of growth,
let us double this estimate and call the average
increase a foot for every century. In so doing,
we are no doubt greatly overrating the rapidity
of the progress, and our calculation of the period
that must have elapsed in the formation of the
Reef will be far within the truth.

The outer Reef, still incomplete, as I have
stated, and therefore of course somewhat lower
than the inner one, measures about seventy feet
in height. Allowing a foot of growth for every
century, not less than seven thousand years must
have elapsed since this Reef began to grow.
Some miles nearer the main-land are the Keys,
or the inner Reef; and though this must have
been longer in the process of formation than the
outer one, since its growth is completed, and
nearly the whole extent of its surface is trans-
formed into islands, with here and there a nar-
row break separating them, yet, in ordfer to keep
fully within the evidence of the facts, I will allow
only seven thousand years for the formation of
this Reef also, making fourteen thousand for
the two.

188 AGE OF CORAL REEFS.

This brings us to the shore-bluffs, consisting
simply of another Reef exactly like those already
described, except that in course of time it has been
united to the main-land by the complete filling up
and consolidation of the channel which once di-
vided it from the extremity of the peninsula, as
a channel now separates the Keys from the shore-
bluffs, and the outer Reef, again, from the Keys.
These three concentric Reefs, then, the outer
Reef, the Keys, and the shore-bluffs, if we meas-
ure the growth of the two latter on the same
low estimate by which I have calculated the rate
of progress of the former, cannot have reached
their present condition in less than twenty thou-
sand years. Their growth must have been suc-
cessive, since, as we have seen, all Corals need
the fresh action of the open sea upon them, and
if either of the outer Reefs had begun to grow
before the completion of the inner one, it would
have effectually checked the growth of the latter.
The absence of an incipient Reef outside of the
outer Reef shows these conclusions to be well
founded. The islands capping these three reefs
do not exceed in height the level to which the
fragments accumulated upon their summits may
have been thrown by the heaviest storms. The
highest hills of this part of Florida are not over
ten or twelve feet above the level of the sea,
and yet the luxuriant vegetation with which they

AGE OF CORAL REEFS. 189

are covered gives them an imposing appear-
ance, recalling the islands of the Pacific.

But this is not the end of the story. Travel-
ling inland from the shore-bluffs, we cross a low,
flat expanse of land, the Indian hunting-ground,
which brings us to a row of elevations called
the Hummocks. This hunting-ground, or Ever-
glade as it is also called, is an old channel,
changed first to mud-flats and then to dry land
by the same kind of accumulation that is filling
up the present channels, and the row of hum-
mocks is but an old Coral Reef with the Keys
or islands of past days upon its summit. Seven
such Reefs and channels of former times have
already been traced between the shore-bluffs and
Lake Okee-cho-bee, adding some fifty thousand
years to our previous estimate. Indeed, upon
the lowest calculation, based upon the facts thus
far ascertained as to their growth, we cannot
suppose that less than seventy thousand years
have elapsed since the Coral Reefs already known
to exist iii Florida began to grow.

When we remember that this is but a small
portion of the peninsula, and that, though we
have no very accurate information as to the
nature of its interior, yet the facts already ascer-
tained in the northern part of the State, formed,
like its southern extremity, of Coral growth, justify
the inference that the whole peninsula is formed

190 AGE OF COFAL REEFS.

of successive concentric Reefs, we must believo
that hundreds of thousands of years have elapsed
since its formation began. Leaving aside, how-
ever, all that part of its history which is not
Fusceptible of positive demonstration in the pres-
ent state of our knowledge, I will limit my re-
sults to the evidence of facts already within our
possession ; and these give us as the lowest pos-
sible estimate a period of seventy thousand years
for the formation of that part of the peninsula
which extends south of Lake Okee-cho-bee to the
present outer Reef.

So much for the duration of the Reefs them-
selves. What, now, do they tell us of the per-
manence of the Species by which they were
formed ? In these seventy thousand years has
there been any change in the Corals living in the
Gulf of Mexico ? I answer most emphatically,
No. Astraeans, Porites, Maeandrinas, and Mad-
repores were represented by exactly the same
Species seventy thousand years ago as they are
now. Were we to classify the Florida Corals
from the Reefs of the interior, the result would
correspond exactly to a classification founded
upon the living Corals of the outer Reef to-day.
There would be among the Astraeans tfye differ-
ent Species of Astraea proper, forming the close
round heads, — the Mussa, growing in smaller
stocks, where the mouths coalesce and run into

AGE OF COBAL BEEFS. 191

each other as in the Brain-Corals, but in which the
depression formed by the mouths are deeper, —
and the Caryophyllians, in which the single in-
dividuals stand out more distinctly from the
stock ; among Porites^ the P. Astraeoides, with
pits resembling those of the Astraeans in form,
though smaller in size, and growing also in solid
heads, though .these masses are covered with
club-shaped protrusions, instead of presenting a
smooth, even surface like the Astraeans, — and
the P. Clavaria, in which the stocks are divided
in short, stumpy branches, with club-shaped ends,
instead of growing in close, compact heads ;
among the Masandrinas we should have the
round heads we know as Brain-Corals, with their
wavy lines over the surface, and the Manicina,
differing again from the preceding by certain de-
tails of structure ; among the Madrepodes we
should have the Madrepora prolifera, with its
small, short branches, broken up by very frequent
ramifications, the M. cervicornis, with longer
and stouter branches and less frequent ramifica-
tions, and the cup-like M. palmata, resembling
an open sponge in form. Every Species, in
short, that lives upon the present Reef is found
in the more ancient ones. They all belong to
our own geological period, and we cannot, upon
the evidence before us, estimate its duration at
less than seventy thousand years, during which

192 AGE OF CORAL REEFS.

time we have no evidence of any change in
Species, but, on the contrary, the strongest proof
of the absolute permanence of those Species
whose past history we have been able to trace.

Before leaving the subject of the Coral Reefs,
I would add a few words on the succession of the
different kinds of Polyp Corals on a Reef as com-
pared with their structural rank and also with
their succession in time, because we have here
another of those correspondences of thought,
those intellectual links in Creation, which give
such coherence and consistency to the whole,
and make it intelligible to man.

The lowest in structure among the Polyps are
not Corals, but the single, soft-bodied Actiniae.
They have no solid parts, and are independent
in their mode of existence, never forming com-
munities, like the higher members of the class.
It might at first seem strange that independence,
considered a sign of superiority in the higher
animals, should here be looked upon as a mark
of inferiority. But independence may mean
either simple isolation, or independence of ac-
tion ; and the life of a single Polyp is no more
independent in the sense of action than that of
a community of Polyps. It is simply not con-
nected witii or related to the life of any others.
The mode of development of these animals tells
us something of the relative inferiority and su-

AGE OF COBAL REEFS. 193

periority of the single ones and of those that
grow in communities. When the little Polyp
Coral, the Astraean or Madrepore, for instance, is
born from the egg, it is as free as the Actinia,
which remains free all its life. It is only at a
later period, as its development goes on, that it
becomes solidly attached to the ground, and be-
gins its compound life by putting forth new
beings like itself as buds from its side. Since
we cannot suppose that the normal development
of any being can have a retrograde action, we
are justified in believing that the loss of freedom
is in fact a stage of progress in these lower
animals, and their more intimate dependence on
each other a sign of maturity.

There are, however, structural features by
which the relative superiority of these animals
may be determined. In proportion as the num-
ber of their parts is limited and permanent, their
structure is more complicated ; arid the indefi-
nite multiplication of identical parts is connected
with -inferiority of structure. Now in these low-
est Polyps, the Actiniae, the tentacles increase
with age indefinitely, never ceasing to grow while
life lasts, new chambers being constantly added
to correspond with them, till it becomes impossi-
ble to count their numbers. Next to these come
the true Fungida3. They are also single, and,
though they are stony Corals, they have no share

194 AGE OF CORAL REEFS.

in the formation of Reefs. In these, alsc, the
tentacles multiply throughouriife, though they
are usually not so numerous as in the Actinia).
But a new feature is added to the complication
of their structure, as compared with Actiniae, in
the transverse beams which connect their vertical
partitions, though they do not stretch across the
9hambers so as to form perfect floors, as in some
of the higher Polyps. These transverse beams or
floors must not be confounded with the horizon-
tal floors alluded to in a former article as char-
acteristic of the ancient Acalephian Corals, the
Rugosa and Tabulata. For in the latter these
floors stretch completely across the body, unin-
terrupted by vertical partitions, which, if they
exist at all, pass only from floor to floor, instead
of extending unbroken through the whole height
of the body, as in all Polyps. Where, on the
contrary, transverse floors exist in true Polyps,
they never cut the vertical partitions in their
length, but simply connect their walls, stretching
wholly or partially from wall to wall.

In the Astraeans, the multiplication of tenta-
cles is more definite and limited, rising some-
times to ninety and more, though often limited to
forty-eight in number, and the transverse floors
between the vertical partitions are more com-
plete than in the Fungida3. The Porites have
twelve tentacles only, never more and never less,

AGE OF CORAL REEFS. 195

and in them the whole solid frame presents a
complicated system of connected beams. The
Madrepores have also twelve tentacles, but they
have a more definite character than those of the
Porites, on account of their regular alternation
in six smaller and six larger ones ; in these also
the transverse floors are perfect, but exceedingly
delicate. Another remarkable feature among the
Madrepores consists in the prominence of one of
the Polyps on the summit of the branches, show-
ing a kind of subordination of the whole com-
munity to these larger individuals, and thus sus-
taining the view expressed above, that the com-
bination of many individuals into a connected
community is among the Polyps a character of
superiority when contrasted with the isolation
of the Actinia3. In the Sea-Fans, the Haley o-
noids, as they are called in our classification,
the number of tentacles is always eight, four
of which are already present at the time of
their birth, arranged in pairs, while the other
four are added later. Their tentacles are lobed
all around the margin, and are much more com-
plicated in structure than those of the preceding
Polyps.

According to the relative complication of their
structure, these animals are classified in the
following order : —

196 AGE OF CORAL REEFS.

STRUCTURAL SERIES.
HALCYONOIDS: eight tentacles in pairs, lobed around the margin,

always combined in large communities, some of which are free

and movable like single animals.
MADREPORES: twelve tentacles, alternating in six larger and six

smaller ones; frequently a larger top animal standing prominent

in the whole community, or on the summit of its branches.
PORITES : twelve tentacles, not alternating in size ; system of con-

nected beams.
ASTR^EANS: tentacles not definitely limited in number, though usu-

ally not exceeding one hundred, and generally much below this

number; transverse floors. Masandrinas, generally referred to

Astraeans, are higher than the true Astrseans, on account of their

compound Polyps.
FUNGID.E: indefinite multiplication of tentacles; imperfect trans-

verse beams.
ACTINIAE: indefinite multiplication of tentacles; soft bodies and no

transverse beams.

If now we compare this structural gradation
among Polyps with their geological succession,
we shall find that they correspond exactly. The
following table gives the geological order in
which they have been introduced upon the sur-
face ol tho earth.

GEOLOGICAL SUCCESSION.

Present, Halcyonoids.

Pliocene, "J

Miocene, r Madrepores.

Eocene,

Cretaceous, r

Jurassic, j Porites

Triassic,

Permian,
Carboniferous, "J
Devonian, r Fungidse,
Silurian,

AGE OF CORAL REEFS. 197

With regard to the geological position of the
Actiniae we can say nothing, because, if their soft,
gelatinous bodies have left any impressions in
the rocks, none such have ever been found ; but
their absence is no proof that they did not exist,
since it is exceedingly improbable that animals
destitute of any hard parts could be preserved.

The position of the Corals on a Reef accords
with these series of structural gradation and ge-
ological succession. It is true that we do not

SUCCESSION ON THE EEEF.
Halcyonoids.

.Madrepores.

CORAL REBpAPorites.

Maandrines.

-Astraeans.

find the Actiniae in the Reef any more than in the
crust of the earth, for the absence of hard parts in
their bodies makes them quite unfit to serve as
Reef-Builders. Neither do we find Fungidae, for
they, like all low forms, are single, and not con-
fined to one level, having a wider range in depth

198 AGE OF CORAL REEFS.

and extent than other stony Polyps. But the
true Reef-Building Polyps follow each other Dn
the Reef in the same order as prevails in their
structural gradation and their geological succes-
sion ; and whether we classify them according to
their position on the Reef, or their introduction
upon the earth in the course of time, or their
relative rank, the result is the same.

It would require an amount of details that
would be tedious to many ^)f my readers, were I
to add here the evidence now on record proving
that the embryological development of these ani-
mals, so far as it is known, and their geographical
distribution over the whole surface of our globe,
show the same correspondence with the other
three series. But this recurrence of the same
thought in the history of animals of the same
Type, showing that, from whatever side we con-
sider them, their creation and existence seem to
be guided by one Mind, is so important in the
study of Nature, that I shall constantly refer to it
in the course of these papers, even though I may
sometimes- be accused of unnecessary repetition,
or of extending my conclusions beyond the facts.

What is the significance of these coincidences ?
They were not sought for by the different inves-
tigators, who have worked quite independently
while ascertaining all these facts, without even
knowing that there was any relation between

AGE OF CORAL REEFS. 199

them. The succession of fossil Corals has been
found in the rocks by the geologist, — the embry-
ologist has followed the changes in the growth
of the living Corals, — the zoologist has traced
the geographical distribution and the structural
relations of the full-grown animals ; but it is
only after the results of their separate investi-
gations are collected and compared that the
coincidence is perceived, and all find that they
have been working unconsciously to one end.
These thoughts in Nature, which we are too prone
to call simply faxjts, when in reality they are the
ideal conception antecedent to the very existence
of all created beings, are expressed in the objects
of our study. It is not the zoologist who invents
the structural relations establishing a gradation
between all Polyps. — it is not the geologist who
places them in tho succession in which he finds
them in 'the rocks, — it is not the embryologist
who devises the changes through which the living
Polyps pass j»s he watches their growth ; these
investigators only read what they see, and, when
they compare their results, it is found that they
all tell the same story. He who reads most cor-
rectly from the original is the best naturalist.
What unites all their investigations, and makes
them perfectly coherent with each other, is the
coincidence of thought expressed in the facts
themselves. In other words, it is the working

200 AGE OF CORAL REEFS.

of the same Intellect through all time, every-
where.

When we observe the practical results of this
sequence in the position of Corals on the reef,
we canfiot fail to see that it is not a mere acci-
dental difference of structure and relation, but
that it bears direct reference to the part these
little beings were to play in Creation. It places
the solid part of the structure at -the base of the
Reef. — it fills in the interstices with a lighter
growth, — it crowns the summit with the more
delicate kinds, that yield to the action of the tides
and are easily crushed into the fine sand that
forms the soil, — it makes a masonry solid,
compact, time-defying, such a masonry as was
needed by the great Architect, who meant that
these smallest creatures of His hand should help
to build His islands and His continents.

HOMOLOGIES. 201

CHAPTER XIII.

HOMOLOGIES.

IT may seem to some of my readers that )
have wandered from my subject and forgotten
the title of these articles, which purport to be a
series of papers on " Methods of Study in Natu-
ral History." But some idea of the progress of
Natural History, of its growth as a science, of
the gradual evolving of general principles out of
a chaotic mass of facts, is a better aid to the stu-
dent than direct instruction upon special modes
of investigation ; and it is with the intention of
presenting the study of Natural History from
this point of view that I have chosen my title.

I have endeavored thus far to show how scien-
tific facts have been systematized so as to form a
classification that daily grows more true to Na-
ture, in proportion as its errors are corrected by
a more intimate acquaintance with the facts ; but
I will now attempt a more difficult task, and try
to give some idea of the mental process by which
facts are transformed into scientific truth. I fear
that the subject may seem very dry to iny read-

9*

202 HOMOLOGIES.

ers, and I would again ask their indulgence for
details absolutely essential to my purpose, but
which would indeed be very wearisome, did they
not lead us up to%n intelligent and most signifi-
cant interpretation of their meaning.

I should be glad to contribute my share to-
wards removing the idea that science is the mere
amassing of facts. It is true that scientific results
grow out of facts, but not till they have been fer-
tilized by thought. The facts must be collected,
but their mere accumulation will never advance
the sum of human knowledge by one step ; it is
the comparison of facts and their transformation
into ideas that lead to a deeper insight into the
significance of Nature. Stringing words together
in incoherent succession does not make an intelli-
gible sentence ; facts are the words of God, and we
may heap them together endlessly, but they will
teach us little or nothing till we place them in
their true relations, and recognize the thought
that binds them together as a consistent whole.

I have spoken of the plans that lie at the
foundation of all the variety of the Animal
Kingdom as so many structural ideas which
must have had an intellectual existence in the
Creative Conception independently of any special
material expression of them. Difficult though
it be to present these plans as pure abstract
formulae, distinct from the animals that represent

HOMOLOGIES. 203

them, I would nevertheless attempt to do it, in
order to show how the countless forms of animal
life have been generalized into the few grand,
but simple intellectual conceptions on which all
the past populations of the earth as well as the
present creation are founded. In such attempts
to divest the thought of its material expression,
especially when that expression is multiplied in
such thousand-fold variety of form and color, our
familiarity with living animals is almost an obsta-
cle to our success. For I shall hardly be able to
allude to the formula of the Radiates, for in-
stance, — the abstract idea that includes all the
structural possibilities of that division of the An-
imal Kingdom, — without recalling to my read-
ers a Polyp or a Jelly-Fish, a Sea-Urchin or a
Star-Fish. Neither can I present the structural
elements of the Mollusk plan, without reminding
them of an Oyster or a Clam, a Snail or a Cuttle-
Fish, — or of the Articulate plan, without calling
up at once the form of a Worm, a Lobster, or an
Insect, — or of the Vertebrate plan, without
giving it the special character of Fish, Reptile,
Bird, or Mammal. Yet I insist that all living
beings are but the different modes of expressing
these formulae, and that all animals have, within
the limits of their own branch of the Animal
Kingdom, the same structural elements, though
each branch is entirely distinct. If this be true,

204 HOMOLOGIES.

and if these organic formulae have the precision
of mathematical formulae, with which I have
compared them, they should be susceptible of the
same tests.

The mathematician proves the identity of prop-
ositions that have the same mathematical value
and significance by their convertibility. If they
have the same mathematical quantities, it must
be possible to transform them, one into another,
without changing anything that is essential ic
either. The problem before us is of the same
character. If, for instance, all Radiates, be they
Sea- Anemones, Jelly-Fishes, Star-Fishes, or Sea-
Urchins, are only various modes of expressing
the same organic formula, each having the sum
of all its structural elements, it should be possi-
ble to demonstrate that they are reciprocally con-
vertible. This is actually the case, and I hope to
be able to convince my readers that it is no fanci-
ful theory, but may be demonstrated as clearly as
the problems of the geometer. The naturalist
has his mathematics, as well as the geometer and
the astronomer ; and if the mathematics of the Aii-
imal Kingdom have a greater flexibility than those
of the positive sciences, and are therefore not so
easily resolved into their invariable elements, it
is because they have the freedom and pliability of
life, and evade our efforts to bring all their exter-
nal variety within the limits of the same structu-

HOMOLOGIES. 205

ral law which nevertheless controls and includes
them all.

I wish that I could take as the illustration of
this statement animals with whose structure the
least scientific of my readers might be presumed
to be familiar ; but such a comparison of the
Vertebrates, showing the identity and relation of
structural elements throughout the Branch, or
even in any one of its Classes, would be too ex-
tensive and complicated, and I must resort to the
Radiates, — that branch of the Animal Kingdom
which, though less generally known, has the sim-
plest structural elements.

I will take, then, for the further illustration of
my subject, the Radiates, and especially the class
of Echinoderms, Star-Fishes, Sea-Urchins, and
the like, both in the fossil and the living types ,
and though some special description of these ani-
mals is absolutely essential, I will beg my readers
to remember that the general idea, and not its
special manifestations, is the thing I am aiming
at^and that, if we analyze the special parts char-
acteristic of these different groups, it is only that
we may resolve them back again into the struc-
tural plan that includes them all.

I have already in a previous article named the
different Orders of this Class in their relative
rank, and have compared the standing of the liv-
ing ones, according to the greater or less compli-

206 HOMOLOGIES.

cation of thek structure, with the succession of
the fossil ones. Of the five Orders, Beches-de-Mer,
Sea-Urchins, Star-Fishes, Ophiurans, and Cri-
noids, — or, to name them all according to their
scientific nomenclature, Holothurians, Echinoids,
Asterioids, Ophiurans, and Crinoids, — the last-
named are lowest in structure and earliest in
time. Cuvier was the first naturalist who de-
tected the true nature of the Crinoids, and
placed them where they belong in the classifica-
tion of the Animal Kingdom. They had been
observed before, and long and laborious investi-
gations had been undertaken upon them, but
they were especially baffling to the student, be-
cause they were known only in the fossil condi-
tion from incomplete specimens ; and though
they still have their representatives among the
type of Echinoderms as it exists at present, yet,
partly owing to the rarity of the living specimens
and partly to the imperfect condition of the fossil
ones, the relation between them was not recog-
nized. The errors about them certainly did not
arise from any want of interest in the subject
among naturalists, for no less than three hundred
and eighty authors have published their investi-
gations upon the Crinoids, and the books that
have been printed about these animals, many of
which were written long before their animal na-
ture was suspected, would furnish a library in
themselves.

HOMOLOGIES. 207

The ancients knew little about them. The only
one to be found in the European seas resembles
the free Star-Fishes closely, and is now called
Gomatula ; but even Aristotle was ignorant of its
true structural relations, and alludes only to its
motion and general appearance. Some account
of the gradual steps by which naturalists have
deciphered the true nature of these lowest Echi-
noderms and their history in past times may not
be without interest, and is very instructive as
showing how such problems may be solved.

In the sixteenth century some stones were
found bearing the impression of a star on their
surface. They received the name of Trochites,
and gave rise to much discussion. Naturalists
puzzled their brains about them, called them star-
shaped crystals, aquatic plants, corals ; and to
these last Linnseus himself, the great authority of
the time on all such questions, referred them.
Beside these stony stars, which were found in
great quantities when attention was once called
to them, impressions of a peculiar kind had been
observed in the rocks, resembling flowers on long
stems, and called "stone lilies" naturally enough,
for their long, graceful stems, terminating either
in a branching crown or a closer cup, recall the
lily tribe among flowers. The long stems of these
seeming lilies are divided transversely at regular
intervals ; the stem is easily broken at any of

208 HOMOLOGIES.

these natural divisions, and on each such frag-
ment is stamped a star-like impression resem-
bling those found upon the loose stones or Tro-
chites.

About a century ago, Guettard the naturalist
described a curious specimen from Porto Rico, so
similar to these fossil lilies of the rocks that he
believed they must have some relation to each
other. He did not detect its animal nature, but
from its long stem and branching crown he
called it a marine palm. Thus far neither the
true nature of the living specimen, nor of the
Trochites, nor of the fossil lilies was understood,
but it was nevertheless an important step to have
found that there was a relation between them.
A century passed away, and Guettard's speci-
men, preserved at the Jardin des Plantes, waited
with Sphinx-like patience for the man who should
solve its riddle.

Cuvier, who held the key to so many of the
secrets of Nature, detected at last its true struc-
ture ; he pronounced it to be a Star-Fish with a
stem, and at once the three series of facts respect-
ing the Trochites, the fossil lilies, and Guettard's
marine palm assumed their true relation to each
other. The Trochites were recognized as simply
the broken portions of the stem of some of these
old fossil Crinoids, and the Crinoids. themselves
were seen to be the ancient representatives of

HOMOLOGIES. 209

the present Comatulae and Star-Fishes with stems.
So is it often with the study of Nature ; many
scattered links are collected before the man comes
who sees the connection between them and
speaks the word that reconstructs the broken
chain.

I will begin my comparison of all Echinoderms
with an -analysis of the Star-Fishes and Sea-
Urchins, because I think I can best show the
identity of parts between them, notwithstanding
the difference in their external form ; the Sea-
Urchins having always a spherical body, while
the Star-Fishes are always star-shaped, though in
some the star is only hinted at, sketched out, as
it were, in a simply^ pentagonal outline, while in
others the indentations between the rays are very
deep, and tha rays themselves so intricate in their
ramifications as to be broken up into a complete
net-work of branches. But under all this vari-
ety of outline, our problem remains always the
same : to build with the same number of pieces
a star and a sphere, having the liberty, however,
of cutting the pieces differently and changing
their relative proportions. Let us take first the
Sea-Urchin and examine in detail all parts of its
external structure. I shall say nothing of the
internal structure of any of these animals, be-
cause it does not affect the comparison of their
different forms and the external arrangement

210 HOMOLOGIES.

of parts, which is the subject of the present
article.

On the lower side is the mouth, and we may
call that side and all the parts radiating from it
the oral region. On the upper side is a small
area* to which the parts converge, and which,
from its position just opposite the so-called mouth
or oral opening, we may call the ab-oral region.
I prefer these more general terms, because, if we
speak of the mouth, we are at once reminded of
the mouth in the higher animals, and in this
sense the word, as applied to the aperture through
which the Sea-Urchins receive their food, is a
misnomer. Very naturally the habit has become
prevalent of naming the different parts of ani-
mals from their function, and not from their
structure ; and in all animals the aperture
through which food enters the body is called the
mouth, though there is not the least structural
relation between the organs so designated, except
•within the limits of each different branch or di-
vision. To speak of these opposite regions in the
Sea-Urchin as the upper and lower sides would
equally mislead us, since, as we have seen, there
is, properly speaking, no above and below, no right
and left sides, no front and hind extremities in
these animals, all parts being evenly distributed
around a vertical axis. I will therefore, although
it has been my wish to avoid technicalities as

HOMOLOGIES. 211

much as possible in these papers, make use of
the unfamiliar terms oral and ab-oral regions, to
indicate the mouth with the parts diverging
from it and the opposite area towards which all
these parts converge.*

Sea-Urchin seen from the oral side, showing the zones with the spines and
the suckers ; for the ab-oral side, on the summit of which the zones unite, see
the wood-cut on the next page, which shows a portion of that region.

The whole surface of the animal is divided by
zones, — ten in number, five broader ones alter-
nating with five narrow ones. The five broad
zones are composed of large plates on which are
the most prominent spines, attached to tubercles
that remain on the surface even when the spines
drop off after death, and mark the places where
the spines have been. The five small zones are
perforated with regular rows of holes, and
through these perforations pass the suckers or

* When reference is made to the whole structure, including the
internal organs as well as the solid parts of the surface, the terms
actinal and ab-actinal are preferable to oral and ab-oral.

212 HOMOLOGIES.

water-tubes which are their locomotive appen-
dages. For this reason these narrower zones are

Portion of Sea-Urchin representing one narrow zone with a part of the broad
zones on either side and the ab-oral area on the summit.

called the ambulacra, while the broader zones in-
tervening between them and supporting the
spines are called the inter ambulacra. Motion,
however, is not the only function of these suck-
ers ; they are subservient also to respiration and
circulation, taking in water, which is conveyed
through them into various parts of the body.

The oral aperture is occupied by five sets of
pieces, which may be called jaws, remembering
always that here again this word signifies the
function, and not the structure usually associated
with the presence of jaws in the higher animals ;
and each of these jaws terminates with a tooth,
set in its centre. Even the mode of eating in
these animals is controlled by their radiate struc-
ture ; for these jaws, evenly distributed about the

HOMOLOGIES. 213

circular oral aperture, open to receive the prey,
and -then are brought together to crush it, the
points meeting in the centre, thus working con-
centrically instead of moving up and down or
from right to left, as in other animals. From
the oral opening the ten zones diverge, spreading
over the whole surface, like the ribs on a melon,
and converging in the opposite direction till they
meet in a small space which we have called the
ab-oral region opposite the starting-pom fc.

Here the broad zones terminate in five large
plates differing somewhat from those that form
the zones in other parts of the body, and called
ovarian plates, because the eggs pass out through
certain openings in them ; while the five narrow
zones terminate in five small plates on each of
which is an eye, making thus five eyes alternating
with five ovarian plates. The centre of this area
containing the ovarian plates and the visual
plates is filled up with small movable plates clos-
ing the space between them. I should add, that
one of the five ovarian plates is larger than the
other four, and has a peculiar structure, long a
puzzle to naturalists. It is perforated with* mi-
nute holes, forming an exceedingly delicate sieve,
and this is actually the purpose it serves. It is,
as it were, a filter, and opens into a canal which
conducts water through the interior of the body ;
closed by this sieve on the outside, all the water

214

HOMOLOGIES.

that passes into it is purified from all foreign
substances that might be injurious to the animal,
and is thus fitted to pass into the water-system,
from which arise the main branches leading to
the minute suckers projecting through the holes
in the narrow zones of plates.

Now, in order to transibrm theoretically our
Sea-Urchin into a Star-Fish, what have we to do?
Let the reader imagine for a moment that the
small ab-oral area closing the space between the
ovarian plates and the eye-plates is elastic, and
may be stretched out indefinitely ; then split the
five broad zones along the centre, and draw them
down to the same level with the mouth, carry-
ing the ovarian plates between them. We have

Star-Fish from the ab-oral side.

then a star ; just as, dividing, for instance, the
peel of an orange into five segments, left, of

HOMOLOGIES. 215

course, united at the base, then stripping it off
and spreading it out flat, we should have a five-
rayed star. But in thus dividing the broad zones
of the Sea-Urchin into halves, we leave the
narrow zones in their original relation to them,
except that every narrow zone, instead of be-
ing placed between two broad zones, has now
one half of each of the zones with which it
alternated in the Sea-Urchin on either side of
it, and lies between them. The adjoining wood-
cut represents a single ray of a Star-Fish,

One arm of Star-Fish from the oral side.

drawn from what we call its lower or oral side.
Along the centre of every such ray, diverging
from the central opening or the mouth, we have
a furrow, corresponding exactly to the narrower

216 HOMOLOGIES.

zones of the Sea-Urchin. It is composed of com-
paratively small perforated plates, through which
pass the suckers or locomotive appendages ; and
on either side of the furrows are other plates,
corresponding to the plates of the broad zones in
the Sea-Urchin. Where shall we now look for
the five eyes ? Of course, at the tip of every ray ;
exactly where they were when the rays were
drawn up to form the summit of a sphere, for
then the eyes, which are now at the extremities
of the rays, were clustered together near the point
of meeting of the five zones on the ab-oral side
of the Sea-Urchin. Where shall we look for the
ovarian plates ? At each angle of the five rays,
because, when the broad zones of which they
formed the summit were divided, they followed
the split, and now occupy the place which,
though seemingly so different on the surface of
the Star-Fish, is nevertheless, relatively to the
rest of the body, the same as they occupied in
the Sea-Urchin. Assuming, as we premised, that
the central area of the ab-oral region, forming
the space between the plates at the summit of the
zones in the Sea-Urchin, is elastic, it has stretched
with the spreading out of the zones, following the
indentation between the rays, and now forms the
whole upper surface of the body. All the inter-
nal organs of the animal lie between the oral and
the ab-oral regions, just as they did in the Sea-

HOMOLOGIES. 217

Urchin, onlj that in the Star-Fish these regions
are coequal in extent, while in the Sea-Urchin
the ab-oral region is very contracted, and the
oral region, with the parts belonging to it, occu-
pies the greater part of its surface.

Such being the identity of parts between a
Star-Fish and a Sea-Urchin, let us see now how
the Star-Fish may be transformed into the Pe-
dunculated Crinoid, the earliest representative of
its Class, or into a Comatula, one of the free ani-
mals that represent the Crinoids in our day.

We have seen that in the Sea-Urchins the ab-
oral region is very contracted, the oral region
and the parts radiating from it and forming the
sides being the predominant features in the
structure ; and we shall find, as we proceed in
our comparison, that the different proportions of*
these three parts, the oral and ab-oral regions and
the sides, determine the different outlines of the
various Orders in this Class. In the Sea-Urchin
the oral region and the sides are predominant,
while the ab-oral region is very small. In the
Star-Fish, the oral and ab-oral regions are
brought into equal relations, neither preponder-
ating over the other, and the sides are compresses,
so that, seen in profile, the outline of the Star-
Fish is that of a slightly convex disk, instead
of a sphere, as in the Sea-Urchin. But when we
come to the Crinoids, we find that the great pre-

1Q

218 HOMOLOGIES.

ponderance of the ab-oral region determines all
that peculiarity of form which distinguishes them
from the other Echinoderms, while the oral regidm
is comparatively insignificant. The'ab-oral region
in the Crinoid rises to form a sort of cup-like
or calyx-like projection. The plates forming it,
which in the Star-Fish or the Sea-Urchin are
movable, are soldered together so as to be per-

Crinoid with branching crown ; oral side turned upward.

fectly immovable in the Crinoid. Let this seem-
ing calyx be now prolonged into a stem, and we

HOMOLOGIES. 219

see at once how striking is the resemblance to a
flower ; turn it downwards, an attitude which is
natural to these Crinoids, and the likeness to a
drooping lily is still more remarkable. The oral
region, with the radiating ambulacra, is now lim-
ited to the small flat area opposite the juncture
of the stem with the calyx ; and whether it
stretches out to form long arms, or is more com-
pact, so as to close the calyx like a cup, it seems
in either case to form a flower-like crown, bud-
like in Encrinus and other genera, and more like
an open flower in Platycrinus and the like. In
these types of Echiiioderrns the interarnbulacral
plates are absent ; there are no rows of plates of
a different kind alternating with the ambulacral
ones, as in the Sea-Urchins and Star-Fishes, but
the ab-oral region closes immediately upon the
ambulacra.

It seems a contradiction to say, that, though
these Crinoids were the only representatives of
their Class in the early geological ages, while it
includes five Orders at the present time, Echiiio-
derms were as numerous and various then as
now. But, paradoxical as it may seem, this is
nevertheless true, not only for this Class, but for
many others in the Animal Kingdom. The same
numerical proportions, the same richness and
vividness of conception, were manifested in the
early creation as now ; and though many of the

220 HOMOLOGIES.

groups were wanting that are most prominent in
modern geological periods, those that existed
were expressed in such endless variety that the
Animal Kingdom seems to have been as full then
as it is to-day. The Class of the Echinoderms is
one of the most remarkable instances of this pe-
culiar distribution. In the Silurian period, the
Crinoids stood alone ; there were neither Ophi-
urans, Asterioids, Echinoids, nor Holothurians ;
and yet in one single locality, Lockport, in the
State of New York, over an area of not more
than a few square miles, where the Silurian de-
posits have been carefully examined, there have
been found more different Species of Echino-
derms than are living now along our whole
Atlantic coast from Maine to Florida, where we
find representatives .of all the five orders of the
class.

There is nothing more striking in these early
populations than the richness of the types. It
would seem as if, before the world was prepared
for the manifold existences that now find their
home upon our earth, when organic life was
limited by the absence of many of the physical
conditions now prevalent, the whole wealth of
the Creative Thought lavished itself upon the
forms first introduced upon the globe. After
thirty years' study of the fossil Crinoids, I am
every day astonished by some new evidence of

HOMOLOGIES. 221

the ingenuity, the invention, the skill, if I may so
speak, shown in varying this single pattern of ani-
mal life. When one has become, by long study
of Nature, in some sense intimate with the animal
creation, it is impossible not to recognize in it the
immediate action of thought, and even to special-
ize the intellectual faculties it reveals. It speaks
of an infinite power of combination and analysis,
of reminiscence and prophecy, of that which has
been, in eternal harmony with that which is to be ;
and while we stand in reverence before the grand-
eur of the Creative Conception as a whole, there
breaks from it such lightness of fancy, such rich-
ness of invention, such variety and vividness of
color, nay, even the ripple of mirthfulness, — foi
Nature has its humorous side also, — that we
lose our grasp of its completeness in wonder at its
details, and our sense of its unity is clouded by
its marvellous fertility. There may seem to be
an irreverence in thus characterizing the Crea-
tive Thought by epithets which we derive from
the exercise of our own mental faculties ; but it
is nevertheless true, that, the nearer we come to
Nature, the more does it seem to us that all our
intellectual endowments are merely the echo of
the Almighty Mind, and that the eternal arche-
types of all manifestations of thought in man
are found in the Creation of which he is the
crowning work.

222 HOMOLOGIES.

In no group of the Animal Kingdom is the
fertility of invention more striking than in
the Oinoids. They seem like the productions
of one who handles his work with an infinite
ease and delight, taking pleasure in presenting
the same thought under a thousand different as-
pects. Some new cut of the plates, some slight
change in their relative position, is constantly va-
rying their outlines, from a close cup to an open
crown, from the long pear-shaped oval of the
calyx in some to its circular or square or pentag-
onal form in others. An angle that is simple
in one projects by a fold of the surface and be-
comes a fluted column in another ; a plate that
was smooth but now has here a symmetrical figure
upon it drawn in beaded lines ; the stem which
is perfectly unbroken in one, except by the trans-
verse divisions common to them all, in the next
puts out feathery plumes at every such transverse
break. In some the plates of the stem are all
rigid and firmly soldered together ; in others they
are articulated upon each other in such a manner
as to give it the greatest flexibility, and allow
the seeming flower to wave and bend upon its
stalk. It would require an endless number of
illustrations to give even a faint idea of the vari-
ety of these fossil Crinoids. There is no change
that the fancy can suggest within the limits of
the same structure that does not find expression

HOMOLOGIES. 223

among them. Since I have become intimate with
their wonderful complications, I have sometimes
amused myself with anticipating some new vari-
ation of the theme, by the introduction of some
undescribed structural complication, and then
seeking for it among the specimens at my com-
mand, I have rarely failed to find it in one or
other of these ever-changing forms.

The modern Crinoid without stem, or the
Comatula, though agreeing with the ancient in
all the essential elements of structure, differs
from it in some specific features. It drops its
stem when full grown, though the ab-oral region
still remains the predominant part of the body,
and retains its cup-like or calyx-like form. The
Comatulae are not abundant, and though repre-
sented by a number of Species, yet the type as it
exists at present is meagre, in comparison to its
richness in former times. Indeed, this group of
Echinoderms, which, in the earliest periods, was
the exponent of all its kind, has dwindled grad-
ually, in proportion as other representatives of
the Class have come in ; and there exists only
one species now, the Pentacrinus of the West
Indies, which retains its stem in its adult condi-
tion. It is a singular fact, to which I have before
alluded, and which would seem to have especial
reference to the maintenance of the same numeric,
proportions in all times, that, while a Class is

224 HOMOLOGIES.

represented by few types, those types are wonder-
fully rich and varied ; but in proportion as other
expressions of the same structure are introduced,
the first dwindle, and, if they do not entirely dis-
appear, become at least much less prominent than
before.

There remain only two other Orders to be con-
sidered, the Ophiurans and the Holothurians.
The Ophiurans approach the Crinoids more
nearly than any other group of Echinoderms,
and in our classifications are placed next above
them. In them the ab-oral region, which has

Ophiuran; showing one ray from the oral side.

such a remarkable predominance in the Crinoid,
has become depressed : it no longer extends into
a stem, nor does it even rise into the calyx-like

HOMOLOGIES. 225

or cup-like projection so characteristic of the Cri-
noids, — though, when the animal is living, the
ab-oral side of the disk is still quite convex.
The disk in the Ophiurans is small in comparison
to the length of the arms, and perfectly circular.
It does not merge gradually into the arms, as in
the Star-Fish, but the arms start abruptly from
its periphery. In these, as in the Crinoids, the
interambulacral plates are absent, and the inter-
ambulacral spaces are filled by an encroachment
of the ab-oral region upon them. There is an
infinite variety and beauty both of form and color
in these Sea- Stars. The arms frequently measure
many times the diameter of the whole disk, and
are so different in size and ornamentation in the
different Species, that, at first sight, one might
take them for animals entirely distinct from each
other.. In some the arms are comparatively short,
and quite simple ; in others they are very long,
and may be either stretched to their full length,
or partly contracted, to form a variety of graceful
curves. In some they are fringed all along the
edges ; in others they are so ramified that every
arm seems like a little bush, as it were, and, in-
tertwining with each other, they make a thick
net-work all around the animal. In the geological
succession, these Ophiurans follow the Crinoids,
being introduced at about the Carboniferous
period, and perhaps earlier. They have had
10 o

226 HOMOLOGIES.

their representatives in all succeeding times, and
are still very numerous in the present epoch.

To show the correspondence of the Holothu-
rians with the typical formula of the whole class
of Echinoderms, I will return to the Sea-Urchins,
since they are more nearly allied with that Order
than with any of the other groups. We have seen
that the Sea-Urchins approach most nearly to the
sphere, and that in them the oral region and the
sides predominate so greatly over the ab-oral
region, that the latter is reduced to a small area
on the summit of the sphere. In order to trans-
form the Sea-Urchin into a Holothurian, we have
only to stretch it out from end to end till it be-
comes a cylinder, with the oral region or mouth
at one extremity, and the ab-oral region, which,
in the Holothurian, is reduced to its minimum,

Holothurian.

at the other. The zones of the Sea-Urchin now
extend as parallel rows on the Holothurian, run-
ning from one end to the other of the long cylin-
drical body. On account of their form, some
of them have been taken for Worms, and so clas-

HOMOLOGIES. 227

by naturalists ; but as soon as their true
structure was understood, agreeing in every re-
spect with that of the other Echinoderms, and
having no affinity whatever with the articulated
structure of the Worms, they found their true
place in our classifications.

The natural attitude of these animals is differ-
ent from that of the other Echinoderms. They
lie on one side, and move with the oral opening
forward ; and this has been one cause of the
mistakes as to their true affinity. But when we
would compare animals, we should place them,
not in the attitude which is natural to them in
their native element, but in what .1 would call
their normal position, — that is, such a position as
brings the corresponding parts into the same re-
lation in all. For instance, the natural attitude
of the Crinoid is with the ab-oral region down-
ward, attached to a stem, and the oral region or
mouth upward. The Ophiuran turns its oral
region, along which all the suckers or ambulacra
are arranged, toward the surface along which it
moves. The Star-Fish does the same. The Sea-
Urchin also has its oral opening downward. But
the Holothurian moves on one side, mouth fore-
most, as represented in the preceding wood-cut,
dragging itself onward, like all the rest, by means
of its rows of suckers. If, now, we compare
these animals in the various attitudes natural to

228 HOMOLOGIES.

them, we may fail to recognize the identity of
parts, or, at least, it will not strike us at once.
But if we place them all — Holothurian, Sea-
Urchin, Star-Fish, Ophiuran, and Crinoid — with
the oral or mouth side downward, for instance,
we shall see immediately that the small area at
the opposite end of the Holothurian corresponds
to the area on the top of the Sea-Urchin ; that the
upper side of the Star-Fish is the same region
enlarged ; that, in the Ophiuran, that region
makes one side of the small circular disk ; while
in the Crinoid it is enlarged and extended to
make the calyx-like projection and stem. In the
same way, if we place them in the same attitude,
we shall see that the long, straight rows of suck-
ers along the length of the Holothurian, and the
arching zones of suckers on the spherical body of
the Sea-Urchin, and the furrows with the suckers
protruding from them along the arms of the Star-
Fish and Ophiuran, and the radiating series of
pores from the oral opening in the Crinoid, are
one and the same thing in all, only altered some-
what in their relative proportion and extent.
Around the oral opening of the Holothurian there
are appendages capable of the most extraordinary
changes, which seem at first to be peculiar to
these animals, and to have no affinity with any
corresponding feature in the same Class. But a
closer investigation has shown them to be only

HOMOLOGIES. 229

modifications of the locomotive suckers of the
Star-Fishes and Sea-Urchins, but ramifying to
such an extent as to assume the form of branch-
ing feelers. The little tufts projecting from the
oral side in the Sea-Urchins, described as gills,
are another form of the same kind of appendage.
The Holothurians have not the hard, brittle
surface of the other Echinoderms ; on the con-
trary, their envelope is tough and leathery, ca-
pable of great contraction and dilatation. No
idea can be frrmed of the beauty of these
animals either from dried specimens or from
those preserved in alcohol. Of course, in either
case, they lose their color, become shrunken, and
the movable appendages about the mouth shrivel
up. One who had seen Holothurians only as
preserved in museums would be amazed at the
spectacle of the living animal, especially if his first
introduction should be to one of the deep, rich
crimson-colored species, such as are found in quan-
tities in the Bay of Fundy. I have seen such an
animal, when first thrown into a tank of sea-water,
remain for a while closely contracted, looking
like a soft crimson ball. Slowly, almost imper-
ceptibly, as it becomes accustomed to its new
position, it begins to elongate ; the fringes creep
softly out, spreading gradually all their ramifica-
tions, till one end of the animal seems crowned
with feathery, crimson sea-weeds of the most

230 HOMOLOGIES.

delicate tracery. It is much to be regretted that
these lower marine animals are not better known.
The plumage of the tropical birds, the down on
the most brilliant butterfly's wing, are not more
beautiful in coloring than the hues of many
Radiates, and there is no grace of motion sur-
passing the movements of some of them in their
native element. The habit of keeping marine
animals in tanks is happily growing constantly
more popular, and before long the beauty of these
inhabitants of the ocean will be as familiar to us
as that of Birds and Insects. Many of the most
beautiful among them are, however, difficult to
obtain, and not easily kept alive in confinement,
so that they are not often seen in aquariums.

Having thus endeavored to sketch each differ-
ent kind of Echinoderm, let us try to forget them
all in their individuality, and think only of the
structural formula that applies equally to each.
In all, the body has three distinct regions, the
j>ral, the ab-oral, and the sides ; but by giving a
predominance to one or the other of these regions,
a variety of outlines characteristic of the differ-
ent groups is produced. In all, the parts radiate
from the oral opening, and join in the ab-oral
region. In all, this radiation is accompanied by
rows of suckers following the line of the diverging
rays. It is always the same structure, but, en-
dowed with the freedom of life, it is never monot-

HOMOLOGIES. 231

onous, notwithstanding its absolute permanence.
In short, drop off the stem of the Crinoid, and
depress its calyx to form a flat disk, and we have
an Ophiuran ; expand that disk, and let it merge
gradually in the arms, and we have a Star-Fish ;
draw up the rays of the Star-Fish, and unite
them at the tips so as to form a spherical outline,
and we have a Sea-Urchin ; stretch out the Sea-
Urchin to form a cylinder, and we have a Holo-
thurian.

And now let me ask, — Is it my ingenuity that
has imposed upon these structures the conclusions
I have drawn from them ? — have I so combined
them in my thought that they have become to
me a plastic form, out of which I draw a Crinoid,
an Ophiuran, a Star-Fish, a Sea-Urchin, or a
Holothurian at will ? or is this structural idea
inherent in them all, so that every observer who
has a true insight into their organization must
find it written there ? Had our scientific results
anything to do with our inventive faculties, every
naturalist's conclusions would be colored by his
individual opinions ; but when we find all zoolo-
gists converging more and more towards each
other, arriving, as their knowledge increases, at
exactly the same views, then we must believe
that these structures are the Creative Ideas in
living reality. In other words, so far as there is
truth in them, our systems are what they are,

232 HOMOLOGIES.

not because Aristotle, Linnaeus, Cuvier, or all
the men who ever studied Nature, have so thought
and so expressed their thought, but because God
so thought and so expressed his thought in ma-
terial forms when he laid the plan of Creation,
and when man himself existed only in the intel-
lectual conception of his Maker.

ALTERNATE GENERATIONS. 233

CHAPTER XIV.

ALTERNATE GENERATIONS.

IP I succeeded in explaining my subject clearly
in the last chapter, my readers will have seen
that the five Orders of the Echinoderms are but.
five expressions of the came idea ; and I will now
endeavor to show that the same identity of struc-
tural conception prevails also throughout the two
other Classes of Radiates, and further, that not
only are the Orders within each Class built upon
the same plan, but that the three Classes them-
selves, Echinoderms, Acalephs, and Polyps, are
also based upon one organic formula.

We will first compare the three Orders of
Acalephs, among which the Hydroids stand low-
est, the Discophorae next, and the Ctenophoras
highest. The fact that these animals have no
popular names shows how little they are known.
It is true that we hear some of them spoken of as
Jelly -Fishes ; but this name is usually applied to
the larger Discophore, when it is thrown upon
the beach and lies a shapeless mass of gelatinous
substance on the sand, or is seen floating on the

234 ALTERNATE GENERATIONS.

surface of the water. The name gives no idea of
the animal as it exists in full life and activity.
When we speak of a Bird or an Insect, the mere
name calls up at once a characteristic image of
the thing ; but the name of Jelly-Fish, or Sun-
Fish, or Sea-Blubber, as the larger Acalephs are
also called, suggests to most persons a vague idea
of a fish with a gelatinous body, — or, if they
have lived near the sea-shore, they associate it
only with the unsightly masses of jelly-like sub-
stance sometimes strewn in thousands along the
beach after a storm. To very few does the term
recall either the large Discophore, with its pur-
ple disk and its long streamers floating perhaps
twenty or thirty feet behind it as it swims, — or
the Ctenophore, with its more delicate, trans-
parent structure, and almost invisible fringes in
parallel rows upon the body, which decompose
the rays of light as the creature moves through
the water, so that hues of ruby-red and emerald-
green, blue, purple, yellow, all the colors of the
rainbow, ripple constantly over its surface when
it is in motion, — or the Hydroid, with its little
shrub-like communities living in tide-pools, estab-
lishing themselves on rocks, shells, or sea-weeds,
and giving birth not only to animals attached
to submarine bodies, like themselves, but also to
free Medusae or Jelly-Fishes that in their turn
give birth again to eggs which return to the

ALTERNATE GENERATIONS. 235

parent form, and thus, by alternate generations,
maintain two distinct patterns of animal life
within one cycle of growth.

Perhaps, of all the three Classes of Radiates,
Acalephs are the least known. The general
interest in Corals has called attention to the
Polyps, and the accessible haunts of the Sea-
Urchins and Star-Fishes have made the Echino-
derms almost as familiar to the ordinary observer
as the common sea-shells, while the Acalephs are
usually to be found at a greater distance from
the shore, and are not easily kept in confinement.
It is true that the Hydroids live along the shore,
and may be reared in tanks without difficulty ;
but they are small, and would be often taken
for sea-weeds by those ignorant of their true
structure. Thus this group of animals, with
all their beauty of form, color, and movement,
and peculiarly interesting from their singular
modes of growth, remains comparatively un-
known except to the professional naturalist.

It may, therefore, be not uninteresting or use
less to my readers, if I give' some account of the
appearance and habits of these animals, "teeping
in view, at the same time, my ultimate object,
namely, to show that they are all founded on
the same structural elements and have the same
ideal significance. I will begin with some ac-
count of the Hydroids, including the story of the

236 ALTERNATE GENERATIONS.

alternate generations, by which they give birth to
Medusae, while the Medusae, in their turn, repro-
duce the Hydroids, from which they spring. But
first, a few words upon the growth of Radiates in
general.

There is no more interesting series of trans-
formations than that of the development of Ra-
diates. They are all born as little transparent
globular bodies, covered with vibratile cilia,
swimming about in this condition for a longer or
shorter time ; then, tapering somewhat at one
end and broadening at the other, they may be-
come attached by the narrower extremity, while
at the opposite one a depression takes place,
deepening in the centre till it becomes an aper-
ture, and extending its margin to form the ten-
tacles. All Radiates pass through this Polyp-like
condition at some period of their lives, either
before or after they are hatched from the eggs,
though they do not all attach themselves per-
manently. In some it forms a marked period of
their existence, while in others it passes very
rapidly, and is undergone within the egg ; but,
at whatever time and under whatever conditions
it occurs, it forms a necessary part of their devel-
opment, and shows that all these animals have
one and the same pattern of growth.

This difference in the relative importance and
duration of certain phases of growth is by no

ALTERNATE GENERATIONS. 237

means peculiar to the Radiates, but occurs in all
divisions of the Animal Kingdom. There are
many Insects that pass through their metamor-
phoses within the egg, appearing as complete
Insects at the moment of their birth ; but the
series of changes is nevertheless analogous to
that of the Butterfly, whose existence as Worm,
Chrysalis, and Winged Insect is so well known
to all. Take the Grasshopper, for instance :
with the exception of the wings, it is born in
its mature form ; but within the egg it has had
its Worm-like stage as much as the Butterfly
that we knew a few months ago as a Caterpillar.
In the same way certain of the higher Radiates
undergo all their transformations, from the Polyp
phase of growth to that of Acaleph or Echino-
derm, after birth ; while others pass rapidly
through the lower phases of their existence
within the egg, and are born in their final con-
dition, when all their intermediate changes have
been completed.

We have appropriate names for all the aspects
of life in the Insect : we call it Larva in its first
or Worm-like period, Chrysalis in its second or
Crustacean-like phase of life, and Imago in its
third and last condition as Winged Insect. But
the metamorphoses of the Radiates are too little
known to be characterized by popular names ;
and when they were first traced, the- relation

238 ALTERNATE GENERATIONS.

between their different phases of -existence was
not understood, so that the same animal in differ-
ent stages of growth- has frequently been described
as two or more distinct animals. This has led to
a confusion in our nomenclature much to be
regretted ; for, however inappropriate it may be,
a name once accepted and passed info general
use is not easily changed.

That early stage of growth, common to all
Radiates, in which they resemble the Polyps, has
been called the Hydra state, in consequence of
their resemblance to the fresh-water Hydra to be
found in quantities on the under side of Duck-
Weed and Lily-pads. For any one that cares to
examine these animals, it may be well to mention
that they are easily found and thrive well in
confinement. Dip a pitcher into any pool of
fresh water where Duck-Weed or Lilies are
growing in the summer, and you are sure to
bring up hundreds of these fresh-water Hydras,
swarming in myriads in all our ponds. In a glass
bowl their motions are easily watched ; and a
great deal may be learned of their habits and mode
of life, with little trouble. Such an animal
soon completes its growth : for the stage which I
have spoken of as transient for the higher Radi-
ates is permanent for these ; and when the little
sphere moving about by means of its vibratile
cilia has elongated a little, attached itself by the

ALTERNATE GENERATIONS. 239

lower end to some surface, while the inversion of
the upper end has formed the mouth and diges-
tive cavity, and the expansion of its margin has
made the tentacles, the very simple story of the
fresh-water Hydra is told. But the last page in
the development of these lower Radiates is but
the opening chapter in that of the higher ones,
and I will give some account of their trans-
formations as they have been observed in the
Acalephs.

On shells and stones, on sea-weeds or on
floating logs, there may often be observed a
growth of exquisitely delicate branches, look-
ing at first sight more like a small bunch of
moss than anything else. But gather such a

Coryne mirabilis, natural size.

mossy tuft and place it in a glass bowl filled
with sea-water, and you will presently find that
it is full of life and activity. Every branch of
this miniature shrub terminates in a little club-
shaped head, upon which are scattered a num-
ber of tentacles. They are in constant motion,

240 ALTERNATE GENERATIONS.

extending and contracting their tentacles, some
of the heads stretched upwards, others bent

Single head or branch of Coryne mirabilis, magnified, with two Medusa bud*.

downwards, all seeming very busy and active.
Each tentacle has a globular tip filled with a
multitude of cells, the so-called lasso-cells, each
one of which conceals a coiled-up thread. These
organs serve to seize the prey, shooting out
their long threads, thus entangling the victim
in a net more delicate than the finest spider's
web, and then carrying it to the mouth by
the aid of the lower part of the tentacle. The
complication of structure in these animals, a
whole community of which, numbering from
twenty to thirty individuals, is not more than
an inch in height, is truly wonderful. In such

ALTERNATE GENERATIONS. 241

a community the different animals are hardly
larger than a good-sized pin's head ; and yet
every individual has a digestive cavity and a
complete system of circulation.

Its body consists of a cavity enclosed in a
double wall, continuing along the whole length
of each branch till it joins the common stem
forming the base of the stock. In this cavity
the food becomes softened and liquefied by the
water that enters with it through the mouth, and
is thus transformed into a circulating fluid which
flows from each head to the very base of the
community and back again. The inner surface
of the digestive cavity is lined with brownish-red
granules, which probably aid in the process of
digestion ; they frequently become -loosened, fall
into the circulating fluid, and may be seen borne
along the stream as it passes up and down. The
rosy tint of the little community is due to these
reddish granules.

This crowd of beings united in a«common life
began as one such little Hydra-like animal as I
have described above, — floating free at first,
then becoming attached, and growing into a
populous stock by putting out buds at different
heights along the length of the stem. The for-
mation of such a bud is very simple, produced
by the folding outwardly of the double wall of
the body, appearing first as a slight projection
n ?

242 ALTERNATE GENERATIONS.

of the stem sideways, which elongates gradually,
putting out tentacles as it grows longer, while
at the upper end an aperture is formed to make
the mouth. This is one of the lower group
of Radiates, known as Hydroids, and long be-
lieved to be Polyps, from their mode of living
in communities and reproducing their kind by
budding, after the fashion of Corals.

But if such a little tuft of Hydroids has bee*
gathered in spring, a close observer may have
an opportunity of watching the growth of an-
other kind of individual from it, which would
seem to show its alliance with the Acalephs
rather than the Polyps. At any time late in
February or early in March, bulb-like projec-
tions, more globular than the somewhat elon-
gated buds of the true Hydroid heads, may be
seen growing either among the tentacles of one
of these little animals, or just below the head
where it merges in the stem.* Very delicate
and transparent in substance, it is hardly per-
ceptible at first; and the gradual formation of
its internal structure is the less easily discerned,
because a horny sheath, forming the outer cover-
ing of the Hydroid stock, extends to enclose and
shield the new-comer, whom we shall see to be
so different from the animal that gives it birth
that one would suppose the Hydroid parent must

* See wood-cut, p. 240.

ALTERNATE GENERATIONS. 243

be as much surprised at the sight of its off-
spring as the Hen that has accidentally hatched
a Duck's egg. At the right moment this film
is torn open by the convulsive contractions of
the animal, which, thus freed from its envelope,
begins at once to expand. By this time the
little bud has assumed the form of a Medusoid
or Jelly-Fish disk, with its four tubes radiating
from the central cavity. The proboscis, so char-
acteristic of all Jelly-Fishes, hangs from the cen-
tral opening ; and the tentacles, coiled within
the internal cavity up to this time, now make
their appearance, and we have a complete little
Medusa growing upon the Hydroid head. Gradu-
ally the point by which it is attached to the
parent-stock narrows and becomes more and
more contracted, till the animal drops off and
swims away, a free Jelly-Fish.

The substance of these animals seems to have
hardly more density or solidity than their native
element. I remember showing one to a friend
who had never seen such an animal before, and,
after watching its graceful motions for a moment
in the glass bowl where it was swimming, he
asked, "Is it anything more than organized
water ? " The question was very descriptive ; for
so little did it seem to differ in substance from
the water in which it floated that one might
well fancy that some drops had taken upon

244 ALTERNATE GENERATIONS.

themselves organic structure, and had begun to
live and move. It swims by means of rapid
contractions and expansions of its disk, thus
impelling itself through the water, its tentacles
floating behind it and measuring many times
the length of the body. The disk is very con-

Little Jelly-Fish, called Sarsia, the free Medusa of Coryne mirabilis.

vex, as will be seen by the wood-cut ; four tubes
radiate from the central cavity to the periphery,

ALTERNATE GENERATIONS. 2i5

where they unite in a circular tube around the
margin and connect also with the four tenta-
cles ; from the centre of the lower surface hangs
the proboscis, terminating in a mouth. Not-
withstanding the delicate structure of this little
being, it is exceedingly voracious. It places it-
self upon the surface of the animal on which
it feeds, and, if it "have any hard parts, it simply
sucks the juices, dropping the dead carcass im-
mediately after ; but it swallows whole the little
Acalephs of other Species and other soft ani-
mals that come in its way. Early in summer
these Jelly-Fishes drop their eggs, little trans-
parent pear-shaped bodies, covered with vibratile
cilia. They swim about for a time, until they
have found a resting-place, where they attach
themselves, each one founding a Hydroid stock
of its own, which will in time produce a new
brood of Medusae.

This serie^ of facts, presented here in their
connection, had been observed separately before
their true relation was understood. Investigations
had been made on the Hydroid stock, described
as Coryne, and upon its Medusoid offspring, de-
scribed as Sarsia, named after the naturalist Sars,
whose beautiful papers upon this class of animals
have associated his name with it ; but the inves-
tigations by which all these facts have been asso-
ciated in one connected series are very recent.

246 ALTERNATE GENERATIONS.

These transformations do not correspond to our
common idea of metamorphoses, as observed in
the Insect, for instance. In the Butterfly's life
we have always one and the same individual, —
the Caterpillar passing into the -Chrysalis state,
and the Chrysalis passing into the condition of
the Winged Insect. But in the case I have heen
describing, while the Hydroid gives birth to the
Medusa, it still preserves its own distinct exist-
ence ; and the different forms developed on one
stock seem to be two parallel lives, and not the
various phases of one and the same life. This
group of Hydroids retains the name of Coryne ; *
and the Medusa born from it, the Sarsia (repre-
sented on p. 244), has received, as I have said,
the name of the distinguished investigator to
whose labors we owe much of our present knowl-
edge of these animals. Let us look now at an-
other group of Hydroids, whose mode of develop-
ment is equally curious and interesting.

The little transparent embryos from which they
arise, oval in form, with a slight, scarcely percep-
tible depression at one end, resemble the embryos
of Coryne already described. They may be seen
in great numbers in the autumn, floating about in
the water, or rather swimming, — for the motion
of all Radiates in their earliest stage of existence
is rapid. and constant, in consequence of the vi-

* See wood-cut, p. 239

ALTERNATE GENERATIONS. 247

bratile cilia that cover the surface. At this stage
of its existence such an embryo is perfectly free,
but presently its wandering life comes to an end :
it shows a disposition to become fixed, and pro-
ceeds to choose a suitable resting-place. I iise
the word " choose " advisedly ; for though at this
time the little embryo seems to have no developed
organs, it yet exercises a certain discrimination
in its selection of a home. Slightly pear-shaped
in form, it settles down upon its narrower end.
It wavers and sways to and fro, as if trying to get
a firm foot-hold, and force itself down upon the
surface to which it adheres; but presently, as if
dissatisfied with the spot it has chosen, it sud-
denly breaks loose and swims away to another
locality, where the same examination is repeated,
not more to its own satisfaction apparently, for
the creature will renew the experiment half a
dozen times, perhaps, before making a final selec-
tion, and becoming permanently attached to the
soil. In the course of this process the lower end
becomes flattened, and moulds itself to the shape
of the body on which it rests. Once settled, this
animal, thus far hardly more than a transparent
oblong body, without any distinct organs, begins
to develop rapidly. It elongates, forming a kind
of cup-like base or stem ; the upper end spreads
somewhat ; the depression at its centre, deepens ;
a mouth is formed that gapes widely, and opens

248 'ALTERNATE GENERATIONS.

into the digestive cavity ; and the upper margin
spreads out to form a number of tentacles, few at
first, but growing more and more numerous, till
a wreath is completed all around it. In this con-
dition the young Jelly-Fish has been described
under the name of Scyphostbma. As soon as the

Scyphostoma of Aurelia flavidula, the white Jelly-Fish with a rosy cross, com-
mon along the coasts of New England.

wreath of tentacles is complete, a constriction
takes place below it, thus separating the upper
portion of the animal from the lower by a marked
dividing-line. Presently a second constriction
takes place below the first, then a third, till the
entire length of the animal is divided across by a
number of such transverse constrictions, the whole
body growing, meanwhile, in height. But now an
extraordinary change takes place in the portions
thus divided off. Each one assumes a distinct
organic structure, as if it had an individual life
of its own. The margin becomes lobed in eight
deep scallops, and a tube or canal runs through
the centre of each such lobe to the centre of the

ALTERNATE GENERATIONS. 249

body, where a digestive cavity is already formed.
At this time the constrictions have deepened, so
that the margins of all the successive divisions of
the little Hydroid are very prominent, and the
whole animal looks like a pile of saucers, or of
disks with scalloped edges, ancl the convex side
turned downward. Its general aspect may be
compared to a string of Lilac-blossoms, such as
the children make for necklaces in the spring, in

Strobila of Aurelia flavidula.

which the base of one. blossom is inserted into the
upper side of the one below it. In this condition
our Jelly-Fish has been called Strobila.
. While these organic changes take place in the
lower disks, the topmost one, forming the summit
of the pile and bearing the tentacles, undergoes
no such modification ; but presently the first con-
striction dividing it from the rest deepens to such
11*

250 ALTERNATE GENERATIONS.

a degree that it remains united to them by a
mere thread only, and it soon breaks off and dies.
Tliis is the signal for the breaking up of the whole
pile in the same way by the deepening of the con-
strictions ; but, instead of dying, as they part,
they begin a new existence as free Medusae. Only
the lowest portion of the body remains, and around
its margin new tentacles are developed, corre-
sponding to those which crowned the first little
embryo. This repeats the whole history again,

Strobila of Aurelia flavidula : o, Scyphostoma reproduced at the base of a
Strobila, all the disks of which have dropped off but the last, b b.

as it grows up during the following season to
divide itself anew into disks, like its predecessor.
As each individual separates from the commu-
nity of which it has made a part, it reverses its
position, and, instead of turning the margin of
the disk upward, it turns it downward, thus
bringing the mouth below, and the curve of the
disk above. These free individuals have been
described under the name of Ephyra. This is
the third phase of the existence of our Jelly-Fish.
It swims freely about, a transparent, umbrella-

ALTERNATE GENERATIONS. 251

like disk, with a proboscis hanging from the lower
side, which, to complete the comparison, we may
call the handle of the umbrella. The margin of
the disk- is even more deeply lobed than in the
Hydroid condition, and in the middle of each lobe
is a second depression, quite deep and narrow, at

Ephyra or Aurelia flavidula.

the base of which is an eye. How far such organs
are gifted with the power of vision we cannot de-
cide ; but the cells of which they are composed
certainly serve the purpose of facets, of lenses
and prisms, and must convey to the animal a
more or less distinct perception of light and color.
The lobes are eight in number, as before, with a
tube diverging from the centre of the body into
each lobe. Shorter tubes between the lobes alter-
nate with these, making thus sixteen radiating
tubes, all ramifying more or less.

From this stage to its adult condition, the
animal undergoes a succession of changes in
the gradual course of its growth, uninterrupted,
however, by any such abrupt transition as that

252

ALTERNATE GENERATIONS.

by which it began its life as a free animal. The
lobes are gradually obliterated, so that the mar-

Aurelia flavidula, the common white Jelly-Fish of our sea-shores, seen from
above : c, mouth ; e e e e e et eyes ; m m m m, lobes or curtain of the mouth
in outlines ; o o o, ovaries ; tt t, tentacles ; w u>, ramified tubes.

gin becomes almost an unbroken circle. The
eight eyes were, as I have said, at the bottom of
depressions in the centre of the several lobes ;
but, by the equalizing of the marginal line, the
gradual levelling, as it were, of all the inequali-
ties of the edge, the eyes are pushed out, and
occupy eight spots on the margin, where a faint
indentation only marks what was before a deep
cut in the lobe. The eight tubes of the lobes
have extended in like manner to the edge, and

ALTERNATE GENERATIONS. 253

join it just at the point where the eyes are
placed, so that the extremity of each tube
unites with the base of each eye. Those parts
of the margin filling the spaces between the
eyes correspond to the depressions dividing the
lobes or scallops in the earlier stage, and to
these radiate the eight other tubes alternating
with the eye-tubes, now divided into numerous
branches. Along each of these spaces is devel-
oped a fine, delicate fringe of tentacles, hanging
down like a veil when the animal is at rest, or
swept back when it is in motion. In the previous
stage, the tubes ramified toward the margin ; but
now they branch at or near their point of starting
from the central cavity, so extensively that every
part of the body is traversed by these collateral
tubes, and when one looks down at it from above
through the gelatinous transparent disk, the nu-
merous ramifications resemble the fine fibrous
structure of a leaf with its net-work of nervules.

On the lower side, or what I have called in a
previous chapter the oral region of the animal, a
wonderfully complicated aparatus is developed.
The mouth projects in four angles, and at each
such angle a curtain arises, stretching outwardly,
and sometimes extending as far as the margin.
These curtains are fringed and folded on the
lower edge, so that they look like four ruffled
flounces hanging from the lower side of ilia

254 ALTERNATE GENERATIONS.

animal. On the upper side of the body, but
alternating in position with these curtains, are
the four ovaries, crescent-like in shape, and so
placed as to form the figure of a cross, when seen
from above through the transparency of the disk.
I should add, that, though I speak of some organs
as being on the upper and others on the lower
srde of the body, all are under the convex,
arched surface of the disk, which is gelatinous
throughout, and simply forms a transparent
vaulted roof, as it were, above the rest of the
body.

Aurelia flavidula, seen in profile.

When these animals first make their appear-
ance in the spring, they may be seen, when the
sky is clear and the sea smooth, floating in im-
mense numbers near the surface of the water,
though they do not seek the glare of the sun,
but are more often found about sheltered places,
in the neighborhood of wharves or overhanging
rocks. As they grow larger, they lose something
of their gregarious disposition, — they scatter

ALTERNATE GENERATIONS. 255

more ; and at this time they prefer the sunniest
exposures, and like to bask in the light and
warmth. They assume every variety of attitude,
but move always by the regular contraction and
expansion of the disk, which rises and falls with
rhythmical alternations, the average number of
these movements being from twelve to fifteen in
a minute. There can be no doubt that they
perceive what is going on about them, and are
very sensitive to changes in the state of the
atmosphere ; for, as soon as the surface of the
water is ruffled, or the sky becomes overcast,
they sink into deeper water, and vanish out of
sight. When approached with a dip-net, it is
evident, from the acceleration of their move-
ments, that they are attempting to escape.

At the spawning season, toward the end of
July or the beginning of August, they gather
again in close clusters. At this period I have
seen them at Nahant in large shoals, covering a
space of fifty feet or more, and packed so closely
in one unbroken mass that an oar could not be
thrust between them without injuring many. So
deep was the phalanx that I could not ascertain
how far it extended below the surface of the
water, and those in the uppermost layer were
partially forced out of the water by the pressure
of those below.

It is not strange that the relation between the

256 ALTERNATE GENERATIONS.

various phases of this extraordinary series of
metamorphoses, so different from each other in
their external aspects, should not have been
recognized at once, and that this singular Aca-
leph should have been called Scyphostoma in its
simple Hydroid condition (see p. 248), Strobila
after the transverse division of the body had taken
place (see p. 249), Ephyra in the first stages of
its free existence (see p. 251), and Aurelia in its
adult state (see pp. 252 and 254), — being thus
described as four distinct animals. These vari-
ous forms are now rightly considered as the suc-
cessive stages of a development intimately con-
nected in all its parts, — beginning with the
simple Hydroid attached to the ground, and clos-
ing in the shape of our common Aurelia, with
its white transparent disk, its silky fringe of
tentacles around the margin, its ruffled curtains
hanging from the mouth, and its four crescent-
shaped ovaries grouped to form a cross on the
summit. From these ovaries a new brood of
little embryos is shed in due time.

There are other Hydroids giving rise to Me-
dusa buds, from which, however, the Medusae
do not separate to begin a new life, but wither
on the Hydroid stock, after having come to ma-
turity and dropped their eggs. Such is the Hy-
dractinia polyclina. This curious community
begins, like the preceding ones, with a single

ALTERNATE GENERATIONS. 257

little individual, settling upon some shell or
stone, or on the rocks in a tide-pool, where it
will sometimes cover a space of several square
feet. Rosy in color, very soft and delicate in
texture, such a growth of Hydractinia spreads
a velvet-like carpet over the rocks on which it
occurs. They may be kept in aquariums with
perfect success, and for that purpose it is better'
to gather them on single shells or stones, so
that the whole community may be removed un-
broken. These colonies of Hydractinia have one.
very singular character : they exist in distinct
communities, some of which give birth only to
male, others to female individuals. The func-
tions, also, are divided, — certain members of
the community being appointed to special offices,
in which the others do not share. Some bear
the Medusae buds, which in due time become
laden with eggs, but, as I have said, wither and
die after the eggs are hatched. Others put forth
Hydroid buds only, while others again are wholly
sterile. About the outskirts of the community
are more simple individuals, whose whole body
seems to be hardly more than a double-walled
tube, terminating in a knob of lasso-cells. They
are like long tentacles placed where they can
most easily seize the prey that happens to ap
proach the little colony. The entire community
is connected at its base by a horny net-work,

Q

258

ALTERNATE GENERATIONS.

uniting all the Hydroid stems in its meshes,
and spreading over the whole surface on which
the colony has established itself.

Hydractinia polyclina : a, sterile individual ; 6, fertile individual, producing
female Medusae ; d, c, female Medusae, containing advanced eggs ; /, $r, A, i,
cluster of female Medusae, with less advanced eggs ; o, peduncle of mouth,
with short globular tentacles ; c, individual with globular tentacles, upon
which no Medusae have appeared, or from which they have dropped.

There is a very curious and beautiful animal,
or rather community of animals, closely allied
to the Hydractinia polyclina, which next de-
serves to be noticed. The Portuguese Man-of-
War — so called from its bright-colored crest,
which makes it so conspicuous as it sails upon
the water, and the long and various streamers
that hang from its lower side — is such a com-
munity of animals as I have just described, re-
versed in position, however, with the individuals
hanging down, and the base swollen and ex-
panded to make the air-bladder which forms its

ALTERNATE GENERATIONS.

259

brilliant crested float. In this curious Acale-
phian Hydroid, or Physalia, the individuality of
function is even more marked than in the Hy-

Physalia, or Portuguese Man-of-War.

dractinia. As . in the latter, some of the indi-
viduals are Medusae-bearing, and others simple

260 ALTERNATE GENERATIONS.

Hydrae ; but, beside these, there are certain mem-
bers of the community who act as swimmers, to
carry it along through the water, — others that
are its purveyors, catching the prey, by which,
however, they profit only indirectly, for others
are appointed to eat it, and these feeders may
be seen sometimes actually gorged with the food
they have devoured, and which is then distrib-
uted throughout the community by the process
of digestion and circulation.

It would be hopeless, even were it desirable,
to attempt within the limits of such an article
as this to give the faintest idea of the number
and variety of these Hydroids ; and I will there-
fore say nothing of the endless host of Tubula-
rians, Campanularians, Sertularians, etc. They
are very abundant along our coast, and will well
reward any one who cares to study their habits
and their singular modes of growth. For their
beauty, simply, it is worth while to examine
them. Some are deep red, others rosy, others
purple, others white with a glitter upon them
as if frosted with silver. Their homes are ver
various. Some like the fresh, deep sea- water
while they avoid the dash and tumult of the
waves ; and they establish themselves in the de-
pressions on some low ledge of rocks running
far out from the shore, and yet left bare for
an hour or two, when the tide is out. In -such

ALTERNATE GENERATIONS. 261

a" depression, forming a stony cup filled with
purest sea-water, and overhung by a roof of rock,
which may be • fringed by a heavy curtain of
brown sea-weed, the rosy-headed, branching Eu-
dendrium, one of the prettiest of the Tubula-
rians, may be found. Others choose the tide-
pools, higher up on the rocks, that are freshened
by the waves only when the tide is full : such are
the small, creeping Campanularians. Others,
again, like the tiny Dynamena, prefer the rougher
action of the sea ; and they settle upon the
sides of rents and fissures in the cliffs along the
shore, where even in calm weather the waves
rush in and out with a certain degree of violence,
broken into eddies by the abrupt character of
the rocks. Others seek the broad fronds of the
larger sea-weeds, and are lashed up and down
upon their spreading branches, as they rock to
and fro with the motion of the sea. Many live
in sheltered harbors, attaching themselves to
floating logs, or to the keels of vessels ; and some
are even so indifferent to the freshness of the
water that they may be found in numbers along
the city-wharves.*

Beside the Jelly-Fishes arising from Hydroids,

* Those who care to know more of the habits and structure of
these animals will find detailed descriptions of all the various species
of our coast, illustrated by numerous plates, in the fourth volume of
my Contributions to the Natural History of the United States, pub-
lished, some time ago.

262 ALTERNATE GENERATIONS.

there are many others resembling these in all
the essential^ features of their structure, but dif-
fering in their mode of development ; for, al-
though more or less Polyp-like when first born
from the egg, they never become attached, nor
do they ever bud or divide, but reach their mature
condition without any such striking metamor-
phoses as those that characterize the develop-
ment of the Hydroid Acalephs. All the Medusae,
whether they arise from buds on the Hydroid
stock, like the Sarsia, or from transverse division
of the Hydroid form, like the Aurelia, or grow
directly from the egg to maturity, without paus-
ing in the Hydroid phase, like the Campanella,
agree in the general division and relation of
parts. All have a central cavity, from which
arise radiating tubes extending to the margin
of the umbrella-like disk, where they unite either
in a net-work of meshes or in a single circular
tube. But there is a great difference in the
oral apparatus ; the elaborate ruffled curtains,
that hang from the corners of the mouth, occur
only in the Species arising from the transverse
division of the Polyp-like young. For this rea-
son they are divided into two Orders, — the Hy-
droids and the Discophorae.

The third order, the Ctenophorae, are among
the most beautiful of the Acalephs. I have spo-
ken of the various hues they assume when in

ALTERNATE GENERATIONS.

263

motion, and I will add one word of the peculiar-
ity in their structure which causes this effect.
The CtenophoraD differ from the Jelly-Fishes de-
scribed above in sending off from the main cavity
only two main tubes, instead of four like the
others ; but each of these tubes divides and sub-
divides in four branches as it approaches the pe-
riphery. From the eight branches produced in
this way there arise vertical tubes extending in

Idyia roseola ; one of our Ctenophorae : a, anal aperture 5 &, radiating tube ;
c, circular tube 5 d, e,f, g, fi, rows of locomotive fringes.

opposite directions up and down the sides of
the body. Along these vertical tubes run the
rows of little locomotive oars, or combs, as they
have been called, from which these animals derive
their name of Ctenophorae. The rapid motion
of these flappers causes the decomposition of the
rays of light along the surface of the body, pro-
ducing the most striking prismatic effect ; and it
is no exaggeration to say that no jewel is brighter

264 ALTERNATE GENERATIONS.

than these Ctenophorae as they move through the
water.*

I- trust I have succeeded in showing that the
three Orders of the Acalephs are, like the five
Orders of the Echinoderms, different degrees of
complication of the same structure. In the Hy-
droids, the organization does not rise above the
simple digestive cavity enclosed by tlie double
body-wall ; and we might not suspect their rela-
tion to the Acalephs, did we not see the Jelly-
Fish born from the Hydroid stock. In the Hy-
droid-Medusae and Discophorae, instead of a sim-
ple digestive sac, &s in the Hydroids, we have a
cavity sending off tubes toward the periphery,
which ramify more or less in their course. Now
whether there are four tubes or eight, whether
they ramify extensively or not, whether there are
more or less complicated appendages around the
margin or the mouth, makes no difference in the
essential structure of these bodies. They are all
disk-like in outline, they all have tentacles hang-
ing from the margin, and a central cavity from
which tubes diverge that divide the body into a
certain number of segments, bearing in all the
same relation to each other and to the central
cavity. In the Ctenophorae, another complication
of structure is introduced in the combination of

* For more details concerning the Ctenophorae, see the third
volume of my Contributions.

ALTERNATE GENERATIONS. 265

vertical with horizontal tubes and the external
appendages accompanying them.

But, whatever their differences may be, a very
slight effort of the imagination only is needed to
transform any one of these forms into any other.
Reverse the position of any simple Hydra, so that
the tentacles hang down from the margin, and
let four tubes radiate from the central cavity to
the periphery, and we have the lowest form of
Jelly-Fish. Expand the cup of the Hydra to
form a gelatinous disk, increase the number of
tubes, complicate their ramifications, let eyes
be developed along the margin, add some exter-
nal appendages, and we have the Discophore.
Elongate the disk in order to give the body an
oval form, diminish the number of main tubes,
and let them give off vertical as well as horizontal
branches, and we have the Ctenophore.

In the Class of Polyps there are but two Or-
ders, — the Actinoids and the Halcyonoids ; and
I have already said so much of the structure of
Polyps that I think I need not repeat my remarks
here in order to show the relation between these
groups. The body of all Polyps consists of a
sac divided into chambers by vertical partitions,
and having a wreath of hollow tentacles around
the summit, each one of which opens into one of
the chambers. The greater.complication of these
parts and their limitation in definite numbers
12

266 ALTERNATE GENERATIONS.

constitute the characters upon which their supe-
riority or inferiority of structure is based. Here
the comparison is easily made ; it is simply the
complication and number of identical parts that
make the difference between the Orders. The
Actinoids stand lowest from the simple character
and indefinite increase of these parts ; while the
Halcyonoids, with their eight lobed tentacles,
corresponding to the same number of internal
divisions, are placed above them.

In the name of the division to which they all
belong we have the key-note to the common
structure of the three Classes whose Orders we
have been comparing : they are Radiates. The
idea of radiation lies at the foundation of all these
animals, whatever be their form or substance.
Whether stony, like the Corals, or soft, like the
Sea-Anemone, or gelatinous and transparent, like
the Jelly-Fish, or hard and brittle, like the Sea-
Urchins, — whether round or oblong or cylin-
drical or stellate, their internal structure always
obeys this law of radiation.

Not only is this true in a general way, but the
comparison may be traced in all the details.
One may ask how the narrow radiating tubes of
the Acalephs, traversing the gelatinous mass of
the body, can be compared to the wide radiating
chambers of the Polyp ; and yet nothing is more
simple than to thicken the partitions in the

ALTERNATE GENERATIONS. 267

Polyps sc much as to contract the chambers
between them, till they form narrow alleys in-
stead of wide spaces, and then we have the tubes
of the Jelly-Fish. In the Jelly-Fish there is a
circular tube around the margin, into which all
the radiating tubes open. What have we to
compare with this in the Polyps ? The outer
edge of each partition in the Polyp is pierced by
a hole near the margin. Of course when the
partition is thickened, this hole, remaining open,
becomes a tube ; for what is a tube but an
elongated hole ? The comparison of the Aca-
lephs with the Echinoderms is still easier, for
they both have tubes ; but in the latter the tubes
are enclosed in walls of their own, instead of
traversing the mass of the body, as in Aca-
lephs, etc.

In preparing these chapters on the homologies
of Radiates, I have felt the difficulty of divesting
my subject of the technicalities which cling to all
scientific results, until they are woven into the
tissue of our every-day knowledge and assume
the familiar ga,rb of our common intellectual
property. When the forms of animals are as
familiar to children as their ABC, and the
intelligent study of Natural History, from the
objects themselves, and not from text-books
alone, is introduced into all our schools, we

268 ALTERNATE GENERATIONS.

x

shall have popular names for things that can
now only be approached with a certain profes-
sional stateliness on account of their technical
nomenclature. The best result of such familiar-
ity with Nature will be the recognition of an
intellectual unity holding together all the vari-
ous forms of life as parts of one Creative Con-
ception.

THE OVARIAN EGG. 269

CHAPTER XV.

THE OVARIAN EGG.

ALL important changes in the social and politi-
Octl condition of man, whether brought about by
violent convulsions or effected gradually, are at
once recognized .as eras in the history of human-
ity. But on the broad high-road of civilization
along which men are ever marching, they pass by
unnoticed the landmarks of intellectual progress,
unless they chance to have some direct bearing
on what is called the practical side of life. Such
an era marked the early part of our own century ;
and though at the time a thousand events seemed
more full-freighted for the world than the dis-
covery of some old bones in the quarries of Mont-
martre, and though many a man seemed greater
in the estimation of the hour than the professor
at the Jardin des Plantes who strove to reconstruct
these fragments, yet the story that they told
lighted up all the past, and showed its true con-
nection with the present.

Before the year 1800, men had never suspected
that their home had been tenanted in past times

270 THE OVARIAN EGG.

by a set of beings totally different from those
that inhabit it now ; still farther was it from their
thought to imagine that creation after creation
had followed each other in successive ages, every
one stamped with a character peculiarly its own.
It was Cuvier who, aroused to new labors by the
hint he received from the bones unearthed at
Montmartre, to which all his vast knowledge of
living animals gave him no clew, established by
means of most laborious investigations the as-
tounding conclusion, that, prior to the existence
of the animals and plants now living, this globe
had been the theatre of another set of beings,
every trace of which had vanished from the face
of the earth. To his alert and active intellect,
and powerful imagination, a word spoken out of
the past was pregnant with meaning ; and when
he had once convinced himself that he had found
a single animal that had no counterpart among
living beings, it gave him the key to many mys-
teries. The existence of a past creation once
suggested, confirmation was found in a thousand
facts overlooked before. The solid crust of the
earth gave up its dead, and from the snows of
Siberia, from the soil of Italy, from caves of Cen-
tral Europe, from mines, from the rent sides of
mountains and from their highest peaks, from
the coral beds of ancient oceans, the varied ani-
mals that had possessed the earth, ages before
man was created, spoke to us of the past.

THE OVARIAN EGG. 271

No sooner were these facts established, than
the relation between the extinct world and the
world of to-day became the subject of extensive
researches and comparisons ; innumerable theo-
ries were started to account for the differences,
and to determine the periods and manner of the
change ; and the science of Paleontology became
one of the most important departments of inves-
tigation in modern times. It is not my intention
to enter now at any length upon the subject of
geological succession, though I hope to return to
it hereafter in a series of papers upon that and
kindred topics ; but I allude to it here, before
presenting some views upon the maintenance of
organic types as they exist in our own period, for
the following reason. Since it has been shown
that from the beginning of Creation till the pres-
ent time the physical history of the world has
been divided into a succession of distinct periods,
each one accompanied by its characteristic ani-
mals and plants, so that our own epoch is only
the closing one in a long procession of ages,
naturalists have been constantly striving to find
the connecting link between them all, and to
prove that each such creation has been a normal
and natural growth out of the preceding one.
With this aim they have tried to adapt the phe-
nomena of reproduction among animals to the
problem of creation, and to make the beginning

272 THE OVARIAN EGG.

of life in the individual solve that great mystery
of the beginning of life in the world. In other
words, they have endeavored to show that the
fact of successive generations is analogous to that
of successive creations, and that the processes by
which animals, once created, are maintained un-
changed during the period to which they belong,
will account also for their primitive existence.

I wish, at the outset, to forestall any such mis-
application of the facts I am about to state, and
to impress upon my readers the difference between
these two subjects of inquiry, since it by no means
follows, that, because individuals are endowed
with the power of reproducing and perpetuating
their kind, they are in any sense self-originating.
Still less probable does this appear, when we con-
sider, that, since man has existed upon the earth,
no appreciable change has taken place in the ani-
mal or vegetable world ; and so far as our knowl-
edge goes, this would seem to be equally true of
all the periods preceding ours, each one maintain-
ing unbroken to its close the organic character
impressed upon it at the beginning.

The question I propose to consider here is
simply the mode by which organic types are pre-
served as they exist at present. Every one has a
summary answer to this question in the state-
ment that all these short-lived individuals repro-
duce themselves, and thus maintain their kinds.

THE OVARIAN EGG. 273

But the modes of reproduction are so varied,
the changes some animals undergo during their
growth so extraordinary, the phenomena accom-
panying these changes so startling, that, in the
pursuit of the subject, a new and independent
science — that of Embryology — has grown up,
of the utmost importance in the present state of
our knowledge.

The prevalent ideas respecting the reproduction
of animals are^made up from the daily observation
of those immediately about us, in the barn-yard
and on the farm. But the phenomena here are
comparatively simple and easily traced. The mo-
ment, however, we extend our observations beyond
our cattle and fowls, and enter upon a wider field
of investigation, we are met by the most startling
facts. Not the least baffling of these are the dis-
proportionate numbers of males and females in
certain kinds of animals, their unequal develop-
ment, as well as the extraordinary difference be-
tween the sexes among certain species, so that
they seem as distinct from each other as if they
belonged to separate groups of the Animal King-
dom. We have close at hand one of the most
striking instances of disproportionate numbers in
the household of the Bee, with its one fertile fe-
male charged with the perpetuation of the whole
community, while her innumerable sterile sister-
hood, amid a few hundred drones, contribute to

12* H

274 THE OVARIAN EGG.

its support in other ways. Another most inter-
esting chapter connected with the maintenance of
animals is found in the various methods and dif-
ferent degrees of care with which they provide for
their progeny : some having fulfilled their whole
duty toward their offspring when they have given
them birth, while others seek hiding-places for
the eggs they have laid, and watch with a certain
care over their development, and still others feed
their young till they can provide for themselves,
or build nests, or burrow holes in the ground, or
construct earth mounds for their shelter, and by
a variety of means secure them from possible
dangers.

But, whatever be the difference in the outward
appearance or the habits of animals, one thing is
common to them all without exception : at some
period of their lives they produce eggs, which,
being fertilized, give rise to beings of the same
kind as the parent. This mode of generation is
universal, and is based upon that harmonious
antagonism between the sexes, that contrast be-
tween the male and the female element, that at
once divides and unites the whole Animal King-
dom. And although this exchange of influence
is not kept up by an equality of numeric relations,
— since not only are the sexes very unequally
divided in some kinds of animals, but the male
and female elements are even combined in cer-

THE OVARIAN EGG. 275

tain types, so that the individuals are uniformly
hermaphrodites, — yet I firmly believe that this
numerical distribution, however unequal it may
seem to us, is not without its ordained accuracy
and balance. He who has assigned its place to
every leaf in the thickest forest, according to an
arithmetical law which prescribes to each its al-
lotted share of room on the branch where it grows,
will not have distributed animal life with less
care and regularity.

Although reproduction by eggs is common to
all animals, it is only one among several modes
of multiplication. We have seen that certain
animals, besides the ordinary process of genera-
tion, also increase their numbers naturally and
constantly by self-division, so that out of one in-
dividual many individuals may arise by a natural
breaking up of the whole body into distinct sur-
viving parts. This process of normal self-division
may take place at all periods of life : it may form
an early phase of metamorphosis, as in the Hy-
droid of our common Aurelia, described in the
last article ; or it may even take place before the
young is formed in the egg. In such a case, the
egg itself divides into a number of portions, —
two, four, eight, or even twelve and sixteen in-
dividuals being normally developed from every
egg, in consequence of this singular process of
segmentation of the yolk, which takes place,

276 THE OVARIAN EGG.

indeed, in all eggs, but in those which produce
but one individual is only a stage in the natural
growth of the yolk during its transformation into
a young embryo. As the facts here alluded to
are not very familiar, even to professional natural-
ists, I may be permitted to describe them more
in detail.

No one who has often walked across a sand-
beach in summer can have failed to remark what
the children call " sand saucers." The name is
not a bad one, with the exception that the saucer
lacks a bottom ; but the form of these circular
bands of sand is certainly very like a saucer with
the bottom knocked out. Hold one of them
against the light and you will see that it is com-
posed of countless transparent spheres, each of
the size of a small pin's head. These are the
eggs of our common Natica or Sea-Snail. Any
one who remembers the outline of this shell will
easily understand the process by which its eggs
are left lying on the beach in the form I have
described. They are laid in the shape of a broad,
short ribbon, pressed between the mantle of the
animal and its shell, and, passing out, they cover
the exterior of the shell, over which they are
rolled up, with a kind of glutinous envelope, —
for the eggs are held together by a soft gluti-
nous substance. Thus surrounded, the Natica,
whose habit is to burrow under the surface of

THE OVARIAN EGO. 277

the beach, soon covers itself with sand, the par-
ticles of which, in contact with the glutinous
substance of the eggs, quickly form a cement
that binds the whole together in a kind of paste.
When consolidated, it drops off from the shell,
having taken the mould of its form, as it were,
and retaining the curve which distinguishes the
outline of the Natica. Although these saucers
look perfectly round, it will be found that the
edges are not soldered together, but are simply
lapped one .over the other. Every one of the
thousand little spheres crowded into such a circle
of sand contains an egg. If we follow the develop-
ment of these eggs* we shall presently find that
each one divides into two halves, these again
dividing to make four portions, then the four
breaking up into eight, and so on, till we may
have the yolks divided into no less than sixteen
distinct parts. Thus far this process of segmen-
tation is similar to that of the egg in other ani-
mals ; but, as we shall see hereafter, the regular
segmentation of an egg seems usually to re-
sult only in a change in the quality of its sub-
stance, for the portions coalesce again to form
one mass, from which a new individual is finally
sketched out, as a simple embryo at first, but
gradually undergoing all the changes peculiar
to its kind, till a new-born animal escapes from
the egg. In the case of the Natica, however, this

278 THE OVARIAN EGG.

regular segmentation changes its character, and
at a certain period, in a more or less advanced
stage of the segmentation, according to the species,
each portion of the yolk assumes an individuality
of its own, and, instead of uniting again with the
rest, begins to subdivide for itself. In our Natica
her os, for instance, the common large gray Sea-
Snail of our coast, this change takes place when
the yolk has subdivided into eight or sixteen
parts. At that time each portion begins a life of
its own, not reuniting with its twin portions ; so
that in the end, instead of a single embryo grow-
ing out of this yolk, we have from eight to six-
teen embryos arising from a single yolk, each
one of which undergoes a series of develop-
ments similar in all respects to that by which
a single embryo is formed from each egg in
other animals. We have other Naticas in which
the normal number is twelve; others, again, in
which no less than thirty-two individuals arise
from one yolk. But this process of segmenta-
tion, though in these animals it leads to such a
multiplication of individuals, is exactly the same
as that discovered by K. E. von Baer in the egg
of the Frog, and described and figured by Pro-
fessor Bischoff in the egg of the Rabbit, the Dog,
the Guinea-Pig, and the Deer ; while other em-
bryologists have traced the same process in Birds,
Reptiles, and Fishes, as well as in a variety of
Articulates, Mollusks, and Radiates.

THE OVARIAN EGG. 279

Multiplication by division occurs also normally
in adult animals that have completed their growth.
This is especially frequent among Worms ; and
strange to say, there are species in this Class
which never lay eggs before they have already
multiplied themselves by self-division.

Another mode of increase is that by budding,
as in the Corals and many other Radiates. The
most common instance of budding we do not,
however, generally associate with this mode of
multiplication in the Animal Kingdom, because
we are so little accustomed to compare and gen-
eralize upon phenomena which we do not see to
be directly connected with one another. I allude
here to the budding of trees, which year after
year enlarge by the addition of new individuals
arising from buds. It must be remembered here
that I use the word individual simply in its scien-
tific sense, as designating singleness of existence,
and I trust that its usual acceptation will not
prevent a correct appreciation of the true re-
lation of buds to their parents and to the beings
arising from them. All buds have the same
organic significance, whether they drop from the
parent stock to become distinct individuals in the
common acceptation of the term, or remain con-
nected with the parent stock, as in Corals and in
trees, thus forming growing communities of com-
bined individuals. Nor will it matter much in

280 THE OVARIAN EGG.

connection with the subject under discussion,
whether these buds start from the surface of an
animal or sprout in its interior, to be cast off in
due time. Neither is the inequality of buds,
varying more or less among themselves, any
sound reason for overlooking their essential iden-
tity of structure. We have seen instances of this
among Acalephs, and it is still more apparent
among trees which produce simultaneously leaf
and flower buds, and even separate male and
female flower-buds, as is the case with our Hazels,
Oaks, etc.

It is not, however, my purpose here to de-
scribe the various modes of reproduction and
multiplication among animals and plants, nor to
discuss the merits of the different opinions re-
specting their numeric increase, according to
which some persons hold that all types originated
from a few primitive individuals, while others
believe that the very 'numbers now in existence
are part of the primitive plan, and essential to
the harmonious relations existing between the
animal and vegetable world. 'I would only at-
tempt to show that in the plan of Creation the
maintenance of types has been secured through
a variety of means, but under such limitations,
that, within a narrow range of individual differ-
ences, all representatives of one kind of animals
agree with one another, whether derived from

THE OVARIAN EGG. 281

eggs, or produced by natural division, or by
budding ; and that the constancy of these normal
processes of reproduction, as well as the uni-
formity of their results, precludes the idea that
the specific differences among animals have been
produced by the very means that secure their
permanence of type. "The statement itself im-
plies a contradiction, for it assumes that the same
influences prevent and produce changes in the
condition of the Animal Kingdom. Facts are all
against such an assumption ; there is not a fact
known to science tending to show that any being,
in the natural process of reproduction and multi-
plication, has ever diverged from the course nat-
ural to its kind, or that a single kind has ever
been transformed into any other. But this once
established, and setting aside the idea that Em-
bryology is to explain to us the origin as well
as the maintenance of life, it yet has most im-
portant lessons for us, and the field it covers
is constantly enlarging as the study is pursued.
The first and most important result of the
science of Embryology was one for which the
scientific world was wholly unprepared. Down
to our own century, nothing could have been
farther from the conception of anatomists and
physiologists than the fact, now generally admit-
ted, that all animals, without exception, arise
from eggs. Though Linnaeus had already ex-

282 THE OVARIAN EGG.

pressed this great truth in the sentence so often
quoted, — " Omne vivum ex ovo," — yet he was
not himself aware of the significance of his own
statement, for the existence of the Mammalian
egg was not then dreamed of. Since then the
discoveries of Von Baer and others have shown
not only that the production of eggs is common
to all living beings without exception, from the
lowest Radiate to the highest Vertebrate, but
that their structure is at first identical in all,
composed of the same primitive elements, and
undergoing exactly the same process of growth
up to the time when they assume the special
character peculiar to their kind. This is un-
questionably one of the most comprehensive gen-
eralizations of modern times.

In common parlance, we understand by an
egg something of the nature of a hen's egg, a
mass of yolk surrounded with white and enclosed
in a shell. But to the naturalist, the envelopes
of the egg, which vary greatly in different ani-
mals, are mere accessories, while the true egg,
or, as it is called, the ovarian egg, with which the
life of every kind of living beings may begin, is
a minute sphere, uniform in appearance through-
out the Animal Kingdom, though its intimate
structure is hardly to be reached even with the
highest powers of the microscope. Some account
of these earlier stages of growth in the egg may

THE OVARIAN EGG. 283

not be uninteresting to my readers. I will take
the egg of the Turtle as an illustration, since
that has been the subject of my own especial
study ; but, as I do not intend to carry my re-
marks beyond the period during which the his-
tory of all vertebrate eggs is the same, they may
be considered of more general application.

It is well known that all organic structures,
whether animal or vegetable, are composed of
cells. These cells consist of an outside bag en-
closing an inner sac, within which there is a dot.
The outer bag is filled with a more or less trans-
parent fluid, and the inner one generally with a
more perfectly transparent fluid, while the dot
has a dark appearance. In the language of our
science, the outer envelope is called the Ecto-
blast, the inner sac the Mesoblast, and the dot
the Entoblast. Although they are peculiarly
modified to suit the different organs, these cells
never lose this peculiar structure ; it may be
traced even in the long drawn-out cells of the
flesh, which are like mere threads, but yet have,
at least while forming, their outer and inner sac
and their dot.

In the Turtle the ovary is made up of such
cells, spherical at first, but becoming hexagonal
under pressure, when they are more closely
packed together. Between these ovarian cells
the egg originates, and is at first a mere granule,

284 THE OVARIAN EGG.

so minute, that, when placed under a very high
magnifying power, it is but just visible. This
is the incipient egg, and at this stage it differs
from the surrounding cells only in being some-
what darker, like a drop of oil, and opaque,
instead of transparent and clear like the sur-
rounding cells. Under the microscope it is found
to be composed of two substances only : namely,
oil and albumen. It increases gradually, and
when it has reached a size at which it requires
to have its diameter magnified one thousand
times in order to be distinctly visible, the outside
assumes the aspect of a membrane thicker than
the interior and forming a coating around it.
This is owing, not to an addition from outside,
but to a change in the consistency of the sub-
stance at the surface, which becomes more closely
united, more compact, than the loose mass in the
centre. Presently we perceive a bright, lumi-
nous, transparent spot on the upper side of the
egg, near the wall or outer membrane. This is
produced by a concentration of the albumen,
which now separates from the oil and collects at
the upper side of the egg, forming this light spot,
called by naturalists the Purkinjean vesicle, after
its discoverer, Purkinje. When this albuminous
spot becomes somewhat larger, there arises a
little dot in the centre, — the germinal dot, as it
is called. And now we have a perfect cell-struc-

THE OVARIAN EGG. 285

ture, differing from an ordinary cell only in
having the inner sac, enclosing the dot, on the
side, instead of in the centre. The outer mem-
brane corresponds to the Ectoblast, or outer cell
sac, the Purkinjean vesicle to the Mesoblast, or
inner cell sac, while the dot in the centre an-
swers to the Entoblast. When the Purkinjean
vesicle has completed its growth, it bursts and
disappears ; but the mass contained in it remains
in the same region, and retains the same char-
acter, though 110 longer enclosed as before.

At a later stage of the investigation, we see
why the Purkinjean vesicle, or inner sac of the
egg, is placed on the side, instead of being at
the centre, as in the cell. It arises on that side
along which the axis of the little Turtle is to lie,
— the opposite side being that corresponding to
the lower part of the body. Thus, the lighter,
more delicate part of the substance of the egg
is collected where the upper cavity of the ani-
mal, enclosing the nervous system and brain, is
to be, while the heavy oily part remains beneath,
where the lower cavity, enclosing all the organs
of mere material animal existence, is afterwards
developed. In other words, when the egg is a
mere mass of oil and albumen, not indicating as
yet in any way the character of the future ani-
mal, and discernible only by the microscope, the
distinction is indicated between the brains and

286 THE OVARIAN EGG.

the senses, between the organs of instinct and
sensation and those of mere animal functions.
At that stage of its existence, however, when
the egg consists of an outer sac, an inner sac,
and a dot, its resemblance to a cell is unmis-
takable ; and, in fact, an egg, when forming, is
nothing but a single cell. This comparison is
important, because there are both animals and
plants which, during their whole existence, con-
sist of a single organic cell, while others are
made up of countless millions of such cells. Be-
tween these two extremes we have all degrees,
from the innumerable cells that build up the
body of the highest Vertebrate to the single-
celled Worm, and from the myriad cells of the
Oak to the single-celled Alga.

But while we recognize the identity of cell-
structure and egg-structure at this point in the
history of the egg, we must not forget the great
distinction between them, — namely, that while
the cells remain component parts of the whole
body, the egg separates itself, and assumes a dis-
tinct individual existence. Even now, while still
microscopically small, its individuality begins.
Other substances collect around it, are absorbed
into it, nourish it, serve it. Every being is a
centre about which many other things cluster
and converge, and which has the power to assimi-
late to itself the necessary elements of its life.

THE OVAKIAN EGG. 287

Every egg is already such a centre, differing from
the cells that surround it by no material elements,
but by the principle of life in which its individ-
uality consists, which is to make it a new being,
instead of a fellow-cell with those that build up
the body of the parent animal, and remain com-
ponent parts of it. This intangible something is
the subtile element that eludes our closest anal-
ysis ; it is the first indication of the immaterial
principle according to which the new being is to
develop. The physical germ we see ; the spirit-
ual germ we cannot see, though we may trace its
action on the material elements through which it
is expressed.

The first change in the yolk after the formation
of the Purkinjean vesicle is the appearance of
minute dots near the wall at the side opposite the
vesicle. These increase in number and size, but
remain always on that half of the yolk, leaving
the other half of the globe clear. One can hardly
conceive the beauty of the egg as seen through
the microscope at this period of its growth, when
the whole yolk is divided, with the dark granules
on one side ; while the other side, where the
transparent halo of the vesicle is seen, is brilliant
with light. With the growth of the egg these
granules enlarge, become more distinct, and un-
der the microscope some of them appear to be
hollow. They are not round in form, but rather

288 THE OVARIAN EGG.

irregular, and under the effect of light they are
exceedingly brilliant. Presently, instead of being
scattered equally over the space they occupy,
they form clusters, — constellations, as it were,
— and between these clusters are clear spaces,
produced by the separation of the albumen from
the oil.

At this period of its growth there is a wonder-
ful resemblance between the appearance of the
egg, as seen under the microscope, and the fir-
mament with the celestial bodies. The little
clusters or constellations are unequally divided.
Here and there they are two and two like double
stars, or sometimes in threes or fives, or in sevens,
recalling the Pleiades ; and the clear albuminous
tracks between are like the empty spaces separat-
ing the stars. This is no fanciful simile. It is
simply true that such is the actual appearance of
the yolk at this time ; and the idea cannot but
suggest itself to the mind, that the thoughts
which have been embodied in the universe are
recalled here within the little egg, presenting a
miniature diagram of the firmament. This is
one of the first changes of the yolk, ending by
forming regular clusters, with a sort of network
of albumen between, and then this phase of the
growth is complete.

Now the clusters of the yolk separate, and next
the albumen in its turn concentrates into clusters,

THE OVARIAN EGG. 289

and the dark bodies, which have been till now the
striking points, give way to the lighter spheres of
albumen between which the clusters are scattered.
Presently the whole becomes re-dissolved : these
stages of the growth being completed, this, little
system of worlds is melted, as it were ; but while
it undergoes this process, the albuminous spheres,
after being dissolved, arrange themselves in con-
centric rings, alternating with rings of granules,
around the Purkinjean vesicle. At this time we
are again reminded of Saturn and its rings, which
seems to have its counterpart here. These rings
disappear, and now once more out of the yolk
mass loom up little dots as minute as before ; but
they are round instead of angular, and those
nearest the Purkinjean vesicle are smaller and
clearer, containing less of oil than the larger and
darker ones on the opposite side. From this time
the yolk begins to take its color, the oily cells
assuming a yellow tint, while the albuminous
cells near the vesicle become whiter.

Up to this period the processes in the different
cells seem to have been controlled by the different
character of the substance of each ; but now it
would seem that the changes become more in-
dependent of physical or material influences, for
each kind of cell undergoes the same process.
They all assume the ordinary cell character, with
outer and inner sac, — the inner sac forming on
13 9

290 THE OVARIAN EGO.

the side, like the Purkinjean vesicle itself ; but it
does not retain this position, for, as soon as its
wall is formed and it becomes a distinct body, it
floats away from the side and takes its place in
the centre. Next there arise within it a number
of little bodies crystalline in form, and which
actually are wax or oil crystals. They increase
with great rapidity, the inner sac or mesoblast
becoming sometimes so crowded with them that
its shape is affected by the protrusion of their
angles. This process goes on till all the cells are
so filled by the mesoblast, with its myriad brood
of cells, that the outer sac or ectoblast becomes a
mere halo around it. Then every mesoblast con-
tracts ; the contraction deepens till it is divided
across in both directions, separating thus into
four parts, then into eight, then into sixteen, and
so on, till every cell is crowded with hundreds of
minute mesoblasts, each containing the indication
of a central dot or entoblast. At this period every
yolk cell is itself like a whole yolk ; for each cell
is as full of lesser cells as the yolk-bag itself.

When the mesoblast has become thus infinitely
subdivided into hundreds of minute spheres, the
ectoblast bursts, and the new generations of cells
thus set free collect in that part of the egg where
the embryonic disk is to arise. This process of
segmentation continues to go on downward till
the whole yolk is taken in. These myriad cells

THE OVARIAN EGG. 291

are, in fact, the component parts of the little Turtle
that is to be. They, will undergo certain modi-
fications, to become flesh-cells, blood-cells', brain-
cells, and so on, adapting themselves to the dif-
ferent organs they are to build up ; but they have
as much their definite and appointed share in the
formation of the body now as at any later stage
of its existence.

We are so accustomed to see life maintained
through a variety of complicated organs, that we
are apt to think this the only way in which it can
be manifested ; and, considering how entirely the
life of an adult animal is dependent upon the
organs through which it is sustained, it is natu-
ral that we should be deeply impressed by their
connection. But embryological investigations
have taught us that during the incipient growth
of the higher animals none of these organs exist,
and yet the principle of life is active, and even
after the organs are formed, they cannot act at
once, most of them being enclosed in the whole
structure, in a way which interferes with their
later functions. In the little Chicken, for in-
stance, before it is hatched, the lungs cannot
breathe, for they are surrounded by a fluid ; the
senses are inactive, for they receive no impres-
sions from without, and all those functions estab-
lishing its relations with the external world lie
dormant, for as yet they are not needed. But

292 THE OVARIAN EGG.

the organs are there, though, as we have seen in
the Turtle's egg, they were not there at the be-
ginning. How, then, are they formed ? Wo
may answer, that the first function of every or-
gan is to make itself. The building material is,
as it were, provided by the process which divides
the yolk into innumerable cells, and by the grad-
ual assimilation and modification of this material
the organs arise. Before the lungs breathe, they
make themselves ; before the stomach digests, it
makes itself; before the organs of the senses act,
they make themselves ; before the brain thinks,
it makes itself. In a word, before the whole
system works, it makes itself out of the elements
given by the formation of independent eggs : its
first office is self-structure.

At the period described above, however, when
the new generations of cells are just set free and
have taken their place in the region where the
new being is to develop, nothing is to be seen of
the animal whose life is beginning there, except
the filmy disk lying on the surface of the yolk.
Next come the layers of white or albumen around
the egg, and last the shell which is formed from
the lime in the albumen. There is always more
or less of lime in albumen, and the hardening of
the last layer of white into shell is owing only to
the greater proportion of lime in its substance.
In the layer next to the shell there is enough of

THE OVARIAN EGG. 293

lime to consolidate it slightly, and it forms a
membrane ; yet the white, the membrane, and
the shell have all the same quality, except that
the proportion of lime is more or less in the dif-
ferent layers.

But, as I have said, the various envelopes of
eggb, the presence or absence of a shell, and the
absolute size of the egg, are accessory features,
belonging not to the egg as egg, but to the spe-
cial kind of being from which the egg has arisen,
and into which it is to develop. What is common
to. all eggs and essential to them all is that which
corresponds to the yolk in the bird's egg. But
their later mode of development, the degree of
perfection acquired by the egg and germ before
being laid, the term required for the germ to
come to maturity, as well as the frequency and
regularity of the broods, are all features varying
with the different kinds of animals. There are
those that lay eggs once a year, at a particular
season, and then die ; so that their existence may
be compared to that of annual plants, undergo-
ing their natural growth in a season, to exist
during the remainder of the year only in the
form of an egg or seed. The majority of Insects
belong to this category, as do also our large
Jelly-Fishes ; many others have a slow growth,
extending over several years, during which they
reach their maturity, and for a longer or shorter

294 THE OVARIAN EGG.

time produce broods at fixed intervals ; wliilo
others, again, reach their mature state very rap-
idly, and produce a number of successive genera-
tions in a comparatively short time, it may be
in a single season.

I do not intend to enter upon the chapter of
special differences of development among ani-
mals, for in this article I have aimed only at
showing that the egg lives, that it is itself the
young animal, and that the vital principle is active
in it from the earliest period of its existence. But
I would say to all young students of Embryology
that their next aim should be to study those in-
termediate phases in the life of a young animal,
when, having already acquired independent exist-
ence, it has not yet reached the condition of the
adult. Here lies an inexhaustible mine of valu-
able information unappropriafed, from which, as
my limited experience has already taught me,
may be gathered the evidence for the solution of
the most perplexing problems of our science.
Here we shall find the true tests by which to de-
termine the various kinds and different degrees
of affinity which animals now living bear not
only to one another, but also to those that have
preceded them in past geological times. Here we
shall find not a material connection by which
blind laws of matter have evolved the whole
creation out of a single germ, but the clew to that

THE OVARIAN EGG. 295

intellectual conception which spans the whole
series of geological ages, and is perfectly consist-
ent in all its parts. In this sense the present
will indeed explain the past, and the young
naturalist is happy who enters upon his life of
investigation now, when the problems that were
dark to all his predecessors have received new
light from the sciences of Paleontology and
Embryology.

296 EMBRYOLOGY AND CLASSIFICATION.

CHAPTER XVI.

EMBRYOLOGY AND CLASSIFICATION.

THE investigation of the structure and gradual
growth of the ovarian egg is so laborious that
it will be many years before we can hope to
have a complete picture of all its phases. The
apparatus required for the task is very compli-
cated, and a long training is necessary merely
to prepare the student for the use of his instru-
ments. A superficial familiarity with the mi-
croscope gives no idea of the exhausting kind
of labor which the naturalist must undergo
who would make an intimate microscopic study
of these minute living spheres. The glance at
the moon, or at Jupiter's satellites, which the
chance visitor at an observatory is allowed to
take through the gigantic telescope, reveals to
him nothing of the intense concentrated watch-
ing by which the observer wins his higher re-
ward. The nightly vision of the astronomer,
revealing myriad worlds in the vague nebulous,
spaces of heaven, is not for him ; he must take
the great results of astronomy for granted, si

EMBRYOLOGY AND CLASSIFICATION. 297

no man capable of original research has the
time to prepare for the uninitiated the attendant
circumstances essential to his more difficult in-
vestigations, or to train their eyes to see what
he sees. So is it also with the microscopic
observer ; the deeper insight he has gained by
long training in steadiness of hand and eye, as
well as in the concentration of intellect that
makes the brain work harmoniously with them,
he cannot communicate. He 'may interest and
amuse his friends and visitors with some easy
exhibition of specimens under the microscope ;
he may open the door into the laboratory of
Nature, but he cannot invite them to cross the
threshold or to enter in with him. I think
people are not generally aware of the difficulty
of microscopic observation, or the amount of
painful preparation required merely to fit the
organs of sight and touch for the work. In old
times men prepared themselves with fast and
vigil for entrance into the temple ; and Nature
does not «open her sanctuary without exacting
due penance from her votaries. It seems an
easy matter for a man to sit down and look at
objects through a glass which enlarges every-
thing to his vision ; but there are subjects of
microscopic research so obscure that the student
must observe a special diet before undertaking
his investigation, in order that even the beating

13*

298 EMBRYOLOGY AND CLASSIFICATION.

of his arteries may not disturb the steadiness
of his gaze, and the condition of his nervous
system be so calm that his whole figure will re
main for hours in rigid obedience to his fixed
and concentrated gaze.

After these remarks I trust I shall not be mis-
understood by those who have been working in
the field of microscopic investigation, and for
whose persevering devotion no one can feel a
deeper reverence than I do, if I add that there
is as yet hardly a beginning in the study of the
egg during its growth, and anterior to the for-
mation of the germ. Since Embryology became
a science, the great aim of students in that de-
partment has been to demonstrate the uniform
structure of the egg in all animals, and investi-
gators have limited their observations to that
stage of the ovarian egg during which it ap-
pears in all animals as a perfect cell. .But a
new field now opens before us, requiring a care-
ful survey of every stage of growth of the egg,
from its first formation to the period when a
well-defined germ is developed. The growth of
the egg during this period requires to be studied
as minutely through all its changes, and in the
various combinations of its constitutive elements,
as the germ itself has been in its later trans-
formations. Here again, in this later phase,
another field presents itself equally new and

EMBRYOLOGY AND CLASSIFICATION. 299

full of promise. Embryologists have generally
considered their work as complete when they
have traced the new being to a point at which
it resembles somewhat any of the members of
the natural group to which it belongs. The
process by which the gradual completion of the
whole frame is attained has been assumed to
be one of little interest, hardly deserving the
careful scrutiny of the embryologist ; while the
zoologist has also overlooked, or regarded as of
little importance, the differences which still dis-
tinguish the young from the adult, even after
its typical characters are perfectly distinct. Yet
naturalists might have taken a. hint from one
class of Vertebrates long known for their pecu-
liar metamorphoses, and which show how im-
portant are the facts to be learned from these
early stages in the life of any animal.

More than a century ago Roesel, in his masterly
work on the Frogs and Toads of Germany, repre-
sented the mode of reproduction and growth
of these animals with a remarkable degree of
accuracy, and this subject has since been traced
with additional precision and minuteness by Rus-
eoni, Yon Siebold, and Funke. Notwithstanding
this, no special application has yet been made
of the results of these investigations to the clas-
sification of these animals, beyond the general
recognition that the caudate Batrachians, with

800 EMBRYOLOGY AND CLASSIFICATION

permanent external gills, rank lower than the
Salamanders, which lose their gills in the adult
condition, while these again are inferior to the
Frogs and Toads, in which the tail also is resorbcd
before the animal completes its growth. But
the comparison of the higher and lower Ba-
trachians should not stop here. A more exten-
sive examination shows that the Tadpole begins
as an elongated body, not only without legs,
but also without external gills, and that it passes
to a branchiate condition, with more or less de-
veloped legs, before it loses the gills, while there
are various modes of development of the limbs
themselves, — various phases in the formation
of the tail, in its growth and resorption ; vari-
ous phases also in the formation of the fingers,
up to their final separation, in* those which are
destitute, in their adult condition, of any web
between them. This gradation is so complete,
that if we follow all the phases of development
of the several representatives of this class, so
common everywhere in our temperate zone, we
cannot fail to perceive that the changes these
animals undergo during their growth furnish a
complete scale ; and if we now compare this
scale with one founded upon the various degrees
of structural complication in the adult repre-
sentatives of the class, we find that these two
series agree perfectly ; so that Nature herself

EMBRYOLOGY AND CLASSIFICATION.

furnishes us with a classification, to establish
which needs no arbitrary interference on the
part of the naturalist, since it is founded upon
natural evidence, both embryological and zoologi-
cal. While this is so obvious and easy among
Batrachians, I have no doubt, from the scanty
investigations I have already made, that Embry-
ology will in the end furnish us with the means
of recognizing the true affinities among all ani-
mals, and of ascertaining their relative standing
and normal position in their respective classes
with the utmost degree of accuracy and precision ;
but, before this can be done, we must be as fa-
miliar with the different stages of growth of the
young animals of all classes as we already are
with those of Batrachians, and shall probably
have to push our researches in directions not yet
dreamed of.

Without entering into any details upon this
subject, I may as well state here, that among
Fishes I have lately discovered metamorphoses
as extensive as those known to take place among
Reptiles. Pisciculture being carried ou upon
so large a scale in some parts of Europe, it is
surprising that the fact should not have been
ascertained long ago. This is perhaps owing to
the circumstance, that these metamorphoses be-
gin after the hatching of the young, at a time
when they are apt to die if reared in close con-

802 EMBRYOLOGY AND CLASSIFICATION.

finement. In this stage, they ard, moreover,
generally too small to be readily seen in their
natural element. Nevertheless, this is the most
important period of their growth, with reference
to their natural affinities, and I shall take an
early opportunity to show how our young fishes,
aping the Gadoid or Blennioid type in their tran-
sition period, pass gradually into that of Labroids
and Lophioids ; how fish embryos, resembling
the tadpoles of frogs and toads, gradually as-
sume the form of Cyprinodqpts ; how A pods are
transformed into Jugulars and Abdominals, and
Malacopterygians into A^anthopterygians ; and,
finally, how a natural classification of the fishes
may be founded upon the correspondence which
exists between their embryonic development and
their structural gradation.

In order to show further how much we may ex-
pect from such investigations, I will allude briefly
to some of the facts with which my own studies
have thus far made me acquainted. One impor-
tant truth already assumes great significance in
the history of the growth of animals ; namely, that
whatever the changes may be through which an
animal passes, and however different the aspect
of these phases at successive periods may appear,
they are always limited by the character of the
type to which the animal belongs, and never
pass that boundary. Thus, the Radiate begins

EMBRYOLOGY AXD CLASSIFICATION. 303

life with characters peculiar to Radiates, and
ends it without assuming any feature of a higher
type. The Mollusk starts with a character es-
sentially its own, in no way related to the Ra-
diates, and never shows the least tendency to
deviate from it, either in the direction of the
Articulate or the Vertebrate types. This is
equally true of the Articulates. At no stage of
growth are their young homologous to those of
Mollusks or Radiates any more than to those of
Vertebrates, and in their final development they
stand equally isolated from all others. That this
is emphatically true of the Vertebrates has already
been fully recognized ; and the facts known with
reference to this highest type of the Animal King-
dom might have served as a warning against the
loose statements still current concerning the so-
called infusorial condition of the young Inver-
tebrates. These results are of the highest impor-
tance at this moment, when men of authority in
science are attempting to renew the theory of a
general transmutation of all animals of the higher
types out of the lower ones. If such views are
ever to deserve serious consideration, and be ac-
knowledged as involving a scientific principle, it
will only be when their supporters shall have
shown that the fundamental plans of structure
characteristic of the primary groups of the Ani-
mal Kingdom are transmutable, or pass into one

304 EMBRYOLOGY AND CLASSIFICATION.

another, and that their different modes of de-
velopment may lead from one to the other.
Thus far Embryology has not recorded one fact
on which to base such doctrines.

In Radiates, as soon as the young is formed,
it is a spheroidal, radiated animal, exhibiting
from the beginning, in all the three classes of
this primary division, — Polyps, Acalephs, and
Echinoderms, — the general plan of structure so
characteristic of the Radiate type, and so distinct
from all others. Let us first see what inference
may be drawn from the development of the lower
representatives of this type ; even though I can
only allude here very generally to facts which
could not be stated more at length without a
great deal of illustration and detail. The young
Polyp reaches its mature condition through a
succession of changes, which, when compared
with the structural complication of the adult
representatives of the different orders in this
same class, promise to furnish better data for the
classification of these animals than have ever
been obtained heretofore. The various modes
of increase observed among Astra3ans, and espe-
cially among Fungidae, already show that the
families in which independent animals complete
their growth, without forming compound com-
munities, are inferior to the compound ones ;
while those in which one diameter prevails over

EMBRYOLOGY AND CLASSIFICATION. 305

the other are superior to those with circular out-
lines. The Manicina, with its convoluted trench-
es, is, in its earlier condition, a perfectly cir-
cular hydra-like simple Polyp ; and the young
Herpolitha is also a simple circular animal, so
closely resembling a young Fungia that it
might be referred to the same genus. I have
no doubt that, when the embryonic history
of the young Madrepore is fully understood, it
will be found that this group also resembles the
young Astraea at first, though it stands so much
above it in its adult condition. In truth, all
these higher representatives of the class of Polyps
resemble the lower ones in their earliest state,
starting from a point common to all, and passing
through phases which are permanent and final
for the lower forms, but are only transient stages
in the development of the higher ones.

I have dwelt so much upon the Embryology of
the Acalephs in another chapter, that I need only
remind my readers here that this class also has a
common starting-point, exhibiting a remarkable
uniformity among the young, which extends even
to the Ctenophorae, the affinities of which have
been, and still are, the subject of controversy
among naturalists. In this class also, the differ-
ent phases of development furnish tbe best basis
for a classification of its representatives.

Until very recently it had been believed that

306 EMBRYOLOGY AND CLASSIFICATION.

the highest class in this division — the Echino-
derms — made an exception to this rule, and did
not agree with the other Radiates in its mode of
development. Johannes Muller, one of the most
eminent investigators of modern times, in a long
series of memorable papers upon the Embryology
of Radiates, has maintained that the larval con-
dition of the young Echinoderm, so far from being
homologous with the early stages of development
in the other classes, is essentially bilateral. It is
true that there is in many of the Radiates some-
thing akin to a bilateral symmetry, though it is
always subordinate to the prevailing idea of radi-
ation in the plan. This tendency is already quite
perceptible in the highest order of the Acalephs,
the Ctenophorae, and becomes still more so in
some representatives of the class of Echinoderms,
the highest in this type. The resemblance of the
larvae of the Echinoderms to the Ctenophorae had
not escaped my notice ; but during the past year
my son has shown conclusively, in a series of
microscopic investigations not yet published, that
they are as truly radiated as the most circular or
spheroidal of the type. The further growth of
the young Echinoderms, from the young Comatula
(as far as its history is known in its pentacrinal
condition) to the gradual transformation of the
common Star-Fish, with its undivided circular
outline, with its two rows of simple ambulacra!

EMBRYOLOGY AND CLASSIFICATION. 307

suckers without a disk at their end, and to the
various Echinoids and Holothurians, the early
phases of whose growth are described by J. Miil-
ler, shows plainly that the metamorphosis of the
Comatula furnishes a scale for the classification
of all the Crinoids of past ages, just as that of the
common Five-Finger (Asterias) gives the key to
the relative standing of all the families of Star-
Fishes, the more circular or pentagonal forms of
which are respectively inferior to their star-shaped
allies, those with two rows of suckers inferior to
those with four, and those with simple ambulacra
inferior to those in which* the ambulacra have
a disk-shaped extremity.

The beautiful investigations of Miiller have
made us acquainted with the young of several
families of the order of Echini or Sea-Urchin, in-
cluding the Spatangoids, so different with their
oblong form and eccentric mouth from the cir-
cular Sea-Urchin, with its central mouth. Yet
the Spatangoid in its earlier stages is spheroidal,
like the young Echinus ; and the ambulacral
apparatus, so highly differentiated in its vertical
extension in the adult Spatangoid, is as simple in
the young as in the Echinus. The adult Spatan-
goid is covered with innumerable hair-like spines,
while the young bears only a few large rods, re-
sembling even more those of a Cidaris than those
of an Echinus. We may, indeed, fairly say, that

808 EMBRYOLOGY AND CLASSIFICATION.

the successive changes of the higher Echiuoids
make us acquainted with a series of transfor-
mations which have their counterparts, not only
in the different families of the order as ranked
one above the other, but also in the order of suc-
cession of these Radiates in past .geological times.
Even among the Holothurians, imperfectly as
their development is known, it already appears,
upon embryonic data, that those without external
ambulacra are inferior to those which have them,
since the latter are destitute of these organs in
their earlier stages of growth. Notwithstanding
the direct bearing of these embryological facts
upon the classification of the Echinoderms, it is
surprising that no attention has thus far been paid
to the subject ; the eminent physiologist himself,
to whom we owe so large a share of our knowl-
edge of the facts above referred to, has failed to
perceive their significance in this connection.

It would require a discussion of facts not yet
sufficiently familiar even to naturalists, were I to
attempt a similar comparison of the successive
stages of growth of the Mollusks with the relative
landing of the different members of their respec-
tive classes ; and yet, as I have by my own in-
vestigations reached a synthesis which enables
me to discuss the question in its most general
bearing, I beg leave to submit here a few state-
ments, the full demonstration of which may be

EMBRYOLOGY AND CLASSIFICATION. 309

furnished hereafter. In many marine slugs ana
univalve shells the development of the young has
been traced again and again ; and their great re-
semblance among themselves, during the earlier
phases of their growth, has already attracted the
attention of all zoologists. This is the more re-
markable when taken in connection with the
extraordinary external difference in the appear-
ance of the adult. The young resemble a some-
what compressed oblong bag, supporting a broad
crescent-shaped veil, stretching evenly in every
direction on one side of the bag, and provided
around its edge with powerful vibratile cilia, by
the agency of which these small animals rotate in
the water with great activity. In this condition
the bag is protected by a very thin transparent
shell, existing even in those which are destitute
of shell both in the earlier and later stages of
their existence, being unprovided with any such
covering at first, and dropping it before they com-
plete their growth. The young of the Sea-Slugs,
which, with a large number of our marine Gas-
teropods and Pteropods, have been very carefully
observed, may give an idea of the younger stages
of, all Mollusks ; for, different as may be the
appearance of the young Cephalopod at some
periods of its life, it is not difficult, nevertheless,
to trace their homology, and even their close
resemblance, at certain periods, to the young of

810 EMBRYOLOGY AND CLASSIFICATION.

the Gasteropods, described above. I have satis-
fied myself of this fact while studying the trans-
formation of the young of our common Squid
(Loligo illecebrosa). Nor are the young of our
common Bivalves, and even those of our Ascidians
(the so-called soft-shelled Clams) or of the Bryo-
zoa, essentially different ; while a closer compari-
son of the condition of the young of the two latter
groups, during the stage when they swarm in the
water as free floating animals, will readily show
that they bear a similar relation to the young
Gasteropods and the young Cephalopods as the
Echinoderm Iarva3 bear to the young swarming
Acalephs or the young Polyps. In the later
phases of their advance .toward a mature con-
dition they constantly recall the appearance and
form of other representatives of their respective
classes, so that even an imperfect acquaintance
with this subject leads to the inference that there
probably exists between the successive stages of
growth of the Mollusk the same correspondence
with the different members of their respective
classes, in their natural gradation, as has already
been observed in the other types. A comparison
of the young of many Gasteropods, which, like
Natica, Pyrula, Buccinum, and Purpura, under-
go their early development in solid egg-cases,
has already furnished very interesting results ;
and collectors cannot be too careful in gather-

EMBRYOLOGY AND CLASSIFICATION. 311

ing these specimens, and making constant efforts
to ascertain by what Mollusks they are laid.
The fact that among Acephala the bivalve shells,
which have two transverse bundles of muscles in
their adult condition, 'have only one in earlier
life, furnishes a satisfactory evidence of the lower
standing of the Monomyaria when compared to
the Dimyaria ; and a closer investigation leaves
no doubt that the one large transverse muscle
of the Oyster corresponds to the posterior muscle
of the Clam (Mactra or Mya). Again, the prev-
alence of the vertical diameter over the longi-
tudinal and the transverse in the young, while
later the longitudinal diameter takes the lead,
affords valuable information respecting the rela-
tive standing of short-bodied or rounded Bivalves
in comparison with their more elongated allies.
And this is in accordance with the inferior posi-
tion of the Brachiopods and Bryozoa. But the
classification of Mollusks is too little advanced
as regards the relative standing of their numer-
ous families to allow a more direct comparison
at present.

In the type of Articulates the difficulties are
of another kind. The extraordinary number of
representatives in the classes of this type renders
a comprehensive view of their respective stand-
ing particularly difficult ; and yet, if we leave out
of sight the minor divisions, and keep in mind

312 EMBRYOLOGY AND CLASSIFICATION.

only the most prominent ones, the correspond-
ence between the phases of growth of the young
and the relative position of the different groups
of adults in their respective classes is very obvi-
ous. The worin-like character of the larval con-
dition of Insects has been noticed by all ento-
mologists, and the crustacean features of their
pupa are equally apparent. Neither can the an-
alogy be overlooked between the Centipedes and
the Worms, or that between the Spiders and Crus-
tacea. We have here the fullest evidence that
while* the highest Insects recall in their earlier
condition the permanent character of the adult
representatives of the lower classes in their type,
those Insects which in their class occupy a middle
and lower position, such as the Spiders and Cen-
tipedes, also correspond to the lower classes of the
same type. Any one familiar with the transfor-
mations of Butterflies, and the successive phases
of their final development, must have perceived
that, even while unfolding its wings, in one sin-
gle act preliminary to taking its flight, the But-
terfly truly recalls the form and mode of folding
the wings peculiar to the Moths and Sphinxes.
It is therefore particularly desirable that all
these changes should not only be separately de-
scribed, as they have been successively observed
in different Insects, but minutely compared with
one another, so as to establish with more pre-

EMBRYOLOGY AND CLASSIFICATION. 313

cision the correspondence of all their different
conditions. In tins direction there is a boundless
field open to the researches of young naturalists.
In the class of Crustacea enough is already
known to establish a correspondence between
the young of the higher members of the class
and the adults of its lower members ; and the
comparison may here be extended with remark-
able precision to the fossils of past ages, since
representatives of this class are known from the
earliest geological epochs in which animals ex-
isted at all to the present time. The class of
worms has of late attracted so much attention,
and so many of them have been studied during
their transformation, that, were these animals
more generally known, I could adduce striking
instances of this correspondence between the
younger stages of growth in the higher mem-
bers of the class and the adult forms of its lower
representatives. But I will not enter into these
details, as I have no vernacular names by which
I could designate them intelligibly, and for pro-
fessional naturalists this allusion is sufficient.
They will remember that the highest worms so
remarkable for the various locomotive and respi-
ratory appendages on their sides, are, in their
earlier phases, as destitute of these appendages
as are the lowest members of the class in their
adult condition.

14

314 EMBRYOLOGY AND CLASSIFICATION.

If we now pass to the highest type of the Ani-
mal Kingdom, the Vertebrates, there is no lack of
evidence to show the identity in their mode of
development, as well as the striking resemblance
of the young in their earliest stages of growth.
The young Fish, the young Reptile, the young
Bird, the young Mammal, resemble one another
to an astonishing degree, while they have not one
feature in their mode of growth which recalls
either the Articulate, the Mollusk, or the Radiate.
It is, therefore, not true, though so often stated,
that in their development the higher animals
pass successively through the condition of all the
lower ones ; while it is emphatically true that in
each of the four great branches of the Animal
Kingdom there is a common mode of develop
ment. It is equally true that in certain features
the higher classes of each branch in their younger
condition recall the characteristic features of the
lower ones, though each class has its own struc-
tural character, and early diverges from the com-
mon starting-point. One single case may suffice
to demonstrate this general statement. When
the young Skate begins to form upon the large
yolk of its egg, it has an oblong form, somewhat
club-shaped, the broader end representing the
head, while the tapering end is the tail. It is
early surrounded by a network of bloodvessels
circumscribed upon the yolk by a circular vein.

EMBRYOLOGY AND CLASSIFICATION. 815

In this condition it closely resembles the young
Snake as represented by Rathke, or the young
Bird as represented by Pander, or the young
Rabbit as represented by Bischoff, and the inex-
perienced student of Embryology would find it
difficult to detect any character by which these
different embryos could be referred to thbir re-
spective classes among Vertebrates ; for nothing
indicates in them as yet the Fish or the Reptile,
the Bird or the Mammal. But as they increase
in size and complication of structure, the young
Skate becoming prominent above the yolk from
which it is nourished, it may be perceived that,
while it retains its primitive connection with the
yolk, through the enlarged vessels first observed,
its body remains exposed above it, while in the
other three the body becomes enclosed in a bag
which gradually grows out of its own lower mar-
gin, and, bending over the back, closes upon it
to form a protecting envelope, the amnios, while
another bag, the allantois, now extends from the
lower side, covered with vessels, which increase in
number and extent as the bag grows larger, while
at the same time the vessels of the yolk and the
yolk itself are gradually drawn into the body.
This new bag, with its innumerable vessels, folds
also in every direction over the young already en-
closed in its first bloodless envelope, and so forms
a second protecting sac. From this time forward

316 EMBRYOLOGY AND CLASSIFICATION.

the Fish can no longer be confounded with the
young Bird or Reptile or Mammal, and the blood-
vessels of the latter will soon enter into such con-
nection with the parent as to distinguish it also
from the young Bird or Reptile which forms no
such connection. I will not pursue this trans-
formation farther in all its details, which would
require numerous figures to be well understood,
but briefly allude to a few facts proving still more
clearly the unity of plan prevailing throughout
the whole Vertebrate type.

The young Skate up to the period already de-
scribed does not differ from the young Shark ;
but when the fins make their appearance, though
exactly the same at first in both these animals,
one pair in the Skate presently grows larger
than the others, expanding upon the sides of the
body and extending towards the tail and towards
the front of the head. Thus the young Skate,
as it advances in life, leaves behind the Shark
character, common to both in their younger
state, but permanent only in the Shark, in which
the fins undergo no such change. This shows
beyond a doubt that the family of Skates is su-
perior to that of Sharks, — an inference which
is confirmed by the order of their succession
upon earth, the Shark family having preceded
that of the Skates, in geological times. • But it is
not only among the lower groups that such cor»

EMBRYOLOGY AND CLASSIFICATION. 317

respondences may be traced. The resemblance
of an adult Skate, especially in the configuration
of the face, the form of the mouth, the position
of the nostrils, the arrangement of the gills, to
some of the earlier conditions in the growth of
the young Mammal, not excepting the human
family, is equally striking. No one can fail to be
impressed with this resemblance who compares
the head of an embryo quadruped, looking at it
in front face, with the adult Skate.*

Indeed, modern Embryology leads at once to
the consideration of the most occult problem, as
to the origin of animals, suggested by these com-
parisons. What do these resemblances mean,
from some of which we shrink as unnatural and
even revolting ? If we put a material interpre-
tation upon them, and believe that even Man
himself has been gradually developed out of a
Fish, they are repugnant to our better nature.
But looked at in their intellectual significance,
they truly reveal the unity of the organic con-
ception of which Man himself is a part, and mark
not only the incipient steps in its manifestation,
but also, with equal distinctness, every phase in
its gradual realization. They mean that when
the first Fish was called into existence, the Ver-

* Let any one who doubts the truth of this statement as re-
gards the human embryo compare the figures of the latter, pub-
lished by Ecker, in the /cones Physiologicce, with any adult Skate.

318 EMBRYOLOGY AND CLASSIFICATION.

tebrate type existed as a whole in the creative
thought, and the first expression of it embraced
potentially all the organic elements of that type,
up to Man himself. To me the fact that the
embryonic form of the highest Vertebrate recalls
in its earlier stage the first representatives of its
type in geological times and its lowest repre-
sentatives at the present day, speaks only of an
ideal relation, existing, not in the things them-
selves, but in the mind that made them. It is
true that the naturalist is sometimes startled at
these transient resemblances of the young among
the higher animals in one type to the adult con-
dition of the lower animals in the same type ;
but it is also true that he finds each one of the
primary divisions of the Animal Kingdom bound
to its own norm of development, which is abso-
lutely distinct from that of all the others ; it is
also true, that, while he perceives corresponden-
ces between the early phases of the higher animals
and the mature state of the lower ones, he never
sees any one of them diverge in the slightest
degree from its own structural character, — never
sees the lower rise by a shade beyond the level
which is permanent for the group to which it
belongs, — never sees the higher ones stop short
of their final aim, either in the mode or the
extent of their transformation. I cannot repeat
too emphatically, that there is not a single fact

EMBRYOLOGY AND CLASSIFICATION. 319

in Embryology to justify the assumption that the
laws of development, now known to be so precise
and definite for every animal, have ever been
less so, or have ever been allowed to run into
each other. The philosopher's stone is no more
to be found in the organic than the inorganic
world ; and we shall seek as vainly to transform
the lower animal types into the higher ones by
any of our theories, as did the alchemists of old
to change the baser metals into gold.

THE END.

Cambridge : Electrotype* and Printed by Welch, Bigelow,

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