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HARVARD 
COLLEGE 
LIBRARY 



AN 

ESSAY ON CLASSIFICATION. 



AN ESSAY 




ON 



CLASSIFICATION. 



■IT 



(Or .... /r- " -•■-; 

LOUIS AGASSIZ. 



■)0 
LONGMAN, BEOWN, GKEEN, LONGMANS, & ROBERTS, 

AMD 

TRUBNER & Co. 

MDCCCTJX. 






T^\\3Uou -> 0'?^ ^ "^^p • 18- 



Vi^rinp' H^lia-tt 



I r \ / • — > • 



/ 



■ ^ 



T. RirnAHIlS, .17, ORKAT QUKKH BTRFKT. 



'vi ex 



PREFACE. 



The contents of this volume appeared for the first time 
as an introduction to a larger work now in course of 
publication, under the title of Contributions to the Natu- 
ral History of the United States} Friends in whose 
opinion I have great confidence, having expressed the 
desire that a separate edition of that part of my book 
which relates to the general principles of Zoology should 
be published in England, I gladly complied with the 
request of Messrs. Triibner and Co., that I should autho- 
rize such a reprint, and have availed myself of the oppor- 
tunity to make such corrections as seemed necessary, and 
also to complete the references up to the latest possible 
date. Besides this, I have also added a new chapter 
upon the Categories of Analogy, a subject which, until 

* Thus far, two Yolumes quarto, ton by Messrs. Little, Brown, and Co., 
with thirty-four plates, have ap- in October 1857. The third volume 
pemred. They were published in Bos- is now in the press. 



VI PREFACE. 

now, I have not felt fully prepared to discuss in all ita 
bearings. Having, however, made no essential alterations 
in this Essay on ClassiJiccUion^ it may not be out of 
place for me to repeat here such parts of the preface to 
the first edition aa may explain the special purpose of 
the treatise, and also the frequent allusions, which could 
not have been omitted without remodelling the whole, 
referring to chapters which belong to other parts of the 
work. 

The preface to the complete work above alluded to 
states that, in consequence of the liberality of the sub- 
scription in America^ " this volume, which, according to 
the original plan, was designed to be one of special 
descriptive Zoology, contains, in addition to a descrip- 
tion of the North American Turtles, a review of the 
classification of the whole animal kingdom. I have also 
endeavoured to make it a text-book of reference for the 
student, in which he may find notices of all that has 
been accomplished in the various departments of Natural 
History alluded to, and which I trust yoimg naturalists 
wiU take, not only as an indication of what has been 
done, but as an earnest of what remains to be done in the 
fields now open to our investigation. 



PREFACE. VU 

" I must beg my European readers to remember that 
this work is written in America, and more especially for 
Americans ; and that the community to which it is par- 
ticularly addressed has very different wants from those 
of the reading public in Europe. There is not a class of 
learned men here, distinct from the other cultivated 
members of the community. On the contrary, so general 
is the desire for knowledge, that I expect to see my book 
read by operatives, by fishermen, by farmers, quite as 
extensively as by the students in our Colleges or by the 
learned professions, and it is but proper that I should 
endeavour to make myself understood by alL 

" Of the two volumes now complete of this series, the 
First Part contains an exposition of the general views I 
have arrived at, thus far, in my studies of Natural His- 
tory." (It is this First Part, entitled Essay on Classifr 
catioUy which is here reprinted). "The Second Part 
shows how I have attempted to apply these results to the 
special study of 2Joology, taking the order of Testudinata 
as an example. The Third Part exemplifies the bearing 
of Embryology upon these general questions, while it 
contains the fullest illustration of the embryonic growth 
of the Testudinata." 



VUl PREFACE. 

In conclusion, I have to acknowledge my indebtedness 
to Mr. Philip Lutley Sclater, of Corpus Christi College, 
Oxford, for his kindness in revising the proofs of this 
edition, — ^a tedious task, which could only be entrusted to 
one extensively conversant with the literature of oui- 
science, and which he has executed with great care. 



L. Agassiz. 



Cambridge, Mass., 

2nd December, 1868. 



] 



ESSAY ON CLASSIFICATION. 



CHAPTER FIRST. 

THE FUNDAMENTAL RELATIONS OF ANIMALS TO ONE ANO- 
THER AND TO THE WORLD IN WHICH THEY LIVE, AS THE 
BASIS OF THE NATURAL STSTEM OF ANIMALS. 



SECT. I. 

THE LEADING FEATUBE9 OF A NATUBAL ZOOLOGICAL SYSTEM ABE 

ALL FOUNDED IN NATUBE. 

Modern classifications of a.TiiTnal8 and plants are based 
upon the peculiarities of their structure ; and this is gene- 
rally considered as the most important, if not the only 
safe guide in our attempts to determine the natural rela- 
tions which exist between animals. This view of the sub- 
ject seems to me, however, to circumscribe the foundation 
of a natural sjrstem of Zoology and Botany within too 
narrow limits, to exclude from our consideration some of 
the most striking characteristics of the two organic king- 
doms of nature, and to leave it doubtful how far the 
arrangement thus obtained is founded in reality, and how 
far it is merely the expression of our estimate of these 
structural differences. It has appeared to me appropriate, 
therefore, to present here a short exposition of the leading 
features of the animal kingdom, as an introduction to the 
study of Natural History in general and of Embryology 

B 



v^ 



ESSAY ON CLASSIFICATION. 



CHAPTER FIRST. 

THE FUNDAMENTAL RELATIONS OF ANIMALS TO ONE ANO- 
THER AND TO THE WORLD IN WHICH THEY LIVE, AS THE 
BASIS OF THE NATURAL SYSTEM OF ANIMALS. 



SECT. I. 

THE LEADING FEATUBE9 OF A KATITBAL ZOOLOGICAL SYSTEM ABE 

ALL FOUNDED IN NATUBE. 

Modern classifications of animals and plants are based 
upon the peculiarities of their structure ; and this is gene- 
rally considered as the most important, if not the only 
safe guide in our attempts to determine the natural rela- 
tions which exist between animals. This view of the sub- 
ject seems to me, however, to circumscribe the foundation 
of a natural sjrstem of Zoology and Botany within too 
narrow limits, to exclude from our consideration some of 
the most striking characteristics of the two organic king- 
doms of nature, and to leave it doubtful how far the 
arrangement thus obtained is founded in reality, and how 
far it is merely the expression of our estimate of these 
structural diflFerences. It has appeared to me appropriate, 
therefore, to present here a short exposition of the leading 
features of the animal kingdom, as an introduction to the 
study of Natural History in general and of Embryology 

B 



*^ 



2 ESSAY ON CLASSIFICATION. 

in particular, as it would afford a desirable opportunity of 
establishing a standard of comparison between the changes 
animals undergo during their growth, and the permanent 
characters of full-grown individuals of other types; and, 
perhaps, of showing also what other points beside struc- 
ture might with advantage be considered in ascertaining 
the manifold relations of animals to one another, and to 
the world in which they live, upon which the natural sys- 
tem may be founded. 

In considering these various topics, I shall of necessity 
have to discuss many questions bearing upon the veiy 
origin of organized beings, and to touch upon many points 
now imder discussion among scientific men. I shall, how- 
ever, avoid controversy as much as possible, and only try 
to give the results of my own studies and meditations 
in as clear a manner as I possibly can in the short space 
of an essay like this. 

There is no question in Natural History on which more 
diversified opinions are entertained, than on that of clas- 
sification ; not that naturahsts disagree as to the necessity 
of some sort of arrangement in describing animals or 
plants; for since nature has become the object of special 
studies, it has been the universal aim of all naturalists to 
arrange the objects of their investigations in the most 
natural order possible. Even Buffon, who began the pub- 
lication of his great Natural History by denying the exist- 
ence in nature of anything like a system, closed his work 
by grouping the birds according to certain general features 
exhibited in common by many of them. It is time that 
authors have differed in their estimation of the charactei's 
on which their different arrangements are founded; and it is 
equally true that they have not viewed their arrangements 
in the same light, some having plainly acknowledged the 



FUNDAMENTAL RELATIONS OF ANIMALS. 3 

artificial character of their systems, while others have 
urged theirs as the true expression of the natural relations 
which exist between the objects themselves. But, whether 
systems are presented as artificial or natural, they have, 
to this day, been considered generally as the expression of 
man's understanding of natural objects, and not as devised 
by the Supreme Intelligence, and manifested in these ob- 
jects.^ 

There is only one point in which all these innumerable 
systems seem to meet, namely, the existence in nature 
of distinct species, persisting with all their peculiarities, 
for a time at least; for even the immutability of species 
has been questioned.^ Beyond species, however, this con- 
fidence in the existence of the divisions generally admit- 
ted in zoological systems diminishes greatly. With respect 
to genera, we already find the number of the naturalists 
who accept them as natural divisions much smaQer; few 
of them having expressed a belief that genera have an exist- 
ence in nature as distinct as species. And as to families, 
orders, classes, or any kind of higher divisions, they seem 
to be universally considered as convenient devices, framed 
with the view of facilitating the study of innumerable 
objects, and of grouping them in the most suitable man- 
ner. The indifference with which this part of our science 
is generally treated becomes unjustifiable, considering the 
progress which Zoology in general has made of late. It 

^ The expressions constantly used own making ; which can, however, 

with reference to genera and species if the views I shall present below are 

and the higher groups in our systems, at all correct, only be true in so far 

such as, Mr. A. has made such a species as these groups are not true to nature, 
a^enus; Mr.B.mp^y«thisorthatspe- ' Lamabck (J. B. pe), Philosophie 

eies to form hu genus ; and those in zoologique, Paris, 1809, 2 vols. Svo.; 

which most naturalists indulge when 2de ^it., 1830. — Powell (The Rby. 

speaking of Mn> species, ^An> genera, Baden), Essays on the Spirit of the 

M^'r families, MWr systems,-— exhibit Inductive Philosophy, etc., London, 

in an unquestionable light their con- 1855, 1 vol. 8vo. Compare, also. Sect, 

viction, that such groups are of their 15, below. 

B 2 



4 ESSAY ON CLASSIFICATION. 

is a matter of consequence, whether genera arc circum- 
scribed in our systematic works within these or those 
limits ; whether families inclose a wider or more contracted 
range of genera ; whether such or such orders are admitted 
in a class, and what are the natural boundaries of classes ; 
as well as how the classes themselves are related to one 
another, and whether or not all these groups are considered 
as resting upon the same foundation in nature. 

Without venturing here upon an analysis of the various 
systems of Zoology, — the prominent features of which are 
sufficiently exemplified for my purpose by the systems of 
Linnaeus and Cuvier,^ which must be familiar to every 
student of Natural History — it is certainly a seasonable 
question to ask, whether the animal kingdom exhibits only 
those few subdivisions into orders and genera, which the 
Linnsean system indicates, or whether the classes differ 
among themselves to the extent which the system of 
Cuvier would lead us to suppose. Or is, after all, this 
complicated structure of classification merely an ingenious 
human invention which every one may shape, as he 
pleases, to suit himself? When we remember that all 
works on Natural History admit some system or other of 
this kind, it is certainly an aim worthy of a true naturalist, 
to ascertain what is the real meaning of all these divisions. 

Embryology, moreover, forces the inquiry upon us at 
every step, as it is impossible to establish precise compa- 
risons between the different stages of growth of yoimg 
animals of any higher group, and the permanent charac- 
ters of full-grown individuals of other types, without first 
ascertaining what is the value of the divisions with which 
we may have to compare embryos. My studies in this 
department have led me for many years to pay the most 

^ Compare Chap. III. 



FUNDAMENTAL RELATIONS OF ANIMALS. 5 

carefiil attention to this subject, and to make special in- 
vestigations for its solution. 

Before I proceed any further, however, I would submit 
one case to the consideration of my reader. Suppose that 
the innumerable articulated animals, which are counted 
by tens of thousands, nay, perhaps by hundreds of thou- 
sands, had never made their appearance upon the surface 
of our globe, with one single exception : suppose, for in- 
stance, that our Lobster {Homancs (miericantis) were the 
only representative of that extraordinarily diversified type, 
— ^how should we introduce that species of animal into our 
systems ? Simply as a genus with one species, by the side 
of all the other classes with their orders, families, etc., or 
as a family containing only one genus with one species, 
or as a class with one order and one genus, or as a class 
with one family and one genus ? And should we acknow- 
ledge, by the side of Vertebrata, MoUusca, and Radiata, 
another type, Articulata, on account of the existence of 
that one Lobster, or would it be natural to call it by a 
single name, simply as a species, in contradistinction to 
all other animals ? It was the consideration of this sup- 
posed case which led me to the investigations detailed 
below, which, I hope, may end in the ultimate solution of 
this apparently inextricable question. 

Though what I have now to say about this supposed 
case cannot be fully appreciated before reading my remarks 
in the following chapter,^ respecting the character of the 
different kinds of groups adopted in our systems, it must 
be obvious that our Lobster, to be what we see this ani- 
mal is, must have had its frame constructed upon that very 
same plan of structure which it exhibits now. And, if I 
should succeed in showing that there is a difference be- 

^ See Ohap. II. 



6 ESSAY ON CLASSIFICATION. 

tween the conception of a plan and the manner of its execu- 
tion, upon which classes are founded in contradistinction to 
the types or branches to which they belong, we might arrive 
at this distinction by a careful investigation of that single 
Articulate, as well as by the study of all of them ; and we 
might recognize its type and ascertain its class-characters 
as fully as if the type embraced several classes, and these 
classes thousands of species. Secondly, this animal has 
a form, which no one would fail to recognize ; so that, if 
form can be shown to be characteristic of families, we 
could thus determine its family. Again : besides the gene- 
ral structure, showing the fundamental relations of all the 
systems of organs of the body to one another in their 
natural development, our investigation could be carried 
into the study of the details of that structure in every part, 
and would thus lead to the recognition of what constitutes 
everywhere generic characters. Finally: as this animal 
has definite relations to the surrounding world, as the in- 
dividuals living at the time bear definite relations to one 
another, as the parts of the body show definite propor- 
tions, and its surface exhibits a special ornamentation, the 
specific characters could be traced as fully as if a number of 
other species were at hand for comparison; and they might 
be drawn and described with sufficient accuracy to dis- 
tinguish it at any future time froia any other set of species 
discovered afterwards, however closely these new species 
might be allied to it. In this case, then, we should have 
to acknowledge a separate branch in the animal kingdom, 
with a class, a family and a genus, in order to introduce 
one species into its proper place in the system of animals. 
But this class would have no order, if orders determine the 
rank, as ascertained by the complication of structure ; for, 
where there is but one representative of a type, there is 



FUNDAMENTAL RELATIONS OF ANIMALS. 7 

no room for the question of its superiority or inferiority 
in comparison to others within the limits of the class, 
orders being groups subordinate to one another in their 
class. Yet, even in this case, the question of the standing 
of Articulata, as a type among the other great branches of 
the animal kingdom, would be open to our investigations ; 
but it would assume another aspect from that which it now 
presents, as the comparison of Articulata with the other 
types would then be limited to the Lobster, and would 
lead to a very diflFerent result from that at which we may 
arrive, now that this type includes such a large number 
of most extensively diversified representatives, belonging 
even to different classes. That such speculations are not 
idle must be apparent to any one who is aware, that, dur- 
ing every period in the history of our globe in past geolo- 
gical ages,^ the general relations, the numeric proportions, 
and the relative importance of all the types of the animal 
kingdom, have been ever changing, until their present 
relations were established. Here, then, the individuals of 
one species, as observed while living, simultaneously ex- 
hibit characters, which, to be expressed satisfactorily and 
in conformity to what nature tells us, would require the 
establishment, not only of a distinct species, but also of a 

* A series of classifications of ani- rate knowledge of the relative stand- 
mala and plants, exhibiting each a ing of all animals and plants, which, 
natural system of the tjpes known at present, can only be inferred from 
to have existed simultaneously dur- the perusal even of those palasonto- 
ing the seyeral successive geological logical works in which fossil remains 
periods, considered singly and with- are illustrated according to their as- 
out reference to the types of other sociation in different geological form- 
ages, would show in a strong light ations ; for, in all these works, the 
the different relations in which the remains of past ages are uniformly 
classes, the orders, the families, and referred to a system established upon 
even the genera and species, have the study of the animals now living, 
stood to one another during each thus lessening the impression of their 
epoch. Such classifications would peculiar combination for the periods 
illustrate, in the most impressive under consideration, 
maimer, the importance of an accu- 



8 ESSAY ON CLASSIFICATION. 

distinct genus, a distinct family, a distinct class, a distinct 
branch. Is not this in itself evidence enough that genera, 
families, orders, classes and types have the same founda- 
tion in nature as species, and that the individuals living 
at the time have alone a material existence, they being 
the bearers, not only of all the different categories of struc- 
ture upon which the natural system of animals is foimded, 
but also of all the relations which animals sustain to the 
surrounding world, — thus showing that species do not 
exist in nature in a different way from the higher groups, 
as is so generally believed ? 

^ The divisions of animals according to branch, class, 
order, family, genus, and species, by which we express the 
results of our investigations into the relations of the 
/ animal kingdom, and which constitute the primary ques- 
I tion respecting any system of Zoology, seem to me to 
jd^serve the consideration of all thoughtful minds. Are 
those divisions artificial or natural \ Are they the devices 
of the human mind to classify and arrange our knowledge 
in such a manner as to bring it more readily within our 
grasp and facilitate further investigations, or have they 
been instituted by the Divine Intelligence as the cate- 
gories of his mode of thinking V- Have we, perhaps, thus 
far been only the unconscious interpreters of a Divine 
conception, in our attempts to expound nature? and 
when in our pride of philosophy we thought that we 
were inventing systems of science, and classifying creation 
by the force of our own reason, have we followed only, 
and reproduced, in our imperfect expressions, the plan 

1 It must not be overlooked here but merely as the expression of a 

that a system may be natural, that fact existing in nature — no matter 

is, may agree in every respect with how — which the human mind may 

the facts in nature, and yet not be trace and reproduce in a systematic 

considered by its author as the mani- form of its own invention, 
festation of the thoughts of a Creator, 



FUNDAMENTAL RELATIONS OF ANLMALS. 9 

whose foundations were laid in the dawn of creation, and \ 
the development of which we are laboriously studying, — 
thinking, as we put together and arrange our fragmentary 
knowledge, that we are introducing order into chaos 
anew ? ^ this order the result of the exertions of human 
skill and ingenuity; or is it inherent in the objects them- 
selves, so that the intelligent student of Natural History 
is led unconsciously, by^he study of the animal kingdom 
itself^ to these conclusions ;1 the great divisions under which 
he arranges animals being indeed but the headings to the 
chapters of the great book which he is reading ? To me it 
appears indisputable, that this order and arrangement of 
our studies are based upon the natural, primitive relations 
of animal lifc/^those systems, to which we have given 
the names of the great leaders of our science who first 
proposed them being in truth but translations into hu- 
man language of the thoughts of the Creator. And if 
this is indeed so, do we not find in this adaptability of the 
human intellect to the facts of creation,^ by which we be- 
come instinctively, and, as I have said, unconsciously, the 
translators of the thoughts of God, the most conclusive 
proof of our aflStnity with the Divine mind 1 and is not 
this intellectual and spiritual connection with the Al- 
mighty worthy of our deepest consideration ? If there is 
any truth in the belief that man is made in the image of 
God, it is surely not amiss for the philosopher to endeavour, 
by the study of his own mental operations, to approximate 
the workings of the Divine Eeason, learning from the 
nature of his own mind better to understand the Infinite 

^ The human mind is in tune with may be considered as a school in 

nature, and much that appears as a which man is taught to know himself, 

result of the working of our intelli- and his relations to his fellow beings, 

gence is only the natural expression as well as to the First Cause of all 

of that preestablished harmony. On that exists, 
the other hand the whole universe 



10 ESSAY ON CLASSIFICATION. 

Intellect from which it is derived. Such a suggestion 
may, at first sight, appear irreverent. But, who is the 
truly humble ? He who, penetrating into the secrets of 
creation, arranges them under a formula, which he proudly 
calls his scientific system ? or he who in the same pur- 
suit recognizes his glorious affinity with the Creator, and 
in deepest gratitude for so sublime a birthright strives to 
be the faithftd interpreter of that Divine Intellect with 
whom he is permitted, nay, with whom he is intended, 
according to the laws of his being, to enter into commu- 
nion'? 

I confess that this question, as to the nature and 
foundation of our scientific classifications, appears to me 
to have the deepest importance ; an importance far greater, 
indeed, than is usually attached to it. If it can be proved 
that man has not invented, but only traced, this syste- 
matic arrangement in nature ; that these relations and 
proportions, which exist throughout the animal and vege- 
table world, have an intellectual, an ideal connection, in 
the mind of the Creator ; that this plan of creation, which 
so commends itself to our highest wisdom, has not grown 
out of the necessary action of physical laws, but was the 
free conception of the Almighty Intellect, matured in liis 
thought before it was manifested in tangible external 
forms ; — if, in short, we can prove premeditation prior to 
the act of creation, we have done, once and for ever, with 
the desolate theory which refers us to the laws of matter 
as accounting for all the wondera of the universe, and 
leaves us with no God but the monotonous, unvarying 
action of physical forces, binding all things to their 
ine\dtable destiny.^ I think our science hiis now reached 

1 I allude here onlj to the doc- necoMary to add, that there are phj- 
trines of materialists. But I feel it deists who might be shocked at the 



FUNDAMENTAL RELATIONS OF ANIMALS. 1 1 

that degree of advancement, when we may venture upon 
such an investigation. 

The argument for the existence of an intelligent Creator 
is generally drawn from the adaptation of means to ends, 
upon which the Bridgewater treatises, for example, have 
been based.^ But this does not appear to me to cover 

idea of beiDg considered as material- not be considered as accounting for 
ists, who are jet prone to believe, the existence of living beings, even 
that, when they have recognized the though these have a material body, 
laws which regulate the physical unless it be actually shown that these 
world, and acknowledged that these laws imply by their very nature the 
laws were established by the Deity, production of such beings. Thus far, 
they have explained everything, even Cross' experiments are the only ones 
when they have considered only the offered as proving such a result. I 
phenomena of the inorganic world: do not know what physicists may 
as if the world contained no living think about them now ; but I know 
beings ; and as if these living beings that there is scarcely a zodlogist who 
exhibited nothing that differed from doubts that they only rest^ upon 
the inorganic world. Mistaking for mistake. Life, in appropriating the 
a casual relation the intellectual con- physical world to itself, with all its pe- 
nexion observable between serial phe- culiar phenomena, exhibits, however, 
nomena, they are unable to perceive some of its own, and some of a higher 
any difference between disorder, and order, which cannot be explained by 
the free, independent, and self-pos- physical agencies. The circumstance, 
sessed action of a superior mind ; and that life is so deeply rooted in the 
call mysticism, even a passing allu- inorganic nature, affords, neverthe- 
sion to the existence of an immate- less, a strong temptation to explain 
rial principle in animals, which they one by the other ; but we shall see 
acknowledge themselves in man. presently how fallacious these at- 
[Powell's Essays, etc., p. 478, 385, tempts have been, 
and 466.] I would further remark, ^ The Bridgewater Treatises, on 
that, when speaking of creation in the Power, Wisdom, and Goodness of 
contradistinction with reproduction, God, as Manifested in the Creation : 
I mean only to allude to the differ- Chalmers (Thomas), The Adapta- 
ence there is between the regular tion of External Nature to the Moral 
course of phenomena in nature, and and Intellectual Constitution of Man; 
the establishment of that order of Glasgow, 1839, 2 vols. 8vo. — Kidd 
things, without attempting to explain (John), On the Adaptation of Exter- 
either ; for, in whatever manner any nal Nature to the Physical Condition 
state of things which has prevailed of Man ; London, 1833, 1 vol. 8vo. — 
for a time upon earth may have been Whewell (Will.), Astronomy and 
introduced, it is self-evident that its General Physics considered with Re- 
establishment and its maintenance ference to Natural Theology; Lon- 
for a determined period are two very don, 1839,1 vol. 8vo. — Bell(Chable8), 
different things, however frequently The Hand, its Mechanism and Vital 
they may be mistaken as identical. Endowments, as evincing Design; 
It is, further, of itself plain that the London, 1833, 1 vol. 8vo. — Rooet 
laws which may explain the pheno- (Peter Mark), Animal and Ye^e- 
mena of the materul world, in con- table Physiology, considered with 
tradistinction from the organic, can- Reference to Natural Theology ; Lon- 



12 



ESSAY ON CLASSIFICATION. 



the whole ground ; for we can conceive that the natural 
action of objects upon each other should rftsult in a final 
fitness of the universe, and thus produce an harmonious 
whole. Nor does the argument derived irom the con- 
nection of organs and functions seem to me more satis- 
factory ; for, beyond certain limits, it is not even tnia 
We find organs without functions, as, for instance, the 
teeth of the whale, which never cut through the gum, and 
the breast in all males of the class of mammalia. These 
and similar organs are preserved in obedience to a certain 
uniformity of fundamental structure, true to the original 
formula of that division of animal life, even when not 
essential to its mode of existence. The organ remains^ 
not for the performance of a function, but with reference 
to a plan,^ and might almost remind us of what we often 
see in human structures, when, for instance, in architec- 
ture the same external combinations are retained for the 
sake of symmetry and harmony of proportion, even when 
they have no practical object. 

I disclaim every intention of introducing into this work 
any evidence irrelevant to my subject, or of supporting any 
conclusions not immediately flowing from it; but I can- 
not overlook or disregard here the close connection which 



doD, 1834, 2 vols. Syo. — Bucklard 
(Will.), Geology and Mineralogy 
considered with Reference to Natural 
Theology ; London, 1836, 2 yoIs. Syo., 
2nd edit., 1837.— Kibby (Will.), 
The Power, Wisdom, and Goodness 
of God, as Manifested in the Creation 
of Animals, and in their History, 
Habits, and Instincts; London, 1835, 
2 vols. 8vo. — Pbout (Will.), Chemis- 
try, Meteorology, and the Function 
of Digestion, considered with Refer- 
ence to Natural Theology ; London, 
1834, 1 Yol. 8vo. Compare also :— 
Stbauss-Dubkueim (Uxbc), Th6o- 



logie de la Nature; Paris, 1852, 3 
vols,, 8yo. — MiLLEB (Hugh), Foot- 
prints of the Creator; Edinburgh, 
1849, 1 vol. 12mo. — Babbaqb (C), 
The Ninth Bridgwater Treatise, a 
Fragment; London, 1838, 1 vol. 8vo., 
2nd edit. 

1 The unity of structure of the 
limbs of club-footed or pinnated ani- 
mals, in which the fingers are never 
moved, with those which enjoy the 
most perfect articulations and free- 
dom 01 motion, exhibits this reference 
most fully. 



FUNDAMENTAL RELATIONS OF ANIMALS. 13 

t|iAjAjflj2SliHgCTi ^^^ fe/^tff flg^gj^^TiArl b^ scientific^ inves- 
tigatiqiv. and the discussions now carried on respecting 
the origin of organized beings. And, thouglTTknow tho^e 
who hold it t o be very unscientific to believe that think- 
ing is not someffilng inherent in matter, and that there is 
an essential diffefence tietween inorganic and hving and 
thinking beings, I shall not be prevented, by aiiy such 
pretensions of a false philosophy, from expressing my 
conviction that, as ^ong as it cannot be shown that matter 
or physical forces do actually reason, any manifestation of 
thought is to Tie considered as evidence of the existence 
of aj;lnnting being as the author of such thought, aid 
that an intelligent and intelligible connection between the 
facts of nature must be looked upon as a direct proof of 
the existence of a thinking God,^ as certainly as man ex- 
hibits the power of thinking when he recognises their 
natural relations. 

As I am not writing a didactic work, I will not enter 
here into a detailed illustration of the facts relating to the 
various subjects submitted to the consideration of my 

^ I am well vifite that even the either by the fear of being supposed 

most eminent isTestigators consider to share clerical or sectarian preju- 

the task of science at an end, as soon dices, or because it may be dangerous 

as the most general relations of natu- for them to discuss freely such ques- 

ral phenomena have been ascertained, tions without acknowledging at the 

JEo Tna"y ^^flipquiryifflto t*'^ primi. same time the obligation of taking 

tire caus e of th<^i r ^Tiaf<>n<»A aAAmfl the Old Testament as the standard 

ei tjiei be yond thf n^^^^^ ^^f "***", ^rjM. by which the validity of their results 

Iferongii^g ^^ „ ^ ^ Itb'^'^'^pbx ^^j^ is to be measured. Science, however, 

to phys ics. To TEese the name of can only prosper when confining itself 

' 6oa t cfpeBjn out of place in a scien- within its legitimate sphere; and no- 

tific work ; as if the knowledge of thing can be more detrimental to its 

secondary affencles constituted alone true dignity than discussions like 

a worthy subject for their investiga- those which took place at the last 

tions, and as if nature could teach meeting of the German Association 

nothing about its Author. Many, of Naturalists in Gdttingen, and which 

again, are no doubt prevented from have since then been carried on in 

expressing their conviction that the several pamphlets in which bigotry 

world was called into existence and vies with personality and invective, 
is regulated by an intelligent God, 



14 ESSAY ON CLASSIFICATION. 

reader beyond what is absolutely necessary to follow the 
argument, nor dwell at any length upon the conclusions 
to which they lead ; but will simply recall the leading 
features of the evidence, assuming in the argument a full 
acquainta,nce with the whole range of data upon which it 
is founded, whether derived from the afl&nities or the 
anatomical structure of animals, or from their habits and 
their geographical distribution, from their embryology, or 
from their succession in past geological ages, and the 
peculiarities they have exhibited during each,^ believing, 
as I do, that isolated and disconnected facts are of little 
consequence in the contemplation of the whole plan of 
creation ; and that, without a consideration of all the facts 
furnished by the study of the habits of animals, by their 
anatomy, their embryology, and the history of the past 
ages of oui- globe, we shall never arrive at the knowledge 
of the natural system of animals. 

Let us now consider some of these topics more spe- 
cially. 

1 Many points little investigated bridge in 1849; Boston, 1850, 1 vol. 

thus far by most naturalists, but to 8yo., p. 432.) Meanwhile, I refer in 

which I have of late years paid par> foot notes to such works as contain 

ticular attention, are here presented the materials already on hand for the 

only in an aphoristic form, as results discussion of these subjects, even 

established by extensive investiga- when presented in a different light, 

tions, though unpublished, most of I would only beg leave to add, that 

which will be fully illustrated in my in these references I have by no 

following volumes, or in a special means attempted to quote all the 

work upon the Plan of the Creation, writers upon the various topics under 

(See AoAssiz (L.), On the Difference consideration, but only the most pro- 

between Progressive, Embryonic, and minent and most instructive, and 

Prophetic Types in the Succession of here and there some condensed ac< 

Organized Beings ; Proceed. 2nd counts of the facts in more elemen- 

Meeting Amer. Assoc, for the Ad- tary works, by the side of the origi- 

vancement of Science, held at Cam- nal papers. 



DIVEBSIFIED TYPES FOUND EVERYWHERE. 15 



SECTION IL 

SIMULTAKEOUS EXISTENCE OF THE MOST DIYEBSIFIED TYPES 

UNDEB IDENTICAL CIBCUMSTANCES. 

It is a fact, which seems to be entirely overlooked by 
those who assume an extensive influence of physical 
causes upon the very existence of organized beings, that 
the most diversified types of animals and plants are every- 
where found under identical circumstances. The smallest 
sheet of fresh water, every point upon the sea-shore, every 
acre of dry land teems with a variety of animals and plants. 
The narrower the boundaries which are assigned as the 
primitive home of all these beings, the more uniform must 
be the conditions under which they must be assumed to 
have originated ; so uniform, indeed, that in the end the 
inference would be, that the same physical causes can 
produce the most diversified effects.^ To concede, on 

^ In order to appreciate fully the pearance, the conditions necessary to 
difficulty alluded to here, it is only their growth must have been pro- 
necessary to remember how compli- vided for, if, as I believe, they were 
cated, and at the same time how created as eggs,— which conditions 
localized, the conditions are, under must have been conformable to those 
which animals multiply. The egg in which the living representatives of 
originates in a special organ, the the types first produced now repro- 
ovaiy ; it grows there to a certain duce themselves. If it were assumed 
sise, until it requires fecundation, — that they originated in a more ad- 
that is, the influence of another liv- vanced stage of life, the difficulties 
ing being, or, at least, of the product would be still greater, as a moment's 
of another organ, the spermary, — to consideration cannot fail to show, 
determine the further development especially if it is remembered how 
of the germ, which, under the most complicated the structure of some of 
diversified conditions, in different the animals was which are known to 

rsies, passes successively through have been among the first inhabit- 
ihose changes which lead to the ants of our globe. When investigat- 
formation of a new perfect being. I ing this subject, it is of course neces- 
would ask then. Is it probable that sary to consider the first appearance 
the circumstances under which ani- of animals and plants upon the basis 
mala and plants originated for the of probabilities only, or even simply 
first time can be much simpler, or upon that of possibilities ; as with re- 
even as simple, as the conditions ference to the first-bom, at least, the 
necessary for their reproduction only transmutation theory furnishes no 
after they have once been created ? explanation of their existence. For 
Preliminary, then, to their first ap- every species belonging to the first 



1 6 ESSAY ON CLASSIFICATION. 

the contrary, that these organisms may have appeared 
in the beginning over a wide area, is to grant, at the 
same time, that the physical influences under which they 
existed at first were not so specific as to justify the as- 
sumption that these could be the cause of their appear- 
ance. In whatever connection, then, the first appearance 
of organized beings upon earth is viewed, whether it is 
assumed that they originated within the most limited 
areas, or over the widest range of their present natural 
geographical distribution, anrmaJs and plants being every- 
where diversified to the most extraordinary extent, it is 
plain that the physical influences under which they sub- 
sist cannot logically be considered as the cause of that 
diversity. In this, as in every other respect, when con- 
sidering the relations of animals and plants to the condi- 
tions under which they live or to one another, we are 
inevitably led to look beyond the material facts of the 
case for an explanation of their existence. Those who 
have been led to take another view of this subject have 
mistaken the action and reaction which exist everywhere 
between organized beings, and the physical influences 
under which they live,^ for a casual or genetic connec- 
tion, and carried their mistake so far as to assert that 
these manifold influences could really extend to the pro- 
duction of these beings ; not considering how inadequate 
such a cause would be, and that even the action of physi- 
cal agents upon organized beings presupposes the very 
existence of those beings.^ The simple fact that there 

fauna and the first flora which have while, in a wider area, physical agents 
existed upon earth, special relations, are too uniform in their mode of ac- 
special contrivances must, therefore, tion to have laid the foundation for 
have been provided. Now, what would so many specific differences as ex- 
be appropriate for the one would not isted between the first inhabitants 
suit the other, so that, excluding one of our globe, 
another in this way, they cannot ^ See below, Sect. 16. 
have originated upon the same point; ' A Critical examination of this 



DIVERSIFIED TYPES FOUND EVERYWHERE. 17 

has been a period in the history of our earth, now well 
known to geologists,^ when none of these organized beings 
as yet existed, and when, nevertheless, the material con- 
stitution of our globe and the physical forces acting upon 
it were essentially the same as they are now,^ shows that 
these influences are insufficient to call into existence any 
living being. 

point maj dispel much of the coDfu- there are neither agents nor laws in 
sion which prevails in the discussions nature known to physicists, under the 
relating to the influence of physical influence, and by the action of which, 
causes upon organized beings. That these beings could have originated ; 
there exist definite relations between that, on the contrary, the very nature 
animals as well as plants and the of these beings and their relations 
mediums in which they live, no one to one another and to the world in 
at aU familiar with the pheoomena which they live exhibit thought, and 
of the organic world can doubt ; that can therefore be referred only to the 
these mediums, and all physical immediate action ofa thinking being, 
agents at work in nature, have a cer- even though the manner in which 
tain influence upon organized beings, they were called into existence re- 
is equally plain. But, before any such mains for the present a mystery. 
action can take place and be felt, ^ Few geologists only may now be 
organized beings must exist. The incliued to believe that the lowest 
problem before us involves, there- strata known to contain fossils are 
fore, two questions, the influence of not the lowest deposits formed since 
physical agents upon animals and the existence of organized beings 
plants already in existence, and the upon earth. But, even those who 
origin of these beings. Granting the would assume that still lower fos- 
influence of these agents upon organ- siliferous beds may yet be disco- 
ized beings to the fullest extent to vered, or may have entirely disap- 
which it may be traced (see Sect, peared, by the influence of plutonic 
16), there remains still the question agencies (Powell's Essays, etc., p. 
of their origin, upon which neither 424), must acknowledge the fact, 
argument nor observation has yet that, everywhere in the lowest rocks 
thrown any light. But, according to known to contain fossils at all, there 
some, they originated spontaneously is a variety of them found together, 
by the immediate agency of physical (See Sect. 7.) Moreover, the simi- 
forces, and have become successively larity in the character of the oldest 
more and more diversified by changes fossils found in different parts of the 
produced gradually upon them by world goes far, in my opinion, to 
these same forces. Others believe that prove that we actually do know the 
there exist laws in nature which were earliest types of the animal kingdom 
established by the Deity in the be- which have inhabited our globe. This 
ginning, to the action of which the conclusion seems fully sustained by 
origin of organized beings may be the fact, that we find everywhere, 
ascribed ; while, according to others, below this oldest set of fossiliferous 
they owe their existence to the im- beds, other stratified rocks, in which 
meoiate intervention of an intelli- no trace of organized beings can be 
gent Creator. It is the object of the found, 
following paragraphB to show that ' See below, Sect. 21. 

C 



1 8 ESSAY ON CLASSIFICATION. 

Physicists, indeed, know these physical agents more 
accurately than the naturalists who ascribe to them the 
origin of organized beings. Let us then ask them, whe- 
ther the nature of these agents is not specific, and whether 
their mode of action is not specific ? They will all answer 
that they are. Let us further inquire of them, what evi- 
dence is there, in the present state of our knowledge, that 
at any time these physical agents have produced any thing 
they no longer do produce, and what probability is there 
that they ever have produced any organized being ? If I 
am not greatly mistaken, the masters in that department 
of science will, one and all, answer, none whatever. 

But the character of the connections between organized 
beings and the physical conditions under which they live 
is such as to display thought;^ these connections are 
therefore to be considered as estabhshed, determined and 
regulated by a thinking being. They must have been 
fixed for each species at its beginning ; while the fact of 
their permanency through successive generations ^ is fur- 
ther evidence, that with their natural relations to the 
surrounding world were also determined the relations of 
individuals to one another,^ their generic as well as their 
family relations, and every higher grade of aflSnity;* 
showing, therefore, not only thought in reference to the 
physical conditions of existence, but such comprehensive 
thoughts as would embrace simultaneously every charac- 
teristic of each species. 

Every fact relating to the geographical distribution of 
animals and plants might be alluded to in confirmation of 
this argument, but especially the character of every fauna 
and every flora upon the surface of the globe. How great 

* Sco below, Sect. 16. « See below, Sect. 17. 

' See below, Sect. 15. * See below, Sect. 6. 



l'« 



DIVERSIFIED TYPES FOUND EVERYWHERE. 19 

the diversity of animals and plants living together in the 
same region may be, can be ascertained by the perusal of 
special works upon the Zoology and Botany of different 
countries, or fix)m special treatises upon the geographical 
distribution of animaJa and plants.^ I need not enter, 
therefore, into further details upon this subject, especially 
since it is discussed more fully below.^ 

It might, perhaps, be urged, that animals living toge- 
ther in exceptional conditions, and exhibiting structural 
peculiarities apparently resulting from these conditions, 
such as the blind fish,^ the blind crawfish, and the blind 
insects of the Mammoth Cave in Kentucky, furnish un- 
controvertible evidence of the immediate influence of 
those exceptional conditions upon the organs of vision. 
K this, however, were the case, — how does it happen that 
that remarkable fish, the Amblyopsis spelcmiSy has only 
remote aflSnities to other fishes ? Or were, perhaps, the 
sum of influences at work to make that fish bUnd, capable 
also of devising such a combination of structural charac- 
ters as that fish has in common with all other fishes, with 

^ ScHMABDA, Die geographische n6e; 2 vols., Bvo., Paris, 1855. Re- 

Verbreitung der Thiere ; 3 vols. 8vo., ferences to special works may be found 

Wien, 1853,— SWAIN805 ( W.), A Trea- below, Sect. 9. 

tise on the Geography and Classifica- * See below, Sect. 9. 

lion of Animals; London, 1836, 1 vol. ' Wymah (Jbf.), Description of a 

12mo.— ZiMMEBMANV (E. A. G.), Spe- Blind Fish, from a Cave in Kentucky, 

dmen Zoologies eeographicse, Quad- Silliman^s Jour., 1843, vol. 45, p. 94, 

rupedum domicuia et migrationes and 1854, vol. 1?, p. 258. — Tell- 

sistens ; Lugduni-Batav., 1777, 1 vol., kampp (Th. G.), Ueber den blinden 

4to. — Humboldt, Essai sur la g6o- Fisch der Mammuthhdhle in Ken- 

graphie des Plan tes ; 4to., Paris, 1805; tucky, in Miiller's Archiv, 1844, p. 

and Ansichten der Natur, 3rd edit., 381. — Tellkampp (TH.G.),Bc8chrei- 

12mo., Stuttgardt and Tubingen, bung einiger neuer in der Mammuth- 

1849. — RoBBBT Bbowv, General Re- hShle aufgefundener Gattungen von 

marks on the Botany of Terra Aus- Gliederthieren, Wieomak's Archiv, 

tralis; London, 1814. — Schouw, 1844, vol. i, p. 318.— Agassiz (L.), 

Grundzt^e einer aUgemeinen Pflan- Observations on the Blind Fish of the 

zengeomphie; 1 vol. 8vo., with atlas Mammoth Cave, Silliman's Journal, 

in foL, Berlin, 1823.— Alph. de Can- 1851, vol. 11, p. 127. 
DOLLS^ Q^graphie botanique raison- 

C2 



20 ESSAY ON CLASSIFICATION. 

those peculiarities which at the same time distinguish it ? 
Does not the existence of a rudimentary eye discovered 
by Dr. J. Wyman in the blind fish show, on the contrary, 
that these animals, like all others, were created, with all 
their peculiarities, by the fiat of the Almighty, and that 
this rudiment of eyes was left them as a remembrance of 
the general plan of structure of the great type to which 
they belong ? Or will, perhaps, some one of those natu- 
ralists who know so much better than the physicists what 
physical forces may produce, and that they may produce, 
and have produced every living being known, explain 
also to us why subterraneous caves in America produce 
blind fishes, blind Crustacea, and blind insects, while 
in Europe they produce nearly blind reptiles ? If there 
is no thought in the case, why is it, then, that this very 
reptile, the Proteus anguinuSy forms, with a number of 
other reptiles living in North America and in Japan, one 
of the most natural series known in the animal kingdom, 
every member of which exhibits a distinct grade ^ in the 
scale ? 

After we have freed ourselves from the mistaken im- 
pression that there may be some genetic connection be- 
tween physical forces and organized beings, there remains 
a vast field of investigation, to ascertain the true relations 
between both, to their full extent, and within their natural 
limits.^ A mere reference to the mode of breathing of 
different types of animals, and to their organs of locomo- 
tion, which are more particularly concerned in these rela- 
tions, will remind every naturalist of how great import- 
ance in Classification is the structure of these parts ; and 
how much better they might be understood, in this point 
of view, were the different structures of these organs more 

» See below, Sect. 12. "See below, Sect. 16. 



IDENTICAL TYPES FOUND EVERYWHERE. 21 

extensively studied in their direct reference to the world 
in which animals live. If this had been done, we should 
no longer call by the same common name of legs and 
wings, organs so diflFerent as the locomotive appendages 
of insects and those of birds ! We should no longer call 
the breathing cavities of snails lungs, as well as the air- 
pipes of mammalia,, birds and reptiles I A great reform 
is indeed needed in this part of our science ; and no 
study can better prepare us for it than the investigation 
of the mutual dependence of the structure of animals and 
of the conditions in which they live. 



SECTION III. 

BEF£TITION OF IDENTICAL TYFE8 UNDER THE MOST 
DITEB8IF1ED CIBCUMSTANCES. 

As much as the diversity of animals and plants Uving 
under identical physical conditions shows the independ- 
ence of organized beings of the medium in which they 
dwell, so far as their origin is concerned, so independent 
do they appear again of the same influences when we 
consider the fact that identical types occur everywhere 
upon earth under the most diversified circumstances. If 
we sum up all these various influences and conditions of 
existence under the common appellation of cosmic influ- 
ences, or of physical causes, or of climate in the widest 
sense of the word, and then look around us for the ex- 
treme diflferences in that respect upon the whole surface 
of the globe, we find still the most similar, nay, identical 
types, (and I allude here, under the expression of type, to 
the most diversified acceptations of the word,) living nor- 
mally under their action. There is no structural diff'cr- 
ence between the herrings of the Arctic and those of 



22 ESSAY ON CLASSIFICATION. 

the Temperate zone, or those of the Tropics and those of 
the Antarctic regions : there is none between the foxes 
and the wolves of the most distant parts of the globe.^ 
Moreover, if there were any, and the specific diflfer^ 
ences existing between them were insisted upon, could 
any relation between these differences and the cosmic 
influences under which they live, be pointed out, which 
would at the same time account for the independence of 
their structure in general ? Or, in other words, how could 
it be assumed, that, while these causes produce specific 
differences, they at the same time produce generic iden- 
tity, family identity, ordinal identity, class identity, typi- 
cal identity? Identity in every thing that is truly 
important, high, and complicated in the structure of 
animals, produced by the most diversified influences, 
while at the same time these extreme physical differ- 
ences, considered as the cause of the existence of these 
animals, produce diversity in secondary relations only! 
What logic ! 

Does not all tliis show, on the contrary, that organized 
beings exhibit the most astonishing independence of the 
physical causes under which they live, — an independence 
so great that it can only be understood as the result of a 
power governing the physical causes themselves, as well 
as the existence of the animals and plants, and l)ringing 
all into harmonious relations by adaptations which can 
never be considered as cause and effect ? 

AMien naturalists have investigated the influence of 
physicid causes upon living beings, they have constantly 
overlooked the fact that the features which are thus 



^ Innumerable other examples naturalibts. Those mentioned above 
might be quoted, which will readily maj suffice for my argument, 
present themselves to professionid 



UNITY OP PLAN IN DIVERSIFIED TYPES. 23 

modified are only of secondary importance in the life of 
RniTTiRlfl and plants, and that neither the plan of their 
structure nor the various complications of that structure 
are ever affected by such influences. What, indeed, are 
the parts of the body which are in any way affected by 
external influences ? Chiefly those which are in imme- 
diate contact with the external world, such as the skin, 
and in the skin chiefly its outer layers, its colour, the thick- 
ness of the fiir, the colour of the hair, the feathers, and the 
scales ; then the size of the body and its weight, as far as 
it is dependent on the quality and quantity of the food ; 
the thickness of the shell of Mollusks, when they live in 
waters or upon a soil containing more or less limestone, 
etc. The rapidity or slowness of the growth is also influ- 
enced in a measure by the course of the seasons in dif- 
ferent years ; so are also the fecundity, the duration of 
life, etc. But all this has nothing to do with the essential 
characteristics of animals. 

A book has yet to be written upon the independence 
of organized beings of physical causes ; for most of what 
is generally ascribed to the influence of physical agents 
upon organized beings ought to be considered as a con- 
nexion, established between them, in the general plan of 
the creation. 



SECTION IV. 

UNITY OF PLAN IN OTHEBWISE HIGHLY DIVEB8IFIED TYPES. 

Nothing is more striking, throughout the animal and 
vegetable kingdoms, than the unity of plan in the struc- 
ture of the most diversified types. From pole to pole, in 
every longitude, mammalia, birds, reptiles and fishes ex- 



24 ESSAY ON CLASSIFICATION. 

hibit one and the same plan of structure,^ involving ab- 
stract conceptions of the highest order, far transcending 
the broadest generalizations of man ; for it is only after 
the most laborious investigations that man has arrived at 
an imperfect imderstanding of this plan. Other plans^ 
equally wonderftd, may be traced in Articulata, in Mol- 
lusks, in Kadiata,^ and in the various types of plants.* 
And yet this logical connection, these beautiful harmo- 
nies, this infinite diversity in unity, are represented by 
some as the result of forces exhibiting no trace of intelli- 
gence, no power of thinking, no faculty of combination, no 
knowledge of time and space. If there is any thing which 
places man above all other beings in nature, it is precisely 

^ With reference to this point con- nisse der wirbellosen Thiere ; Braun- 
suit: Oken (Lor.), Ueber die Bedeut- schweig, 1848, 8vo. — Agassiz (L.), 
ung der Schadel-Knochen ; Frank- Twelve Lectures on Comparative Em- 
fort, 1807, 4to. (pamphlet.) — Spix bryology; Boston, 1849, 8vo. — On 
(J. B.), Gephalogenesis, sive capitis Animal Morphology, Proc. Amer. 
ossei structura, formatio et significa- Assoc, for the Adv. of Science ; Bos- 
tio; Monachii, 1815, fol. — Geoffrot ton, 1850, 8vo., p. 411. I would call 
St. HiL.viRB (£t.), Philosophic ana- particular attention to this paper, 
tomique; Paris, 1818-1823, 2 vols, which has immediate reference to the 
8vo., and several papers in the Annal. subject of this chapter. — Carus ( V.), 
des sc. nat., Annal. and M6m. du System der thierischen Morphologie; 
Museum, etc. — Carus (C. G.), Von Leipzig, 1853, 1 vol., 8vo. — MiiLLBB 
den Ur-Theilen des Knochen- und (J.), Ueber den Bau der Echinodcr- 
Schalengeriistes ; Leipzig, 1828, fol. men.; Akad. J. Wiss., Berlin, 1854, 4to. 
— OwEif (R.), On the Archetype and ' Qothb (J. W.), Zur Naturwiss- 
Homologies of the Vertebrate Skele- enschaft iiberhaupt, besondcrs zur 
ton; London, 1848, 8vo. Morphologie; Stuttgardt, 1817-24, 2 

' Oken (Lor.), Lehrbuch der Na- vols. 8vo.; French, (Euvrcsd'histoiro 

turphilosophie; Jena, 1809-1 1,3 vols, naturelle, comprenant divers m6- 

8vo. ; Engl. Elements of Physio-phi- moires d'Anatomie compar^e, de Bo- 

losophy, Ray Society, London, 1847, tanique et do G6ologie, traduits et 

8vo. — CuviER (G.), Sur un nouveau annot^ par Oh. Fr. Martins; Paris, 

rapprochement k 6tablir entre les 1837, 8vo.; atlas in fol. — De Oan- 

classes qui composent le R^gne Ani- dolle (A. P.), Organographie v6g6- 

mal, Annales du Museum, vol. xix, tale; Paris, 1827,2 vols. 8vo. — Braux 

1812. — Saviqxy (J. C), M6moires (Al.), Vergleichende Untersuchung 

sur les animaux sans vertM)res ; iiber die Ordnung der Schuppen an 

Paris, 1816, 8vo.-^Baer (C. E. v.), den Tanuenzapfen, als Einleitung zur 

Ueber Entwickelungsgeschichte der Untersuchung der Blattstellung iiber- 

Thiere, K5nigsbcrg, 1828, 4to. — haupt; Act. Nov. Ac. Nat. Ourios., 

LeucKART (R.), Ueber die Morpho- vol. xv, 1829. — Das Individuum der 

logie und dieVerwandtschaftsverh&lt- Pflanze, Akad.d.Wi8s,Berlin,l853,4to. 



HOMOLOGIES IN DISCONNECTED ANIMALS. 25 

the circumstance that he possesses those noble attributes, 
without which, in their most exalted excellence and per- 
fection, not one of these general traits of relationship, so 
characteristic of the great types of the animal and vege- 
table kingdoms, can be understood or even perceived. 
How, then, could these relations have been devised, with- 
out similar powers ? If all these relations are almost be- 
yond the reach of the mental powers of man, and if man 
himself is part and parcel of the whole system, how could 
this system have been called into existence, if there docs 
not exist One Supreme Intelligence as the Author of all 
things? 

SECTION V. 

C0RRE8F0KDENCE IN THE DETAILS OF STBUCTUBE IN ANIMALS 
0THEBWI8E ENTIRELY DISCONNECTED. 

During the first decade of this century, naturalists 
began to study relations among animals, which had 
escaped almost entirely the attention of earher observers. 
Though Aristotle already knew that the scales of fishes 
correspond to the feathers of birds,^ it is but recently 
that anatomists have discovered the close correspondence 
which exists between all the parts of all animals belonging 
to the same type, however difierent they may appear at 
first sight. Not only is the wing of the bird identical in 
its structure with the arm of man or the foreleg of a 
quadruped, but it agrees quite as closely with the fin 
of the whale or the pectoral fin of the fish ; and all 
these together correspond in the same maimer with their 

1 Aristoteles, Historia Animali- in Sect. 4, notes 1 and 2, and the 

um, Lib. i, Chap. 1, Sect. 4. h yhp many other works, pamphlets, and 

i9 SppiBi vrtphp, rovTo iv IxB&l iorX Xcvf s. papers quoted by them, which are too 

Consult also the authors referred to numerous to be mentioned here. 



26 ESSAY ON CLASSIFICATION. 

hind extremities. Quite as striking a coincidence is ob- 
served between the solid skull-box, the immoveable bones 
of the face, and the lower jaw of man and the other 
mammalia, and the structure of the bony frame of the 
head of birds, turtles, lizards, snakes, fix)gs and fishes. 
But this correspondence is not limited to the skeleton; 
every other system of organs exhibits in these animals 
the same relations, the same identity in plan and struc- 
ture, whatever be the differences in the form of the parts^ 
in their number, and even in their functions. Such an 
agreement in the structure of animals is called their 
homology, and is more or less close in proportion as the 
animals in which it is traced are more or less nearly 
related. 

The same agreement exists between the different sys- 
tems and their parts in Articulata, in Mollusks, and in 
Radiata, only that their structure is built upon respect- 
ively different plans, though in these three types the 
homologies have not yet been traced to the same extent 
as among Vertebrata. There is, therefore, still a wide 
field open for investigations in this most attractive branch 
of Zoology. So much, however, is already plain, fix>m 
what has been done in this department of our science, 
that the identity of structure, among animals, does not 
extend to all the four branches of the animal kingdom ; 
that, on the contrary, every great type is constructed 
upon a distinct plan, — so peculiar, indeed, that homo- 
logies cannot be extended from one type to the other, 
but are strictly Umited within each of them. The more 
remote resemblance which may be traced between repre- 
sentatives of different types is founded upon analogy,^ 

^ Sec SwAiNsoN (W.),On the Qeo- London, 1835, 12mo., p. 129, where 
graphy and Classification of Animals; this point is abljr discussed. 



HOMOLOGIES IN DISCOKNECTED ANIMALS. 27 

and not upon aflSnity. WHle, for instance, the head of 
fishes exhibits the most striking homology with that of 
reptiles, birds, and mammalia, as a whole, as well as in all 
its parte, that of Articulata is only analogous to it and to 
its part What is commonly called the head in Insecte is 
not a head like that of the Vertebrata : it has not a distinct 
cavity for the brain, separated from that which commu- 
nicates below the neck with the chest and abdomen ; ite 
solid envelope does not consist of parte of an internal 
skeleton surrounded by flesh, but is formed of external 
rings, like those of the body, soldered together ; it con- 
tains but one cavity, which includes the cephaUc gan- 
glion, as well as the organs of the mouth and all the 
muscles of the head. The same may be said of the chest, 
the legs and wings, the abdomen, and all the parte they 
contain. The cephalic ganglion is not homologous to the 
brain, nor are the organs of the senses homologous to 
those of Vertebrata, even though they perform the same 
functions. The alimentary canal is formed in a very dif- 
ferent way in the embryos of the two types, as are also 
their respiratory organs ; and it is as imnatural to identify 
them, as it would be stiU to consider gills and lungs as 
homologous among Vertebrata, now that Embryology has 
taught us, that in different stages of growth, these two 
kinds of respiratory organs exist in all Vertebrata in very 
different organic connections one from the other. 

What is true of the branch of Articulata when com- 
pared to that of Vertebrata is equally true of the Mol- 
lusks and Kadiata when compared with one another or 
with the two other tjrpes, as might easily be shown by a 
fuller illustration of the correspondence of their structure 
within these limite. This inequality in the fundamental 
character of the structure of the four branches of the 



28 ESSAY ON CLASSIFICATION. 

animal kingdom points to the necessity of a radical 
reform in the nomenclature of Comparative Anatomy.^ 
Some natm-alists, however, have already extended such 
comparisons respecting the structure of animals beyond 
the Umits within which they lead to correct results, when 
they have attempted to show that all structures may be 
reduced to one norm, and when they have maintained, 
for instance, that every bone existing in any Vertebrate 
must have its counterpart in every other species of that 
type. To assume such a uniformity among animals would 
amount to denying to the Creator even as much freedom 
in expressing his thoughts as man enjoys. 

If it be true, as pointed out above, that all a.nimal8 are 
constructed upon four different plans of structure, in such 
a maimer that all the different kinds of animals are only 
different expressions of these fundamental formulae, we 
may well compare the whole animal kingdom to a work 
illustrating four great ideas, between which there is no 
other connecting link than the unity exhibited in the 
eggs in which their most diversified manifestations are 
first embodied in an embryonic form, to undergo a series 
of transformations, and appear in the end in that won- 
derful variety of independent living beings which inhabit 
our globe, or have inhabited it from the earliest period of 
the existence of life upon its surface. 

The most surprising feature of the animal kingdom 
seems to me, however, to rest neither in its diversity, nor 
in the various degrees of compHcation of its structure, nor 
in the close affinity of some of its representatives while 
others are so different, nor in the manifold relations of all 

* See AoASSiz (L.), On the Struc- Proc. of the Amer. Assoc, for the 

ture ftnd Homologies of Radiated Ani- Adv. of Science for 1849; Boston, 

mals, with Reference to the System- 1850, 1 vol. 8vo., p. 389. 
atic Position of the Ilydroid Poljpi, 



DEGREES AND KINDS OP RELATIONSHIP. 29 

of them to one another and the surrounding world ; but 
in the circumstance, that beings, endowed with such dif- 
ferent and such unequal gifts, should nevertheless consti- 
tute an harmonious whole, intelligibly connected in all its 
parts. 

SECTION VI. 

YARIOUS DEGREES ANP DTFFERENT KINDS OF RELATIONSHIP 

AMONG ANIMALS. 

The degrees of relationship existing between different 
animals are most diversified. They are not only akin as 
representatives of the same species, bearing as such the 
closest resemblance to one another, but different species 
may also be related as members of the same genus ; the 
representatives of different genera may belong to the 
same family ; and the same order may contain different 
famihes, the same class different orders, and the same 
type several classes. The existence of different degrees of 
aflSnity, between animals and plants which have not the 
remotest genealogical connection, which live in the most 
distant parts of the world, which have existed in periods 
long gone by in the history of our earth, is a fact beyond 
dispute ; at least, within certain limits, no longer contro- 
verted by well informed observers. Upon what can this 
be founded? Is it that the retentive capacity of the 
memory of the physical forces at work upon this globe is 
such, that, after bringing forth a tjrpe according to one 
pattern, in the infancy of this earth, that pattern was 
adhered to under conditions, no matter how diversified, 
to reproduce, at another period, something similar, and so 
on, through all ages, until, at the period of the establish- 
ment of the present state of things, all the infinitude of 
new ^niTTiRlfl and new plants which now crowd its surface 



30 ESSAY ON CLASSIFICATION. 

were cast in these four moulds, in such a manner as 
to exhibit, notwithstanding their complicated relations to 
the surrounding world, all those more deeply seated 
general relations that establish among them the different 
degrees of afl&nity which we may trace so readily in all 
the representatives of the same type ? Does all this really 
look more like the working of blind forces than like the 
creation of a reflective mind, establishing deliberately all 
the categories of existence which we recognize in nature, 
and combining them into that wonderful harmony, which 
unites all things into such a perfect system, that even to 
read it as it is established, or even with all the imperfec- 
tions of a translation, must be considered as the highest 
achievement of the maturest genius ? 

Nothing seems to me to prove more directly and more 
fully the action of a reflective mind, to indicate more 
plainly a deliberate consideration of the subject, than the 
different categories upon which species, genera, families, 
orders, classes, and branches are founded in nature, and 
manifested in material reality in a succession of indivi- 
duals, the life of which is limited in its duration to com- 
paratively very short periods. The great wonder in these 
relations consists in the fugitive character of the bearers 
of this complicated harmony. For, while species persist 
during long periods, the individuals which represent them 
arc ever changing, one set dying after the other in quick 
succession. Genera, it is true, may extend over longer 
periods ; families, orders and classes may even have existed 
throughout all periods during which animals have existed 
at all ; but, whatever may have been the duration of their 
existence, at all times these different divisions have stood 
in the same relation to one another and to their respec- 
tive branches, and havo always been represented upon 



EARLIEST TYPES OF ANIMALS. 31 

our globe in the same maimer, by a succession of ever 
renewed and short-lived individuals. 

As, however, the second chapter of this work is entirely 
devoted to the consideration of the different kinds and 
the different degrees of aflSnity existing among animals, I 
will not enter here into any details upon this subject, but 
simply recall the fact, that, in the course of time, investi- 
gators have agreed more and more with one another in 
their estimates of these relations, and built up systems 
more and more conformable to one another. This result, 
which is fully exemplified by the history of our science,^ 
is in itself suflBcient to show that there is a system in 
nature, to which the different systems of authors are suc- 
cessive approximations, more and more closely agreeing 
with it, in proportion as the human mind has understood 
nature better. This growing coincidence between our 
systems and that of nature shows, further, the identity of 
the operations of the human and the Divine intellect ; 
especially when it is remembered to what an extraor- 
dinary degree many a priori conceptions, relating to 
nature, have in the end been proved to agree with the 
reality, in spite of every objection at first offered to them 
by empiric observers. 

SECTION VII. 

SIMULTANEOUS EXISTENCE IN THE EARLIEST GEOLOGICAL 
PERIODS, OF ALL THE GREAT TYPES OF ANIMALS. 

It was formerly believed by geologists and palaeontolo- 
gists that the lowest animals first made their appearance 

^ Splz (J.), Ckschichte und Beur- — Db Blainyille (H.), Histoire des 

theUuDg fldler Sjrsteme in der Zoolo- sciences de Torganisation et de leurs 

ne; KCunberff, 1811, 1 vol. 8vo. — progi^s; Paris, 1847, 3 vols. 8vo. — 

GirriSR (G.), Histoire des progrds des Fouchet (F. A.), Histoire des sci- 

sdences naturelles ; Paris, 1826, 4 ences naturelles au moyen kge ; Pa- 

Tols. 8to. — Histoire des sciences na- ris, 1853, 1 vol. 8vo. Compare, also, 

turelles^etc.; Paris, 1841,5 vols. 8yo. Chap. II below. 



32 ESSAY ON CLASSIFICATION. 

upon this globe, and that they were followed by higher 
tmd higher types, until man crowned the series. Every 
geological museum, representing at aQ the present state 
of our knowledge, may now furnish the evidence that this 
is not the case. On the contrary, representatives of nume- 
rous families, belonging to aQ the four great branches of 
the animal kingdom, are well known to have existed 
simultaneously in the oldest geological formations.^ Never- 
theless, I well remember when I used to heur the great 
geologists of the time assert that the Corals were the first 
inhabitants of our globe, that Mollusks and Articulata 
followed in order, and that Vertebrates did not appear 
until long after these. What an extraordinary change the 
last thirty years have brought about in our knowledge, and 
in the doctrines generally adopted respecting the exist- 
ence of animals and plants in past ages ! However much 
naturalists may still difier in their views regarding the 
origin, the gradation, and the afl&nities of animals, they 
now all know, that neither Radiata nor Mollusks nor Arti- 
culata have any priority one over the other, as to the 
time of their first appearance upon earth ; and that, though 
some still maintain that Vertebrata originated somewhat 
later, it is universally conceded that they were already in 
existence towards the end of the first great epoch in the 
history of our globe. I think it would not be difficult to 
show, upon physiological groimds, that their presence 
upon earth dates from as early a period as any of the 

1 MuRCHisoN (R. I.), The Silurian Mountains; London, 1845, 2 Tola. 

System ; London, 1839, 1 vol. 4to. — 4to. — Hall (Jamks), Palaeontology 

MuRCHisoN (Sir R. I.), Siluria. The of New York; Albany, 1847-52, 2 

Ilistory of the Oldest Known Rocks toIs., 4to. — Barrande (J.), Syst^me 

containing Fossils; London, 1854, 1 silurien du centre de la Boh^me; 

vol. 8vo. — MuRCHisoN (R. I.), DB Prague and Paris, 1852, 2 vols. 4to. — 

Yerneuil (Ed.), and Kaiserlino Sedqwick (A.), and McCoy (Fr.), 

(Count Alex, von), The Geology of British Palieozoic Rocks and Fossils; 

Russia in Europe, and the Ural London, 1851-55, 4U>., 3 fasc. 



EABUEST TYPES OF ANIMALS. 33 

three other great types of the animal kingdom, since fishes 
exist wherever Eadiata, Mollusks and Articulata are 
found together, and the plan of structure of these four 
great types constitutes a sjrstem intimately comiected in 
its very essence. Moreover, for the last twenty years 
every extensive investigation among the oldest fossilifer- 
ous rocks has carried the origin of Vertebrata step by step 
farther back ; so that, whatever may be the final solution 
of this vexed question, so much is abeady established by 
innumerable facts, that the idea of a gradual succession 
of Badiata, MoUusks, Articulata and Vertebrata is for ever 
out of the question. It is proved beyond doubt, that Ra- 
diata^ MoUusca and Articulata axe everywhere found toge- 
ther in the oldest geological formations, and that very early 
Vertebrata are associated with them and have continued 
to be so through all geological ages to the present time. 
This shows that even in those early days of the existence 
of our globe, when its surface did not yet present those 
diversified features which it has exhibited in later periods, 
and which it exhibits in still greater variety now, animals 
belonging to all the great types now represented upon 
earth were simultaneously called into existence. It shows 
further, that, unless the ph3rsical elements then at work 
themselves devised such plans, and impressed them 
upon the material world as the pattern upon which 
Nature was to build for ever afterwards, no such general 
relations as exist among all animals of all geological 
periods as well as among those now living, could ever 
have existed. 

This is not all : every class among Eadiata, Mollusks 
and Articulata is known to have been represented in those 
earliest days, with the exception of the Acalephs^ and 

^ Acalephs hare been found in the Their absence in other formations 
Jorasdc tiimestone of Solenhofen. may be owing simply to the extraor* 

D 



34 ESSAY ON CLASSIFICATION. 

Insects only. It is, therefore, not only the plan of the 
four great types which must have been adopted then, 
but also the maimer in which these plans were to be exe- 
cuted ; the systems of form imder which these structures 
were to be clothed, and even the ultimate details of struc- 
ture which in different genera bear definite relations to 
those of other genera; the mode of differentiation of 
species, and the nature of their relations to the surround- 
ing media, must likewise have been determined; for the 
character of the classes is as well defined as that of the 
four great branches of the animal kingdom, or that of the 
families, the genera and the species. Again, the first 
representatives of each class stand in definite relations to 
their successors in later periods, and, as their order of 
appearance corresponds to the various degrees of compU- 
cation of their structure, and forms a natural series doeely 
linked together, this natural gradation must have been 
contemplated from the very beginning. There can be the 
less doubt upon this point, as man, who comes last, closes 
in his own cycle a series, the gradation of which points 
from the very beginning to him as its last term. I think 
it can be shown by anatomical evidence, that man is not 
only the last and highest among the living beings of the 
present period, but that he is the last term of a series, 
beyond which there is no material progress possible in 
accordance with the plan upon which the whole animal 
kingdom is constructed ; and that the only improvement 

dinary softness of their body. Insects the oldest geological periods, since 

are known as early as the Carbonife- representatives of the family of 

rous Formation, and may have ex- JiiUeparina occur in the Silurian 

isted before. — Since the publication rocks. 

of these remarks I have ascertained It remains only to be ascertained 

that MUUpora is not a Polyp, but now whether all the Zoantharia tabu- 

belongs to the Hydroids. It is thus lata are as truly Hydroids as the 

shown that Acalephs have existed in genuine MilUporina or not. 



EARLIEST TYPES OF ANIMALS. 35 

we can look for upon earth, for the future, must consist 
in the development of man's intellectual and moral 
facultiea^ 

The question has been raised of late, how far the oldest 
fossils known may truly be the remains of the first inha- 
bitants of our globe. No doubt extensive tracts of fos- 
siliferous rocks have been greatly altered by plutonic 
agencies, and their organic contents so entirely destroyed 
and the rocks themselves so deeply metamorphosed, that 
they now resemble eruptive rocks more closely than 
stratified deposits. Such changes have taken place again 
and again up to comparatively recent periods, and upon 
a very large scale. Yet there are entire continents — North 
America, for instance — in which the palaeozoic rocks have 
undergone little, if any alteration, and where the remains 
of the earliest representatives of the animal and vegetable 
kingdoms are as well preserved as in later formations. In 
such deposits, the evidence is satisfactory that a variety 
of animals belonging to diflferent classes of the great 
branches of the animal kingdom has existed simulta- 
neously from the beginning ; so that the assumption of a 
successive introduction of these types upon earth is flatly 
contradicted by well established and well known facts.^ 
Moreover, the remains found in the oldest deposits are 
everywhere closely allied to one another. In Russia, in 
Sweden, in Bohemia, and in various other parts of the 
world, where these oldest formations have been altered 
upon a more or less extensive scale, as well as in North 
America^ where they have imdergone little or no change, 
they present the same general character, and that close 

^ A0A88IZ (L.), An Introduction to versity and Number of Animals in 

the Study of Natural History ; New Geological Times ; Amer. Joum. of 

York, 1847, Sto., p. 57. Science and Arts, 2nd ser., vol. 17, 

* Aqabsiz (L.), The Primitiye Bi- 1854, p. 309. 

D 2 



36 ESSAY ON CLASSIFICATION. 

correspondence, in their structure and in the combination 
of their families, which shows them to have belonged to 
contemporaneous faunce. It would, therefore, seem that, 
even where metamorphic rocks prevail, the traces of the 
earliest inhabitants of this globe have not been entirely 
obliterated. 



SECTION VIII. 

THE GRADATION OF STBUCTUBE AMOKO AN1MAI.8. 

There is not only variety among aiumaJs aoid plante, 
but they diflFer also as to their standing, their rank, their 
superiority or inferiority, when compared one to another. 
But this rank is diflficult to determine ; for, while in some 
respects all animals are equally perfect, since they perform 
completely the part assigned to them in the general 
economy of nature,^ there are in other respects sudi 
strikii^ differences between them, that their very agree- 
ment in certain features points at their superiority or 
inferiority in regard to others. 

This being the case, the question first arises, Do all 
animals form one unbroken series, fix)m the lowest to the 
highest? Before the animal kingdom had been studied 
so closely as it has been of late, many able writers really 
believed that all animalft formed but one simple, conti- 
nuous series, the gradation of which Bonnet was particu- 
larly industrious in trying to ascertain.^ At a later period, 
Lamarck^ endeavoured to show further, that, in the com- 

^ Ehbbnbebo (C. G.)> Dm Natur- 2 vols. Bto. — Contemplations do la 

reich des Mensohen, oder das Reich Nature; Amsterdam, 1764*65, 2 volt, 

der willensfreien beseelten NaturkOr- Bto. — Paling^n^sie philosophique ; 

per, in 29 Classen Cibersichtlich ge- Gendre, 1769, 2 vols. Bvo. 
ordnet; Berlin, 1836 (folio), 1 sheet. ' Lamabck (J. B. db), Philoso- 

' BoNVBT (Oh.), Considerations sar phie soologique; Paris, 1809, 2 vols, 

lea corps organist ; Amsterdam, 1 762, 8to. 



GRADATION OF STRUCTURE AMONG ANIMALS. 37 

plication of their structure, all the classes of the animal 
kingdom represent only successive degrees; and he was so 
thoroughly convinced that classes constitute one graduated 
series, that in his sjrstematic arrangement he actually 
calls the classes " degrees of organization/' De Blainville,^ 
in the main, followed in the steps of Lamarck, though he 
does not admit quite so simple a series ; for he considers 
the MoUusks and Articulates as two diverging branches, 
ascending fix)m the Radiata, to converge again and unite 
in the Vertebrata. But now, since it is known how the 
great branches of the animal kingdom may be circum- 
scribed,^ notwithstanding a few doubtful points ; since it 

1 Blaivtilla ^H. D, !>■), De TOr- ^g. 2d edit.; Grund^tze der verglei- 

ganizadondesAnimaux; Pari8,1822, chenden Anatomie, Dresden, 1828, 

1 vol. 8vo. Syo. ; Engl, bj R. J. Gobi, Bath, 

* Besides the works reyiewed in 1827, 2 yols. Svo., Atlas. — Cabus (0. 

Chapter III, consult: Blumesbaoh G.)and Otto (A W.), Erlauterungs- 

(J. Fb.), Handbuch der vergleichen- tafeln zur rergleichenden Anatomie; 

den Anatomie; Gdttingen, 1824, 1 Leipzic, 1826-40, fol.—WAONEB (R.), 

Yol. 8to.; Engl., by W. Lawbsnce, Lehrbuch der yergleichenden Anato- 

London, 1827, 1 yoI. Syo. — Ouyisb, mie; Leipzic, 1834-35, 2 yoIs. 8yo.; 

(G.), LJB^ns d* Anatomie compar6e, Kngl. bj A. Tulk, London, 1844, 1 

rec. et publ. par MM. Dum&il et yoI. Syo.; 2nd edit., Lehrbuch der 

Dayemoj; Paris, 1800-1805, 5 yoIs. Zootomie,Leipzic, 1 843-44, IyoI.Syo., 

8yo.; 2de 6dlt., roY. par MM. F. G. 2nd yoI. by Fbet and Leuckabt; 

GirriEB et Laubillabd, Paris, 1836- Icones anatomicse, Leipzig, 1841, fol. 

39, 10 Yols. Syo. — Cuyieb (G.), Le — Gbamt (R. E.), Outlines of Com- 

lU^e animal di8tribu6 d*apr^ son paratiye Anatomy ; London, 1 835, 1 

organisation; Paris, 1817,4 Yols. Syo.; yoI. fol. — Jones (Btkeb^, A General 

2nd 6dit., 1829-30, 5 yoIs. Syo. ; 3e Outline of the Animal Kingdom ; 

6dit. illustr6e 1836 et suIy.; Engl. London, 1838-39, 1 yoI. Syo. fig.; 2nd 

Trans, by GairriTH, London, 1824, edit., 1854. — Todd (R. B.), OyclopsB- 

9 Yols. Syo. — Meckel (J. F.), System dia of Anatomy and Physiology; lK>n- 

der Yergleichenden Anatomie ; Halle, don, 1835-52, 4 yoIs. Syo. fig. — Aoas- 

1821-31, 6yo1s. 8yo.; French TransL, siz (L.) and Gould (A. A.), Princi- 

Paris, 1829-38, 10 yoIs. Syo. — Tbeyi- pies of Zodlogy; Boston, 1 yoI. 8yo., 

BAEUB (G. R.), Biologic, oder Philo- 2nd edit. 1851. — Owen (R.), Lectures 

sophie aer leoenden Natur; Gdttin- on the InYcrtebrate Animals; Lon- 

gen, 1802 16, 6 Yols. Syo.— Die Er- don, 1843, 1 yoI. fig.; 2nd edit. 1855. 

scheinongen und Gesetze des organis* — Lectures on the ComparatiYc Ana* 

chen Lebens; Bremen, 1831*37, 5 tomy of the Vertebrate Animals, 

Tols. Syo. — ^Delle Ghiajb, Istituzi- Fishes; London, 1846, 1 Yol. 8yo. fig. 

oni d'Anatomia e Fisiologia compa- — Siebold (C. Th.y.^ und Stannius 

rata; Napoli, 1832, 8yo.— Cabus (C. ^Uebk.), Lehrbuch der Ycrgleichen- 

G.), Lehrbuch der Yergleichenden den Anatomie; Berlin, 1845-46, 2 Yols, 

Anatomie; Leipzic, 1834, 2 yoIs. 4to., Syo.; 2nd edit, 1855; Engl. Trans. 



38 ESSAY ON CLASSIFICATION. 

is still more accurately known how most classes should 
be characterized, and what is their respective standing ; 
since every day brings dissenting views, respecting the 
details of Classification, nearer together, — ^the supposition 
that all a.TiiTnals constitute one continuous, graduated series 
can be shown to be contrary to nature. Yet, the greatest 
difficulty in this inquiry is to weigh rightly the respective 
standing of the four great branches of the whole animal 
kingdom ; for, although the inferiority of the Radiata may 
seem plain when they are compared with the bulk of the 
MoUusks or Articulata, or still more evident when they are 
contrasted with the Vertebrata, it must not be forgotten that 
the structure of most Echinoderms is far more complicated 
than that of any Bryozoon or Ascidian, of the tjipe of Mol- 
lusks, or that of any Helminth, of the type of Articulata, and 
perhaps even superior to that of the Amphioxus among 
the Vertebrata. These facts are so well ascertained, that 
an absolute superiority or inferiority of one type to the 
others must be unconditionally denied. As to a relative 
superiority or inferiority, however, determined by the 
bulk of evidence, though it must be conceded that the 
Vertebrata rank above the three other types, the question 
of the relative standing of MoUusks and Articulata seems 
to rest rather upon a difference in the tendency of their 
whole organization than upon a real gradation in their 
structure ; concentration being the prominent trait of the 
structure of MoUusks, whUe the expression ' outward dis- 
play^ would more naturally indicate that of Articulata; 

by W. J. Burnett, Boston, 1854. — Cambridge, 1856, 2 toIs. 8vo. — Ca- 

Bbromann (0.) und Leuckart (R.^, rub (J. V.), Icones Zootomicse, mit 

Vergleichende Anatomie und Phjsi- Original-beitragen von G. J. Allman, 

ologie ; Stuttgardt, 1852, I toI. 8vo. 0. Gcgenbauer, Th. H. Hayley, Alb. 

fig.— Van der Hobyen (F.), Hand- K511iker, H. Mailer, M. S. Scbultse, 

book of Zoology, translated from the C. Th. £. von Siebold und F. Stein, 

Dutch by the Ret. William Clabk; Leipzig, 1857, fol. 



GRADATION OF STEUCTURE AMONG ANIMALS. 39 

and SO it might seem as if MoUusks and Articulata were 
standing on nearly a level with one another, and as much 
above Kadiata as both stand below Vertebrata^ but con- 
structed upon plans expressing different tendencies. To 
appreciate more precisely these most general relations 
among the great types of the animal kingdom will require 
deeper investigations into the character of their plan of 
structure than have been made thus far.^ Let, however, 
the respective standing of these great divisions be what 
it may ; let them differ only in tendency, or in plan of 
structure, or in the height to which they rise, admitting 
their base to be on one level or nearly so ; so much is 
certain, thus far, that in each type there are representa- 
tives exhibiting a highly complicated structure, and others 
which appear very simple. Now the very fact that such 
extremes may be traced within the natural boundaries of 
each type shows, that, in whatever manner these great 
t3rpes are supposed to follow one another in a single 
series, the highest representative of the preceding type 
must join on to the lowest representative of the following, 
thus necessarily bringing together the most heterogeneous 
forms.2 It must be further evident, that, in proportion 
as the internal arrangement of each great type becomes 
more perfected, the greater is likely to appear the differ- 
ence at the two ends of the series, which are ultimately 
to be brought into connection with one another in any 
attempt to establish a single series for all animals. 

I doubt whether there is a naturalist now living who 
would object to an arrangement in which, to determine 

' I legret to be unable to refer here gressive, Embryonic, and Prophetic 

to the contents of a course of lectures Types; Proc. Am. Assoc, for 1849, 

which I delirered upon this subject, p. 432. 

in the Smithsonian Institution, in " Agassiz (L.), Animal Morpho- 

1S52. Compare, meanwhile, my pa- logy; Proc. Am. Assoc, for 1849, p. 

per, On the Differences betweenr Pro- 415. 



40 ESSAY ON CLASSIFICATION. 

the respective standing of Radiata, Polyps would be 
placed lo>resty Acalephs next, and Echinoderms highest 
A similar arrangement of MoUusks would bring Acephala 
lowest, Grasteropoda next and Cephalopoda highest. Arti- 
culata would appear in the following order: Wonns^ 
Crustacea and Insects. Vertebrata with the Fishes lowest, 
Eeptiles and Birds next, and Mammalia highest. I 
have here purposely avoided every allusion to contro- 
verted points. Now if MoUusks were to follow Kadiata in 
a simple series, Acephala should join on to the Echino- 
derms : if Articulata, Worms would be the connecting 
link We should then have either Cephalopods or Insects 
as the highest term of a series beginning with Eadiata, 
followed by MoUusks or by Articulates. In the first case, 
Cephalopods would be foUowed by Worms : in the second. 
Insects by Acephala. Again, the connection with Verte- 
brata would be made either by Cephalopods, if Articulata 
were considered as lower than MoUusks, or by Insects, if 
MoUusks were placed below Articulata. Who does not 
see, therefore, that in proportion as our knowledge of the 
true aflSnities of animals is improving, we accumulate 
more and more convincing evidence against the idea that 
the animal kingdom constitutes one simple series ? 

The next question would then be: Does the animal 
kingdom constitute several, or any number of graduated 
series ? In attempting to ascertain the value of the less 
comprehensive groups when compared to one another, the 
difficulties seem to be graduaUy less and less. It is already 
possible to mark out with tolerable precision the relative 
standing between the classes, though even here we do not 
yet perceive in aU the types the same relations. Among 
Vertebrata there can be no doubt that the Fishes are 
lower than the ReptUes, these lower than Birds, and that 



GRADATION OF STRUCTURE AMONG ANIMALS. 41 

Mammalia stand highest; and it seems equally evident, 
that in the main Insects and Crustacea are superior to 
Worms, Cephalopods to Gasteropods and Acephala, and 
Echinoderms to Acalephs and Polj^L But there are 
genuine Insects, the superiority of which over many Crus- 
tacea would be difficult to prove : there are worms which 
appear in every respect superior to certain Crustacea : the 
structure of the highest Acephala seems more perfect than 
that of some Grasteropods, and that of the Halcyonoid 
Polyps more perfect than that of many Hydroids. Classes 
do not therefore seem to be so Umited in the range of 
their characters, as to justify in every type a complete 
serial arrangement among them. But, when we come to 
the orders, it can hardly be doubted that the gradation of 
these natural divisions among themselves in each class 
constitutes the very essence of this kind of groups. As a 
^ial p^gmph^i, devoted U. the considStirn of .he 
character of orders in my next chapter, I need not dwell 
longer upon this point here.^ It will be sufficient for me 
to remark now, that the difficulties, with which geologists 
have met in their attempts to compare the rank of the dif- 
ferent types of animals and plants with the order of their 
succession in diflFerent geological periods, have chiefly 
arisen from the circumstance, that they have expected to 
find a serial gradation, not only among the classes of the 
same type, where it is only incomplete, but even among 
the types themselves, between which such a gradation 
cannot be traced. Had they limited their comparisons to 
the orders which are reaUy founded upon gradation, the 
result would have been quite different; but, to do this, 
requires more familiarity with Comparative Anatomy, with 
Embryology and with Zoology proper, than can naturally 

* See Chap. II, Sect. 3. 



42 ESSAY ON CLASSIFICATION. 

be expected of those, whose studies are chiefly devoted to 
the investigation of the structure of our globe. 

To appreciate fully the importance of this question of 
the gradation of animals, and to comprehend the whole 
extent of the difl&culties involved in it, a superficial ac- 
quaintance with the perplexing question of the order of 
succession of animals in past geological ages is by no 
means sufiicient. On the other hand, a complete familia- 
rity with the many attempts which have been made to 
establish a correspondence between the two, and with all 
the crudities which have been published upon this sub- 
ject, might dispel every hope to arrive at any satisfiEU^toiy 
result upon this subject, did it not now appear that the 
inquiry, to be conducted upon its true groimd, must be cir- 
cumscribed within different limits. The results at which 
I have aheady arrived, since I have perceived the mia- 
take imder which investigators have been labouring thus 
far in this respect, satisfy me that the point of view, under 
which I have presented the subject here, is the true one; 
and that, in the end, the characteristic gradation exhibited 
by the orders of each class will present the most striking 
correspondence with the character of the succession of the 
same groups in past ages, and afford another startling 
proof of the admirable order and gradation in the de- 
grees of comphcation of the structure of animals, which 
have been eijtablished from the very beginning and main- 
t4iined throughout all time. 

SECTION IX. 

RANGE OF THR OEOORAPIIICAL DISTRIBUTION OF ANIMALS. 

Tlie surface of the earth being formed partly by water 
and partly by land, and the organization of all living 



GEOGRAPHICAL RANGE OF ANIMALS. 43 

beings standing in close relation to the one or the other 
of these mediums, it is in the natm^ of things that no 
single species, either of animals or plants, should be uni- 
formly distributed over the whole globe. Yet there are 
some types of the animal, as well as of the vegetable king- 
dom, which are equably distributed over the whole surface 
of the land, and others which are as widely scattered in 
the sea; while others are limited to some continent or 
some ocean, to some particular province, to some lake, 
nay, to some very Umited spot of the earth's surface.^ 

As far as the primary divisions of animals are con- 
cerned, and the nature of the medium to which they are 
adapted does not interfere, representatives of the four 
great branches of the animal kingdom are everywhere 
found together. Eadiata, MoUusks, Articulata and Verte- 
brata occur together in every part of the ocean, in the 
Arctics as well as under the equator and near the 
southern pole, as far as man has penetrated : every bay, 
every inlet, every shoal is peopled by them. So universal 
is this association, not only at present but in all past 
geological ages, that I consider it as a sufficient reason to 
believe that fishes will be foimd in those few fossUife- 
rous beds of the Silurian System in which thus far they 
have not been foimd.^ Upon land we find equally every- 
where Vertebrata, Articulata and MoUusks, but no Ea- 
diata, this whole branch being limited to the waters ; 
but, afi far as terrestrial animals extend, we find repre- 

' The human race affords an ex- be circumscribed in the sea, and that 

ample of the wide distribution of a of the Goniodonts of South America 

terrestrial type : the Herring and the in the fresh waters. The Chaca of 

Mackerel families have an equally Lake Baikal is found nowhere else, 

wide distribution in the sea. The This is equally true of the Blindfish 

Mammalia of New Holland show how (AmUvopsis) of the Mammoth Cave, 

some families may be limited to one and of tne Proteus of the caverns of 

continent, the family of LabyrirUhici Carinthia. 

of the Indian Ocean how fishes may ' See above, Sect. 7. 



44 ESSAY ON CLASSIFICATION. 

sentatives of the other three branches associated, as we 
find them all four in the sea. Classes have already a 
more limited range of distribution. Among Badiata^ the 
Polypi, Acalephs and Echinoderms^ are not only all aqua- 
tic, but they are all marine, with a single exception,* — 
the genus Hydra, which inhabits fresh watera Among 
MoUusks,^ the Acephala are all aquatic, but partly ma- 
rine and partly fluviatile ; the Grasteropoda partly marine, 

^ For the geographical dlstribu- water Polyps, Alcjonella, Plumatel- 

tion of Radiata, consult: Dana (J. la, etc., are Bryozoa, and not true 

J>,)y Zoophytes. United States Ex- Polyps. 

ploring Expedition, under the com- * For the geographical distribution 

mand of Oh. Wilkes, U.8.N., Phila- of Mollusks consult : Lamabok (J. 

delphia, 1846, 1 vol. 4to.; Atlas, fol. B. de), Histoire naturelle des Ani- 

— Milne-EdwArds et Haime (Jul.), maux sans vert^bres, Paris, 1815-2S; 

Becherches sur les Poly piers, Ann. 7 vols. Sto.; 2de 6dit. augment^e de 

Sc. Nat. 3e s6r., vol. 9-18, Paris, 1848- notes par MM. DssHates et Miuri- 

52,8yo. — Eschscholtz (Fa.), System Edwards, Paris, 1835-43, 10 vdi. 

der Acalephen; Berlin, 1829, 4to., 8vo. — Ferussao (J. B. L. de). His- 

fig. — Lesson (R. Pr.), Histoire natu- toire naturelle des MoUusques tems- 

relle des Zoophytes, Acal^phes ; Paris, tres et fluyiatiles ; Paris, 18 1 9, 6t suir, 

1843,1vol. 8yo., fig. — K5lliker (A.), 4to., fig., fol., continue par Dbh 

Die Schwimmpolypen und Siphono- Hates. — Frussao (J. B. ti. ]>k) et 

phoren von Messina; Leipzic, 1853, Sander-Rano (A.), Histoire naturelle 

1 vol. fol., fig. — Leuckart (R.), Zoo- des Aplysiens; Paris, 1828, 4to., fig., 

logische Untersuchungen ; Giessen, fol. — Ferussac (J. B. L. de) et D*Om- 

1853, 4to.; Zur nahem Kenntniss der biont (A.), Monographie des C6pha- 

Siphonophoren von Nissa, Arch. f. lopodes cry ptodibranches; Paris, 1834- 

Naturg., 1854 ; Beitrage zur Kennt- 43, fol. — Martini (F. H. W.) und 

niss der Medusenfaune von Nissa, Chemnitz (J. H.), Keues systema- 

Arch.f. Katurg.,1856. — Geoenbauer tisches Conchy lien-Kabinet; Nfim- 

(C), Beitrage zur nahem Kenntniss berg, 1769-05, 11 vols. 4to., ^g.\ new 

der Schwimmpolypen, Zeitsch.f.wiss. edit, and continuation by ScHOBXBf 

ZooL, 1853; Versuch eines Systems and A. Wagner, completed by H. 0. 

derMedu8en,mit Beschreibung neuer Kiister, Numberg, 11 rols. 4to., fig. 

oderwenigbekannterformen,Zeit8ch. — Kiener (L. C), Species g6n4nd ^ 

f. wiss. Zool., 1856. — Vogt (C), Re- Iconographie des Coquilles yivantei; 

cherches sur les animaux inferieurs Paris, 1834, etsuiy,8T0., fig. — Rhtb 

de la M6diterran^; Qen^ye, 1854. — (Loyell), Conchologia iconica; a 

MuLLER (J.) und Trosohel (F. H.), complete Repertory of Species of 

System der Asteriden, Braunschweig, Shells, Pictorial and Descriptive; Lon- 

1842, 8vo., fig. — AoASSiz (L.), Cata- don, 1843, and foil., 4to.,fig. — Pfeif- 

loguoraisonn^ des families, des genres fer (L), Monographia Heliceorum 

et des espies de la Classe des Echi- yiventium ; Leipzig, 1847-48, 8vo. — 

nodermes, Ann. des Sc. Nat., 3e s^r., Ppeifper (L.), Monographia Pneu- 

Yol. 6-8; Paris, 1847, 8yo. monopomorum Yiventium ; Cassel, 

' 1 need luu*dly say in this con- 1852, 8vo., and all the special works 

nection that the so-called fresh- on Conchology. 



A 



GEOGRAPHICAL BANGE OF ANIMALS. 45 

partly fluviatile, and partly terrestrial ; while all Cepha- 
lopoda are marine. Among Articulata,^ the worms are 
partly marine, partly fluviatile and partly terrestrial, 
whUe many are internal parasites, Uving in the cavities or 
in the organs of other animals ; the Crustacea are partly 
marine and partly fluviatile, a few are terrestrial ; the In- 
sects are mostly terrestrial or rather aerial, yet some are 
marine, others fluviatile, and a large number of those 
which, in their perfect state, live in the air, are terrestrial 
or even aquatic during their earlier stages of growth. 
Among Vertebrata^ the Fishes are all aquatic, but partly 

^ The mode of distribution of free relating to the different orders of this 
mndparasiticWormSjin different parts class; but thej are mentioned in: 
of the world and in different animals, Percheroit (Ach. R.), Bibliographie 
may be ascertained from : Qrubb entomologique, Paris, 1837, 2 vols. 
(A. Ei>.),I>ieFamilienderAnneliden, Sto. — Aoassiz (L.), Bibliograpbia 
Wiegman*s Archiy, 1850. I mention Zoologise et Geologias; ageneiul cata- 
this paper in preference to any other logue of all books, tracts, and mo- 
work, as it is the only complete list moirs on Zodlogy and Geology, cor- 
of Annulata; and though tne local- rected, enlarged, and edited by U. E. 
ities are not given, the references Strickland; London, 1848-54,4 vols. 
may supply the deficiency. — Rupol- 8vo. (Ray Society.) 
PHI (K. A.) Entozoorum sive Vermi- ' For the geographical distribution 
um intestinalium Hbtoria naturalis; of Fishes, consult: Gutier (G.) and 
Amstelodami, 1808-10, 3 vols. 8vo., Yalenciennes (A.), Histoire natu- 
fig. — Entozoorum Synopsis; Berolini, relle des Poissons; Paris, 1828-1849, 
1819, 8to., fig. — GuRLT (E. F.), Ver- 22 vols. 8vo., fijic. — Muller (J.) und 
leiclmiss der Thiere, bei Welchen Henle (J.), Sprstematische Beschrei- 
Entozoen gefunden worden sind, bung der Plagiostomen; Berlin, 1841, 
Wiegman'fl Archiv, 1845, con tin. by fol., fig. — Richardson (Sir John), 
C^piin in the followingKo. — Dujar- Article ' Ichthyology,* in Encyclopss- 
Div (Fbl.), Histoire naturelle des diaBritannica; Edinburgh, 1856, 4to. 
Helminthes ou Yers intestinaux ; — DumISril (A. M. C), Ichthyologie 
Paris, 1844, 1 vol. 8vo. — Diesino (0. analytique ou essai d*une classifica- 
M.), HistoriaYermium,Yindob. 1850, tion naturelle des Poissons; Paris, 
2 vols. 8to. That of Chrustacea from 1856, 4to. For that of Reptiles : 
Milnb-Edwardb, Histoire naturelle DuMf ril (A. M. C.) et Bibron (G.), 
des Crustac^; Paris, 1834, 3 vols. 8vo. Erp^tologie g6n6rale, ou Histoire na- 
fig. — Dana (J. D.), Crustacea. Uni- turelle complete des Reptiles ; Paris, 
tod States Exploring Expedition, un- 1834-1 855, 9 vols. 8vo., ng. — Tbohudi, 
der the command of Ch. Wilkes, (J. J.), Classification der Batrachier, 
U.8.K., vol. xiT, Philadelphia, 1852, Keuch&tel, 1838, 4to. M6m. Soc. 
2 vols. 4to., atlas, fol. For the geo- Neuch., 2nd vol. — Fitzinobr (L. J.), 
graphical distribution of Insects I SystemaReptilium,Yindobon 89,1843, 
mnst refer to the general works on 8vo. For that of Birds : Gray (G. 
Entomolog7,a8 it would require pages R.), The Genera of Birds, illustrated 
to enumerato even the standard works with about 350 plates by D. W. 



46 



ESSAY ON CLASSIFICATION. 



marine and partly fluviatile ; the Reptiles are either 
aquatic or amphibious or terrestrial, and some of the 
latter are aquatic during the early part of their life ; the 
Birds are all aerial, but some more terrestrial and others 
more aquatic ; finally, the Mammalia, though all aSrial, 
live partly in the sea, partly in fresh water, but mostly 
on land. A more special review might show that this 
localization, in connection with the elements in which 
animals Uve, has a direct reference to peculiarities of 
structure of such importance that a close consideration of 
the habitat of animals, within the limits of the classeSi 
might, in most cases, lead to a very natural classification.^ 
But this is true only within the limits of the classes, and 
even here not absolutely, as in some the orders only, or 
the families only, are thus closely related to the elements; 
and there are even natural groups, in which this connec- 
tion is not manifested beyond the limits of the genera, and 
a few cases in which it is actually confined to the speciea 
Yet, in every degree of these connexions we find that 
upon every spot of the globe it extends simultaneously to 
the representatives of different classes, and even of dif- 
ferent branches, of the animal and vegetable kingdoms ; 
a circumstance which shows, that, when called into exist- 
ence in such an association, these various animals and 
plants were respectively adapted, with all the peculiaritieB 



Mitchell; London, 1844-1849, 3 vols, 
imp. 4to. — Bonaparte (C. L.), Con- 
spectus gencrum Ayium, Lugduni- 
Batavoruin, 1850, and seq., 8vo. For 
that of Mammalia: Wagner (A.), 
Die geographische Verbreitung der 
Saugthiere, Verhandl. dcr Akau. der 
Wissensch. in MCinchen, vol. iv. — 
PoMPPER (Herm.), Die Saugthiere, 
Vogcl und Amuhibicn, nach ihrer 
geographischen Verbreitung tabella- 
rish zusammengestellt; Leipzig, 1841, 



4to. — See also the works quoted 
above. Sect. 2, and the annual reporU 
in Wiegnian*8 Archiv, now editod bT 
Troschel ; the Catalogues of the Bri- 
tish Museum, of the Jardin dei 
Plantes, etc., furnish equally impor- 
tant information. 

^ AoABSiz (L.), The Natural Relm- 
tions between Animals and the Sle- 
ments in which thej live. Amer. 
Jour, of Sc. and Arts, 2d ser., toL 9, 
1800, 8vo., p. 309. 



GEOGRAPHICAL RANGE OF ANIMALS. 47 

of their kingdom, those of their class, those of their order, 
those of their genus, and those of their species, to the 
home assigned to them, and therefore were not produced 
by the nature of the place, or of the element, or by any 
other physical condition.^ To maintain the contrary, would 
really amoimt to asserting, that, wherever a variety of 
organized beings live together, no matter how great their 
diversity, the physical agents prevailing there must have 
in their combined action the power of producing such a 
diversity of structures as exists in animals, notwith- 
standing the dose connection in which these animals 
stand to them, or of working out an intimate relation to 
themselves in beings, whose essential characteristics have 
no reference to their nature. In other words, in all these 
animals and plants there is one side of their organization 
which has an immediate reference to the elements in 
which they Uve, and another which has no such connec- 
tion ; and yet it is precisely that part of the structure of 
animals and plante. which haa no dii^ct bearing upon the 
conditions in which they are placed in nature, which con- 
stitutes their essential, their typical character. This 
proves, beyond the possibility of an objection, that the 
elements in which animals and plants live (and under 
this expression I mean to include all that is commonly 
included imder the expressions of physical agents, phy- 
sical causes, etc.) cannot in any way be considered as the 
cause of their existence. 

^ ^ In the study of the geographical rous and most heterogeneous typet*, 

dif tribution of animals and plants under all possible variations of clima- 

and their relations to the conaitions tic influences, severally circumscribed 

under which they live, too little im- within the narrowest limits, seems to 

portance is attached to the circum- me to present the most insuperable 

stance that representations of the objection to the supposition that the 

most diversified types are everywhere organized beings, so combined, could 

found associatedyWithin limited areas, in anyway have originated sponta- 

under identical conditions of exist- neously by the working of any natu- 

ence. These combinations of nume« ral law. 



48 ESSAY ON CLASSIFICATION. 

If the naturalists of past centuries have fEiiled to im- 
prove their systems of Zoology by introducing considera- 
tions derived from the habitat of animals, it is chiefly 
because they have taken this habitat as the foundation of 
their primary divisions. But, reduced to its proper limits^ 
the study of the connexion between the structure and the 
natural home of animals cannot fail to lead to interesting 
results, among which the growing conviction that these 
relations are not produced by physical agents, but deter- 
mined in the plan ordained from the beginning, will not 
be the least important. 

The imequal limitation of groups of a different value 
upon the surface of the earth produces the most diversi- 
fied combinations possible, when we consider the mode of 
association of different families of animals and plants in 
different parts of the world. These combinations are so 
regulated that every natural province has a character of 
its own, as far as its animals and plants are concerned; 
and such natural associations of organized beings, extend- 
ing over a wider or narrower area, are called FauruB, when 
the animals alone are considered, and FlorcBy when the 
plants alone are regarded. Their natural Hmits are far 
from lx?ing yet ascertained satisfactorily everywhere. As 
tlie works of Schow and Schmarda may suffice to give an 
approximate idea of their extent,^ I would refer to them 
for further details, and allude here only to the imequal 
cxtc^nt of these different faunae, and to the necessity of 
limiting them in different ways, according to the point of 
vi(jw under which they are considered; or rather show, 
that, as different groups have a wider or more limited 

* I would also refer to a sketch I (Philadelphia, 1854, 4to.), accom- 
havc publiiihed of the Faunas in NoTT*8 panied with a map and illuBtra- 
and Qliddon*8 Tjpea of Mankind tions. 



GEOGRAPHICAL RANGE OF ANIMALS. 49 

range, in investigating their associations, or the fannre, we 
must distinguish between zoological realms, zoological 
provinces, zoological coimties, zoological fields, as it were ; 
that is, between zoological areas of unequal value, over 
the widest of which range the most extensive types, while 
in their smaller and smaller divisions we find more and 
more limited types, sometimes overlapping one another, 
sometimes placed side by side, sometimes concentric to 
one another, but always and everywhere impressing a 
special character upon some part of a wider area, which is 
thus made to differ from any other part within its natural 
limits. 

These various combinations of smaller or wider ai-eas, 
equally well defined in different types, have given rise to 
the conflicting views prevailing among naturaUsts respect- 
ing the natural limits of faunae ; but, with the progress of 
our knowledge, these discrepancies cannot fail to disap- 
pear. In some respect, every island of the Pacific upon 
which distinct animals are found may be considered as 
exhibiting a distiact fauna; yet several groups of these 
islands have a common character, which unites them into 
more comprehensive faimae ; the Sandwich Islands for in- 
stance, compared with the Fejees or with New Zealand. 
What is true of disconnected islands or of isolated lakes 
is equally true of connected parts of the mainland and of 
the ocean. 

Since it is well known that many animals are limited 
to a very narrow range in their geographical distribution, 
it would be a highly interesting subject of inquiry to 
ascertain what are the narrowest limits within which ani- 
mals of different types are circumscribed, as this would 
furnish the first basis for a scientific consideration of the 
conditions under which animals have been created. The 

E 



50 ESSAY ON CLASSIFICATION. 

time is passed, when the mere indication of the conti- 
nent whence an animal had been obtained could satisfy 
our curiosity ; and those naturalists who have an oppor- 
tunity of ascertaining closely the particular circumstances 
under which the animals they describe are placed in their 
natural homes, are guilty of a gross disregard of the inte- 
rests of science when they neglect to relate them. Our 
knowledge of the geographical distribution of Rnimalft 
would be far more extensive and precise than it is now, 
but for this neglect. Every new fact relating to the geo- 
graphical distribution of well-known species is as import- 
ant to science as the discovery of a new species. Cbuld 
we only know the range of a single animal as accurately 
as Alphonse de CandoUe has lately determined that of 
many species of plants, we might begin a new era in Zoo- 
logy. It is greatly to be regretted, that, in most works 
containing the scientific results of explorations of distant 
countries, only new species are described, when the mere 
enumeration of those already known might have added 
invaluable information respecting their geographical dis- 
tribution. The carelessness with which some naturalists 
distinguish species merely because they are found in dis- 
tant regions, without even attempting to secure specimens 
for comparison, is a perpetual source of erroneous conclu- 
sions in the study of the geographical distribution of 
organized beings, not less detrimental to the progress of 
science than the readiness of others to consider as identi- 
cal animals and plants which may resemble each other 
closely, without paying the least regard to their distinct 
origin, and without even pointing out the differences they 
perceive l)etween specimens from different parts of the 
world. The perfect identity of animals and plants living 
in very remote parts of the globe hiis so often l>een ascer- 



GEOGRAPHICAL RANGE OF ANIMALS. 51 

tained, and it is also so well known how closely species 
may be allied and yet differ in all the essential relations 
which characterize species, that such loose investigations 
are no longer justifiable. 

This close resemblance of animals and plants in distant 
parts of the world is the most interesting subject of inves- 
tigation with reference to the question of the unity of the 
origin of animals; and to that of the influence of physical 
agents upon organized beings in general. It appears to 
me, that, as facts now point distinctly to an independent 
origin of individuals of the same species in remote re- 
gions, or of closely allied species representing one another 
in distant parts of the world, one of the strongest argu- 
ments in favour of the supposition, that physical agents 
may have had a controlling influence in changing the 
character of the organic world, is gone for ever. 

The narrowest limits within which certain Vertebrata 
are circumscribed, are exemplified, among Mammalia, by 
some large and remarkable species : the Orang-Outangs 
upon the Sunda Islands; the Chimpanzee and the Gorilla 
along the western coast of Africa ; several distinct species 
of Rhinoceros about the Cape of Good Hope, and in Java 
^ and Sumatra; the Pinchaque and the common Tapir in 
South America, and the eastern Tapir in Sumatra; the 
East Indian and the African Elephant, the Bactrian Camel 
and the Dromedary, the Llamas, and the different kinds 
of wild Bulls, wild Goats, and wild Sheep, etc. ; among 
Birds by the African Ostrich, the two American Rheas, 
the Emeu {Dromceus) of New Holland, and the Casuary 
{Casuarivs gcdeatus) of the Indian Archipelago, and still 
more by the different species of doves confined to parti- 
cular islands in the Pacific Ocean ; among Reptiles, by the 
Proteus of the cave of Adelsberg in Carinthia, and the 

E 2 



52 



ESSAY OX CLASSIFICATION. 



Gopher {Testudo Polyphemus^ Auct.) of our Southern 
States ; and among Fishes, by the Blind Fish {Amhlyop»i$ 
speUtiis) of the Mammoth Cave. Examples of closely 
limited Articulata may not be so striking ; yet the Blind 
Crawfish of the Mammoth Cave, and the many parasites 
found only upon or within certain species of animals, are 
very remarkable in this respect. Among MoUusks I would 
remark the many species of land shells, ascertained by 
Professor Adams to occur only in Jamaica,^ among the 
West India Islands; and the species discovered by the 
United States Exploring Expedition upon isolated islands 
of the Pacific, and described by Dr. Gould.^ Even among 
Radiata many species might be quoted, among Echino- 
derms as well as among MedusaB and Polypi, which are 
only known from a few localities; but, so long as these 
animals are not collected with the special view of ascer- 
taining their geographical range, the indications of travel- 
lers must be received with great caution, and any gene- 
ralization respecting the extent of their natural areas would 
be premature, as long as the countiies they inhabit have 
not been more extensively explored.^ It is nevertheless 
true, as established by ample evidence, that, within defi- 
nite limits, all the animals occurring in different natural 
zoological provinces are specifically distinct. What remains 
to be ascertained more minutely is the pi-ecise range of 
each species, as well tis the most natural limits of the dif- 
ferent faunse. 



* Adamb (C. B.), Contributions to 
Conchology; New York, 1849-50, Svo. 
A series of pamphlets, full of original 
information. 

■ GoDLD (A. A.), Mollusks, United 
States Exploring Expedition, under 
the command of On. Wilkk8,U.S.N.; 
1 vol. 4to., Philadelphia, 1854. 



' With reference to the Echino- 
derms and Acalephs, I am able to 
state, that the species of the Atlantic 
shores of North America, found along 
the northern states, differ entirelj 
from those of the southern states, and 
these differ again from those of the 
Gulf of Mexico. 



STEUCTUEE AND GEOCKAPHICAL DISTRIBUTION. 53 



SECTION X. 

IDENTITY OF STRUCTITKE OF WIDELY DISTBIBUTED TYPES. 

It is not only when considering the diversification of 
the animal kingdom within limited geographical areas, 
that we are called upon in our investigations to admire 
the unity of plan which its most diversified types exhibit ; 
the identity of structure of these types is far more sur- 
prising, when we trace it over a wide range of country 
and within entirely disconnected areas. Why the animals 
and plants of North America should present such a strong 
resemblance to those of Europe and Northern Asia, whUe 
those of Australia are so entirely different from those of 
Africa and South America under the same latitudes, is 
certainly a problem of great interest, in connection with 
the study of the influence of physical agents upon the 
character of animals and plants in different parts of the 
world. North America certainly does not resemble Eu- 
rope and Northern Asia, more than parts of Australia 
resemble certain parts of Africa or of South America ; 
and, even if a greater difference should be conceded be- 
tween the latter than between the former, these dispa- 
rities are in no way commensurate with the difference or 
similarity of their organized beings, nor in any way 
rationally dependent one upon the other. Why should 
the identity of species prevailing in the Arctic not ex- 
tend to the Temperate zone, when it is as difficult to dis- 
tinguish many species of this zone, though different, as it is 
to prove the identity of certain arctic species where the 
continents converge towards the north; and when, besides, 
the species of the two zones mingle to a great extent 
at their boundaries ? Why are the antarctic species 



54 



ESSAY ON CLASSIFICATION. 



not identical with those of the arctic regions ? And why 
should a further increase of the average temperature in- 
troduce such completely new t3rpes, when even in the 
Arctics there are, where the different continents converge 
towards the North Pole, such strikingly peculiar types 
{Rhytina, for instance,) combined with those which are 
identical over the whole arctic area V- 

It may, at first sight, seem very natural that the arctic 
species should extend over the three northern continents 
converging towards the north pole, as there can be no 
insuperable barrier to the widest dissemination over this 
whole area of the animals that live in the glacial ocean, 
or upon parts of three continents which are almost bound 
together by ice. Yet, the more we trace this identity in 
detail, the more surprising does it appear, as we find in 
the Arctics as well as everywhere else, representatives of 
different types living together. The arctic Mammalia, be- 
longing chiefly to the families of Whales, Seals, Bears, 
Weasels, Foxes, Ruminants and Rodents, have, as Mam- 
malia, the same general structure as the Mammalia of any 
other part of the globe, and so have the arctic Birds, the 
arctic Fishes, the arctic Articulata, the arctic MoUusks, 
the arctic Riidiata, when compared with the representa- 
tives of the same types all over our globe. This identity 
extends to every degree of afiinity among these i^nima1«^ 
and the plants which accompany them : their orders, 



^ I beg not to be misunderstood. 
I do not impute to all naturalists the 
idea of ascribing all the differences 
or all the similarities of the organic 
world to climatic influences ; and I 
wish only to remind them that e^en 
the truest picture of the correlations 
of climate and geotrraphical distri- 
bution does not yet touch the ques- 
tion of origin, which is the point 



under consideration. Too little atten- 
tion has thus far been paid to the 
facts bearing upon the peculiar! tief 
of structure of animals in connexion 
with the range of their distribution. 
Such investigations are only begin- 
ning to be made, as native investi- 
gators are studying comp&ratiTely 
the anatomy of animals of different 
continents. 



nn 



STRUCTURE AND GEOGRAPHICAL DISTRIBUTION. 55 

their families, and their genera, as far as they have repre- 
sentatives elsewhere, bear everywhere the same identical 
ordinal, family, or generic characters. The arctic foxes 
have the same dental formula, the same toes and claws, in 
fact, every generic peculiarity which characterizes foxes, 
whether they live in the Arctics or in the temperate or 
tropical zone, in America, in Europe, in Africa, or in Asia. 
This is equally true of the seals and the whales ; the same 
details of structure which characterize their genera in the 
Arctics reappear in the Antarctics and the intervening 
spac^, as far as their natural distribution goes. This is 
equally true of the birds, the fishes, etc., etc. And let it 
not be supposed that it is only a general resemblance. By 
no means. The structural identity extends to the most 
minute details in the most intimate structure of the teeth, 
of the hair, of the scales, in the furrows of the brain, in 
the ramification of the vessels, in the folds of the internal 
surface of the intestine, in the comphcation of the glands, 
et€., etc. ; to peculiarities, indeed, which nobody but a 
professional naturalist conversant with microscopic ana- 
tomy would ever believe could present such precise and 
permanent characters. So complete, indeed, is this iden- 
tity, that, were any of these beings submitted to the 
investigation of a skilful anatomist after having been 
mutilated to such an extent that none of its specific 
characters could be recognized, yet not only its class, or 
its order, or its family, but even its genus, could be iden- 
tified as precisely as if it were perfectly well preserved in 
all its parts. Were the genera, which have a wide range 
upon the earth and in the ocean, few, this might be con- 
sidered as an extraordinary case ; but there is no class of 
animals and plants which does not contain many genera, 
more or less cosmopoUtan in their geographical distribution. 



56 ESSAY ON CLASSIFICATION. 

The number of animals which have a wide distribution is 
SO great, as far at least as genera are concerned, that, 
it may even fairly be said that the majority of them have 
an extensive geographical range. This amounts to the 
most complete evidence, that, as far as these genera ex- 
tend in their geographical distribution, animals, the struc- 
ture of which is identical within this range of distribution, 
are entirely beyond the influence of physical agents, un- 
less these agents have the power, notwithstanding their 
extreme diversity, within these very same geographical 
limits, to produce absolutely identical structures of the 
most diversified types.^ 

It must be remembered here that there are genera of 
Vertebrata, of Articulatii, of Mollusks, and of Radiata 
which occupy the same identical and wide geographical 
distribution ; and that, while the structure of their respec- 
tive representiitives is identical over the whole area, as 
Vertebrata, as Articulata, as Mollusks, as Eadiata, they 
are at the same time built upon the most dififerent plans. 
I hold this fact to be in itself a complete demonstration 
of the entire independence of the structure of animals of 

^ An example may scryc to bring circumscribed within the narrowest 

this argument nearer to those not limits; although a large number of 

familiar with Natural History. From them have representatiyes in other 

the Arctic Ocean to Cape Horn, Ame- parts of the world. It is plain, theie- 

ricH embraces such a variety of phy- fore, that physical agents cannot be 

sical features, that we may well sup- the cause of the existence of any of 

pose all the natural causes to which them, unless these agents act with 

the origin of organized beings could discrimination, producing mammalia 

be ascribed, to be or to have been of the same genus over the whole 

active within this range. Now there continent, and by the side of them 

is a peculiar kind of fox in Arctic other animals belonging to the most 

America ; others occur in the tem- diversified types, and agreeing with 

perate zone of that continent, and the extra- American representatives 

others again in more southern lati- of these types in every essential fea- 

tudcs. With them the most diversified ture. This is tantamount to assuming 

animals of every class are associated, that such an action is the work of a 

among which there are many types, rational being, 
the geographical range of which is 



STRUCTURE AND GEOGRAPHICAL DISTRIBUTION. 57 

physical agents ; and I may add that the vegetable king- 
dom presents a series of facts identical with these. This 
proves that all the higher relations among animals and 
plants are determined by other causes than by mere phy- 
sical influences. 

While all the representatives of the same genus are iden- 
tical in structure,^ the different species of one genus differ 
only in their size, in the proportions of their parts, in 
their ornamentation, in their relations to the surrounding 
elements, etc. The geographical rhnge of these species 
varies so greatly that it cannot afford in itself a criterion 
for the distinction of species. It appears fm-ther, that 
whUe some species which are scattered over very exten- 
sive areas, occupy disconnected pails of that area, other 
species, closely allied to one another, and which are gene- 
rally designated under the name of representative species, 
occupy respectively such disconnected sections of these 
areas. The question then arises, how these natural boun- 
daries assigned to every species are established. It is now 
generally beheved that each species had, in the beginning, 
some starting point, from which it has spread over the 
whole range of the area it now occupies ; and, that this 
starting point is still indicated by the prevalence or con- 
centration of such species in some particular part of its 
natural area, which, on that account, is called its centre of 
distribution or centre of creation, while at the external 
limits of the area its representatives thin out, as it were, 
occurring more sparsely, and sometimes in a reduced 
condition. 

It was a great progress in our science, when the more 
extensive and precise knowledge of the geographical dis- 
tribution of organized beings forced upon its cultivators 

^ Sc? hereafter, Chap. II, Sect. 5. 



58 ESSAY ON CLASSIFICATION. 

the conviction, that neither animals nor plants could 
have originated upon one and the same spot upon the 
surface of the earth, and thence have spread more and 
more widely until the whole globe became inhabited It 
was indeed an immense progress which freed science 
from the fetters of an old prejudice. For now that we 
have the facts of the case before us, it is difficult to con- 
ceive how, by assuming such a ^ual dissemination 
from one spot, the diversity which exists in every part of 
the globe could ever have seemed to be explained. But, 
even to grant distinct centres of distribution for each 
species, within their natural boimdaries, is only to meet 
the facts half way, as there are innumerable relations be- 
tween the animals and plants foimd everywhere associ- 
ated together, which must be considered as primitive, 
and cannot be the result of successive adaptation. And if 
this be so, it would follow that all animals and plants 
have occupied, from the beginning, those natural boun- 
daries within which they stand one to another in such 
harmonious relations.^ Pines have originated in forests, 
heaths in heaths, grasses in prairies, bees in hives, her- 
rings in shoals, buffiiloes in herds, men in nations.^ I see 
a striking proof that this must have been the case in the 
circumstance, that representative species, which, as dis- 
tinct species, must have had from the beginning a dif- 
ferent and distinct geographical range, frequentiy occupy 
sections of an area simultaneously inhabited by the re- 
presentatives of other species, which are perfectiy iden- 
tical over the whole area. By way of an example, I 
would mention the European and the American Widgeon, 

1 A0A88IZ (L.), Qeographical Dis- ' Aoassiz (L.), The Divonity of 
tributiou of Animals, Christian Ex- Origin of the liuman Races, Chris* 
aminor; Boston, 1850, Sto. (March.) tian Examiner; Boston, 1850, Sto. 



8TKUCTURE AND GEOGRAPHICAL DISTRIBUTION. 59 

{Anas Penelope and A. amiericana,) or the American 
and the European Red -headed Ducks, {A. ferina 
and A. en/throcephala,) which inhabit respectively the 
northern parts of the Old and New World in summer, 
and migrate further south in these same continents dur- 
ing winter; while the Mallard {A. Boschas) and the Scaup 
Duck {A. marila) are as common in North America as in 
Europe. What do these facts tell ? That all these birds 
originated together somewhere where they no longer occur, 
and established themselves in the end within the limits 
which they now occupy ? or, that they originated either in 
Europe or America, where, it is true, they do not live aU 
together, but only a part of them ? or, that they really origin- 
ated within the natural boundaries which they now occupy? 
I suppose with sensible readers I need only follow out the 
conclusions flowing from the last supposition. If so, the 
American Widgeon and the American Red-headed Duck 
originated in America, and the European Widgeon and 
the European Red-headed Duck in Europe. But what of 
the Mallard and the Scaup, which are equally common 
upon the two continents ? Did they first appear in Eu- 
rope, or in America, or simultaneously upon the two con- 
tinents? Without entering into further details, — as I 
have only desired to lay clearly a distinct case before my 
readers, from which the character of the argument, which 
applies to the whole animal kingdom, may be fully 
understood, — I say that facts lead, step by step, to the 
inference, that such birds as the Mallard and the Scaup 
originated simultaneously and separately in Europe and 
in America ; and that all animals originated in vast num- 
bers, indeed, in the average number characteristic of their 
species, over the whole of their geographical area, whether 
its surface be continuous, or disconnected by sea, lakes, or 



Go ESSAY ON CLASSIFICATION. 

rivers, or by differences of level above the sea^ etc. The 
details of the geographical distribution of animals exhibit^ 
indeed, too much discrimination to admit for a moment 
that it could be the result of accident ; that is, the result 
of the accidental migrations of the animals, or of the acci- 
dental dispersion of the seeds of plants. The greater the 
uniformity of structure of these widely distributed organ- 
ized Ix^ings, the less probable does their accidental distri- 
bution appear. I confess that nothing has ever surprised 
me so much as to see the perfect identity of the most 
delicate microscopic structures of animals and plants 
from the remotest pai-ts of the world. It was this striking 
identity of stinicture in the same types, this total inde- 
pendence of the essential characteristics of animals and 
plants of their distribution under the most extreme 
climatic differences known upon our globe, which led me 
to distrust the belief, then almost universal, that organized 
b(»ings are influenced by physical causes to a degree which 
essentially modifies theu* chiu-acter. 

SECTION XL 

COMMUNITY OF STRUCTURE AMONG ANIMALS LIVING IN THE 

SAME REGIONS. 

Tli(» most interesting result of the earliest investigations 
of the* fauna of Australia was the discovery of a type of 
aniinalrt, the Mai'supialia, prevailing upon this continental 
inlaiKl, which .are unknown in almost every other part of 
th(» world. Every student of Natural History now knows 
that th<*r(5 are no Quadrumana in New Holland, neither 
Moiikis nor Makis: no Imectivora, neither Shrews nor 
Moles, nor Hedgehogs; no tnio Caniivora} neither Bears, 
nor WcNisels, nor Foxes, nor Vivemus, nor Hyaenas, nor 

I DoubtM are entertained respecting the origin of the Dingo, the onlj 
livaMt of prey of Now Holland. 



COMMUNITY OF STRUCTURE. 61 

Wild Cats ; no Edentata^ neither Sloths, nor Tatous, nor 
Ant-Eaters, nor Pangohns ; no Pojchy deisms, neither Ele- 
phants, nor Hippopotamuses, nor Hogs, nor Ehinoceroses, 
nor Tapirs, nor Wild Horses; no Ruminantia, neither 
Camels, nor Llamas, nor Deer, nor Goats, nor Sheep, nor 
Bulls, etc.; and yet the Mammalia of Australia are almost 
as diversified as those of any other continent. In the 
words of Waterhouse,^ who has studied them with parti- 
cular care, " the Marsupialia present a remarkable diver- 
sity of structure, containing herbivorous, carnivorous and 
insectivorous species; indeed, we find amongst the Mar- 
supial animals analogous representations of most of the 
other orders of Mammalia. The Quadrumana are repre- 
sented by the Phalangers, the Carnivora by the Dasyuri, 
the Iiisectivora by the small Phascogales, the Ruminantia 
by the Kangaroos, and the Edeiitcvta by the Monotremes. 
The Cheiroptera are not represented by any known Mar- 
supial animals, and the Rodents arc represented by a single 
species only. The hiatus is filled up, however, in both 
cases, by placental species ; for Bats and Rodents are tole- 
rably numerous in Australia ; and, if we except the Dog, 
which, it is probable, has been introduced by man, these 
are the only placental Mammalia found in that conti- 
nent." Nevertheless, all these animals have in common 
some most striking anatomical characters, which distin- 
guish them from all other Mammalia, and stamp them as 
one of the most natural groups of that class. Their mode 
of reproduction, and the connection of the yoimg with- the 
mother, are different; so also is the structure of their 

brain, etc.^ 

Now, the suggestion that such peculiarities could be 

1 Watebhouse (G. a.), Natural pialia' in Todd's Cjclopredia of Anat. 

HUtory of the Mammalia; London, and Physiol.; London, 1841, 8vo.; 

1848, 2 vols. Svc, vol. i, p. 4. and several elaborate paners by him- 

' See Owen (R.), article ' Marsu- self and others, quoted there. 



62 ESSAY ON CLASSIFICATION. 

produced by physical agents is for ever set aside by the 
fact that neither the birds nor the reptiles, nor, indeed, 
any other animals of New Holland, depart in such a man- 
ner from the ordinary character of their representatives 
in other parts of the world ; unless it can be shown that 
such agents have the power of discrimination, and may 
produce, under the same conditions, beings which agree, 
and others which do not agree, with those of different 
continents ; not to speak again of the simultaneous occur- 
rence, in that same continent, of other heterogeneous 
types of Mammalia, Bats and Rodents, which occur there 
as well as everywhere else in other continents. Nor is 
New Holland the only part of the world which nourishes 
animals highly diversified among themselves, and yet pre- 
senting common characters strikingly different fix)m those 
of the other members of their tjrpe, circumscribed within 
definite geographical areas. Almost every part of the 
globe exhibits some such group, either of animals or of 
plants, and every class of organized beings contains some 
native natural group, more or less extensive, more or less 
prominent, which is circumscribed within pecuhar geogra- 
phical limits. 

Among Mammalia we might quote the Quadrumana, 
the representatives of which, though greatly diversified in 
the Old as well as in the New World, differ and agree 
respectively in many important points of their structure; 
also the Edentata of South America. Among Birds, the 
Humming Birds, which constitute a very natural, beauti- 
ful, and numerous family, aU of which are nevertheless 
confined to America only, as the Pheasants are to the Old 
World. ^ Among Reptiles, the Crocodiles of the Old World 

^ ^Yhat are called Pheasants in The American Pheasants, so called, 
America do not even belong to the are genuine Qrouse. 
same family as the eastern Pheasants. 



SERIAL CONNECTION AMONG ANIMALS. 63 

compared with those of America. Among Fishes, the family 
of Labyrinthtciywlnch. is confined to the Indian and Pacific 
Oceans; and that of Goniodonts, which is limited to the 
fresh waters of South America, as that of Cestracionts is 
to the Pacific. The comparative anatomy of Insects is 
not sufficiently far advanced to famish striking examples 
of this kind. Among Insects, however, remarkable for 
tbeir form, which are limited to particular regions, may 
be quoted the genus Mormolyce of Java, Pneumora of 
the Cape of Good Hope, Bdostoma of North America, 
Ftdgora of China, etc. The geographical distribution 
of Crustacea has been treated in such a masterly manner 
by Dana, in his great work upon the Crustacea of the 
United States Exploring Expedition, vol. xiii, p. 1 451, that 
I need only refer to it for numerous examples of localized 
types of this class, and also as a model how to deal with 
such subjects. Among Worms, the genus Peripates of 
Guiana deserves to be mentioned. Among Cephalopods, 
Nautilus of Amboyna. Among Gasteropods, the genus lo 
of the western waters of the United States. Among Ace- 
phala, the genus Trigonia of New HoUand, certain Naiades 
of the United States, the genus Aet/ieria of the Nile. 
Among Echinodenns, Pentacrinus of the West Indies, Cul- 
cita of Zanzibar, Amhlypneustes of the Pacific, Temno- 
pleurus of the Indian Ocean, Dendraster of the western 
coast of North America. Among Acalephs, Berenice of 
New HoUand. Among Poljrpi, the true Fungidw of the 
Indian and Pacific Oceans, the genus ReniUa of the 
Atlantic, etc. 

Many more examples might be quoted, were our know- 
ledge of the geographical distribution of the lower animals 
more precise. But these will suffice to show, that, whether 
high or low, aquatic or terrestrial, there are types of ani- 



64 ESSAY ON CLASSIFICATION. 

mals remarkable for their peculiar structure which are 
circumscribed within definite limits, and this localization 
of special structures is a striking confirmation of the 
views expressed already in another connection, that the 
organization of animals, whatever it is, is adapted to 
various and identical conditions of existence, and can in 
no way be considered as originating from these condi- 
tions. 

SECTION XII. 

SERIAL CONKECTIOK IN THE STRUCTUBE OF ANIMALS WIDELY 
SCATTERED UPON THE SURFACE OF OUR GLOBE. 

Ever since I have become acquainted with the reptiles 
inhabiting different parts of the world, I have been struck 
with a remarkable fact, not yet noticed by naturalists, as 
far as I know, and of which no other class exhibits such 
striking examples. This fact is, that among Saurians, as 
well as among Batrachians, there are families, the repre- 
sentatives of which, though scattered all over the globe, 
form the most natural connected series, in which every 
link represents one particular degree of development. 
The Scincoids,^ among Saurians, are one of these familiea 
It contains about one hundred species, referred by Du- 
m^ril and Bibron to thirty-one genera, which, in the de- 
velopment of their organs of locomotion, exhibit most 
remarkable combinations, as illustrated in a diagram on 
opposite page. 

Fidly to appreciate the meaning of this diagram, it 
ought to be remembered that the animals belonging to 
this family are considered here in two different points of 

^ For the characters of the family, Cocteau, Etudes sur les Scincoides; 
see DuM^KiL ct Bibron, Erp^tologie Paris, 183C, 4to. fig. 
gC'ii^rale, vol. 5, p. 511. See also 



SERIAL CONNECTION AMONG ANIMALS. 65 

view. In the first place, their zoological relations to one 
another are expressed by the various combinations of the 
structures of their legs ; some having four legs, and these 
are the most numerous, others only two legs, which are 
always the hind legs, and others no legs at all. Agaiu, 
these legs may have only one toe, or two, three, four, or 
five toes, and the number of toes may vary between the 
fore and hind legs. The classification adopted here is 
based upon these characters. In the second place, the 
geographical distribution is noticed. But it is at once 
apparent that the home of these animals stands in no 
relation whatsoever to their zoological affinities. On the 
contrary, the most remote genera may occur in the same 
coimtry, while the most closely related may live far 
apart. 

GENERA WITH FOtJR LEGS. 

With^i^ toes to the fore feet as weU as to the hind feet : Tropidophorus, I 
species, Ooch in-China. — ScincuSy 1 sp., Syria, North and West Africa. 
— SphenopSy I sp., Egypt. — Diplo^lossus, 6 sp., West Indies and 
Brazils. — Amphi^losstis, 1 sp., Madagascar. — QongyluB, with 7 sub- 
genera : QongyhUy 2 sp., Southern Europe, Egypt, Teneriffe, Isle 
de France; Eumeces, 11 sp., East and West Indies, South America, 
Vanikoro, New Ireland, New Guinea, Pacific Islands ; Euprepes, 
13 sp., West Coast of Africa, Cape of Good Hope, Egypt, Abyssinia, 
Seychelles, Madagascar, New Guinea, East Indies, Sunda Islands, 
Manilla ; Plestiodon, 5 sp., Egypt, Algiers, China, Japan, United 
States ; Lygowma, 19 sp., New Holland, New Zealand, Java, New 
Guinea, Timor, East Indies, Pacific Islands, United States ; lAoh^ 
puma, 1 sp., Mauritius and Manilla; TropidolopUma, 1 sp.. New 
Holland. — Cyclodus, 3 sp.. New Holland and Java. — Trachysauru8, 
1 sp.. New Holland. — AbUphariu, 4 sp.. South-eastern Europe, New 
Holland, Pacific Islands. 

With /he toes to the fore feet and /our toes to the hind feet : Campsodacty' 
lu8, 1 sp., Bengal. 

With four toes to the fore feet and five toes to the hind feet : Heteropus, 3 
sp., Africa, New Holland, Isle de France. — Gymnophthalmus, 1 sp., 
W. Indies and Brazil. 



66 ESSAY ON CULSSIFICATIOK. 

With four toes to the fore feet and fow toes to the hind feet : Tttradaidf- 

liu, 1 sp., New HoIUnd. The genus Ckalcides, of the allied &milj 

Chalcidioidft, exhibits another example of this comhinatioo. 
With /o«r toes to the fore feet and three toes to the hind feet: No ezami^ 

known of this combination. 
With three toes to the fore feet and four toes to the hind feet: Not known. 
With three toes to the fore feet and three toes to the hind feet: Hemiergit, 

1 sp., New Holland. — Sep9y 1 sp., S. Europe and N. Africa. — Nema^ 

1 sp., Origin unknown. 
With three toes to the fore feet and tvBO toes to the hind feet: Not known. 
With two toes to the fore feet and three toes to the hind feet: Heieromdei^ 

1 sp., Algiers. — Leruta^ 1 sp.. New Ilolland. 
With two toes to the fore feet and two toes to the hind feet: CA€lomeUMj \ 

sp., New Holland. 
With ttco toes to the fore feet and one toe to the hind feet: BraekymeUsj 1 

8p., Philippine Islands. 
With one toe to the fore feet and tvo toes to the hind feet : Brmeh^Moput^ 

1 sp.. South Africa. 
With 07ie toe to the fore feet and one toe to the hind feet: BveM, 1 sp., 

Origin unknown. 

GENERA WITH ONLY TWO LEGS. 

No representatives are known with fore legs ordy; but this structural 
combination occurs in the allied family of the Chalcidioids. The represen- 
tatives with hind legs oidy present the following combinations: 

With two toes: SceLotee^ 1 sp., Cape Good Hope. 

With one toe: Propeditui, 1 sp., Cape Good Hope and New Holland. 

OphiodeSy 1 sp.. South America. 

Ilgsteropue, 1 sp., New Holland. 

Lialisy I sp.. New Holland. 

Dibamus, I sp., New Guinea. 

GENEilA WITHOUT ANY LEGS. 

Anguit, 1 sp., Europe, Western Asia, Northern Africa. 
OphiomortUy 1 sp., Morea, Southern Russia, and Algiers. 
Acontiatty 1 sp., Southern Africa, Capo Good Hope. 
TyiMintiy 1 sp.. Southern Africa, Cape Good Hope. 

Who can look at this diagram and not recognize, in it« 
arranfTcincnt, tli(.» comlnnations of thought ? This is so 
obviouH, that while eonsidering it one might almost over- 
look th(j fact, that, while it was drawn up to classify ani- 



SERIAL CONNECTION AMONG ANIMALS. G7 

mals preserved in the Museum of the Jardin des Plantes 
in Paris, it is in reality inscribed in nature by these ani- 
mals themselves, and is only read off when they are 
brought together, and compared side by side. But it con- 
tains an important element for our discussion. The series 
is not built up of equivalent representatives in its diffe- 
rent terms, some combinations being richly endowed, 
others numbering a few, or even a single genus, and 
others again being altogether disregarded. Such freedom 
indicates selection, and not the working of the law of 
necessity. 

And if, from a contemplation of this remarkable series, 
we turn our attention to the indications relating to the 
geographical distribution of these so closely linked genera 
inscribed after their names, we at once perceive that 
they are scattered all over the globe, but not so that 
there can be any connection between the combinations 
of their structural characters and their homes. The types 
without legs are found in Europe, in Western Asia, in 
Northern Africa, and at the Cape of Good Hope ; the 
types with hind legs only, and with one single toe, at the 
Cape of Good Hope, in South America, New Holland, and 
New Guinea ; those with two toes at the Cape of Good 
Hope only. Among the types with four legs, the origin of 
those with but one toe to each foot is unknown ; those 
with one toe in the fore foot and two in the hind foot are 
from South Africa ; those with two toes in the fore foot 
and one in the hind foot occur in the Philippine Islands ; 
those with two toes to all four feet in New Holland ; those 
with three toes to the hind feet and two to the fore feet, 
in Algiers and New Holland. None are known with three 
toes to the fore feet and two to the hind feet. Those with 
three toes to the fore feet inhabit Europe, Northern Africa, 

F 2 



68 ESSAY ON CLASSIFICATION, 

and New Holland There are none with three and four 
toes, either in the fore feet or in the hind feet Those 
with four toes to the fore feet live in New HoUand ; those 
with five toes to the fore feet and four to the hind feet, 
in Bengal ; and with four toes to the fore feet and five to 
the hind feet, in Africa, the West Indies, the Brazils^ and 
New Holland. Those with five toes to all four feet have 
the widest distribution ; and yet they are so scattered that 
no single zoological province presents any thing like a com- 
plete series. On the contrary, the mixture of some of the 
representatives with perfect feet with others which have 
them rudimentary in almost every faima, excludes still 
more decidedly the idea of any influence of physical agents 
upon this development. 

Another similar series, not less striking, may be traced 
among the tailed Batrachians ; for the characters of which 
I may refer to the works of Holbrook, Tschudi, and 
Baird,^ even though they have not presented these animals 
in this connection ; as the characteristics of the genera will 
of themselves suggest their order, and further details upon 
this subject would be superfluous for my purpose, the 
more so as I have already discussed the gradation of these 
animals elsewhere.^ 

Similar series, though less conspicuous and more limited, 
may be traced in every class of the animal kingdom, not 
only among living types, but also among the represen- 
tatives of past geological ages ; which adds to the interest 
of such series, as showing that such combinations in- 
clude not only the element of space, indicating omni- 

1 Holbrook (J. £.), North Ameri- trachia ; Journal Acad. Nat. Science, 

can Ilcrpetology; Philadelphia, 1842, of Philadelphia, 2nd series, Tol. i, 

4to., 5th vol. — Tschudi (J. J.), Clas- 1849, 4to. 

sification der Batrachier; Neuch&tcl, ' Agassiz (L.), Twelve Lectures 

1838, 4to. — Baird (Sp. P.), Revision on Comparative Embryology; Bostoiii 

of the North American Tailed Ba- 1849, 8vo., p. 8. 



SERIAL CONNECTION AMONG ANIMALS. 69 

presence, but also that of time, which involves prescience. 
The series of Crinoids, that of Brachiopods through all 
geological ages, that of the Nautiloids, that of Ammoni- 
toids from the Triassic to the Cretaceous formations inclu- 
sive, that of Trilobites from the lowest beds up to the 
Carboniferous period, that of Ganoids through all the for- 
mations ; then, again, among living animals in the class of 
Mammalia, the series of Monkeys of the Old World espe- 
cially, that of Camivora, from the Seals through the Plan- 
tigrades to the Digitigrades ; in the class of Birds, that 
of the Wading Birds, and that of the Gallinaceous Birds ; 
in the class of Fishes, that of Pleuronectids and Gadoids, 
that of Skates and Sharks ; in the class of Insects, that of 
Lepidoptera from the Tineina to the Papilionina ; in the 
class of Crustacea, that of the Decapods in particular ; in 
the class of Worms, that of the Nudibranchiata and that of 
the Dorsibranchiata especially ; in the class of Cephalo- 
poda, that of the Sepioids ; in the class of Gasteropoda, 
that of the Nudibranchiata in particular ; in the class of 
Acephala that of the Ascidians and that of the Oysters in 
the widest sense ; in the class of Echinoderms, those of the 
Holothurians and Asterioids ; in the class of Acalephs, that 
of the Hydroids ; in the class of Polyps, that of the Hal- 
cyonoids, of the Atraeoids, etc., etc., deserve particular 
attention, and may be studied with great advantage in 
reference to the points under consideration. For every- 
where do we observe in them, with reference to space and 
to time, the thoughtful combinations of an active mind. 
But it ought not to be overlooked, that, while some types 
represent strikingly connected series, there are others in 
which nothing of the kind seems to exist, and the diver- 
sity of which involves other considerations. 



< M ESSAY OX CLASSIFICATIOX. 

SECTION XnL 

HELATIOX BETWEEN THE SIZE OF XSIJUlLS AXD THEIR 

STSrCTUSE. 

The relation between the sLze and the stractore of ani- 
mxils has l>een very Uttle investigated, though even the most 
fm[>f:frficial Burvey of the animal kingdcHn may satisfy any 
on<f, tliat there Ls a decided relation between size and 
Ktructure among them. Not that I mean to assert that 
H17J* and structure form parallel series, or that all animals 
of ontt branch, or even those of the same class or the same 
onlcr, agree very closely with one another in reference to 
Hiyjt. lliin element of their organization is not defined 
within thoBC limits, though the Vertebrata> as a ^ole, 
arc larg^T than Articulata, MoUusks, or Radiata; though 
Mammalia are larger than Birds, Crustacea larger than 
IrjM<fctH ; though Cetacea are larger than Herbivora> these 
larger tlian (.'amivora, etc. The true limit in the organiza- 
tion of aninialn, within which size acquires a real import- 
ant'*, in thai of families, that is, groups which are essen- 
tially (liHiinguirthed by their form ; as if form and size 
wrvit correlative cOS far as the structure of animals is 
eone<*rne<l. The representatives of natural families are, 
in'le(*i|, eloHeJy similar in that respect. The greatest 
iJiireren'eH within these limits are hardly anywhere 
iiH nujeh as ten to one, and frequently not more 
iJiiin iiH two to r)ne. A few examples, selected from 
arnonj^ the, most natunil families, will show this. Omit- 
f in/^ nuinkin<l, on aecount of the objections which might 
Ix' rnaije ngaiuHt the idea that it embraces any original 
ijiverrtity. let UK eouHider th(» different families of Mon- 
keyn, of Halrt. of luHeetivores, of ( -arni vores, of Rodents, of 
I'arjiyilcnn.s. of Ruminants, etc. ; among Birds, the Vul- 



SIZE OF ANIMALS. 71 

tures, the Eagles, the Falcons, the Owls, the Swallows, 
the Finches, the Warblers, the Humming Birds, the Doves, 
the Wrens, the Ostriches, the Herons, the Plovers, the 
Gulls, the Ducks, the Pelicans ; among Reptiles, the Cro- 
codiles, the dijflferent families of Chelonians, of Lizards, of 
Snakes, the Frogs proper, the Toads, etc. ; among Fishes, 
the Sharks and Skates, the Herrings, the Codfishes, the 
Cyprinnodonts, the Chaetodonts, the Lophobranches, the 
Ostracionts, etc. ; among Insects, the Sphingoidse or the 
Tineina, the Longicoms or the Coccinellina, the Bom- 
boidse or the Brachonidae ; among Crustacea, the Can- 
croidea or the Pinnitheroidae, the LimuloidaB or the 
Cypridoidae, and the Rotifera ;^ among Worms, the Dor- 
sibranchiata or the Naioidae ; among Mollusks, the Strom- 
boidae or the Buccinoidae, the HelicinoidaB or the Lim- 
naeoidaa, the Chamacea or the Cycladoidae ; among Radiata, 
the Asterioidae and the Ophiuroidae, the Hydroids and the 
Discophorae, the AstraeoidaB and the ActinioidaB. 

Having thus recalled some facts which go to show what 
are the limits within which size and structure are more 
directly connected,^ it is natural to infer, that, since size 
is such an important character of species, and extends 
distinctly its cycle of relationship to the families or even 
further, it can as little be supposed to be determined by 

^ See Daka*8 Crustacea, p. 1409 the least bearing upon the question 

and 1411. of origin, or even the maintenance of 

' These remarks about the average any species, but only upon the con- 
size of animals in relation to their dition of individuals, respecting which 
structure, cannot fail to meet with more will be found in Sect. 16. More- 
some objections, as it is well known over, it should not be overlooked that 
that, under certain circumstances, there are limits to these variations, 
man may modify the normal size of and that, though animals and plants 
a variety of plants and of domesti- may be placed under influences con- 
cated animals, and that, even in their ducive to a more or less voluminous 
natural state, occasional instances of growth, yet it is chiefly under the 
extraordinary sizes occur. But this agency of man that such changes 
neither modifies the characteristic reach their extremes. (See also Sect. 
average, nor is it a case which has 15.) 



72 ESSAY ON CLASSIFICATION. 

physical agents as the structure itself, with which it is so 
closely connected, both bearing similar relations to these 
agents. 

Life is regulated by a quantitative element in the 
structure of all organized beings, which is as fixed and 
as precisely determined as every other feature depending 
more upon the quality of the organs or their parts. This 
shows the more distinctly the presence of a specific, im- 
material principle in every kind of animals and plants. 
All begin their existence in the condition of ovules of a 
microscopic size, which exhibit a wonderful similarity of 
structure. And yet these primitive ovules, so identical 
at first in their physical constitution, never produce any 
thing different fi'om the parents ; and all reach respec- 
tively, through a succession of unvarying changes, the 
same final result, the reproduction of a new being iden- 
tical with the parents. How does it happen then, that> if 
physical agents have such a powerful influence in shaping 
the character of organized beings, we see no trace of it in 
the innumerable instances in which these ovules are dis- 
charged into the elements in which they undergo their fur- 
ther development, at a period when the germ they con- 
tain has not yet assumed any of those more determined 
characteristics which distinguish the fuU-grown animal 
or the perfect plant? Do physicists know any law of 
the material world which presents such analogy to these 
phenomena, that it could be considered as accounting for 
them ? 

In this connection, it should be further remembered 
that these cycles of size characteristic of different fami- 
lies are entirely different for animals of different types, 
though living together under identical circumstances. 



H.^ 



SIZE AND THE ELEMENTS. 73 



SECTION XIV. 

HELATIONS BETWEEN THE SIZE OF ANIMALS AND THE 
MEDIUMS IN WHICH THET LITE. 

It has just been remaxked, that animals of different 
types, even when living together, are framed in structures 
of different size. Yet, life is so closely combined with 
the elements of nature, that each type shows decided re- 
lations, within its own limits, to these elements, as far as 
size is concerned.^ The aquatic Mammalia, as a whole, 
are larger than the terrestrial ones ; so are the aquatic 
Birds and the aquatic Reptiles. In families which are 
essentially terrestrial, the species which take to the water 
are generally larger than those which remain permanently 
terrestrial, as, for instance, the Polar Bear, the Beaver, the 
Coypu, and the Capybara. Among the different families 
of aquatic Birds, those of their representatives which are 
more terrestrial in their habits are generally smaller than 
those which live more permanently in the water. The same 
relation is observed in the different families of Insects 
which number aquatic and terrestrial species. It is 
further remarkable, that, among aquatic animals, the 
fresh-water types are inferior in size to the marine ones ; 
the marine Turtles are all larger than the largest inhabi- 
tants of our rivers and ponds ; the more aquatic Trionyx 
larger than the Emyds ; and, among these, the more aquatic 
Chelydra larger than the true Emys, and these generally 
larger than the more terrestrial Clemmys or the Cistudo. 

' Geoffrot St. Hilaibe (Ibid.), etc., quoted above, p. 46; and Be- 

Becherches zoologiques et physiolo- fold (A.ton), Untersuchungen iiber 

giques but les variations de la taille die Vertheilung von Wasser, organ- 

chez les Animaux et dans les races ischer Materie und anorganischen 

humaines ; Paris, 1831, 4to. — See also Verbindungen imThierreiche,Zeit8ch. 

my paper upon the Natural Relations f. wiss. Zool., 1857, vol. 8, p. 487. 
between Animals and the Elements, 



74 ESSAY ON CLASSIFICATION. 

The class of Fishes has its largest representatives in the 
sea ; fresh water fishes are on the whole dwarfs in com- 
paiison to their marine relatives, and the largest of them, 
our Sturgeons and Salmons, go to the sea. The same 
relations obtain among Crustacea ; and to be satisfied of 
the fact, we need only compare our fi'eshwater Crawfishes 
with the Lobsters, our Apus with Limulus, etc. Among 
Worms, the Earthworms and Leeches furnish a still wider 
range of comparison, when contrasted with the marine 
types. Among Gasteropods and Acephala> this obtains 
to the same extent ; the most gigantic Ampullariae and 
Anodontae are small in comparison to certain species of 
Fusus, Voluta, Tritonium, Cassis, Strombus, or to the Tri- 
dacna. Among Eadiata even, which are all marine witii 
the exception of the single genus Hydra, this rule holds 
good, as the fresh water Hydroids are among the smallest 
Acalephs known. 

This coincidence, upon such an extensive scale, seems 
to be most favourable to the view that animals are mo- 
dified by the immediate influence of the elements ; yet I 
consider it as affording one of the most striking proofs 
that there is no causal connexion between them. Were 
it otherwise, the terrestrial and the aquatic representatives 
of the same family could not be so simUar as they are in 
all their essential chamctcristics, which actually stand in 
no relation whatsoever to these elements. That which con- 
stitutes the Bear in the Polar Bear is not its adaptation to 
an aquatic mode of existence. That which makes the 
Whales Mammalia bears no relation to the sea. That which 
constitutes Earthworms, Leeches, and Eunice members of 
one class has no more connexion with their habitat, than 
the pocuUarities of structure wliich unite Man, Monkeys, 
Bats, Lions, Seals, Beavers, Mice, and Whales into one class. 



IMMUTABILITY OF SPECIES. 73 

Moreover, aniniala of diflferent types, living in the same 
element, have no sort of similarity as to size. The aquatic 
Insects, the aquatic MoUusks, fall in with the average size 
of their class, as well as the aquatic Reptiles and the 
aquatic Birds, or the aquatic Mammalia ; but there is no 
common average for either terrestrial or aquatic animals 
of different classes taken together. And in this lies the 
evidence that organized beings are independent of the 
mediums in which they live, as far as their origin is con- 
cerned, though it is plain that, when created, they were 
made to suit the element in which they were placed. 

To me these facts show that the phenomena of life are 
manifested in the physical world, and not through or by 
it ; that organized beings are made to conquer and assi- 
milate to themselves the materials of the inorganic world ; 
that they maintain their original characteristics, notwith- 
standing the imceasing action of physical agents upon 
them. And I confess I cannot comprehend how beings so 
entirely independent of these influences could be produced 
by them. 

SECTION XV. 

PERMANENCY OF SPECIFIC PECULIARITIES IN ALL ORGANIZED 

BEINGS. 

It was a great step in the progress of science when it 
was ascertained that species have fixed characters, and 
that they do not change in the course of time. But this 
fact, for which we are indebted to Cuvier,^ has acquired a 
still greater importance since it has also been established, 
that even the most extraordinary changes in the mode of 
existence, and in the conditions under which animals 

1 CuYiSR (G.), Recherches sur Ics Paris, 1821, 5 vols., 4to., fig. vol. i, 
ossements fossiles, etc., Nouv. ^it.; sur ribis, p. cxli. 



76 ESSAY ON CLASSIFICATION. 

are placed, have no more influence upon their essential 
characters than the lapse of time. 

The facts bearing upon these two subjects are too well 
known to require special illustration. I will, therefore, 
allude only to a few points, to avoid even the possibility 
of a misapprehension of my statements. That animals of 
different geological periods differ specially, en masse^ from 
those of preceding or following formations, is a fact satis- 
factorily ascertained. Between two successive geological 
periods, then, changes have taken place among animalfl 
and plants. But none of those primordial forms of life 
which naturalists call species are known to have changed 
during any of these periods. It cannot be denied, that 
the species of different successive periods are supposed 
by some naturalists to derive their distinguishing features 
from changes which have taken place in those of pre- 
ceding ages ; but this is a mere supposition, supported 
neither by physiological nor by geological evidence ; and 
the assumption, that animals and plants change in a 
similar manner during one and the same period, is equally 
gratuitous. On the contrary, it is known, by the evidence 
furnished by the Egyjitian monuments, and by the most 
careful comparison between animals found in the tombs 
of Egypt with living specimens of the same species ob- 
tained in the same country, that there is not the shadow 
of a difference between them for a period of about five 
thousand years. These comparisons, first instituted by 
Cuvier, have proved, that, as far as it has been possible to 
carry back the investigation, it does not afford the begin- 
ning of an evidence that species change in the course of 
time, if the comparisons be limited to the Siime great cos- 
mic ej)och. Geology only shows that at different periods^ 

^ I trust no reader will be so igno- to infer from the use of the woid 
rant of the facts here aUuded to as *'period**for different eras and epochs 



IMMUTABILITY OF SPECIES. 77 

there have existed different species ; but no transition 

from those of a preceding into those of the following 

of great length,— «ach of which is under the action of physical agents, 
characterized by different animals, — according to their law, or is it pro- 
that the differences these animals duced by the intervention of an agen- 
exhibit is in itself eyidence of a cy not at work in that way before or 
change in the species. The question afterwards ? A comparison may ex- 
is, whether any changes take place plain my view more fully. Let a 
during one or any of these periods, lover of the fine arts visit a museum 
It is almost incredible how loosely arranged systematically, and in which 
some people will argue upon this the works of the different schools are 
point ^m a want of knowledge of placed in chronological order. As he 
the facts, even though they seem to passes from one room to another, he 
reason logically. A distinguished beholds changes as great as those 
physicist has recently taken up this which the palaeontologist observes in 
subjectof the immutability of species, passing from one system of rocks to 
and called in question the logic of another. But, because these works 
those who uphold it. I will put his bear a closer resemblance as they 
argument into as few words as pos- belong to one or the other school 
sible, and show, I hope, that it does or to periods following one another 
not touch the case. '' Changes are closely, would the critic be in any 
observed from one geological period way justified in assuming that the 
to another ; species which do not ex- earlier works have changed into 
ist at an earlier period are observed those of a later period, or in denying 
at a later period, while the former that they are the works of artists 
have disappeared ; and, though each living and active at the time of 
species may have possessed its pecu- their production ? The question about 
liarities unchanged for a lapse of the immutability of species is iden- 
time, the fact that, when long periods tical with this supposed case. It is 
are considered, all those of an earlier not because species have lasted for 
period are replaced by new ones at a a longer or shorter time in past ages 
later period, proves that species that naturalists consider them as im- 
change in the end, provided a suffici- mutable, but because, in the whole 
entlylong period of time is granted." series of geological ages, taking the 
I have nothing to object to the state- entire lapse of time which has passed 
ment of facts, as far as it goes, but I since the first introduction of ani- 
maintain that the conclusion is not mals or plants upon earth, not the 
logical. It is true that species are U- slightest evidence has yet been pro- 
mited to particular geological epochs ; duced that species are actually trans- 
and it is equally true, that, in all formed one into the other. We only 
geological formations, those of sue- know that they are different at dif- 
cessive periods are different one from ferent periods, as are works of art 
the other. But because they so differ, of different periods and of different 
does it follow that they have them- schools ; but, as long as we have no 
selves changed, and not been ex- other data to reason upon than those 
changed for, or replaced by, others ? which Geology has furnished to this 
The length of time taken for the day, it is as unphilosophical and illo- 
operation has nothing to do with the gical, because such differences exist, 
argument. Qran ting myriads of years to assume that species do change, 
for each period, no matter how many and have changed, — that is, are trans- 
or how few, the question remains formed, or have been transformed, — 
simply this : When the change takes as it would be to maintain that works 
place,doefl it take place spontaneously, of art change in the course of time. 



78 



ESSAY ON CLASSIFICATION. 



epocli has ever been noticed anywhere ; and the questdoii 
alluded to here is to be distinguished firom that of the 
origin of the differences in the bulk of species belonging 
to two different geological eras. The question we are now 
examining involves only the fixity or mutability of spe- 
cies during one epoch, one era, one period, in the history 
of our globe. And nothing furnishes the slightest argu- 
ment in favour of their mutability. On the contrary, 
every modern investigation^ has gone only to confirm the 
results first obtained by Cuvier, and his views, that species 
are fixed. 

It is something to be able to show by monumental evi- 
dence and by direct comparison, that animals and plants 
have undergone no change for a period of about five thou- 
sand years.^ This result has had the greatest influence 
upon the progress of science, especially with reference to 
the consequences to be drawn from the occurrence in the 
series of geological formations of organized beings as 
highly diversified in each epoch as those of the present 
day ;^ and it has laid the foundation for the conviction, 
now univei-siil among well informed naturalists, that this 
globe has been in existence for innumerable ages, and that 
the length of time elapsed since it first became inhabited 
cannot be counted in years. Even the length of the period 



We do not know how organized 
beings have originated, it is true ; 
and no naturalist can be prepared to 
account for their appearance in the 
beginning, or for their difference in 
different periods; but enough is known 
to repudiate the assumption of their 
transmutation, as it docs not explain 
the facts, and shuts out further at- 
tempts at proper investigations. See 
Badex Powell's Essays, quoted 
above, p. 412 et seq., and Essay 3rd, 
generally. 



^ KusTU, Recherches sur les 
plantes trouvees dans les tombcftux 
6gvptiens ; Ann. des scien. nat., toL 
vii'i, 1820, p. 411. 

^ It is not for me to discuss the 
degree of reliability of the Egyptian 
chronology ; but, as far as it goes, it 
shows that, from the oldest periods 
ascertained, animals have been what 
they are now. 

* See my paper upon The Primi- 
tive Diversity, etc., quoted aboTe, 
p. 35, 



IMMUTABILITY OF SPECIES. 79 

to which we belong is still a problem, notwithstanding the 
precision with which certain systems of chronology would 
fix the creation of man.^ There are, however, many cir- 
cumstances which show that the animals now living have 
been for a much longer period inhabitants of our globe 
than is generally supposed. It has been possible to trace 
the formation and growth of our coral reefs, especially in 
Florida,^ with sufficient precision to ascertain that it must 
take about eight thousand years for one of those coral 
walls to rise fi-om its foundation to the level of the sur- 
face of the ocean. There are, around the southernmost 
extremity of Florida alone, four such reefs, concentric with 
one another, which can be shown to have grown up one 
after the other. This gives, for the beginning of the first 
of these reefs, an age of over thirty thousand years (nay, 
probably, over one hundred thousand years) ; and yet the 
the corals by which they were all built up are the same 
identical species in all of them. These facts, then, fur- 
nish evidence as direct as we can obtain in any branch 
of physical inquiry, that some, at least, of the species of 
animab now existing, have been in existence over thirty 
thousand years,^ and have not undergone the slightest 
change during the whole of that period.* And yet these 

1 NoTT and Gliddok, Types of at one hundred thousand years; so 

Mankind, p. 653. slow are the operations of nature. 

* See my paper upon the Reefs of ^ Those who feel inclined to ascribe 

Florida, soon to be published in the the differences which exist between 

Reports of the United States Coast species of different geological periods 

Surrey, extracts of which are already to the modifying influence of physi- 

prin ted in the Report for 1851, p. 145. cal agents, and who look to the 

A renewed examination of the reefs changes now going on among the Ut- 

of Florida has satisfied me that this ing for the support of such an opi- 

estimate falls short of the reality by nion, and not being satisfied that the 

a great deal. The rate of growth of facts just mentioned are sufficient 

the corals, ascertained by direct ob> to prove the immutability of spe- 

serration, is not half so rapid as I cies, still belieye that a longer 

had been led to assume at first. period of time would yet do what 

' I am now satisfied that the age of thirty thousand years have not done, 

thisreef is not OYerstated, if estimated I beg leave to refer, for further con- 



80 ESSAY ON CLASSIFICATION. 

four concentric reefs are only the most distinct of that 
region ; others, thus far less extensively investigated, lie 
to the northward : indeed, the whole peninsula of Florida 
consists altogether of coral reefs annexed to one another 
in the course of time, and containing only fragments of 
corals and shells, etc., identical with those now living 
upon that coast. Now, if a width of five miles is a fiedr 
average for one coral reef, growing under the circum- 
stances under which the concentric reefs of Florida are 
seen now to follow one another, and this regular succes- 
sion extends only as far north as Lake Ogeechobee, 
for two degrees of latitude, this would give about two 
hundred thousand years for the period of time which was 
necessary for that part of the peninsula of Florida which 
lies south of Lake Ogeechobee to rise to its present 
southern extent above the level of the sea, and during 
which no changes have taken place in the character of 
the animals of the Gulf of Mexico.^ 

It is very prejudicial to the best interests of science to 
confound questions that are entirely different, merely for 
the sake of supporting a theory ; and yet this is constantly 
done, whenever the question of the fixity of species is 
alluded to. A few more words upon this point, therefore, 
wiU not be out of place here. 

I will not enter into a discussion upon the question, 
whether any species are found identically the same in two 
successive formations, as I have already examined it at 
full length elsewhere,^ and it may be settled finally, one 

sideration, to the charming song of * Aoassiz (L.), Coquilles tertiairet 
Chamisso, entitled Tragische Qes- r6put6es identiques avec lea esp^^oei 
chichte, and beginning as follows : vivantes ; Nouv. M6m. de la Soc 



<**8 war£incrdom*szu Herzenffing.** Helv. des so. nat., Keuch&tel, 1845, 

tiy - ; " ' - - - 

ible critiqu 

that time, at least, has elapsed since KeucMtel, 1831-45, 4to., &g, — Aoas- 



1 According to facts recently ob- Yol.7,4to., fig. — Aoassiz (L.), Ktudei 
■ - ill ----- 



served, and alluded to above, double critiques sur les Mollusques foBsilei; 
that time, at least, has elapsed since KeucMtel, 1831-45, 4to., &g, — Aoas- 
their first appearance in these waters, biz (L.), Monographies d*EchiiiQ- 



IMMUTABILITY OF SPECIES. 81 

way or the other, without affecting the proposition now 
under consideration ; for it is plain, that, if such identity 
could be proved, it would only show more satisfactorily 
how tenacious species are in their character, to continue 
to live through aU the physical changes which have taken 
place between two successive geological periods. Again, 
such identity, once proved, would leave it still doubtful, 
whether their representatives in two successive epochs 
are descendants one of the other, as we have already 
strong evidence in favour of the separate origin of the 
representatives of the same species in separate geo- 
graphical areas. ^ The case of closely allied but different 
species occurring in successive periods, yet limited re- 
spectively to their epochs, affords, in the course of time, a 
parallel to the case of closely allied, so-caUed, representa- 
tive species occupying different areas in space, which no 
sound naturalist would now suppose to be derived one 
from the other. There is no more reason to suppose 
species equally allied, following one another in time, to 
be derived one from the other; and aU that has been 
said in preceding paragraphs respecting the differences 
observed between species occurring in different geo- 
graphical areas applies with the same force to species 
succeeding each other in the course of time. 

When domesticated animals and cultivated plants are 
mentioned as furnishing evidence of the mutability of 
species, the circumstance is constantly overlooked, or 
passed over in silence, that the first point to be es- 
tablished respecting them, in order to justify any in- 
ference from them against the fixity of species, would be 

dermes yiTans et fossiles; Neuch&tel, 4to., atlas, fol. 
1838-42, 4 noB., 4to., fig. — Aoassiz ^ See Sect. 10, where the case of 

(L.), Recherches but les Poissons fos- representative species is consider- 

Biles; Neucb&tel, 1833-44, 5 vols., ed. 





82 ESSAY ON CLASSIFICATION. 

to show that each of them has originated firom one com- 
mon stock, whic h, far from being the case, is flatly con- 
tradicted by the positive knowledge we have that the 
varieties of several of them at least are owing to the 
entire amalgamation of different species.^ The Egyptian 
monmnents further show that many of these so-called 
varieties, which are supposed to be the product of time, 
are as old as any other animals which have been known 
to man. At all events, we have no tradition, no monu- 
mental evidence of the existence of any wild animal older 
than those which represent domesticated animals, already 
as different among themselves as they are now,^ It is^ 
therefore, quite possible that the different races of domes- 
ticated animals were originally distinct species, more or 
le88 mixed now, as the different races of men are. More- 
ov(»r, neither domesticated animals, nor cultivated plants^ 
nor the races of men, are the proper subjects for an in- 
vestigation res2)ecting the fixity or mutability of species, 
.'IS all involve already the question at issue in the premises 
which are assumed in introducincr them as evidence in the 
case. With reference to the different breeds of our do- 
mesticated animals, which are known to be produced by 
the management of man, as well as certain varieties of our 
cultivated i)lants, they must be weU distinguished from 
permanent races, which, for aught we know, may be pri- 
mordiiJ ; for breeds are the result of the fosteiing care of 
man : they are the jjroduct of the limited influence and 
control the human mind has over organized beings, and 
not the free jiroduct of mere i)hysical agents. They show, 
therefore, that even the least important changes which 
may take iilaccj during one and the same cosmic period, 
among animals and jJants, are controlled by an inteUec- 

' Our fowlH, for instance. ^ Nott and Oliddon, Types of Mankind, p.38G. 



IMMUTABILITY OP SPECIES. 83 

tual power, and do not result fipom the immediate action 
of physical causes. 

So far, then, from disclosing the effects of physical 
agents, whatever changes are known to take place in the * 
course of time among organized beings appear ^ the 
result of an intellectual power, and go therefore to sub- 
stantiate the view, that all the differences observed among 
finite beings are ordained by the action of the Supreme 
Intellect^ and not determined by physical causes. This 
position is still more strengthened, when we consider that 
the differences which exist between different races of do- 
mesticated animals and the varieties of our cultivated 
plants, as well as among the races of men, are permanent 
xmder the most diversified climatic influence ; a fact 
which is daily proved more conclusively by the extensive 
migrations of the civilized nations, and which stands in 
direct contradiction to the supposition that such or similar 
influences could have produced them. 

When considering the subject of domestication, in par- 
ticular, it ought further to be remembered, that every 
race of man has its own peculiar kinds of domesticated 
animals and of cultivated plants, and that these exhibit 
much fewer varieties among themselves in the case of 
those races which have had little or no intercourse with 
other races, than in the case of those nations which have 
been formed by the mixture of several tribes. 

It is often stated, that the ancient philosophers have 
solved satisfactorily all the great questions interesting to 
man ; and that modem investigations, though they have 
grasped with new vigour, and illuminated with new light, 
all the phenomena of the material world, have added little 
or nothing in the field of intellectual progress. Is this 
true 1 There is no question so deeply interesting to man 

G 2 



84 ESSAY OX CLASSIFICATIOX. 

as that of his own origin, and the origin of aU things. 
And yet, antiquity had no knowledge concerning it: 
things were formeriy believed, either to be firom eternity, 
or to have been created at one time. Modem science, 
however, can show in the most satis&ctoiy manner that 
all finite beings have made their appearance successively 
and at long intervals, and that each kind of organized 
iK^ings has existed for a definite period of time in past 
jiges, and that those now living are of comparatively 
Titi'jint oricfin. At the same time, the order of their sue- 
r:('SHion, and their inmiutability during such cosmic periods, 
Hhr>vv no casual connexion with physical agents and the 
known sphere of action of these agents in nature, but 
argne in favour of repeated interventions on the part of 
ihii ( 'Hfjitor. It seems really surprising, that, while such 
an int<;rvention is admitted by all, except the strict ma- 
tc^rialistH, for the establishment of the laws regulating the 
inorganic world, it is yet denied by so many physicists 
with nifcrence U> the introduction of organized beings at 
rlifl'rrcnt succcsHive periods. Does this not show the 
inipr rfect aequaintuncc of these investigators with the 
condilionH under which life is manifested, and with the 
eHHcntinJ difference between the phenomena of the organic 
and thorn; of the i)hy8ical world, rather than furnish any 
evidenet; that i\ui organic world is the product of physical 
eiumeH If 

SECTION XVI. 

Iir.I.ATrONH IIETWEKN ANIMALS AND PLANTS AND THE 

8URB0UNDINO WORLD. 

Iwery anininl and plant stands in certain definite rela- 
tions to th(i surrounding world ; some, however, like the 



HABITS OF ANIMALS. 



85 



domestic animals and the cultivated plants, are capable of 
adapting themselves to various conditions more readily 
than others ; but even this pliability is a characteristic 
feature. These relations are highly important in a syste- 
matic point of view, and deserve the most careful attention 
on the part of naturalists. Yet, the direction which zoolo- 
gical studies have taken since Comparative Anatomy and 
Embryology began to absorb almost entirely the attention 
of naturalists has been very unfavourable to the investi- 
gation of the habits of animals, in which their relations to 
one another and to the conditions under which they live 
are more especially exhibited. We have to go back to the 
author of 'the pLeding century, for th! met inter- 
esting accounts of the habits of animals, as among mo- 
dem writers there are few who have devoted their chief 
attention to this subject.^ So little, indeed, is its import- 
ance now appreciated, that the students of this branch of 
natural history are hardly acknowledged as peers by their 
fellow investigators, the anatomists and physiologists, or 
the systematic zoologists. And yet, without a thorough 
knowledge of the habits of animals, it will never be pos- 
sible to ascertain with any degree of precision the true 
limits of all those species which descriptive zoologists 
have of late admitted with so much confidence into their 



> Reaumur (R. Akt. db), Mtooires 
pour servir h, rhistoire des Insectes ; 
Paris, 1834-42, 6 vols. 4to. fig.— R5- 
6EL (A. J.), Insectenbelttstigungen ; 
Nurnberg, 1746-61, 4 vols. 4to., fig. — 
BuFFON (0. L. LbCiiEbo i>E),Histoire 
naturelle g6n6rale et particuli^re ; 
Paris, 1749, 44 toIb. 4to., fig. 

' AuDUBOK (J. J.), Ornithological 
Biography, or an Account of the Ha- 
bits of the Birds of the United States 
of America; Edinburgh, 1831-49,5 
▼ols. Sto. — KiBBT (W.) and Spence 
( W.), An Introduction to Entomology ; 



London, 1818-26, 4 vols. 8vo., ^g. — 
Lenz (H. 0.), Qemeinniitzige Natur- 
geschichte; Qotha, 1835, 4 vols. 8vo. 
— Ratzenbubo (J. Th. Ch.), Die 
Forst-Insekten ; Berlin, 1837-44, 3 
vol8.4to. fig., and supplement. — U ab- 
BIS (T. W.), Report on the Insects 
injurious to Vegetation ; Cambridge, 
1841, 1 vol.Svo.; 2nd edit., A Trea- 
tise on some of the Insects of New 
England which are injurious to Vege- 
tetion ; Boston, 1852, 8vo. The most 
important work on American In« 
sects. 



86 ESSAY ON CLASSIFICATION. 

works. And after all, what does it matter to science, 
that thousands of species, more or less, should be de- 
scribed and entered in our systems, if we know nothing 
about them ? A very common defect of the works rela- 
ting to the habits of aniTnalfl has no doubt contributed to 
detract from their value, and to turn the attention m 
other directions : their purely anecdotic character, or the 
circumstance that they are too frequentiy made the occa- 
sion for narrating personal adventures. Nevertheless, the 
importance of thij kind of investigation can hardly be 
overrated ; and it would be highly desirable that natu- 
ralists should turn their attention that way again, now 
that Comparative Anatomy and Physiology, as well as 
Embryology, suggest so many new topics of inquiry, 
and the progress of Physical Greography has laid such a 
broad foundation for researches of this kind. Then we 
may learn with more precision, how far the species de- 
scribed from isolated specimens are founded in nature, or 
how far they are only a particular stage of growth of 
other species : then we shall know, what is yet too littie 
noticed, how extensive the range of variation is among 
animals observed in their wild state, or rather, how much 
individucility there is in each and all living beings. So 
marked, indeed, is this individuality in many families^ — 
and that of the Turties affords a striking example of this 
kind, — that correct descriptions of species can hardly be 
drawn from isolated specimens, as is constantly attempted 
to be done. I have seen hundreds of specimens of some 
of our Chelonians, among which there were not two iden- 
tical. And truly, the limits of this variability constitute 
one of the most important characters of many species ; 
and, without 2>recise information upon this point for every 
genus, it will never be possible to have a solid basis for 



HABITS OP ANIMALS. 



87 



the distinction of species. Some of the most perplexing 
questions in Zoology and Palaeontology might long ago 
have been settled, had we had more precise information 
upon this point, and were it better known, how unequal 
in this respect different groups of the animal kingdom are, 
when compared with one another. While the individuals 
of some species seem all different, and might be described 
as different species, if seen isolated, or obtained from dif- 
ferent regions, those of other species appear as if all cast 
in one and the same mould. It must be, therefore, at once 
obvious, how different the results of the comparison of 
one fauna with another may be, if the species of one have 
been studied accurately, for a long period, by resident 
naturalists, and the other is known only from specimens 
collected by chance travellers ; or, if the fossil representa- 
tives of one period are compared with living animals, 
without both faunas having first been revised according 
to the same standard.^ 

Another deficiency, in most works relating to the habits 
of animals, consists in the absence of general views and of 
comparisons. We do not learn from them, how far ani- 
mals related by their structure are similar in their habits, 
and how far these habits are the expression of their struc- 
ture. Every species is described as if it stood alone in 
the world ; and its peculiarities are mostly exaggerated, 
as if to contrast more forcibly with all others. Yet, how 



1 In this respect I would remark 
that most of the cases in which spe- 
cific identity has been affirmed be- 
tween liTing and fossil species, or 
between the fossils of different geolo- 
gical periods, beloDg to families which 
present either great similarity or ex- 
traordinary variability, and in which 
the limits of species are therefore 
very difficult to establish. Such cases 



should be altogether rejected in the 
investigation of general questions in- 
volving fundamental principles, as 
untrustworthy observations always 
are in other departments of science. 
Compare further my paper upon The 
Primitive Diversity and number of 
animals, quoted above, page 36, 
in which this point is specially consi- 
dered. 



88 ESSAY ON CLASSIFICATION. 

interesting would be a comparative study of the mode of 
life of closely allied species ! how instructive a picture 
might be drawn of the resemblance there is in this re- 
spect between species of the same genus and of the same 
family ! The more I learn upon this subject^ the more am 
I struck with the similarity in the very movements, the 
general habits, and even in the intonation of the voices of 
animals belonging to the same family ; that is to say, be- 
tween animals agreeing in the main in form, size, struc- 
ture, and mode of development. A minute study of these 
habits, of these movements, and of the voice of animals, 
cannot fail, therefore, to throw additional light upon their 
natural affinities. 

While I thus acknowledge the great importance of such 
investigations with reference to the systematic arrange- 
ment of animals, I cannot help regretting deeply that 
they are not more highly valued with reference to the in- 
formation they might secure respecting the a.nima1fl them- 
selves, independently of any system. How much is there 
not left to study with respect to every species after it is 
named and classified ! No one can read Nauman's Natural 
History of German Birds without feeling that natural 
history would be much further advanced, if the habits of 
all other animals had been as accurately investigated and 
as minutely recorded ; and yet that work contains hardly 
anything of importance with reference to the systematic 
arrangement of birds. We scarcely possess the most ele- 
mcntaiy information necessary to discuss upon a scien- 
tific basis the question of the instincts, and in general the 
faculties of animals, and to compare them together and 
with those of mau,^ not only because so few animals have 

1 ScHEiTLiN (P.), Vcrsuch cincr Stuttgart uiid Tubingen, 1840, 2 vols, 
vollst&udigen Thicrscclonkundo ; 8?o. — CuviEB(FaJD.)llesum6aimljt- 



HABITS OF ANIMALS. 89 

been thoroughly investigated, but because so much fewer 
still have been watched during their earlier periods of life, 
when their faculties are first developing; and yet how 
attractive and instructive this growing age is in every 
living being ! Who, for instance, could believe for a mo- 
ment longer that the habits of animals are in any degree 
determined by the circumstances under which they live, 
after having seen a little turtle of the genus Chelydra, still 
enclosed in its egg-shell, which it hardly fills half-way, 
with a yolk bag as large as itself hanging firom its lower 
surface and enveloped in its amnios and in its allantois, 
with the eyes shut^ snapping as fiercely as if it could bite 
without killing itself?^ Who can watch the Sunfish (Po- 
metis vulgaris) hovering over its eggs and protecting 
them for weeks, or the Catfish {Pimdodus CaJtus) moving 
about with its young, like a hen with her brood, without 
remaining aatisEed that the feeling which prompts them 
in these acts is of the same kind as that which attaches 
the Cow to her suckling, or the child to its mother ? Is 
there an investigator, who having once recognized such a 
similarity between certain faculties of Man and those of 
the higher animals, can feel prepared, in the present stage 
of our knowledge, to trace the limit where this commu- 
nity of nature ceases ? And yet, to ascertain the character 
of all these faculties there is but one road ; the study of 
the habits of animals, and a comparison between them and 
the earlier stages of the development of Man. I confess 
I could not say in what the mental faculties of a child 
differ fix)m those of a young Chimpanzee. 

Now that we have physical maps of almost every part 

i<jae des obseirations sur rinstinct et ^ See Contributions to the Natural 

rintelligence des animaux, par R. History of the United States., Part 

Flourens; Ann. Sc. Nat., 2de s^r., Ill, which is devoted to the Embry- 

Tol. 12. olpgj of the Turtles. 



90 ESSAY ON CLASSIFICATION. 

of the globe,^ exhibiting the average temperature of the 
whole year and of every season upon land and sea ; now 
that the average elevation of the continents above the 
sea, and that of the most characteristic parts of their sur- 
face, — their vaUeys, their plains, their table-lands, their 
mountain systems, — ^are satisfactorily known ; now that 
the distribution of moisture in the atmosphere, the limits 
of the river systems, the prevailing direction of the winds^ 
the course of the currents of the ocean, are not only in- 
vestigated but mapped down, even in school atlases ; now 
that the geological structure of nearly all parts of the 
globe has been determined with tolerable precision, — 
zoologists have the widest field and the most accurate 
basis to ascertain all the relations which exist between 
animals and the world in which they live. 

Having thus considered the physical agents with 
reference to the share which they may have had in calling 
organized beings into existence, and satisfied ourselves 
that they are not the cause of their origin, it now remains 
for us to examine more particularly these relations, as an 
established fact, as conditions in which animals and plants 
arc placed at the time of their creation, within definite 
limits of action and reaction between them ; for, though 
not produced by the influence of the physical world, or- 
ganized beings live in it, they are bom in it, they grow 
up in it, they multiply in it, they assimilate it to them- 
selves or feed upon it, they have even a modifying in- 
fluence upon it, within the same limits as the physical 
world is subservient to every manifestation of their life. 
It cannot fail, therefore, to be highly interesting and in- 
structive to trace these connexions, even without any 

1 BERGHADSjPhysikalischcr Atlas; (A. K.), Physical Atlaa of Natural 
Gotha, 1838 ct soq., foL — Jounstom, Phonomooa; Edinb., 1848, I toL foL 



HABITS OP ANIMALS. 91 

reference to the manner in which they were established ; 
and this is the proper sphere of investigation in the study 
of the habits of animals. The behaviour of each kind 
towards its fellow-beings, and with reference to the con- 
ditions of existence in which it is placed, constitutes a 
field of inquiry of the deepest interest, as extensive as it 
is complicated. When properly investigated, especially 
within the sphere which constitutes more particularly the 
essential characteristics of each species of animals and 
plants, it is likely to afford the most direct evidence of 
the unexpected independence of organized beings of 
physical influences, if I mistake not the evidence which I 
have myself been able to collect. What can be more 
characteristic of different species of animals, than their 
motions, their plays, their affections, their sexual relations, 
their care of their young, the dependence of these upon 
their parents, their instincts, etc., etc. ; and yet there is 
nothing in all this which depends in the slightest degree 
upon the nature or the influence of the physical con- 
ditions in which they live. Even their organic functions 
are independent of these conditions to a degree unsus- 
pected, though this is the sphere of their existence which 
exhibits the closest connexions with the world around. 

Functions have so long been considered as the test of 
the character of organs, that it has almost become an 
axiom in Comparative ABatomy and Physiology, that 
identical functions presuppose identical organs. Most of 
our general works upon comparative anatomy are divided 
into chapters according to this view. And yet there 
never was a more incorrect principle, leading to more 
injurious consequences, more generally adopted. That 
naturalists should not have repudiated it long ago is the 
more surprising, as every one must have felt again and 



92 ESSAY ON CLASSIFICATION. 

again how unsound it is. The organs of respiration and 
circulation of fishes afford a striking example. How long 
have not their gills been considered as the equivalent of 
the lungs of the higher Vertebrate^ merely because they 
are breathing organs ; and yet these gills are formed in a 
very different way from the lungs : they bear very dif- 
ferent relations to the vascular system ; and it is now 
known that they may exist simidtaneously with lungs, as 
in some full-grown Batrachians, and, in the earlier em- 
bryonic stages of development, in all Vertebrata. There 
can now no longer be any doubt that they are essentially 
different organs, and that their functions afford no test of 
their nature, and cannot constitute an argument in favour 
of their organic identity. The same may be said of the 
vascular system of the fishes. Cuvier^ described their 
heart as representing the right auricle and the right ven- 
tricle, because it propels the blood it contains to the gills, 
in the same maimer as the right ventricle propels the 
blood to the lungs of the warm blooded animals ; yet 
embryology has taught us that such a comparison, based 
upon the special relations of the heart of fishes, is un- 
justifiable. The air-sacs of certain spiders have also been 
considered as lungs, because they perform similar respi- 
ratoiy functions ; and yet they are only modified tracheae,^ 
which are constructed upon such a peculiar plan, and stand 
in such different relations to the peculiar kind of blood of 
the Articulata,^ that no homology can be traced between 
them and the lungs of Vertebrata, any more than between 

1 CuTiEB (G.), lUgn. Anim., 2de ' Blanchard (Em.), De la circuit- 

6clit., Tol. ii, p. 122. tion dans les lusectes. Compt. Rend., 

* Leuckabt (R.), Ueber den Bau 1847, vol. 24, p. 870. — Aoassiz (L.), 

und die Bcdeutung der sogenannten On the Circulation of the Fluids in 

Lnngcn bei den Arachniden, in Sib- Insects, Proceedings of the Ame- 

BOLD und KoLLiKEK^s Zcitschiift, f. rican Association for 1649, page 

wiss. Zool., 1840, 1, p. 246. 140. 



HABITS OF ANIMALS. 93 

these and the so-called lungs of the air breathing Mollusks, 
whose aerial respiratory cavity is only a modification of 
the peculiar kind of giUs observed in other MoUusks. 
Examples might easily be multiplied. I will, however, 
only allude further to the alimentary canal of Insects and 
Crustacea with its glandular appendages, formed in such 
a different way firom that of Vertebrata> or Mollusks, or 
Kadiata, to their legs and wings, etc., etc. I might allude 
also to what has been called the foot in Mollusks, did it 
not appear like pretending to suppose that any one still 
entertains an idea that such a name implies any similarity 
between their locomotive apparatus and that of Verte- 
brata or Articulata ; and yet the very use of such a name 
misleads the student ; and even some of the coryphees of 
our science have not fireed themselves from such and 
similar extravagant comparisons, especially with reference 
to the solid parts of the frame of the lower animals. ^ 

This identification of functions and organs was a natural 
consequence of the prevailing ideas respecting the in- 
fluence physical agents were supposed to have upon or- 
ganized beings. But as soon as it is understood how 
different the organs may be which perform the same func- 
tion in animals, organization is at once brought into such 
a position towards physical agents as to make it utterly 
impossible to maintain the idea that there is any genetic 
connexion between them. A fish, a crab, a mussel, living 
in the same waters, breathing at the same source, should 
have the same respiratory organs, if the elements in which 
these animals live had anything to do with shaping their 
organizatioiL I suppose no one can be so short-sighted 
as to assume that the same physical agents acting upon 

> CAEU8 (CO.), Von den Ur-Thei- tea; Leipzig, 1828, 1 yol. fol., p. 61- 
len det Knochen- und Schalengerus- 89. 



94 



ESSAY ON CLASSIFICATION. 



animals of different types must produpe in each peculiar 
organs, and not to perceive that such an assumption 
implies the very existence of these animals independentlj 
of the physical agents. But this mistake recurs so con- 
stantly in discussions upon this and similar topics, that^ 
trivial as it is, it requires to be rebuked.^ On the con- 
trary, when acknowledging an intellectual conception, as 
the preliminary step in the existence not only of all or- 
ganized beings, but of everything in nature, how natural 
it is to find, that, while diversity is introduced into the 
plan, the complication, and the details of structure of 
animals, their relations to the surroimding media are 
equally diversified, and consequently that the same func- 
tions may be performed by the most different apparatus ! 



SECTION XVII. 

BELATIONS OF INDIVIDUALS TO ONE AMOTHEB. 

The relations in which individuals of the same species 
of animals stand to one another are no less determined 
and fixed than the relations of species to the surrounding 
elements, which we have thus far considered. The relar 
tions which individual animals bear to one another are of 
such a character, they they ought long ago to have been 
considered as sufficient proof that no organized being 
could ever have been called into existence by other 
agency than by the direct intervention of a reflective mind. 

having spent so much labour in UTg^ 
ing my fellow labourers in a right 
direction ; but, at the same time, I 
must protest now and for ever against 
the bigotry spreading in some quar- 
ters, which would press upon science 
doctrines not immediately flowing 
from scicntiEc premises, and check 
its free progress. 



^ I hope the day is not far distant 
when zoologists and botanists will 
equally disclaim having shared in 
the physical doctrines more or less 
now prevalent, respecting the origin 
and existence of organized beings. 
Should the time come when my pre- 
sent efforts may appear like Eghting 
against windmills, I shall not regret 



RELATIONS OF INDIVIDUALS. 95 

It is in a measure conceivable that physical agents might 
produce something like the body of the lowest kinds of 
animals or plants, and that, imder identical circumstances, 
the same thing may have been produced again and again, 
by the repetition of the same process ; but that, upon 
closer analysis of the possibilities of the case, it should 
not have at once appeared how incongruous the further 
supposition is, that such agencies could delegate the power 
of reproducing what they had just called into existence 
to those very beings, with such limitations that they could 
never reproduce anything but themselves, I am at a loss 
to understand. It will no more do to suppose, that, from 
simpler structures, such a process may end in the produc- 
tion of the most perfect, as every step implies an addition 
of possibilities not even included in the original case. 
Such a delegation of power can only be an act of intelli- 
gence ; while between the production of an indefinite 
number of organized beings as the result of a physical 
law, and the reproduction of these same organized beings 
by themselves, there is no necessary connexion. The 
successive generations of any animal or plant cannot 
stand, as far as their origin is concerned, in any causal 
relation to physical agents, if these agents have not the 
power of delegating their own action to the full extent to 
which they have already been productive in the first ap- 
pearance of these beings ; for it is a physical law, that the 
resultant is equal to the forces applied. If any new being 
has ever been produced by such agencies, how could the 
successive generations enter, at the time of their birth, 
into the same relations to these agents, as their ancestors, 
if these beings had not in themselves the faculty of sus- 
taining their character, in spite of these agents ? Why, 
again, should animals and plants at once begin to decom- 



96 ESSAY ON CLASSIFICATION. 

pose under the very influence of all those agents which 
have been subservient to the maintenance of their life, as 
soon as life ceases, if life is limited or determined by 
them ? 

There exist between individuals of the same species 
relations far more complicated than those already alluded 
to, which go stiU further to disprove any possibility of 
causal dependence of organized beings upon physical 
agents. The relations upon which the maintenance of 
species is based, throughout the animal kingdom, in the 
universal antagonism of sex, and the infinite diversity of 
these connexions in different types, have reaUy nothing 
to do with external conditions of existence ; they indicate 
only relations of individuals to individuals, beyond their 
connexions with the material world in which they liva 
How, then, could these relations be the result of physical 
causes, when physical agents axe known to have a specific 
sphere of action, in no way bearing upon this sphere of 
phenomena ? 

For the most part, the relations of individuals to in- 
dividuals are imquestionably of an organic nature, and, as 
such, have to be viewed in the same light as any other 
structural feature ; but there is much also in these con- 
nexions that partakes of a psychological character, taking 
this expression in the widest sense of the word. 

When animals fight with one another, when they asso- 
ciate for a common purpose, when they warn one another 
in danger, when they come to the rescue of one another, 
when they display pain or joy, they manifest impulses of 
the same kind as are considered among the moral attri- 
butes of man. The range of their passions is even as ex- 
tensive as that of the human mind, and I am at a loss to 
perceive a difference of kind between them, however 



RELATIONS OP INDIVIDUALS. 97 

much they may differ in degree, and in the manner in 
which they are expressed. The gradations of the moral 
faculties among the higher animals and man are more- 
over so imperceptible, that, to deny to the first a certain 
sense of responsibihty and consciousness, would certainly 
be an exaggeration of the differences which distinguish 
animals and man. There exists, besides, as much indivi- 
duaUty, within their respective capabilities, among ani- 
mals, as among men, as every sportsman, every keeper of 
menageries, and every farmer or shepherd can testify, or 
any one who has had large experience with wild, tamed or 
domesticated animals.^ 

This argues strongly in favour of the existence in every 
animal of an immaterial principle similar to that which, 
by its excellence and superior endowments, places man so 
much above animals.^ Yet the principle unquestionably 

^ See J. £. RiDiNOEB^s vivrious form the transition between man and 
works illustrative of Chime Animals, quadrupeds (Aristoteles, Naturj^e* 
which have appeared under different schichte der Thiere, von Dr. F. 
titles in Augsburg, from 1729 to Strack, Frankfurt-am-Main, 1816, 
1778. — Oeottrot St. Hilairb et p. 65); but the original says no such 
CuYiSR (Fr.), Histoire naturelle des thing. In the History of Animals, 
Mammif^res ; Paris, 1820-35, 3 vols. Book 2, Chap. Y, we read only, fvta 
fol. — LxNZ (H. 0.), Qemeinniitzige W r&p ^6«l' iwofuportpl^u tV ♦^<rii' ry 
Naturgeschichte ; Qotha, 1835, 4 r§ iwefx&frtp xal roh rtrpdxoffiv. There 
vols. 8vo. — BiNQLET (W.), Animal is a wide difference between "par- 
Biography; London, 1803, 3 vols, taking of the nature of both man 
Svo. and quadrupeds," and "forming a 

' It might easily be shown that transition between man and qua- 

the exaggerated views generally en- drupeds." The whole chapter goes on 

tertainea of the difference existing enumerating the structural simila- 

between man and monkeys are trace- rity of the three monkeys above 

able to the ignorance of the ancients, named with man ; but the idea of a 

and especiaUy the Greeks (to whom close affinity is not even expressed, 

we owe chieny our intellectual cul- and still less that of a transition be- 

ture) of the existence of the Orang- tween man and quadrupeds. The 

Outang and the Chimpanzee. The writer, on the contrary, dwells very 

animals most closely allied to man, fully upon the marked differences 

known to them, were the Red Mon- they exhibit, and knows, as well as 

key, K^/9of, the Baboon, KuroK^^oAos, any modern anatomist has ever 

and the Barbary Ape, wieriKof. A known, that monkeys have four hands. 

modem translation of Aristotle, it is ^x'* '^ f^^^ fipaxCowas, &(rn*p &y$p»wos . . . 

trae, makes him say that monkeys iiCovs 8i rohs wdias- thX y^ otov x<^' 

H 



98 ESSAY ON CLASSIFICATION. 

exists, and whether it be called soul, reason, or instinct, it 

presents, in the whole range of organized beings, a series 

fitydxat. Kal ol ZdicrvKoi Hffirtp ol r&v from the other neTOF affords a raffi- 
Xf ip«»', A M^7af naucp6raros ' «tol t6 ndret cient ground for remoYing any of 
TOW iro9ht x«pi ^MiMor, irxj^v M rh fifiicos them into another category. A dote 
rh rrit x««f>^« ^'^ ^o ttrxara ruvop luxBd. study of the dog might satisfy every 
wp eipop, TovTo 8i ir* (Upov (ncAvp^ff- one of the similarity of his impulses 
pow,icaKSisKcui^v9p&tfufio6ft,€yovwr4ptriiv. with those of man; and these im- 
It is strange that these clear and pulses are regulated in a manner 
precise distinctions should have heen which discloses psychical faculties in 
so entirely forgotten in the days of every respect of the same kind as 
Linnaeus that the great reformer in those of man : moreover he expresses 
Natural History had to confess, in by his voice his emotions and his 
the year 1746, that he knew no cha- feelings with a precision which maj 
racter by which to distinguish man be as intelligible to man as the arti- 
from the monkeys. Fauna Suecica culated speech of his fellow men. 
(Prefat., p. 2), — "Nullum characte- His memory is so retentive that it 
rem adhuc eruere potui, unde homo frequently baffles that of man. And 
a simia internoscatur." But, it is though all these fiuniltiee do not 
not upon structural similarity or dif- make a philosopher of him, they cer- 
ference alone that the relations be- tainly place him, in that respect, 
twcen man and animals have to be upon a level with a considerable pro- 
considered. The psychological his- portion of poor humanity. The in- 
tory of animals shows that, as man telligibility of the voice of animals 
is related to animals by the plan of to one another, and all their actions 
his structure, so are these related to connected with such calls, are also a 
him by the character of those very strong argument of their perceptive 
faculties, which are so transcendent power, and of their ability to act 
in man as to point at first to the spontaneously and with logical se- 
ncccssity of disclaiming for him com- quence in accordance with these per- 
pletely any relationship with the ceptions. There is a vast field open 
animal kingdom. Yet the natural for investigation in the relations be- 
history of animals is by no means tween the voice and the actions of 
completed after the somatic side of animals, and a still more interesting 
their nature has been thoroughly subject of inquiry in the relationship 
investigated; for they too have a between the cycle of intonations 
psychological individuality, which, which different species of animals of 
though less fully studied, is never- the same family are capable of utter- 
thelcss the connecting link between ing, which, as far as I have as yet 
them and man. I cannot, therefore, been able to trace them, stand to one 
agree with those authors who would another in the same relations as the 
disconnect mankind from the animal different, so-called, families of Ian- 
kingdom, and establish a distinct guages. — Schleoel (F&.), Ueber die 
kingdom for man alone, as Ehren- Sprache und Weisheit der Indier; 
berg (Das Naturreich des Menschen; Heidelberg, 1808, 1 vol. Svo. — Hvm- 
Berlin,1835, fol.), and lately, I. Geof- boldt (W. v.), Ueber die Kawi- 
froy St. Hilaire (Hist. nat. g^o^rale, Sprache, auf der lusel Java; Berlin, 
Paris, 185(), tome i, Part 2, p. 167), 1836-39, 3 vols. 4to., Abh. Ak. d. 
has done. Compare also Chap. II, Wissensch. — Steinthal (H.), Gram- 
whero it is shown for every kind of matik, Logik und Psychologic ; Ber- 
group of the animal kingdom that lin, 1855, 1 vol. 8vo., — in the human 
the amount of their difference one family. All the Canirui bark; the 



RELATIONS OF INDIVIDUALS. 99 

of phenomena closely linked together ; and upon it are 
based not only the higher manifestations of the mind, but 
the very permanence of the specific diflferences which 
characterize every organism. Most of the arguments of 
philosophy in favour of the immortaUty of man apply 
equally to the permanency of this principle in other living 
beings. May I not add, that a future life, in which man 
would be deprived of that great source of enjoyment and 
intellectual and moral improvement which result from 
the contemplation of the harmonies of an organic world, 
would involve a lamentable loss. And may we not look 
to a spiritual concert of the combined worlds and all their 
inhabitants in presence of their Creator, as the highest 
conception of paradise ? 

SECTION XVIII. 

METAMORPHOSES OF ANIMALS. 

The study of Embryology is of very recent date ; the 
naturahsts of the past century, instead of investigating 
the phenomena accompanying the first formation and 
growth of animals, were satisfied with vague theories upon 
reproduction.^ It is true, the metamorphoses of Insects 

howling of the wolves, the barking kind, but only in the mode of utter- 

of the dogs and foxes, are only differ- ance. Among birds, this is, perhaps, 

ent modes of barking, comparable to stiU more striking. Who does not 

one another in the same relation as distinguish the note of any and every 

the monosyllabic, the agglutinating, thrush, or of the warblers, the ducks, 

and the inflecting languages. The the fowls, etc., however numerous 

FelidcB mew : the roaring of the lion their species may be, and who can 

is only another form of the mewing fail to perceive the affinity of (heir 

of our cats and the other species of voices T And does this not indicate 

the family. The Equina neigh or a similarity also in their mental 

bray : the horse, the donkey, the ze- faculties 1 

bra, the dow, do not differ much in ^ Buffo5 (G. L. LeClerg pe), 

the scale of their sounds. Our cattle, Discours sur la nature des Animaux; 

and the different kinds of wild bulls, Gendve, 1754, 12mo. ; also in his 

have a similar affinity in their into- OSuvres completes, Paris, 1774-1804, 

nations : their lowing differs not in 36 vols. 4to. 

H 2 



100 



ESSAY ON CLASSIFICATION. 



became very early the subject of most remarkable obser- 
vations ; ^ but so little was it then known that all animals 
undergo great changes, from the first to the last stages of 
their growth, that metamorphosis was considered a distin- 
guishing character of Insects. The differences between In- 
sects in that respect are, however, already found to be so 
great, that a distinction has been introduced between those 
which undergo a complete metamorphosis, — that is to say, 
which appear in three different successive forms, as larvae, 
pupae, and perfect insects, — and those with an incomplete 
metamorphosis, or whose larvae differ little from the perfect 
insect. Yet the range of these changes is so limited in 
some insects, that it is not only not greater, but is even 
much smaller than in many representatives of other 
classes. We may, therefore, well apply the term meta- 
morphosis to designate all the changes which animftla 
undergo, in direct and immediate succession,^ during their 
growth, whether these changes are great or small, pro- 
vided they are correctly determined for each type. 

The study of Embryology, at first limited to the inves- 
tigation of the changes which the chick undergoes in 
the egg, has gradually extended to every type of the 
animal kingdom ; and, so diligent and thorough has been 
the study, that the first author who ventured upon an 
extensive illustration of the whole field, C. K von Baer» 
has already presented the subject in such a clear manner, 
and drawn general conclusions so accurate and so com- 



* SwAMMERDAM (J.), Biblia Natu- 
rae, sive Historia Insectorum, etc. ; 
Lugduni-Batavorum, 1737-38, 3 vols. 
fol., fig. — Reaumur (R. Ant. de), 
M6moires pour servir h, THistoire des 
Insectcs ; Paris, 1734-42, 6 vols. 4to., 
fig. — ROESEL VON RosENnop (A. J.), 
Insectenbelustigungen ; Niirnberg, 
174(>-()1, 4 vols. 4to., fig. 



* I say purposely, "in direct and 
immediate succession,** as the pheno- 
mena of alternate generation are not 
included in metamorphosis. They con- 
sist chiefly in the production of new 
germs, which have their own meta- 
morphosis; while metamorphosis pro- 
per relates only to the successire 
changes of one and the same germ. 



METAMOKPHOSES OF ANIMALS. 101 

prehensive, that all subsequent researches in this depart- 
ment of our science may be considered as only a further 
development of the facts first noticed by him, and of the 
results he has already deduced from them.^ It was he 
who laid the foundation for the most extensive generali- 
zations respecting the mode of formation of Rnimalfl ; for 
he first discovered, in 1827, the ovarian egg of Mam- 
malia, and thus showed, for the first time, that there is no 
essential difference in the mode of reproduction of the 
so-called viviparous and oviparous animals, and that man 
himself is developed in the same manner as animals. 
The universal presence of eggs in all animals, and the unity 
of their structure, which was soon afterwards fully ascer- 
tained, constitute, in my opinion, the greatest discovery 
in the natural sciences of modem times.^ 

* Without referring to the works 8vo. — Valentin (G.), Handbuch der 
of older writers, such as De Qraaf, Entwickelungsgeschichte, etc.; Ber- 
Mai pighi,Haller, Wolf, MeckeljTiede- lin, 1835, 1 vol. 8vo. — Lehrbuch der 
mann, etc., which are all enumerated Phjsiologie des Menschen ; Braun- 
with many others inBiscHovr's arti- schweig, 1843, 2 vols. 8vo. — Longet 
cle, " Entwickelungsgeschichte," in (F. A.), Trait6 de Phjsiologie; Paris, 
Wagner's Handwdrterbuch der Phj- 1850, 2 yols. 8yo. — K5lliker (Alb.), 
siologie, vol. i, p. 860, 1 shall men- Microscopische Anatomie des Men- 
tion hereafter, chiefly those published schen; Leipzig, 1840-54, 2 vols. 8yo. 
since, under the influence of DSllin- fig. — See also Owen's Lectures, etc., 
ger, this branch of science has as- Siebold und Stannius's Lehrbuch, 
sumed a new character : — Baeb (C. and Oa rub's Morphologic, q. a., p. 37 
£.Y.),Ueber£ntwickelungsgeschichte and p. 24. I might further quote 
der Thiere ; Konigsberg, 1828-37, 2 almost every modern text-book on 
vols. 4to., ^g. The most important physiology ; but most of them are so 
work yet published. The preface is evidently mere compilations, exhibit- 
a model of candour and truthfulness, ing no acquaintance with the sub- 
and sets the merits of Ddllinger in a ject, that I purposely omit to men- 
true and beautiful light. As text- tion any other elementary works, 
books, I would quote, Bubdaoh (0. ' Baeb (C. E. a.), De Ovi Mamma- 
F.), Die Physiologic als Erfahrungs- Hum et Hominis Genesi ; Konigsberg, 
wissenschaft ; Leipzig, 1829-40, 6 1827, 4to., fig.— Pubkinjb (J. E.), 
vols. 8vo.; French, Paris, 1837-41, 9 Symbolaj ad Ovi avium historiam 
vols. 8vo. — MiiLLEB (J.), Handbuch ante incubationem ; Lipsice, 1830, 
der Physiologic des Menschen ; Cob- 4to., fig. — Wagner (R.), Prodromus 
lenz, 1843, 2 vols. 8vo., 4th edit. ; Historise generationis Hominis atque 
Engl., by W. Batlt, London, 1837, Animalium, etc.; Lipsice, 1836, 1 vol. 
8vo. — Waonbr (R.), Lehrbuch der fol., fig. — 1 cones physiologicas ; Lip- 
Physiologie; Leipzig, 1839-42, 2 vols, sia;, 1839, 4to., fig. Compare also 



102 ESSAY ON CLASSIFICATION. 

It was indeed a gigantic step to demonstrate such an 
identity in the material basis of the development of all 
animals, when their anatomical structure was already 
known to exhibit such radically diflFerent plans in their 
full-grown state. From that time a more and more ex- 
tensive investigation of the maimer in which the first germ 
is formed in these eggs, and the embryo developes itself ; 
how its organs grow gradually out of a homogeneous mass ; 
what changes, what complications, what connections, what 
functions, they exhibit at every stage ; how, in the end, 
the young animal assumes its final form and structure, 
and becomes a new, independent being, could not fail to 
])e a most interesting subject of inquiry. To ascertain 
all this, in as many animals as possible, belonging to the 
most diflferent types of the animal kingdom, soon became 
the principal aim of all embryological investigations ; and 
it can truly be said, that few sciences have advanced with 
such astonishing rapidity, or led to more satisfactory 
results. 

For the actual phases of the mode of development of 
the different types of the animal kingdom, I must refer to 
S2)ecial works upon this subject,^ no general treatise, em- 

Valencienkeb (A.) and FrCmy^ Re- Batrachians, the Lepidosteus, the 
cherches sur la composition des oeufs Amia, etc.; not to speak of the op- 
dans la s^rie des animaux, Compt.- portunities which thousands of miles 
Rend., 1854, vol. 39, p. 469, 525 and of sea-coast, everywhere easily acoes- 
570. sible, afford for embrjological invet- 
' The limited attention thus far ligations, from the borders of the 
paid in this country to the study of Arctics to the Tropics. In connexion 
Embryology, has induced me to enu- with Embryology, the question of 
mcrate the works relating to this Individuality comes up naturally. 
branch of science more fully than any See upon this subject: Lsuckakt 
others, in the hope of stimulating in- ^Rud.), Ueber den Polymorphismus 
vestigations in this direction. There der ludividucn oder die Erscheinung 
exist, upon this continent, a number der Arbcitstheilung in der Natur; 
of types of animals, the embryologi- Qiesscn, 1851, 4to. — Reichebt (C. 
cal illustration of which would add B.), Die monogene Fortpflanzung; 
immensely to the stock of our science: Dorpat, 1852. — IIuxlet (Th. 11.), 
such are the Opossum, the Ichthyoid Upon Animal Individuality; Ann. 



METAMORPHOSES OF ANIMALS. 103 

bracing the most recent investigations, having as yet been 
published ; and I must take it for granted, that, before 
forming a definite opinion upon the comparisons instituted 
hereafter between the growth of animals and the structural 
gradation among full-grown animals, or the order of suc- 
cession of the fossils characteristic of difierent geological 
periods, the necessary information respecting these changes 
will have been gathered and mastered by my readers suffi- 
ciently to enable them to deal with it freely. 

The embryology of Poljrpi has been very little studied 
thus far ; and what we know of the embryonic growth of 
these animals relates chiefly to the family of Actinoids. ^ 
When the young is hatched, it has the form of a little 
club-shaped or pear-shaped body, which soon assumes the 
appearance of the adult, from which it differs only by 
having few tentacles. The mode of ramification and the 
multiplication by buds have, however, been carefully and 
minutely studied in all the families of this class.^ Acalephs 
present phenomena so peculiar, that they are discussed 
hereafter in a special section. Their young ^ are either 

and Mag. Nat. Hist., 2nd ser., 1852, (L.), Twelve Lectures, etc. p. 40 et 
ToL 9, p. 507. — FoBBBS (Ed.), On the seq. — Haimb (J.), M6moire sur le 
supposed Analogy between the Life L6rianthe, Ann. 8c. Nat. 4e 86r.,1854, 
of an Individual and the Duration of yol.i. — ^Note sur le d^veloppement des 
a Species ; Ann. and Mag. Nat. Hist., Actinies, Oompt.-Bend., 1854, vol. 39, 
2nd ser., 1852, vol. 10, p. 59.— Bbavn p. 437 et 595. 
(Al.), I>u Indiyiduum der Pflanze, ' SeeDANA*sZoophyte8,andMILNfi- 
q. a. — Betrachtungen Ciber die £r- Edwabds et Haimb, Recherches, etc., 
Bcheinung der YeijSngung in der Na- q. a., p. 44, n. 1. 
tur; Freiburg, 1849, 4to., fig. ' Siebold (C. Th. E. y.), Beitrage 
^ Sabs (M^, Beskrivelser og Jagt- sur Naturgeschichte der wirbellosen 
tagelser over nogle maerkelige elTer Thiere, Neueste Schriften der Natur- 
nye i Havet ved den Bergenske Eyst forsch. Gesellschaft in Dansig ; Dan- 
levende Djr, etc.; Bergen, 1835, 4 to. zig, 1839, 4to., p. 1-35. — Loyek (S. 
— ^Fauna uttoralis Norvegise ; Chris- L.), Beitrag zur Kentniss der Gattun- 
tiania, 1846, foL, fig. — Rathke (H.), gen Oampanularia und Syncoryne, 
in Burdach*s Physiologic, vol. ii, Snd Wiegm., Arch., 1837, pp.249 and 321 ; 
edit, p. 215.^ — Zur Morphologic, Rei- French Ann. Sc. n. 2de s6r., vol. xv, 
sebemerkungen aus Taurien ; Riga p. 157. — Sabs (M.), Beskrivelser, q. 
und Leipzig,! 837, 4to., fig. — Aoassiz a. — Fauna littoralis, q. a. — Einige 



104 ESSAY ON CLASSIFICATION. 

pol)rp-like or resemble more immediately the type of their 
class. Few multiply in a direct, progressive development 

Worte uber die Entwickelung der Lectures, etc., q. a. — Debor (Ed.), 
Meduscn ; Arch. f. Naturg., 1857, i, Lettre sur la g6n6ration mMusipare 
p. 117. — NoBDMANN (Al. t.), Sur les des Polypes Hydraires ; Ann. Sc Nat. 
changements que T^gc apporte dans 3e 86r., 1849, toI. xii, p. 204. — Kbohh 
la mani^re d'etre des Campanulaires, (A.), Bemerkun^en uber die Oe- 
Oomptes-ReDdus, 1834, p. 709. — schlecbtsyerh&ltDisse der Sertolari- 
Steenstbup (J.), Ueber den Qenera- nen; Muller's Arch.,1843,p.l74. — Ve- 
tions-Wechsel oder die Fortpflanzung ber die Brut des Cladonema radiatun 
und KntwickeluDg durcb abwech- und deren Entwickelung sum SUtu- 
selnde Generationen, Uebers. von Lo- ridium, Miiller^s Arch., 1853, p. 4S0. 
bexzen; Kopenh., 1842, 8vo., fig.; — V eher Podocoryne cameayOin wid 
Engl, by G. Busk (Ray Society), Lon* die Fortpflanzungsweise ihrer medu- 
doD, 1845, 8vo. — Van Bbneden (P. senartigenSprGsslinge; WiegnuArch. 
J.), Memoire sur les Campanulaires 1851, i, p. 263. — Ueber oinige niedere 
de la cdte d'Osteude, etc., M6m. Ac. Thiere ; Mtdler*8 Arch., 18513, p. 137. 
Bruz., 1843, vol. xvii, 4to., fig. — Re- — Ueber die fruhesten Entwickel- 
cherches sur TEmbryog^nie des Tu- ungsstufen der Pelagia noctUwoa; 
bulaircs, etc., M6in. Ac. Brux., 1844, Mdller^s Archiv., 1855, p. 491. — K6ii- 
4to., fig. — Ddjabdin (Fel.), Obser- likeb (A.), Die Schwimmpolypen, 
vations sur un nouveau genre de M6- etc., q. a., p. 44. — BusoH (W.), Beo- 
dusaires {Cladonema)^ provenant de bachtungcn uber Anatomie und Ent- 
la metamorphose des Syncorynes ; wickelungsgeschichte einiger wirbel- 
Ann. Sc. n. 2d6 86r., 1843, vol. 20, p. loser Seethiere; Berlin, 1851, AXo^ 
370. — Memoire sur le d^vcloppement fig., pp. 1, 25 and 30. — OEGEHBAnKB, 
des M6dusaire8 et des Polypes Hy- K5llikeb und Mulleb, Bericht uber 
draires; Ann. Sen. 3e s^r., 1845, yoI. einige im Herbste 1852 in Messinm 
4, p. 257. — Will (J. G. Fr.), Horfe angestellte anatomische Untersuch- 
Tergestinao; Leipzig, 1844, 4to , fig. ungcn, Zeitsch. f. wiss. Zoo!., voL 4, 
— Prey (H.) und Ledckart (R.), p. 299. — Geqenbaueb (C), Ueber die 
Beitriigc zur Kenntniss wirbelloser Entwickelung yon Doliolum, der 
Thiere ; Braunschweig, 1847, 4to., Scheibenquafien und von Sagitta, 
fig. — Daly ELL (Sir J. G.), Rare and Zeitsch. f. wiss. Zool., 1853, p. 13. — 
BLemarkaltle Animals of Scotland, Beitrage zu nahem Kenntniss der 
etc.; London, 1847, 2 vols. 4to. fig. — Schwimrapolypen (Siphonophoren), 
Forbes (Ed.), Monograph of the Zeitsch. f. wiss. Zool., 1853, Tol. 5, p» 
British Naked-eyed Medusae; Lon- 285. — Ueber Diphyes turgida^ etc., 
don, 1847, 1 vol. fol., fig. (Ray So- Zeitsch. f. wiss. Zool. 1853, vol. 5, p. 
ciety). — On the Morphology of the 442. — Ueber den Entwickelunncy* 
Reproductivo System of Sertularian clus von Doliolum, etc., Zeitsch. f. 
Zoophytes, etc.; Ann. and Mag. Nat. wiss. Zool., 1855, vol. 7, p. 283. — ^Be- 
ll ist., 1844, vol. 14, p. 385. — Leydiq mcrkungen iiher die RandkSrper der 
(F.), Einige Bemerkungen iibcr den Mcdusen, Miiller's Arch.,1856,p.230. 
Ban der Hydren,Miillcr, Arch., 1854, — Studien iibcr Organisation und 
p. 270. — EcKER (A.), Zur Lehre vom Systcmatik der Ctenophoron, A^^, 
Ban und Lebcn der Kontraktilcn f. natz., 1850, i, p. 163. — Fba5TZIU8 
Substanz der niederstcn Thiere; Ba- (Al. v.), Ueber die Jungen der Ce- 
sel, 18-lH, 4to.; also in Zeitsch. f. w. phca, Zeitsch. f. wiss. Zool., vol. 4, p. 
Zool., 1840, vol. i, p. 218. — Rouoet's 118. — Miiller (J.),Uebereineeigen* 
papers on Hydra 1 have nut yet been thiimliche Mcduso des Mittelmeerea 
able to secure. — Agassiz (L.), Twelve und ihrcn Jugendzustand, Mullcr*8 



METAMORPHOSES OF ANIMALS. 105 

As to Echinodenns, they have for a long time ahnost 
entirely escaped the attention of embryologists ; but lately 
J. MuUer has published a series of most important inves- 
tigations upon this class, ^ disclosing a wonderful diversity 

Arch., 1851, p. 272. — Scbultze (M.), Nat., 4© s^r., 1854, vol. 2. — Schultzb 
Ueber die mannlichen Geschlechts- (Max.), Ueber der Bau der Gallert- 
theile der Campanularia genictdata, scheibe der Medusen, MuHer's Arch., 
Mailer's Arch., 1850, p. 53.— Hiscks 1856,p.311.— M'CBADT(J.),Descrip- 
(TH.), Notes on the Reproduction of tion of Oceania Nutricida and the 
the CampannlariadaB, etc., Ann. and embrjological history of a singular 
Mag. Nat. Hist., 2nd ser., 1852, vol. Medusan larva found in the cavity of 
10, p. 81. — Further Notes on British its bell ; Proceed. Elliott Society, 
Zoophytes, Ann. and Mag. Nat. Hist., Charleston, S.C., 1857. — Wright (T. 
1853, vol. 15, p. 127. — Allma5 (G. S.),On Hydractinia EchinataylSAinh. 
J.), On Hydroids, Rep. Brit. Ass. New Phil. Joum., new series, 1857. — 
Adv. 8e., 1852, p. 50. — On the Struc- Observations on British Zoophytes, 
ture of Hydratiridis, Proc. Brit. Ass. Edinb. New Phil. Joum., new series, 
1853, p. ^ — ^Derbss (A.), Note sur 1857. — Observations on British Zoo- 
lea organes reproducteurs et Tembry- phy tes : Laomedea acuminata, Tri- 
ogenie du Ctfanea ehrysaora, Ann. chydra pudica, and Tubvlaria indi- 
Sc. Nat., 3e sir., 1850, vol. 13, p. 377. vim; Edinb. New Phil. Joum., new 
— VooT (C), Ueber die Siphonopho- series, 1868. — On the Reproduction 
ren, Zeitsch. f. wiss. Zool., 1852, vol. of Cydippe pomiformiM, Edinb. New 
3, p. 522. — Untersuchungen iiber Philos. Joum., new series, 1856, vol. 
Thierstaaten ; Frankfurt, 1851, 8vo^ 4, p. 85.— Peach (C. W.), Notice of 
— Siphonophores de Nice, q. a., p. 44. a Curious Metamorphosis in a Zoo* 
— HvxLBT (Th. £.), On the Anato- phyte-like Animal, Edinb. New Phi- 
my and Affinities of the Family of los. Joum., new series, 1856, vol. 4, 
the Meduse, Philoe. Trans. Roy. Soc, p. 162. 

1849, ii, p. 413. — An Account of Re- ^ Beskrivelser, etc., p. 37. — Ueber 

searches into the Anatomy of the die Entwickelung der Seesterae, 

Hydrostatic Acalephse, Proc. Brit. Wiegm. Arch., 1844, 1., p. 169, fig. — 

Ass. Adv. Sc., 1851, p. 78. — Lkuck- Fauna littoralis, etc., p. 47. — Miii> 

ART (R), Zoologisehe Untersuchun- ler, (J.,) Ueber die Larven u. die 

gen ; Giessen, 1853-54, 4to., fig., 1st Metamorphose der Ophiuren u. 

Faac. — Zur n&hem Kenntniss der Seeigel,Akad.d. Wiss.; Berlin, 1848. 

Siphonophoren von Nizza, Wiegm. — Ueber die Larven u. die Metamor- 

Arch^ 1854, p. 249. — Medusen von phose der Echinodermen, 2te Abh., 

Nizxa, q. a^ p. 44.— Stimpson (W.), Ak. d. Wiss.; Berlin, 1849. — Ueber 

Synopsb of the Marine Invertebrata die Larven u. die Metamorphose der 

of Grand Manan, Smithson. Contrib., Holothurien u.Asterien, Ak. d. Wiss. ; 

1853, 4to., ^g, — Leidt (Jos.), Con- Berlin, 1850. — Ueber die Larven u. 

tributions towards a Knowledge of die Metamorphose der Echinodermen, 

the Marine Invertebrate Fauna, etc., 4te Abh., Ak. d. Wiss. ; Berlin, 1 852. — 

Joum. Acad. Nat. Sc., Philad., 2nd Ueber die Ophiurenlarven des Adri- 

ser., 1855, vol. 3, 4to., fig. — See also atischen Meeres; Ak. d. Wiss.; Ber- 

below, Sect, 20. — Oosss (Th. H.), lin, 1852. — Ueber den allgemeinen 

Natundist's Rambles on the Devon- Plan in der Entwickelung der Echino- 

shire Coast; London, 1853, 8vo. — dermen, Ak. d. Wiss. ; Berlin, 1853. — 

QuATREFAGES (A. de), M^moire sur Ueber die Gattungen der Seeigellar- 

Torganisation des Physales, Ann. Sc. ven, 7te Abh., Ak. d. Wiss., 1855. — 



106 ESSAY ON CLASSIFICATION. 

in the mode of their development, not only in the diflFer- 
cnt orders of the class, but even in different genera of the 
same family. The larvae of many have a close resem- 
blance to diminutive Ctenophorae, and may be homolo- 
gized with this type of Acalephs. 

As I shaU frequently refer hereafter to the leading 
divisions of the animal kingdom, I ought to state here, 
that I do not adopt some of the changes which have been 
proposed lately in the limitation of the classes^ and which 
seem to have been pretty generally received with favour. 
The imdivided type of Kadiata appears to me as one of 
the most natural branches of the animal kingdom, and I 
consider its subdivision into Coelenterata and Echinoder- 
mata as an exaggeration of the anatomical differences ob- 
served between them. ^ As far as the plan of their struc- 
ture is concerned, they do not differ at all, and that 
structure is throughout homplogical In this branch I 

Ueber den Canal in den Eiem der Ueber die Larve dei Comatnls, M&l- 

Holothurien, Muller's Arch., 1854, p. ler*8 Arch., 1849, p. 400. — Krohv, 

60. — Fortsetzung der Beobachtun- (A.,) Ueber die Entwickelung der 

gen uber die Metamorphose der Echi- Seesteme und Holothurien, Mfiller's 

nodermen, MCdler's Arch., 1855, p. Arch., 1853, p. 317. — Ueber die Eni- 

67. — French abstracts of these papers wickelung einer lebendig gebfthren- 

may be found in Ann. Sc. Nat., 3e den Ophiure, MuUer's Arch., 1851, p. 

86r., 1852 and '53, vols. 17, 19, and 338.— Ueber die Larre dee Eckinu$ 

20, and 4e s^r., 1854, vol. 1, by C. brevUpinosuSy Mfdler's AtcIl, 1853, 

Dareste. An English account is p. 361. — Beobachtungen &ber Echi- 

published by Huxley, TTh. H.,) Re- nodermenlaryen,MCdrer*BArclL,1854, 

port upon the Researcnes of Prof. p.208. — Ueber einenneuenEntwidcel- 

Midler into the Anatomy and Deve- ungsmodus der Ophiuren, MfiUer*B 

lopment of the Echinoderms, Ann. Arch., 1857, p. 369. — ScHnLTSB,(M.), 

and Mag. Nat. Hist. 2d ser., yol. 8, Ueber die Entwickelung tod Ophio- 

1851, p. 1. — Kobe5 und Danielssen lepis squamata, Mfiller'a Arch., 1858, 

in Nyt Magazin for Naturvid, yol. 5, p. 37. — Gosse (R. H.), Tenby, a ae^- 

u. 253, Ohristiania, 1847 ; Ann. Sc. side holiday ; London, 1856, 8to. 

Nat., p. 347. See also Fauna littoralis ^ I am surprised to find thai J. 

Norvegise, 2d. liyr. — Aqassiz, (L.,) M&Iler favours the view of a cloee 

Twelve Lectures, etc., p. 13. — Der- affinity between Polyps and Aca- 

BES, (A.,) Sur la formation de Tern- lephs, and still more that he u in- 

bryon chez Toursin comestible, Ann. clined to refer the Bryozoa to the 

Sc. Nat., 3e sor., vol. 8, p. 80.— Busu, type of iUdiata, Muller's Arch., 1858, 

(W.,) Beobachtungen, etc , 4. a. — 8vo., p. 105. 



METAMORPHOSES OP ANIMALS. 107 

recognize only three classes, Polypi^ AcalephcBy and Echi- 
nodermata. The chief diflFerence between the two first 
lies in the radiating partitions of the main cavity of the 
Polypi, supporting the reproductive organs ; moreover the 
digestive cavity in this claas consiBts of an inward fold of 
the upper aperture of the common sac of the body, while 
in Acalephs there exist radiating tubes, at least in the 
proles medusinay which extend to the margin of the body 
where they anastomoze, and the digestive cavity is hol- 
lowed out of the gelatinous mass. This is equally true of 
the Hydroids, the Medusae proper, and the Ctenophorse ; 
but nothing of the kind is observed among Polypi Si- 
phonophorse, whether their proles medusina becomes ifree 
or not, and Hydroids, agree in having, in XhQ proles me- 
dusina, simple radiating tubes, uniting into a single cir- 
cular tube aroimd the margin of the bell-shaped disk. 
These two groups constitute together one natural order, 
in contradistinction to the Covered-eyed Medusae, whose 
radiating tubes ramify towards the margin and form a 
complicated net of anastomoses. Morphologically, the 
proles polypoidea of the Acalephs is as completely an 
Acaleph as their proles mediisina} and, whether they 
separate or remain connected, their structural relations 
are everjrwhere the same. A comparison of Hydractinia, 
which is the most common and the most polymorphous 
Hydroid, with our common Portuguese Man-of- War, {Phy- 
scdia,) will at once show the homology of their most poly- 
morphous individuals. 2 

The embryology of MoUusks has been very extensively 

^ I flhaU show this fully in the • ' It has already been stated above, 

third volume of my contributions to that the Milleporina are not true 

the Natural History of the United Polyps, but Hydroids, closely allied 

States. Meanwhile, see my paper on to Hydractinia, by their structure 

the structure and homologies of Ka- and their polymorphism, 
diata, q. a., p. 28. 



108 ESSAY ON CLASSIFICATION. 

investigated, and some types of this branch are among 
the very best known in the animal kingdom. The natural 
limits of the branch itself appear, however, somewhat 
doubtful. I hold that it must include the Bryozoa^ ^ which 
lead gradually through the Brachiopods^ and Tunicata to 
the ordinary Acephala, and I would add that I have satis- 
fied myself of the propriety of uniting the Vdrticellidfle 
with Bryozoa. On the other hand, the Cephalopods can 
never be separated from the MoUusks proper, as a distinct 
branch ; and the partial segmentation of their yolk no 
more affords a ground for their separation, than the total 
segmentation of the yolk of Mammalia would justify their 
separation from the other Vertebrata. Moreover, Cepha- 
lopods are, in aU the details of their structure, homologous 
Avith the other MoUusks. The Tunicata are particularly 
interesting, inasmuch as the simple Ascidians have pedun- 
culated young, which exhibit the most striking resemblance 
to BoUenia, and form, at the same time, a connecting link 
wth the compound Ascidians.^ The development of the 

^ Allma5, (G. J.,) On the Present (F.,) Infusionsthiere ftuf ihre Eiit« 

State of our Knowledge of the Fresh wickelungsgeschichte untersucht ; 

Water Polyzoa, Proc. Brit. Asso. Adv. Leipzig, 1854, I vol, 4to. ^g. — 

Sc, 20th Meet. ; Edinburgh, 1850, p. Frantzius, (Al. y.,) Anftlecta ftd 

305. — Proc. Irish Ac. 1850, vol. 4, p. Ophrydii versatilis historiam natu- 

470. — Ibid., 1853, vol. 5, p. 11. — Mo- ralem, Vratislav, 1849. — ^LAOHMAVir, 

nograph of the Fresh-water Polyzoa, (C. F. J.,) Ueber die Organiiation der 

Ray Soc. — Van Beneden (P. I.,) Infusorien, besonders der VorticeUeo, 

Kechcrches sur T Anatomic, la phy- Miiller's Arch., 1856, p. 340. Having 

siologio et le d6veloppement dcs Bry- satisfied myself that the Vorticellidn 

ozoaires qui habitent la cdte d'Os- are Bryozoa, I would also refer here 

tende, Nouv. Mem. Ac. Brux., 1845, to all the works on Infusoria in 

vol. 18. — DuMORTiER, (B.C.,) et Van- which these animals are considered. 

Beneden, (P. J.) Uistoire naturelle ' I see, from a short remark of 

dcs Polypes compos6s d'cau douce, Leuckart, Zeitsch. f. wiss. Zool., vol. 

M6m. Ac. Brux., 1850, vol. IG, 4to. 7, suppl., p. 115, that he also has per- 

fig. — IIiNCKs, ^Tn.,) Notes on British ceived the close relationship which 

Zoophytes, with Descriptions of some exists between Brachiopods and Bry- 

New Species, Ann. and Mag. Nat. ozoa. See also Hancock (Alb.), On 

Hist., 2d ser., 1851, vol. 8, p. 353.— the Organization of the Brachiopoda, 

EiiRENBERQ, (C. Q.,) Die Infusions- Proc. Roy. Soc. ; London, 1857, p. 

thiero als vollkommene Organismen, 463. 

Leipzig, 1838, 2 vols. fol. fig. — Stein, ' Saviqny, (J. C.,) M6moire8 aur 



METAMORPHOSES OP ANIMALS. 109 

Lamellibranchiata seems to be very uniform, but they 
differ greatly as to their breeding, many laying their eggs 
.before the germ is formed, whilst others carry them in 
their gills until the young are entirely formed.^ This is 
observed particularly among the Unios, some of which, 
however, lay their eggs very early, while others carry them, 
for a longer or a shorter time, in a special pouch of the 
outer gill, which presents the most diversified forms in 

les Anim. sans Vertebras, etc. q. a.-^ Leipzig, 1832, 4to., fig. — Quatre- 

Ghamisso, (Ad. v.,) De animalibus faoes (Arm. de,), Sur rembrjog^nie 

quibusdam e classe Vermium Lin- des Tarets, Ann. Sc. Kat., 3e s^r., 

nseana. Pasc. 1, De Salpa, Berol. 1849, vol. 2, p. 202. — Sur la vie in- 

1819, 4to., fig. — Mbtbv, (F. J.,) Bei- terbranchiale des petites Anodontes, 

trage zur Zoologie, etc., Ist Abth., Ann. Sc. Nat., 2de s^r., vol. 5, p. 321. 

uber Salpen, Not. Act. Nat. Cur. — Loven (S. L.), Om UtveckllDgen 

1832, vol. 16. — Edwards, (H.MILNE-) of Mollusca Acephala, Overs. Vet. 

Observations sur les Ascidies com- Akad. FQrhandl. ; Stockholm, 1849. 

poshes des c6tes de la Manche ; Paris, — Germ. Muller*s Arch., 1848, p. 531, 

1841, 4to., fig. — Sar8, (M.,) Beskri- and Wiegman*s Arch., 1849, p. 312. 

velser, q. a. — Fauna Utt., q. a. — — Prevost, (J. L.,) De la g6n6ration 

Van Beneden, (P. J.,) Recherches chez la moule des peintres, M6m. Soc. 

sur rembryog^nie, ranatomie et la Phjs. ; Geneve, 1825, vol. 3, p. 121. 

physiologie des Ascidies simples, — Voot, (0.,) Bilder aus dem Thierle- 

Mem. Ac. Bruz., 1847, vol. 20. — ben; Frankfurt, 1 852, 8vo. — Schmidt, 

Krohn, (A.,) XJeber die Entwickel- (0.,) Ueber die Entwickelung von Ct/- 

ung der Ascidien, Muller*8 Arch., clcu cali/culata, Drap. Muller's Arch., 

1852, p. 312.-— KfiLLiKER, (A.,) et 1854, p. 428.— Lbydio, (F.,) Ueber 

L5wio, De la composition et de la Cycliu cornea, Muller*s Arch., 1855, 

structure des enveloppes des Tuni- p. 47. — Lacafe-Duthiers, (H.,) Re- 

ciers, Ann. Sc. Nat. 3e s6r., vol. 5, p. cherches sur les organes g6n6taux des 

193. — HuxLBT (Th. H.), Observa- Ac6phales lamellibranches, Ann. Sc. 

tions upon the Anatomy and Physi- Nat. 4e. s^r., 1854, vol. 2. — M6moire 

ology of Salpa and Pyrosoma, Philos. sur Torgane de Bojanus des Ac6phales 

^l^ns. B. »>c., 1851, II., p. 567. — lamellibranches, Ann. Sc. Nat., 4e. 

EscHRiOHT (D. F.), Anatomisk-phy- s^r., 1855, vol. 4. — Observations sur 

tiologiske UndersOgelser over Sal- rhermaphrodisme des Anodontes, 

peme, Ki5b. 1840, fig.— Stbbnstrup, Ann. Sc. Nat., 4e. s6r., 1855, vol. 4. 

(J.,) Ueber den Generationswechsel, — M6moire sur le d6veloppement des 

q. a. — Voot (C), Bilder aus dem branchies des Mollusques Ac^phales 

Thierleben, Frankfurt a. M., 1852, lamellibranches, Ann. Sc. Nat., 4e. 

8vo. — MuLLBR (H.), Ueber Salpen, s6r., 1856, vol. 5. — Histoire de Tor- 

Zeitsch. f., wiss., Zool., vol. 4, p. 329. ganisation et du d^veloppement du 

— LsucKART (R.), Zoologische tJnter- Dentale, Ann. Sc. Nat., 4e. s^r., 1856, 

suchungen, Giessen, 1853-54, 4to., vol. 6. — I have not yet been able 

fig., 2a Fasc. — Geoenbauer (C), to secure Davaisne'r paper on the 

Ueber die Entwickelung von Dolio- reproduction of the Oyster, published 

lum, &c., q. a., p. 104. in the M6moires de la Soci6t^ de Bio- 

^ Oarub (C. G.), EntwickelungS" logie. 
geschichte unserer Flussmuschel, 



110 ESSAY ON CLASSIFICATION. 

diflFerent genera of the family. Nothing is as yet known of 
the development of Brachiopods. The Gasteropods^ ex- 



^ Cabus, (G. G.,) Yon den aussem Beitrag sor nahem Kenntniss 

Lebensbedingimgen der weiss- and Thieres in embx7ologischer,anatonii»- 

kaltblutigen Thiere; Leipzig, 1824, cher und hiBtologiBcher Besidmng, 

4to., fig. — Pbkyost, (J. L.,) Be la Zeitsdu £, wias. ZooL, 1850, toL S, p. 

g6n6ration chez le Lymnde, M6m. Soc. 125. — KSllikbb, (A.,) q. a., Zeitwn, 

Fhja.y Gen^Te, yoL 5, p. 119. — Sabs, f. wiss. Zool., toL 4, p. 333 and 369. 

(M.,) Zur Entwickelungsgeschichte — Mulleb, (J.,) Ueber Tenchkdene 

der Mollosken und Zoophyten ; Formen yon Seeihieren, Muller*8 

Wiegm.Arch.,1837,I.,p.402; 1840,1, Arch., 1854, p. 69.— Uebv Syru^Mi 

p. 196. — Zus&tze zu der von mir gege- digitata and ober die Eneugong Yon 

Denen Dartstellung der Entwickelung Schnecken in Holothurien ; Berlin, 

der Nudibranchien ; Wiegm. Arch., 1852, 4to. fig. — The renuurkable case 

1845, 1, p. 4. — Quatbefaqbs (Abm. described in this Pikper Admits of an 

DE,) M^moire sur TEmbryog^nie des explanation whicn MoUer has not 

Planorbes et des Lymn6es ; Ann. Sc. considered. It is known that fishes 

Nat., 2de ser., vol. 2, p. 1 07. — Yam Be- (Ophidium) penetrate into Uie caTitr 

NEDEir, (P. J.,) Recherches sur le d6- of the body of HolotharisB, through 

Teloppement des Aplysies ; Ann. Sc. its posterior opening. (Db BoesBT, 

Nat., 2de s^r., vol. 15, p. 123. — Yah Notice, etc., M6m. Soc. 8e. Nat., 

Benbden, (P. J.,) et WiNDisoHMAN, Nouch., 1839, yoI. 8, 4to. — I haTe 

rOn.,) Recherches sur rEmbryog6nie observed the fa^ct myself in Florida.) 

des Limaces, M6m. ; Ac. Brux., 1841. The similarity of ErUoeoneka mm- 

— Jacquemix, (Em.,) Sur le d^ve- bilU with the embryonic ^ell of 

loppement des Planorbes ; Ann. Sc. yarious species of littorinss, such as 

Nat., Yol. 5, p. 117 ; Nov. Act. Nat. Lacuna vincta, the deyelopment of 

Our., vol. 18. — DuMORTiEB, (B. 0.,) which I had an opportunity of stndy- 

M6moire sur Ics Evolutions de Tern- log, suggests the possibility, that 

bryon dans les Mollusques Gast^ro- some species of this family, of which 

pedes, M6m. ; Ac. Brux., 1836, vol. there are many very small ones, se- 

10. — Laueent, (J. L. M.)) Observa- lect the Synapta as their breeding 

tions sur le d6veloppemcnt de Toeuf place, and leave it after depositing 

des Limaces ; Ann. Sc. Nat., vol. 4, their eggs, which may become con- 

p. 248. — PovcHET, (F. A.,) Sur le d6- nected with the Synapta, as our 

veloppement de Tembryon des Lym- Mistletoe or the OroMmcne and many 

n6es ; Ann. Sc. Nat., 2de 86r., vol. 10, other parasitic plants with Uie plants 

I>. 63. — VooT, (0.,) Recherches sur upon which tney grow. — OsoEir- 

'Embryologie do rActocon ; Ann. Sc. baueb, (0.,) Beitrage zur Entwickel- 

Nat. 3e s6r., 1846, vol. 6, p. 5. — ungsgeschichte der Landgasteropo- 

Beitrag zur Entwickelungsgeschichte den, Zeitsch, f. wiss. ZooL, 1858, vol. 

eines Cephalophoren ; Zeitsch. f. wiss. 3, p. 371. — Untersuchungen &ber 

Zool., 1855, vol. 7, p. 162. — Schultze, Pteropoden und Heteropoden ; Leip- 

(M.,) Ueber die Entwickelung des zig, 1855, 1 vol., 4to. fig. — Kobbv, 



Tergipe* lactniUattis; Wiegm. Arch., (J.,) und Daitielssen, (D. C.,) 

1849, 1., p. 268.— Warneck, (N. A.,) til Pectin ibranchiemes Udviklings- 

Ueber die Bildung und Entwickelung historic, Bergen, 1851, 4to. ; French 

des Embryo bei Gastcropodcn, Bull. Sc. Nat., 1852, vol. 18, p. 5K57, and 

Soc. Imp. ; Moscou, 1850, vol. 23, I., 1853, vol. 19, p. 89 ; also (}erm. in 

p. 90. — Schmidt, (0.,) Ueber die Ent- Wiegm. Arch., 1853, p. 173 ; see also 

wickelung von Limax agreatisy Mill- Fauna littoralis Norvegise 2de livr. — 

ler's Arch., 1851, p. 278. — Letdio, Nobdmann, (Al. V.,) Yersuch einer 

(F.,) Ueber Paludina vivipnray ein Monographic von TVrys^iSirftMirfini; 



METAMORPHOSES OF ANIMALS. Ill 

hibit a much greater diversity in their development than 
the Lamellibranchiata. Even among the terrestrial and 
aquatic Pulmonata there are striking differences. Some 
of the Pectinibranchiata are remarkable for the curious 
cases in which their eggs are hatched and the young de- 
veloped, to an advanced state of growtL The cases of 
Pyrula and Strombus are among the most extraordinary 
of these organic nests. The embryology of Cephalopods^ 
has been illustrated in a masterly way by KoUiker. 

St. Petersburg, 1844, 4to. — Lsvo- Ueber die Entwickelune der PhTl- 

KABT, (R.^ Zoologische Untersu- lirhoe Bucephalum, Mailer's Arch., 

chungen ; Giessen, 185d-54, 4to., fig., 18/58, p. 35. 

3d Fmc — HvxLBT, (Th. H.,) On the ^ KdUiiKBB, (Alb.,) Entwickel- 

Morphology of the Oephalous Mol- ungseeschichte der Gephalopoden, 

Insca^ etcTPhil. Trans. R. Soc., 1853, Zurich, 1844, 4to., fig.— Yak-Bene- 

I., p. S^. — Hoao, (Jabez,) On the deit, ^P. J.,) Recherches sur TEm- 

Derelopment and Growth of the brjogenie des S^pioles, N. M6m. Acad. 

Waternmil, Quart. Micr. Jour., 1854, Bruz., vol. 14, 1841. — Coldstream, 

p. 91. — Reid, (J.,) On the Develop- (Z.,) On the Ova of Sepia, Lond. and 

ment of the Ova of the Nudibran- Ed. Phil. Mag., Oct., 1833. — Duoes, 

chiate Mollusca, Ann. and Mag. Nat. (Ant.,) Sur le d^veloppement de Tem- 

Hist., 1846, vol. 17, p. 377. — Gabpen- bryon chez les Moliusques 06phalo- 

TEB, (W. B.,) On the Development of podes, Ann. Sc. Nat., vol. 8, p. 107. — 

the Embryo of Purpura ZapiUuSf Rathke, (H.,) Perothis, ein neues 

Quart. Micr. Joum., 1845, p. 17.— genus der Gephalopoden, M6m. Ac. ; 

LoBEN, (8.,) Ueber die Entwickelung St. Petersburgh, 1834, vol. 2, p. 149. 

von Ghiton, Arch. Naturz. 1856, I, (Is the young of some Loligoid Ge- 

p. 206. — Ejiohn, (A.,) Ueber einer phalopod.) — Milne-Edwabds, (H.,) 

neuen mit Wimpersegeln versehenen Observations sur les spermatophores 

(Sasteropoden, Arch. f. Naturz. 1853, des MoUusques G^phalopodes, etc., 

p. 223. — Beobachtungen aus der Ann. Sc, n., 2de s6r., vol. 3, p. 193. 

Entwickelungsgeschichte der Ptero- — K6lltkeb, (A.,) Hectocotylus Ar- 

podeUy Heteropoden, Echinodermen, jgfonatUcBy'DeWe ChiAJe und Beet. Trem- 

Maller*s Arch. 1856, p. 515, and 1857, octopodts, K., die Mannchen von 

p. 459. — Maodonald, (J. D.,) Re- Argoriauta Argo und Tremociopus 

marks on the Anatomy of MacgiUi- violaeeus, Ber. Zool. Anst. ; Wiirz- 

vrayapdagxeatkudCheUtropisHaielziy berg, 1849, p. 69. — Mulleb, (H.,) 

Trans. Boy. 8oc.;. London, 1855. II, Ueber das Mannchen von Argonauta 

p. 289 ; — Further observations, etc., Argo und die Hectocotylen, Zeitsch. 

p. 295. — Glapabedb, (Ed.,) Anatomic f. wiss. Zool., vol. 4, p. 1. — Vebaxy, 

und£ntwickelung8ge8chicntederi\^0- (J. B.,) et Yogt, (G.,) M6moire sur 

rUifUi fiuvicUUva^VLWlet^^ Arch. 1857, les Hectocotyles et les males de quel- 

p. 109. — ^Beitrag fur Anatomic des ques O^phalopodes, Ann. 8c. n., 3e 

Cjftiottama degant, Muller*s Arch., ser., 1852, vol. 17, p. 147. — Roulin, 

1858, p. 1.— Sempeb, (G.,) Beitr&ge (F. D.,) De la connaissance qu'ont 

fur Anatomie und Physiologic der eue les anciens du bras copulateur 

Pulmonaten, Zeit. f. w. Zool. 1856, chez certains G^phalopodes, Ann. Sc. 

vol. 8, p. 340.— -SoHREiDEB, (A.,) N., 3e s6r., 1852, vol. 17, p. 188.— 



112 



ESSAY ON CIASSIFICATION. 



There is stiU much diversity of opinion among natu- 
ralists respecting the limits of Articnlata ; some being 
inclined to separate the Arthropods and Worms as dis- 
tinct branches, while others unite them into one. I 
confess I cannot see the ground for a distinction. The 
worm-like nature of the larvae of the majority of Arthro- 
pods and the perfect homology of these larvsB with the 
true Worms, seem to me to show beyond the possibility 
of a doubt, that all these animals are built upon one and 
the same plan, and belong, therefore, to one branch, which 
contains only three classes, if the principles laid down in 
my second chapter are at all correct, namely, the Worms, 
Crustaceans, and Insects. As to the Protozoa, I have little 
confidence in the views generally entertained respecting 
their nature. Having satisfied myself that Colpoda and 
Paramecium are the brood of Planariae, and OpaUna that 
of Distoma, I see no reason why the other Infusoria^ in- 
cluded in Ehrenberg's division Enterodela,^ should not 
also be the brood of the many lower Worms, the develop- 
ment of which has hitherto escaped our attention. Again, 
a comparison of the early stages of development of the 
Entomostraca with Rotifera might be sujficient to show, 
what Burmeister, Dana, and Leydig have proved in 
another way, that Rotifera are genuine Crustacea, and not 
Wonns. The vegetable character of most of the Anen- 
tera has been satisfactorily illustrated. I have not yet 
been able to arrive at a definite result respecting the 



Leuckart, (R.,) Zool. Unters. q. a. — 
Steenstrup, (J.,) Die Hectocotylen- 
bildung bei Argonauta und Tremoc- 
topus. crkl&rt durch Beobachtung 
ahnlicher Bildungen bei den Ccpha- 
lopoden im Allgcmeinen, Arch. Nat., 
1856, I, p. 211.— Trosciiel, (F. 11.,) 
Bemcrkungcn iiber die Ocpbalopoden 



von Messina. Arch. Nat., 1S57, 1, p. 
41. — Van der Hoeyen, (J.,) Beitimg 
zur Anatomie von NautUtu Pom" 
pilius L., besonders des M&imlicheii 
Thiercs, Arch. f. Nat. 1857, I, page 
77. 

* That the Vorticcllidae are Biyo* 
zoa, has already been stated aboTe. 



METAMORPHOSES OF ANIMALS. 113 

Rhizopods, though they may represent, in the type of 
Mollusks, the stage of yolk-segmentation of Gasteropods.^ 
From these remarks it should be inferred that I do not 
consider the Protozoa as a distinct branch of the animal 
kingdom, nor the Infusoria as a natural class.^ 

^ See also below, Chap. III., Sect. 1. Infusiorien. Ak. d. wiss. ; Berlin, 1855 

* ScHULTZE, (M.,) ^eitrage zur — Cohn, (F.,) Untersuchungen uber 

Katurgeschichte den Turbellarien, die Entwickelungsgcschichte der 

Qreifswald, 1851, 4to., fig. — Zoolo- Microscopischen Algen, Nov, Act. 

gische Skizzen, Zeitsch. f. wiss. Zool. Acad. N. G. 1854, vol. 24, p. 101 ; 

1852, Tol. 4, p. 178. MiiLLER, (J ,) Beitrage zur Entwickelunesge- 

Ueber eine eigenthiimliche Wurm- schichte der Infusorien, Zeitscn. f. 

larve, etc., Archiv., 1850, p. 485. — wiss. Zool. 1851, vol.3, p. 257. — Bei- 

Desob (E.,) On the Embryology of trage zur Eenntniss der Infusorien, 

Kemertes, with an Appendix on the Zeitsch. f. wiss. Zool. 1854, vol. 5, p. 

Embryonic Development of Polynoe, 420. — Ueber Encystirung von Am- 

Boston Joum. Nat. Hist. 1850, vol. 6, phileptus fasciola, ibid. p. 434. — Ob* 

p. 1 ; Muller*8 Archiv, 1848, p. 511. servation sur Torganisation et la pro- 

— Agassiz, (L.,) Colpoda and Para- pagation des Volvocin^es, Oorapt.- 

mecium are larvee of Planarise, Proc. Rend. 1856, vol. 43, p. 1054. — Ueber 

Am. Ass. Adv. Sc. ; Cambridge, 1849, Fortpflanzung von Naswda elegans, 

p. 439. — GiBABD, (Ch.,) Embryonic Zeit. f. wiss. Zool. 1857, vol. 9, p. 143. 

Development of Planocera dliptica, — Schultze, (M.,) Ueber den Orga- 

Jour. Ac. Nat. 8c. Phil., 2d ser. 1854, nismus der Polythalamien ; Leipzig, 

vol. 2, p. 307. — Ehreitbebo, (0. Q.,) 1854, 1 vol. fol. fig. — Beobachtungen 

Die Infusionsthierchen, etc., q. a. — uber die Fortpflanzung der Polytha- 

Microgeologie ; das Erder una Fel- lamien,Miiller's Archiv, 1856, p. 165. 

senschafiende Wirken des unsicht- — Archiac (Vic. d') and Haine (J.), 

baren kleinen selbststandigen Lebens Description des animaux fossiles du 

auf der Erde ; Leipzig, 1854, fol. — groupe nummulitique de Tlnde ; Pa- 

Ueber den Grunsand und seine ris, 1853, 4to. — Carter (H. J.,) De- 

Erlauterune des organischen Le- scrip tion of some of the Larger Forms 

bens, Ak. a., Wiss., Berlin, 1855, of Fossilized Foraminifera in Scinde, 

4to.— KuTZiKO, (F. T.,) Ueber die Ann. and Mag. Nat. Hist., 1853, p. 

Yerwandlung der Infusorien in nie- 161. — CARPENTER(W.B.),Rresearche8 

dere Algenformen, Nordhausen, 1 844, on the Foraminifera, Trans. Roy. iSoc, 

4to., fig. — K5LLIKEB, (A.,) Das Son- London, 1856, i, p. 181; ii, p. 547. — 

nenthierchen, ActinophrifS Soly Huxlet (Th. H.), Zoological Notes 

Zeitsch. f. w. Zool. 1849, I, p. 198. — and Observations made on Board 

Clapabidb, (Ed.,) Ueber Actino- H.M.S. Rattlesnake, upon Thalassi- 

phrys Eickamii, Miiller*s Arch., 1854, cola, a new Zoophyte ; Ann. and Mag. 

p. 398. — SiEBOLD, (C. Th. E. v.,) Nat. Hist., 2nd ser., 1851, vol. viii, 

Ueber einzelligePflanzen und Thiere, p. 433.'« — Miiller (J.), Ueber SphsB- 

Zeitsch. f. wiss. Zool. 1849, vol. 1, p. rozoum und Thalassicola, Ber. Ak. d. 

270. — Naeoell, (0.,) Gattungen ein- Wiss., Berlin, 1855, p. 229. — Ueber 

zelliger Algen ; Zurich, 1849, 4to. fig. die im Hafen von Messina beobach- 

— Bbaun, (A.,) Algarum unicellula- teten Polycystinen ; Ibid., p. 671. — 

rium genera nova et minus cognita; Ueber die Thalassicol en, Polycystinen 

Leipzig, 1846, 4to. fig. — Ueber Chi- und Acanthometren des Mittelmeeres, 

iridium, eine Gattungein Zellifer Ber. Ak. d. Wiss.; Berlin, 1856, p. 

SchmarotzergeoT&chse auf Algen und 474. — Auebbagh (L.), Ueber die Ein- 



114 ESSAY ON CLASSIFICATION. 

Taking the class of Wonns in the widest sense, it 
would thus embrace the Hehninths, Turbellariae, and 
Annulata.^ The embryology of these animals still requires 
careful study, notwithstanding the many extensive in- 
vestigations to which they have been submitted; the 
intestinal Worms especially continue to baffle the zeal of 
naturalists, even now, when the leading features of their 
development are ascertained. The Nematoids undergo 
a very simple development, without alternate generations, 
and, as some are viviparous, their changes can easily be 
traced.^ The Cestoids and Cystici, which were long con- 

zelligkeit dcr Amoeben Zeitsch. f. Reproduction of the Asearis IfyMaXy 

•wbs. Zool., 1855, vol. 7, p. 365.— Philos. Trans. R. Soc., 1852, II, p. 

Ueber Encystirung von Oxytricha 563. — Thompson (Alueh), Ueber die 

Pellionella, Zeitsch. f. wiss. Zool., Samenk&rperchen, die Eier und die 

1854, vol. 5, p. 430. — Oienkowskt, Befruchtung der A»car%$ IfystaXf 

Ueber Cjstenbildung bei Infusorien, Zeitsch. f. wiss. Zool., 1856, vol. 8, 

Zeitsch. f. wiss. Zool., 1855, vol. 6, p. p. 425. — Gbubb (E.), Ueber einige 

301. — LiEBERKiinN (N.), Ueber Pro- Anguillulen und die Entwickelung 

tozoen, Zeit. f. w. Zool., 1856, vol. 8, von Oordius Aquattetu, Wiegm&nn*8 

p. 30. — Bcitrage zur Entwickelungs- Archiv, 1849, i, p. 358. — Sibbou) 

geschichto der Spongillen, Miiller's (C. Tn. E. v.), Ueber die Wanderung 

Arch., 1856, p. 1. — Zur Entwickel- der Qordiaceen, Uebers d. Arb. und 

ungsgeschichto der Spongillen, Nach- Ver. schles. Ges. f. vaterl. Kulture 

trag.. Mailer's Arch., 1856, p. 399.— 1850, p. 38.— Meissner (G.), Beitriig, 

ZusiltzezurEntwickelungsgeschichte zur Anatomic und Physiologie von 

der Spongillen, Miillcr's Arch., 1856, Mermis albicans, Zeitsch. f. wise. 

p. 496. — ^Beitrage zur Anatomic der Zool., 1853, vol. 5, p. 207. — Beobach- 

Spongicn, Miiller's Arch., 1857, p. tungcn iiber das Eindringen der Saa- 

376. — Beitrilgc zur Anatomic der In- menelemente in den Dotter, Zeitsch. 

fusorien, Miiller's Arch.. 1856, p. 20. f. wiss. Zool., 1855, vol. 6, p. 208 und 

— Schneider (A.), Beitrage zur Na- 272. — Beitrage zur Anatomie und 

turgeschichte der Infusorien, Miiller's Physiologie der Gordiaceen, Zeitsch. 

Arch., 1854, p. 191. — Perty (Max.), f. wiss. Zool., 1855, vol. 7, p. 1. — K6i«- 

Zur Kenntniss Kleinster Lcbensfor- liker (A.), Beitrage zur Entwickel- 

men,nachBau,Function, Systematik; ungsgeschichte wirbelloser Thiers, 

Bern, 1852. Miiller's Archiv, 1843, p. 68.— Baqqb 

^ Blanchard (E.), Recherches sur (H.), Dissertatio inaug. de evolutione 

Torganisation des Vers; Paris, 4to.; Stron^t/liauricularisetAscaridisacu* 

part of Voyage en Sicile, by Milne- minatoe; Erlangen, 1841, 4to., fig. — 

Edwards, Do Quatrefages and Blan- Leidt (Jos.), A Flora and Fauna 

chard. within Living Animals, Smithson. 

» Stei.n (F.), Beitrage zur Ent- Contrib., 1853, 4to., fig. — Luscbka 

wickelungsgeschichto der Eingewei- (II.), Zur Naturgeschi^te der Trir 

dewiirmer, Zeitsch. f. wiss. Zool., 1852, china spiralis, Zeitsch. f. wiss. Zool., 

vol. 4, p. 196.— Nelson (II.), On the 1851, vol. 3, p. 69.— BiscnoFF (Th.), 



METAMORPHOSES OP ANIMALS. 115 

sidered as separate orders of Helminths, are now known 
to stand in direct genetic connection with one another, 
the Cystici being only earlier stages of development of 
the Cestoids.^ The Trematods exhibit the most compli- 

XJeber Ei- und Samenbildung und Be- Ibid., 1 853, p. 409. — Ueber die Band- 

fjuchtungheiAsearisMtfstaXyZQitsch, und Blasenwiirmer, nebst einer Ein- 

f. wiss. ZooL, 1855, yol. 6, p. 377. — leitungUber die Entstehung der Ein- 

Wiederlegimg, des von De. Kebbb bei geweide warmer ; Leipzig, 1854, 8to., 

den Najadcn und Da. Nslsoh bei den fig. ; translated in Ann. Sc. Nat., 4e 

Ascariden bebaupteten Eindringens sdr., 1855, vol. 4. — Huxlet (Th. H.), 

der Spennatozoiden in das Ei ; Gies- On the Anatomy and Development 

sen, 1854, 4to., fig. — Bestatigung des of Echinococcus veteritwrum, Ann. 

von Da. Newport bei den Batrachi- and Mag. Nat. Hist., 2nd ser., vol. 

em und Dr. Babet bei den Eanin- ziv, p. 379. — Kuohenmeister (Fb.), 

chen bebaupteten Eindringens der Ueber die Umwandlung der Finnen 

Spermatozoiden in das Ei; Qiessen, {Ci/sticerct) in BtkndwurmQT (Tcsnicg) 

1864, 4to.— Dataine (C), Sur la Prag. Vierteljahrssch. 1852, p. 106. 

maladie du bid, connue sous le nom — Extrait d*une lettre sur des exp6- 

de nielle et sur les Helmintbes qui riences relatives h la transmission 

occasionnent cette maladie, Oompt.- des Vers Intestinaux chcz Tesp^e 

Rend., 1855, voL 41, p. 435. — Clap A- bumaine, Ann. Sc. Nat., 4e sdr., 1855, 

BlEDE (Ed.), Ueber Eibildung und vol. 3. — Cas de transformation de 

Befrucntung bei den Nematoden, Gysticerques cellulaires en Tamia 

Zeitach. f. wiss. ZooL, 1857, vol. 9, p. Solum dans Torganisme bumain, 

106. — Waltbb (G.), Beitr&ge zur Oompt.-Rend., 1854, vol. 39, p. 1180. 

Anatomic und Physiologie von Or^a- — Wage neb (R. G.), Die Entwickel- 

nis omata, Zeitscb. f. w. ZooL, 1856, ung der Gestoden; Bonn, 1855, 1vol. 

vol. 8, p. 163. — Waqneb (Q. R.), 4to.fig. — HelminthologischeBemerk- 

Ueber Dic7ema,K511.,M{iller's Arch., ungen, Zeitscb. f. wiss. ZooL, 1857, 

1857, p. 354. — Libbebkuhn (N.), vol. 9, p. 73. — ^Meissner (G.), Zur 

Beitr&ge zur Anatomic der Ne- Entwickelungsgeschichte und Ana- 

matoden, MCdler's Arch., 1855, p. tomie der Bandwlirmer, Zeitscb. f. 

314. wiss. ZooL, 1854, vol. 5, p. 380. — 

^ Yav Beeedbk (P. J.), Les Hel- Leuckart (R.), Erziehung des Cys- 

minthes, Gestoides, etc.. Bullet. Ac. ticereus faseiolaris aus den Eiem der 

Belg.,voLl6etseq.; M6m.Ac. Brux., Tcenia crassieoUis, Zeitscb. f. wiss. 

1850, vol. 17 et seq.— Sur les Cobuu- ZooL, 1854, vol. 6, p. 139. — Milnb- 

res, 0ompt.-Rend., 1854, vol. 39, p. Edwards, Nouvelles experiences sur 

46. — KdLLiKER (A.), Beitrage, etc., la transmission et les metamorphoses 

q. a., p. 81. — Siebold (G. Th. E. v.), de vers intestinaux, et Valexciennes 

Ueber den Generationswechsel der (A.),Remarques au sujetde la pr^ce- 

Gestoden, etc., Zeitscb. wiss. ZooL, dente communication, Compt.-Rend., 

1850, voL 2, p. 198.— Ueber die Um- 1855, vol. 40, p. 997.— Lettre relative 

wandlungvonBlasenwIirmer in Band- h des nouvelles experiences sur le d^- 

wurmer, Uebers. d. Arb. und Yer. d. veloppement des Yers Intestinaux, 

schles. Ges. f. vaterl. Kultur, 1852, Ann. Sc. Nat., 4e s^r., 1855, voL 3 — 

p. 48.^Ueber die Yerwandlung des Die Blasenbandurmer und ihre Ent- 

CystieercuB pinformis in Tcenia ser^ wickelung, Zeitscb. im Beitrag. zur 

rata, Zeitscb. f. wiss. ZooL, 1853, vol. Kenntniss der Gjsticercus leber, Gi- 

4, p. 400. — Ueber die Yerwandlung eB8en,1856,4to. — Aubbrt(H.), Ueber 

der Echinoooccu»-Brut in Tsenien, Otyporhynchus ptmllus, eine freie 

I 2 



116 



ESSAY ON CLASSIFICATION. 



cated phenomena of alternate generations ; but, as no 
single species has thus far been traced through all the 
successive stages of its transformations, doubts are still 
entertained respecting the genetic connection of many of 
the forms which appear to belong to the same organic 
cycle.^ It is also stiQ questionable, whether the Gregarinas 
and Psorospcrmia are embryonic forms or not, though the 
most recent investigations render it probable that they 
are.^ The development of the Annulata, as they are now 



Oestoden Amme, Zeitsch. f. w. Zool., 
1856, vol. 8, p. 274. 

^ NORDMANN (Al. V.), MicTogTa- 
phische Beitrage zur Naturgeschichte 
der wirbelloscn.Thiere ; Berlin, 1832, 
4to. fig. — Bo JANUS (L.), Zerkarien 
und ihr Fundort, Isis 1818, vol.4, p. 
729. — Enthelminthica Isis 1821, p. 
1G2. — Carus, Beobachtungen iiber 
einen mcrkwiirdigen EiDgeweide- 
wurm, Leucochloridium paradoxum, 
Nov. Act. Ac. Nat. Cur., vol. 17, p. 
85. — SiEBOLD (C. Th. E. v.), Helmin- 
thologische Beitrage, Wiegman's Ar- 
chiv, 1835, vol. 1, p. 45. — Ueber die 
Conjugation des Diplozoon paradox- 
um, etc., Zeitsch. f. wiss., Zool., 1851, 
vol. 3, p. 62. — Gyrodactylus, ein am- 
mendes Wesen, Zeitsch. f. wiss. Zool., 

1849, vol. 1, p. 347. — Steenstrup 
(J.), Generationswechel, etc., q. a. — 
BiLHARZ (Th.), Ein Beitrag zur Hcl- 
minthographia humana, Zeitsch. f. 
wiss. Zool. 1852, vol. 4, p. 59. — 
AuASSiz (L.), Zoological Notes, etc., 
Amer. Journ. Sc. and A. 1852, vol. 
13, p. 425.— Baer (K. E. v.), Bei- 
triige zur Kenntniss der nicdcrcn 
Thicre, Act. Nov. Nat. Cur. li^27, 
vol. 13. — AuBERT (II.), Ueber das 
Wassergefass-system,dieGeschlcchts- 
vcrhiiltnisse, die Eibildung und die 
Entwickclung von Aspidofjaster con- 
chicola, Zeitsch. f. wiss. Zool. 1855, 
vol. 6, p. 349. — Leidy (Jo3.), De- 
scription of two new iSpecies of Di- 
8toma,with the partial History of one 
of them, Jour. Ac. Nat. Sc. Phil. 

1850, vol. 1, p. 301, fig. — Lav alette 



(A. de), Symbolae ad Trematodom 
evolutionis historiam. Diss, inaug. ; 
Berolini, 1866, 4to.— Filippi (Th. 
de), M6inoire pour Mrvir k Thistoire 
g6n6tique des Trematodes, Ann. 8a 
Nat., 4e. s^r. 1854, vol. 2. — Quelques 
nouvelles observations sur les larres 
des Trematodes, Ann. Sc. Nat., 4e 

S6r., 1856, vol. 6. CLAPABiDB (£i>.). 

Ueber die Ealkkdrperchen der Tre- 
matoden und die Qattung Tetraco- 
tyle, Zeitsch. f. wiss. Zool. 1867, toL 
9, p. 99. 

* MUlleb (J.), Ueber eine eigen- 
thumliche krankhafte parasitische 
Bildung, etc., Midler's Archiv, 1841, 
p. 477. — Ueber parasitische Bildun- 
gen, etc., Miiller*8 Archiv, 1842, p. 
193. — DuPOUR (L.), Note sur la Gre- 
garine, etc., Ann. Sc. Nat.j 1828, toI. 
13, p. 366, fig.— Ibid., 2de s^r., 1837, 
vol. 7, p. 10.— SiEBOLD (C. Th. E. t.), 
Beitrage, etc., q. a. ; p. 66-71. — Ham- 
MERBCUMiDT (C. Ed.), Helmintholo- 
gische Beitrilge, Isis 1838, p. 351. — 
KoLLiKER (A.), Die Lehre von der 
thierischen Zelle, etc., Zeitsch. wiss. 
Botanik. 1845, vol. i., p. 46, and p. 
97. — Beitrage zur Kenntniss niederer 
Thicre, Zeitsch. f. wiss. Zool. 1848, 
vol. i. p. 1. — Henle (J.), Ueber die 
Oattung Grcgarina, Midler's Archiv, 
1845, p. 369. — Frantzids (Al. t.), 
Obscrvationes qucedam de Gregarinis, 
Berolini, 1846.— Stein (F.), Ueber 
die Natur der Qrcgarincn, Mailer's 
Archiv, 1848, p. 182, fig.— BarcH 
(C), Einige Bemerkungen uber die 
Qregarincn, Zeitsch. f. wiss. Zool. 



METAMORPHOSES OF ANIMALS. 117 

circumscribed, exhibits great variety '} some resemble 

more the Nematoids, in their metamorphoses, while others, 

1850, vol. 2, p. 110. — Letdio (F.) des Ann61ide8, Ann. 8c. Nat. 3e 86r., 

Ueber Psorospermicn und Grega- 1848, vol. 10, p. 153, fig. — Besor (E.), 

rinen, Muller's Archiv, 1851, p. 221. On the Embryology, etc., q. a. — Leidy 

— Leidt (Jos.), On the Organization (Jos.), Descriptions of some Ame- 

of the Genus Gregarina, Trans. Amer. rican Annelida abranchia, Joum. 

Phil. Soc. 1851, vol. 10, p. 233.— Ac. Nat. 8c. Phil. 1850, vol. 2, 

Some Observations on Nematoidea p. 43, fig. (LumbriciUus con- 

imperfecta and Descriptions of three tained seventl thousand large Leuco- 

parasitic Infusoria, Trans. Amer. phrys. The case related here by Leidy 

PhiL Soc. 1851, vol. 10, p. 241. — seems to me to indicate rather the 

LiEBERKiiHN (N.), Uebcr die Psoro- hatching of Opalinas from the eggs 

sperm ien, Miiller's Archiv, 1854, p. Lumbricillus, than the presence of 

1 . — Schmidt (A.),Beitr&g zur Kennt- parasitic Leucophrys.) — Schultzb 

niss der Gregarinen, Abh. Leuk. (M.) Ueber die Fortpflanzung durch 

Gesell. 1854. — Ueber parasitische Theilung bei Nats prohoscidea, Wieg- 

Schlauche auf einigen Insektenlar- mann's Archiv, 1849, I., p. 293 ; id. 

ven, Muller's Archiv, 1856, p. 494. — 1852, I., p. 3. — Zoologische Skizzen 

Comp. also note 2, p. 113. ( Arenicota pUcat.) Zeitsch. f. wiss, 

> Weber (E. H.), Ueber die Ent- Zool. 1852, vol. 4, p. 192.~Abh. Nat. 

wickelung von Hirudo medicinalis, Gesellsch. in Halle, vol. 4. — Buscn 

Meckel's Archiv, 1828, p. 366, fig.— (W.), Beob. iiber Anat. und Entw. q. 

FiLiPPi (FiL de), Sopra Tanatomia e a. (p. 55.) — MiiLLEB (M.), Observa- 

lo sviluppo delle Clepsine, Pavia, tiones anatomicsD de Vermibus qui- 

1839, 8vo. fig. — Loves ( J.), Beobacht- busdam maritimis, Berolini, 1852, 

ungen uber die Metamorphose einer 4to. ; Miiller*s Archiv, 1852, p. 323. 

Annelide, K. Vet. Ac. Handl. 1840, — Ueber die weitere Ent wickelung 

Wiegman's Archiv, 1842, vol. i., p. von Mesotrocha sexocidata, Miiller's 

302. — Oersted (A. 8.), Ueber die Archiv, 1855, p. 1.- Ueber Sacco- 

Ent wickelung der Jungen bei einer nereis helffolanaica, Miiller's Archie, 

Annelide, etc., Wiegmann's Archiv, 1855, p. 13. — Krohn (A.), Ueber die 




Mbhob (A.), Zur Roth-Wurmer Gat- Autolytue prolifer Gr., Miiller's Ar- 

tung Euaxes, Wiegmann's Archiv, chiv, 1855, p. 489.— Leuckart (R.), 

1845, vol. i., p. 24.— Grubb (A. E.), Ueber die ungeschlechtliohe Ver- 

Zur Anatomic und Entwickelung der mehrung bei Nais proboecidea, Weig- 

Kiemenwurmer, K5nigsberg, 1838, man's Archiv, 1851, p. 134.— Ueber 

4to. Actinien, Echinodermen und die Jugendzustilnde einiger Anneli- 

Wiirmer, etc., EGnigsberg, 1843, den, Wiegman's Archiv, 1855, I., p. 

4to. ^g. — Untersuchungen iiber die 63. — Quatrefages (A. de), M6- 

Entwickelung der Clepsine, Dorpat, moiresur lagen6ratioualtemanto des 

1844.— Edwards (H. Milne-), Ob- Syllis, Ann. 8c. Nat. 4e ser., 1854, 

eervations sur le d6veloppemcnt des vol. 2. — Note sur le developpcmcnt 

Ann^lides, Ann. Sc.Nat. 3e ser. 1845, des Spermatozoides chez la Torrea 

vol. 3, p. 145.— Koch (II.), Einige vitrea, Ann. 8c. Nat. 4e ser., 1854, 

Worte zur Entwickclungsgeschichte vol.2. — IIering (Ew.),Zur Anatomie 

der Eunice, mit eincm Nach worte von und Physiologic der Generations- 

KSlliker, N. Denksch. Schw. GcselL, organe des Regenswurms, Zeitsch. f. 

1847, vol. 8, 4to. fig.— Quatrefages wiss. Zool. 1856, vol. 8, p. 400.— 

(A. de), Memoire sur TEmbryogdnie Gosse (Pu. H.), Tenby, q. a. — 



118 ESSAY ON CLASSIFICATION. 

the Leeches for instance, approximate more to the type of 
the Trematods. The Sipmiculoids are no doubt more 
closely related to the Annnlata than to the Holothurioids.^ 
The class of Crustacea, on the contrary, may be con- 
sidered as one of the best known, as far as its zoological 
characters and embryonic growth are concerned, the only 
point still questioned being the relationship of the Ro- 
tifera.^ In their mode of development the Lemseans, the 
Entomostraca proper, and the Cirripeds, agree as closely 
with one another as they differ from the higher Crustacea. 
This conformity^ is the more interesting, as the low posi- 

UDEKEM(J.D'),NouyeIlec]a88ificatioQ 1852, p. 12. — WiLLiAMSOif (W. C), 

des Ann61ides S6tig^nes abranches, On the AxiB.iomj of If dtcertarin^ens. 

BuU. Ac; Brux. 1855, IF., p. 533. Quart. Micr. Joum. 1852, p. 1. — 

^ Peters (W.), Ueber die Fort- BuRMBi8TEB(H.),NocheuiiffeWorte 

pflanzungsorgane des Sipunculus, uber die systematische Stelmng der 

Miiller's Archiy, 1850, p. 382.— MuL- Raderthiere, Zeit. f. w. Zool. 1856, 

LER (M.), Ueber eine den Sipuncu- vol. 8, p. 152. — GossB (Th. H^, (hi 

liden verwandte Wurmlarve, Miiller's the Structure, FuQctionB and Efomo- 

Archiv, 1850, p. 439. — Krohn (A.), logies of the Manducatory organs in 

Ueber die Larve des Sij>unctUiu the class Rotifera, Phil. Trans. Roj. 

nudu8, etc., Miiller's Archiv, 1851, Soc. ; London, 1856, II., p. 419. 

p. 368. — ScHMARDA (L.), Zur Natur- ' tfuRiNE (L.), Histoire des Mon- 

ge8chichtederAdria(i?on^/iai;i>i(/i«) odes qui se trouyent auz environs 

Denksch. Wien. Akad. 1852, vol. 4, de Geneve ; Paris, 1806, 4to. Bg. — 

p. 117, fig. Milne-Edwards (H.), in Cuvicr, 

* Ehrenberq (0. J.), Die Infu- R^gn.An.edit. illustr. q.a. Omstao^s; 

sionsthierchen, etc., q. a. — Dalrtm- represents young Limulus. — Zai>- 

PLE (J.), Description of an Infusory dacu (E. Q.), De Apodii cancr^or^ 

Animalcule allied to the Genus Not- mis Anatomia et Historia evolutionis 

omma, Philos. Trans. 1844, II., p. Bonna), 1841, 4to. fig. — Nordmaitv 

331. — Nahoeli (H.), Beitrage zur (Al. v.), Microgr. Beitr. q. a. — Let- 

Entwickelungsgeschichte der Rader- dio (Fr.), Ueber Argulm foliaceu9^ 

thiere. Diss, inaug. Zurich, 1852, 8vo. ein Beitrag zur Anatomie, Uistologie 

fig. — liETDia (Fr.^, Ueber den Bau und Entwickelungsgeschichte dieses 

und die sjstematische Stcllung der Thieres, Zeitsch. f. wiss. Zool. 1850, 

Raderthiere, Zeitsch. f. wiss. Zool. vol. 2, p. 323. — Veh&t Artemia $alina 

1854, vol. 6, p. 1. — Zur Anatomie \m^ Branchipus stagnalUy Zeitsch,, i, 

und Entwickelungsgeschichte der Za- wiss. Zool. 1851, vol. 3, p. 280. — Yak- 

cinularia 80ci<iUs, Zeitsch. f. wiss. Beneden (P. J.), Recherches but 

Zool. 1852, vol. 3, p. 452. — Ueber quelques Crustac^s inf6riears Ann. 

Hi/datina Scata, Miiller's Arch. 1857, 8c. Nat. 3e 86r. 1851, vol. 16, p. 71.— 

p. 404. — OoHN (F.), Ueber die Fort- M6moire sur le d6veloppoment et 

pflanzung der Raderthiere, Zeitsch. Torganisation des Nicotho^, Ann. 

f. wiss. Zool., 1855, vol. 7, p. 431.— Sc. Nat. 3c 86r. 1850, vol. 13, p. 354. 

Huxley (Tn. II.), Lacinularia soci- Geqerbaur (C), Ueber die Bnt- 

alis, Trans. M. Soc., Micr. Joum. wickclung der Sagitta, Abh. d. na- 



METAMORPHOSES OF ANIMALS. 119 

tion which the Entomostraca hold in the class of Crustacea 
agrees strikingly with their early appearance in geological 
times ; while the form of the adult Cirripeds^ and that of 
the Lemaeans would hardly lead one to suspect their near 
relationship, which has, indeed, been entirely overlooked, 
until the study of their metamorphoses showed that their 
true position is among the Crustacea. In the development 
of the higher Crustacea,^ their superior rank is plainly ex- 
turf. Qes. zu Halle, 1856, 4to. vol. Oirripedia, with Figures of all the 
4, p. 1. — Kbohn (A.), Anatomisch- Speciesi London, 1851, 2 vols. Syo. 
phjsiologische Beobachtungen tiber (Eay Society). — Bate (Spenge), On 
die Sagitta Copwictata ; Hamburgh, the Development of the Oirripedia, 
1844. — Kachtragliche Bemerkung- Ann. and Mag. Nat. Hist. 2d ser. vol. 8, 
en, etc., Moller^s Arch., 1853, p. p. 324. — Gossb (Th. H.), Tenby, q. a. 
266. — WiLMB, Obsenrationes de Sa- ■ Rathke (H.), Untersuchungen 
gitta mare Germanicum circa insu- iiber die Bildung und Entwickelung 
lam Helgoland incolento; Berolini, des Flusskrebses, Leipzig, 1829, 1 
1846. — HuxLET (Th. H), Observa- vol. fol. fig. — Beitra^e zur Fauna 
tions on the genus Sagitta. Rep. Korvegica, Act., Nov. Ac. Leop. Oaes. 
Brit. Ass. for 1851, p. 77. — Darwiv vol.20. — Beitrage zur vergleichenden 
(Gh.), Observations on the Structure Anatomie and Physiologic, Reisebe- 
and Propagation of the genus Sa- merkungen aus Skandlnavien, Dant- 
gitta. An. Mag. Nat. Hist. 1844, vol. zig, 1842, 4to. — Zur Morphologic, 
13, p. 1. — BuBCH (W.), .Beobacht- Reisebemerkungen aus Taurien, Riga 
ungen, q. a. — Babbande (J.), Syst. und Leipzig, 1837, 4to. fig. — Uel^r 
sil. q. a. ; contains the first observa- die Entwickelung der Decapoden, 
tions upon the transformations of Miiller's Archiv, 1836, p. 187, Wieg- 
Trilobites. man's Archiv, 1840, I., p. 241. — 

^ Thompson (W. Y.), ZoSlogical Beobachtungen und Betrachtungen 
Researches and Illustrations, or Na- iiber die Entwickelung der Mysia 
tural History of nondescript or im- vulgaris, Wiegman's Archiv, 1839, 
perfectly Icnown Animals, Oork, p. 195, fig. — Erdl (M. P.), Ent- 
1828-34, 8vo., ^g, — Bubmeistbb wickelung des Hummereies, Miin- 
(H.), Beitr&ge zur Naturgeschichte chen, 1843, 4to. fig. — Edwaeds (H. 
der Ranken&sser ( Oirripedia), Ber- Milxb-), sur la g6n6ration des Orus- 
lin, 1834, 1 vol. 4to. fig.— Cold- tac6s, Ann. 8c. Nat. 1829.— Obser- 
STBEAM (J.) Article Oirrhopoda, in vations sur les changements de forme 
Todd*8 (>yclop8Bdia, London, 1 836, que divers Orustacis 6prouvent dans 
vol. 1, p. 683. — GooDSiR (H. D. S.), le jeune &ge, Ann. Sc. Nat. 2de s6r. 
On the Sexes, Organs of Reproduc- vol. 3, p. 321. — Aoassiz (L.), Zodlo- 
tion, and Development of Cirripeds, gical Notes, etc., Am. Jour. Sc. and 
Ed. N. Phil. J. 1843, No. 35, p. 88, A., 1852, p. 426.— Recent Researches, 
fig. — Mabtin St. Angb (G. J.), M6- etc.. Am. Jour. Sc. and A., 1852, vol. 
moire sur Porganisation des Cirri- 16, p. 136. — Bate (8p.), On the Bri- 
pddes et sur leurs rapports naturels tish Edriophthalma, Report Brit, 
avec les animauz articul6s, Ann. Sc. Ass., 1855, p. 18. — Lebeboullet, 
Nat. 1831, p. 366, ^g. — Dabwin R6sum6, etc., Ann. Sc. Nat. 4e s6r. 
(Ch.), a Monograph of the sub-class 1854, vol.1 .— Gosse (T. H.), Tenby,q.a. 



120 ESSAY ON CLASSIFICATION. 

hibited ; and few types show more directly a resemblance, 
in their early stages of growth, to the lower members of 
their class, than the Brachyura. 

In the class of Insects, I include Myriapods, Arachnoids, 
and the true Insects, as, according to the views expressed 
hereafter, these natural groups constitute only diflferent 
degrees of compUcation of the same combination of or- 
ganic systems, and must therefore be considered as natural 
orders of one and the same class. This class, though very 
extensively studied in a zoological and anatomical point 
of view, and as far as the habits of its representatives are 
concerned, still, however, requires much patient work, as 
the early embryonic development of these animals has 
been much less studied than their later transformations.^ 
The type of the Arachnoids embraces two groups, the 

^ Hekold (M.), Entwickelungs- organe der Eafer, Berlin, 1847, foL 

geschichte der Schmetterlinge, etc., ^f^. — Siebold (C. Th. £. v.), Ueber 

Kassel und Marburg, 1815, 4to. fig. die Fortpflanzung yonP8Yche,Zeit8ch. 

— Disquisitiones de animalium Ycrte- f. wiss. Zool., 1848, vol. 1, p. 93.— 

bris carcntium in ovo format ione, Wahre Parthenogenesis bei Schmet- 

Frankfurt a. M., 1835, fol. fig. — terlingen und Bienen, £in Beitrag 

Rathke (II.), Entwickelungsge- zur Fortpfianzungsgeschichte der 

schichte der Blatta germanica^ Thiere, Leipzig, 1856, Svo. ; see also 

Meckel's Archiv, 1832.— Zur Ent- Ann. 8c. Nat. 4e 86r. 1856, voL 6. 

wickclungsgeschichte der Maul- — Leydio (Fb.), Einige Bemerk- 

wurfsgrille ( Gryllotalpa vulgaris )y ungen iiber die Entwickelung der 

Miiller's Archiv, 1844, p. 27. — K6l- Blattlause, Zeitsch. f. wiss. Zool., 

LiKER (A.), Obscrvationes de prima 1850, yoI. 2, p. 62. — Meyeb (H.), 

Insectorum Genesi, Turici, 1842, 4to. Ueber die Entwickelung des Fett- 

fig. — Zadpach (G.), Die Entwickel- k6rpers, der Tracheen und der keim- 

ung des Phryganiden Eics, Berlin, bereitendenGeschlechtstheile boi den 

1 vol. 4to. 1854. — Leuckardt (R.), Lepidopteren, Zeitsch. f. wiss. Zool., 

Ueber dieMicropyle und den feinern 1849, vol. 1. — Burnett (W. I.), Re- 

Bau der Schalenhaut bei den Insek- searches on the Development of vivi- 

teneiern, Miiller's Arch., 1855, p. 90. parous Aphides, Amer. Jour. ScL and 

— Newport (Geo.), On the Organs Arts, 1854, vol. 17, p. 62 and 261. — 

of Reproduction and the Develop- Fabre, Recherches sur Tanatomie 

ment of Myriapoda, Phil. Trans. R. des organes reproducteurs et sur le 

Soc. 1842, II., p. 99. — On the Ana- development des Mjriapodes, Ann. 

tomy and Development of Meloe, Sc. Nat. 4e s6r. 1855, vol. 3. — Etude 

Ann. and Mag. Nat. Hist., 1848, vol. sur Tinstinct et les metamorphoses 

1, p. 377, vol. 2, p. 145. — Stein des Sph6gien8, Ann. Sc. Nat. 4e 86r. 

(Fr), Vergleichende Anatomic und 1856, vol. 6. — Saussure (Hbnrt 

Physiologic der Insecteu, l8te Mo- de^, Nouvelles considerations sur la 

nogr., Die weiblichcn Geschlcchts- nidification des gu5pes, Ann. Sc. Nat. 



METAMORPHOSES OF ANIMALS. 121 

Acari and the Arachnoids proper, corresponding respec- 
tively in this class to the Entomostraca and the higher 
Crustacea. The embryo of the Acari resembles somewhat 
that of the Entomostraca, whilst that of the true Spiders^ 
recalls the metamorphosis of the higher Crustacea. On 
the ground of the similarity of their young, some animals, 
formerly referred to the class of Worms, ^ are now con- 
sidered as Arachnoids ; but the limits between the aquatic 
Mites and the Pycnogonums are not yet quite defined. 

In the branch of Vertebrata, all classes have been ex- 
tensively studied, and, as far as the principal types are 
concerned, the leading features of their development are 
satisfactorily known. Much, however, remains to be done 

4e ser. 1855, vol. 3. — Semper (C), Spinoeneies, Zeitsch. f. wiss. Zool., 
Ueber die Bildung der Fliigel, Schup- 1850, toI. 2, p. 97. — Dujardin (F.), 
pen und Haare bei den Lepidopteren, Mtooire snr des Acariens sans 
Zeitsch. f. wiss. Zoo!., 1856, vol. 8, bouches, dont on a fait le genre 
p. 326. — Lbuckart (R.), Die Fort- Hypopus et qui sont le premier kge 
pflanzuug und Entwickelung der des Gamaases, Ann. So. Nat. 1849, 
Pupiparen, Abh. d. naturf. Ges. zu vol. 12, p. 243 et 259. — Blanohard 
Halle, 1858, vol. 4, p. 145. — As far (E), Observations relatives h, la g6- 
as the metamorphoses of Insects, n6ration des Arachnides, Oomptes- 
after the ecljsis of the larva, are Rcndus, 1857, vol. 44, p. 741. — 
concerned, I must refer to the Scheuter (A.), Einiges iiber Mil- 
works of Reaumur and Roesel, ben, Arch. f. Naturg. 1857, 1., p. 104. 
already quoted, and to almost every * Kaufmann (Jos.), Ueber die 
modem book upon Entomology. The Entwickelung und zoologische Stel- 
metamorphoses of North American lung der Tardigraden, Zeitsch. f. 
Insects are minutely described in wiss. Zool. 1851, vol. 3, p. 220. — 
Harris's Report, q. a., p. 85. Van Beneden (P. J.), Recherches 
^ Herold (M.), De generatione sur Torganisation et le develop- 
Aranearum in ovo, Marburgi, 1824, pement des Linguatules (Penta- 
fol. ^g. — Ratbkb (H.), Ueber die «^owki^,M6m. Acad. Brux., vol. 15, 1., 
Entwickelung des Scorpions ; Zur p. 188. — Schubert (T. D.), Ueber 
Morphologie, q. a. — Van Beneden Entwickelung von Pentastomum 
(P. «f.), Recherches sur THistoire na- tcenioides, Zeitsch. f. wiss. Zool. 
turelle et le d^veloppement de r^^or 1852, vol. 2, p. 117. — Wilson 
ypsilophora, M6m. Ac. Brux., 1850, (E.), Researches into the Structure 
vol. 24, p. 444. — WiTTiCH (W. H. v.), and Development of a newly dis- 
Observationes qusedam de aranearum covered Parasitic Animalcule of the 
ex ovo evolutione. Diss, inaug. Halis. Human Skin, Phil. Trans. R. Soc. 
Sax., 1845.— Die Entstehung des 1844, p. 305.— Semper (C), Zur 
Arachnideneies im Eierstock, Mul- Anatomic und Entwickelungsge- 
ler's Arch., 1849, p. 113.— Carus schichte der Gattung Myzostoma, 
(J. V.),1Jebcr die Entwickelung des Zeitsch. f. wiss. Zool., 1857,vol. 9, p. 48. 



1 22 ESSAY ON CLASSIFICATION. 

in ascertaining the minor modifications characteristic of the 
different families. It may even be, that further investi- 
gations will greatly modify the general classification of 
the whole brancL The class of Fishes^ may require sub- 

^ FoBCHHAMMER, (G.,) De Blennii &ber die Verachiedenheiten unterden 

yipipari formatione et erolutione ob- Haifischen und Rochen in der £nt- 

servationes, Kiel, 1819, 4to. — Pbb- wickelung des Eies ; Berlin, 1842, fol. 

YOST, (J. L.,) De la ff6n6ration chez fig. — Leuokart, (F. 8.,) Untennch- 

Ic Sichot {Cottus Oomo)f M^m. Soc. ungen uber die &u8sem Kiemen der 

Phys. et Hist. Nat. Geneve, vol. 4, Embryonen von Rochen and Haien ; 

1828, 4to.— Rathkb, (H.,) Beitrage Stuttgardt, 1836, 8to. figw— Leti>ig, 

zur Geschichte der Thierwelt, Halle, (Fr.,) Beitrage sur microacopischen 

1820-27, 4 Tols. 4to. fig. — Abhand- Anatomie und Eniwickelungage- 

lungen zur Bildungs- und Entwickel- schichte der Rochen und Haie ; Leip- 

ungsgcschichte des Menschen und zig, 1852, 1 vol. 8to. fig. — Oarus, 

der Thiere ; Leipzig, 1832-33, 2 yols. (G. G.,) Erl&uterungstafeln, etc^ No. 

4to. fig. — Ueber das Ei einiger Lacbs- 3 ; Leipzig, 1831, fol. fig. — Shaw, (J.,) 

arten. Mockers Archiv, 1832, p. 392, Account of some Experiments and 

— Baer, (K. E. y.,) Untersuch ungen Observations on the Parr, etc., Edinb. 

uber die Entwickelungsgeschichte der New PhU. Joum., vol. 21, p. 99. — 

Fische ; Leipzig, 1835, 4to. — ^Also On the Development and Growth of 

Entw. der Thiere, q. a., vol. 2. — the Fry of the Salmon, etc^ Ibid. vol. 

Davt, (J.,) On the Development of 24, p. 165 ; also Ann. Nat. Hist., I. p. 

the Torpedo, Philos. Trans. R. Soc., 75, and IV. p. 352.— Yarr«Uu( W.,) 

1 834. — Some observations on the ova Growth of the Salmon in Fresh Water, 

of the Salmon, in relation to the dis- Ann. and Mag. Nat. Hist., IV. p. 334. 

tribution of species. Trans. Roy. Soc. ; — Duvernoy, (G. L.,) Observations 

London, 1856, I, p. 21. — Filippi, pour servir k la connaissance du d6- 

(FiL. DE,) Memoria sullo sviluppo del veloppement de la P6cilie de Surinam, 

Oobiiis fluviatilisy Annal. Medic, Mi- Ann. Sc. Nat., 1844, 3e s6r. I. p. 313, 

lane, 1841, 8vo. fig. — RuscoNi, (M.,) fig. — Coste, (P.,) Histoire gen^rale 

Sopra la fecondationo artificialo nci et particuli^re du d6veloppement des 

pesci, Giorn. dclle Sc. Med.-chir., corps organist ; Paris, 1847-53, 4to , 

Pavia, vol. 9 ; transl. in Miiller's Ar- Atl. fol., 2d Fasc., Epinoche.---QuA- 

chiv, 1840, p. 185. — Lettre sur les trefaqes, (Arm. db,) Memoire sur 

changemcnts quo les ooufs de Pois- les Embryons des Syngnathes, Ann. 

sons eprouvent avant quails aient pris Sc. Nat., 2de s4r. vol. 18, p. 193, fig. 

la forme d'embryon, Ann. Sc. Nat., — Sur le d6veloppement embryonaire 

2dc s6r. vol. 5 ; transl. Mag. Zool. and des Blenuies, etc., Comptes-Rendus, 

Bot., I., p. 586. — Agassiz, (L.,) His- vol. 17, p. 320. — Valehcibvnbs, (A.,) 

toire naturelle des Poissons d'eau AnaUeps in Cuvier et Valkvci- 

douce de TEurope centrale, vol. 1. EN^fss, Uistoire naturelle des Pois- 

Embryologie des Salmones, par C. sons ; Paris, 1846, vol. 18, p. 245. — 

VooT, Neuch&tel, 1842, 8vo. atlas fol. Wvman, (J.,) Observations on the 

These investigations were made under Development of AnabUps Oronovii, 

my direction and supervision. The Journ. Bost. Nat. Hist., 1854, vol. 6, 

reader may compare the preface to fig. — On some peculiar modes of ges- 

this work with a letter published in tation observed in certain animals of 

Zeitsch. f. wissensch. Zoologie, 1855, Guiana, Proc. Bost. Nat. Hist., 1857. 

vol. 7, p. 328. — MiiLLER, (J.,) Ueber — AaAR8iz,(L.,)Extraordinai7 Fishes 

den glattcn Hai des Aristotelcs, und from California, constituting a new 



METAMORPHOSES OF ANIMALS. 123 

division, since the development of the Plagiostoms diflFers 
greatly from that of the ordinary fishes. As it now stands 
in our systems, the class of Fishes is certainly the most 
heterogeneous among Vertebrata. The disagreement of 
authors, as to the limits and respective value of its orders 
and families, may be partly owing to the unnatural cir- 
cumscription of the class itself^ As to the Reptiles, it is 

family, Amer. Joum. Sc. and A., 1853, Mag. Nat. Hist., 2d ser., 1856, vol. 1 7, 

vol. 16, p. 380. — Embryology of Zo- p. 443. — Mullee, (A.,) Ueber die 

^Atu5^mmcantM,Proc.Am.Ac.l855. Eniwickelung der Neunaugen, Miil- 

— Lbbbboullet, (A,) Recherches sur ler's Arch., 1856, p. 303 ; translated 

I'Anatomie des organes genitauz des in Ann. Sc. Nat., 4e s^r., 1856, vol. 5. 

animaux Vert4br&, N. Act. Ac. Nat. The unexpected facts mentioned here. 

Our., Yol. 23, p. 1. — R6sum6 d*un render it highly probable, that Am- 

travail d*embryologie compar6e but phioxus is the immature state of 

le d^Teloppement du Brochet, de la some marine Gyclostom. — DuFOSgH, 

Perche et de rEcrevisse, Ann. Sc. De Thermaphrodisme chez certains 

Nat., 4e s^r., 1854, yol. 1. — Aubebt, Yert^br^s, Ann. Sc. Nat., 4e sdr., 1856, 

(H.,) Beitrage zur Entwickelungs- vol. 5. 

geschichte der Fisohe, Zeitsch. f. wiss. ^ The peculiarities of the deyelop- 

Zool., 1853, Yol. 5, p. 94 ; 1855, vol. ment of the Plagiostoms consist not 

7. — Yalbrtin, (G.,) Zur Entwickel- so much in the few large eggs they 

ungsgeschichte der Fische, Zeitsch. produce, and the more intimate con- 

f. wiss. Zool., 1850, vol. 2, p. 267. — nection which the embryo of some of 

Lbucsjlbt, (R.,) Ueber die allmahlige them assumes with the parent, as in 

Bildung der Kdrpergestalt bei den the development itself, which, not- 

Bochen, Zeitsch. f. wiss. Zool., 1850, withstanding the absence of an 

vol. S, p. 258. — Habckbl, (E.,) Ueber amnios and an allantois, closely 

die Eier der Scomberesoces, Muller*s resembles, in its early stages, that of 

Arch., 1855, p. 23. — Retzius, (A.,) the Reptiles proper and of the Birds, 

Ueber den grossen Fetttropfen in den especially in the formation of the 

Eiem der Fische, Muller's Arch., vascular system, the presence of a 

1855, p. 34. — BuucH, (C.,) Ueber die nnus terminalis, etc. Again, besides 

MicTopyle der Fische, Zeitsch. f. wiss. the more obvious anatomical differ* 

Zool., 1855, vol. 7, p. 172. — Reichbbt, ences existing between the PJa- 

(K.B.,)UeberdieMicropylederFi8ch- giostoms and the bony Fishes, it 

eier, etc., Muller's Arch., 1856, p. 83. should be remembered, that, as in 

— Ueber die Mdller-WolfTschen Kor- the higher Yertebrata, the ovary is 

perbeiFischembryonen, etc.,Muller'8 separated from the oviducts in the 

Arch., 1856, p. 125. — DerNahrungs- Sharks and Skates, and the eggs are 

dotter des Dechteies eino contractile taken up by a wide fallopian tube. 

Substanz, MuUer's Arch., 1857, p. 46. That the Plagiostoms can hardly be 

— DowLBB, (B.,) Discovenr of a Yivi- considered simply as an order in the 

parous Fish in Louisiana, Amer. Jour, class of Fishes might even be in- 

8c. and Arts, 1855, vol. 19, p. 133, ferred ^m the fact, that they do 

with Remarks by L. Aoassiz, p. 136. not constitute a natural series with 

— ScHULTZE, (M.,) Note sur le d6- the other Fishes. I would, there- 

veloppement des P6tromy zous, Oomp- fore, propose the name of Sel a- 

tes-RenduB, 1856, p. 336 ; Ann. and cbiams for adbtinct class, emWacing 



124 ESSAY ON CLASSIFICATION. 

alreacly certain that the Amphibia and Reptiles proper, so 
long united as one class, constitute two distinct classes. 
In the main, the development of the true Reptiles^ agrees 

very closely with that of the Birds, while the Amphibians^ 

the Sharks, Skates, and Chimaeras. Ann. 8c. Nat. 3e 86r I. p. 193, fig. — 

Recent investigations upon the Cy- Ruscoifi (M.), D6veloppement de la 

clostoms show them also to differ Qrenouille commune, depuis le mo- 

widely from the Fishes proper, and ment de sa naissance jusquli son 

they too ought to be separated as 6tat parfait, Milan, 1828, 4to. ^g. — 

a distinct class, for which the name Amours des Salamandres aquatiques 

of Mtzoxtes may be most appro- et d6veloppement du T6tanl de ces 

priate. Salamandres, etc., Milan, 1822, 4to. 

* VoLKMANN (Q. W.), De Colttbris ^g, — Baeb (K. E. v.), Die Metamor- 

natricis Qeneratione, Lipsise, 1834, phose des Eies der Batrachier vor 

4to. — Rathke (H.), Entwickel- der Erscheinung des Embryo, etc., 

ungsgeschichte der Natter (Coluber Muller*s Archiy, 1834, p. 481. — Ent- 

natrix), K6nigsberg, 1839, 4to. fig. wickelungsgeschichte, etc., toL 2, 

— Untersuchungen iiber die Aorten- p. 280. — -Rbichbbt (K. B.), Das Ent- 

wurfeln, Denksch. Ak. Wiss. Wien, wickelungsleben imWirbeithierreich, 

1857, vol. 13.— Wbinland (D.), Berlin, 1840, 4to. fig.— Vergleich- 

Ueber den Eizahn der Ringelmatter, ende Entwickelungsgeschicbte det 

Wurt. Nat. Hist. Jahreshefte, 1855. Kopfes der nackten Amphibien, etc., 

— TiEDEMANN (F.), Ueber das Ei und K6nigsberg, 1838, 4to. fig. — Ueber 

den Fcetus der Schildkrdte, Heidel- den Furchungsprocess der Batra- 

berg, 1828, 4to. ^g. — Baeb (K. E. v.), chier-Eier, Muller*s Archly, 1841, p. 

Bcitrage zur Entwickelungsge- 523. — VooT (C), Untersuchungen 

schichte der Schildkrdten, Miiller*s iiber die En t wickelungsgeschichte 

Archiv, 1834, p. 544. — Rathke (U.), der Qeburtshelferkr5te, Solothuro, 

Ueber die Entwickelung der Schila- 1841, 4to. fig. — Quelques observa- 

kroten, Braunschweig, 1848, 4to. fig. tions sur Tembryologie des Batra- 

' Rosel v. Rosenhop (A. J.), His- ciens, Ann. 8c. N., 3e s^r. vol. 2, p. 

toria naturalis Ranarum nostratium, 45. — Remak (R.), Untersuchungen 

etc., Norimb., 1758, fol. fig. — Funk uber die Entwickelung der Wirbel- 

(A. F.), De Salamandrce Urrestris thiere, Berlin, 1855, fol. — Newpobt 

vita, cvolutione, formatione, etc., (G.), On the Impregnation of the 

Berlin, 1826, fol. fig. — Rathke (H.), Ovum in the Amphibia, Phiios. 

Diss, de Salamandrarum corporibus Trans. R. Soc. 1851, 1., p. 169; 1853, 

adiposis eorumque cvolutione, Berol. II., p. 233; 1854, II., p. 229. — WiT- 

1818. — Ueber die Entstchung und tich (W. II. v.), Beitrage zur mor- 

Entwickelung der Geschlechtstheile phologischen und histologiBchen 

bei den Uroaclen, N. Schr. Dantz. Entwickelung der Ham- und Ge- 

Naturf. Ges., 1820. — Steinheim (L.), schlechtswerkzeugo der nackten Am- 

Dic Entwickelung der FrQsche, Uam- phibien, Zeitsch. f. wiss. Zoo!., 1852, 

burg, 1820, 8vo. fig. — Hasselt (J. vol. 4, p. 125. — Wei5LA5D (D.), 

CoNR., van). Dissert, exhibens Ob- Ueber den Beutelfrosch, Muller^s 

servationcs do metamorphosi qua- Archiv, 1854, p. 449. — Wtman (J.), 

rumdam partium Raiicc temporaruB, Observations on Pij>a Americana^ 

Gottinga), 1820, 8vo. — Frevost Am. Jour. So. and Arts, 2d ser 1854, 

(J. L.), ct Lebert, M6moire sur la vol. 17, p. 309. — Thomas (A.), Note 

formation des organcs do la circula- sur la generation duPelodyteponctu6, 

tion et du Sang dans Ics Batracicns, Ann. Sc. Nat. 4e scr., vol. U 



METAMORPHOSES OF ANIMALS. 125 

more resemble the true Fishes. In no class are renewed 
embryological investigations, extending over a variety of 
families, so much needed, as in that of Birds, if we desire 
to derive any assistance in their natural classification 
from the peculiarities of their development; and yet the 
general development of these animals is perhaps better 
known than that of any other tjrpe.^ The class of Mam-» 
malia^ has found in Bischoff a most successful and 
thorough investigator.^ 

* Pander (Chr. H.J, Diss, slstens stitute, Salem, vol. 2, p. 33. — Hoyer 
historiam metamorpnoseos quam (H.), Ueber die Eifollikel, der Vogel, 
oTum incubatum prioribus quinque Miiller's Arch., 1867, p. 52. — Hor- 
diebus subit; Wirceb., 1817, 8vo. — ner (F. R.), On some discoveries 
Beitrage zur Entwickelungsge- relative to th^ Chick in ovo, and its 
schichtedesHiihnchen8im£ie,Wurzb. liberation from the shell, Proc. Brit. 
1817, fol., fig.— Babr (K. E. yX Ent- Ass., 1853, p. 68. 
wickelungsgeschichte, etc., vol. 1. — ■ For the papers relating to the 
DuTROCHBT (H.), Histoire de Toeuf foetal envelopes and the placenta, and 
des Oiseauz avant la ponte, Bull, also to the different systems of organs 
Soc. Philom., 1819, p. 38. — Hunter or any organ in particular, and for 
(JonN), Observations on Animal De- human embryology generally, see 
velopment, edited, and his lUustra- Bischoff'^s article " Entwickelungs- 
tions of that process in the Bird de- geschichte," in R. Wagner's Hand- 
scribed, by R. Owen; London, 1841, wSrterbuch der Physiologic, p. 867, 
fol., ^g. — Prevost (J. L.), M^moire where everything that has been 
sur le d^veloppement du poulet dans done in this direction, up to the year 
Toeuf, Ann. Sc. Nat., 1827, vol. 12, p. 1843, is enumerated. For more re- 
415. — Preyost (J. L ) et Lebert, cent researches upon these topics, 
M6moires sur la formation des or- consult also, MuLLER*sArchiv, Wieq- 

fanes de la circulation et du sang man's Archiv, Siebold und K5lli- 

ans Tembryon du Poulet, Ann. 8c. kbr's Zeitsch. f. wiss. Zool., Milne- 

Nat., 3e s^r., i, p. 265 ; ii, 222, fig. ; Edwards, Ann. Sc. Nat., and the 

iii, p. 96. — Baudrimont (A.),etMAR- Annals and Magazine of Nat. Hist., 

TIN St. Anoe (Q. J.^, Recherches etc. 

anatomiques et physiologiques sur le ' Bisohoff(Th.L.W.), EntwickeU 

d6veloppement du foetus ; raris,1850, ungsgeschichte des Kaninchen-Eies, 

4to. — Meckel v. Hemsbach (H.), Braunschweig, 1842, 4to. ^g. — Ent- 

Die Bildung der fur partielle Furch- wickelungsgeschichte des Huude- 

ung bestimmten Eier der V5gel, etc., Eies, Braunschweig, 1845, 4to. fig.-^ 

Zeitsch. f. wiss. Zool., 1852, vol. iii, En t wickelungsgeschichte des Meer- 

p. 420. — Dareste (C), M6moire sur schweinchens, Giessen, 1852, 4to. 

rinfluence qu'exercesur le d^veloppe- fig. — Entwickelungsgeschichte des 

ment du poulet Tapplication partielle Rehes, Giessen, 1854, 4to. fig. — Pre- 

d'un vemis sur la coquille de Toeuf, vost (J. L.), et Dumas (J. A.), De 

Ann. Sc. Nat., 4e s6r., 1855, vol. 4. — la g6n6ration chez les Mammif^res, 

Weinland (D.), On the Armature of etc., Ann. Sc. Nat., 1824, vol. 3, p. 

the Lower Bill of the Hatching 113, fig. — Bojanus (L.), Observatio 

Tringa Pim^, Wils., Proc. Essex In- anatomica de foetu canino 24 dicrum, 



126 ESSAY ON CLASSIFICATION. 

Embryology has, however, a wider scope than to trace 
the growth of individual animals, the gradual building up 
of their body, the formation of their organs, and all the 
changes they undergo in their structure and in their form ; 
it ought also to embrace a comparison of these forms and 
the successive steps of these changes between all the types 
of the animal kingdom, in order to furnish definite stan- 
dards of their relative standing, of their affinities, and of 
the correspondence of their organs in all their parts. Em- 
bryologists have thus far considered too exclusively the 
gradual transformation of the egg into the perfect animal 
There remains still a wide field of investigation, to ascer- 
tain the diflferent degrees of similarity between the succes- 
sive forms which an animal assumes until it has completed 
its growth, and the various forms of difierent kinds of 
full-grown animals of the same type ; between the difier- 
ent stages of complication of their structure in general, 
and the perfect structure of their kindred ; between the 
successive steps in the formation of all their parts and the 
various degrees of perfection of the parts of other groups ; 
between the normal course of the whole development of 

etc., Act. Ac. Nat. Cur., vol. 10, p. Omithorhi/tichus paradoxusy Phil. 
139, fig. — CosTE (P.), Embryog6nie Trans. 1834, p. 655. — On the Toang 
compajr6e ; Paris, 1837, Svo. Atlas of the Orniihorhynchus paradoxus, 
4to.. — Uistoirc particuli^re et g6n6- Trans. Zool. Soc., i. p. 221 ; Proc 
rale du d^veloppemcnt des corps Zodl. Soc, ii. p. 43 ; Ann. So. Nat., 
orgnnis^s, q. a. — Rechcrches sur la 2d ser. ii. p. 303 ; iii. p. 299. — On 
generation des Mammif^res et Ic d6- the Generation of the Marsupial Ani- 
veloppement de la brebis, Ann. Sc. mals, etc., Phil. Trans., 1824, p. 333. 
Nat. 1835, III., p. 78. — Recherches — On the Placenta of the Elephant, 
sur la generation des Mammif^res ; Proc. Roy. Soc. ; London, 1857, p. 
Paris, 1834, 4to. fig. — Bernhardt 471. — Meiqs (Oh.), Obfiervations on 
(C. A.), Symbolas ad Ovi Mamma- the Reproductive Organs and on the 
Hum historiam ante pregnationem. Foetus of 2>^»Atnu«AeMirfuiir,JoQm. 
Vratisl., 4to., Miiller's Arch., 1835, Ac. Nat. Sc. Phil., new ser. 1849, yol. 
p. 228.— Barry (M.), Researches in 1, p. 267. — Wyman (F.), On the con- 
Embryology, Phil. Trans. R. Soc. nection between the Uterus and the 
1838, p. 301; 1839, p. 307; 1840, p. Chorion in Pigs, Proc. Bost. Nat 
529 ; 1841, p. 195.— Baer (H. E. v.). Hist. Soc, 1858. 
q. a. — Owen (R.), On the Ora of the 



METAMORPHOSES OF ANIMALS. 127 

one type compared with that of other tjrpes, as well as 
between the ultimate histological differences which all 
exhibit within certain limits. Though important frag- 
ments have been contributed upon these different points, 
I know how much remains to be done, from the Kttle I 
have thus far been able to gather myself by systematic 
research in this direction. 

I satisfied myself long ago that Embryology furnishes 
the most trustworthy standard to determine the relative 
rank among animals. A careful comparison of the suc- 
cessive stages of development of the higher Batrachians 
furnishes, perhaps, the most striking example of the 
importance of such investigations. The earlier stages of 
the Tadpole exemplify the structure and form of these 
Ichthyoids which have either no legs or very imperfect 
legs, with and without external gills ; next it assumes a 
shape reminding us more of the Tritons and Salamanders, 
and ends with the structure of the Frog or Toad.^ 
A comparison between the two latter families proves 
further that the Toads are higher than the Frogs, not 
only on account of their more terrestrial habits (see 
Section 1 6), but because the embryonic web, which, to 
some extent^ still unites the fingers in the Frogs, dis- 
appears entirely in the Toads, and, possibly also, because 
glands are developed in their skin, which do not exist in 
Frogs. A similar comparison of the successive changes 
of a new species of Comatula discovered by Prof. Holmes 
in the harbour of Charleston, in South Carolina, has shown 
me in what relation the different tjrpes of Crinoids of past 
ages stand to these changes, and has furnished a standard 
to determine their relative rank ; as it cannot be doubted 
that the earlier stages of growth of an animal exhibit a 

^ AaASSiz (L.), Twelye Lectures, etc., p. 8. ' 



128 ESSAY ON CLASSIFICATION. 

condition of relative inferiority, when contrasted with 
what it grows to be after it has completed its develop- 
ment, and before it enters upon those phases of its 
existence which constitute old age, and certain curious 
retrograde metamorphoses observed among parasites. 

In the young Comatula there exists a stem, by which 
the little animal is attached, either to sea weeds or to the 
cirrhi of the parent ; the stem is at first simple and with- 
out cirrhi, supporting a globular head, upon which the 
so-called arms are next developed and gradually com- 
pleted by the appearance of branches ; a few cirrhi are at 
the same time developed upon the stem, which increase in 
number untU they form a wreath between the arms and 
the stem. At last, the crown having assumed all the 
characters of a diminutive Comatula, drops off^ freeing 
itself from the stem, and the Comatula moves freely as an 
independent animal.^ 

The classes of Crustacea and of Insects^ are particularly 
instructive in this respect. Rathke, however, has described 
the transformations of so many Crustacea, that I cannot 
do better than refer to his various papers upon this sub- 
ject,^ for details relating to the changes these animals 
imdergo during their earlier stages of growth. I would 
only add, that, while the embryo of the highest Crustacea, 
— the Brachyura, — resembles by its form and structure the 
lowest types of this class, the Entomostraca and Isopoda, 
it next assumes the shape of those of a higher order, the 

1 A condensed account of the trans- • See Agassiz's Twelve Lectures, 

formations of the European Coma- p. 62, and Classification of Insects, 

tula maybe found in E. Forbes*8 etc., q. a. It is expected that Embrj- 

History of the British Starfishes, p. ology will furnish the means of »s- 

10. The embryology of our species certaining the relative standing of 

will be illustrated in one of the next every family, 

volumes of my contributions to the ' See above, page 119, note 2. 
>Iatural Ilistory of the United States. 



METAMORPHOSES OF ANIMALS. 129 

Macroura, before it appears with all the characteristics of 
the Brachynra. 

Embryology furnishes also the best measure of the true 
affinities existing between animals. I do not mean to say 
that the affinities of animals can only be ascertained by 
embryonic investigations ; the history of Zoology shows, 
on the contrary, that even before the study of the forma- 
tion and growth of animals had become a distinct branch 
of Physiology, the general relationship of most animals 
had already been determined, with a remarkable degree of 
accuracy, by anatomical investigations. It is nevertheless 
true, that in some remarkable instances, the knowledge of 
the embryonic changes of certain animals gave the first 
clue to their true affinities, while, in other cases, it has 
furnished a very welcome confirmation of relationships, 
which, before, might have appeared probable, but were still 
very problematical.- Even Cuvier, for instance, considered 
the Barnacles as a distinct class, which he placed among 
MoUusks, under the name of Cirripeds. It was not until 
Thompson ^ had shown, what was soon confiimed by Bur- 
meister and Martin St Ange, that the young Barnacle 
has a structure and form identical with that of some of 
the most common Entomostraca, that their true position 
in the system of animals could be determined ; when they 
had to be removed to the class of Crustacea, among the 
Articulata. The same was the case with the Lemoeans, 
wliieh Cuvier arranged with the Intestin^d Worms, and 
which Nordmann has shown, upon embryological evidence, 
to belong also to the class of Crustacea.^ Lamarck asso- 
ciated the Crinoids with the Polyps, and, though they were 

' Thompson's Zool. Researches, ganisation, etc., quoted p. 11J>, n. 1. 
etc.; Burmeister's Heitragc, etc.; * Nordmann's Micrographische 
Martin St. Anoe, M6in. sur Tor- Boytrivge, q. a. 

R 



130 • ESSAY ON CLASSIFICATION. 

removed to the class of Echinoderms by Cuvier before 
the metamorphoses of Comatula were known,^ the dis- 
covery of their pedunculated young furnished a direct 
proof that this was their true position. 

Embryology, further, aflfords a test of homologies in 
contradistinction to analogies. It shows that true ho- 
mologies are limited respectively within the natural 
boundaries of the great branches of the animal king- 
dom. 

The distinction between homologies and analogies, 
upon wliich the English naturalists first insisted,^ has re- 
moved much doubt respecting the real afl&nities of animals 
which could hardly have been so distinctly appreciated 
before. It has taught us to distinguish between real affi- 
nity based upon structural conformity, and similarity 
based upon mere external resemblance in form and 
habits. But, even after this distinction had been fairly 
estiiblished, it remained to determine within what limits 
homologies may be traced. The works of Oken, Spix, 
Geoffroy, and Carus,^ show to what extravagant compa- 
risons a preconceived idea of unity may le^id. It was not 
until Baer had shown that the development of the four 
great branches of the animal kingdom is essentially dif- 
ferent,^ that it could even be suspected that organs per- 
forming identical functions may be diflFerent in their 
ess(»ntial relations to one another ; and not until Rathke^ 
liad demonstrated that the yolk is in open communication 
with the main cavity of the Articulata, on the dorsal side 

* Thompson and Forbes, q. a., p. vol.i. p. 160 and 224. The extent of 
IH). Baer's information, and the compre- 

' Swainson's Geography and Clas- hcnsivcness of his views, nowhere 

sification, etc. See above, Sect. V., appear so striking] j as in this part of 

]). 2(). his work. 

^ See above, Sect. IV., notes land 2. * RATHKE'sUntcrs. iiberBild.^ete^ 

* BAER'sEntwickelungsgeschichte, see above, p. 119, n. 2, 



METAMORPHOSES OF ANIMALS. 131 

of the animal, and not on the ventral side, as in the Veite- 
brata, that a solid basis was obtained for the natural limi- 
tation of true homologies. It now appears more and 
more distinctly at every step of the progress Embry- 
ology is making, that the structure of animals is only 
homologous within the limits of the four great branches of 
the animal kingdom ; and that general homology, strictly 
proved, proves also typical identity, as special homology 
proves class identity. 

The results of aU embryonic investigations of modem 
times go to show more and more extensively, that animals 
are entirely independent of external causes in their de- 
velopment. The identity of the metamorphoses of ovipa- 
rous and viviparous animals belonging to the same type 
furnishes the most convincing evidence to that effect.^ 
Formerly it was supposed that the embryo was aflFected 
directly by external influences, to such an extent, that 
monstrosities, for instance, might be ascribed to the in- 
fluence of external causes. Direct observation has shown 
that they are founded upon peculiarities of the normal 

^ This seems the most appropriate though they may agree in laying 
place to remark, that the distinction eggs or bringing forth living young. 
made between yiviparous and ovipa- The essential feature upon which 
rous animals is not only untenable any important generalization must be 
as far as their first origin in the egg based is, of course, the mode of de- 
is concerned, but also unphysiolo- velopment of the germ. In this re- 
gical, if it is intended, by this de- spect we find that Selachians, whether 
signation, to convey the idea of oviparous or viviparous, agree with 
any affinity or resemblance in their one another. This is also the case 
respective modes of development, with the bony fishes and the reptiles, 
Fishes show more distinctly than any whether they are respectively ovi- 
other class, that animals, the devel- parous or viviparous ; even the pla- 
opment of which is identical, in all cental and implacental Mammalia 
its leading features, may either be agree with one another in what 
yiviparous or oviparous ; the difier- is essential in their development. 
ence here arising only from the con- Too much importance has hitherto 
nection in which the egg is devel- been attached to the connections in 
oped, and not from the development which the germ is developed, to the 
itself. Again, viviparous and ovipa- exclusion of the leading features of 
rous animals of different classes differ the transformations of the germ it- 
greatly in their development, even self. 

k2 



132 ESSAY ON CLASSIFICATION. 

course of their development.^ The snug berth in which 
the young of all Mammalia undergo their first transforma- 
tion — the womb of their mother, excludes so completely 
the immediate influence of any external agent, that it is 
only necessary to allude to it to show how independent 
their growth must be of the circumstances in which even 
the mother may be placed This is equally true of all 
other vivaparous animals, as certain snakes, certain sharks, 
and the viviparous fishes. Again, the uniformity of tem- 
perature in the nests of birds, and the exclusion, to a cer- 
tain degree, of influences which might otherwise reach 
them, in the various structures which animals build for 
the protection of their young or of their eggs,^ show dis- 
tinctly, that the instinct of all animals leads them to re- 
move their progeny ft'om the influence of physical agen- 
cies, or to make these agents subservient to their purposes, 
as in the case of the ostrich. Reptiles and terrestrial 
Mollusks bury their eggs to remove them fix)m varying 
influences ; fishes deposit them in localities where they 
are exposed to the least changes. Insects secure theirs in 
various ways. Most marine animals living in extreme 
climates lay their eggs in winter, when the variations of 
external influences are reduced to a minimum. Every- 
where we find evidence that the phenomena of life, though 
manifested in the midst of all the most diversified phy- 
sical influences, are rendered independent of them to the 
utmost degree, by a variety of contrivances prepared by 
the animals themselves for self-protection, or for the pro- 
tection of their progeny from any influence of physical 
agents not desired by them, or not subsement to their 
own ends. 

' Bisciiopp (Tn. L. W.), in R. * Burdach's Phjsiologie, etc., q. 

Wagner's llandwGrtcrbuch der Phy- a. 2d ed. vol. 2, Sect. 334-8. See, also, 

Biologic, Article ** Entwickeluogs- Kibby and Spencers Introduction, 

gcschichte," p. 885, etc., q. a. 



DURATION OF LIFE. 133 



SECTION XIX. 

DURATION OF LIFE. 

There is the most extraordinary inequality in the ave- 
rage duration of the life of diflferent kinds of animals and 
plants. While some grow and reproduce themselves and 
die in a short summer, nay, in a day, others seem to defy 
the influence of time.^ 

Who has thus apportioned the life of all organized 
beings ? To answer this question, let us first look at the 
facts of the case. In the first place, there is no conform- 
ity between the duration of life and either the size or 
structure or habitat of animals ; next, the system in wliich 
the changes occurring during any period are regulated 
difiers in almost every species, there being only a slight 
degree of uniformity between the representatives of dif- 
ferent classes, within certain limits. 

In most Fishes and the Eeptiles proper, for instance, 
the growth is very gradual and uniform, and their de- 
velopment continues through life, so much so that their 
size is continually increasing with age. 

In others, the Birds, for instance, the growth is rapid 
during the first period of their life, until they have 
acquired their full size, and then follows a period of 
equilibrium, which lasts for a longer or shorter period in 
different species. 

In others again, which also acquire within certain Umits 
a definite size, the Mammalia, for instance, the growth is 
slower in early Ufe, and maturity is attained, as in man, 

^ ScHUBLEB, (Gust.,) Beobachtun- und PflaDzenreich, Tubingen, 18.31, 
gen uber jahrliche periodisch wieder- 8vo. — Quetelet, (A.,) Phcuom^nes 
kchrende Erscheinungen im Thier- p6riodi(^uos, Ac. Brux. 



134 ESSAY ON CLASSIFICATION. 

at an age which fonns a much longer part of the whole 
duration of life. In Insects the period of maturity is, on 
the contrary, generally the shortest, while the growth of 
the larva is very slow, or, at least, that stage of de- 
velopment lasts for a much longer time than the life of 
the perfect Insects. There is no more striking example 
of tins peculiar mode of growth than the seventeen years 
locust, so fully traced by Miss M. H. Morris.^ 

Whilst all long-lived animals continue, as a matter of 
course, their existence through a series of years, under the 
varying influence of successive seasons, there are many 
others which are periodical in their appearance ; this is 
the case with most insects,^ but perhaps in a still more 
striking manner with Medusae.^ 

The most interesting point, however, in this subject is 
the change of character which takes place in the different 
stages of growth of one and the same animal Neither 
Vertebrates nor Mollusks, nor even Radiates, exhibit in 
this respect anything so remarkable in the continuous 
changes which an individual animal undergoes as Insects, 
and among them those with so-called complete meta- 
morphosis. Here the young (the larva) is an active, 
wormlike, voracious, even carnivorous being, which in 
middle age (as a chrysalis) becomes a mummy-like, almost 
motionless maggot, incapable of taking food, and ends 
life as a winged and active insect. Some of these larvae 
are acjuatic and veiy voracious, when the perfect insect 
is aerial and takes no food at all.^ 

* See also IIarri8'8 Insects in- * Burmsister's Handb. d. Entom. 

jurious to Vegetation, p. 184, 2d. etc. — Lacordaire, Introd. k TEnto- 

edit. p. 180. mologie, etc. — Kirby and Spexck, 

' llER0LD,(E.,)Teut8cher Raupen- Introd. to Eutomol., etc., q. a., give 

Kalender, Nordhausen. 1845. accounts of the habits of Insects 

3 Agassi z*8 Acalephs of North during their metamorphoses. 
America, p. 228. 



ALTERNATE GENERATIONS. 135 

Is there any thing in this regulation of the duration of 
life in animals which recalls the agency of physical 
forces? Does not, on the contrary, the fact, that, while 
some animals are periodical and bound to the seasons in 
their appearance, others are independent of the course 
of the year, show distinctly their independence of all 
those influences, which, under a common expression, are 
called physical causes 1 Is this not further illustrated in 
the most startling manner by the extraordinary changes, 
above alluded to, which one and the same animal may 
undergo during different periods of its life ? Does not 
this directly prove the immediate intervention of a power 
capable of controlling all these external influences, as well 
as regulating the course of life of every being, and esta- 
bUshing it upon such an immutable foundation, within 
its cycle of changes, that the iminterrupted action of 
these agents does not interfere with the regular order of 
its natural existence ? 

There is, however, stiU another conclusion to be drawn 
from these facts : they point distinctly at a discriminating 
knowledge of time and space, at an appreciation of the 
relative value of unequal amounts of time and an 
unequal repartition of small, unequal periods over longer 
periods, which can only be the attribute of a thinking 
being. 



SECTION XX. 

ALTESNATE OENESATIONS. 



While some animals go on in gradual development, 
from the first formation of their germ to the natural end of 
their life, and bring forth generation after generation, a 



136 ESSAY ON CLASSIFICATIOK. 

progeny which runs with never-varying regularity througli 
the same course, there are others which multiply in 
various ways, by division and by budding,^ or by a 
strange succession of generations, differing one £ix)m the 
other, and not returning in a direct course to their 
typical cycle. 

The facts which have led to the knowledge of the 
phenomenon now generally known under the name of 
cdtomaie gene^xUion were first observed by Chamisso and 
Sars, and afterwards presented in a methodical connection 
by Steenstrup, in his famous pamphlet on that subject^ 
As a brief account of the facts may be found in almost 
every text-book of Physiology, I need not repeat them 
here, but only refer to the original investigations, in 
which all the details known upon this subject may be 
found. ^ These facts show, in the fii-st place, with regard 
to llydroid Medusse, tliat individuals bom from eggs 
may be entirely different from those wliich produced the 
eggs, and may end their life without ever undergoing 
themselves such changes as would transform them into in- 

^ Much information useful to the tion of Procreating Indiyidualfl from 

zoologist, may bo gathered from a single Ovum ; London, 1849, 8vo. 

Braun's paper upon the Budding of — On Metamorphosis and Metagene- 

Plauts, q. a., p. 24, note 3. The pro- sis, Ann. and Mag. Nat. Hist., 2a ser. 

cess of multiplication by budding or vol. 8, 18.*>7, p. 59. — Prosch, (V.,) 

by division, and that of sexual repro> On Parthenogenesis og Qcnerations- 

duction, are too often confounde<l by vcxel et Bidrag til Generationslteren ; 

zoologists, and this confusion has al- Kiobenhavn, 1851. — Leuckart, (R.,) 

ready led to serious misconstructions Ucber Metamorphose, ungeschlecht- 

of well known facts. licho Vermehrung, Generationswech- 

* Steensthup, J.,) Ueber den Go- scl, Zeitsch. f. wiss. Zool., vol. 3, 1851. 

nerationswechsel, 4. a., p. 103, note 3. — 1>ai<a, (J. D.,) On the Analogy be- 

'^ See the works quoted above, p. tween the Mode of Reproductioa ia 

103, note 3, and p. 105, note 1, also Plants and the ** Alternation of Gene- 

Cards, (V.,) Zur nahern Kenntniss rations'' observed in some Radiata, 

des Generations wcchsels ; Leipzig, Amer. Joum. A. and 8c., 2d ser. vol. 

1841), 8vo. — Einige Worte iiber Me- 10, p. 341. — Ehrenbbrg, (C. G.,) 

tamor[)hose und Generationswechsel, Ueber die Formenbestandigkeit und 

Zoitsch. f. wiss. Zool., 1851, vol. 3, den Entwickelungskreis dcr orgaa- 

p. 359. — Owen, (R.,) On Partheno- ischen Formen,Mouatsbcr. deiAJutd. ; 

genesis, or the tSuccetffiivo Produc- Berlin, 1852, 8vo. 



ALTERNATE OENERATIONS. 137 

dividuals similar tx) their parents ;^ and they show further 
that this brood, originated from eggs, may increase and 
multiply by producing new individuals like themselves 
(as in Syncorynejy or of two kinds (as in Camj)anularia), 
or even individuals of various kinds, all diflFering to a 
remarkable extent one from the other (as in HydractintaJ, 
but in no case resembling their common parent. None 
of these new individuals have distinct reproductive 
organs, any more than the first individuals bom from 
eggs, their multiplication taking place chiefly by the 
process of budding ; but^ as these buds remain gene- ^.^ 

rally connected with the first individual bom from an Jjjir 
egg, they form compound communities, similar to some 
polypstocks. Now some of these buds produce, at certain 
seasons, new buds of an entirely different kind. These 
generally drop off* from the parent stock at an early 
period of their development (as in Syncoryne, Cam- 
panulartay etc.), and then undergo a succession of changes, 
which end by their assuming the character of the pre- 
vious egg-laying individuals. Organs of reproduction of 
the two sexes are developed in them meanwhile, which, 
when mature, lead to the production of new eggs. In 
others (as in Hydractiniajy the buds of this kind do not 
drop off", but fade away upon the parent stock, after 
having undergone all their transformations, and also 
produced in due time a number of eggs.^ 

> Polymorphism among individuals and fourth volumes of my Oontrib. to 

of the same species is not limited to the Nat. Hist, of the U. S., and to 

Acalephs ; it is also observed among which I do not allude here, as thoy 

genuine Polyps, the Madrepores for could not be understood without nu- 

example, and among Bryozoa, As- merous drawings. The case of Hy- 

cidians, Worms, and Crustacea {Lu' dractinia is not quite correctly repre- 

l>ea)y and even among Insects (Bees), sented in the works iu which that 

' I have observed many other com- animal has been described. Respcct- 

biuationsof a similar character among ing Physalia and the other Siphono- 

the Hydroid Medusa), which I shall phora, see the works quoted above, 

describe at full length in the third p. 103, note 3. 



138 ESSAY ON CLASSIFICATION. 

In the case of the Medusae proper,^ the parent lajB eggs 
from which poljrplike individuals originate ; but here these 
individuals separate by transverse constrictions into a num- 
ber of disks, and every one of these undergoes a succession 
of changes, which end in the production of as many indi- 
viduals, each identical with the parent, and capable in its 
turn of laying eggs, (some, however, being males, and 
others females.) But the polyplike individuals bom from 
eggs may also multiply by budding, and each bud undergo 
the same changes as the first, the base of which does not 
die, but is also capable of growing up again and of re- 
peating the same process. 

In other classes, other phenomena of a similar character 
have been observed, which bear a similar explanation. 
J. MtiUer^ has most fully illustrated the alternate genera- 
tions of the Echinoderms ; Chamisso, Steenstrup, Eschricht, 
Krohn, and Sars, those of the Salpse ;^ von Siebold, Steen- 
strup, and others, those of certain Intestinal Worms.* 

This alternate generation differs essentially from meta- 
morphosis, though some writers have attempted to identify 
these two processes. In metamorphosis, as observed among 
Insects, the indi\ddual bom from an egg goes on under- 
going change after change in direct and immediate suc- 
cession, until it has reached its final transformation ; but, 
however different it may be at different periods of its life, 
it is always one and the same individual. In altemat<3 
generations, the individual bom from an egg never as- 
sumes tlu-ough a succession of transfonnations the cha- 
racter of its parent, but produces, either by internal or 
external budding or by division, a number — sometimes 

^ See Siebold, and Sars, q. a., p. ^ See the works, q. a., page 108, 

103, note 3. note 3. 

* MuLLER, (J.,) Ueber den allge- * See the works, q. a., p. 115, note 

mcincn Plan, etc., q. a., p. 105, note 1. 1, and 116, note 1. 



ALTERNATE GENERATIONS. 139 

even a large number — of new individuals, and it is this 
progeny of the individuals bom from eggs which grows 
and assumes again the characters of the egg-laying indi- 
viduals. 

There is really an essential dijQference between the 
sexual reproduction of most animals and the multiplica- 
tion of individuals in other ways. In ordinary sexual re- 
production, every new individual arises from an egg, and, 
by a regular succession of changes, assumes the character 
of its parents. Now, though all species of animals re- 
produce their kind by eggs, and though in each there is 
at least a certain number of individuals, if not all, which 
have sprung from eggs, this mode of reproduction is not 
the only one observed among animals. We have already 
seen how new individuals may originate from buds, which 
in their turn may produce sexual individuals ; and we 
have also seen how, by division, individuals may also 
produce other individuals, differing from themselves quite 
as much as the sexual buds, alluded to above, differ from 
the individuals which produce them. There are yet still 
other combinations in the animal kingdom. In Polyps, 
for instance, every bud, whether it is freed from the parent 
stock or not, grows up at once to be a new sexual indi- 
vidual ; and in many animals which multiply by division, 
every new individual thus produced assumes also at once 
the characters of those bom from eggs.^ There is, finally, 
one mode of reproduction which is pecuhar to certain 
Insects, in which several generations of fertile females 
follow one another, before males appear again.^ 

What comprehensive views must physical agents be 

1 Milvb-Edwabds, Rech. anat. et logie, etc. ; Paris, 1745. — Owen, Par- 
zool. faites pendant un Voyage sur thenogenosis, etc., q. a., p. 136 ; com- 



leg c6te8 de Sicile, 3 vols. 4to. fig. pare also Siebold, (C. Th. E. von.,) 

' BoaiTET, (Oh.,) Trait6 d'Insecto- Wahre Parthenogenesis, q. a. p. 120. 



1 40 ESSAY ON CLASSIFICATION. 

capable of taking,, and what a power of combination 
must they possess, to be able to ingraft all these compli- 
cated modes of reproduction upon structures already so 
complicated ! — But, if we turn away from mere fancies, 
and consider the wonderful phenomena just alluded to in 
all their bearings, how instructive they appear with refer- 
ence to this very question of the influence of physical 
agents upon organized beings ! For here we have animals 
endowed with the power of multiplying in the most ex- 
traordinary ways, every species producing new individuals 
of its own kind difiering to the utmost from their parents. 
Does this not seem, at first, as if we had before us a perfect 
exemplification of the manner in which difierent species 
of animals may originate one from the other, and increase 
the number of types existing at first ? And yet, with all 
this apparent freedom of transformation, what do the 
facts finally show? That all these transformations are 
the successive terms of a cycle, as definitely closed within 
precise limits, as in the case of animals the progeny of 
which resembles the immediate parent in all succes- 
sive generations. For here, as everywhere in the or- 
ganic kingd(jms, these variations are only the successive 
expressions of a well regulated cycle ever returning to its 
own type. 

SECTION XXL 

SUCCESSION OF ANIMALS AND PLANTS IN GEOLOGICAL TIMES. 

Geologists hardly seem to appreciate fully the extent 
of the intricate relations exhibited by the animals and 
plants whose remains are found in the difierent successive 
geological formations. I do not mean to say that the 
investigations we possess respecting the zoological and 



SUCCESSION OF ANIMALS AND PLANTS. 141 

botanical characters of these remains are not remarkable 
for the accuracy and for the ingenuity with which they 
have been traced. On the contrary, having myself thus 
far devoted the better part of my life to the investigation 
of fossil remains, I have learned early, from the difficulties 
inherent in the subject, better to appreciate the wonder- 
ful skill, the high intellectual powers, the vast erudition, 
displayed in the investigations of Cuvier and his succes- 
sors upon the faimsB and florae of past ages.^ But I can- 
not refrain from expressing my wonder at the puerility 
of the discussions in which some geologists still allow 
themselves to indulge, in the face of such a vast amount 
of well digested facts as our science now possesses. They 
have hardly yet learned to see that there exists a definite 
order in the succession of these innumerable extinct 
beings ; and of the relations of this gradation to the other 

* CuTiER, (G.,) Recherches sur les et Bonnee, 1836, 4to. ^g. — ^Die Gat- 

Ossemens fossiles des Quadruples, tuneen der fossilen Pmrnzen, ver* 

etc. ; Paris, 1812, 4 vols. 4to. ; nouv. glichen mit deuen der Jetztwelt, etc., 

edit. Paris, 1821-23, 6 vols. 4to, ; 4e Bonn, 1841-48, 4to. fig.— Monogra- 

6dit. 10 vols. 8vo. and 2 vols. pi. 4to. phie der fossilen Oonifcren. Diissel- 

— SowBBBT, (James,) The Mineral dorf, 1850, 4to. fig. — More special 

Conchology of Great Britain ; Lond., works arc quoted hereafter ; but 

1812-19, 6 vols. 8vo. fig. — Schlott- only such will be mentioned as 

HEix, E. F. v.,) Die Petrefactenkunde, have advanced the progress of Geo- 

etc., Gotha, 1820, 8vo. fig. — Lamabck, logy and Palaeontology, or contain 

(J. B. D£,) M6moires sur les fossiles full reports of the present state of 

des environs de Paris, Paris, 1823, 4to. our science, or such as have spe- 

fig. — GoLDFuss, (G. A.,) Petrefacta cial reference to America. Refer- 

Germanise, Dusseldorf, 1826-33, fol. ences to the description of species 

fig. — Stebitberf, (Kaspab, M. Gb. may be found in Bbonn, (H. G.,) 

V.,) Yersuch einer geognostisch-bo- Index palasontologicus ; Stuttgart, 

tanischen Darstellung der Flora der 1848-49, 3 vols. 8vo. — See also Kefer- 

Vorwelt ; Leipzig una Prag, 1820-38, stein, (Chb.,) Geschichte und Lite- 

fol. fig. — Bbongniabt, (An.,) Pro- ratur der Geognosie ; Ilalle, 1840, 1 

drome d*une Histoire des V6g6taux vol. 8vo. — Abohiac, (Vic. d*,) ITis- 

fossiles ; Paris, 1818, 2 vols. 8vo. — toire des progr^ de la G6ologio ; 

Histoire des Y^g^tauz fossiles ; Paris, Paris, 1847, et suiv. 4 vols. 8vo. ; and 

1828-43, 2 vols. 4to. fig. — Lindlst, the Transactions, Journals, and Pro- 

(J.,) and HuTTON, (W.,) The Fossil ceedings of the Geological Societies of 

Flora of Great Britain ; London, 1831- London, of Paris, of Berlin, of Vienna, 

37, 3 vols. 8vo. — Goppert, (H. R.,) etc. ; also, Leonhabd and Bbonn^s 

Bystema Filicum fossilium, Vratisl. Neues Jahrbuch, etc. 



142 ESSAY ON CLASSIFICATION. 

great features exhibited by the animal kingdom, of the 
great fact that the development of life is the prominent 
trait in the history of our globe,^ they seem either to 
know nothing, or to look upon it only as a vague specu- 
lation, plausible perhaps, but hardly deserving the notice 
of sober science. . 

It is true, Palaeontology as a science is very yoimg; 
and it has had to fight its course through the unrelenting 
opposition of ignorance and prejudice. What amount of 
labour and patience it has cost merely to establish the fact 
that fossils are really the remains of animals and plants 
that once actually lived upon earth,^ only those know who 
are fiimiliar with the history of science. Then it had to 
be proved that they are not the wrecks of the Mosaic 
deluge, which, for a time, was the prevailing opinion, even 
among scientific men.^ After Cuvier had shown beyond 
question that they are the remains of animals no longer 
to ])e found upon earth among the living, Palaeontology 
acquired for the first time a soUd basis. Yet the amount 
of labour which it has cost to ascertain by direct evi- 
dence how these remains are distributed in the soUd 
crust of our globe, what differences they exhibit in suc- 
cessive formations,^ and what their geographical distribu- 

1 AoASSiz's Geological Times, etc., fossils of the oldest geological forma- 

q. a., p. 3o, note 2. — Dana's Address tions, see the works quoted aboTe, p. 

to the Amer. Ass. for Adv. Sc. 8th 32, note 1. Also, McCoy, (F.,> Sy- 

Meeting, held at Providence, 1855. nopsis of the Silurian Fossils of 

^ SciLLA, (Ag.,) La vana specula- Ireland ; Dublin, 1846, 4to. fig. — 

zionedesingannatadalsenso; Napoli, Geinitz (U. D.^, Die Yersteinerun- 

1670, 4to. fig. gen der Grauwackenformation; Leip- 

3 SciiKUCUZER, (J. J.,) Homo Di- zig, 1850 53, 4to. fig. — And for local 

luvii testis et 6f6aKovos ; Tiguri, 1726, information, see the geological reports 

4to. — BucKLAND, (W.,) Reliquiae di- of the dififerent States of the Union, a 

luvianao, or Observations on the Or- complete list of which, with a sum- 

ganic Remains attesting the Action mary of the Geology, may be found 

of an Universal Deluge ; London, in ^IARCOu's (J.), R6sum6 ezplicatif 

1826, 4to. fig. d'une carte g^oiogique des Etats- 

* For references respecting the Unis, Bull. Soc. G6ol. de France; 



SUCCESSION OF ANIMALS AND PLANTS. 143 

tion is, only those can fully appreciate who have had a hand 

Paris, 1855, 2de s6r., voL 12. — For tologie, etc.; Stuttgart, 1836, 4to., 
the Devonian system : Phillips (J.), fig. — Romeb (Fb. A.), Die Yerstein- 
Fig^ures and Descriptions of the Pa- erungen des Norddeutschen Oolithen- 
Imzoic Fossils of Cornwall, Devon, Qebirges; Hanover, 1836, 4to., fig. — 
and West Somerset, etc. ; London, Zieten (C. H. v.), Die Versteinerun- 
1841, 8vo. — Abchiac (Vic. d') and gen Wurtembergs; Stuttgart, 1830- 
Yekhjbuil (Ed. de). Memoir on the 34, fol., fig. — Obbignt (Alc. n'), Pa- 
Fossils of the Older Deposits in the 16ontologie fran9ai8e ; Paris, 1840-53, 
Rhenish Provinces ; Paris, 1842, 4to., 8vo,fig. — Mobbis (J.) and Lycett 
fig. — Sardbeboeb (G. und Fb.), Sys- (J.), Mollusca from the Great Oolite 
tematische Beschreibimg und Abbil- (Palseont. Soc.) ; London, 1850-55, 
dung der Yersteinerungen des Bhei- 4to., fig.*— For the Cretaceous perioct : 
nischen Schichtensystems in Nassau ; Mobton (S. G.), Synopsis of the Re- 
Wiesbaden, 1850-54, 4to., fig. — For mains of the Cretaceous Group of the 
the Carboniferous period: Phillips United States ; Philadelphia, 1834, 
(J.), Illustrations of the Geology of 8vo., fig. — Obbiony (Alc. n'), Pal6- 
Yorkshire; London, 1836, 2nd vol., ont. frang., q. a. — Geinitz (JI. Bb.), 
4to., ^g, — Db Koninok (L.), Descrip- Charakteristik der Schichten und Pe- 
tions des animaux fossiles qui se trefakten des Kreidegebirges ; Dres- 
trouvent dans le terrain houiller de den, 1839-42, 4to., fig. — Pictet ^F. 
la Belgique ; Li^e, 1842, 2 vols. 4to., J.) et Roux (W.), Description aes 
fig.; suppl., etc. — McKoT (Fb.), Sy- fossiles qui se trouvent dans les gr^s 
nopsis of the Carboniferous Fossils of verts des environs de Geneve, M6ra. 
Ireland; Dublin, 1844, 4to., fig. — Soc. Phys., etc.; Geneve, 1847-52, 
Gebmab (E. Fb.), Die Versteinerun- vols. 12 et 13. — ROmeb (F. A.), Die 
gen des Steinkohlengebirges ; Halle, Yersteinerungen des norddeutschen 
1844-53, fol., fig. — Geinitz (H. BX Kreidegebirges; Hanover, 1841, 4to., 
Die Yersteinerungen der Steinkohl- fig. — Die Kreidebildungen von Texas; 
enformation ; Leipzig, 1855, fol., fig. B^nn, 1852, 4to., fig. — Reuss (A. £.), 
— For the Permian system : QuEir- Die Yersteinerungen der bdhmischen 
STEDT (A.), Ueber die Identit&t der Kreideformation; Stuttgart, 1845-46, 
Petrificate des Thuringischen and 4to., fig. — Mulleb (Jos.), Monogra- 
Englischen Zechsteins, Wiegman's phie der Petrefacten der Aachener 
Archiv, 1835, i, p. 75. — Geinitz (H. kreideformation ; Bonn, 1851, 4to., 
B.) und Gutbieb (A.^, Die Yerstein- fig. — Shabpe (D.), Fossil Remains 
erunffen des Zechstemgebirges, etc.; of Mollusca found in the Chalk of 
Dre«aen, 1849, 4to., fig. — Kino (W.), England (Palaeont. Soc.) ; London, 
Monograph of the Permian Fossils of 1854, 4to., fig. — Hall (James) and 
England (Palreont. Soc.) ; London, Meek (F. B.), Descriptions of New 
1850, 4to., fig. — Swallow (J. C.) and Species of Fossils from the Cretaceous 
Hawn (F.), The Rocks of Kansas, Formationsof Nebraska, Mem. Amer. 
with Descriptions of New Permian Akad., 1856, vol. 5. — For the Tertia- 
Fossils, by J. C. Swallow, Trans. Ac. ries : Bboochi (G. B.), Conchiologia 
8c., St. Louis, 1858. — For the Tri- fossile subappennina, etc.; Milano, 
<uie system: Albebti (Fb. v.), Bei- 1814-43, 2 vols., 4to., fig. — Des 
trag zur einer Monographic des bun- Hates (G. P.), Description des co- 
ten 8andsteins,Mushelkalks, und Keu- quilles fossiles des environs de Paris, 
pers; Stuttgart und Tiibingen, 1834, 1824-37, 3 vols. 4to., At].— Bronn 
8vo. — For the Jurassic: Phillips (H. G.), Italiens Tertiargebilde; Hei- 
(J.), Illustrations of the Geology of delberg, 1831, 8vo. — Lea (I.), Con- 
Yorkshire; York, 1829, vol. i, 4to., tributions to Geology; Philadelphia, 
fig.— PcscB (G. G.), Polens Palseon- 1833, 8vo., fig.— Conbad (T. A.), Fos- 



144 ESSAY ON CLASSIFICATION. 

in the workJ And even now how many important ques- 
tions still await an answer ! 

One result, however, now stands imquestioned — ^the ex- 
istence during each great geological era^ of an assemblage 
of animals and plants diflfering essentially for each period. 
And by period I mean those minor subdivisions in the 
successive sets of beds of rocks which constitute the strati- 
fied crust of our globe, the number of which is daily increas- 
ing as our investigations become more extensive and more 
precise.^ What remains to be done is to ascertain with 

sil Shells of the Tertiary Formations ' Geological text-books : De la Be- 
of North America; Philadelphia, oh e, (Sir H. T.,) Oeo|ogical Manual; 
1832-36, 8vo., fig.— Qrateloup (Dr.), London, 1833, 1 vol. Bvo. ; German 
Conchyliologie fossile du bassin de Trans, by Dechen ; French by Bro- 
TAdour, etc.; Bordeaux, 1837, 8vo., chant de Villers. — The Geological Ob- 
fig. — Matueron (Ph.), Catalogue server; London, 1851, 8vo. — Ltell, 
m6thodique et descriptif des corps (Sir 0.,) Manual of Elementary Geo- 
organis^s fossiles, etc. ; Marseilles^ logy ; Londoni 1851, 1 vol. Bvo. — 
1842, 8vo. — Berendt (G. C), Orga- Principles of Geology, etc. ; London, 
nische Reste im Bernstein ; Berlin, 1830, 2 vols. 8vo. ; 8th edit. 1850, I 
1845-54, fol, fig.— Wood (S. V.), A vol. 8vo.— Naumakn, (C. Fb.,) Lehr- 
Monograph of the Crag Mollusks buch der Geognosie; Lcpzig, 1850- 
(Palteont. Soc), 1848-50, 4to., fig.— 54, 2 vols. 8vo. Atl. 4to.— Voot, (C.,) 
Edwards (F. E.), Eocene MoUusca Lehrbuch der Geologie und Petre- 
(PaloDont. Soc.) ; London, 1849-52, faktenkunde ; Braunschweig, 1854, 
4to., fig. — II6UNES3 (M.), Die Fossi- 8vo. 2 vols., 2d edit. — Text-books on 
Icn Mollusken dcs Tertiiir-Beckens Fossils : Bbonn, (H. G.,) Lethsca 
von Wien; Wion, 1H51, 4to., fig.— Geognostica ; Stuttgart, 1835-37, 2 
Beyricii (E.), bio Conchylien des vols. 8vo. Atl. fol. ; 3d edit, with Fb. 
norddeutscheu Tertiiirgcbirges ; Ber- Roemer, 1846, et seq. — Pictet, (F. 
lin,1854 57, 8vo., fig. — Tuomey (M.), J.,) Traits 616mentaire de Pal^on- 
and Holmes (Fr.S.), Fossils of South tologie, etc. ; Paris, 1844-45, 4 vols. 
Carolina; Charleston, 1855-57, 4to., 8vo. fig.; 2de 6dit. 1853 et seq. 8to. 
fig. Atl. 4to. — Orbiqny, (Alc. d',) Cours 
^ Bucn (L. v.), P6trifications re- 616mcntairc de Palcontologie ; Paris, 
cueillies en Aiiicrique, par M. Alex. 1852,3 vols. 12mo. — Giebel, (E. G.,) 
dc Humboldt et par M. Ch. Degon- Fauna der Vorwelt ; Leipzig, 185^ 
hard; Berlin, 1838, fol., fig. — Or- 2 vols. 8vo. — Allgemeine PaJsconto- 
BiGNY (Alc. d'). Voyage dans rAm6- logic ; Leipzig, 1852, 1 vol. Bvo. — 
rique Aleridionale, etc. ; Paris, 1834- Quexstedt, (F. A.,) ITandbuch der 
43, 7 vols., 8vo., Atl., 4to. — Akchiac Pctrcfaktenkunde ; Tiibingen, 1852, 
(Vic. D',)ut IIaimk, (J.,) Description 8vo.tig. Unfortunately, there does not 
des animaux fossiles du groupc num- exist a single English text-book of 
mulitique de Tlnde ; Paris, 1S53, 4to. Palocontology. A translation of Pic- 
fig. — Lkuckakt, (F. 8.,) I'cber die tet's and Bronn^s works would be par- 
Verbrcitung der ubriggcblicl)cnen ticularly desirable, 
licste einer vorwcltlichcuychopfung; ' At first only three great periods 
Freiburg, 1835, 4to. were distinguished, the primary|tho 



SUCCESSION OF ANIMAI^ AND PLANTS. 145 

more and more precision the true affinities of these remains 
with the animals and plants now living, the relations of 
those of the same period to one another and to those of 
the preceding and following epochs, the precise limits of 
these great eras in the development of Hfe, the character 
of the successive changes which the animal kingdom has 
undergone, the special order of succession of th,e represen- 
tatives of each class,^ their combinations into distinct faimse 

secondary, and the tertiary ; after- fig. (without date.) — HikLL (J.), 

wards,8ixor8eTeD(DelaB^he); lately Pala&ont. of New York, q. a. — Gold- 

from ten to twelve; and now, the num- fuss (Q. A.), Petref. Germ., q. a.— > 

ber is almost indefinite, at least unde- DeKoxinck (L.), et Lehom (H.), Re- 

termined in the present stage of our cherches sur les Crinoides, etc., Brux- 

knowled^re, when many geologists elles, 1854, 4to. fig. — OwEif (D.D.), 

would only consider as subdivisions and SnuMikHi) (6« F.), Description of 

of longer periods, what some palasou- New Species of Crinoidea, Joum. 

tologists are inclined to consider as Ac. Nat. 8c. ; Philad. 1850, 4to. fig. — 

distinct periods. Sismonda (£.), Monographia degli 

^ The principal Monographs re- Echinidi fossili del Piemonte ; To- 

lating to special classes or families, rino, 1840, 4to. fig. — Des Moultns 

are the following ; Polyps and In- (C), Etude sur les Echinides ; Bor- 

fumria: Michelir (H.), Iconogra- deaux, 1835-37, 8vo. fig. — Aqassii 

phie Zoophytologique, raris, 1841- (L.), Monogr. Echin , q. a., p. 80. — 

45, 4to. fig. — Edwards (H. Milne), Catalogue raisonn6, etc., q. a., p. 44. 

et Haimb (J.), Recherches, etc., q. a., I quote this paper under my name 

p. 44. — Polypiers fossiles des terrains alone, because that of Mr. Desor, 

Si^ozoiques, Arch. Mus., toL 5. — which is added to it, has no right to 

onograph of the British Fossil be there. It was added by him, after 

Corals, Palseont. Soc. London, 1850- I had left Europe, not only without 

55, 4to. fig. — Lonsdale (W.), On the authority, but even without my leam- 

Oorals from the Tertiary Formations ing it, for a whole year. The genera 

of North America, Joum. Geol. Soc., Goniocidaris, Mespilia, Boletia, Le- 

I., p. 495 ; Sill. Joum. 2d ser. lY., nita, Gualteiia, Lovenia, Breynia, 

p. 357. — McOoT (Fb.), Contributions which bear his name— whereas they 

to British Palasontology, Cambridge, should bear mine, as I established 

1854, 1 vol. 8vo. fig. — Eieferences to and named them, while Mr. Desor 

all minor papers may be found in was travelling in Sweden — were 

Edwards and Haime*8 Recherches. — appropriated by him, without any 

Ehbbnbebo (C. G.), Mikrogeologie, more right, by a mere dash of the 

Leipzig, 1854, fol. fig. — Echinoderms : pen, while he was carrying my manu- 

MiLLBB (J. C.), A Natural History script through the press. How many 

of the Crinoidea, Bristol, 1821, 4to. species he has taken to himself, in 

fig.— Obbiont (Alo. d*), Histoire na- the same manner, I cannot tell. As 

torelle g6n6rale et particuli^e des the printed work, and a paper pre- 

Crinoides Tivans et fossiles, Paris, sen ted by me to the Academy of Sci- 

1S40, 4to. fig. — Austin ^Th. and ences of Paris, in 1846, exhibit, to 

Th. Jr.), Monograph ot Recent every one acquainted with zodlogical 

and Fossil Crinoidea, Bristol, 4to. nomenclature, internal evidence of 



146 ESSAY ON CLASSIFICATION. 

during each period ; not to speak of the causes of these 
changes, or even the circumstances under which they 
have taken place. 

my statement, — ^such, for instance, fig. — ^Db KoiriiroK (L.), Beeherdief 
as my name left standing as autho- sur lea animaux fosoles ; Lieges, 
rity for the species of Mespilia, Le- 1847, 4to. fig. — ^Agassis (L.), Etudes 
nita, Gualteria, and Breynia, while crit. q. a., p. 80. — ^Fatrb (A.), Obser- 
the genera bear his, — I need not al- yations but leB DiceratoB ; Okn^ve, 
lude further to the subject. This is 1843, 4to. fig. — Bblla&di (L.),eMi- 
one of the most extraordinary cases chellotti (G.), Saggio orittografico 
of plagiarism I know of. — Desob(E.), sulla classe dei Qasteropodi foBsili, 
Synopsis des £chinides fossiles ; Paris, Torino, 1840, 4to. fig. — Db Haah(W.), 
1854-56, 8vo. fig. ; partly reprinted MonographisQ Ammoniteomm ei 
from my Catalogue, with additions Goniatiteorum Specimen ; Lugduni- 
and figures. — Buch (L. v.), Ueber Batav., 1825, 8vo. — BuoH (L. t.), 
die Oystideen ; Berlin, 1844, 4to. fig. ; Ueber Ammoniten, iiber ihre Sonder- 
Ak. d. Wiss. — MUller (J.), Ueber ung in Familien, etc ; Berlin, 1832, 
den Bau der Echinodermen ; Berlin, 4to. fig. Ak. d. Wiss. — Ueber Gonio- 
1854, 4to. fig. — BoEMEB (F.), Ueber titen und Clymenien in Schlesien ; 
Stephanocrinus, etc., Wiegm. Arch., Berlin, 1839, 4to. fig. ; Ak. d. WisB. 
1850, p. 365. — Monographic der fos- — Muvsteb (Gb. v.), Ueber Goniati- 
silen Crinoidenfamilie der Blastoi- ten und Planuliten im Uebergmnga- 
deen, etc., Wiegm. Arch., 1851, p. kaik, etc.: Baireuth, 183^ 4to. fig. — 
323. — FoBBES (En.), Echinodermata Yoltz (Ph. L.), ObBervationB but lea 
of the British Tertiaries (Palseont. B^lemnites ; Paris, 1830, 4to. fiff. — 
Soc), 1852, 4to. fig.—- Mem. of the Qitekbtedt (P. A.), De NotiB Nau- 
Gcol. Surv. of the Unit. Kingdom ; tileorum primariis, etc. ; Berolini, 
London, 1849, 8vo. fig., Dec. 1st, 3d, 1834. 8vo. — Crrutacea: Bbohgniabt 
and 4th. — Mollv^ks : Des Hayes (G. (Al.), et Debmabest (A. G.), Histoire 
P.), Trait6 6I6mentaire de Conchy li- naturelle des Trilobites, etc. ; Parii, 
ologie, etc.; Paris, 1835-39, 2 vols. 1822, 4to. fig. — Dalmaw (J. W.), 
8vo. fig. — Description des coquilles Ueber die PalsBaden oder die soge- 
caractcristiques des terrains ; Paris, nannten Trilobiten, a. d. Schwed. ; 
1831, 8vo. fig. — Woodward (S. P.), Niirnberg,1828,4to.fig.— Gbebh(J.), 
A Manual of the Mollusca, etc.; A Monograph of the Trilobitefl of 
London, 1851-54, 12mo. fig. — 11 age- North America, etc. ; Philadelphia, 
NOW (Fr. v.), Die Bryozoen der Maas- 1833, 8vo. fig. — Emmebich (H. F.), 
trichterKreideformation,0assel,1851, De Trilobitis ; Berolini, 1839, 8to. 
4to. fig. — Des Moulins (C), Essai fig. — Zur Naturgeschichte der Tri- 
sur les Sph6rulites, Bull. Soc. Lin. ; lobiten ; Meiningen, 1844, 4to. 
Bordeaux, 1827. — Roquan (O. R. du), — Burmeisteb (11.), Die Organifl»- 
Description des Coquilles fossilles de tion der Trilobiten ; Berlin, 1843, 
la famille des Rudistes, etc., Carcas- 4to. fig. ; (Ray Society.) — Bktbioh 
Sonne, 1841, 4to. fig. — Hoeninqhaus (E.), Ueber einige bOhmische Txilo- 
(Fb. W.), Monographic der Gattung biten ; Berlin, 1845, 4to. ; 2d part, 
Crania, Diisseldorf, 1828, 4to. fig. — 1846, 4to. — Cobda (A. J. C), and 
Bucn (L.V.), Ueber Terebrateln, etc. ; Uawle (Ig.), Prodrom einer Mono- 
Berlin, 1834, 4to. fig. ; Ak.d. Wiss. Ue- flnraphie der bdhmischen Trilobiten; 
bcr Productus und Loptaena ; Berlin, Prag, 1848, 8vo. fig. — Bab&aiidb(J.), 
1842, 4to. fig. ; Ak. d. Wiss.— David- Syst. Sil., q. a., p. 32. — Saltbb (J. 
SON (Th.), British Brachiopoda (Pa- W.),In Mem.Geol. 8unr.,etc.,Dec.8. 
lacont. Soc): London, 1851-55, 4to. — Miinsteb (Gb. G. y.), Beitrilge lur 



SUCCESSION OP ANIMALS AND PLANTS. 147 

In order to be able to compare the order of succession 

of the animals of past ages with some other prominent 

Petrefaktenkunde ; Beyreuth, 1839, liobates, Ibid., 1849, p. 299.— MoCoT 

4to. 2d Faflc., fig.— M*tkb (H. v.), (F.), In Sedgwick and McCoy's Bri- 

Neue Gattungen fossiler Erebse, etc., tisn Palasoz. Bocks, q. a., p. 32. — 

8tattgaii,I840,4to.fig. — DbKonihck Nbwbebby (J. 8.), Fishes of the 

(L.), M^moire sur les Orustac^ fos- Carbonif. Deposits of Ohio, Proc. Ac. 

nles de Belgique ; Li^e, 1841, 4to. Nat. Sc., Philadelphia, 1856. — lUp' 

fig. — CoBNUBL (J.), Description des tiUs: Cuvibb (G.), Bech. Oss. foss., 

^tomostrac^ fossiles, etc., M6m. q. a., p. 75. — Jaeoeb (G. Fb.), Uebcar 

Soc. G6ol. de France, 2de s^r., vol. 1, die fossilen Beptilien welche in Wur- 

part 2d ; Paris, 1846, 4to. fig. — Bos- temberg aufgefunden worden sind, 

QVBT, Description des Entomostrac^ Stuttgurt, 1828, 4to. fig. — Geovvbot 

fossiles de la Craie de Maestricht, St. Hilaibb (£t.), Becherches sur 

M^m. Soc. Boy. de Li^e, 1847, 8to. les grands Sauriens, etc., Paris, 1831, 

— Jones (T. B.), The Entomostraca 4to. fig. — Dbsi.onochamps (£ud.^, 

of the Cretaceous Formation of £ng- M6m. sur le FoecilopUuran Buck- 

land (PalflDont. Soc.) ; London, 1848, Icendi, Caen, 1837, 4to. fig. — Bbonh 

4to. ^g. — Dabwis (Ch.), Fossil Cirri- (H. G.), und Kaup (J. J.), Abhand- 

pedia (PalsDont. Soc.) ; London, 1851 lungen uber die Gavialartigen Bep- 

and 1854, 4to. fig.— /iMwtt.' Bbodib tilien, Stuttgart, 1842, fol. fig.— 

(P. B.), History of the Fossil Insects €k>Li>FT78S (A.), Der Sch&delbau des 

of the Secondary Bocks of England ; Mosasaurus, N. Act. Ac. Nat. Car., 

London, 1845, 8to.— Hbeb (0.), Die 1844, 4to. fig.— Ai<tov (£. d*) und 

Insektenfaunader Tertiiirgebilde ron Bubmbisteb (H.), Der fossile Gayial 

Oeningen und Ton Badeboy : Leip- Ton Boll, Halle, 1854, fol. fig. — Bub- 

Bg, 1853, 4to. fig. — Hebb (0.), et meisteb (H.), Die Labyrinthodonten, 

£^EB y. DBB LivTH (A.), Zwei geo- Berlin, 1850, 4to. fig. — Queitstedt 

logische Yortrftge, etc., N. Denk., (A.), Die Mastodonsaurier sind Ba- 

HelT. Gessellsch; Z&rich, 1852, 4to. trachier, Tubingen, 1850, 4to. fig.— 

— FUhe$ : Aoassiz (L.), Bech. s. les Gibbes (B.W.), A Memoir on Mosa- 

poiss. foss., q. a., p. 81. — Eoebton saurus and three New Genera, etc^ 

(Sib Phil.), A Systematic and Stra- Smithson, Contrib. 1851, 4to. fig. — 

tigraphical Catalogue of the Fossil Meteb (H. y.^ Zur Fauna der Yor- 

Fishes, etc. ; London, 1837, 4to. 2d welt, Die Sauner des Muschelkalkes, 

edit.-~On some new Ganoid Fishes, etc., Frankfurt a. M., 1845-52, foL — 

Proc GeoL Soc. ; London, lY., p. Meteb (H. t), und Plibitinoeb 

183. — On some New Species of Chi- (Th.), Beitr&ge zur Palssontologie 

nueroid Fishes, Ibid., p. 153 and 211, Wurtembergs, Stuttgart, 1844, 4 to. 

and sereral other papers in Trans, fig. — Owen ^B ), Beport on British 

Geol. Soc. Lond. ; Joum. Geol. Soc ; Fossil Beptiles, Brit. Ass. 1839, p. 

Ann.and Maff. Nat. Hist.,and Memoirs 43 ; 1841, p. 60. — Fossil Beptilia of 

of the Geol. Sunr. of the United the London Clay (Palseont. Soc), 

Kingdom. — Pictbt (F. J.), Pois- London, 1849, 4to. fig. (the Chelonia 

sons fossiles du Mt. Liban ; Gendve, with T. Bell.) — Fossil Beptilia of 

1850, 4to. £tt, — Heckel (J. J.), the Cretaceous Formation (Palseont. 

Beitriige sur Eenntniss der fossilen Soc), London, 1851, 4to. fig. — Fossil 

Fische Oesterreichs ; Wien, 1849, Beptilia of the Wealden Formation 

4to. ^g. — Gibbes (R, W.), Mono- (PalsDont. Soc), London, 1852-55, 

graph of the Fossil Squalidss of 4to. fig. — Lea (I.), On a Fossil Sau- 

the United States, Joum. Acad, rian of the New Bed Sandstone, etc., 

Hat. Be, Philadelphia, 1848 and Philadelphia, 1852, 4to. fipr.— Leidt 

1849, 4to. fig. — New Species of My- (Jos.), Description of Extmct Blam- 

L2 



148 ESSAY ON CLASSIFICATION. 

traits of the animal kingdom, it is necessary for me to 
make a few more remarks upon this topic. I can, fortu- 
nately, be veiy brief, as we possess a text-book of Palae- 
ontology, arranged in zoological order, in which every one 
may at a glance see how, throughout all the classes of the 
animal kingdom, the dififerent representatives of each, in 
past ages, are distributed in the successive geological for- 
mations.^ From such a cursory survey it must appear 
that, whHe certain types prevail during some periods, they* 

malia and Chelonia from Nebraska logical Society ; Trans. Zool. So- 

Territory, in D. D. Owen, Qeol. ciety, etc. — Schmeblino (P. C), 

Surv. of Wisconsin, Iowa, Minesota, Recherches sur les ossemens fossilcs 

etc., Philadelphia, 1852, 4to. fig. — descavemesdeLi^ge, Lidge,1833 36, 

On Bathygnathus bortaliSy an ex- 2 vols. 4to. fig.. — Cboizet et Jobebt, 

tinct Saurian, Joum. Ac. Nat. Sc, Recherches sur les ossemens fossiles 

Philad., 1854, 4to. fig. — Description du d^partement du Puy-de-I>6me, 

of Ifi New Species of Crocodile, etc., Paris, 1828, fol. fig. — Meteb (H. v.), 

Ibid., 1851. — Wyman (Jeppb.), On Zur Fauna, etc., q. a. — Die fossilen 

some remains of Batrachian Reptiles Zahne und Knochen, in der Gegend 

discovered in the Coal Formation of von Qeorgensgmilnd, Frankfurt a. 

Ohio, Amer. Joum., 1858, vol. 25, p. M., 1834, 4to.fig. — Jaeobb (G. Fb.), 

158. — Birds: Owen (R), History of Die fossilen Slugethiere Wiirtem- 

British Fossil Mammalia and Birds, bergs, Stuttgardt, 1835-39, fol. fig. 

London, 1844-46, 1 vol. 8vo. fig. — — Falcoiteb (H.), and Cautlbt (P. 

Fossil Birds from the Wealden, T.), Fauna antiqua Sivalensis, etc., 

Joum. Geol. Soc, II., p. 96. — Me- London, 1846, fol. fig. — Gebtais 

moir on the Dinomis, Trans. Zool. (P.), Zoologie et Pal6ontologie fran- 

Soc, vol. 3, p. 3, London, 1844, 4to. caises, Paris, 1848-52, 4to. ^g. — 

fig. — Mammalia: Cdvieb (G.), Oss. MiiLLER (J.) Ueber die fossilen Reste 

foss., q. a. — BucKLAND (W.), Rel. der Zcuglodonten, etc., Berlin, 1849, 

Diluv.,q. a., p. 142. — De Blainville fol. fig. — Le Coktb (J.), On Platy- 

(DucR.), Ostoographie ou Descrip- gonus coinpressus, Mem. Amer. 

tion iconographique compar^c du Acad. Arts and Sc, 1848, 4to. fig. — 

Squelctte, etc., Paris, 1841, et suiv. Wyman (J.), Notice of the Geolo- 

4to. Atlas fol. — Kaup (J. J.) De- gical Position of Castoroides Ohio- 

scriptions d'ossemcns fossiles de ensis, by J. Hall, and an Anatomical 

MammifOrcs inconnus, Darmstadt, Description of the same, Boston 

1 832-30, 4to. fig.— Owen (R.) Odon- Joum. Nat. Hist., 1847, voL 5, p. 

tography, or a Treatise ou the Com- 385, 8vo. fig. — Warren (J. C.) De- 

parative Anatomj of the Teeth, Lon- scription of a Skeleton of the Ifas- 

don, 1840-41, 3 vols. 8vo. fig. — Brit. tO(Io7i, giganteus, Boston, 1852, 4to. 

foss. Mam. and Bird.*», q. a. — The fol. — Leidy (J.), The Ancient Fauna 

Fossil Mammalia of the Voyage of of Nebraska, Smith8on.Contr.,Waj»h- 

II. M. S. Beaole, London, 18.38, 4to. iugton,1852,4to. fig. See also Sec. 22. 

fig. — Description of the Skeleton of * I allude to the classical work of 

an extinct gigantic Sloth, Afglodon Pictet, Trait6 616mentaire de Pale- 

robuHtus. London, 1842, 4to. fig.; ontologie, q. a., a second edition of 

and many papers in Journal of Geo- which is now being published. 



SUCCESSION OF ANIMALS AND PLANTS. 149 

are entirely foreign to others. This limitation is conspi- 
cuous with reference to entire classes among Vertebrata^ 
while, in other types, it relates more to the orders or to 
the families, and extends frequently only to the genera or 
the species. But, whatever be the extent of their range 
in time, we shall presently see that all these types bear, 
as far as the order of their succession is concerned, the 
closest relation to the relative rank of living: animals of 
the same types compared with one another, and to the phases 
of the embryonic growth of these types in the present 
day, and even to their geographical distribution upon the 
present surface of our globe. I will, however, select a few 
examples for further discussion. Among Echinoderms 
the Crinoids are, for a long succession of periods, the only 
representatives of that class; next follow the Starfishes, 
and next the Sea-Urchins, the oldest .of which belong to 
the type of Cidaris and Echinus, followed by the Clypeas- 
troids and Spatangoids. No satisfactory evidence of the 
existence of Holothurias has yet been found. Among 
Crustacea, a comparison of the splendid work of Barrande^ 
upon the Silurian System of Bohemia with the paper of 
Count von Miinster upon the Crustacea of Soleiihofen,^ and 
with the work of Desmarest upon fossil Crabs,^ will at 
once show that, while Trilobites are the only Crustacea of 
the oldest palaeozoic rocks, there is found in the Jurassic 
period a carcinological fauna entirely composed of Ma- 
croura, to which Brachyura are added in the tertiary period. 
The formations intermediate between the older palaeozoic 
rocks and the Jura contain the remains of other Entomo- 
straca, and later of some Macroura also. In both classes 

^ BABBA5DE'sSj8t.Silur.,q.a.,p.32. ^ Desmarest, see Brongniart and 
• Ge. G. v. AliiMSTER, Beitrage Desmarest's Hist. Nat. a, Tril. et 
zur Petrefactcnkunde, q. a., p. 146. Crust., q. a., p. 146. 



150 ESSAY ON CLASSIFICATION. 

the succession of their representatives, in different periods, 
agrees with their respective standing, as determined by 
the gradation of their structure. 

Among plants, we find in the Carboniferous period Ferns 
and Lycopodiaceae prominent;^ in the Triassic period, 
Equisetaceaj^ and Coniferas prevail; in the Jurassic depo- 
sits, Cycadese^ and Monocotyledoneae ; while later only 
Dicotyledonese take the lead.* The iconographic illustra- 
tion of the vegetation of past ages has of late advanced 
beyond the attempts to represent the characteristic fea- 
tures of the animal world in different geological periods.^ 

Without attempting here to characterize this order of 
succession, so much already follows from the facts men- 
tioned, — that, while the material world is ever the same 
through all ages in all its combinations as far back as 
direct investigations can trace its existence, organized 
beings, on the contrary, ever transform these same mate- 
rials into new forms and new combinations. The carbon- 
ate of lime of aU ages is the same carbonate of lime in 
form as well as in composition, as long as it is under the 
action of physical agents only. Let life be introduced 
upon earth, and a Polyp builds its coral out of it, and 
each family, each genus, each species, a different coral, which 
is again different in every successive geological epoch. Phos- 
phate of lime in palaeozoic rocks is the same phosphate as 
when prepared artificially by Man ; but Fishes make their 

* See, above, p. 141. der Vorwelt ; Leipzig, 1841, 4to. fig. 

* SoHiHPER (W. P.), et MouQBOT — Heer(0.), Flora tertiariaHelvetiw, 
(A.) Monographie des Plantes Fos- Wintherthur, 1855, fol. ^g. 

Biles du Gr^-bigarr6 de la chaine ^ Landscapes of the different ffeo- 

dc8 Vosges, Strasb. et Paris, 1840- logical periods are represented in 

43, 4to, fig. Unoer (Fr.), Die Vorwelt in iliren 

* BucKLAND (W.), On the Cyca- verschiedenen Bildungsperioden, 
deoidsD, a Family of Plants found in WieD,fo].(nodate.) These landscapes 
Oolite, etc., Trans. Geol. Soc. Lond. are ideal representations of the vege- 
2d ser. II., p. 395. Unger (Fr.), tation of past ages. 

Chloris protogaea, Beitrage zur Flora 



SUCCESSION OP ANIMALS AND PLANTS. 151 

spines out of it, and every Fish in its own way; Turtles 
their shields. Birds their wings, Quadrupeds their legs, and 
Man, like all other Vertebrates, his whole skeleton; and 
during each successive period in the history of our globe, 
these structures are diflferent in diflferent species. What 
similarity is there between these facts ? Do they not plainly 
indicate the working of diflferent agencies excluding one 
another ? Truly the noble frame of Man does not owe its 
origin to the same forces which combine to give a definite 
shape to the crystal. And what is true of the carbonate 
of lime is equally true of all inorganic substances; they 
present the same characters, in all ages past, as those which 
they exhibit now. 

Let us look upon the subject again in another light, and 
we shall see that the same is also true of the influence of 
all physical causes. Among these agents the most power- 
ful certainly is electricity; the only one to which, though 
erroneously, the formation of animals has ever been directly 
ascribed. The eflfects which it now produces, it has 
alwajrs produced, and produced them in the same manner. 
It has reduced metallic ores and various earthy minerals 
and deposited them in crystalline form, in veins, during 
all geological ages; it has transported these and other 
substances from one point to another, in times past, as we 
may do now in our laboratories under its influence. Eva- 
poration upon the surface of the earth has always pro- 
duced clouds iQ the atmosphere, which, after accumulatiag, 
have been condensed in rain showers in past ages as now. 
Rain-drop marks in the carboniferous and triassic rocks 
have brought to us this testimony of the identity of the 
operation of physical agents in past ages, and remind 
us that what these agents do now they also did in 
the same way in the oldest geological times, and have 



152 ESSAY ON CLASSIFICATION. 

done at all times. Who, in presence of such facts, could 
assume any casual connexion between two series of phe- 
nomena, the one of which is ever obejring the same laws, 
while the other presents at every successive period new 
relations, an ever changing gradation of new combinations, 
leading to a final climax with the appearance of Man ? 
Who does not see, on the contrary, that this identity of 
the products of physical agents in all ages totally dis- 
proves any influence on their part in the production of 
these ever changing beings which constitute the organic 
world, and which exhibit, as a whole, such striking evi- 
dence of connected thoughts ! 



SECTION XXII. 

LOCALIZATION OF TYPES IN PAST AGES. 

The study of the geographical distribution of the ani- 
mals now living upon earth has taught us that every spe- 
cies of animals and plants has a fixed home, and even 
that peculiar t}^cs may be circumscribed within definite 
limits upon the surface of our globe. But it is only re- 
cently, since geological investigations have been carried 
on in remote parts of the world, that it has been ascer- 
tained that this special localization of types extends to 
past ages. Lund for the fii-st time showed that the ex- 
tinct Fauna of the Brazils,^ dui-ing the latest period of a 
piust age, consisted of diflercnt representatives of the very 
same types now prevalent in that continent; and Owen 
has observed similar relations between the extinct Fauna 

^ Lund, (Pr.,) l^^'k P^ I^ra-silicns Afhandl. VIII. ; Kiobenhavn, 1841, 
Dyrcvcrdcu for sidstc Jordomvaclt- 4to. fig., p. (Jl, etc. ; Engl. Abstract, 
niiig. K. Dauske ViJcusk. 8clsk. Auu. aud Mag. vol. 3, p. 422. 



EARLY LOCALIZATION OF TYPES. 153 

of Australia^ and the types now living upon that conti- 
nent. 

If there is any naturalist left who believes that the 
Fauna of one continent may be derived from another por- 
tion of the globe, the study of these facts, in all their beiir- 
ings, may undeceive him. 

It is well known how characteristic the Edentata are 
of the present Fauna of the Brazils, for there is the home 
of the Sloths {Bradypus), the Tatous {Dasypus), the Ant- 
eaters {Mymiecophaga) ; there also have been found those 
extraordinary extinct genera, the Megatherium, the Mylo- 
don, the Megalonx, the Glyptodon, and the many other 
genera described by Dr. Lund and Professor Owen, aU of 
wliich belong to this same order of Edentata. Some of 
these extinct genera of Edentata had also representatives 
in North America during the same geological period,^ thus 
showing that, though limited within a similar area, the 
range of this type has been diflferent in diflPerent epochs. 

Australia, at present almost exclusively the home of 
Marsupials, has yielded also a considerable number of 
equally remarkable species and two extinct genera of that 
type, all described by Owen in a report to the British 
Association in 1 844, and in Mitchell's Expeditions into the 
Interior of Australia. 

How far similar facts are likely to occur in other classes 
remains to be ascertained. Our knowledge of the geo- 
graphical distribution of the fossil remains is yet too frag- 
mentiiry to furnish any further data upon this point. It 
is, how^ever, worthy of remark, that, though the types of 

• 0wE5, (R.,) Od the Geographical Smithson. Contrib. IS.'JS, 4to. fig. — 

Distribution of Extinct Mammalia, Wyman, (J.,) Notice of Fossil Bones, 

Ann. and Mag. Nat. Hist., 1846, vol. etc., Am" Joum. Sc. and A., 2d ser., 

17, p. 197. 1850, vol. 10.— Owen, (R.,) On tho 

' Leidy, (Jos.,) A Memoir on the Megatherium, Trans. Roy. Soc, 1855, 

Extinct Sloth Tribe of North America, II, p. 359 ; 185(), II, p. 571. 



154 ESSAY ON CLASSIFICATION. 

the oldest geological periods had a much wider distribu- 
tion than most recent families exhibit now, some families 
of fishes largely represented in the Devonian system of 
the Old World have not yet been noticed among tiie fossils 
of that period in America, as, for instance, the Cephalas- 
pids, the Dipteri, and the AcanthodL Again, of the many 
gigantic Keptiles of the Triasic and Oolitic periods, none 
are known to occur elsewhere than in Europe ; and this 
can hardly be owing simply to the less extensive distri- 
bution of these formations in other parts of the world, 
since other fossils of the same formations are known from 
other continents. It is more likely that some of them, at 
least, were peculiar to Umited areas of the surface of the 
globe, as, even in Europe, their distribution is not ex- 
tensive. 

Without, however, entering upon debateable ground, it 
remains evident, that, before the establishment of the 
present state of things, peculiar types of animals, which 
were formerly circumscribed within definite limits, have 
continued to occupy the same or similar grounds in the 
present period, even though no genetic connection can be 
assumed between them, their representatives in these dif- 
ferent formations not belonging even to the same genera. 
Such facts are in the most direct contradiction with any 
assumption that physical agents could have had anything 
to do with their origin; for, though their occurrence within 
similar geographical areas might at first seem to favour 
such a view, it must be borne in mind that these beings, 
so localized, are associated with other types, which have a 
much wider range ; and, what is still more significant, 
they belong to diflferent geological periods, between which 
great physical changes have undoubtedly taken place. 
Thus the facts indicate precisely the revei*se of what the 



LIMITATION OF SPECIES IN TIME. 155 

theory assumes : they prove a continued similarity of or- 
ganized beings during successive geological periods, not- 
withstanding the extensive changes in the prevailing 
physical conditions which the coimtry they inhabited may 
have undergone at diflFerent periods. In whatever direc- 
tion this theory of the origin of animals and plants, imder 
the influence of physical agents, is approached, it can no- 
where stand a critical examination. Only the deliberate 
intervention of an Intellect, aeting continuously, accord- 
iBg to one plan, can account for phenomena of this kind. 



SECTION XXIII. 

LIMITATION OF SPECIES TO FABTIGULAB OEOLOOICAL PEBIODS. 

Without entering into a discussion respecting the 
precise limits within which the fact is true, there can no 
longer be any doubt that not only species, but aU other 
groups of animals and plants, as weU as individuals,^ 
have a definite range of duration. The limits of this 
duration, as far as species are concerned, generally coin- 
cide with great changes in the physical conditions of the 
earth's surface ;^ though, strange to say, most of those 
investigators who would ascribe the origin of organized 
beings to the influence of such causes, maintain also that 
species may extend from one period to another, which 
implies that they are not afiected by such changes.^ 

When considering, in general, the limitation of species 

^ Compare Sect. XIX. Bbonn, (H. Q.,) Index palseontologi- 
' Elii db Beaumont, Recherches cus ; Stuttgardt, 1848-49, 3 vols. 8yo. 
BUT quelques tines des Revolutions de — Orbiqkt, (A. J>\) Prodome de Pa- 
la surface du Globe ; Paris, 1830, 1 Iseontologie stratigraphique univer- 
Tol. 8to. selle, etc. ; Paris, 1850, 2 vols. 12mo. 
' For indications respecting the — Morris, (J.,) Catalogue of the 
occurrence of all species of fossil or- British Fossils ; London, 1854, 1 vol. 
ganized beings now known, consult Syo. ; 2d edit., 1854, 1 vol. 8to. 



156 ESSAY ON CLASSIFICATION. 

to particular geological periods, we might very properly 
disregard the question of the simultaneousness of the suc- 
cessive appearance and disappearance of Faunse, as in no 
way affecting the result of the investigation, as long as it 
is universally conceded that there is no species, known 
among the fossils, which extends through an indefinite 
series of geological formations. Moreover, the number of 
the species, still considered as identical in several suc- 
cessive periods, is growing smaller and smaller, in pro- 
portion as they are more closely compared. I have already 
shown, long ago, how widely many of the tertiary species, 
generally considered as identical with living ones, differ 
from them,^ and also how different the species of the same 
family may be in successive subdivisions of the same great 
geological formation.^ Hall has come to the same result, 
in his investigations of the fossils of the State of New 
York.^ Every monograph reduces their number in each 
formation. Thus Barrande, who has devoted so many 
years to the most minute investigation of the Trilobites 
of Bohemia,^ has come to the conclusion that their species 
do not extend from one formation to the other; D'Or- 
bigny^ and Pictet^ have come to the same conclusion for 
the fossU remains of all classes. It may well be said, that, 
as fossil remains are studied more carefully in a zoologic^il 
point of view, the supposed identity of species, in different 
geological formations, gradually vanishes more and more ; 
so that the limitation of species in time, already ascer- 
tained in a general way, by the earlier investigations of 

^ Aqassiz, (L.,) Coquilles tertiaires * Barrande, Sjst^mesilurien, etc., 

repulses ideiitiques avec les espies q. a. ; see, also, my Monographies 

viyantes ; Neuchfitel, 1845, 4to. fig. d'P^chinodermcs, q. a., p. 80. 

* AoASSiz, (L.,) Etudes critiques * D'Orbigny, Paleoutologio Fran- 

8urle8Mollusquesfossiles;Neuchdtel, 9aise, q. a., p. 143. 

1815-40, 4to. lig. « PiCTET, Traito de Pal6oDtologie, 

' Hall, (J.,) Palieontology of the etc., q. a, p. 144, note 2, 
State of New York, q. a, p. 32, note 1. 



LIMITATION OF SPECIES IN TIME. 157 

their remains in successive geological formations, is cir- 
cumscribed, step by step, within narrower, more definite, 
and also more equable periods. Species are truly limited 
in time, as they are limited in space, upon the surface of 
the globe. The facts do not exhibit a gradual disappear- 
ance of a Umited number of species, and an equally gradual 
introduction of an equally limited number of new ones ; 
but, on the contrary, the simultaneous creation and the 
simultaneous destruction of entire faunae, and a coinci- 
dence between these changes in the organic world and 
the great physical changes our earth has undergone. Yet, 
it would be premature to attempt to determine the extent 
of the geographical range of these changes, and stiU more 
questionable to assert their sjuchronism upon the whole 
surface of the globe, in the ocean and upon dry land. 

To form adequate ideas of the great physical changes 
which the surface of our globe has undergone, and the fre- 
quency of these modifications of the character of the earth's 
surface, and of their coincidence with the changes observed 
among the organized beings, it is necessary to study at- 
tentively the works of EKe de Beaumont.^ He, for the 
first time, attempted to determine the relative age of the 
different systems of mountains, and first showed also, that 
the physical disturbances occasioned by their upheaval 
coincided with the successive disappearance of entire 
faunae, and the reappearance of new ones. In his earlier 
papers he recognized seven, then twelve, afterwards fifteen, 
such great convulsions of the globe ; and now he has traced, 
more or less fuUy and conclusively, the evidence that the 
number of these disturbances has been at least sixty, per- 
haps one himdred. But, while the genesis and genealogy 

* Elib de Beaumont, Notice sur (Leop. v.,) Ueber die geognotischen 
Ics syst^mes de Montagnes ; Paris, Sjstcme von Deutschland, Leonbard*s 
1852, 3 vols. 12ino. ; see, also, Bucu, Taschenb., 1824, II, p. 501. 



158 ESSAY ON CLASSIFICATION. 

of our mountain systems have been thus illustrated, palae- 
ontologists, extending their comparisons between the fossils 
of diflferent formations more carefully to all the successive 
beds of each great era, have observed more and more 
marked differences between them, and satisfied themselves 
that faunas also have been more frequently renovated than 
was formerly supposed; so that the general results of 
geology proper and of palaeontology concur in the main to 
prove, that, while the globe has been at repeated intervals, 
and indeed frequently, though after immensely long periods, 
altered and altered again, imtil it has assumed its present 
condition, so also have animals and plants, living upon its 
surface, been again and again extinguished and replaced 
by others, until those now living were called into existence, 
with man at their head. The investigation is not in every 
case sufficiently complete to show everywhere a coinci- 
dence between this renovation of animals and plants and 
the great physical revolutions which have altered the 
general aspect of the globe, but it is already extensive 
enough to exhibit a frequent sjuchronism and correlation, 
and to warrant the expectation that it will, in the end, 
lead to a complete demonstration of their mutual depend- 
ence, not as cause and effect, but as steps in the same pro- 
gressive development of a plan which embraces the physical 
as well as the organic world. 

In order not to misapprehend the facts, and perhaps to 
fall back upon the idea that these changes may have been 
the cause of the differences observed between the fossils of 
different periods, it must be well understood, that, while 
organized beings exhibit, through all geological formarions, 
a regular order of succession, the character of which will 
be more fully illustrated hereafter, this succession has 
been from time to time violently interrupted by physical 



SUCCESSION AND STANDING OF ANIMALS. 159 

disturbances, without any of these altering in any way 
the progressive character of that succession of organized 
beings. Truly this shows that the important, the leading 
feature, of this whole drama, is the development of life,^ 
and that the material world aflfords only the elements for 
its realization. The simultaneous disappearance of entire 
faunae, and the following simultaneous appearance of 
other faunae, show further, that, as all these faunae consist 
in every formation of a great variety of types^ combined 
into natural associations of animals and plants, between 
which there have been definite relations at all times, 
their origin can never be attributed to the limited influ- 
ence of monotonous physical causes, which always act 
in the same way. Here, again, the intervention of a Crea- 
tor is displayed in the most striking manner, in every 
stage of the history of the world. 



SECTION XXIV. 

PABALLELISM BETWEEN THE OEOLOOICAL SUCCESSION OF ANIMALS 
AND PLANTS AND THEIB PBE8ENT BELATIYE STANDING. 

The total absence of the highest representatives of the 
animal kingdom in the oldest deposits forming part of 
the crust of our globe, has naturally led to the very 
general belief that the animals which have existed during 
the earliest period of the history of our earth were inferior 
to those now living, nay, that there is a natural gradation 
from the oldest and lowest animals to the highest now in 
existence.^ To some extent, this is true ; but it is cer- 
tainly not true, that all animals form one simple series 

^ Daha, (J. D.,) Address, q. a., p. p. 35. 
142, note 1. ' See the palseontological works 

' AoASSiz, (L.,) Geol. Times, q. a., quoted in Sect. 21. 



160 ESSAY ON CLASSIFICATION. 

from the earliest times, during which only the lowest 
types of animals were represented, to the last period, 
when Man appeared at the head of the animal crea- 
ttion.^ It has already been shown, (Sect VIL), that 
representatives of all the great types of the animal king- 
dom have existed from the beginning of the creation of 
organized beings. It is not, therefore, in the successive 
appearance of the great branches of the animal kingdom, 
that we may expect to trace a parallelism between their 
succession in geological times and their relative standing 
at present. Nor can any such correspondence be observed 
between the appearance of classes, at least not among 
Eadiata, MoUusks, and Articulata, as their respective 
classes seem to have been introduced simultaneously 
upon our earth, with perhaps the sole exception of the 
Insects, which are not known to have existed before the 
Carboniferous period. Among Vertebrata, however, there 
already appears a certain coincidence, even within the 
limits of the classes, between the time of their intro- 
duction, and the rank which their representatives hold in 
comparison wdth one another. But upon this point more 
hereafter. 

It is only within the limits of the diflferent orders of 
each class, that the parallelism between the succession of 
their representatives in past ages and their respective 
rank in the present period, is decidedly characteristic. 
But if this is trae, it must be at the same time obvious to 
what extent the recognition of this correspondence may 
be influenced by the state of our knowledge of the true 
affinities and natural gradation of living animals, and 
that, until our classifications have become the correct ex- 
pression of these natui^al relations, even the most striking 

^ Aga88IZ, (L.,) Twelve Lect., etc., p. 68 and p. 128. 



SUCCESSION AND STANDING OF ANIMALS. 161 

coincidence with the succession of their representatives in 
past ages may be entirely overlooked On that account, 
it would be presumptuous on my part to pretend that I 
could illustrate this proposition through the whole animal 
kingdom, as such an attempt would involve the assertion 
that I know all these relations ; or that, where there 
exists a discrepancy between the classification and the 
succession of animals, the classification must be incorrect, 
or the relationship of the fossUs incorrectly appreciated. 
I shall, therefore, limit myself here to a general compa- 
rison, which may, however, be sufficient to show that the 
improvements which have been introduced into our systems 
upon purely zoological groimds have nevertheless tended 
to render more apparent the coincidence between the 
relative standing among living animals and the order 
of succession of their representatives in past ages. I have 
lately attempted to show, that the order of Halcyonaria 
among the Polyps, is superior to that of Actinaria ; ^ that 
in this class compound communities constitute a higher 
degree of development, when contrasted with the cha- 
racters and mode of existence of single Polyps, as 
exhibited by the Actinia ; that top-budding is superior to 
lateral budding ; and that the type of Madrepores, with 
their top-animal, or at least with a definite and limited 
number of tentacles, is superior to all other Actinoids, 
If this be so, the prevalence of Actinoids in older geolo- 
gical formations, to the exclusion of Halcyonoids, the 
early prevalence of Astrseoids, and the very late intro- 
duction of Madrepores, at once exhibits a correspond- 
ence between the rank of the living Polyps and the 
representatives of that class in past ages, though we can 

1 For classification of Polyps, see and Aqassiz, (L.,) Classification of 
Dana, q. a., p. 44, note 1 ; also Polyps, Proc. Am. Acad. Sc. and 
Milvs-£dwa&D8 and Haime, q. a., Arts, 1856, p. 187. 

M 



162 ESSAY ON CLASSIFICATION. 

hardly expect a very close coincidence in this respect 
between animals whose structure is so simple. The 
prevalence of Kugosa and Tabulata in the oldest deposits^ 
appears in a new light, since it has been known that the 
Tabulata are Hydroids, and not genuine Polyps.^ 

The gradation among the orders of Echinoderms is 
perfectly plain. Lowest stand the Crinoids, next the 
Asterioids, next the Echinoids, and highest the Holo- 
thurioids. Ever since this class has been circumscribed 
within its natural limits, this succession has been con- 
sidered as expressing their natural relative standing, and 
modem investigations respecting their anatomy and 
embryology, however extensive, have not led to any 
important change in their classification, as far as the 
estimation of their rank is concerned. This is also 
precisely the order in which the representatives of this 
class were successively introduced upon the earth in 
past geological ages. Among the oldest formations we 
find pedunculated Crinoids ^ only, and this order remains 
prominent for a long series of successive periods ; next 
come free Crinoids and Asterioids ; next Echinoids,* the 
successive appearance of which, since the Triassic period to 
the present day, coincides also with the gradation of their 
subdivisions, as determined by their structure ; and it 
was not until the present period, that the highest Echino- 
derms, the Holothurioids, assumed a prominent position 
in their class. 

Among Acephala there is no more imcertainty re- 

' See Milne-Edwabds and Haime, System der Asteriden ; Braunschweig, 

q. a., p. 44. 1842, 4to. fig. — MuLLEB, (J.,) UebSr 

' Comp. the notes, pp. 34 and 107. den Bau der Echinodermen ; Berlin, 

' Miller, Crinoids, q. a. — D*Oii- 1864, 4to. — Tiedkman, (Fb.,) Anato- 

BioNY, q. a. — J. IIall, q. a. — Aus- mie der R5hren-Holothurie, des 8ee- 

TiN, q. a., p. 145. igels,etc.; Landshut, 1817,foL fig. — 

^ See the works q. a., p. 145; also, Valentin, (G.,) Anat. du genre Echi- 

MuLLER, (J.,) and Tbosouel, (F. U.,) nus ; Neuch&tel, 1842, 4to. 



SUCCESSION AND STANDING OF ANIMALS. 163 

spceting the relative rank of their living representatives 
than among Echinodenns. Every zoologist acknowledges 
the inferiority of the Bryozoa and the Brachiopods ^ when 
compared with the Lamellibranchiata ; and among these, 
the inferiority of the Monomyaria in comparison with the 
Dimyaria would hardly be denied. Now, if any fact is 
well established in PaJssontology, it is the earlier appear- 
ance and prevalence of Bryozoa and Brachiopods in the 
oldest geological formations, and their extraordinary 
development for a long succession of ages, until Lamel- 
libranchiata assume the ascendancy, which they maintain 
to the fullest extent at present. A closer comparison of 
the different families of these orders might further show 
how close this correspondence is through all ages. 

Of Gasteropoda I have nothing special to say, as every 
palaeontologist is aware how imperfectly their remains 
have been investigated, in comparison with what has been 
done for the fossils of other classes. Yet the Pulmonata 
are known to be of more recent origin than the Bran- 
chifera, and among these the Siphonostomata to have 
appeared later than the Holostoma, and this already 
exhibits a general coincidence between their succession in 
time and their respective rank. 

Our present knowledge of the anatomy of the Nautilus, 
for which science is indebted to the skill of Owen,^ must 

* Obbioitt, (A. d',) Bryozoires, Anatomy of the Terebratula, 1853, 

Ann. Sc. Nat., 3e sdr. 1851, vol. 16, 4to. fig. (Palseont. Soc.) — Buoh, (L. 

p. 292. — Busk, (G.,) Catalogue of v.,) Ueber Terebrateln, q. a., p. 146. 

marine Polyzoa in the collection of — Payidson, (Th.,) Monogr. etc., q. 

the British Museum ; London, 1854. a., p. 146. — Poli (Xav.,) Testacea 

— GuTiER, (0.,) M^moire sur Tanimal utriusque Sicilias, eorumque Historia 

de la Lingule, Ann. Mus. I, p. 69, fig. et Anatomia ; Parmae, 1791-93, 2 vols. 

— YoGT, (0.,) Anatomie der Lingula fol. fig., continued by Delle Chiaje. 

anatina, N. M6m. Soc. Helv. 1843, ' Owen, (R.) Memoir on the Pearly 

VII, 4to. fig.— OwB». (R.,) On the Nautilus ; London, 1832, 4to. fig.— 

Anatomy of the Brachiopoda, Trans. Valbnoiennes, (A.,) Nouvelles Re- 

Zool. Soc., I, 4to. p. 145, fig. — On the cherches anatomiques sur le Nautile. 

M 2 



164 



ESSAY ON CLASSIFICATION. 



satisfy everybody that among Cephalopods the Tetra- 
branchiata are inferior to the Dibranchiata ; and it is not 
too much to say, that one of the first points a collector of 
fossils may ascertain for himself is the exclusive pre- 
valence of the representatives of the first of these types in 
the oldest formations, and the later appearance, about the 
middle geological ages, of representatives of the other 
type, which at present is the most widely distributed.^ 

Of Worms, nothing can be said of importance with 
reference to our inquiry ; but the Crustacea again ex- 
hibit the most striking coincidence. Without entering 
into details, it appears, from the classification of Milne- 
Edwards, that Decapods, Stomapods, Amphipods, and 
Isopods, constitute the higher orders ; whUe Bran- 
chiopods, Entomostraca, Trilobites, and the parasitic 
types, constitute, with Limulus, the lower orders of this 
class.^ In the classification of Dana,^ his first type 
embraces Decapods and Stomapods, the second Am- 
pliipods and Isopods, the third Entomostraca including 
Branchiopods, the fourth CLrripedia, and the fifth Eota- 
toria. Both authors acknowledge, in the main, the same 
gradation ; though they difier greatly in the combination 
of the leading groups, and also in the exclusion, by Milne- 
Edwards, of some types, as the Rotifera, which Burmeistor 
first and then Dana and Leydig, justly, as I believe, united 



C. R., Paris, 1841, 4to. — Macdonald, 
(J. D.,) On the anatomy of NmUilus 
umhilicatusy compared with that of 
Nautilus Po7n2)ihiiSyTrB.uB.Roy. Sc; 
London, 1855, II, p. 277. — Van der 
HoEVEN, (J.,) Beitrag zur Anatomic 
von Xautilus PompiliuSy L., besonders 
des miinulichen Thieres, Arch, fiir 
Naturg., 1857, I, p. 77. — Cuvier, 
(G.,) Momoircs pour servir k THis- 
toirc et k TAnatomic des Mollusques ; 
Paris, 1817, 4to. fig. — Edwards, (II. 



M.,) QUATREFAQES, (Ar. DX,) et 

Blanchard, (£m.) Voyage en Sicile ; 
Paris, 3 vols. 4to. fig., without date. 

^ Some Ammonites, and especi&Hy 
the splendid Crioceras of ^gota, 
described by Valenciennes, exhibit 
plainly a combination of characters 
found separately in Nautilus and in 
Argonauta. 

^ Milne-Edwards, Hist. Nat. des 
Crustac^ ; Paris, 1834-40, 3 Tols. 8to. 

* I)ANA(J.D.),Cru8tacea,q.a.,p.45. 



SUCCESSION AND STANDING OF ANIMALS. 165 

to the Crustacea.^ Now this gradation presents the 
most perfect coincidence with the order of succession of 
Crustacea in past geological ages, even down to their sub- 
divisions into minor groups. Trilobites and Entomostraca 
are the only representatives of the class in palaeozoic 
rocks ; in the middle geological ages there appears a 
variety of Shrimps, among which the Macrouran Decapods 
are prominent, and in the later only the Brachyura, which 
are the most numerous in our days. 

The fragmentary knowledge which we possess of fossil 
Insects does not justify us, yet, in expecting to ascertain 
with any degree of precision the character of their suc- 
cession through all geological formations, though much 
valuable information has already been obtained respecting 
the entomological faunae of several geological periods.^ 

The order of succession of Vertebrata in past ages 
exhibits features in many respects differing greatly from 
the Articulata, MoUusks, and Radiata. Among the latter 
we find the respective classes appearing simultaneously in 
the oldest periods of the history of our earth. Not so 
with the Vertebrata, for though Fishes may be as old tis 
any of the lower classes. Reptiles, Birds, and Mammalia are 
introduced successively in the order of their relative rank 
in their types. Again, the earliest representatives of these 
classes do not always seem to be the lowest ; on the con- 
trary, they are, to a certain extent, and in a certain sense, 
the highest, in as far as they embody characters, which, in 
later periods, appear separately in higher classes (see 
Sect 26), to the exclusion of what henceforth constitutes 
the special character of the lower class. For instance, 

1 Letdio, (Fb.,) R&derthiere, etc., thiere, Zeitsch. f. wiss. Zool. 1856, 

Zeitsch. f. wiss. Zool. 1854, vol. 6, p. vol. 8, p. 162.— Gossb, (Th. H.,) On 

1. — Dana, (J. D.,) Crustacea q. a. — the Structure of the class Rotifcra 

BuBMEiSTER, Noch einige Worte iibor q. a. 
die systematischeStelluDg der R&der- ' User, q. a.; Brodie, q. a., p. 147. 



166 ESSAY ON CLASSIFICATION. 

the oldest known Fishes partake of characters, which, 
at a later time, are exclusively found in Eeptiles, and no 
longer belong to the Fishes of the present day. It may 
be said that the earliest Fishes are rather the oldest 
representatives of the type of Vertebrata than of the class 
of Fishes, and that this class only assumes its proper 
characters after the introduction of the class of Beptilcs 
upon the earth. Similar relations may be traced between 
the Eeptiles and the classes of Birds and Mammalia, 
which they precede. I need only allude here to the 
resemblance of the Pterodactyli to Birds, and to that 
of the Ichthyosauri to certain Cetacea. Yet, through all 
these intricate relations there runs an evident tendency 
towards the production of higher and higher tjrpes, until, 
at last, Man crowns the whole series. Seen, as it were, 
at a distance, so that the mind can take a general survey 
of the whole, and perceive the connection of the successive 
steps, without being bewildered by the details, such a 
series appears like the development of a great conception, 
expressed in proportions so harmonious that every link 
appears necessary to the full comprehension of its mean- 
ing, and yet so independent and perfect in itself, that it 
might be mistaken for a complete whole, and again so 
intimately connected with the preceding and following 
members of the series, that one might be viewed as 
flowing out of the other. What is universally acknow- 
ledged as characteristic of the highest conceptions of 
genius is here displayed in a fullness, a richness, a 
magnificence, an amplitude, a perfection of details, a 
complication of relations, which baffle our skill and 
our most persevering efforts to appreciate aU its beau- 
ties. AVho can look upon such series, coinciding to 
such an extent, and not roiid in them the successive 



SUCCESSION AND STANDING OF ANIMALS. 167 

manifestations of a thought, expressed at different times 
in forms ever new, and yet tending to the same end, 
onwards to the coining of Man, whose advent is already 
prophesied in the first appearance of the earliest Fishes ! 

The relative standing of plants presents a somewhat 
different character from that of animals. Their great 
tjrpes are not built upon plans of structure so strictly 
different; they exhibit, therefore, a more uniform gra- 
dation, from their lowest to their highest types, which 
are not personified in one highest plant, as the highest 
animals are in Man. 

Again, Zoology is more advanced respecting the limi- 
tation of the most comprehensive general divisions than 
Botany, while Botany is in advance respecting the limi- 
tation and characteristics of families and genera. There 
is, on that account, more diversity of opinion among 
botanists respecting the number and the relative rank of 
the primary divisions of the vegetable kingdom, than 
among zoologists respecting the great branches of the 
animal kingdom. While most writers^ agree in admit- 
ting among plants such primary groups as Acotyledones, 
Monocotyledones, and Dicotyledones, imder these or 
other names, others would separate the Gynmosperms 
from the Dicotyledones.2 

It appears to me that this point in the classification of 
the living plants cannot be fully understood without a 
thorough acquaintance with the fossils and their distri- 
bution in the successive geological formations, and that 
this case exhibits one of the most striking examples of 
the influence classification may have upon our appreci- 
ation of the gradation of organized beings in the course of 
time. As long as the Gynmosperms stand among the Dico- 
tyledones, no relation can be traced between the relative 

* €K$ppjEBT, etc., q. »., p. 141. • Ad. BB050iiiA»T,etc.,q.a.,p.l41. 



168 ESSAY ON CLASSIFICATION. 

standiDg of living plants and the order of succession of their 
representatives in past ages. On the contrary, let the true 
affinity of the Gjonnosperms with the Ferns, Equisetacese, 
and especially with the Lycopodiaceae, be fully appreciated, 
and we at once see how the vegetable kingdom has been 
successively introduced upon earth, in an order which 
coincides with the relative position its primary divisions 
bear to one another, in respect to their rank, as deter- 
mined by the complication of their structure. Truly, the 
Gymnosperms, with their imperfect flower, their open 
caq)eLs supporting their polyembryonic seeds in their 
axis, arc more nearly allied to the ananthic Acrophytes 
with their innumerable spores than to either the Mono- 
cotyledones or Dicotyledones ; and if the vegetable king- 
dom constitutes one graduated series, beginning with the 
Cryptogams, followed bytheGynmosperms,and ending with 
the Monocotyledones and Dicotyledones, have we not in 
that series the most striking coincidence with the order of 
succession, as exhi])ited ])y the CVj^ptogams of the oldest 
geological fonnations, especially the Femn, Equisetaceoe, 
and Lycopodiaceae of the Carboniferous period, foDowed 
by the Gymnosperms of the Trias and Jura and the Mono- 
cotyledones of the same formation and the late develop- 
ment of the Dicot}'ledones ? Here, as everywhere, there is 
but one order, one plan in nature. 



SECTION XXV. 

PARALLELISM BETWKEN THE GEOLOGICAL SUCCESSION OP ANIMAI^ 
AND THE EMBRYONIC GROWTH OF THEIR LIVINO REPRE- 
SENTATIVES. 

Sovoral authors have already alluded to the resemblance 
which exists Ik*! ween the young of some of the animals 



SUCCESSION AND DEVELOPMENT OF ANIMALS. 169 

now living and the fossil representatives of the same 
families iq earlier periods.^ But these comparisons have, 
thus far, been traced only iq isolated cases, and have not 
yet led to a conviction, that the character of the suc- 
cession of organized beiags iq past ages is such, in 
general, as to show a remarkable agreement with the 
embryonic growth of animals ; though the state of our 
knowledge in Embryology and Palaeontology now jus- 
tifies such a conclusion. The facts most important to a 
proper appreciation of this point have already been 
considered iq the precediQg paragraph, as far as they 
relate to the order of succession of animals, when com- 
pared with the relative rank of their living representatives. 
In now examining the agreement between this succession 
and the phases of the embryonic growth of living animals, 
we may, therefore, take for granted that the order of suc- 
cession of their fossil representatives is sufficiently present 
to the mind of the reader to aflford a satisfactory basis of 
comparison. Too few Corals have been studied embryo- 
logically to furnish extensive means of comparison ; yet 
so much is known,^ that the young poljrp, when hatched, 
is an independent, simple animal, that it is afterwards 
incased in a cup, secreted by the foot of the actinoid 
embryo, which may be compared to the external wall of 
the Rugosay^ and that the polyp gradually widens until 
it has reached its maximum diameter, prior to budding or 
dividing; while in ancient Corals this stage of enlarge- 
ment seems to last during their whole life, as, for example, 

^ Agassiz (L.), Poiss. foes., q. a., ' I haye ascertained these facts 

p. 81. Embryonic Types, q. a., p. 14. from the inyestigation of several 

Twelve Lect., etc., p. 8. — Edwarbs corals of the reef of Florida, especi- 

(H. Milne,) Con6id6rations sur quel- ally of the genera Pontes, Astrsea 

ques principes relatifs h la Classifica- and Manicina. 

tion naturelle des Animaux, Ann. Sc. ' Milne-Edwards et Uaim e, q. a., 

Nat., 3e ser., 1844, 1 vol., p. 65. p. 44. 



170 



ESSAY ON CLASSIFICATION. 



in the Cyathophylloids.^ None of the ancient Corals 
form those large communities, composed of myriads of 
united individuals, so characteristic of our coral reefe ; on 
the contrary, the more isolated and more independent 
character of the individual polyps of past ages presents a 
striking resemblance to the isolation of young Corals, in 
all the living types. In no class, however, is there so much 
to learn still, as in the Polyps, before the correspondence 
of their embryonic growth, and their succession in time, 
can be fully appreciated. In this connection I would 
also remark, that, among the lower animals, it is rarely 
observed that any one, even the highest type, represents 
in its metamorphoses all the stages of the lower types, 
either in their development, or in the order of their 
succession ; and that frequently the knowledge of the 
embryology of several tj^es of diflFerent standing is 
requisite to ascertain the connection of the whole series 
in both spheres. 

No class, as yet, affords more complete and more 
beautiful evidence of the correspondence of their embry- 
onic changes with the successive appearance of their 
representiitives in gast ages than the Echinoderms, thanks 
to the extensive and patient investigations of J. Miiller 
upon the metamorphoses of these animals.^ Prior to the 
publication of his papers, the metamorphosis of the Euro- 



^ Since I have ascertained that the 
Tabulata are Hydroids and not Po- 
lyps, I have had my doubts respecting 
the real affinities of the Rugosa. The 
tendency to a quadripartite arrange- 
ment of their septa indicates unques- 
tionably a nearer relation to Aca- 
Icphs than to Polyps. Moreover, 
their successive floors are different 
from the interseptal floors of the true 
Polyps, and resemble those of the 
Tabulata. It may be, therefore, that 



their true affinity is rather with the 
Acalephs than with the Poljps, and 
that the family of Lucemarut is a 
living representative of that type, 
but without hard parts. In this case 
the foot-secretion of the Actinoids 
would only indicate a typical resem- 
blance between Polyps and Acalephs, 
and not constitute an evidence of the 
relative standing of the two types. 

' MiiLLEB (J.), Seven papers, q. a., 
p. 105. 



SUCCESSION AND DEVELOPMENT OF ANIMALS. I7l 

pean Comatula aJone was known. (See Sect. XVIII,p. 105.) 
This had abready shown that the early stages of growth 
of this Echinodenn exemplify the pedunculated Crinoids 
of past ages. I have myself further seen that the succes- 
sive stages of the embryonic growth of Comatula tj^pify, 
as it were, the principal forms of Crinoids which charac- 
terize the successive geological formations. First, it recalls 
the Cistoids of the palaeozoic rocks, which are represented 
in its simple sphseroidal head, next the few-plated Platy- 
crinoids of the Carboniferous period, next the Pentacri- 
noids of the Lias and OoKte with their whorls of cirrhi, 
and finally, when freed from its stem, it stands as the 
highest Crinoid, as the prominent type of the family, in 
the present period. The investigations of Muller upon 
the larvae of all the families of living Asterioids and Echi- 
noids enable us to extend these comparisons to the higher 
Echinodenns also. The first point which strikes the 
observer in the facts ascertained by Muller is the extra- 
ordinary similarity of so many larvae of such different 
orders and different families as the Ophiuroids and Aste- 
rioids, the Echinoids proper and the Spatangoids, and 
even the Holothurioids, all of which end, of course, in re- 
producing their typical peculiarities. Secondly, it is very 
remarkable that the more advanced larval state of Echi- 
noids and Spatangoids should continue to show such great 
similarity that a young Amphidetus hardly differs from a 
young Echinus.^ Finally, not to extend these remarks 
too far, I would only add that these young Echinoids 
(Spatangus as well as Echinus proper) have a general re- 
semblance to Cidaris, on account of their large spines, 
rather than to Echinus proper. Now, these facts agree 

1 Compare J. Miiller's Ist paper, pi. Ill, with pis. IV- VII, and with pis. 
VI and VII, 4th paper. 



1 72 ESSAY ON CLASSIFICATION. 

exactly with what is known of the successive appearance 
of Echinoids in past ages '} their earliest representatives 
belong to the genera Diadema and Cidaris, next come 
true Echinoids, later only Spatangoids. When the em- 
bryology of the Cly3)eastroids is known, it will, no doubts 
afford other links to connect a larger number of the mem- 
bers of this series. 

What is known of the embryology of Acephala, Gaste- 
ropoda, and Cephalopoda, affords but a few data for such 
comparisons. It is, nevertheless, worthy of remark, that, 
while the young Lamdlihranchiata are still in their em- 
bryonic stage of growth, they resemble Brachiopods,^ 
externally at least, more than their own parents, and the 
young shells of all Gasteropods^ known in their embry- 
onic stage of growth being all holostomate, recall the 
oldest types of that class. Unfortunately, nothing is yet 
known of the embryology of the Chambered Cephalopoda, 
which are the only ones found in the older geological for- 
mations, and the changes which the shield of the Dibran- 
chiata undergoes have not been observed, so that no 
comparisons can be established between them and the 
Belemiiites and other representatives of this order in the 
middle and mora recent geological ages. 

Kcspecting Worms, our knowledge of the fossils is too 
fragmentary to lead to any conclusion, even should our 
information of the embryology of these animals be suflSi- 
cient, as a basis for similar comparisons. The class of 
Crustacea, on the contrary, is very instructive in this 
respect ; but, to trace our compaiisons through the whole 
series, it is necessary that we should consider simul- 

* A0A88IZ (L.,) Twel?e Lectures, ' See the works, q. a., p. 110, n. 1, 
q. a., etc., p. 25. especially those rehitiug toNudibrao- 

' See the works, 4. a., p. 110, n 1. chiuta. 



SUCCESSION AND DEVELOPMENT OF ANIMALS. 173 

taneously the embryonic growth of the higher Ento- 
mostraca, such as Limulus, and that of the highest order 
of the class,^ when it will appear, that, as the former 
recall in early life the form and character of the Trilobites, 
so does the young Crab passing through the form of the 
Isopods, and that of the Macrouran Decapod before it 
assumes its tjrpical form as Brachynran, recall the well- 
known succession of Crustacea through the geological 
middle ages and the Tertiary periods to the present day. 
The early appearance of Scorpions, in the Carboniferous 
period, is probably also a fact to the point, i^ as I have 
attempted to show. Arachnoids may be considered as 
exemplifying the chrysalis stage of development of 
Insects ;^ but, for reasons already stated, (Sect. XXIV.), 
it is hardly possible to take Insects into consideration in 
these inquiries. 

In my researches upon fossil Fishes,^ I have pointed 
out at length the embryonic character of the oldest fishes ; 
but much remains to be done in that direction. The 
only fact of importance I have learned of late is that the 
young Lepidosteus, long after it has been hatched, ex- 
hibits, in the form of its tail, characters hitherto only 
known among the fossil fishes of the Devonian system.^ 
It is to be hoped that the embryology of the Crocodile 
will throw some Ught upon the succession of the gigantic 
Reptiles of the middle geological ages, as I shaU show 
that the embryology of Turtles throws light upon the 
fossil Chelonians.^ It is already plain that the embryonic 
changes of Batrachians coincide with what is known of 

* A0AB8IZ (L.,) Twelve Lectures, * Aoassiz (L.,) Lake Superior, etc., 

etc., p. 68. p. 254. 

' Ulassif. of Insects, q. a., page • See my Contributions to the Nat. 

128. Hist, of the United States, vol. i, pp. 

» Poiss. fossiles, q. a., p. 81. 290, 303 and 38G. 



174 ESSAY ON CLASSIFICATION. 

their succession in past ages.^ Fossil Birds are too little 
known, and fossil Mammalia^ do not extend through 
a suflSciently long series of geological formations^ to 
afford many striking points of comparison ; yet, the 
characteristic peculiarities of their extinct genera exhibit 
everywhere indications that their living representatives in 
early life resemble them more than they do their own 
parents. A minute comparison of a young elephant with 
any mastodon will show this most fully, not only in the 
peculiarities of their teeth, but even in the proportion of 
their limbs, their toes, etc. 

It may therefore be considered as a general hct, very 
likely to be more fully illustrated as investigations cover 
a wider ground, that the phases of development of all 
living animals correspond to the order of succession of 
their extinct representatives in past geological times. As 
far as this goes, the oldest representatives of every class 
may then be considered as embryonic types of their 
respective orders or famiUes among the Uving. Pedun- 
culated Crinoids are embryonic types of the Comatuloids, 
the oldest Echinoids embryonic representatives of the 
higher living families, Trilobites embryonic types of Ento- 
mostraca, the Oolitic Decapods embryonic types of our 
Crabs, the Hetcrocercal Ganoids embryonic types of the 
Lepidosteus, the Andrias Scheuckzeri an embryonic proto- 
type of our Batracliians, the Zeuglodonts embryonic 
Sircnidae, the Mastodonts embryonic Elephants, etc. 

To appreciate, however, fully and correctly all these 
relations, it is further necessary to make a distinction 
between embryonic types in general, which represent in 

^ Sec the works, q. a., p. 124, note siz (L.,^ Zo<)lo^ical Character of 
2. Young Mammalia, Proc. Am. Km, 

' Cuv., Oss. foss., q. a.; also, Aoab- Adv. Sc; Cambridge, 1849, p. 86. 



SUCCESSION AND DEVELOPMENT OP ANIMALS. 175 

their whole organization early stages of the growth of higher 
representatives of the same type, and embryonic features 
prevailing more or less extensively in the characters of 
allied genera, as in the case of the Mastodon and Ele- 
phant, and what I would call hypembryonic types, in 
which embryonic features are developed to extremes in 
the further periods of growth, as, for instance, the wings 
of the Bats, which exhibit the embryonic character of a 
webbed hand, as all Mammalia have it at first, but here 
grown out and developed into an organ of flight, or 
assuming in other families the shape of a fin, as in the 
Whale, or the Sea-turtle, in which the close connection of 
the fingers is carried out to another extreme. 

Without entering into further details upon this subject, 
which will be fully illustrated in my Contributions to the 
Natural History of the United States, enough has already 
been said to show that the leading thought which runs 
through the succession of all organized beings in past 
ages is manifested again in new combinations in the 
phases of the development of the living representatives of 
these diflFerent types. It exhibits everywhere the working 
of the same creative Mind, through all times, and upon 
the whole surface of the globe. 



SECTION XXVI. 

FBOFHETIC TYPES AMONG ANIMALS. 

We have seen in the preceding Section, how the em- 
bryonic conditions of higher representatives of certain 
types, called into existence at a later time, are tjrpified, 
as it were, in representatives of the same types which 
have existed at an earlier period. These relations, now 



176 ESSAY ON CLASSIFICATION. 

they are satisfactorily known, may also be considered as 
exemplifying, as it were, in the diversity of animals of an 
earlier period, the pattern upon which the phases of the 
development of other animals of a later period were to be 
established. They now appear like a prophecy in those 
earlier times of an order of things not possible with the 
earlier combinations then prevailing in the animal king- 
dom, but exhibiting in a later period, in a striking manner, 
the antecedent consideration of every step in the grada- 
tion of animals. 

This is, however, by no means the only, nor even the 
most remarkable case, of such prophetic connections be- 
tween facts of different dates. 

Kecent investigations in Palaeontology have led to the 
discovery of relations between animals of past ages and 
those now living, which were not even suspected by the 
founders of that science. It has, for instance, been noticed 
that certain types, which are frequently prominent among 
the representatives of past ages, combine in their struc- 
ture peculiarities which at later periods are only observed 
separately in different, distinct types. Sauroid Fishes 
existed before Reptiles, Pterodactyles before Birds, Ich- 
thyosaiui before Dolphins, etc. 

There are entire families, among the representatives of 
older periods, of neai4y every chiss of animals, which, in 
the state of their perfect development, exemplify such 
prophetic relations, and afford, within the limits of the 
animal kingdom at least, the most unexpected evidence 
that the plan of the whole creation had been maturely 
considered long before it was executed. Such types I 
have for some time past been in the habit of caUing pro- 
phetic types. The Sauroid^ Fishes of the past geological 

^ AoASSiz (L.,) Poiss. foss., vol. 2, part 2. 



PROPHETIC TYPES AMONG ANIMALS. 177 

ages are an example of this kind These Fishes, which 
have preceded the appearance of Reptiles, present a com- 
bination of ichthyic and reptilian characters, not to be 
found in the true members of this class, which form its 
bulk at present. The Pterodactyles^ which preceded 
the class of Birds, and the Ichthyosauri^ which pre- 
ceded the appearance of the Cetacea, are other examples 
of such prophetic types. These cases suffice, for the 
present, to show that there is a real diflFerence between 
embryonic tjrpes and prophetic types. Embryonic types 
are in a measure also prophetic types, but they exemplify 
only the peculiarities of development of the higher repre- 
sentatives of their own types ; while prophetic types 
exemplify structural combinations observed at a later 
period in two or several distinct ty3)es, and are more- 
over not necessarily embryonic in their character, as, for 
example, the Monkeys in comparison with Man ; while they 
may be so, as in the case of the Pinnate, Plantigrade, and 
Digitigrade Camivora, or, still more so, in the case of the 
pedimculated Crinoids.^ 

Another combination is also frequently observed among 
animals, when a series exhibits such a succession as exem- 
plifies a natural gradation, without immediate or necessary 
reference to either embryonic development or succession 
in time, as the Chambered Cephalopods. Such types I 
call progressive types.^ 

Again : a distinction ought to be made between pro- 
phetic types proper and what I would call synthetic types, 
though both are more or less blended in nature. Pro- 
phetic types proper are those, which in their structural 

* OiTTiER (Q.), Oss. fo8s., vol. 5, * AoASSiz (L.), On the Difference 
p. 2. between Progressiye, Embryonic and 

* OvTiER (G.), Oss. fo88., as q. a. Prophetic Types, etc., Proc. Am. Ass. 
» See above, Sect. 25. Adv. Sc.; Cambridge, 1849, p. 4.32. 

N 



178 ESSAY ON CLASSIFICATION. 

complications lean towards other combinations fully rea- 
lized in a later period, while synthetic types are those 
which combine in a well balanced measure features of 
several types occurring as distinct, only at a later time. 
Sauroid Fishes and Ichthyosauri are more distinctly syn- 
thetic than prophetic types, while Pterodactyles have more 
the character of prophetic types; so also are the generaEchi- 
nocrinus with reference to the Echini, Pentremites with re- 
ference to the Asterioids, and Pentacrinus with reference to 
Comatula. Full iQustrations of these diflferent cases will 
yet be needed to render obvious the importance of such 
comparisons ; and I shall not fail to present ample details 
upon this subject in my Contributions to the Natural His- 
tory of the United States, now in course of publication. 
Enough, however, has ah^ady been said to show that the 
character of these relations among animals of past ages, 
compared with those of later periods or of the present 
day, exhibits more strikingly than any other feature of 
the animal kingdom, the thoughtful connection which 
unites all living beings, through all ages, into one great 
system, intimately linked together from beginning to end- 



SECTION XXVII. 

PARALLELISBC BETWEEN THE STRUCTURAL GRADATION OF ANIMALS 

AND THEIR EMBRYONIC GROWTH. 

So striking is the resemblance of the young of higher 
animals to the full-grown individuals of lower tjrpes, that 
it has been assumed l)y many writers that all the higher 
animals pass, during the earlier stages of their growth, 
through phases corresponding to the permanent constitu- 
tion of the lower classes. These suppositions, the results 



RANK AND DEVELOPMENT OF ANIMALS. 179 

of incomplete investigations, have even become the foun- 
dation of a system of philosophy of Nature which repre- 
sents all a.nimals as the different degrees of development 
of a few primitive types.^ These views have been too 
generally circulated of late, in an anonymous work, en- 
titled Vestiges of Creatioriy to require further mention 
here. It has also been shown above (Sect. VIII.) that 
animals do not form such a simple series as would result 
from a successive development. There now, therefore, 
remains only for us to show within what limits the natural 
gradation which may be traced in the different types of 
the animal kingdom,^ corresponds to the changes they 
undergo during tiieir growth, having already considered 
ihe relations which exist between these metamorphoses 
and the successive appearance of animals upon earth, and 
between the latter and the structural gradation or relative 
standing of their living representatives. Our knowledge 
of the complication of structure of all animals is suflBi- 
ciently advanced to enable us to select, almost at random, 
our examples of the correspondence between the structural 
gradation of animals and their embryonic growth, in all 
those classes, whose embryological development has been 
suflSiciently investigated. Yet, in order to show more dis- 
tinctly how closely all the leading features of the animal 
kingdom are combined, whether we consider the compli- 
cation of their structure, or their succession in time, or 
their embryonic development, I shall refer by preference 
to the same tjrpes which I have chosen before for the 
illustration of the other relations. 

^ LAMABCK,q.a., p.36. — Db Mail- LehrbuchderNatur-PhiloBophie,q.a., 

LBT (Pseudon. Telliamed), Entre- p. 24. — The Vestiges of Creation, etc. 

liens d'un Philosophe indien avec un ' See the works quoted from,p.l01- 

missionaire firanfais ; Amsterdam, 126, also MiLNE-£DWARDS,q.a.,p. 169. 

1748, 2 vols. 8vo.--Okbn (Lor), — Thompson, Crinoids, q. a. 

N 2 



180 ESSAY ON CLASSITICATION. 

Among the Ecliinodenn8,we find in the order of Crinoids 
the pedunculated types standing lowest,^ Comatulas highest^ 
and it is well known that the young Comatula is a pedun- 
culated Crinoid, which only becomes free in later life.^ 
J. Mtiller has shown, that, among the Echinoids, even the 
highest representatives, the Spatangoids, diflFer but slightly 
in early youth from the Echinoids, and no zoologist can 
doubt that these are inferior to the former. Among the 
Crustacea, Dana^ has insisted particularly upon the serial 
gradation which may be traced between the diflferent types 
of Decapods, their order being natural from the highest 
Brachyura, through the Anomoura^ the Macroura, the 
Tetradecapods, etc., to the Entomostraca. The Macrouran 
character of the embryo of our Crabs has been ftdly illus- 
trated by Rathke,* in his beautiful investigations upon the 
embryology of the Crustacea. I have further shown that the 
young of the Macroura represent Entomostracan forms, 
some of them having even been described as represen- 
tatives of that order.^ The correspondence between the 
gradation of Insects and their embryonic growth I have 
illustrated fully in a special paper.^ Similar comparisons 
have been made in the class of Fishes ;^ in that of ReptDes 
we find the most striking examples of this kind among 
Batrachians^ (see above, Sect. XII.) ; in the Birds,^ the uni- 
formly webbed foot of all the young, exhibits another cor- 
respondence between the young of higher orders and the 
permanent character of the lower ones. In the order of 

* MuLLER (J.), Ueber P^ntacrinus * Rathke, q. a., p. 119. 

Caput MedusaB ; Berlin, 1833, 4to., ' Twelve Lectures, etc., p. 67. 

Ak. d. Wiss. « Classification of Insects, q. a. 

^ Forbes (Ed ), History of British ' Poissons fossiles, q. a. 

Starfishes; London, 1851, 1 vol. 8vo., " Twelve Lectures, etc., p. 8. 

p. 10. * Aqassiz (L.), Lake Superior, etc., 

' Dana, q. a., p. 45. — Burmeister, p. 194. 
Cirri peds, q. a., p. 119. 



GRADATION, GROWTH, SUCCESSION, DISTRIBUTION. 1 81 

Camivora, the Seals, the Plantigrades, and the Digitigrades 
exemplify the same coincidence between higher and higher 
representatives of the same tjrpes, and the embryonic 
changes through which the highest pass successively. 

No more complete evidence can be needed to show that ' 
there exists throughout the animal kingdom the closest 
correspondence between the gradation of their types and 
the embryonic changes their respective representatives ex- 
hibit throughout. And yet what genetic relation can there 
exist between the Pentacrinus of the West Indies and the 
ComatulsB found in every sea ; what between the embryos 
of Spatangoids and those of Echinoids, and between the 
former and the adult Echinus ; what between the larva of 
a Crab and our Lobsters ; what between the Caterpillar 
of a Papilio and an adult Tinea, or an adult Sphinx ; 
what between the Tadpole of a Toad and our Menobrair=^ 
chus ; what between a young Dog and our Seals, unless it 
be the plan designed by an intelligent Creator ? 



SECTION XXVIII. 

BEUITIOKS BETWEEN THE 8TBUCTUBE, THE EMBBYONIC OBOWTH, 
THE GEOLOGICAL SUCCESSION, AND THE GEOGBAFHIOAL DIS- 
TBIBUTION OF ANIMALS. 

It requires imusual comprehensiveness of view to per- 
ceive the order prevailing in the geographical distribution 
of animals. We need not wonder, therefore, that this 
branch of Zoology is so far behind the other divisions of 
that science. Nor need we wonder at the fact that the 
geographical distribution of plante is so much better 
known than that of animals, when we consider how 
marked a feature the vegetable carpet which covers the 
surface of our ^obe is, when compared with the little 



182 ESSAY ON CLASSIFICATION. 

show animals make almost everywhere. And yet it will, 
perhaps, some day be easier to understand the relations 
existing between the geographical distribution of animals 
and the other general relations prevailing among animals, 
because the range of structural differences is much greater 
among animals than among plants. Even now, some 
curious coincidences may be pointed out, which go far to 
show that the geographical distribution of animals stands 
in direct relation to their relative standing in their re- 
spective classes, and to the order of their succession in 
past geological ages, and more indirectly also to their em- 
bryonic growth. 

Almost every class has its tropical families^ and these 
stand generally highest in their respective classes ; or 
when the contrary is the case, when they stand evidently 
upon a lower level, there is some prominent relation be- 
tween them and the prevailing types of past ages. The 
class of Mammalia affords striking examples of these two 
kinds of connection. In the first place, the Quadrumana, 
which, next to Man, stand highest in their class, are aU 
tropical animals ; and it is worthy of remark that the two 
highest types of Anthropoid Monkeys, the Orangs of Asia 
and the Chimpanzees of Western Africa, bear, in the colo- 
ration of their skin, an additional similarity to the races 
of Man inhabiting the same regions, the Orangs being 
yellowish red, as the Malays, and the Chimpanzees blackish, 
as the Negroes. The Pachyderms, on the contrary, stand 
low in their class, though chiefly tropical ; but they con- 
stitute a group of animals prominent among the earliest 
representatives of that class in past ages. Among the Chi- 
roptcra the larger, frugivorous representatives are essen- 
tially tropical ; the more omnivorous, on the contrary, 
occur everywhere. Among the Caniivora the largest, most 



GRADATION, GROWTH, SUCCESSION, DISTRIBUTION. 183 

powerful, and also highest types, the Digitigrade, prevail 
in the tropics ; whUe among the Plantigrades, the most 
powerful, the Bears, belong to the temperate and to the 
arctic zone, and the lowest, the Pinnate, are marine species 
of the temperate and arctic seas. Among the Ruminants 
we find the Giraffe and the Camels in the warmer zones, 
the others everywhere. In the class of Birds, the gradation 
is not so obvious as in other classes, and yet the aquatic 
types form by far the most numerous representatives of 
this class in temperate and cold regions, and are almost 
the only ones found in the arctic, while the higher, land 
birds prevail in the warm regions. Among the Reptiles, the 
Crocodilians are entirely tropical ; the largest land Turtles 
are also only foimd in the tropics, and the aquatic repre- 
sentatives of this order, which are evidently inferior to 
their land-kindred, extend much further nortk The Rat- 
tlesnakes and Vipers extend further north and higher up 
the mountains than the Boas and the common harmless 
snakea The same is true of the Salamanders and Tritons. 
The Sharks and Skates are most diversified in the tropics. 
It is also within the tropics that the most brilliant diurnal 
Lepidoptera are foimd, and this is the highest order of 
Insects. Among the Crustacea the highest order, the Bra- 
chyora, are most numerous in the torrid zone ; but 
Dana has shown, what was not at all expected, that they 
nevertheless reach their highest perfection in the middle 
temperate regions.^ The Anomoura and Macroura, on the 
contrary, are nearly equally divided between the torrid 
and temperate zones ; while the lower Tetradecapods are 
far more numerous in extra-tropical latitudes than in the 
tropical The Cephalopods are most diversified within 
the tropics ; yet the Nautilus is a reminiscence of past 

> Dana, Crustacea, p. 1501. 



184 ESSAY ON CLASSIFICATION. 

ages. Among the Gasteropods, the Stromboids belong to 
the tropics; but among the lamellibranchiate Acephala»the 
Naiades, which seem to me to stand very high in their 
class, have their greatest development in the fresh waters 
of North America. The highest Echinoderms, the Holo- 
thurians and Spatangoids, are most diversified within the 
tropics, whUe the Echini, Starfishes, and Ophiurse extend 
to the arctics. The presence of Pentacrinus in the West 
Indies has undoubtedly reference to the prevalence of 
Crinoids in past ages. The Madrepores, the highest among 
the Actinoid Polypi, are entirely tropical; while the 
highest Halcyonoids, Renilla, VeretiUum, and Pennatula, 
extend to the tropics and the temperate zone. 

Another interesting relation between the geographical 
distribution of animals and their representatives in past 
ages, is the absence of embryonic types in the warm 
regions. We find in the torrid zone no true representa- 
tives of the oldest geological periods : Pentacrinus is not 
found before the Lias ; among Cephalopods we find the 
Nautilus, but nothing like Orthoceras ; Limulus, but no- 
thing like Trilobites. 

This study of the relations between the geographical 
distribution of animals and their relative standing is 
rendered more difficult, and in many respects obscure, by 
the circumstance that entire types, characterized by pecu- 
liiir structures, are so strangely limited in their range ; 
and yet, even this shows how closely the geographical dis- 
tribution of animals is connected with their structure. 
Why New Holland should have no Monkeys, no Cami- 
vora, no Ruminants, no Pachyderms, no Edentata, is not 
to be explained ; but that this is the case, every zoologist 
knows, and is further aware that the Marsupials^ of that 

^ See Sect. 11. 



ANIMAL AND VEGETABLE KINGDOMS. 185 

continental island represent, as it were, the other orders 
of Mammalia, under their special structural modifications. 
New Holland appears thus as a continent with the cha- 
racters of an older geological age. No one can fail, there- 
fore, to perceive of how great an interest for Classification 
will be a more extensive knowledge of the geographical 
distribution of animals in general, and of the structural 
peculiarities exhibited by localized types. 



SECTION XXIX. 

MUTUAL DEPENDENCE OF THE ANIMAL AND VEGETABLE KINGDOMS. 

Though it had long been known, by the experiments of 
De Saussure, that the breathing process is very different 
in animals and plants, and that while the former inhale 
atmospheric air and exhale carbonic acid gas, the latter 
appropriate carbon and exhale oxygen, it was not until 
Dimias and Bousingault^ particularly called the attention 
of naturalists to the subject, that it was fully understood 
how direct is the dependence of the animal and vege- 
table kingdoms one upon the other in that respect, or 
rather how the one consumes what the other produces, and 
vice versa, thus tending to keep the balance, which either 
of them singly would disturb to a certain degree. The 
common agricultural practice of manuring exhibits on 
another side the dependence of one kingdom upon the 
other : the undigested particles of the food of animals 
return to the ground to fertilize it for fresh production.^ 
Again, the whole animal kingdom is either directly or 
indirectly dependent upon the vegetable kingdom for its 

^ Dumas, Le^on sur la statique chi- p. 122. 
mique des 6tres organises, Ann. Sc. ' Liebio, Agricultural Chemistry; 
Nat., 2de 86r., vol. 6, p. 33; vol. 17, Animal Chemistry. 



186 



ESSAY ON CLASSIFICATION. 



sustenance, as the herbivorous aninials afford the needful 
food for the carnivorous tribes. We are too far in advance 
of the thac when it ™ «.ppoeed that Worms origii^ted in 
the decay of fruits and other vegetable substances, to need 
here a repetition of what is known respecting the repro- 
duction of these animals. Nor can it be necessary to 
show how preposterous the assumption would be that 
physical agents produced plants first, in order that fix)m 
these a.nimBls might spring forth. Who could have taught 
the physical agents to make the whole animal world de- 
pendent upon the vegetable kingdom ? 

On the contrary, such general facts as those above 
alluded to, show, more directly than any amount of spe- 
cial disconnected facts could do, the establishment of a 
well-regulated order of things, considered in advance ; for 
they exhibit well-balanced conditions of existence, pre- 
pared long beforehand, such as only an intelligent being 
could ordain. 



SECTION XXX. 

PARASITIC ANIMALS AND PLANTS. 

However independent of each other some animals may 
appear, there are yet many which live only in the closest 
connection with their fellow-creatures, and which are 
knowTi only as parasites upon or within them. Such are 
the intestinal Worms, and all the vermin of the skin.^ 
Among plants, the Mistletoe, Orobanche, Rafflesia, and 



^ See above, p. 114, p. 116, note 1, 
and p. 116, notes 1 and 2; see also 
RuPOLPiii (K. A.), Entozoorum sive 
Vcrmium, etc., q. a., p. 46. Bkemser 
(J. 0), Uebcr lebendc Wiirmer im 
lebenden Menschcn; Wien, 1819, 4to. 
— Ddjardin (F.), Hist. Nat. des Hel- 
miuthcs, etc., q. a., p. 45. — Diesino 



(0. M.), Historia Vennium, etc., q. a., 
p. 45. — KUOHEMMBISTEB (Fr.), Die 
in und an dem Kdrper des lebenden 
Menschen Torkommenden Parasiten; 
Leipzig, 1855, Syo. j Engl, bj Lank as- 
ter (Cavendish Society). — Lbdokart 
(H.), Parasiten in Parasitismus, Vie- 
rord's Archiv., 1852. — Robih (Cb.), 



PARASITIC ANIMALS. 187 

many of the OrchideaB, may be quoted as equally remark- 
able examples of parasitism. 

There existe the greatest variety of parasites among 
animals. It would take volimies to describe them and to 
write their history, for their relations to the animals and 
plants upon which they are dependent for their existence 
are quite as diversified as their form and their structure. 

It is important, however, to remark, at the outset, that 
these parasites do not constitute for themselves one great 
division of the animal kingdom. They belong, on the 
contrary, to all its branches ; almost every class has its 
parasites, and in none do they represent one natural order. 
This fact is very significant, as it shows at once that 
parasitism is not based upon peculiar combinations of the 
leading structural features of the animal kingdom, but 
upon correlations of a more specific character. Nor is 
the degree of dependence of parasites upon other organized 
beings equally close. There are those which only dwell 
upon other animals, whUe others axe so closely connected 
with them that they cannot subsist for any length of time 
out of the most intimate relation to the species in which 
they grow and multiply. Nor do these parasites live upon 
one class of a.Tiima]s ; on the contrary, they are found on 
all of them. 

Among the Vertebrata there are few parasites properly 
speaking. None among the Mammalia. Among the Birds 
a few species depend upon others to sit upon their eggs 
and hatch them, as the European Cuckoo, and the North 
American Cowbird. Among Fishes some small Ophi- 
diums (Fierasfers) penetrate into the cavity of the body 
of large Holothuriae in which they dwell.^ Echeneidcs 

Histpire naturcllc des Y4g6taux para- les animaux vivans ; Paris, 1853, 8vo. 
sites qui croissent sur rhomme et sur ^ See above, p. Ill, note I. 



188 



ESSAY ON CLASSIFICATION. 



attach themselves to other fishes, but only temporarily. 
Among the Axticulata the number of parasites is latest. It 
seems to lie in the very character of this type, so remark- 
able for the outward display of their whole organization, 
to include the greatest variety of parasites. And it is 
reaUy among them that we observe the most extraordinary 
combinations of this singular mode of existence. 

Insects in general are more particularly dependent 
upon plants for their sustenance than herbivorous animals 
usually are, inasmuch as most of them are limited to par- 
ticular plants for their whole life, such as the Plant-lice, 
the Coccus, the Gall Insects. In others the larvae only 
are so limited to particular plants, while the larvae of 
others again, such as the Bots, grow and imdergo their de- 
velopment under the skin or in the intestines, or in the 
nasal cavities of other animals. The Ichneumons lay their 
eggs in the larvae of other insects, upon which the young 
larvae prey imtil hatched. Among perfect Insects, there 
are those which live only in community with others, such 
as the Ant-Hill Insects, the Clavigers, the Cleri and the 
Bees. Different kinds of Ants live together, if not as 
parasites one upon another, at least in a kind of servitude. 
Other Insects live upon the bodies of warm-blooded ani- 
mjils, such as the Fleas and Lice, and of these the number 
is legion. Some Hydrachnas are parasitic upon aquatic 
Mollusks.^ 

Among the Crustacea there are Crabs which constantl}^ 



^ NiTZScii (Chr. L.), Darstellung 
der Familien und Gattungen der 
Thierinsekten ; Ilalle, 1818, 8vo. — 
IIayden (C. v.), Versuch einer sys- 
tematischcn Einthcilung der Acari- 
den; Isis, 1826, p. 608. — Ratzen- 
BURO (J. S. C), Die Ichneumoncn der 
Forstinsekten ; Berlin, 1844-52, 3 



vols. 4to., fig. — Clark (Br.), Obser- 
vations on the Qenus Oestrus, Trans. 
Lin. Soc, iii, p. 289, fig. — Koch (C. 
L.), Die Pflanzen-liluse, Aphiden, 
Niirnberg, 1846, 8vo., ng. — Dnofes 
(Ant.), Recherchcs siir 1 ordre des 
Acariens, Ann. Sc. Nat., 2de 86r., 
1834, i, p. 5 ; ii, p. 18, fig. 



PARASITIC ANIMALS. 189 

live in the shells of MoUusks, such as the Pinnotheres of the 
Oyster and MusseL I have found other species upon Sea- 
Urchins {Pinnotheres MdittcB, a new species, upon Mditta 
quinquefora) The Paguri take the shells of Mollusks to 
protect themselves ; while a vast number of Amphipods 
live upon Fishes, attached to their gills, upon their tongue, 
or upon their skin, or upon Starfishes.^ The Cycmius Ceti 
Uves upon the Whale. Some Cirripeds are parasites upon 
the Whales, others upon Corals. In the family of Ler- 
nseans, the females are mostly parasites upon the gills or 
fins or upon the bodies of Fishes, while the males are free. 
Among Worms this mode of existence is still more fre- 
quent, and while some dwell only among Corals, entire 
families of others consist only of genuine parasites ; but 
here again we find the most diversified relations ; for, 
while some are constantly parasitic, others depend only 
for a certain period of their life upon other animals for 
their existence. The yoimg Gordius is a free animal ; it 
then creeps into the body of Insects, and leaves them 
again to propagate ; the yoimg Distoma lives free in the 
water as Cercaria, and spends the remainder of its life in 
other animals ; the Taenia, on the contrary, is a parasite 
through life, and only its eggs pass from one animal into 
the other. But what is most extraordinary in this, as in 
many other intestinal Worms, is the fact, that, while they 
undergo their first transformations in some kind of ani- 
mals, they do not reach their complete development until 
they pass into the body of another higher type, being 
swallowed up by this while in the body of their first host. 
Such is the case with many Filariae, the Taeniae and Bothro- 
cephali These at first inhabit lower Fishes, and these 
Fishes, being swallowed by Sharks or Water Birds, or 

' I have found a new genus of this family upon Asterias helianthoides. 



190 ESSAY ON CLASSIFICATION. 

Mice with their Worms being eaten up by Cats, the para- 
sites living in them undergo their final transfonnation in 
the latter. Many Worms undertake extensive migrations 
through the bodies of other animals, before they reach the 
proper place for their final development.^ 

Among the MoUusks parasites are very few, if any can 
properly be called true parasites, as the hectocotylized 
arm of the males of some Cephalopods living upon their 
own females ;^ as the Gasteropods growing buried in 
Corals,^ and the Lithodomus and a variety of Areas found 
in Corals. Among Radiata there are no parasites, properly 
speaking; some of them only attaching themselves by 
preference to certain plants, while the young of others 
remain connected with their parent, as in all Corals, and 
even among Crinoids, as in the Comatula of Charleston. 

In all these different cases, the chances that physical 
agents may have a share in producing such animals are 
still less than iq the cases of independent animals, for here 
we have, superadded to the very existence of these beings, 
all the complicated circumstances of their peculiar mode 
of existence, and their various connections with other 
animals. Now if it can already be shown, from the mere 
connections of independent animals, that external circum- 
stances cannot be the cause of their existence, how much 
less could such an origia be ascribed to parasites ! It is 
tnio, they have been supposed to originate in the body of 
the animals upon which they live. What, then, of those 
wh(7 enter the body of other animals at a somewhat ad- 

' Soo ul»ovo, J). 114, note 2; Sie- 1858. 

Boi.n, Wftiulcruiiji:, ott\, p. 1 1(>, note I ; ■ See above, p. Ill, note 1, K6lli- 

STKRNSTUUr, (Jencratiou.swechHol, q. ker, Muller, Verany, Voqt, Stee5- 

a., p. ()'.) — Wkini.ani> (P.), The Plan strup, Frontel, etc. 

adopted by Nature for tho Preserva- ' Ruppell (Ed.), M6moiro sur le 

tion of tlio Varioun Spccios of Ilel- jhfmfittis antiguuSyTmis.Soc.SinLah., 

ininthn, Troc. Jiost. Nat. Hist. 800., 1832, i, fig. 



PARASITIC PLANTS. 191 

vanced stage of growth, as the Gordius ? Is it a freak of 
the latter ? Or, what of those which only live upon other 
animals, such as lice ; are they the product of the skin ? Or 
what of those which have to pass from the body of a lower 
into that of a higher animal to undergo their final meta- 
morphosis, and in which this succession is normal ? Was 
such an arrangement devised by the first animal, or im- 
posed upon the first by the second, or devised by physical 
agents for the two? Or, what of those in which the 
females only are parasites ? Had the two sexes a different 
origin 1 Md Jmales and fences i«rhap« originate in 
different ways ? 

I am at a loss to conceive how the origin of parasites 
can be ascribed to physical causes, unless indeed animals 
themselves be considered as physical causes with reference 
to the parasites they nourish ; and if so, why can they not 
get rid of them, as well as produce them, for it cannot be 
supposed, that all this is not done consciously, when 
parasites bear such close structural relations to the various 
types to which they belong ? 

The existence of parasitic animals belonging to so many 
different types of the animal as well as of the vegetable 
kingdom is a fact of deep meaning, which Man himself can- 
not too earnestly consider ; and, while he marvels at the 
fact^ let him take it as a warning for himself with reference 
to his boasted and yet legitimate independence. All rela- 
tions in nature are regulated by a superior wisdom. May 
we only learn in the end to conform, within the limite of 
our own sphere, to the laws assigned to each race ! 



192 ESSAY ON CLASSIFICATION. 

SECTION XXXI. 

COMBINATIONS IN TIMB AND 8PACB OF TABIOTTS KINDS OF 

BELATI0N8 AMONG ANIMALS. 

It must occur to every reflecting mind, that the mutual 
relation and respective parallelism of so many structural, 
embryonic, geological, and geographical characteristics of 
the animal kingdom, are the most conclusive proof that 
they were ordained by a reflective mind, while they pre- 
sent at the same time the side of nature most accessible 
to our intelligence, when seeking to penetrate the relations 
between finite beings and the cause of their existence. 

The phenomena of the inorganic world are all simple, 
when compared to those of the organic world. There is 
not one of the great physical agents, — electricity, mag- 
netism, heat, hght, or chemical affinity, — which exhibits, 
in its sphere, phenomena so comphcated as the simplest 
organized beings ; and we need not look for the highest 
among the latter to find them presenting the same phy- 
sical phenomena as are manifested in the material world, 
besides those which are exclusively peculiar to them. 
When, then, organized beings include everything the 
material world contains, and a great deal more that is 
peculiarly their own, how could they be produced by 
physical causes, and how can the physicists, acquainted 
with the laws of the material world, and who acknowledge 
that these laws must have been established at the begin- 
ning, overlook that a fortiori the more complicated laws 
which regulate the organic world, of the existence of which 
there is no trace for a long period upon the surface of the 
earth, must have been established, later and successively, 
at the time of the creation of the successive types of ani- 
mals and plants ? 



COMBINATION OF RELATIONS. 193 

Thus far we have been considering chiefly the contrasts 
existing between the organic and inorganic worlds.^ At 
this stage of our investigation it may not be out of place 
to take a glance at some of the coincidences which may 
be traced between them, especially as they afford direct 
evidence that the physical world has been ordained in 
conformity with laws which obtain also among living 
beings, and disclose, in both spheres equally plainly, the 
workings of a reflective mind. It is weU known, that the 
arrangement of the leaves in plants ^ may be expressed by 
very simple series of fractions, all of which are gradual 
approximations to, or the natural means between ^ or ^, 
which two fractions are themselves the maximum and the 
TniTiinriiiTn divergence between two single successive leavea 
The normal series of fractions which expresses the various 
combinations most frequently observed among the leaves 
of plants, is as follows : h J, f, f , i^, /r> H> H> etc. 
Now, upon comparing this arrangement of the leaves in 
plants with the revolutions of the members of our solar 
system, Pierce has discovered the most perfect identity 
between the fundamental laws which regulate both; as 
may be at once seen by the following diagram, in which 
the first column gives the names of the planets, the second 
column indicates the actual time of revolution of the suc- 
cessive planets, expressed in days, the third column the 
successive times of revolution of the planets, which are 
derived from the hypothesis that each time of revolution 
shoidd have a ratio to those upon each side of it, which 
shall be one of the ratios of the law of phyUotaxis ; and 
the fourth column, finally, gives the normal series of frac- 
tions expressing the law of the phyUotaxis. 

» Compare Sects. 24, 25, 26, 27, 28, 24, note 3.— Wright (C), Od the 
29, and 30. PhyUotaxis, Astr. Journ., vol. 5, Dec. 

' See the works quoted above, p. 1856. 

O 



194 



ESSAY ON CLASSIFICATION. 



Neptono . 


. 60,129 . 


62,000 




Uranus 


, 30,687 . 


31,000 


. . i 


Saturn 


. 10,769 . 


10,333 


• • i 


Jupiter 


4,333 . 


4,133 


6 


Asteroids . 


1,200 to 2,000 


1,660 


8 


Mars 


687 . 


696 


• • A 


FArth 


365 . 


866 


:SK 


Venus 


225 . 


227 


Mercury . 


88 . 


87 


• • H 



In this series the Earth forms a break ; but this appa- 
rent irregularity admits of an easy explanation. The 
fractions, i h f , f, ^t^, -iz, H> etc., as expressing the poei-. 
tion of successive leaves upon an axis, by the short way 
of ascent along the spiral, are identical, as fax as their 
meaning is concerned, with the fractions expressing these 
same positions, by the long way, namely, i, f , ^, |, i^, 
ii, H, etc. 

Let us therefore repeat our diagram in another form, 
the third column giving the theoretical time of revolution. 



Neptune 
Ura;;us 

» 

Saturn 

)> 
Jupiter 

>» 
Asteroids 

Mars 
Earth 
Venus 

» 
Mercury 



1 
1 

X 

1 
1 

f 

A 
b 

b 

I 

8 

h 
h 
if 



62,000 . . 


. 60,129 


62,000 . . 
31,000 . , 




. 30,687 


15,600 . 
10,333 . . 




. 10,769 


6,889 . . 






4,133 . 


4,333 


2,480 . . 




],550 . . 


1,200 


968 . , 




596 . 


687 


366 . . 


365 


227 . . 


225 


140 . . 




87 . 


88 



It ai)peai'S, from this tiiblo, that two inter\'als usually 



COMBINATION OP RELATIONS. 195 

elapse between two successive planets, so that the normal 
order of actual fractions is i> i, f > 8> A* etc., or the frac- 
tions by the short way in phyllotaxis, from which, how- 
ever, the Earth is excluded, while it forms a member of 
the series by the long way. The explanation of this, sug- 
gested by Peirce, is, that, although the tendency to set ojff 
a planet is not sujEcient at the end of a single interval, it 
becomes so strong, near the end of the second interval, 
that the planet is found exterior to the limit of this second 
interval Thus, Uranus is rather too far from the Sun 
relatively to Neptune, Saturn relatively to Uranus, and 
Jupiter relatively to Saturn, and the planets thus formed 
engross too large a proportionate share of material, and 
this is especially the case with Jupiter, Hence, when we 
come to the Asteroids, the disposition is so strong at the 
end of a single interval, that the outer Asteroid is but 
just within this interval, and the whole material of the 
Asteroids is dispersed in separate masses over a wide 
space, instead of being concentrated into a single planet. 
A consequence of this dispersion of the forming agents is, 
that a small proportionate material is absorbed into the 
Asteroids. Hence, Mars is ready for formation so far 
exterior to its true place, that, when the next interval 
elapses, the residual force becomes strong enough to form 
the Earth, after which the normal law is resumed without 
any further disturbance. Under this law, there can be no 
planet exterior to Neptune, but there may be one interior 
to Mercury. 

Let us now look back upon some of the leading fea- 
tures alluded to before, omitting the simpler relations of 
organized beings to the world around, or those of indi- 
viduals to individuals, and consider only the different pa- 
rallel series which we have been comparing when showing, 

o 2 



196 ESSAY ON CLASSIFICATION. 

that, in their respective great tyipes, the phenomena of 
animal hfe correspond to one another, whether we com- 
pare their rank as determined by structural complication 
with the phases of their growth, or with their succession 
in past geological ages ; whether we compare this suc- 
cession with their embryonic growth, or all these different 
relations with each other and with the geographical distri- 
bution of animals upon earth. The same series every- 
where ! ^ These facts are true of all the great divisions of 
the animal kingdom, so far as we have pursued the inves- 
tigation ; and though, for want of materials, the train of 
evidence is incomplete in some instances, yet we have proof 
enough for the establishment of this law of a universal 
correspondence in all the leading features which binds all 
organized beings, of all times, into one great system, in- 
tellectually and intelligibly linked together, even where 
some links of the chain are missing. It requires con- 
siderable familiarity with the subject even to keep in 
mind the evidence ; for, though yet imperfectly imder- 
stood, it is the most briUiant result of the combined intel- 
lectual efforts of himdreds of investigators during half a 
century. The connection, however, between the facts, it 
is easily seen, is only intellectual ; and implies, therefore, 
the agency of Intellect as its first cause. 

And if the power of thinking connectedly is the privi- 
lege of cultivated minds only ; if the power of combining 
different thoughts, and of drawing from them new thoughts, 
is a still rarer privilege of a few superior minds ; if the 
ability to trace simultaneously several trains of thought, is 
such an extraordinary gift, that the few cases in which 

* Compare all the preceding sec- * Aoassiz (L.), Contemplation of 
tions, where every topic is considered Qod in the Kosmos, Christian Exa- 
sepai-atcly. miner, January 1851, Boston. 



COMBINATION OF RELATIONS. 197 

evidence of this kind has been presented have become a 
matter of historical record (Caesar dictating several letters 
at the same time), though they exhibit only the capacity 
of passing rapidly, in quick succession, from one topic to 
another, while keeping the connecting thread of several 
parallel thoughts : if all this is only possible for the 
highest intellectual powers, shall we, by any false argu- 
mentation, allow ourselves to deny the intervention of a 
Supreme Intellect in calling into existence combinations 
in nature, by the side of which all human conceptions are 
child's play 1 

If I have succeeded, even very imperfectly, in showing 
that the various relations observed between animals and 
the physical world, as well as between themselves, exhibit 
thought, it follows that the whole has an Intelligent Au- 
thor ; and it may not be out of place to attempt to point 
out, afl far as^ possible, the difference there may be between 
Divine thinking and human thought. 

Taking nature as exhibiting thought for my guide, it 
appears to me, that, while human thought is consecutive, 
Divine thought is simultaneous, embracing at the same 
time and for ever, in the past, the present, and the future, 
the most diversified relations among hundreds of thou- 
sands of organized beings, each of which may present 
compUcations again, which, to study and understand even 
imperfectly, as for instance, Man himself, Mankind has 
already spent thousands of years. And yet, all this has 
been done by one Mind, must be the work of one Mind 
only, of Him before whom Man can only bow in grateful 
acknowledgment of the prerogatives he is allowed to 
enjoy in this world, not to speak of the promises of a 
future life. 

I have intentionally dismissed many points in my 



198 ESSAY ON CLASSIFICATION. 

argument with mere questions, in order not to extend 
unduly a discussion which is, after all, only accessory to 
the plan of my work I have felt justified in doing so 
because, from the point of view under which my subject 
is treated, those questions find a natural solution, which 
must present itself to every reader. We know what the 
intellect of Man may originate, we know its creative 
power, its power of combination, of foresight, of analysis, 
of concentration; we are, therefore, prepared to recog- 
nize a similar action emanating from a Supreme Intelli- 
gence to a boimdless extent. We need, therefore, not even 
attempt to show that such an Intellect may have origi- 
nated all that which the Universe contains. It is enough 
to demonstrate, that the constitution of the physical 
world, and more particularly the organization of living 
beings in their connection with the physical world, prove 
in a general way, the existence of a Supreme Being, as the 
Author of all things. The task of science is rather to 
investigate what has been done, to inquire, if possible, 
how it has been done, than to ask what is possible for the 
Deity, as we can know that only by what actually exists. 
To attack such a position, those who would deny the 
intervention in nature of a creative mind must show, that 
the cause to which they refer the origin of finite beings is 
by its nature a possible cause, which cannot be denied of 
a being endowed with the attributes we recognize in 
God. Our task is therefore completed, as soon as we have 
proved His existence. It would, nevertheless, be highly 
desirable that every naturalist who has arrived at similiu* 
conclusions should go over the subject anew, from his 
point of view and with particular reference to the special 
field of his investigations ; for thus only can the whole 
evidence be brought out. 



RECAPITULATION. 199 

I foresee already that some of the most striking 
illustrations may be drawn from the morphology of the 
vegetable kingdom, especially from the characteristic suc- 
cession and systematic combination of different kinds of 
leaves in the formation of the foliage and the flowers of 
so many plants, all of which end their development by 
the production of an endless variety of fruits. The in- 
organic world, considered in the same light, would not 
fail to exhibit also unexpected evidence of thought, in 
the character of the laws regulating chemical combina- 
tions, the action of physical forces, the universal attrac- 
tion, etc., etc. Even the history of human culture ought 
to be investigated from this point of view. But I must 
leave it to abler hands to discuss such topics. 

SECTION XXXII. 

BE0AFITT7LATI0N. 

In recapitulating the preceding statements, we may 
present the following conclusions : — 

Ist.^ The connection of aU the known features of nature 
into one system exhibits thought, the most comprehensive 
thought, in limits transcending the highest wonted powers 
of man. 

2d. The simultaneous existence of the most diversified 
types under identical circumstances exhibits thought, the 
ability to adapt a great variety of structures to the most 
uniform conditions. 

3d. The repetition of similar types, under the most 
diversified circumstances, shows an immaterial connection 

^ The numbers inscribed here cor- may at once refer back to the evi- 
respond to the preceding sections, in dencc, when needed, 
the same order, bo that the reader 



200 ESSAY ON CLASSIFICATION. 

between them ; it exhibits thought^ proving directly how 
completely the Creative Mind is independent of the influ- 
ence of a material world. 

4th. The unity of plan in otherwise highly diversified 
types of animals, exhibits thought; it exhibits more 
immediately premeditation, for no plan could embrace 
such a diversity of beings, called into existence at such 
long intervals of time, unless it had been framed in the 
beginning with immediate reference to the end. 

5th. The correspondence, now generally known as 
special homologies, in the details of structure in animals 
otherwise entirely disconnected, down to the most minute 
peculiarities, exhibits thought, and more immediately the 
power of expressing a general proposition in an indefinite 
number of ways, equally complete in themselves, though 
difiering in all their details. 

6th. The various degrees and different kinds of relation- 
ship among animals which can have no genealogical 
connection, exhibit thought, the power of combining 
different categories into a permanent, harmonious whole, 
even though the material basis of this harmony be ever 
changing. 

7th. The simultaneous existence, in the earliest 
geological periods in which animals existed at all, of 
representatives of all the great types of the animal king- 
dom, exhibits most especially thought, considerate thought, 
combining power, premeditation, prescience, omniscience. 

8th. The gradation, based upon complications of struc- 
ture, which may be traced among animals built upon the 
same plan, exhibits thought, and especially the power of 
harmoniously distributing unequal gifts. 

9th. The distribution of some tj^es over the most ex- 
tensive range of the surface of the glolje, while others are 



RECAPITULATION. 201 

limited to particular geographical areas, and the various 
combinations of these types into zoological provinces of 
unequal extent, exhibit thought, a close control over the 
distribution of the earth's surface among its inhabitants. 

lOtL The identity of structure of these types, notwith- 
standing their wide geographical distribution, exhibits 
thought ; that deep thought, which, the more it is scru- 
tinized, seems the less capable of being exhausted, though 
its meaning at the surface appears at once plain and in- 
telligible to every one. 

11th. The community of structure, in certain respects, 
of animals otherwise entirely different, but living within 
the same geographical area, exhibits thought, and more 
particularly the power of adapting most diversified types 
with peculiar structures to either identical or to different 
conditions of existence. 

12tL The connection, by series, of special structures 
observed in animals widely scattered over the surface of 
the globe, exhibits thought, unlimited comprehension, and 
more directly onmipresence of mind, and also prescience, 
as far as such series extend through a succession of geo- 
logical agea 

13th. The relation there is between the size of animals 
and their structure and form, exhibits thought ; it sHows 
that in nature the quantitative differences are as fixedly 
determined as the qualitative ones. 

14tL The independence, in the size of animals, of the 
mediums in which they live, exhibits thought, in establish- 
ing such close connection between elements so influential 
in themselves and organized beings so little affected by 
the nature of these elements. 

15th. The permanence of specific peculiarities under 
every variety of external influences, during each geological 



202 ESSAY ON CLASSIFICATION. 

period, and under the present state of things upon earthy 
exhibits thought : it shows, also, that limitation in time is 
an essential element of aQ finite beings, whUe eternity is 
an attribute of the Deity only. 

1 6th. The definite relations in which animals stand to 
the surrounding world, exhibit thought ; for all animals 
living together stand respectively, on account of their 
very diflFerences, in diflFerent relations to identical con- 
ditions of existence, in a manner which implies a con- 
siderate adaptation of their varied organization to these 
uniform conditions. 

17th. The relations in which individuals of the same 
species stand to one another, exhibit thought, and go far 
to prove the existence in all living beings of an immaterial, 
imperishable principle, similar to that which is generally 
conceded to man only. 

18th. The limitation of the range of changes which 
animals undergo during their growth, exhibits thought ; 
it shows most strikingly the independence of these changes 
of external influences, and the necessity that they should 
be determined by a power superior to these influences. 

19th. The unequal limitation in the average duration 
of the life of individuals in different species of animals, 
exhibits thought ; for, however uniform or however diver- 
sified the conditions of existence may be under which 
animals live together, the average duration of life, in dif- 
ferent species, is unequally limited. It points, therefore, 
at a knowledge of time and space, and of the value of 
time, since the phases of life of different animals arc ap- 
portioned according to the part they have to perform upon 
the stage of the world. 

20th. The return to a definite norm of animals which 
multiply in various ways, exhilnts thought. It shows 



RECAPITULATION. 203 

how wide a cycle of modulations may be included in the 
same conception, without yet departing from a norm ex- 
pressed more directly in other combinations. 

2l8t The order of succession of the different types of 
animals and plants characteristic of the different geo- 
logical epochs, exhibits thought It shows, that, while 
the material worid is identical in itself in all ages, ever 
different types of organized beings are called into exist- 
ence in successive periods. 

22d. The localization of some types of animals upon 
the same points of the surface of the globe, during several 
successive geological periods, exhibits thought, consecutive 
thought ; the operations of a mind acting in conformity 
with a plan laid out beforehand, and sustained for a long 
period 

23d. The limitation of closely allied species to different 
geological periods, exhibits thought ; it exhibits the power 
of sustaining nice distinctions, notwithstanding the inter- 
position of gi^at disturbances by physical revolutions. 

24 th The parallelism between the order of succession 
of animals and plants in geological times and the grada- 
tion among their Uving representatives, exhibit thought ; 
consecutive thought, superintending the whole develop- 
ment of nature from beginning to end, and disclosing 
throughout a gradual progress, ending with the introduc- 
tion of man at the head of the animal creation. 

25th. The parallelism between the order of succession 
of animals in geological times and the changes their living 
representatives undergo during their embryological growth^ 
exhibit thought ; the repetition of the same train of 
thoughts in the phases of growth of living animals and 
the successive appearance of their representatives in 
past ages. 



204 ESSAY ON CJLASSIFICATION. 

26tli. The combination, in many extinct types, of 
characters, which, in later ages, appear disconnected in 
diflferent types, exhibits thought, prophetic thought, fore- 
sight ; combinations of thought preceding their manifestar 
tion in Uving forms. 

27tL The parallelism between the gradation among 
animals and the changes they undergo during their growth, 
exhibits thought, as it discloses everywhere the most inti- 
mate connection between essential features of itTiiTnalft 
which have no necessary physical relation, and can, there- 
fore, not be understood otherwise than as established by a 
thinking being. 

28 th. The relations existing between these different 
series and the geographical distribution of animals, ex- 
hibit thought ; they show the omnipresence of the Creator. 

29th. The mutual dependence of the animal and 
vegetable kingdoms upon each other for their maintenance, 
exhibits thought; it displays the care with which all con- 
ditions of existence, necessary to the maintenance of organ- 
ized beings, have been balanced. 

30tL The dependence of some animals upon others or 
upon plants for their existence, exhibits thought ; it shows 
to what degree the most complicated combinations of 
structure and adaptation can be rendered independent of 
the physical conditions which surroimd them. 

We may sum up the results of this discussion, up to 
this point, in still fewer words : — 

All organized beings exhibit in themselves all those 
categories of structure and of existence upon which a 
natural system may be founded, in such a manner that, 
in tracing it, the human mind is only translating into 
human language the Divine thoughts expressed in nature 
in Uving realities. 



RECAPITULATION. 205 

All these beings do not exist in consequence of the 
continued agency of physical causes, but have made their 
successive appearance upon earth by the immediate inter- 
vention of the Creator. As proof, I may sum up my 
argument in the following manner : 

The products of what are commonly called physical 
agents are everywhere the same (that is, upon the whole 
surface of the globe), and have always been the same 
(that is, during all geological periods) ; while organized 
beings are everywhere diflFerent and have diflFered in aU 
ages. Between two such series of phenomena there can 
be no causal or genetic connection. 

31st The combination in time and space of all these 
thoughtful conceptions exhibits not only thought, it shows 
also premeditation, power, wisdom, greatness, prescience, 
omniscience, providence. In one word, all these facts, in 
their natural connection, proclaim aloud the One Grod, whom 
man may know, adore, and love ; and Natural History 
must, in good time, become the analysis of the thoughts of 
the Creator of the Universe, as manifested in the animal 
and vegetable kingdoms, as well as in the inorganic world. 

It may appear strange that I should have presented the 
preceding disquisition under the title of an " Essay on 
Classification.'* Yet it has been done dehberately. In the 
b^inning of this chapter, I have already stated that 
Classification seems to me to rest upon too narrow a 
foundation when it is chiefly based upon structure. Ani- 
mals are linked together as closely by their mode of de- 
velopment, by their relative standing in their respective 
classes, by the order in which they have made their ap- 
pearance upon earth, by their geographical distribution, 
and generally by their connection with the world in which 
they live, as by their anatomy. All these relations should. 



206 ESSAY ON CLASSIFICATION. 

therefore, be fully expressed in a natural classification ; 
and, though stracture furnishes the most direct indication 
of some of these relations, alwajrs appreciable under every 
circumstance, other considerations should not be neglected, 
which may complete our insight into the general plan of 
creation. 

In characterizing the great branches of the animal 
kingdom, it is not enough to indicate the plan of their 
structure in all its peculiarities ; there are possibilities of 
execution which are at once suggested, to the exclusion of 
others, and which should also be considered, and so fully 
analyzed, that the various modes in which such a plan 
may be carried out shall at once be made apparent. The 
range and character of the general homologies of each 
type should also be illustrated, as well as the general con- 
ditions of existence of its representatives. In character- 
izing classes, it ought to be shown why such groups con- 
stitute a class, and not merely an order or a family ; and, 
to do this satisfactorily, it is indispensable to trace the 
special homologies of all the systems of organs which are 
developed in them. It is not less important to ascertain 
the foundation of all the subordinate divisions of each 
class ; to know how they differ, what constitutes orders, 
what families, what genera, and upon what characteristics 
species are based in every natural division. This we shall 
examine in the next chapter. 



CHAPTER SECOND. 

LEADING QROUPS OF THE EXISTING SYSTEMS 

OF ANIMALS. 



SECTION I. 

OBEAT TYPES OB BBANCHE8 OF THE ANIMAL KINGDOM. 

The use of the terms types, classes, orders, fiamilies, genera 
and species in the sj^tems of Zoology and Botany is so 
universal, that it would be natural to suppose that their 
meaning and extent are well determined and generally 
understood; but this is so far £rom being the case, that it 
may, on the contrary, be said there is no subject in Natu- 
ral History respecting which there exists more uncer- 
tainty, and a greater want of precision. Indeed, I have 
failed to find anywhere a definition of the character of 
most of the more comprehensive of these divisions, while 
the current views respecting genera and species are very 
conflicting. Under these circumstances, it has appeared 
to me particularly desirable to inquire into the foimdation 
of these distinctions, and to ascertain, if possible, how far 
they have a real existence. And, while I hope the results 
of this inquiry may be welcome and satisfactory, I am 
free to confess that it has cost me years of labour to arrive 
at a clear conception of their true character. 

It is a fact so universal, in every sphere of intellec- 
tual activity, that practice anticipates theory, that no 



208 ESSAY op CLASSIFICATION. 

philosopher can be surprised to find that zoologists have 
instinctively adopted natural groups, in the animal and 
vegetable kingdoms, even before the question of the 
character and of the very existence of such groups in 
nature was raised. Did not nations speak, understand, 
and write Greek, Latin, German and Sanscrit, before it 
was even suspected that these languages and so many 
others were akin? Did not painters produce wonders 
with colours, before the nature of light was understood ? 
Had not men been thinking about themselves and the 
world, before logic and metaphysics were taught in 
schools ? Why, then, should not observers of nature have 
appreciated rightly the relationship between animals or 
plants before getting a scientific clue to the classifications 
which they were led to adopt as practical ? 

Such considerations, above all others, have guided and 
encouraged me when seeking for the meaning of all 
these systems, so different one fi-om the other in their 
details, and yet so similar in some of their general fea- 
tures. The history of our science shows how early some 
of the principles, which obtain to this day, have been 
acknowledged by all reflecting naturalists. Aristotle, for 
instance, already knew the principal differences which 
distinguish Vertebrata from all other animals; and his 
distinction of Enaima and Anaima} corresponds exactly 
to that of Vei^ehrata and InvertebrcUa of Lamarck,^ and 
to that of Flesh' and Gut-Animals of Oken,^ and to that of 
Myelaneura and Ganglioneura of Ehrenberg;* and one 
who is at aU familiar with the progress of science at diffe- 
rent periods can but smile at the claims to novelty or 

1 Ilistof. Anim., Lib. I, ch. 5 and 6. ' Naturphilosophie, 3d 6dit.,p.400. 
' Anim. Vert., 2d edit., vol. i, p. * Das Naturreich des Menschen; 
313. a diagram upon a large sheet, folio. 



BRANCHES OF THE ANIMAL KINGDOM. 209 

originality so frequently brought forward for views long 
before current among men. Here, for instance, is one and 
the same fact presented in diflferent aspects; first, by 
Aristotle with reference to the character of the formative 
fluid, next by Lamarck with reference to the general 
frame, — for I will do Lamarck the justice to believe that 
he did not unite the Invertebrata simply because they 
have no skeleton, but because of that something which 
even Professor Owen fails to express,^ and which yet 
exists, — the one cavity of the body in the Invertebrata con- 
taining all organs, — whilst the Vertebrata have one distinct 
cavity for the centres of the nervous system, and another 
for the organs of the vegetative life. This acknowledg- 
ment is due to Lamarck as truly as it would be due to 
Aristotle not to accuse him of having denied the Inverte- 
brata any fluid answering the office of the blood, though 
he calls them Anaima; for he knew nearly as well as 
we now know, that a nutritive fluid moves in their 
body, though that information is generally denied him, 
because he had no correct knowledge of the circulation of 
the blood. 

Again, when Oken speaks of Flesh- Animals, he does 
not mean that Vertebrates consist of nothing but flesh, or 
that the Invertebrates have no muscular fibres; but he 
brings prominently before us the presence, in the former, 
of those masses, forming the main bulk of the body, 
which consist of flesh and bones, as well as of blood and 
nerves, and constitute another of the leading features dis- 
tinguishing Vertebrata and Invertebrata. Ehrenberg pre- 
sents the same relations between the same beings as 
expressed by their nervous system. If we now take the 
expressions of Aristotle, Lamarck, Oken and Ehrenberg 

* Comparat. Anat. of Inv., 2d edit., p. 11. 



210 



£^AY OS CLASSIFICATIOX. 



together, bave we not, as characteiistie of their systems, 
the very words by which erery one distinguishes the most 
prominent features of the body of the higher anitnAlfi^ 
when speaking of blood relations, of blood and bones, or 
of having flesh and nerve \ 

Neither of these observers has probably been conscious 
of the identity of his classification with that of his prede- 
cessors ; nor, indeed, should we consider either of them 
as superfluous, inasmuch as it makes prominent features 
more or less different from those insisted upon by the 
others ; nor ought any one to suppose that with all of 
them the field is exhausted, and that there is no more 
room for new systems upon that very first distinction 
among animals.^ As long as men inquire, they will find 
opportunities to know more upon these topics than those 
who have gone before them, so inexhaustibly rich is nature 
in the innermost diversity of her treasures of beauty, order, 
and intelligence. 

So, instead of discarding all the 8}'stems, which have 
thus far had little or no influence upon the progress of 
science, either because they are based upon principles not 
generally acknowledged or considered worthy of confi- 
dence, I have carefully studied them with the view of 
ascertaining what there may be true in them, fix)m the 
standing-point from which their authors have considered 
the animal kingdom ; and I own that I have often derived 
more information from such a careful consideration than 
I had at first expected. 



> By way of an example, I would 
mention the mode of reproduction. 
The formation of the egg in Verte- 
brata ; its origin, in all of them, in a 
more or less complicated Graafian 
TeHicle, in which it is nursed; the 
formation and development of the 
embryo up to a certain period, etc., 
etc., are so completely different from 



what is observed in any of the InTer- 
tebrata, that the animal kingdom, 
classified according to these facts, 
would again be divided into two great 
^oups, corresponding to the Verte- 
orata and InverUbrata of Lamarck, 
or to the FUth- and Gut- Animals of 
Oken, or the Enaima and Anaima of 
Aristotle, etc. 



BRAl^CHES OF THE ANIMAL KINGDOM. 211 

It was not indeed by a lucky hit, nor by one of those 
unexpected apparitions, which, like a revelation, suddenly 
break upon us and render at once clear and comprehensible 
what has been dark and almost inaccessible before, that I 
came to undeiBtand the meaning of those divisions caJled 
types, classes, orders, families, genera, and species, so long 
admitted in Natural History as the basis of every system, 
and yet so generally considered as mere artificial devices 
to facilitate our studies. For years I had been labouring 
under the impression that they are founded in nature, 
before I succeeded in finding out upon what principle 
they are really based. I soon perceived, however, that 
tiie greatest obstacle in the way of ascertaining their true 
significance lay in the discrepancies among different au- 
thors in their use and application of these terms. Dif- 
ferent naturalists do not call by the same name groups of 
the same kind and the same extent : some call genera 
what others call subgenera ; others call tribes, or even 
families, what are called genera by others ; even the 
names of tribe and family have been appUed by some to 
what others call sub-genera ; some have called families 
what others have called orders ; some consider as orders 
what others have considered as classes ; and there are 
even genera of some authors which are considered as 
classes by others. Finally, in the number and limitation 
of these classes, as weU as in the manner in which they 
are grouped together under general heads, there is found 
the same diversity of opinion. It is nevertheless possible, 
that, under these manifold names, so differently appUed, 
groups may be designated which may be natural, even if 
their true relation to one another have thus far escaped 
our attention. 

It is already certain that most, if not all, investigators 

p2 



212 ESSAY ON CLASSIFICATION. 

agree in the limitation, of some groups at least, under 
whatever name they may call them, and however much 
they would blame one another for calling them so, or 
otherwise. I can, therefore, no longer doubt that the 
controversy would be limited to definite questions, if 
naturalists could only be led to an agreement respecting 
the real nature of each kind of groups. I am satisfied, 
indeed, that the most insuperable obstacle to any exact 
appreciation of this subject lies in the fact, that all na- 
turalists, without exception, consider these divisions, under 
whatever name they may designate them, as strictly sub- 
ordinate one to the other, in such a maimer that their 
difierence is only dependent upon their extent ; the class 
being considered as the more comprehensive division, thfe 
order as the next extensive, the family as more limited, 
the genus as still more limited, and the species as the 
ultimate limitation in a natural arrangement of living 
beings ; so that all these groups would diflfer only by the 
quantity of their characters, and not by the quality, as if 
the elements of structure in animals were all of the same 
kind ; as if the form, for instance, was an organic element 
of the same kind as the complication of structure, and as 
if the degree of comphcation implied necessarily one plan 
of structure to the exclusion of another. I trust I shall 
presently be able to show, that it is to a neglect of these 
considerations that we must ascribe the slow progress 
which has been made in the philosophy of classifica- 
tion. 

Were it possible to show that all these groups do not 
differ in quantity, and are not merely divisions of a wider 
or more limited range, but are based upon different cate- 
gories of characters, genera would be called genera by all, 
whether they differ much or little one from the other, and 



BRANCHES OF THE ANIMAL KINGDOM. 213 

SO would families be called families, orders be called orders, 
etc. C!ould species, for instance, be based upon absolute 
size, genera upon the structure of some external parts of 
the body, families upon the form of the body, orders upon 
the similarity of the internal structure, or the like, it is 
plain that there could not be two opinions respecting 
these groups in any class of the animal kingdom. But, 
as the problem is not so simple in nature, it was not until 
after the most extensive investigations that I obtained the 
clue to guide me through this labyrinth. I knew, for 
instance, that, though naturalists have been disputing, 
and are still disputing, about species and genera, they all 
distinguished the things themselves in pretty much the 
same manner. What A would call a species, B called 
only a variety or a race ; but then B might call a sub- 
genus the very same aggregate of individuals which A 
called a species ; or what A called a genus was considered 
by B as a family or an order. Now it was this something, 
called no matter how, for which I tried to find out such 
characters as would lead all to call it by the same name ; 
thus limiting the practical difficulty in the application of 
the name to a question of accuracy in observation, and 
no longer allowing it to be an eternal contest about mere 
nomenclature. 

At this stage of my investigation, it struck me that the 
character of the writings of eminent naturalists might 
throw some light upon the subject itself. There are au- 
thors, and among them some of the most celebrated con- 
tributors to our knowledge in Natural History, who never 
busied themselves with Classification, or paid only a 
passing notice to this subject, whilst they are, by uni- 
versal consent, considered as the most successful bio- 
graphers of species ; such are Buffon, Reaumur, Roesel, 



214 ESSAY ON CLASSIFICATION. 

Trembley, Smeathman, the two Hubers, Bewick, Wilson, 
Audubon, Naumann, etc. Others have applied themselves 
almost exclusively to the study of genera. Latreille is 
the most prominent zoologist of this stamp ; whilst Lin- 
naeus and Jussieu stand highest among botanists for their 
characteristics of genera, or at least for their early sue- 
cessful attempts af tracing the natui^ limite of genera. 
Botanists have thus far been more successftd than zoolo- 
gists in characterizing natural families, though Cuvier and 
Latreille have done a great deal in that same direction in 
Zoology, whilst Linnaeus was the first to introduce orders 
in the classification of animals. As to the higher groups, 
such as classes and tjrpes, and even orders, we find, 
again, Cuvier leading the procession, in which all the 
naturalists of this century have followed. 

Now, let us inquire what these men have done in 
particular to distinguish themselves especially, either as 
biographers of species or as characterizers of genera, of 
families, of orders, of classes, and of types. And, should 
it appear that in each case they have been considering 
their subject from some particular point of view, it strikes 
me, that, what has been unconsciously acknowledged as 
constituting the particular eminence or distinction of 
these men, might very properly be proclaimed, with 
grateful consciousness of their services, as the charac- 
teristic of that kind of groups which each of them has 
most successfully illustrated ; and I hope every impre- 
judiced naturalist will agree with me in this respect. 

As to the highest divisions of the animal kingdom, first 
introduced by Cuvier under the name of embranchemeiits 
(and which we may well render by the good old English 
word branch), he tells us himself that they are founded 
upon distinct plans of structure, having been cast, as it were, 



BBANCHES OF THE ANIMAL KINGDOM. 215 

in distinct moulds or fonns.^ Now there can certainly be 
no reason why we should not all agree to designate as types 
or branches all such great divisions of the animal kingdom 
as are constituted upon a special plan,^ if we should find 
practicaUy that such groups may be traced in nature. 
Those who may not see them may deny their existence ; 
those who do recognize them may vary in their estimation 
of their natural limits ; but aU can, for the greatest benefit 
of science, agree to call any group which seems to them 
to be founded upon a special plan of structure, a type or 
branch of the animal kingdom ; and, if there are still 
differences of opinion among naturalists respecting their 
limits, let the discussion upon this point be carried on 
with the imderstanding that types are to be characterized 
by different plans of structure, and not by special ana- 
tomical peculiarities. Let us avoid confounding the idea 
of plan with that of complication of structure, even 
though Cuvier himself has made this mistake here and 
there in his classification. 

1 It would lead me too far were I sions, in a somewhat modified sense, 
to consider here the characteristics is found preferable to framing new 
of the different kingdoms of Nature, ones. I trust the value of the fol- 
I maj, however, refer to the work of lowing discussion will be appreciated 
I. Geoffbot St. Hilaibb, Histoire by its intrinsic merit, tested with a 
natureUe g6n6rale des r^gnes organ- willingness to understand what has 
iques (Paris, 1856, 8to.), who has been mj aim, and not altogether by 
discussed this subject recently,though the relative degree of precision and 
I must object to the admission of a clearness with which I may have ex- 
distinct kingdom for Man alone. pressed myself, as it is almost impos- 

' It is almost superfluous for me sible, in a first attempt of this kind, 
to mention here that the terms, plan, to seize at once upon the form best 
ways and means, or manner in which adapted to carry conviction. I wish 
a plan is carried out, complication of also to be understood as expressing 
structure, form, details of structure, my views more immediately with re- 
ultimate structure, relations of indi- ference to the animal kingdom, as I 
viduals, frequently used in the fol- do not feel quite competent to extend 
lowing PH>^ '^^ taken in a some- the inquiry and the discussion to the 
what different sense from their usual vegetable kingdom, though I have 
meaning, as is always necessary when occasionally alluded to it, as far as 
new views are introduced in a sci- my information would permit, 
ence, and the adoption of old expres- 



216 ESSAY ON CLASSIFICATION. 

The best evidence I can produce that the idea of 
distinct plans of structure is the true pivot upon which 
the natural limitation of the branches of the animal 
kingdom must ultimately turn, lies in the fact that every 
great improvement, acknowledged by all as such, which 
these primary divisions have undergone, has consisted in 
the removal from among each, of such groups as had been 
placed with them from other considerations than those of 
a peculiar plan, or in consequence of a want of informa- 
tion respecting their true plan of structure. Let us 
examine this point within limits no longer controvertible. 
Neither Infusoria nor Intestinal Worms are any longer 
arranged by competent naturalists among theRadiata. Why 
they have been removed may be considered elsewhere ; 
but it was certainly not because they were supposed to 
agree in the plan of their structure with the true Eadiata, 
that Cuvier placed them in that division, but simply 
because he allowed himself to depart from his own prin- 
ciple, and to add another consideration, besides the plan 
of structure, as characteristic of Radiata, — the supposed 
absence of a nervous system, and the great simplicity of 
structure of these animals; as if simplicity of execution 
had any necessary connection with the plan of structure. 
Another remarkable instance of the generally approved 
removal of a class from one of the types of Cuvier to 
another, was the transfer of the Cirripeds from among the 
MoUusks to the branch of Articulata. Imperfect know- 
ledge of the plan of structure of these animals was here 
the cause of the mistake, which was corrected without any 
opposition, as soon as they became better known. 

From a comparison of what is here stated respecting 
the different plans of structure characteristic of the pri- 
maiy divisions of the animal kingcom with what I have 



BRANCHES OF THE ANIMAL KINGDOM. 217 

to say below about classes and orders, it will appear more 
fully that it is important to make a distinction between 
the plan of structure and the manner in which that 
plan is carried out, or the degrees of its complication and 
its relative perfection or simplicity. But even after it is 
imderstood that the plan of structure should be the lead- 
ing characteristic of these primary groups, it does not yet 
foUow, without further examination, that the four great 
branches of the animal kingdom, first distinguished by 
Cuvier, are to be considered as the primary divisions 
which Nature points out as fandamental. It will still be 
necessary, by a careful and thorough investigation of the 
subject, to ascertain what these primary groups are ; but 
we shall have gained one point with reference to our 
systems, that, whatever these primary groups, founded 
upon different plans, which exist in nature, may be, when 
they are once defined, or whilst they are admitted as the 
temporary expression of our present knowledge, they 
should be called the branches of the animal kingdom, 
whether they be the Vertebrata, Articulata, MoUusca, and 
Badiata of Cuvier, or the Artiozoaria, Actinozoaria, and 
Amorphozoaria of Blainville, or the Vertebrata and Inver- 
tebrata of Lamarck. The special inquiry into this point 
must be left for a special paper. I will only add, that I 
am daily more satisfied, that, in their general outlines, thQ, 
primary divisions of Cuvier are true to nature, and that 
never did a naturalist exhibit a clearer and deeper insight 
into the most general relations of animals than Cuvier, 
when he perceived, not only that these primary groups are 
founded upon differences in the plan of their structure, 
but also how they are essentially related to one another. 

Though the term tjrpe is generally employed to desig- 
nate the great fundamental divisions of the animal 



218 ESSAY ON CLASSIFICATION. 

kingdom, I shall not use it in future, but prefer the 
term branch of the animal kingdom, because the tenn 
type is employed in too many different acceptations, and 
quite as commonly to designate any group of any kind, 
or any peculiar modification of structure stamped with a 
distinct and marked character, as to designate the primary 
divisions of the animal kingdom. We speak, for instance, 
of specific types, generic types, fanuly types, ordinal types, 
classic types, and also of a typical structure. The use of the 
word type in this sense is so frequent on almost every page of 
our systematic works, in Zoology and in treatises of compara- 
tive anatomy, that it seems to me desirable, in order to avoid 
every possible equivocation in the designation of the most 
important great primary divisions among animals, to call 
them branches of the animal kingdom, rather than types. 
That, however, our systems are more true to nature 
than they are often supposed to be, seems to me to be 
proved by the gradual approximation of scientific men to 
each other, in their results, and in the forms by which 
they express those results. The idea which lies at the 
foundation of the great primary divisions of the animal 
kingdom is, the most general conception possible in con- 
nection with the plan of a definite creation ; these divi- 
sions are, therefore, the most comprehensive of all, and 
properly take the lead in a natural classification, as repre- 
senting the first and broadest relations of the different 
natural groups of the animal kingdom, the general for- 
mula which they each obey. What we call a branch 
expresses, in fact, a purely ideal connection between 
animals, the intellectual conception which unites them in 
the creative thought. It seems to me, that the more we 
examine the true significance of this kind of groups, the 
more we shaU be convinced that they are not founded 



BRANCHES OF THE ANIMAL KINGDOM. 219 

upon material relations. The lesser divisions which suc- 
ceed next are founded upon special qualifications of the 
plan, and differ one from the other in the character of 
these qualifications. Should it be found that the features 
in the animal kingdom, which, next to the plan of struc- 
ture, extend over the largest divisions, are those which 
determine their rank or respective standing, it would 
appear natural to consider the orders as the second most 
important category in the organization of animals. Ex- 
perience, however, shows that this is not the case ; that 
the manner in which the plan of structure is executed 
leads to the distinction of more extensive divisions (the 
classes) than those which are based upon the complica- 
tion of structure (the orders). As a classification can be 
natural only so feu* as it expresses real relations observed 
in nature, it follows, therefore, that classes take the second 
position in a system, immediately imder the branches. 
We shall see below that orders follow next, as they natu- 
rally constitute groups that are more comprehensive 
than families, and that we are not at liberty to invert 
their respective position nor to transfer the name of one 
of these divisions to the other, at our own pleasure, as so 
many naturalists are constantiy doing. 



SECTION II. 

CLASSES OF ANIMALS. 



Before Cuvier had shown that the whole animal king- 
dom is constructed upon four different plans of structure, 
classes were the highest groups acknowledged in the sys- 
tems of Zoology, and naturalists at a very early period imder- 
stood upon what this kind of division should be founded, in 



220 ESSAY ON CliASSlFICATION. 

order to be natural, even though, in practice, they did not 
always perceive the true value of the characters upon 
which they established their standard of relationship. 
Linnaeus, the first expounder of the system of animals, 
already distinguished by anatomical characters the classes 
which he adopted, though very imperfectly; and ever since, 
systematic writers have aimed at drawing a more and 
more complete picture of the classes of animals, based 
upon a more or less extensive investigation of their struc- 
ture. 

Structure, then, is the watchword for the recognition of 
classes, and an accurate knowledge of their anatomy the 
surest way to discover their natural limits. And yet, with 
this standard before them, naturalists have differed, and 
differ greatly stiU, in the limits which they assign to classes, 
and in the number of them which they adopt. It is really 
strange, that, applying apparently the same standard to 
the same objects, the results of their estimation should so 
greatly vary ; and it was this fact which led me to look 
more closely into the matter, and to inquire whether, after 
all, the seeming unity of standard was not rather a fancied 
than a real one. Structure may be considered from many 
points of view : first, with reference to the plan adopted 
in framing it; secondly, with reference to the work to be 
done by it, and to the ways and means employed in 
building it up ; thirdly, with reference to the degrees of 
perfection or complication exhibited, which may differ 
greatly, even though the plan be the same and the ways 
and means employed in carrying out such a plan may 
not differ in the least; fourthly, with reference to the 
form of the whole structure and its parts, which bears no 
necessary relation, at all events no very close relation, to 
the degree of perfection of the structure, or to the man- 



CLASSES OP ANIMALS. 221 

ner in which its plan is executed, or to the plan itself, 
as a comparison between Bats and Birds, between Whales 
and Fishes, or between Holothurians and Worms, may 
easily show ; fifthly and lastly, with reference to its last 
finish, to the execution of the details in the individual 
parts. 

It would not be difficult to show that the differences 
which exist among naturalists in their limitation of classes 
have arisen from an indiscriminate consideration of the 
structure of animals in all these different points of view, 
and an equally indiscriminate application of the results 
obtained, to characterizing classes. Those who have not 
made a proper distinction between the plan of a structure 
and the manner in which that plan is actually executed, 
have either overlooked the importance of the great fun- 
damental divisions of the animal kingdom, or have im- 
duly multiplied the number of these primary divisions, 
basing their distinctions upon purely anatomical consider- 
ations, that is to say, not upon differences in the character 
of the general plan of structure, but upon the material 
development of that plan. Those, again, who have con- 
founded the complication of the structure with the ways 
and means by which life is maintained through any given 
combination of systems of organs, have failed in establish- 
ing a proper difference between class and ordinal charac- 
ters, and have again and again raised orders to the rank 
of classes. For we shall presently see that natural orders 
must be based upon the different degrees of complication 
of structure, exhibited within the limits of the classes, 
while the classes themselves are characterized by the man- 
ner in which the plan of the type is carried out, that is to 
say, by the various combinations of the systems of organs 
constituting the body of the representatives of any of the 



222 ESSAY ON CLASSIFICATION. 

great types of the animal kingdom ; or perhaps, still more 
distinctly, the classes are characterized by the different 
ways in which life is maintained, and the different means 
employed in establishing these ways. An example will 
suffice to show that this distinction implies a marked dif- 
ference between class and ordinal characters. 

Let us compare the Polyps and Acalephs as two classes, 
without allowing ourselves to be troubled by the different 
limits assigned to them by different authors. Both are 
constructed upon the same plan, and belong, on that 
account, to the type of Radiata. In establishing this feet, 
we do not consider the actual structure of these animals, 
whether they have a nervous system or not, whether they 
have organs of the senses or not, whether their muscles 
are striated or smooth, whether they have a solid frame 
or an entirely soft body, whether their alimentary cavity 
has only one opening or two opposite openings, whether 
it has glandular annexes or not, whether the digested 
food is distributed in the body one way or another, 
whether the undigested materials are rejected through 
the mouth or not, whether the sexes arc distinct or not, 
whether they reproduce themselves only by eggs, or by 
budding also, whether they are simple or not : all we 
neecl know, in order to refer them to the branch of 
Radiata, is whether the plan of their structure exhibits a 
general radiated arrangement or not. But, when we 
would distinguish Polyps, Acalephs, and Echinoderms as 
classes, or rather, when we would ascertain what are the 
classes among the Radiata, and how many there are, we must 
inquire into the manner in which tliis idea of radiation, 
which lies at the foundation of their plan of structure, is 
actually expressed in all the animals exhibiting such a 
plan, and we easily find that, while in some (the Polyps) 



CLASSES OF ANIlfALS. 223 

the body exhibits a large cavity, divided by radiating par- 
titions into a number of chambers, into which hangs a sac 
(the digestive cavity,) open below, so as to pour freely the 
digested food into the main cavity, whence it is circulated 
to and fro in all the chambers, by the agency of vibrating 
cilia ; in others, (the Acalephs,) the body is plain and ftdl, 
not to be compared to a hollow sac, traversed only in its 
thickness by radiating tubes, which arise from a central 
cavity, (the digestive cavity,) without a free communica- 
tion with one another for their whole length, etc., etc. ; 
while in others still, (the Echinoderms,) there is a tough 
or rigid envelope to the body, inclosing a large cavity, in 
which are contained a variety of distinct systems of 
organs, etc. 

Without giving here a full description of these classes, 
I only wish to show that what truly characterizes them 
is not the complication of their structure, (for Hydroid 
Medusae are hardly more complicated in their structure 
than Polyps,) but the manner in which the plan of the Ra- 
diata is carried out, the ways in which life is maintained 
in these animals, the means applied to this end : in one 
word, the combinations of their structural elements. But 
the moment we would discern what are the orders of 
these classes, these considerations no longer suffice ; and 
their structure has to be viewed in a different light ; it is 
now the complication of these apparatus which may guide 
us. Actinarians and Halcyonarians among Polyps, as 
orders, are distinguished, the first by having a larger and 
usually indefinite number of simple tentacles, an equally 
large nimiber of internal partitions, etc.; the second by 
having the eight tentacles lobed and complicated, and all 
the parts combined in pairs in definite numbers, etc. ; dif- 
ferences which establish a distinct standing between them 



224 ESSAY ON CLASSIFICATION. 

in their class, and assign to the latter a higher rank than 
to the former. 

It follows, then, from the preceding remarks, that classes 
are to be distinguished by the manner in which the plan 
of their type is executed, by the ways and means by which 
this is done, or, in other words, by the combinations of 
their structural elements ; that is to say, by the combina- 
tions of the different systems of organs building up the 
body of their representatives. We need not consider here 
the various forms under which the structure is embodied, 
nor the ultimate details, nor the last finish which this 
structure may exhibit, as a moment s reflection will con- 
vince any one that neither form nor structural details can 
ever be characteristic of classes. 

There is another point to which I would call attention, 
respecting the characteristics of classes. These great di- 
visions, so important in the study of the animal kingdom, 
that a knowledge of their essential features is rightly con- 
sidered as the primary object of all investigations in com- 
parative anatomy, are generally represented as each exhi- 
biting some essentiid modification of the type to which they 
belong. This view, again, I consider to be a mistaken 
appreciation of the facts, to which Cuvier has already 
called attention, though his warning has remained un- 
noticed.^ There is, in reaUty, no difference in the plan of 
animals belonging to different classes of the same brancL 
The plan of structure of the Polj'ps is no more a modifica- 
tion of that of the Acalephs, than that of the Acalephs or 
Echinoderms is a modification of ihe plan of the Polype; 
the plan is exactly the same in all three. It may be re- 
presented by one single diagram, and may be expressed 
in one single word, radiation ; it is the manifestation of one 

^ Cuvier, lUgii. An., 2d cdif., p. 48. 



CLASSES OF ANIMALS. 225 

distinct, characteristic idea. But this idea is exhibited in 
nature under the most different forms, and expressed in 
different wajrs, by the most diversified combinations of 
structural modifications and in the most varied relations. 
In the innumerable representatives of each branch of the 
animal kingdom, it is not the plan that differs, but the 
manner in which this plan is executed. In the same 
manner as the variations played by a most skilful artist 
upon the simplest tune are not modifications of the tune 
itself^ but only different expressions of the same funda- 
mental harmony, just so neither the classes, nor the orders, 
nor the families, nor the genera, nor the species of any 
great type are modifications of its plan, but only its dif- 
ferent expressions, the different ways in which the funda- 
mental thought embodied in it is manifested in a variety 
of Uving beings. 

In studjring the characteristics of classes we have to 
deal with structural features, while in investigating their 
relations^ to the branches of the animal kingdom to which 
they belong, we have only to consider the general plan, 
the framework, as it were, of that structure, not the 
structure itsel£ This distinction leads to an important 
practical result. Since, in the beginning of this century, 
naturalists have begun, imder the lead of the German 
physiophilosophers, to compare more closely the structure 
of the different classes of the animal kingdom, points of 
resemblance have been noticed between them which had 
entirely escaped the attention of earlier investigators ; 
structural modifications have been identified which at first 
seemed to exhibit no similarity, so much so, that step by 
step these comparisons have been extended over the whole 
animal kingdom, and it has been asserted, that, whatever 
may be the apparent differences in the organization of 

Q 



226 ESSAY ON CLASSIFICATION. 

animals, they should be considered as constructed of parts 
essentially identical This assumed identity of structure 
has been called homology.^ But the progress of science 
is gradually restricting these comparisons within narrower 
limits, and it appears now that the structure of animals is 
homologous only as far as they belong to the same branch, 
so much so, that the study of homologies is likely to 
aflFord one of the most trustworthy means of testing the 
natural limits of any of the great types of the animal 
kingdom. While, however, homologies show the close 
similarity of apparently different structures and the per- 
fect identity of their plan within the same branches of the 
animal kingdom, yet they daily exhibit more and more 
striking differences, both in plan and structure, between 
the branches themselves, leading to the suspicion that 
systems of organs which are generally considered as iden- 
tical in different types, wiU, in the end, prove essentially 
different, as, for instance, the so-called gills in Fishes, 
Crustacea, and MoUusks. 

It requires no great penetration to see already that the 
gills of Ci-ustacea are homologous with the tracheae of 
Insects and the so-called lungs of certain spiders, in the 
same manner as the gills of aquatic MoUusks are homo- 
gous with the so-caUed lungs of our air-breathing snails 
and slugs. Now, until it can be shown that all these 
different respiratory organs are truly homologous, I hold 
it to be more natural to consider the system of respira- 
tory organs in MoUusks, in Articulates, and in Verte- 
brates as essentiaUy different among themselves, though 
homologous within the limits of each type ; and this 
remark I would extend to aU their systems of organs, to 
their solid frame, to their nervous system, to their muscu- 

* See Chap. I, Sect. 5. 



CLASSES OF ANIMALS. 227 

lar sjTstem, to their digestive apparatus, to their circula- 
tion, and to their reproductive organs, etc. It would not 
be difficult to show now that the alimentary canal with 
its glandular appendages, in Vertebrata, is formed in an 
entirely different way from that of Articulates or Mol- 
lusks, and that it cannot be considered as homologous in 
all these types. And if this be true, we must expect 
soon an entire reform of our methods of illustrating com- 
parative anatomy. 

Finally, it ought to be remembered, in connexion with 
the study of classes as well as that of other groups, that 
the amount of difference existing between any two divi- 
sions is nowhere the same. Some features in nature 
seem to be insisted upon with more tenacity than others, 
to be repeated more frequently and more widely, and to 
be impressed upon a larger number of representatives. 
This unequal weight of different groups, so evident every- 
where in the animal kingdom, ought to make us more 
cautious in estimating their natural limits, and pre- 
vent us from assigning an undue value to the differences 
observed between living beings, either by overrating appa- 
rently great discrepancies, or by underrating seemingly 
t riflin g variations. The right path, however, can only be 
ascertained by extensive investigations made with special 
reference to this point. 

Everybody must know that the males and females of 
some species differ much more one from the other than 
many species do, and yet the amount of difference ob- 
served between species is constantiy urged, even without 
a preliminary investigation, as an argument for distin- 
guishing them. These differences, moreover, are not only 
quantitative, they are to a still greater extent also quali- 
tative. In the same manner do genera differ more or less 

Q 2 



228 ESSAY ON CLASSIFICATION. 

one from the other, even in the same family ; and such 
inequality, and not an equable apportionment^ is the nonn 
throughout nature. In classes, it is not only exhibited in 
the variety of their forms* but also, to an extraordinaiy 
extent, in their numbers ; as, for instance, in the class of 
Insects compared with that of Worms or Crustacea. The 
primary divisions of the animal kingdom differ in the 
same manner one from the other. Articulata are by fer 
the most numerous branch of the whole animal kingdom ; 
their number exceeding greatly that of aU other animala 
put together. Such facts are in themselves sufficient to 
show how artificial those classifications must be which 
admit only the same number and the same kind of divi- 
sions for all the types of the animal kingdom. 



SECTION III. 

OBDERS AMONG ANIMALS. 



Great as is the discrepancy between naturalists respect- 
ing the number and limits of classes in the animal king . 
dom, their disagreement in regard to orders and families 
is yet far greater. These conflicting views, however, do 
not in the leiist shake my confidence in the existence of 
fixed relations between animals, determined by thought- 
ful considemtions. I would as soon cease to believe in 
the existence of one God because men worship Him in so 
many difierent ways, or because they even worship gods of 
their ow^i making, as to dLstrast the e\ddence of my own 
senses respecting the existence of a preestablished and 
duly considered system in nature, the arrangement of 
which preceded the creation of all things that exist. 

From the manner in which orders are generally charac- 



OBDERS AMONG ANIMALS. 229 

terized and introduced into our systems, it would seem 
as if this kind of groups were interchangeable with fami- 
lies. Most botanists make no diflFerence at all between 
orders and families, and take almost universally the terms 
as mere synonyms. Zoologists have more extensively ad- 
mitted a difference between them, but whUe some consider 
the orders as superior, others place families higher; others 
admit orders without at the same time diatinguishing 
families, or vice versd introduce families into their classi- 
fication without admitting orders ; others again admit 
tribes as intermediate groups between orders and fami- 
lies. A glance at any general work on Zoology or Botany 
will satisfy the student how utterly arbitrary the systems 
are in this respect. The Regne animal of Cuvier exhibits 
even the unaccountable feature, that while orders and 
famiKes are introduced in some claases.^ only orders are 
noticed in others,^ and some exhibit only a succession of 
genera under the head of their class, without any further 
grouping among them into orders or families.^ Other 
classifications exhibit the most pedantic uniformity of a 
regular succession in each class, of sub-classes, orders, sub- 
orders, families, sub-families, tribes, sub-tribes, genera, 
sub-genera, divisions, sections, and sub-divisions, sub- 
sections, etc., and bear evidence upon their face that they 
are made to suit preconceived ideas of regularity and 



^ In the classes Mammalia, Birds, ' The classes Echinoderms, Aca- 

Beptiles, and Fishes, OuTier mostly lephs, and Infusoria are divided into 

distinguishes families as well as orders, but without families. 

orders. In the class of Mammalia ' Such are his classes of Cephalo- 

some orders number no families, pods, Pteropods, Brachiopods, and 

whilst others are divided into tribes Oirripeds (Cirrhopods). Of the Ce- 

instead of families. In the class of phalopods, he says, however, they 

Gasteropods, Annelids, Intestinal constitute but one order (R^gn. An., 

Worms, and Polyps, some of the vol. 3, p. 11), and p. 22, he caUs them 

orders only are divided into families, a family ; and yet he distinguishes 

while the larger number are not. them as a class, p. 8. 



230 ESSAY ON CLASSIFICATION. 

symmetry in the system, and that they are by no means 
studied from nature. 

To find out the natural characters of orders from the 
study of those features which really exist in nature, I have 
considered attentively the different systems of Zoology in 
which orders are admitted and apparently considered with 
more care than elsewhere, and in particular the Systema 
NaJturce of LinnaBus, who first introduced into Zoology this 
kind of groups, and the works of Cuvier, in which orders 
are frequently characterized with imusual precision, and 
it appears to me that the leading idea prevailing every- 
where respecting orders, where these groups are not 
admitted at random, is that of a definite rank among 
them — the desire to determine the relative standing of 
these divisions, to ascertain their relative superiority or 
inferiority, as the name order, adopted to designate them, 
itself implies. The first order in the first class of the 
animal kingdom, according to the classification of Lin- 
naeus, is called by him Primates, expressing no doubt his 
conviction that these beings, among which Man is in- 
cluded, rank uppermost in their class. Blainville uses 
here and there the expression of " degrees of organization" 
to designate orders. It is true Lamarck uses the same 
expression to designate classes. We find, therefore, here 
as eveiyvvhere, the same vagueness in the definition of 
the different kinds of groups adopted in our systems. But 
if we would give up an arbitrary use of these terms, and 
assign to them a definite scientific meaning, it seems to 
me most natural, and in accordance with the practice of 
the most successful investigatoi-s of the animal kingdom, 
to call such divisions as are characterized by different 
degrees of complication of their structure within the 
limits of the classes orders. As such I would consider, for 



ORDERS AMONG ANIMALS. 231 

instance, the Actinoids and Halcyonoids in the class of 
Polypi, as circumscribed by Dana; the Hydroids, the 
Discophorae, and the Ctenoids among the Acalephs; the 
Crinoids, Asterioids, Echinoids, and HolothuriaB among the 
Echinoderms ; the Bryozoa, Brachiopods, Tunicata, and 
Lamellibranchiata among the Acephala; the Branchifera 
and Pulmonata among the Gasteropods; the Ophidians, 
the Sanrians, and the Chelonians among the Keptiles ; the 
Ichthyoids and the Anoura among the Amphibians, etc. 

Having shown, in the preceding section, that classes 
rank next to branches, it would be proper to ehow 
here that orders are natural groups, which stand above 
families in their respective classes ; but for obvious rea- 
sons I have deferred this discussion to the following 
paragraph, which relates to families, as it will be easier 
for me to show what is the respective relation of these 
two kinds of groups after their special character has been 
duly considered. 

From the preceding remarks respecting orders, it might 
be inferred that I deny all gradation among all other 
groups, or that I assume that orders constitute necessarily 
one simple series in each class. Far from asserting any 
such thing, I hold, on the contrary, that neither is neces- 
sarily the case. But, to explain fldly my views upon 
this point, I must introduce here some other considera- 
tions. It will be obvious, from what has already been 
said (and the further illustration of this subject will only 
go to show to what extent this is true), that there exists 
an unquestionable subordination among the different 
kinds of groilps admitted in our systems, based upon the 
different kinds of relationship observed among animals: 
that branches are the most comprehensive divisions, in- 
cluding each several classes, that orders are subdivisions 



232 ESSAY ON CLASSIFICATION. 

of the classes, families subdivisions of orders, genera sub- 
divisions of families, and species subdivisions of the 
genera; but not in the sense that each type should 
necessarily include the same number of classes, nor even 
necessarily several classes, as this must depend upon the 
maimer in which the type is carried out. A class, again, 
might contain no orders,^ if its representatives presented 
no different degrees, characterized by the greater or less 
complication of their structure ; or it may contain many 
or few, as these gradations are more or less numerous 
and well marked; but as the representatives of any and 
every class have of necessity a definite form, each class 
must contain at least one family, or many families, in- 
deed, as many as there are systems of forms imder which 
its representatives may be combined, if form can be 
shown to be characteristic of families. The same is the 
case with genera and species; and nothing is more 
remote from the truth than the idea that a genus is 
better defined in proportion as it contains a greater 
number of species, or that it may be necessary to 
know several species of a genus before its existence 
can be fully ascertained. A genus may be more satis- 
fixctorily characterized, its peculiarity more fully ascer- 
tained, and its limits better defined, when we know all its 
representatives ; but I am satisfied that any natural genus 
may be at least pointed out, however numerous its spe- 
cies may be, from the examination of any single one of 
them. Moreover, the number of genera, both in the ani- 
mal and vegetable kingdoms, which contain but a single 
species, is so great, that it is a matter of necessity in all 
these cases to ascertain their generic characteristics from 
that one species. Again, such species require to be cha- 

* Sec Chap. I, Sect. 1. 



ORDERS AMONG ANIMALS. 233 

racterized with as much precision, and their specific charac- 
ters to be described with as much minuteness, as if a host 
of them, although not yet known, existed besides. It is a 
very objectionable practice among zoologists and botanists 
to remain satisfied in such cases with characterizing the 
genus, and perhaps to believe, what some writers have 
actually stated distinctly, that in such cases generic and 
specific characters are identical 

Such being the natural relations and the subordination 
of branches, classes, orders, families, genera, and species, I 
believe, nevertheless, that neither branches, nor classes, 
(orders of course not at all,) nor families, nor genera, nor 
species, have the same standing when compared among 
themselvea But this does not in the least interfere with 
the prominent features of orders, for the relative standing 
of branches, or classes, or families, or genera, or species, 
does not depend upon the degrees of complication of their 
structures as that of orders does, but upon other features, 
as I will now show. The four great types or branches of 
the animal kingdom, characterized as they are by four 
different plans of structure, will each stand higher or 
lower, as the plan itself bears a higher or lower character, 
and to show this to be the case we need only compare 
Vertebrata and Badiata.^ The different classes of one 
type will stand higher or lower, as the ways in which, and 
the means with which, the plan of the type to which they 
belong is carried out, are of a higher or lower nature. 
Orders in any or all classes are of course higher or lower, 
according to the degree of perfection of their representa- 
tives, or according to the complication or simplicity of 

^ I muBt leave out the details of moreover, any text>book of compara-* 
such comparisons, as a mere mention tive anatomy will furnish the com* 
of the point suffices to suggest them; plcte evidence to that effect. 



234 ESSAY ON CLASSIFICATION. 

their structure. Families stand higher or lower, according 
as the peculiarities of their form are determined by modi- 
fications of more or less important systems of organs. 
Genera stand higher or lower, as the structural pecu- 
Uarities of the parts constituting the generic character- 
istics exhibit a higher or lower grade of development 
Species, lastly, stand one above the other in the same 
genus, according to the character of their relations to 
the surrounding world, or that of their representatives 
to one another. These remarks must make it plain that 
the respective rank of groups of the same kind among 
themselves must be determined by the superior or inferior 
grade of those features upon which they are themselves 
founded ; while orders alone are strictly defined by the 
natural degrees of structural complications exhibited 
within the limits of the classes. 

As to the question, whether orders constitute neces- 
sarily one simple series in their respective classes, I would 
say that this must depend upon the character of the chiss 
itself, or the manner in which the plan of the type is car- 
ried out within the limits of the class. If the class is ho- 
mogeneous, that is, if it is not primarily subdivided into 
sub-classes, the orders ^\all, of course, form a single series ; 
but if some of its organic systems are developed in a dif- 
ferent way from the others, there may be one or several 
parallel scries, each subdivided into graduated orders. 
This can, of course, only be determined by a much more 
minute study of the characteristics of classes than has 
been yet made, and mere guesses at such an internal 
arrangement of the classes into series as those proposed 
Ijy Kaup or Fitzinger can only be considered as the first 
attempts towards an estimation of the relative vtdue of 
the intermediate divisions which may exist between the 
classes and their ordei's. 



ORDERS AMONG ANIMALS. 235 

Oken and the physiophilosophers generally have taken 
a different view of orders. Their idea is, that orders re- 
present, in their respective classes, the characteristic fea- 
tures of the other types of the animal kingdona. As 
Oken's Intestinal or Gelatinous animals are characterized 
by a single system of organs, the intestine, they contain 
no distinct orders ; but each class has three tribes, corre- 
sponding to the three classes of this type, which are Infu- 
soria, Polypi, and Acalephs. The tribes of the class of 
Infusoria are Infusoria proper. Polypoid Infusoria, and 
Acalephoid Infusoria ; the tribes of the class of Polypi are 
Infusorial Polypi, Polypi proper, and Acalephoid Polj^i ; 
the tribes of the class Acalephs are Infusorial Acalephs, 
Polypoid Acalephs, and Acalephs proper. But the classes 
of MoUusks, which are said to be characterized by two 
systems of organs, the intestine and the vascular system, 
contain each two orders, one corresponding to the Intes- 
tinal animals, the other to the type of Mollusks ; and so 
Acephala are divided into the order of Gelatinous Ace- 
phala and that of MoUuscoid Acephala, and the Gastero- 
pods and Cephalopods in the same manner into two 
orders each. The Articulata are considered as represent- 
ing three systems of organs, — the intestinal, the vascidar, 
and the respiratory systems; hence their classes are di- 
vided each into three orders. For instance, the Worms 
contain an order of Gelatinous Worms, one of Molluscoid 
Worms, one of Annulate Worms, and the same orders are 
adopted for Crustacea and Insects. Vertebrata are said 
to represent five systems : the three lower ones being the 
intestine, the vessels, and the respiratory organs, and the 
two higher the flesh, (that is, bones, muscles, and nerves), 
and the organs of the senses; hence, five orders in each 
class of this type, as, for example. Gelatinous Fishes, Mol- 



236 ESSAY ON CLASSIFICATION. 

luscoid Fishes, Entomoid Fishes, Carnal Fishes, and Sen- 
sual Fishes, and so also in the classes of Reptiles, Birds, 
and Mammalia.^ 

I have entered into so many details upon these vagaries 
of the distinguished German philosopher, because these 
views, however crude, have imdoubtedly been suggested 
by a feature of the animal kingdom which has thus far 
been too little studied : I mean the analogies which exist 
among animals, besides their true aflSnities, and which 
cross and blend, under modifications of strictly homolo- 
gical structures, other characters, which are only analogi- 
cal But, it seems to me that the subject of analogies is 
too little known, the facts bearing upon this kind of 
relationship being stiU too obscure to be taken as the 
basis of such important groups in the animal kingdom as 
the orders are; and I would insist upon considering the 
complication or gradation of structure as the feature 
which should regulate their limitation, if under order we 
arc to understand natural groups expressing the rank, the 
relative standing, the superiority or inferiority of animals, 
in their respective classes. Of course, groups thus cha- 
nicterized cannot be considered as mere modifications of 
the classes, being founded upon a special category of 
features. 

SECTION IV. 

FAMILIES. 

Nothing is more indefinite than the idea of form, as 
applied by systematic writers, in characterizing animals. 
Here it means a system of the most different figures 

^ See further developments upon geschichte, vol. iv, p. 582. Compare 
this subject in Ok en's Naturphiloso- also the following chapter, 
phio, and in his Allgcmcino Natur- 



FAMILIES. 237 

having a common character, as, for instance, when it is 
said of Zoophytes that they have a radiated form ; there, 
it indicates any outline which circumscribes the body of 
animals, when, for instance, animal forms are alluded to 
in general, instead of designating them simply as animals ; 
here, again, it means the special figure of some indivi- 
dual species. There is, in fsict, no group of the animal 
kingdom, however extensive or however limited, from the 
branches down to the species, in which form it is not 
occasionally alluded to as characteristic. Speaking of 
Articulates, C. E. v. Baer characterizes them as the tyipe 
with elongated forms, MoUusks as the type with massive 
forms, Eadiates as that with peripheric symmetry. Verte- 
brates as that with double symmetry ; evidently taking 
their form, in its widest sense, as expressing the most 
general relations of the different dimensions of the body 
to one another. Cuvier speaks of form in general, with 
reference to these four great types, as a sort of mould, as 
it were, in which the different tjrpes would seem to have 
been cast Again, form is alluded to in characterizing 
orders; for instance, in the distinction between the Bra- 
chyourans aud the Maxjrourans among the Crustacea, or 
between the Saurians, the Ophidians, and the Chelonians. 
It is mentioned as a distinguishing feature in many 
families, ex. gr. the Cetacea, the Bats, etc. Some genera 
are separated from others in the same family on the 
ground of differences of form; and in almost every de- 
scription of species, especially when they are considered 
isolatedly, the form is described at full length. Is there 
not, in this indiscriminate use of the term form, a con- 
fusion of ideas, a want of precision in the estimation of 
what ought to be called form, and what might be desig- 
nated by another name ? Such seems to me to be the case. 



-LlL.. 



238 ESSAY ON CLASSIFICATION. 

m 

In the first place, when form is considered as character- 
istic of Eadiata or Articulata, or any other of the great 
types of the animal kingdom, it is evident that it is not a 
definite outline and well determined figure which is 
meant, but that here the word form is used as a synonym 
for plan. Who, for instance, would describe the tubular 
body of an Holothuria as characterized by a form similar 
to that of the Euryale, or that of an Echinus as identical 
with that of an Asterias ? And who does not see, that, as 
far as the form is concerned, Holothurise resemble Worms 
much more than they resemble any other Echinodenn, 
though, as far as the plan of their structure is concerned, 
they are genuine Kadiates, and have nothing to do with 
the Articulates? 

Again, a superficial glance at any and all the classes of 
the animal kingdom is sufficient to show that each con- 
tains animals of the most diversified forms. What can 
be more difierent than Bats and Whales, Herons and Par- 
rots, Frogs and Sirens, Eels and Turbots, Butterflies and 
Bugs, Lobsters and Barnacles, Nautili and Cuttlefishes, 
Slugs and Conchs, Clams and compoimd Ascidians, Pen- 
tacrinus and Spatangus, Beroc and PhysaHa, Actinia and 
Gorgonia ? And yet they belong respectively to the same 
class, as they are coupled here : Bats and Whales toge- 
ther, etc. It must be obvious, then, that form cannot be 
a characteristic element of classes, if we intend to desig- 
nate anything definite under that name. 

But form has a definite meaning, understood every- 
where, when applied to well-known animals. We speak, 
for instance, of the human form ; an allusion to the form 
of a horae or that of a bidl conveys at once a distinct idea; 
everybody would acknowledge the similarity of form of 
the hoi-se and ass, and knows how to distinguish them by 



FAMILIES. 239 

their form from dogs or cats, or fix)m seals and porpoises. 
In this definite meaning, form corresponds also to what 
we call figure when speaking of men and women; and it 
is when taken in this sense that I would now consider the 
value of forms as characteristic of different animals. We 
have seen that form cannot be considered as a character 
of branches, nor of classes; let us now examine further, 
whether it is a character of species. A rapid review of 
some of the best known types of the animal kingdom, 
embracing well-defined genera with many species, will at 
once show that this cannot be the case ; for such species 
do not generally show the least difference in their forms. 
Neither the many species of Squirrels, nor the true Mice, 
nor the Weasels, nor the Bears, nor the Eagles, nor the 
Falcons, nor the Sparrows, nor the Warblers, nor the genu- 
ine Woodpeckers, nor the true Lizards, nor the Frogs, nor 
the Toads, nor the Skates, nor the Sharks proper, nor the 
Turbots, nor the Soles, nor the Eels, nor the Mackerels, 
nor the Sculpins, nor the genuine Shrimps, nor the Craw- 
fishes, nor the Hawkmoths, nor the Geometers, nor the 
Dorbugs, nor the Spring-Beetles, nor the Tapeworms, nor 
the Cuttlefishes, nor the Slugs, nor the true Asterias, nor 
the Sea-Anemones, could be distinguished among them- 
selves one from the other by their form only. There may 
be differences in the proportions of some of their parts, 
but the pattern of every species belonging to well-defined 
natural genera is so completely identical that it wiU never 
afford specific characters. There are genera in our system 
which, as they now stand, might be alluded to as examples 
contrary to this statement; but such genera are still based 
upon very questionable features, and are likely to be 
found, in the end, to consist of unnatural associations of 
heterogeneous species: at aU events, all recent improve- 



240 ESSAY ON CLASSIFICATION. 

ments in Zoology have gone to limit genera graduaUy 
more and more in such a manner that the species belong- 
ing to each have shown successively less and less differ- 
ence in form, until they have assumed, in that respect, 
the most homogeneous appearance. Are natural genera 
any more to be distinguished by their form one from the 
other 1 Is there any appreciable difference in the general 
form ? I say purposely general form, because a more or 
less prominent nose, larger or smaller ears, longer or 
shorter claws, etc., do not essentially modify the form. 
Is there any real difference in the general form between 
the genera of the most natural families? Do, for instance, 
the genera of Ursina, the Bears, the Badger, the Wolve- 
rines, the Eaccoons, differ in form ? Do the Phocoidse, the 
Delphinoidoe, the Falconinse, the TurdinsB, the Fringil- 
liniB, tlic Picinse, the ScolopacinsB, the Chelonioidae, the 
Gcckonina, the Colubrina, the Sparoidse, the Elaterida^, 
the Pyralidoidae, the Echinoidse, etc, differ any more 
among themselves ? Certainly not ; though, to some ex- 
tent, there ai^e differences in the form of the representa- 
tives of one genus when compared with those of another 
genus; but, when rightly considered, these differences 
appear only as modifications of the same type of forms. 
J ust as there are more or less elongated ellipses, so do we 
find the figure of the Badgers somewhat more contracted 
than that of either the Bears, or the Raccoons, or the 
Wolverines, and that of the Wolverines somewhat more 
(4ongatod than that of the Raccoons; but the form is 
here as completely typical as it is among the Viverrina, 
among the Canina, or among the Brad}^odidse, or among 
the Delphinoida}, etc. We must, therefore, exclude form 
fix)m the characteristics of natural genera, or at least in- 
troduce it only as a modification of the typiciil form of 
natunU families. 



FAMILIES. 241 

Of all the natural groups in the animal kingdom there 
remain, then, only families and orders, for the distinction 
of which form can apply as an essential criterion. But 
these two kinds of groups are just those upon which 
zoologists are least agreed ; so that it may not be easy to 
find a division which all naturalists would aOTce to take 
as an example of a natural order. Let us, however, do 
our best to settle the difficulty, and suppose, for a moment, 
that what has been said above respecting the orders is 
well founded, — that orders are natural groups character- 
ized by the degree of complication of their structure, and 
expressing the respective rank of these groups in their 
class, — then we shall find less difficulty in pointing out 
some few groups which would be generally considered as 
orders. I suppose most naturalists would agree, for in- 
stance, that among Keptiles the Chelonians constitute a 
natural order; that among Fishes, Sharks and Skates 
constitute an order also ; and, if any one would urge the 
necessity of associating also the Cyclostomes with them, 
it would only the better serve my purpose. The Ganoids, 
even when circumscribed within narrower limits than those 
I have assigned to them, and perhaps reduced to the ex- 
treme limits proposed for them by J. Muller, I am equally 
prepared to take as an example, though I have in reality 
still some objections to this limitation, which, however, 
do not interfere with my present object. The Decapods, 
among the Crustacea, I suppose everybody would also 
admit as an order; and I do not care here what other 
families are claimed, besides the Decapods, to complete the 
highest order of the Crustacea. Among the Acephala, I 
trust, the Bryozoa, Tunicata, Brachiopods, and Lamelli- 
branchiata would be also very generally considered to be 
natural orders. Among the Echinoderms I suppose the 

R 



242 ESSAY ON CLASSIFICATION. 

Crinoids, Astcrioids, Echinoids, and Holothurioids would 
be conceded also as such natural orders; among the Aca- 
lephs the Beroids, and perhaps also the Discophorse and 
Hydroids; while, among the Polyps, the Halcyonoids consti- 
tute a verynatural ordcrwhen compared with the Actinoids. 

Let us now consider these orders with reference to the 
characteristic forms they include. The forms of true 
Testudo, of Trionyx, and of Chelonia are very different 
one from the other; and yet few orders are so well cir- 
cumscribed as that of Chelonians. The whole class of 
Fishes scarcely exhibits greater differences than those 
observed in the forms of the common Sharks, the Saw- 
fishes, the conmion Skates, and the Torpedo, not to speak 
of the Cyclostomes and Myxinoids, if these families were 
also considered as members of the order of Placoids. The 
Ganoids cannot be circumscribed within narrower limits 
than those assigned to them by J. Muller; and yet this 
order, thus limited, contains forms as heterogeneous as 
the Sturgeons, the Lepidosteus, the Polypterus, the Amia> 
and a host of extinct genera and families, not to speak of 
those families I have associated with them, and which 
Prof. Muller would have removed, which, if included 
among the Ganoids, would add still more heteromorphous 
elements to this order. Among the Decapods we need only 
remember the Lobsters and Crabs to be convinced that it 
is not similarity of form which holds them so closely 
together as a natural order. How heterogeneous the 
Bryozoa, the Brachiopods, and the Tunicata are among 
themselves, as far as their form is concerned, everybody 
knows who has paid the least attention to these animala 

Unless, then, form be too vague an element to charac- 
terize any kind of natural groups in the animal kingdom, 
it must constitute a prominent feature of families. I 



FAMILIES. 243 

have already remarked, that orders and families are the 
groups upon which zoolc^ists are least agreed, and to the 
study and characterizing of which they have paid least 
attention. Does this not arise simply from the fact, that, 
on the one hand, the difference between ordinal and class 
characters has not been understood, and only assumed to 
be a difference of degree; and, on the other hand, that 
the importance of form, as the prominent character of 
families, has been entirely overlooked? For, though so 
few natural famiUes of animals are well characterized, or 
characterized at all, we cannot open a modem treatise 
upon any class of animals without finding the genera 
more or less naturally grouped together, under the head- 
ing of a generic name with a termination in idee or iruB 
indicating family and sub-family distinctions; and most 
of these groups, however unequal in absolute value, are 
really natural groups, though far from designating always 
natural families, being as often orders or sub-orders as 
families or sub-families. Yet they indicate the fsiciUty with 
which, almost without study, the intermediate natural 
groups between the classes and the genera may be pointed 
out. This arises, in my opinion, from the fact that family 
resemblance in the animal kingdom is most strikingly ex- 
pressed in the general form, and that form is an element 
which falls most easily under our perception, even when 
the observation is made superficially. But, at the same 
time, form is most difficult to describe accurately, and 
hence the imperfection of most of our family character- 
istics, and the constant substitution for such characters of 
features which are not essential to the family. To prove 
the correctness of this view, I would only appeal to the 
experience of every naturalist. When we see new animaLs, 
does not the first glance, that is, the first impression made 

r2 




244 ESSAY ON CLASSIFICATION. 

upon US by their fonn, give us at once a very correct idea 
of their nearest relationship? We perceive, before ex- 
amining any structural character, whether a Beetle is a 
Carabicine, a Longicom, an Elaterid, a Curculionid, a 
Chrysomeline ; whether a Moth is a Noctuelite, a Geo- 
metrid, a Pyralid, etc. ; whether a bird is a Dove, a Swal- 
low, a Humming-bird, a Woodpecker, a Snipe, a Heron, 
etc., etc. But, before we can ascertain its genus, we have 
to study the structure of some characteristic parts ; before 
we can combine families into natural groups, we have to 
make a thorough investigation of their whole structure, 
and compare it with that of other families. So form is 
characteristic of families; and I can add, fix)m a careful 
investigation of the subject for several years past, during 
which I have reviewed the whole animal kingdom with 
reference to this and other topics connected with classifi- 
cation, that form is the essential characteristic of famihea^ 
I do not mean the mere outline, but form as determined 
by structure ; that is to say, that families cannot be well 
defined, nor circumscribed within their natural limits, 
witliout a thorough investigation of all those features of 
the internal stracture which combine to determine the 
fonn. 

The characteristic of the North American Chelonians, 
which I have published in my Contributions to the 
Natural History of the United States,^ may serve as au 
example how this subject is to be treated. I will only 
add here, that, however easy it is at fii'st, from the gene- 
ral impression made upon us l)y the form of animals, to 

* These investigations, which have which I would not allow to appear 

led to most interesting results, have before I could revise the whole ani- 

delayed thus far the publication of mal kingdom in this new light, in 

the systematic part of the Princii)lcs order to introduce as much precision 

of Zoology, undertaken in common as possible into its classification, 
with my friend, Dr. A. A. Gould, and ' Scevol.i,pp.317-36Gof thatwork. 



FAMILIES. 245 

obtain a glimpse of what may fairly be called families, 
few investigations require more patient comparisons than 
those by which we ascertain the natural range of modi- 
fications of any typical form, and the structural features 
upon which it is based. Comparative anatomy has so 
completely discarded every thing that relates to Morpho- 
logy, and the investigations of anatomists lean so uni- 
formly towards a general appreciation of the connections 
and homologies of the organic systems which go to build 
up the body of animals, that, for the purpose of under- 
standing the value of forms and their true foimdation, they 
hardly ever afford us any information, unless it be here 
and there a consideration respecting teleological relations. 

Taking for granted that orders are natural sroups 
characteLd b^e compUcation of their structu^ and 
that the different orders of a class express the different 
degrees of that compUcation,— taking now further for 
granted that families are natural groups, characterized by 
their form as determined by structural peculiarities, it 
follows that orders are the superior kind of division, as 
we have seen that the several natural divisions which are 
generally considered as orders contain each several natu- 
ral groups, characterized by different forms, that is to say, 
constituting as many distinct families. 

After this discussion it is hardly necessary to add, that 
families cannot by any means be considered as modifica- 
tions of the orders to which they belong, if orders are to 
be characterized by the degrees of complication of their 
structure, and families by their forms. I would also 
further remark, that there is one question relating to the 
form of animals which I have not touched upon here, and 
which it is still more important to consider in the study 
of plants, namely, the mode of association of individuals 



246 ESSAY ON CLASSIFICATION. 

into larger or smaller communities, as we observe them, 
particularly among Polyps and Acalephs. These aggrega- 
tions have not, as far as their form is concerned, the same 
importance as the form of the individual animals of which 
they are composed, and therefore seldom aflford trust- 
worthy family characters. But this point may be more 
appropriately considered in connection with the special 
illustration of our Hydroids, to which the third volume 
of my Contributions is to be devoted. 

I have stated above, that botanists have defined the 
natural families of plants with greater precision thiui 
zoologists those of animals ; I have further remarked also, 
that most of them make no distinction between orders 
and families. This may be the result of the peculiar 
character of the vegetable kingdom, which is not built 
upon such entirely different plans of structure as are 
animtds of different branches. On the contrary, it is 
possil)le to trace among plants a certain gradation between 
their liigher and lower types more distinctly than among 
animals, even though they do not, any more than animals, 
constitute a simple series. It seems to me, nevertheless, 
that if Crj'ptogams, Gymnosperms, Monocotyledones, and 
Dicotyledones cim be considered as branches of the vege- 
table kingdom, analogous to Radiata, Mollusks, Articulata, 
and Vertebrata among animals, such divisions as Fungi, 
Algoo, Lichens, ^Mosses, Hepaticae, and Ferns in the widest 
sense, may be taken as classes. Diatomaceae, Confer\\a\ 
and Fuci may tlicn be considiTcd as orders, ^Mosses and 
Ilepatica) as ordei^s, and Equisetaccii), Ferns proper, lly- 
dropterids, and Lyc(^])odiaceie as orders {dso, as they 
exhil)it different degrees of coni])lication of structure, 
wliil(3 their natural sulxlivisions, which are moi*e closely 
allied in form or habitus, may be considered as families; 



GENERA. 247 

natural families among plants having generally as distinct 
a port as families among animals have a distinct form. 
We need only remember the Palms, the Coniferae, the 
Umbelliferae, the Compositae, the Leguminosae, the Lab- 
iatae, etc., as satisfactory examples of this kind. 

SECTION V. 

OEKERA. 

LinnsBUS already knew very well that genera exist in 
nature, though what he calls genera frequently constitute 
groups to which we at present give other names, as we 
consider many of them as families ; but it stands proved 
by his writings that he had fully satisfied himself of the 
real existence of such groups, for he says distinctly, in 
his Philosaphia Botanica, sect. 169, " Scias characterem 
non constituere genus, sed genus characterem. Cha- 
racterem fluere e genere, non genus e charactere. Cha- 
racterem non esse, ut genus fiat, sed ut genus noscatur." 

It is surprising, that, notwithstanding such clear state- 
ments, which might have kept naturalists awake respect- 
ing the natural foimdation of genera, such loose ideas 
have become prevalent upon this subject, that at present 
the niunber of investigators who exhibit much confidence 
in the real existence of their own generic distinctions is 
very limited. And as to what genera really are, the want of 
precision of ideas appears still greater. Those who have 
considered the subject at all seem to have come to the 
conclusion that genera are nothing but groups including 
a certain number of species agreeing in some more gene- 
ral features than those which distinguish species ; thus 
recognizing no difierence between generic and specific 
characters as such, as a single species may constitute a 



248 ESSAY ON CLASSIFICATION. 

genus, whenever its characters do not agree with the 
characters of other species, and many species may con- 
stitute a genus, because their specific characters agree to 
a certain extent among themselves.^ Far from admitting 
such doctrines, I hope to be able to show, that, however 
much or however Uttle species may differ among them- 
selves as species, yet they may constitute a natural genus^ 
provided their respective generic characters are identical 
I have stated before, that, in order to ascertain upon 
what the different groups adopted in our systems are 
founded, I have consulted the works of such writers as are 
celebrated in the annals of science for having characterized 
mth particular felicity any one kind of these groups ; and 
I have mentioned Latreille as prominent among zoologists 
for the precision with which he has defined the genera of 
Crustacea and Insects, upon which he has written the 
most extensive work extant.^ An anecdote, which I have 
often heard repeated by entomologists who knew Latreille 
well, is very characteristic as to the meaning he connected 
with the idea of genera. At the time he was preparing 
the work just mentioned, he lost no opportunity of ob- 
taining specimens, the better to ascertain from nature the 
generic peculiarities of these animals; and he used to 
apply to the entomologists for contributions to his collec- 
tion. It was not show specimens he cared to obtain ; any 
would do, for he used to say he wanted them only " to 
examine their parts." Have we not here a hint, from a 
master, to teach us what gcuera arc, and how they should 

1 Spring, Ueber die naturhistoris- Dana (J. D.), Thoughts on Species, 

chen Begriffe von Gattung, Art und Amer. Journ. 8c. and Arts, 1857, vol. 

Abart; Lci|)zig,1838,lvol.bvo.— Buu- 24, p. .305. 

MEisTER (LI.), Zoonomische Briefc ; ^ Latreille, Genera Orustaceo- 

Leipzig, 1856, 2 vols. 8vo. — Wollas- rum ct Inscctorum ; Paris, et Ar- 

TON (T. v.). On the Variation of gent., l8liG-18()J), 4 vols. 8vo. 
Species; Loudon, 1856, 1 vol. 8vo. — 



GENERA. 249 

be characterized ? Is it not the special stracture of some 
part or other, which characterizes genera ? Is it not the 
finish of the organization of the body, as worked out in 
the ultimate details of structure, which distinguishes one 
genus fix)m another ? Latreille, in expressing the want 
he felt with reference to the study of genera, has given us 
the key-note of their harmonious relations to one another. 
Genera are most closely allied groups of animals, diflFering 
neither in form nor in complication of structure, but 
simply in the ultimate structural peculiarities of some of 
their parts ; and this is, I beheve, the best definition which 
can be given of genera. They are not characterized by 
modifications of the features of the famihes, for we have 
seen that the prominent trait of family difierence is to be 
found in a typical form ; and genera of the same family 
may not diflFer at all in form. Nor are genera merely a 
more comprehensive mould than species embracing a 
wide range of characteristics; for species in a natural 
genus should not present any structural difierences, but 
only such as express the most special relations of their 
representatives to the surroimding world and to each 
other. Genera, in one word, are natural groups of a pecu- 
liar kind; and their special distinction rests upon the 
idtimate details of their structure. 



SECTION VI. 

8FECIES. 



It is generally believed that nothing is easier than to 
determine species ; and that, of all the degrees of relation- 
ship which animals exhibit, that which constitutes specific 
identity is the most clearly defined. An unfailing crite- 
rion of specific identity is even supposed to exist i^j the 



250 



ESSAY ON CLASSIFICATION. 



sexual connexion, which so naturally brings together the 
individuals of the same species in the function of repro- 
duction. But I hold that this is a complete fallacy, or at 
least a petitio principiiy not admissible in a philosophical 
discussion of what truly constitutes the characteristics of 
species. I am even satisfied that some of the most per- 
plexing problems involved in the consideration of the 
natural limits of species would have been solved long ago 
had it not been so generally urged that the ability and 
natural disposition of individuals to connect themselves 
in fertile sexual intercourse was of itself sufficient evidence 
of their specific identity. Without alluding to the fact, 
that every new case of hybridity^ is an ever-returning 
protest against such an assertion; and without entering 
here into a discussion respecting the possibility or practi- 
cability of setting aside this difficulty by introducing the 
consideration of the limited fertility of the progeny of 
individuals of different species, I will only remark, that, 
as long as it is not proved that all the varieties of dogs, 
and of any others of our domesticated animals and of our 
cultivated plants, are respectively derived from one un- 
mixed species ; and as long as doubts may Ixi entertained 
respecting the common origin of all races of men from 
one common stock, it is not logictd to admit that sexuiJ 
connexion, resulting even in fertile offspring, is a trust- 
worthy evidence of specific identit)^ 

To justify this assertion I would only ask, AMiere is the 



* WiEQMAN, GckrdDto Preisschrift 
uber die Bastarderzeugung im Pflan- 
zenreich ; Braunschweig, 1828, 8vo. 
— Braun (A.), Ueber die Erschein- 
ung der Verjiingung in der Natur; 
Freiburg, 1849, 4to. — Morton (8. 
G.), Essay onlljbriditjjAiner. Jourii., 
1^47.-^ Additional Observations on 



nybridity in Animals, and on some 
collateral subjects ; Charleston Med. 
Joum., 1850. — De Selys Lo50- 
CHAMPS, Recapitulation des bjbrides 
observes dans la famille des Anati- 
does, Bull. Ac. Brux., 1845 ; and 
Additions, ibid., Ib6(), 2dc part., page 
(i. 



SPECIES. 251 

unprejudiced naturalist who in our days would dare to 
maintain: 1st, that it is proved that all the domesticated 
varieties of sheep, of goats, of bulk, of llamas, of horses, 
of dogs, of fowls, etc., are respectively derived from one 
common stock; 2nd, that the supposition that these 
varieties have originated from the complete amalgamation 
of several primitively distinct species is out of the ques- 
tion ; and 3rd, that varieties imported from distant coun- 
tries and not before brought together, such as the Shanghae 
fowl, for instance, do not completely mingle ? Where is 
the physiologist who can conscientiously affirm that the 
limits of the fertility between distinct species are ascer- 
tained with sufficient accuracy to make it a test of specific 
identity? And who can say that the distinctive charac- 
ters of fertile hybrids and of unmixed breeds are suffi- 
ciently obvious to enable anybody to point out the primi- 
tive features of all our domesticated animals, or of all our 
cultivated plants? As long as this cannot be done, as 
long as the common origin of all races of men, and of the 
difierent animals and plants mentioned above, is not 
proved, while their fertility with one another is a fact 
which has been daily demonstrated for thousands of 
years ; as long as large numbers of animals are her- 
maphrodites, never requiring a connection with other 
individuals to multiply their species; as long as there are 
others w^hich multiply in various ways without sexual 
intercourse, — it is not justifiable to assume that those 
animals and plants are unmixed species, and that sexual 
fecundity is the criterion of specific identity. Moreover, 
this test can hardly ever have any practical value in most 
cases of the highest scientific interest. It is never re- 
sorted to, and, as far as I know, has never been apphed 
with satisfactory results to settle any doubtful case. It 



252 ESSAY ON CLASSIFICATION. 

has never assisted any anxious and conscientious naturalist 
in investigating the degree of relationship between closely 
allied animals or plants living in distant regions or in dis- 
connected geographical areas. It will never contribute 
to the solution of any of those difficult cases of Bceming 
difference of identity between extinct animals and plants 
found in different geological formations. In all critical 
cases, requiring the most minute accuracy and precision, 
it is discarded as unsafe, and of necessity questionable. 
Accurate science must do without it ; and the sooner it 
is altogether discarded, the better. But, like many reUcs 
of past time, it is dragged in as a sort of theoretical bug- 
bear, and exhibited only now and then to make a false 
show in discussions upon the question of the unity of 
origin of mankind. 

There is another fallacy, connected with the prevailing 
ideas about species, to which I would also allude, — the 
fancy that species do not exist in the same way in nature 
as genera, families, orders, chisses, and types. It is 
actually maintained by some, that species are founded in 
nature in a manner different from these groups ; ^ that 
their existence is, as it were, more real, whilst that of the 
other groups is considered as ideal, even when it is ad- 
mitted that these groups have themselves a natunJ 
foundation. 

Let us consider this point more closely, as it involves 
the whole question of individuality. I wish, however, 
not to be understood as under\'aluing the importiince of 
sexual relations as indicative of the close ties which unite, 
or may imite, the individuals of the same species. I 
know as well as any one to what extent they manifest 
themselves in nature, l)ut I moan to iiLsist upon the un- 

* BuicMEiuTEK (II.); Zoou. liricfc, ([. a., vol. 1, p. 11. 



SPECTES. 253 

deniable fket that these relations are not so exclusive as 
those naturalists would represent them who urge them as 
an imfaihng criterion of specific identity. I would re- 
mind those who constantly forget it, that there are animals, 
which, though specifically distinct, do unite sexually, 
which do produce offspring, mostly sterile, it is true, in 
some species, but fertile to a limited extent in others, and 
in others even fertile to an extent which it has not yet 
been possible to determine. Sexual connection is the re- 
sult, or rather one of the most striking expressions, of the 
close relationship established in the beginniug between 
individuals of the same species, and is by no means the 
cause of their identity in successive generations. When 
first created, animals of the same species paired because 
they were made one for the other; they did not take one 
another in order to build up their species, which had full 
existence before the first individual produced by sexual 
connection was bom. 

This view of the subject acquires greater importance in 
proportion as it becomes more apparent that species did 
not originate in single pairs, but were created in large 
numbers in those numeric proportions which constitute 
the natural harmonies between organized beings. It alone 
explains the possibility of the procreation of Hybrids, as 
founded upon the natural relationship of individuals of 
closely allied species, which may become fertile with one 
another the more readily as they difier less structurally. 

To assimae that sexual relations determine the species, 
it should further be shown that al>solute promiscuousness 
of sexes among individuals of the same species is the pre- 
vailing characteristic of the animal kingdom ; while the 
fact is, that a large number even of animals, not to speak 
of Man, select their mates for life, and rarely have any 



254 ESSAY ON CLASSIFICATION. 

intercourse with others. It is a fact known to every &nner, 
that different breeds of the same species are less inclined to 
mingle than individuals of the same breed. For my own 
part, I cannot conceive how moral philosophers, who urge 
the unity of origin of Man as one of the fundamental 
principles of their religion, can at the same time justify 
the necessity which it involves of a sexual intercourse 
between the nearest blood relations of that assumed first 
and unique human family, when such a connection is re- 
volting even to the savage. Then again, there are innu- 
merable species in which vast numbers of individuals are 
never developed sexually, others in which sexual indivi- 
duals appear only now and then at remote intervals, while 
many intermediate generations are produced without any 
sexual connection, and others still which multiply more 
extensively by budding than by sexual generation. I 
need not again allude here to the phenomena of alternate 
generation, now so well known among Acalephs and 
Worms, nor to the polymorphism of many other types. 
Not to acknowledge the significance of such facts, would 
amount to the absurd pretension, that we are to take 
distinctions and definitions, introduced into our science 
during its infancy, as standards for our appreciation of the 
phenomena of nature, instead of framing and remodelling 
our standards, according to the laws of nature, as our 
knowledge extends. It is, for instance, a specific cha- 
racter of the Horse and the Ass to be able to connect 
sexually ^^dth each other, and thus to produce an offspring 
different from that which they bring forth among them- 
selves. It is characteristic of the Mare, as the representa- 
tive of its species, to bring forth a ]\Iule with the Jackass, 
and of the StaUion to procreate Hinnies with the She-ass. 
It is equally characteristic of them to produce again other 



SPECIES. 255 

kinds of halfbreeds with the Zebra, the Daw, etc. And 
yet, in face of all these facts, which render sexual repro- 
duction, or at least promiscuous intercourse among the 
representatives of the same species, so questionable a 
criterion of specific identity, there are still naturalists 
who would represent it as an unfailing test, only that 
they may sustain one single position, that all men are de- 
rived from one single pair. 

These facts, with other facts which every day go more 
extensively to show the great probability of the inde- 
pendent origin of individuals of the same species in dis- 
connected geographical areas, force us to remove from the 
philosophic definition of species the idea of a commimity 
of origin, and consequently, also, the idea of a necessary 
genealogical connection. The evidence, that all animals 
have originated in large numbers, is gn>wing so strong 
that the idea that every species existed in the beginning 
in single pairs may be said to be given up almost entirely 
by naturalists. Now if this is the case, sexual derivation 
does not constitute a necessary specific character, even 
though sexual connection be the natural process of their 
reproduction and multiplication. K we are led to admit 
as the beginning of each species the simultaneous origin 
of a large number of individuals, and if the same species 
may originate at the same time in different localities, 
these first representatives of each species, at least, were 
not connected by sexual derivation ; and as this applies 
equally to any first pair, this fancied test criterion of 
specific identity must at all events be given up ; and with 
it goes also the pretended real existence of the species, in 
contradistinction to the mode of existence of genera, 
families, orders, classes, and types ; for what really exist 
are individuals, not species. We may, at the utmost. 



256 ESSAY ON CLASSIFICATION. 

consider individuals as representatives of species ; but no 
one individual nor any niunber of individuals represents 
its species only, without representing also at the same 
time, as we have seen above (Sect. I to V) its genus, its 
family, its order, its class, its branch. 

Before attempting to prove the whole of this proposi- 
tion, I will first consider the characters of the individual 
animals. Their existence is scarcely limited as to time 
and space within definite and appreciable limits. No one 
nor all of them represent ftdly, at any particular time, 
their species ; they are always only the temporary repre- 
sentatives of the species, inasmuch as each species exists 
longer in nature than any of its individuals. All the in- 
dividuals of any or of all species now existing are only 
the successors of other individuals which have gone be- 
fore, and the predecessors of the next generations : they 
do not constitute the species, they represent it. The 
species is an ideal entity, as much as the genus, the family, 
the order, the class, or the type; it continues to exist, 
while its representiitives die, generation after generation. 
Again, these representatives do not represent simply what 
is specific m the individual, but they exhibit and repro- 
duce in the same manner, generation after generation, all 
tliat is generic in tliem, all that characteiizes the family, 
the order, the class, the branch, with the same fulness, the 
same constancy, the same precision. Species, then, exist 
ill natures in the Siime manner as any other group; they 
are (juite as ideal in their mode of existence as genera, 
families, etc., or quite as rcid. But individuals truly exist 
in a diircrciit way: no one of them exhil)its at one time 
all the characteristics of the species, even though it be 
h(»rma[)lir(Mlite, neither do any two represent it, even 
though the species be not polynioii)hous, for individuals 



spECiEa 257 

have a growth, a youth, a mature age, an old age, and are 
bound to some limited home during their lifetime. It is 
true that species are also limited in their existence; but 
for our purpose we can consider these limits as boundless, 
inasmuch as we have no means of fixing their duration, 
either for the past geological ages or for the present 
period, whilst the short cycles of the life of individuals 
are quantities easily measurable. Now, as truly as indi- 
viduals, while they exist, represent their species for the 
time being and do not constitute them, so truly do these 
same individuals represent at the same time their genus, 
their family, their order, their class, and their type, the 
characters of which they bear as indelibly as those of the 
species. 

As representatives of Species^ individual animals bear 
the closest relations to one another; they exhibit definite 
relations also to the surrounding elements, and their ex- 
istence is limited within a definite period. 

As representatives of Genera^ these same individuals 
have a definite and specific ultimate structure, identical 
with that of the representatives of other species. 

As representatives of Families, these same individuals 
have a definite figure, exhibiting, with similar forms of 
other genera, or for themselves, if the feunily contains but 
one genus, a distinct, specific pattern. 

As representatives of Orders^ these same individuals 
stand in a definite rank when compared to the representa- 
tives of other families. 

As representatives of Classes, these same individuals 
exhibit the plan of structure of their respective types in 
a special manner, carried out with special means and in 
special ways. 

As representatives of BrancheSy these same individuals 

s 



258 ESSAY OK CLA8SIFICATI0K. 

are aU organized upon a distinct plan, differing fixim the 
plan of other types. 

Indiyiduals, then, are the bearers, for the time beingi 
not only of specific characteristics, but of all the natural 
features in which animal life is displayed in all its diversity. 

Viewing individuals in this light, they resume aH their 
dignity; and they are no longer so absorbed in species 
as to be ever its representatives without being any- 
thing for themselvea On the contrary, it becomes pkio, 
from this point of view, that the individual is the worthy 
bearer, for the time being, of all the riches of nature's 
wealth of life. This view further teaches us how we may 
investigate not only the species in the individual, but also 
the genus, the family, the order, the class, the branch, as 
indeed naturalists have at all times done in practice, 
whilst denying the possibility of it in theory. 

Having thus cleared the field of what does not belong 
to it, it now remains for me to show what in reahty 
confttitutes species, and how they may be distinguished 
with precision within their natural limits. 

If we would not exclude from the characteristics of 
species any feature which is essential to it, nor force into 
it any one which is not so, we must first acknowledge 
that it ia one of the characters of species to belong to a 
given period in the history of our globe, and to hold defi- 
nite* reflations to the physical conditions then prevailing, 
and to animals and plants then existing. These relations 
are manifold, and arc exhibited: 1st, in the geographical 
r«ng(; natural to any species, as well as in its capability 
of being acchmatized in countries where it is not primi- 
tively found ; 2nd, in the connection in which they stand 
to the elements around them, when they inhabit either 
the water or the land, deep seas, brooks, rivers and lakes, 



SPECIES. 259 

shoals, flaty sandy, muddy, or rocky coasts, limestone 
banks, coral reefs, swamps, meadows, fields, dry lands, salt 
deserts, sandy deserts, moist land, forests, shady groves, 
sunny hills, low regions, plains, prairies, high table-lands, 
mountain peaks, or the frozen barrens of the Arctics, etc. ; 
3rd, in their dependence upon this or that kind of food 
for tlieir sustenance; 4th, in the duration of their life; 
5th, in the mode of their association with one another, 
whether living in flocks, small companies, or isolated; 
6th, in the period of their reproduction; 7th, in the 
changes they undergo during their growth, and the pe- 
riodicity of these changes in their metamorphosis; 8th, in 
tiieir association with other beings, which is more or less 
close as it may only lead to a constant association in 
some, whilst in others it amounts to parasitism; 9th, 
specific characteristics are further exhibited in the size to 
which animals attain, in the proportions of their parts to 
one another, in their ornamentation, etc., and all the 
variations to which they are liable. 

As soon as all the facts bearing upon these different 
points have been fully ascertained, there can remain no 
doubt respecting the natural limitation of species ; and it 
is only the insatiable desire of describing new species from 
insufficient data which has led to the introduction in our 
systems of so many doubtful species, which add nothing 
to our real knowledge, and only go to swell the nomen- 
clature of j^niTn^tlft and plants, already so intricate. 

Assuming, then, that species cannot always be identified 
at first sight, and that it may require a long time and 
patient investigation to ascertain their natural limits; 
iiiwnmiTig further, that the features alluded to above are 
among the most prominent characteristics of species, we 
may say that species are based upon well determined 

s2 



260 ESSAY ON CLASSIFICATION. 

relations of individuals to the world around them, and to 
their kindred, and upon the proportions and relations of 
their parts to one another, as well as upon their ornamenta- 
tion. Well digested descriptions of species ought, therefore, 
to be comparative ; they ought to assume the character of 
biographies, and attempt to trace the origin, and follow 
the development, of a species during its whole existence. 
Moreover, all the changes which species may undergo in 
the course of time, especially imder the fostering care of 
man, in the state of domesticity and cultivation, belong 
to the history of the species ; even the anomalies and dis- 
eases to which they are subject, belong to their cycle, as 
well as their natural variations. Among some species 
variation of colour is frequent, others never change, and 
some change periodically, others accidentally ; some throw 
oflF certain ornamental appendages at regular times, the 
Deers their horns, some Birds the ornamental plumage which 
they wear in the breeding season, etc. All this should be 
ascertained for each, and no species can be considered as 
well defined and satisfactorily characterized, the whole 
history of which is not completed to the extent alluded 
to above. The practice, prevailing since Linnaeus, of 
limiting the characteristics of species to mere diagnoses, 
has led to the present confusion of our nomenclature, and 
made it often impossible to ascertain what were the species 
which the authors of such condensed descriptions hail 
before them. But for the tradition which has transmitted, 
generation after generation, the knowledge of these species 
among the cultivators of science in Europe, this confusion 
would be still greater; but for the preservation of most 
original collections, it would be inextricable. In countries 
which, like America, do not enjoy these advantages, it is 
often hopeless to attempt criticid investigations upon 



OTHER NATURAL DIVISIONS. 261 

doubtful cases of this kind. One of our ablest and most 
critical investigators, the lamented Dm Harris, has very 
forcibly set forth the difficulties under which American 
naturalists labour in this respect, in the Preface to his 
Report upon the Insects Injurious to Vegetation. 



SECTION VIL 

OTUEB KATUBAX DIVISIONS AMONG ANIMALS. 

Thus far I have considered only those kinds of divisions 
which are introduced in almost all our modem classifica- 
tions, and attempted to show that these groups are 
founded in nature, and ought not to be considered as 
artificial devices, invented by man to facUitate his studies. 
Upon the closest scrutiny of the subject, I find that these 
divisions cover all the categories of relationship which 
exist among animals, as far as their structure is concerned. 

Branches or types are characterized by the plan of 
their structure ; 

Classes^ by the maimer in which that plan is executed, 
as far as wajs and means are concerned; 

OrderSy by the degrees of complication of that struc- 
ture; 

Families, by their form, as far as determined by struc- 
ture; 

Genera, by the details of the execution in special 
parts; and 

Species, by the relations of individuals to one another 
and to the world in which they live, as well as by the 
proportions of their parts, their ornamentation, etc. 

And yet there are other natural divisions which must 
be acknowledged in a natural zoological system ; but 



262 ESSAY ON CLASSIFICATION. 

these are not to be traced so uniformly in all classes aB 
the former, — thdj* are in ffeality only limitations of the 
other kinds of divisions. 

A class, in which one syBtem of organs presents a 
peculiar development while all the other systems coincide, 
may be subdivided into sub-classes; for instance, the 
Marsupialia when contrasted with the Placental Mam- 
maUa. The characters upon which such a subdivision is 
founded are of the kind upon which the class itself is 
based, but do not extend to the whole class. An order 
may embrace natural groups of a higher value than 
families, founded upon ordinal characters, which may yet 
not determine absolute superiority or inferiority, and 
therefore not constitute for themselves distinct orders ; as 
the characters upon which they are founded, though of 
the kind which determines orders, may be so blended as 
to determine superiority in one respect, while with refeiv 
ence to some other features they may indicate inferiority. 
Such groups are called sub-orders. The order of Testu- 
dinata illustrates this point best, as it contains two natural 
sub-orders.^ A natural family may exhibit such modifi- 
cations of its characteristic form that upon these modifi- 
cations subdivisions may be distinguished, which have 
been called sub-families by some authors, and tribes or 
legions by others. In a natural genus, a number of 
species may agree more closely than others in the par- 
ticulars which constitute the genus and lead to the dis- 
tinction of sub-genera. The individuals of a species, 
occupying distinct fields of its natural geographical area, 
may difier somewhat from one another, and constitute 
varieties, etc. 

' See my Contributions to the Natural Ilistory of the United States, vol. i, 

p. 3U8. 



OTHER NATURAL DIVISIONS. 263 

These distinctions have long ago been introduced into 
our systems ; and every practical naturalist, who has 
made a special study of any class of the animal kingdom, 
must have been impressed with the propriety of acknow- 
ledging a large number of subdivisions to express all the 
various degrees of affinity of the different members of any 
higher natural group. Now, while I maintain that the 
branches, the classes, the orders, the families, the genera, 
and the species are groups established in nature respec- 
tively upon different categories, and while I feel prepared 
to trace the natural limits of these groups by the cha- 
racteristic features upon which they are founded, I must 
confess at the same time that I have not yet been able 
to discover the principle which obtains in the limitation 
of their respective subdivisions.^ All I can say is, that 
all the different categories considered above, upon which 
branches, classes, orders, families, genera, and species are 
founded, have their degrees, and upon these degrees sub- 
classes, sub-orders, sub-families, and sub-genera have been 
established. For the present, these subdivisions must be 
left to arbitrary estimations ; and we shall have to deal 
with them as well as we can, so long as the principles 
which regulate these degrees in the different kinds of 
groups are not ascertained. I hope, nevertheless, that 
such arbitrary estimations are for ever removed from our 
science, as far as the categories themselves are concerned. 

Thus far, inequality of weight seems to be the standard 
of the internal valuation of each kind of group ; and this 
inequality extends to all groups, for even within the 
branches there are some classes more closely related among 

^ Professor James D. Dana has Sc. and Arts, 1858, vol. 26, p. 333. 

thrown out some valuable suggestions See also Weinland (D.), On Series 

upon this point in his review of my in the Animal Kingdom, Proc. Brit. 

** Contributions." See Amcr. Jouru. Nat. Hist. Soc, vol. vi, p. 112. 



264 ESSAY ON CLASSIFICATION. 

themselves than others : Polypi and Acalephs, for instance^ 
stand nearer to one another than to Echinoderms ; Crus- 
tacea and Insects are more closely allied to one another 
than to Worms, etc. Upon such degrees of relationship 
between the classes, within their respective branches, the 
so-called sub-types or sub-branches have been founded, 
and these differences have occasionally been exaggerated 
so far as to give rise- to the establishment of distinct 
branches. Upon similar relations between the branches, 
sub-kingdoms have also been distinguished, but I hardly 
think that such far-fetched combinations can be considered 
as natural groups ; they seem to me rather the expression 
of a relation arisiog from the weight of their whole 
organization as compared with that of otlier groups^ than 
the expression of a definite relationship. 



SECTION VIIL 

SUCCESSIVE DEVELOPMENT OP CHABiiCTEBS. 

It has been repeated again and again, that the cha- 
racters which distinguish the different types of the animal 
kingdom are developed in the embryo in the successive 
order of their importance : first, the structural features 
of their respective branches ; next, the characters of the 
class ; next, those of the order ; next, those of the family ; 
next, those of the genus ; and, finally, those of the species. 
Tins assertion has met with no direct opposition ; on the 
contrary, it seems to have been approved of almost without 
discussion, and now to be generally taken for granted 
The importance of the subject requires, however, a closer 
scrutiny ; for if Eiiil)ry()lorry is to lead to great impmve- 
nieuts in Zoology, it is necessiiiy at the outset to deter- 



SUCCESSION OF CHARACTERS. 265 

mine well what kind of information we may expect it to 
furnish to its sister science. Now I would ask, if, at this 
day, zoologists know with sufficient precision what are 
typical, ekss, ordinal, family, generic, and specific cha- 
racters, to be justified in maintaining, that, in the progress 
of embryonic growth, the features which become suc- 
cessively prominent correspond to these characters, and 
occur in the order of their subordination ? I doubt it. I 
will say more : I am sure there is no such imderstanding 
about it among them ; for, if there was, they would already 
have perceived that this assumed coincidence between 
the subordination of natural groups among ftdl-grown 
iiniTnalR, and the successive stages of growth during their 
embryonic period of life, does not exist in nature. It is 
true, there are certain features in the embryonic develop- 
ment which may suggest the idea of a progress from a 
more general typical organization to its ultimate specializ- 
ation ; but it nowhere proceeds in that stereotyped order 
of succession, nor indeed even, in a general way, in the 
manner thus assumed 

Let us see whether it is not possible to introduce more 
precision into this matter. Taking it for granted that what 
I have said about the characteristics of natural groups 
in the animal kingdom is correct, that we have, 1st, four 
great tjrpical branches of the animal kingdom, character- 
ized by different plans of structure ; 2nd, classes, cha- 
racterized by the ways in which, and the means with 
which these plans of structure are executed ; 3rd, orders, 
characterized by the degrees of simplicity or compUcation 
of that structure ; 4th, famUies, characterized by differ- 
ences of form, or by structural peculiarities determin- 
ing form ; 5th, genera, characterized by ultimate pecu- 
liarities of structure in the parts of the body ; 6th, species, 



266 ESSAY ON CLAS8IFICATI0K. 

characterized by relations and proportions of parts among 
themselves, and of the individuals to one another and 
to the surrounding mediums; we finally reach indi- 
viduals, which, for the time being, represent not only the 
species with aU their varieties, and variations of age, sex, 
size, etc., but also the characteristic features of all the 
higher groups. We have thus, at one epd of the series, 
the most comprehensive categories of the structure of 
animals, while at the other end we meet individual beinga 
Individuality on one side, the most extensive divisions of 
the animal kingdom on the other. Now, to b^in our 
critical examination of the progress of life in its successive 
manifestations with the extremes, is it not plain, from all 
we know of Embryology, that individualization is the 
first requirement of all reproduction and multiplication ; 
and that an individual germ, (or a nimiber of them,) an 
ovarian egg, or a bud, is first formed and becomes distinct 
as an individual fi:om the body of the parent, before it 
assumes either the characters of its branch or those of its 
class, order, etc. 1 This fact is of great significance as 
showing the importance of individuality in nature. Next^ 
it is true we generally perceive the outlines of the plan 
of structure before it becomes apparent in what manner 
that plan is to be carried out ; and the character of the 
branch is marked out, in its most general features, before 
that of the class can be recognized with any degree of 
precision. Upon this fact, we may base one of the most 
important generalizations in Embryology. 

It has been maintained, in the most general terms, 
that the higher animals pass during their development 
through all the phases characteristic of the inferior classes. 
Put in this form, no statement can be further from the 
truth ; and yet there iu:e decided relations, within certain 



SUCCESSION OF CHARACTEBS. 267 

limits, between the embryonic stages of growth of higher 
animals and the pennanent characters of others of an in- 
ferior grade. Now, the fact mentioned above enables us 
to mark with precision the limits within which these 
relations may be traced. As eggs, in their primitive con- 
dition, animals do not diflfer one fix)m the other *; but as 
soon as the embryo has begun to show any characteristic 
features, it presents such peculiarities as distinguish its 
brancL It cannot^ therefore, be said that any animal 
passes through phases of development which are not in- 
cluded within the limits of its own brancL No Verte- 
brate is, or resembles at any time, an Articulate ; no 
Articulate a Mollusk ; no Mollusk a Eadiate ; and vice 
versa. Whatever correlations between the young of 
higher animals and the perfect condition of inferior ones 
may be traced, they are always limited to representatives 
of the same branch ; for instance. Mammalia and Birds, in 
their earlier development^ exhibit certain features of the 
lower classes of Vertebrates, such as the Reptiles or 
Fishes ; Insects recall the Worms in some of their earlier 
stages of growth, etc., but even this statement requires 
qualifications, to which we shall have occasion to refer here- 
after. However, this much is already evident, that no higher 
animal passes through phases of development recalling all 
the lower types of the animal kingdom, but only such as 
belong to its own brancL What has been said of the 
infusorial character of young embryos of Worms, Mol- 
lusks, and Radiates, can no longer stand before a serious 
criticism, because, in the first place, the animals generally 
called Infusoria cannot themselves be considered as a 
natural class; and in the second place, those to which a 
reference is made in this connexion are themselves free- 
moving embryos.1 

^ See above, Chap. I, Sect. 18. 



268 ESSAY ox CLASSIFICATION. 

With the progress of growth, and in proportion as the 
type of an animal becomes more distinctly marked in its 
embryonic state, the plan of structure appears also more 
distinctly in the peculiarities of that structure, — ^that is 
to say, in the ways in which, and the means by which, 
the plan, only faintly indicated at first, is to be carried 
out and become prominent, — ^and by this the class charac- 
ter is pointed out For instance, a wonnlike insect-larva 
will already show, by ite trachea, that it is to be an 
Insect and not to remain a Worm, as it at first appears 
to be: but the complications of that special structure, 
upon which the orders of the class of Insects are based, 
do not yet appear; this is perfected only at a late period 
in the embryonic life. At this stage we frequently notice 
already a remarkable advance of the features character- 
istic of the families over those characteristic of the order; 
for instance, young Hemiptera and young Orthoptera 
may safely be referred to their respective families, from 
the characteristics they exhibit before they show those 
jioeuliarities which characterize them as Hemiptera or 
as Orthoptera ; yoimg Fishes may be kno\ni as members 
of their respective fiunilies before the characters of their 
onlers are apparent, etc. 

It is very ob\'ious wliy this should be so. With the 
progn^ss of the development of the structure the general 
form is gnulually sketched out, and it has already reached 
many of its most distinctive features before all the com- 
plications of the structure which ch;iracterize the orders 
have become apparent; and as form essentiaUy charac- 
terizes the families, we see here the reason why the family 
type may be fully stamped upon an animal before its 
ordinal characters are developed. Even specific charac- 
ters, as far as they depend upon the proportions of parts 



SUCCESSION OP CHARACTERS. 269 

and have on that ground an influence in modifying the 
form, may be recognized long before the ordinal charac- 
ters are fully developed. ITie Snapping-Turtle, for in- 
stance, exhibits its small crosslike sternum, its long tail, 
its ferocious habits, even before it leaves the egg, before 
it breathes through lungs, before its derm is ossified to 
form a bony shield, etc. ; nay, it snaps with its gaping 
jaws at any thing brought near, when it is still sur- 
rounded by its amnios and allantois, and its yolk still 
exceeds in bulk its whole body.^ The calf assumes the 
form of the bull before it bears the characteristics of the 
hollow-homed Ruminants ; the fawn exhibits all the pecu- 
liarities of its species before those of its family are un- 
folded. 

With reference to generic characters, it may be said 
that they are scarcely ever developed in any type of the 
animal kingdom before the specific features are for the 
most part fully sketched out, if not completely developed. 
Can there be any doubt that the human embryo belongs 
to the genus Homo, even before it has cut a tooth ? Is 
not a kitten or a puppy distinguishable as a cat or a dog 
before the claws and teeth tell their genus ? Is not this 
true also of the Lamb, the Kid, the Colt, the Rabbits,-and 
the Mice, of most Birds, most Reptiles, most Fishes, most 
Insects, Mollusks and Radiates? And why should this 
be? Simply because the proportions of parts, which con- 
stitute specific characters, are recognizable before their 
ultimate structural development, which characterizes 
genera, is completed. 

^ pR. M. Y. Neu-Wied quotes as a is still a pale, almost colourless 

xeinarkable fact, that the Chelonura embryo, wrapped up in its footal en- 

ierperUina bites as soon as it is velopes, with a yolk larger than itself 

hatched. I have seen it snapping in hanging from its sternum, three 

the same fierce manner as it does months before it is hatched, 
when full-grown, at a time when it 



I 



270 ESSAY ON CLASSIFICATION. 

It seems to me that these facts are likely to influence 
the future progress of Zoology, in enabling us gradually 
to unravel more and more distinctly the features which 
characterize the different subordinate groups of the animal 
kingdom. The views I have expressed above, of the 
respective value and the prominent characteristics of these 
different groups, have stood so completely the test in this 
analysis of their successive appearance^ that I consider 
this circumstance as adding to the probability of their 
correctness. 

But this has another very important bearing, to which 
I have already alluded in the beginning of these remaikaw 
Before Embryology can furnish the means of settling 
some of the most perplexing problems in Zoology, it is 
indispensable to ascertain first what are typical, class, ordi- 
nal, family, generic, and specific characters; and as long 
as it is supposed that these characters appear neces- 
sarily during the embryonic growth, in the order of their 
subordination, there is no possibility of deriving jfrom 
embryological monographs that information upon this 
point so much needed in Zoology, and so seldom alluded 
to by embryologists. Again, without knowing what con- 
stitutes truly the characters of the groups named above, 
there is no possibility of finding out the true characters of 
a genus of which only one species is known, of a family 
which contains only one genus, etc.; and for the same 
reason no possibiUty of arriving at congruent results with 
reference to the natural limitations of genera, families, 
orders, etc., without which we cannot even begin to build 
up a permanent classification of the animal kingdom, and, 
still less, hope to establish a solid basis for a general com- 
parison between the animals now living and those which 
have peopled the surface of our globe in past geological 
ages. 



SUCCESSION OF CHARACTEBS. 271 

It is not accidentally that I have been led to these in- 
vestigations, bnt by necessity. As often as I tried to 
compare higher or more limited groups of animals of the 
present period with those of former ages, or early stages 
of growth of higher living animals with full-grown ones of 
lower types, I was constantly stopped in my progress by 
doubts as to the equality of the standards I was applying, 
until I made the standards themselves the object of direct 
and very extensive investigations, covering indeed a much 
wider ground than would appear from these remarks; for 
upon these principles I have abeady remodelled, for my 
own convenience, nearly the whole animal kingdom, and 
introduced into almost every dass very unexpected changes 
in the classification. 

I have already expressed above^ my conviction that the 
only true system is that which exists in nature; and as, 
therefore, no one should have the ambition of erecting a 
system of his own, I will not now even attempt to present 
these results in the shape of a diagram, but remain satis- 
fied to express my belief that all we can really do is, at 
best, to offer imperfect translations, in human language, 
of the profound thoughts, the innumerable relations, the 
unfjEtthomable meaning of the plan actually manifested in 
tlie natural objects themselves; and I should consider it 
as my highest reward, should I find, after a number of 
years, that I had helped others on in the right path. 

SECTION IX 

THE CATEOOBIES OF ANALOGY. 

Thus far we have considered those relations only among 
animals^ which are founded upon strictly homological 

' See Chap. I, Sect. 1, p. 13. 



272 ESSAY ON CLASSIFICATION. 

features of their structure. We now proceed to examine 
the more remote and less definite relations, which are 
called analogies. 

It has already been stated in what way homologies dif- 
fer from analogies.^ Homology is that kind of relation- 
ship which is founded upon identity of structure in differ- 
ent animals belonging to natural divisions of the same 
kind; while analogy is a resemblance arising iroui the 
combination of features characteristic of one natural 
group with those of another group.^ We have, indeed, 
seen that all the animals belonging to the same branch 
are homologous, as far as the plan of their structure is 
concerned; that all the members of the same class are 
homologous, as far as the mode of execution of that struc- 
ture is concerned ; that all the members of the same order 
are homologous in the complication of their structure; 
that all the representatives of the same family are homo- 
logous in form; that the different genera of one and the 
same family exhibit homologous peculiarities in the de- 
tails of their structure ; and that even within the narrow 
limits of species we may still trace homologous features, 
among the genera which have numerous representatives, 
even when such resemblances do not extend to the species 
of closely allied genera. It is plain from this that the 
categories of homology are as numerous and diversified 
as the essential kinds of differences which we may trace 
in the structure of animals; or, in other words, we have 
branch homologies, class homologies, ordinal homologies, 
family homologies, generic homologies, and specific homo- 

* See p. 26. based upon similarity of function, 

- Ilouiology has albo been defined without reference to structure. The 

as the rehitionship arising from definition given above is more pre- 

Identity of structure without refer- cise, as it embraces all the different 

eucc to function, while analogy is categories of analogy and homology. 



THE CATEGORIES OF ANALOGY. 273 

logiea Examples of the more comprehensive kinds of 
these homologies will occm* to every practical geologist. 
As to specific homologies, they are particularly traceable 
in those structural features which determine the propor- 
tions among the parts; as for instance, when all the 
species of one genus are either long-necked, short-tailed, 
long-legged, etc., while those of closely allied genera may 
present reverse proportions, etc. 

Let us now see what are the categories of analogy, and 
how far it is possible, under all circumstances, to distin- 
guish homological and analogical features. If analogy is a 
resemblance arising from a combination of features charac- 
teristic of one group, with those characteristic of another 
group (such as class characters of one class with those of 
another class, or those of families of another class), then the 
investigation will only require the recognition of the dif- 
ferent categories of structure already considered (such as 
branches, classes, orders, etc.), and a correct appreciation 
of the mode of their combination with those of another 
group. It will, for instance, be sufficient to ascertain in 
what manner the features, resulting from a certain mode 
of execution of the homologies of one type, are combined 
with structures of another type; or, in other words, to 
recognize any feature wherever it appears, and not merely 
within the limits within which structures are strictly 
homologous. The study of analogies is therefore limited 
to the investigation of more or less distinct features that 
are naturally characteristic of one kind of group, in their 
combination with features of groups of another kind. For 
instance, the similarity between an insect wing and the 
wing of a bird is based upon analogy. The entire differ- 
ence of structure between the organs of flight in these 
two classes of animals forbids our considering the resem- 

T 



274 ESSAY ON CLASSIFICATION. 

blance which exists between them as homological, for 
they are not built upon homologous structures. But there 
is analogy between them, inasmuch as the peculiar struc- 
ture characteristic of two diflferent types is worked up 
into organs that appear the same because they perform 
similar functions. 

Admitting these distinctions to be correct, the catego- 
ries of analogy must be like those of homology; either 
analogies of branch, or of class, or of order, or of family, 
or of genus, or of species ; and these analogies may either 
be observed between different branches, classes, orders, 
families, genera, and species; or features characteristic of 
branch or of class may be limited to certain families, or 
even to genera of other branches and other classes; so 
that the study of analogies becomes very diflBcult and 
highly comphcated; and these complications have, no 
doubt, been the source of most errors and inaccuracies in 
the attempts that have been made to classify the animal 
kingdom. 

Branch analogies. The plan of structure characteristic 
of the four branches of the animal kingdom are so pecu- 
liar that we nowhere find analogies of this kind extending 
from one branch to aD the representatives of another 
branch. On the contrary, they extend generally to minor 
divisions of some classes, and rarely to entire classes. Yet, 
among Mollusks, all the Cej)halopods have some analogy 
with the Radiates in the arrangement of their arms around 
the mouth. All the Bryozoa have a striking analogy 
with the Polyps in the crown which spreads around their 
up})er pai-t; and so it is with the tentacles of a large 
number of the Dorsibranchiate Annelids. There is an 
unmistakable analogy l)et\veen the structure of the solid 
frame of Echinodorms (especially in the star-fishes) and 



THE CATEGORIES OF ANALOGY. 275 

the plan of structure of the Articulates ; so much so that 
Oken does not hesitate to refer the Echinoderms to the 
type of Articulates, mistaking their analogy for true homo- 
logy. 

Class analogies. The ways in which, and the means 
by which, the plan of structure of one class is carried 
out, as compared with another class, frequently produce 
striking analogies. For instance, among Vertebrates the 
whole class of birds is winged; and wings constructed 
like the wing of birds exists in no other class. Yet the 
bats are also winged; and many fishes which are capable 
of rising above the water are also described as winged. 
But the wing of a bat is homologous to the foreleg of the 
other mammalia, and only analogous to that of birds ; for 
it exhibits the special homologies of the class of mam- 
malia, and not those of the class of birds. ^ The same is 
true of the so-called wings of the flying fishes, in which 
the wing is a fin, homologous to the pectoral fin of other 
bony fishes, and not constructed in the same way as the 
wing of the bat or that of the bird. The wing of insects 
is entirely difierent, and its analogy with the wing of 
birds more remote, than that of the bat and of the flying 
fish, inasmuch as it is not an analogy between members 
of different classes of the same branch, but between two 
classes of different branches, differing therefrom in the 
plan of structure, and not only in the mode of execution 
of one and the same plan. 

Ordinal analogies. As orders are founded upon the 
complications of the structure which characterizes the 
different classes, it is not likely that ordinal analogies will 
occur between the different orders of one and the same 

* As limbs of Vertebrates these homolofjous ; but as wings thej are 
two kinds of wings are, nevertheless, only analogous. 



276 ESSAY ON CLASSIFICATION. 

class; we may rather expect them to be prominent be- 
tween the orders of closely allied classes, or between the 
orders of a higher class and the lower classes of the same 
branch. We find, for instance, a remarkable correspond- 
ence between the orders of the class of Batrachians, and 
those of the class of true Keptiles.^ The same may be 
said of the order of Cetacea in the class of Mammalia, as 
compared to the whole class of Fishes, or of the lower 
order of the Insects (the Myriapods) as compared to the 
class of Worms, or of the lower order of Acalephs (the 
Hydroids) as compared to the class of Poljrps.^ An accu- 
rate knowledge of this kind of analogies is of the utmost 
importance for the study of the true affinities of animals, 
since a misapprehension of the real value of their struc- 
tural features has again and again misled zoologists into 
combining such groups as if they were truly related. In 
the beginning of the last century, for instance, the Cetacea 
were generally united with the Fishes, to which they are 
only analogous ; and even to this day we see the Hydroids, 
which are true Acalephs of a lower order, imited into one 
class with the Polypi. 

Family analogies. It requires little familiarity with 
the animal kingdom to know how strong may be the re- 
semblance between the forms of animals, even when they 
belong to entirely difierent types; but, unless their pat- 
tern be determined by identical structural features, their 
form certainly cannot be considered as homologous; and 
however close the resemblance may be externally, an 
attempt to distinguish between analogical and homologi- 

1 For further details upon this ' For further details respecting 

point) see the second part of the first the Uydroids, I must refer to the 

volume of my Contributions to the third volume of my Contributions to 

Nat. Hist, of the Un. St., Sect. Ill, the Nat. Hist, of the Un. St., now in 

p. 252. the press. 



THE CATEGORIES OF ANALOGY. 277 

cal forms cannot fail to add precision to our zoological 
investigations. When, for instance, the form of the Worms 
is compared with that of the Holothurians, it should be 
borne in mind that in the Worms, according to the plan of 
their structure and their homology to the other Articulates, 
their longer diameter is the longitudinal diameter; while 
the longer diameter of the Holothurians, when identified 
by their homologies with the other Radiates, is their ver- 
tical diameter. This shews at once, that however similar 
to one another, the form of the Holothurians is only ana- 
logous to that of the Worms. 

The limits within which similar forms may be homolo- 
gous appear to be very wide, and to extend beyond the 
limits of their respective classes. The form of the Salaman- 
ders and the Lizards, for instance, is certainly homological, 
though they are members of different classes ; yet similar 
forms within the same class are not necessarily homolo- 
gous, — ^for instance, the long snout of Syngnathus, and 
that of Fistularia, or the flat heads of Lophius and of 
Scaphirhynchus, are only remotely analogous, their struc- 
ture being entirely diff'erent. The forms of animals have 
been so imperfectly studied, and the structural elements 
which determine them so little considered, that the time 
has hardly come yet to determine with any degree of 
accuracy the analogies and homologies of the form of ani- 
mals. Considered with reference to their position, the 
six pairs of articulated appendages which are placed upon 
the sides of the mouth of the horse-shoe crab (Limulus) 
are truly homologous to the jaws of the higher Crustacea; 
but by their form they resemble the thoracic legs of the 
latter; and yet, as appendages to the normal rings of an 
Articulate, all these parts are homologous. Here, there- 
fore, it becomes necessary to remember that while the 



278 ESSAY ON CLASSIFICATION. 

appendages of the mouth of Limulus are only analogous 
to the legs of the Decapods, as far as their form is con- 
cerned, these organs are yet homologous as parts of the 
body of an Articulate. This and similar cases may shew 
how wide a field of investigation lies before us in the 
study and discrimination of homological and analogical 
forms. 

Generic Analogies. As the generic characters are 
based upon peculiaiities of structure limited to some part 
or other of an animal, we may expect to find the generic 
analogies reduced to a resemblance of certain parts of the 
body and not extending to its general appearance. For 
while genera, as members of a family, must exhibit the 
same form, combined with the structural complication of 
their order, it is obvious that, if there is any generic ana- 
logy between animals of different families, their whole 
form may be widely different and the complication of 
their structure exhibit entirely different conbinations, or 
be based upon diff^erent modes of execution, if they 
belong to different classes, and even be constructed upon 
different plans of structure, if they belong to different 
branches ; and yet some of their parts should be similar 
in some way or other, in order to present a generic 
analog}'-. 

Now such generic analogies are rather frequent, and 
may be traced between animals of widely different fami- 
lies, belonging to different orders, nay even to different 
classes and to different branches ; for instance, there is 
a marked generic andogy between the dentition of the 
Insectivora, of the cLass of MammaHa, and that of the 
Characiiii of the cIuhs of Fishes, so also between some 
genera of the family of Sparoids and those of the Chro- 
niids, l)ctwt'en sonic geneia of the family of Insectivom 



THE CATEGORIES OF ANALOGY. 279 

and of the Rodentia, and between some of the family of 
Bombyces and of the Papiliones, etc. 

Specific Analogies. If the characteristic features of 
species be truly found in the relations which animals bear 
to the surrounding world or to one another, and in the 
relative proportions of their parts, and their ornamenta- 
tion, we cannot fail to find specific analogies resulting 
from these different aspects in animals belonging to dif- 
ferent genera, to different families, to different orders, and 
even to different classes and branches. As far as they 
are aquatic, animals belonging to different genera which 
number terrestrial species also, have a certain analogy 
with one another. All animals living in pairs or in flocks, 
or isolated, may in this respect be considered as having 
an analogy to one another, especially if they belong to 
genera in which different species bear these different rela- 
tions to one another. But it is in the proportions of the 
parts to one another in the species of different genera 
belonging to the same family or even to different families 
of the same class, and in the ornamentation of their sur- 
face, that we observe the most niunerous specific analogies. 
Reference has already been made to the specific homolo- 
gies resulting from the relative length of the head, the 
neck, the tail, etc. But there is a specific analogy only 
between the Zerda, a species of dog found in the interior 
of Africa, which is characterized by the extraordinary 
length of its ears, and those species of hare which live also 
in the desert, and have much larger and longer ears than 
those inhabiting the woods and marshes. This analogy is 
no doubt owing to the fact that under the conditions in 
which these animals are placed, they require a keener 
perception of sound, and yet they belong to different 
orders, though of the same class. This is therefore a spe- 



280 ESSAY ON CLASSIFICATION. 

cific analogy. The pattern of colouration may also exhibit 
specific analogy, as, for instance, in the transverse bands 
of the tiger when compared to the Quagga, in the spots 
of the leopard and the Giraffe, which is so striking as to 
have suggested the name of the latter, Camelo-paxdalis. 

As it is not my intention here to trace all these analo- 
gies throughout the Animal Kingdom, these few examples 
may sufiice to call attention to the subject, and to lead 
hereafter to a more careful investigation of the different 
categories of analogy. A few more remarks may, how- 
ever, find a plac6 here to show how to distinguish analo- 
gical from homological features. As homologies, whether 
extensive or limited, are strictly confined within groups 
of the same kind, it is evident that imless any feature 
observed in any animal be common to all the representa- 
tives of the group in which it occurs, we shall have good 
reason to suspect that it is not based upon strict homo- 
logy, but rather belongs to some category of analogy. It 
for instance, the dorsal cord is a fundamental feature of 
Vertebrates, any structure in the longitudinal axis of an 
animal which is not structurally identical with the dorsiil 
cord cannot be homologous with it, but must be some- 
thing only analogous to it; for instance, the medial stripe 
which appears during the early development of the em- 
bryo of the earlier Crustacea. For the farther progress 
of the formation of the backbone, we trace the formation 
of arches below as weD as above the dorsal cord, while in 
Crustacea, there is a similar development only on one 
side. We are therefore compelled to consider the solid 
arches of Crustacea only as analogous structures to Ver- 
tobne and not as homologous with them, the more so, 
since these arches enclose not only the iierv^ous system, 
us iu Vertebrates, but all ihe other viscex^a besides. The 



THE CATEGORIES OF ANALOGY. 281 

system of Articulation in Articulates exhibits, therefore, a 
Branch analogy with the vertebral system of the Verte- 
brates, but there is no true homology between them. The 
class of Fishes is eminently characterized by the presence 
of gills, and so have Crustacea gills, and so also the 
Cephalopods, a large number of Grasteropods, and most 
Acephala. But the structure of these gills is widely 
different in these different classes, and their presence only 
constitutes class analogies, and is no indication of a real 
affinity ; while the so-called lungs of the land Gastero- 
pods have the closest structural resemblance to the giUs 
of the other MoUusks, thus showing a real affinity between 
them, while their air sacks, on accoimt of their gill-Kke 
structure, constitute only an analogy between them and 
the other air-breathing animals. We may go on testing 
in this way the analogies and homologies in all their 
degrees and combinations throughout the animal king- 
dom, and be sure to arrive at satisfactory results, provided 
we remember that analogies are features of one group 
combined with the characteristic features of another 
group, and not, like homologies, circimiscribed within one 
and the same group. 



SECTION X. 

CONCLUSIONS. 

The importance of such an investigation as the preced- 
ing must be obvious to every philosophical investigator. 
As soon as it is understood that all the different groups 
introduced into a natural system may have a definite 
meaning ; as soon as it can be shown that each exhibits a 
definite relation among hving beings, founded in nature. 



282 ESSAY ON CLASSIFICATION. 

and no more subject to arbitrary modifications than any 
other law expressing natural phenomena; as soon as it ia 
made plain that the natural limits of all these groups may 
be ascertained by careful investigations, the interest in 
the study of classification, or the systematic relationship 
existing among all organized beings, which has almost 
ceased to engage the attention of the more careftd original 
investigators, will be revived ; and the manifold ties which 
link together all animals and plants as the living expres- 
sion of a gigantic conception, carried out in the course of 
time, like a soul-breathing epos will be scrutinized anew, 
determined with gxeater precision, and expressed with 
increasing clearness and propriety. Fanciful and artifi- 
cial classifications will gradually lose their hold upon a 
better informed community ; scientific men themselves 
will be restrained from bringing forward immature and 
premature investigations ; no characteristics of new spe- 
cies will have a claim upon the notice of the learned, 
wliich have not been fully investigated, and compared 
with those most closely allied to it; no genus will be 
admitted, the structural peculiarities of wliich are not 
clearly and distinctly illustrated ; no family will be con- 
sidered as well founded, which shall not exhibit a distinct 
system of forms intimately combined and determined by 
structural relations ; no order will appear admissible, 
which shall not represent a well-marked degree of struc- 
tural complication ; no class will desen^e that name, wliich 
shall not appear as a distinct and independent expression 
of some general plan of structure, carried out in a pecu- 
liar way and with peculiar means; no type will be re- 
cognized as one of the fundamental groups of the animal 
kingdom, which shall not exliibit a plan of its own, not 
convertible into another. No naturalist will be justified 



CONCLUSIONS. 283 

in introducing any one of these groups into our systems 
without showing: 1st, that it is a natural group; 2nd, 
that it is a group of this or that kind, so as to avoid hence- 
fortJi calling groups that may be genera, families ; groups 
that may be orders, families ; groups that may be orders 
or chtsses, classes or branches respectively ; 3rd, that the 
characters by which these groups may be recognized are 
in fact respectively specific, generic, family, ordinal, classic, 
or typicdl characters, so that our works may no longer 
exhibit the annoying confusion, which is to be met almost 
everywhere, of generic characters in the diagnoses of spe- 
cies, or of family and ordinal characters in the character- 
istics of classes and branches.^ 

It may, perhaps, be said that all this will not render 
the study of Zoology more easy. I do not expect that it 
will; but if an attentive consideration of what I have 
stated in the preceding pages respecting classification 
should lead to a more accurate investigation of all the 
different relations existing among animals, and between 
them and the world in which they live, I shall consider 
myself as having fully succeeded in the object I have had 
in view from the beginning, in this inquiry. Moreover, 
it is high time that certain zoologists, who would call 
themselves investigators, should remember, that natural 
objects, to be fiilly understood, require more than a pass- 
ing glance ;^ they should imitate the example of astrono- 

* As I do not wish to be personal, indiscriminately to distinguish all 

I will refrain from quoting examples these groups. 

to justify this assertion. I would ^ The mere indication of the exist- 
only request those who care to be ence of a species is a poor addition 
accurate, to examine critically almost to our knowledge, when compared to 
any description of species, any cha- those monographs in which either 
racterization of genera, of families, the structure or the development of 
of orders, of classes, or of types, to a single animal is fully illustrated ; 
satisfy themselves that characters of such as Lyonnet's Anatomy of the 
the same kind arc introduced almost Oossus, Bojauus* Anatomy of the 



284 ESSAY ON CLASSIFICATION. 

iners, who have not become tired of looking into the 
rehitions of the few members of our solar system and de- 
termining, with increased precision, their motions, their size, 
their physical constitution, and should keep in mind that 
every organized being, however simple in its structure, 
presents to our appreciation far more complicated phe- 
nomena, within our reach, than all the celestial bodies put 
together; they should remember, that, as the great Ute- 
rary productions of past ages attract ever anew the at- 
tention of scholars, who never feel that they have ex- 
hausted the inquiry into their depth and beauty, so the 
living works of God, which it is the proper sphere of 
Zoology to study, wiU never cease to present new at- 
tractions to them, if they proceed to the investigation of 
them with the right spirit The study of them, indeed, 
ought to inspire every one with due reverence and admi- 
ration for such wonderful productions. 

The subject of classification in particular, which seems 
to embrace apparently so limited a field in the science of 
animals, cannot be rightly and fully understood without 
a comprehensive knowledge of all the topics alluded to in 
the preceding pages. 

Turtle, Strauss-Durckheim'g Anato- years will be required, at the present 

my of Melolontha, Owen's Anatomy rate of our progress, to iuTestigate 

of the Nautilus, Bacr's, Bischoflfs, satisfactorily, and in all their rela- 

Rathke's, J. Miiller's, K()lliker*s, He- tions, the hundred thousands of Hying 

rold's, and so many other embryolo- and extinct animals now known to 

gical works. And yet valuable as exist. It might afford aome con- 

thcse investigations are, they cover solation to those impatient spirits 

only a very small part of the field, who quarrel with their fellow-students 

It may, indeed, be said that there about the discovery of a hair upon a 

hardly appears one such work every stuffed skin, if they only knew what 

other year, and that thousands of rich harvests remain to be gathered. 



M 



CHAPTER THIRD. 



NOTICE OF THE PRINCIPAL SYSTEMS OP ZOOLOGY. 



SECTION I. 

OBKB&AL BEMABK8 UPON HODBBN SYSTEMS. 

Without attempting to give an historical account of the 
leading features of all zoological systems, it is proper that 
I should here compare critically the practice of modem 
naturalists with the principles discussed above. With 
this view, it would hardly be necessary to go back beyond 
the publication of the ** Animal Kingdom", by Cuvier, were 
it not that Cuvier is still represented by many naturalists, 
and especially by Ehrenberg^ and some other German zoo- 
logists, as favouring the division of the whole animal 
kingdom into two great groups, one containing the Verte- 
brates, and the other all the remaining classes, under the 
name of Invertebrates; while in reality it was he who, 
dismissing his own earlier views, first introduced into the 
classification of the animal kingdom that fourfold division 
which has been the basis of all improvements in modem 
Zoology. He first showed that animals difier, not only by 
modifications of one and the same organic structure, but 
are constructed upon four different plans of structure, 

' Eherubbbo (0. G.), Die CoralleDthiere des rothcn Meeres; Berlin, 1834, 
4io^ p. 30. 




286 ESSAY ON CLASSIFICATION. 

forming natural, distinct groups, which he called Radiat*% 
Articulata, Mollusca, and Vertebrata. 

It is true that the further subdivisions of these leading 
groups have undergone many changes since the pubhca- 
tion of the " Rfegne Animal/' Many smaller groups, even 
entire classes, have been removed from one of his " em- 
branchments" to another; but it is equally true that the 
characteristic idea which lies at the bottom of these great 
divisions was first recognized by him, the greatest zoolo- 
gist of all time. 

The question which I would examine here in particular 
is, not whether the circumscription of these great groups 
was accurately defined by Cuvier, whether the minor 
groups referred to them truly belong there or elsewhere, 
nor how far these divisions may be improved within their 
respective limits ; but whether there are four great fundar 
mental groups in the animal kingdom based upon four 
difi*erent plans of structui-e, and neither more nor less than 
four. Tliis question is very seasonable, since modem 
zo()logists, and especially Siebold, Leuckart, and Vogt, have 
proposed combinations of the classes of the animal king- 
dom into higher groups, differing essentially from those of 
Cuvier. It is but justice to Leuckart to say that he has 
exliibited, in the discussion of this subject, an acquaint- 
ance with the whole range of Invertebrata,^ which de- 
mands a careful consideration of the changes he proposes, 
as tliey are based upon a critical discrimination of differ- 
euccH of great value, though I think he overrates their 
importance. The modifications introduced by Vogt, on 
the contniry, appear to me to be based upon entirely un- 
j)liysi()logical principles, though seemingly borrowed from 
tliat all important guide, Embryologj^ 

' Leuckart (R.), Uebcr (lie Mor- haltnissc der wirUellosen Thiere ; 
j)holo;:ic luid die Vcrwainlt.shaftsvcr- Braunschweig, 1818, 1 vol. Svo. 



MODERN SYSTEMS. 



287 



The divisions adopted by Leuckart are : Protozoa 
(though he does not enter upon an elaborate considera- 
tion of that group), Coelenterata, Echinodermata, Vermes, 
Arthropoda^ Mollusca, and Vertebrata. The classification 
adopted, many years before, by Siebold, in his text-book 
of comparative anatomy, is nearly the same, except that 
the Mollusks follow the Worms, that the Coelenterata and 
Echinoderms are united into one group, and that the Bry- 
ozoa are left among the Polyps. 

Here we have a real improvement upon the classifica- 
tion of Cuvier, inasmuch as the Worms are removed from 
among the Radiates, and brought nearer the Arthropods, 
an improvement, however, which, so far as it is correct, 
has already been anticipated by many naturalists, since 
Blainville and other zoologists long ago felt the impro- 
priety of allowing them to remain among Eadiates, and 
have been induced to associate them more or less closely 
with Articulates. But I beheve the union of the Bryozoa 
and Rotifera with the Worms, proposed by Leuckart, to be 
a great mistake ; and as to the separation of the Coelente- 
rata from the Echinoderms, I consider it as an exaggeration 
of the difierence which exists between the Polyps and Aca- 
lephs on the one hand, and the Echinoderms on the other.^ 



1 The readiness \vith which the 
(}ennan naturalists have acquiesced 
in the proposition of LeucKart to 
unite the Polyps and Acalephs into 
one class, seems to be owing to the 
circumstance that their opportunities 
for studying the Polyps have been 
chiefly limited to the Actiniae. Had 
they been able to extend their inves- 
tigations to the Astreeans and Madre- 
pores, and to the many types of Halcy- 
onoids which characterize the Faunro 
of the tropics, they could not have 
failed to perceive that the Polyps 
constitute for themselves a distinct 



class, founded upon a special mode 
of execution of the plan which distin- 
guishes the Radiata from the other 
branches of the animal kingdom. 
Their investigations have truly shown, 
what several French naturalists have 
long maintained, that many families 
of Radiata, long referred to the class 
of Polyps, such as thtf Hydroids, can- 
not be separated from the Acalephs , 
but they have been misled, by the 
evidence thus obtained, to an exag- 
geration of the affinities of the Aca- 
lephs and Polyps. The Polyps, as a 
class, differ from the Acalephs in ex- 



288 ESSAY ON CLASSIFICATION. 

The fundamental groups adopted by Vogt^ are : Pro- 
tozoa, Radiata, Vermes, Mollusca, Cephalopoda, Articulata, 
and Vertebrata, an arrangement which is based solely 
upon the relations of the embryo to the yolk, or the ab- 
sence of eggs. But, as I have already stated, this is an 
entirely unphysiological principle, inasmuch as it assumes 
a contrast between the yolk and the embryo within limits 
which do not exist in nature. The Mammalia, for in- 
stance, which are placed, like aU other Vertebrata, in the 
category of the animals in which there is an opposition 
between the embryo and the yolk, are as much formed of 
the whole yolk as the Echinoderms or Mollusks. The yolk 
undergoes a complete segmentation in the Mammalia, as 
well as in the Radiates, the Worms and most Mollusks ; and 
the embryo, when it makes its appearance, no more stands 
out from the yolk than the little Starfish stands out from 
its yolk. These simple facts, known since Sars and 
Bischoflf published their first observations twenty years 
ago, is in itself suflficicnt to show that the whole principle 
of classification of Vogt is radically wrong. 

Respecting the assertion, that neither Infusoria nor 

hibiting radiating partitions, project- kind as those that project around the 
ing inward from the outer wall of upper margin of the main cavity, 
the body into the main cavity, and Again, the marginal tentacles of the 
in having a digestive cavity derived Acalcphs are homologous to those of 
from the inversion of the upper part the Polyps, while their oral append- 
of that wall into the upper part of ages are characteristic of their class, 
the main cavity. In Acalephs there I may add also that the radiating 
are no radiating partitions, and the partitions of the Rugosa, which I re* 
digestive cavity is hollowed out of fer to the Acalephs, as weU as the 
the mass of the body ; the central Tabulata, are not homologous to the 
prolongation of the body rising above radiating partitions of the Actinoids 
the digestive cavity in the shape of and Halcyonoids, but correspond to 
oral appendages, which are never the ridges of the stem of certain Hal- 
hollow as the tentacles of the Polyps cyonoids, and are, like them, a foot 
are. The mouth tentacles of Cerian- secretion. 

thus, which are hollow, are not ho- * Voot (Carl), ZoolosischeBriefe. 

niologous to the oral appendages of Naturgeschichte der lebenden und 

the Acalcphs, but constitute only an untergegangencn Thiere. Frankfurt 

inner row of tentacles, of the bame a M., 1851 ; vol. i, p. 70. 



MODERN SYSTEMS. 289 

Rhizopoda produce any eggs, I shall have more to say 
presently. As to the arrangement of the leading groups, 
Vertebrata, Articulata, Cephalopoda, Mollusea, Vermes, 
Kadiata, and Protozoa in Vogt's system, it must be appa- 
rent to every zoologist conversant with the natural affini- 
ties of animals, that a classification which interposes the 
whole series of Mollusks between the types of Articulata 
and Worms cannot be correct. A classification based, 
like this, solely upon the changes which the yolk under- 
goes, is not likely to be the natural expression of the 
manifold relations existing between all animals. Indeed, 
no system can be true to nature which is based upon the 
consideration of a single part or a single organ. 

After these general remarks, I have only to show more 
in detail why I believe that there are only four great 
fundamental groups in the animal kingdom, neither more 
nor less. 

With reference to Protozoa, first, it must be acknow- 
ledged, that, notwithstanding the extensive investigation 
of modem writers upon Infusoria and Rhizopoda, the true 
nature of these beings is still very little known. The 
Rhizopoda have been wandering from one end of the 
series of Invertebrata to the other, without finding a 
place generally acknowledged as expressing their true 
affinities. The attempt to separate them from aU the 
classes with which they have been so long associated, and 
to place them with the Infusoria in one distinct branch, 
appears to me as mistaken as any of the former arrange- 
ments ; for I do not even consider that their animal 
nature is yet proved beyond a doubt, though I have 
myself once suggested the possibility of a definite relation 
between them and the lowest Gasteropods.^ Since it 

* Comp. Chap. I, Sect. 18, p. 113. 

U 



290 ESSAY ON CLASSIFICATION. 

has been satisfactorily ascertained that the Corallines and 
Nullipores are genuine Algae which contain more or less 
lime in their structure, and since there is hardly any 
group among the lower animals and lower plants which 
does not contain simple locomotive individuals, as well as 
compound communities, either free or adhering to the 
soil, I do not see that the facts known at present preclude 
the possibility of an association of the Rhizopods with 
the Algae. This would almost seem natural, when we 
consider that the vesicles of many Fuci contain a viscid, 
filamentous substance, so similar to that protruded from 
the body of the Rhizopods, that the most careftd micro- 
scopic examination does not disclose the slightest diflFer- 
ence in its structure from that which mainly forms the 
body of Rhizopods. The discovery by Schultze^ of what 
he considers as the germinal granules of these beings by 
no means settles this question, since we have similar ovoid 
masses in Algse, and since, among the latter, locomotive 
forms are also very numerous.^ 

With reference to the Infusoria, I have long since ex- 
pressed my conviction that they are an unnatural com- 
bination of the most heterogeneous beings. A large 
number of them, the Desmidieae and Volvocinae, are 
locomotive AlgsB. Indeed, recent investigations seem to 
have established beyond all question the fact, that all the 
Infusoria Anentcra of Ehrenberg are Algae.^ The Ente- 
rodcla, however, are true animals, but belong to two very 
distinct types, for the VorticeUida) differ entirely from aU 

1 ScuuLTZE(M.S.),Polythalamicn, more I examine these enigmatical 

q. a., p. 24. bodies the more do they impress me 

* The recent investigations of Ehr- as being allied to the lower Algie and 

enberg and J. Miillcr, q. a., p. 113, to the Sponges, rather than to any 

note 2, indicate a very close affinity type of the animal kingdom, 

between the Thalussicolrc, the Poly- * Oomp. the works, q. a., p. 113, 

cystinac and the Rhizopods ; and the note 2. 



MODERN SYSTEMS. 291 

others. Indeed, they axe, in my opinion, the only inde- 
pendent animals of that group ; and, so far from having 
any natural aflSnity with the other Enterodela, I do not 
doubt that their true place is by the side of the Bryozoa, 
among the Mollusks, as I shall attempt to show presently. 
Isolated observations which I have been able to make 
upon Paramecium, Opalina, and the like, seem to me 
sufl&cient to justify the assumption that they disclose the 
true nature of the bulk of this group. I have seen, for 
instance, a Planaria lay eggs out of which Paramecia 
were bom, which underwent aU the changes these animals 
are known to undergo up to the time of their contraction 
into a chrysalis state ; while the Opalina is hatched from 
Distoma's eggs. I shall publish the details of these ob- 
servations on another occasion. But if it can be shown 
that two such types as Paramecium and Opalina are the 
progeny of Worms, it seems to me to foUow that aU the 
Enterodela, with the exception of the VorticeUidaB, must 
be considered as the embryonic condition of that host of 
Worms, both parasitic and free, the metamorphosis of 
which is stiU unstudied. In this connection I might 
further remark, that the time is not long past when 
Cercaria was also considered as belonging to the class of 
Infusoria, though at present no one doubts that it belongs 
to the cycle of Distoma ; and the only link in the me- 
tamorphosis of that genus which was not known is now 
supplied, since, as I have stated above, the embryo which 
is hatched from the egg laid by the perfect Distoma is 
found to be Opalina. 

All this leads to the conclusion, that a. division of the 
animal kingdom to be called Protozoa, differing from all 
other animals in producing no eggs, does not exist in 
nature, and that the beings which have been referred to 

u 2 



292 ESSAY ON CLASSIFICATION. 

it have now to be divided, and scattered, partly among 
plants in the class of Algae, and partly among animals in 
the classes of Acephala, (Vorticellse,) of Worms, (Para- 
mecium and Opalina,) and of Crustacea (Rotifera) ; the 
Vorticellae being genuine Bryozoa, and therefore Acepha- 
lous Mollusks ; while the beautiful investigations of Dana 
and Leydig have proved the Kotifera to be genuine 
Crustacea, and not Worms. 

The great type of Radiata, taking its leading features 
only, was first recognized by Cuvier, though he associated 
with it many animals which do not properly belong to it 
This arose partly from the imperfect knowledge of those 
animals at the time, but partly also from the fact that he 
allowed himself, in this instance, to deviate from his own 
principle of classification, according to which types are 
founded upon speciixl plans of structure. With reference 
to Radiata, he departed, indeed, from this view, so fai as 
to admit, besides the consideration of their peculiar plan, 
the element of simplicity of their structure as an essential 
feature in the typical character of these animals, in con- 
sequence of which he introduced five classes among 
Riuliata : the Echinoderms, Intestinal Worms, Acalephs, 
Pol}'pi, and Infusoria. In opposition to this unnatural 
association I need not repeat here what I have already 
stated of the Infusoria, when considering the case of 
Protozoa ; neither is it necessary to urge again the pro- 
priety of removing the Worms from among the Radiata 
and connecting them with the Articulata. There would 
thus remain only tlu-ee classes among Radiates, — Pol}'pi, 
Acalephs, and Echinoderms, — which, in my opinion, con- 
stitute really three natural classes in this great division, 
inasmuch as they exhibit the three different wa}'S in 
which the chai-acteristic plan of the t}'pe, radiation, is 
can-ied out, in distinct structures. 



MODERN SYSTEMS. 293 

Since it can be shown that Echinodenns are, in a 
general way, homologous in their structure with Acalephs 
and Pol3rpi, it must be admitted that these classes belong 
to one and the same great tjrpe, and that they are the 
only representatives of the branch of Radiata, assuming 
of coittse that Bryozoa, Corallinse, Sponges, and all other 
foreign admixtures, have been removed from among 
Poljrps. Now, it is this Cuvierian tjrpe of Radiata, thus 
freed of all its heterogeneous elements, which Leuckart 
undertakes to divide into two branches, each of which he 
considers coequal with Worms, Articulates, Mollusks, and 
Vertebratea He was undoubtedly led to this exaggera- 
tion of the difference existing between Echinodenns on 
one side, and Acalephs and Polypi on the other, by the 
apparently greater resemblance of Medusae and Polypi,^ 
and perhaps still more by the fact, that so many genuine 
Acalephs, such as the Hydroids, including Tubularia, 
Sertularia, Campanularia, etc., are stUl comprised by 
most zoologists in the class of Polypi 

But since the admirable investigations of J. Mliller 
have made us familiar with the extraordinary metamor- 
phosis of Echinodenns, and since the Ctenophorae and 
the SiphonophoraB have also been more carefully studied 
by Grube, Leuckart, Kolliker, Vogt, Gegenbaur, and my- 
self^ the distance which seemed to separate Echinodenns 
from Acalephs disappears entirely, for it is no exaggera- 
tion to say, that, were the Pluteus-like forms of Echino- 
denns not known to be an early stage in the transforma- 
tion of Echinodenns, they would find as natural a place 
among Ctenophorae, as the larvae of Insects among Worms. 
I therefore maintain, that Polj^i, Acalephs, and Echino- 

* We see here clearly how the con- den the primary feature of hranches, 
rideration of anatomical differences their plan, and exalted a class to the 
which characterize classes has oTerrid- rank of a branch . 



294 ESSAY ON CLASSIFICATION. 

denns constitute one indivisible primary group of the 
animal kingdom. The Polypoid character of young 
Medusae proves this as plainly as the Medusoid character 
of young Echinoderms. 

Further, nothing can be more unnatural than the transfer 
of CtenophoraB to the tjrpe of Mollusks which Vogt has 
proposed, for CtenophoraB exhibit the closest homology 
with the other Medusae, as I have shown in my paper on 
the Beroid Medusae of Massachusetts. The Ctenophoroid 
character of young Echinoderms establishes a second 
connection between Ctenophorae and the other Radiata, 
of as great importance as the first. We have thus an 
anatomical link to connect the Ctenophorae with the 
genuine Medusae, and an embryological link to connect 
them with the Echinoderms. 

The classification of Radiata may therefore stand thus : 

1st Class : Polypi; including two orders, the Actinioids 
and the Halcyonioids, as limited by Dana. 

2nd Class : Acahphce; with the following orders : Hy- 
droids, (including Siphonophorae,) Discophorae, and Cteno- 
phorae. 

3rd Class : Echinoderms; with Crinoids, Asterioids, 
Echinoids, and Holothurioids, as orders. 

The natural limits of the branch of Mollusks are easily 
detci-mined. Since the Cirripeds have been removed to 
the branch of Articulata, naturalists have generally agreed 
to consider, \nih Cuvier, the Cephalopods, Pteropods, 
Gasteropods, and Acephala as forming the bulk of this 
type, and the discrepancies between modem investigators 
have mainly resulted from the views they have taken 
respecting the Bryozoa, which some still consider as 
Polyps, while others would unite them with the Worms, 
though their affinity with the Mollusks seems to me to 



MODERN SYSTEMS. 295 

have been clearly demonstrated by the investigations of 
Milne-Edwards. Vogt is the only naturalist who con- 
siders the Cephalopoda "as built upon a plan entirely 
peculiar";^ though he does not show in what this pecu- 
liarity of plan consists, but only mentions the well-known 
anatomical differences which distinguish them from the 
other classes of the branch of MoUusks. These differ- 
ences, however, constitute only class characters, and 
exhibit in no way a different plan. It is, indeed, by no 
means difficult to homologize all the systems of organs of 
the Cephalopods with those of the other MoUusks,^ and 
with this evidence the proof is also furnished that the 
Cephalopods constitute only a class among the Mollusks. 
As to the differences in the development of the Cepha- 
lopods and the other MoUusks, the type of Vertebrata 
teaches us that partial and total segmentation of the 
yolk is not inconsistent with imity of type, as the eggs 
of Mammalia and Cyclostomata undergo a total segmenta- 
tion, while the process of segmentation is more or less 
limited in the other classes. In Birds, Reptiles, and 
Selachians^ the segmentation is only superficial ; in 
Batrachians, and most Fishes, it is much deeper; and 
yet no one would venture to separate the Vertebrata into 
several distinct branches on that account. With refer- 
ence to Bryozoa, there can be no doubt that their asso- 
ciation with Poljrpi or with Worms is contrary to their 
natural affinities. The plan of their structure is in no 
way radiate ; it is, on the contrary, distinctly and essen- 
tially bilateral ; and as soon as their close affinities with 

* VooT (C), Zoologische Briefe, Cephalous MoUusca, Tr. Roy. Soc. ; 
q. a., Tol. i, p. 361. London, 1853, p. 29. — V. Carus, 

* See Leuckabt, Ueber die Mor- System der thierischen Morphologie 
phologie, etc., q. a., p. 24, note 2. — q. a., p. 24, note 2. 

UuxLET, On the Morphology of the 



296 ESSAY ON CLASSIFICATION. 

the Brachiopods, alluded to above,^ are fiilly understood, 
no doubt will remain of their true relation to MoUosks. 
As it is not within the limits of my plan to illustrate 
here the characters of all the classes of the animal 
kingdom, I will only state further, that the branch of 
MoUusks appears to me to contain only three classes, as 
follows : — 

Ist Class : Acephala; with four orders, Bryozoa, (in- 
cluding the Vorticellae) Brachiopoda, Tunicata, and Lamel- 
libranchiata. 

2nd Class : Gasteropoda; with three orders, Pteropoda, 
Heteropoda, and Gasteropoda proper. 

3rd Class : Cephalopoda ; with two orders, Tetra- 
branchiata and Dibranchiata. 

The most objectionable modification introduced in the 
general classification of the animal kingdom, since the 
appearance of Cuvier's Rfegne Animal, seems to me to be 
the establishment of a distinct branch, now very generally 
admitted under the name of Vermes, including the 
Annulata, the Helminths, the Kotifera, and, as Leuckardt 
would have it, the Bryozoa also. It was certainly an im- 
provement upon Cuvier s system to remove the Helminths 
from the type of Eadiates ; but it was at the same time 
as tiiily a retrograde step to separate the Annelides from 
the branch of Articulata. The most minute comparison 
does not lead to the discovery of a distinct plan of 
structure, uniting all these animals into one natural 
primary group. What holds them together and keej)3 
them at a distance^ from the other Articulate groups is 
not a (liirereiit plan of stmcture, but a greater simphcity 
in theii- organizatiou.^ In bringing these animals to- 

J Chap. I, Sect. 18, p. 108. " Chap. II, Sect. 7, pp. 261-203. 

3 fcJcc above, Chap. I, Sect. 18, pp. 112, 113. 



MODERN SYSTEMS. 297 

gether, naturalists make again the same mistake which 
Cuvier committed, when he associated the Helminths 
with the Radiates, only in another way and upon a 
greater scale.^ The Bryozoa are as it were depauperated 
Mollusks, as Aphanes and Alchemilla are depauperated 
Bosacese. Rotifera are in the same sense the lowest 
Crustacea; while Helminths and AnneUdes constitute 
together the lowest class of Articulata. This class is 
connected by the closest homology with the larval states 
of Insects ; the plan of their structure is identical, and 
there exists between them only such structural diflFerences 
as constitute classes.^ Moreover, the Helminths are 
linked to the AnneUdes in the same manner as the apodal 
larvae of Insects are to the most highly organized cater- 
pillars. It may truly be said that the class of Worms 
represents, in perfect animals, the embryonic states of 
the higher Articulata. The two other classes of this 
branch are the Crustacea and the Insects, respecting the 
limits of which, as much has already been said above^ as 
it is necessary to state here. 

The classification of the branch of Articulata may, 
therefore, stand thus : — 

1st Class : Worms ; with three orders, Trematods, 
(including Cestods, Planariae, and Leeches,) Nematoids, 
(including Acanthocephala and Gordiacei,) and An- 
nelides. 

2nd Class : Crustacea ; with four orders, Eotifera, 
Entomostraca, (including Cirripeds,) Tetradecapods, and 
Decapods. 

3rd Class : Insects ; with three orders, Myriapods, 
Arachnids, and Insects proper. 

^ Compare Chap. II, Sect. 1, p. 2 16. ' Compare Chap. I, Sect, lb, p. 
' Compare Chap. 11, Sect. 2, p. 219. 116-120. 



298 ESSAY ON CLASSIFICATION. 

There is not a dissenting voice among anatomists 
respecting the natural limits of the Vertebrata as a 
branch of the animal kingdom. Their character, how- 
ever, does not so much consist in the structure of their 
backbone or the presence of a dorsal cord, as in the 
general plan of that structure, which exhibits a cavity 
above and a cavity below a solid axis. These two cavities 
are circumscribed by complicated arches, arising from the 
axis, which are made up of diflferent systems of organs, 
the skeleton, the muscles, vessels, and nerves, and include, 
the upper one the centres of the nervous system, the 
lower one the diflferent systems of organs by which assi- 
milation and reproduction are carried on. 

The number and limits of the classes of this branch 
are not yet satisfactorily ascertained. At least, natural- 
ists do not agree about them. For my part, I believe 
that the Marsupialia cannot be separated from the Placental 
Mammalia as a distinct class, since we observe, within 
the limits of another type of Vertebrata, the Selachians, 
which cannot be subdivided into classes, similar diflfer- 
cnccs in the mode of development to those which exist 
between the Marsupials and the other Mammalia. But I 
hold at the same time with other naturalists, that the 
Batrachia must be separated, as a class, from the true 
Reptiles, as the characters w^hich distinguish them are of 
the kind upon w^hich classes are founded. I am also 
satisfied that the diflferences which exist between the 
Selachians (the Skates, Sharks, and Chimaeraj) and tlie 
Fishes, are of the same kind as those which distinguish 
the Amphibians from the Reptiles proper, and justify, 
therefore, their separation, as a class, from the Fishes 
proper. I consider also the Cyclostomes as a distinct 
class, for similar reasons ; but I am still doubtful whether 



MODERN SYSTEMS. 



299 



the Ganoids should be also separated from the ordinary- 
Fishes. This, however, cannot be decided untU their 
embryological development has been thoroughly investi- 
gated, though I have already collected data which favour 
this view of the case. Should this expectation be rea- 
lized, the branch of Vertebrata would contain the follow- 
ing classes :— 

1st Class : Myzontes ; with two orders, Myxinoids 
and Cyclostomes. 

2nd Class: Fishes proper; with two orders, Ctenoids 
and Cycloids.^ 

3rd Class : Ganoids ; with three orders, Coelacanths, 
Acipenseroids, and Sauroids; and doubtftd, the Siluroids, 
Plectognaths, and Lophobranches.^ 

4th Class: Selachians; with three orders, Chimserae, 
Galeodes, and Batides. 

5th Class : Amphibians ; with three orders, CsecUise, 
Ichthyodi, and Anura. 

6th Class: Reptiles; with four orders, Serpentes, Saurii, 
Ehizodontes, and Testudinata. 

7th Class: Birds; with four orders, Natatores, GraUaB, 
Kasores, and Insessores (including Scansores and Acci- 
pitres.) 

8th Class: Mammalia; with three orders, Marsupialia, 
Herbivora, and Camivora.^ 



^ I am satisfied that this subdiyi- 
sion of the Fishes proper requires 
modifications; but I fear it would 
lead me too far, were I to discuss 
here the reasons for the changes I 
propose to introduce into it. 

■ I have observed a very curious 
and peculiar mode of locomotion in 
aU the Lophobranches, Scleroderms 
and Gymnodontes, which I have seen 
alive. They do not progress by the 
lateral motions of the vcrtebnd co- 



lumns, as other fishes do ; but chiefly 
by an undulatory movement of their 
vertical fins, resembling very much 
the mode of action of the vibratile 
membranes. In this they resemble 
the young Lepidosteus ; and I consi- 
der this fact as a new argument in 
favour of their association with the 
true Ganoids. Comp. also the re- 
marks respecting the limits of the 
Ganoids, p. 242. 
' Since this chapter was written 



300 ESSAY ON CLASSIFICATION. 

I shall avail myself of an early opportunity to inves- 
tigate more fully how far these groups of Vertebrata 
exhibit such characters as distinguish classes ; and I sub- 
mit my present impressions upon this subject, rather as 
suggestions for further researches than as matured results. 



SECTION II. 

EABLY ATTEBfPTS TO CLASSIFY AKTMAL8. 

So few naturaHsts have paid special attention to the 
foundation of the classification of the animal kingdom in 
general, that I deem it necessary to allude to the dijSer- 
cnt principles, which, at different times, have guided 
zoologists in their attempts to group animals according 
to their natural aflSnities. This, I hope, will appear the 
more acceptable, in a work at first published with special 
reference to the wants of naturalists in America, since 
few of the libraries of this continent contain even the 
leading works of our science, and many zealous students 
are thus prevented from even attempting to make them- 
selves familiar with what has thus far been done in this 
direction. 

Science began, in the introduction of names, to de- 
signate natural groups of different value with the same 
vagueness which still prevails in ordinary language in the 
use of class, order, genus, family, species ; taking them 
cither as s}Tion}Tns or substituting one for the other at 
random. Linnaeus was the first to urge upon naturalists 

Owen has published his invaluable themselves. Sec OwEir (R.), On the 

paper upon the classification of Mam- Characters, Principles of Division, 

malia, which furnishes most import- and Primary Groups of the CU«s 

ant new data for a discussion of the Mammalia ; Proceed. Linn. Society, 

true affinities of Mammalia, among lb07. 



MODERN SYSTEMS. 301 

precision in four kinds of groups in natural history, which 
he calls classes, orders, genera, and species. 

Aristotle, and the ancient philosophers generally, dis- 
tinguish only two kinds of groups among animals, 761/09 
and eZSo? (genus and species). But the term genus had a 
most unequal meaning, applying at times indiscriminately 
to any extensive group of species, and designating even 
what we now call classes as well as any other minor group. 
In the sense of class it is taken in the followiug case : 
Xe/Gff Be 7€vo9, otov 6pvi0a, xal l^Ovv (Arist., Hist. Anim., Lib. 
I, Chap. I), while etBo^ is generally used for species, as the 
following sentence shows : /col eariv etSTj TrXeio) t^Ovcjv koX 
6pvi0a)v, though it has occasionally also a wider meaning. 
The sixth chapter of the same book is the most important 
in the whole work of Aristotle upon this subject, as it 
shows to how many different kinds of groups the teim 
yevo^ is applied. Here he distinguishes between yevrj fii- 

yurra and yevtf fieyaXa and yevfx; shortly. Tept) Bk fiiyiara 
T&v ^uKoVy ek & BuupeiTcu raXXa ^cja, toS* eariv hf fiev opviffcov. 
If S* lj(0wop^ oKKo Be Kifrov^, "AXXo Be 761/09 eorl to t&v oarpa- 

KoBepfitov Tft)i/ S^ Xoi^irSiV ^wcdv ovk ean ra yevrj iieyaKa* 

oif yap irepUx^i 'jroXXcL eiBt) h/ eiBo<i, . * . . Ta S' e^ei fiev, aXX* 

ojwwfJM. This is further insisted upon anew: rov Be yevov<; 

T&p rerpairoBfov ^axov kcu ^axoTotctov etBrf p.ev elai ttoWA, dviovvfia 

Be. Here eSo^ has evidently a wider meaning than our 
term species; and the accurate Scaliger translates it by 
genus medium, in contradistinction to 761/09, which he ren- 
ders by genus summum. EZ809, however, is generally used 
for species, in the same sense as we now distinguish them ; 
and Aristotle already considers fecundity as a specific 
character, when he says, of the Hemionos, that it is called 
Bo from its likeness to the Ass, and not because it is of 
the same species ; for, he adds, they copulate and propa- 



302 ESSAY ON CLASSIFICATION. 

gate among themselves : of KaXovvrai rifilovoi Bi ofioumpra, 

ovK ova-ad, airX&<; to aino eZSov* fcaX yap o'^evovra* kcu yewAvrtu 

ef aXXi]\(ov, In another passage 70/09 applies, however, to 
a group exactly identical with our modem genus Equus: 

eirel iarip 2i/ ti yevo^ koX eirX toJ? e^ovai 'xaiTrfv, 7<oif>ovpot^ Kty- 
\ovfjUvoi<;, olov Xirrrtp kclL ovtp Koi opel koX yiw^ koI Zwto kclL to!? 
iv ^vpia ica\ovfi€va4><: ^fiiovoi^, 

Aristotle cannot be said to have proposed any regular 
classification. He speaks constantly of more or less ex- 
tensive groups imder a common appellation, evidently 
considering them as natural divisions; but he nowhere 
expresses a conviction that these groups may be arranged 
methodically, so as to exhibit the natural aflinities of 
animals. Yet he frequently introduces his remarks re- 
specting diflFerent animals in such an order and in such 
connexions as clearly to indicate that he knew their rela- 
tions. When speaking of Fishes, for instance, he never 
includes the Selachians. 

After Aristotle, the systematic classification of iinimals 
makes no progress for two thousand years, until Linnaeus 
introduces new distinctions and assigns a more precise 
meaning to the term cla&s (genius sumnuim), order (genus 
intermedium), genus (genus j^^^oximum), and species, the 
two first of which are introduced by him for the first time 
as distinct groups, under these names, into the system of 
Zoology. 



SECTION III. 

PEBIOD OF LINNJEU8. 



AMicn looking over the "Systema Natune" of Linnreus, 
taking as the stimdard of our appreciation even the twelfth 
edition, which is the last he edited himself, it is hardly 



PERIOD OF LINNiEUS. 303 

possible, in our day, to realize how great was the influ- 
ence of that work upon the progress of Zoology.^ And 
yet it acted like magic upon the age, and stimulated it to 
exertions far surpassing any thing that had been done in 
preceding centuries. Such a result must be ascribed 
partly to the circumstance that he was the first man who 
ever conceived distinctly the idea of expressing in a defi- 
nite form what he considered to be a system of nature, 
and partly also to the great comprehensiveness, simpli- 
city, and clearness of his method. Discarding in his sys- 
tem everything that could not easUy be ascertained, he 
for the first time divided the animal kingdom into dis- 
tinct classes, characterized by definite features; he also 
for the first time introduced orders into the system of 
Zoology besides genera and species, which had been 
vaguely distinguished before.^ And, though he did not 
even attempt to define the characteristics of these difierent 
kinds of groups, it is plain, from his nimierous writings, 
that he considered them all as subdivisions of a succes- 
sively more limited value, embracing a larger or smaller 
number of animals, agreeing in more or less comprehen- 
sive attributes. He expresses his views of these relations 
between classes, orders, genera, species, and varieties, by 
comparisons, in the following manner : — ^ 

^ To appreciate correctly the sue- eighth, and ninth, are reprints of the 
eessiTe improvements of the classifi- sixth ; the eleventh is a reprint of 
cation of Linnseus, we need onlj the tenth ; and the thirteenth, pub- 
compare the first edition of the Sys- lished after his death, by Qmelin, is 
tema Nature, published in 1735; a mere compilation, deserving of little 
with the second, published in 1740; confidence. 

the sixth, published in 1748; the " See above, Sect. II, p. 301. The 

tenth, published in 1758 ; and the 7/nj fi4yi<rra of Aristotle correspond, 

twelfth, published in 1 7G6, as they however, to the classes of Linnseus ; 

are the only editions he revised him- the ydmi fAtydXa to his orders. 

■elf. The third is only a reprint of ' See Systema Natune, 12th edit., 

the first, the fourth and fifth arc re- p. 13. 
prints of the second; the seventh, 



304 ESSAY ON CLASSIFICATION. 

Classis. Ordo. Genus. Species. VarieUu. 

Genus sum- Genus inter- Genus proxi- g j^ Individuum. 

mum. medium. mum. '^ 

ProvincisB. Territoria. Paroeciss. Pagi. Domicilium. 

Legiones. Oohortes. Manipuli. Oontubernia. Miles. 

His arrangement of the animal kingdom is presented 
in the following diagram, compiled from the twelfth edi- 
tion, published in 1766. 

CLASSIFICATION OF LINN^US. 

Cl. 1. Mammalia. Ord. Primates, Bruta, Ferse, Glires, Pecora, Bellu», 

Cete. 
Cl. 2. Ayes. Ord. Accipitres, Picss, Anseres, Grail se, GallinflD, Passeres. 
Cl. 3. Amphibia. Ord. Reptiles, Serpentes, Nantes. 
Cl. 4. Pisces. Ord. Apodes, Jugulares, Thoracici, Abdominales. 
Cl. 5. Imsecta. Ord. Coleoptera, Uemiptera, Lepidoptera, Neuroptera, 

Hymenoptera, Diptera, Aptera. 
Cl. 6. Vermes. Ord. Intestina, Mollusca, Testacea, Lithophyta, Zoo- 

phyta. 

In the earlier editions, up to the tenth, the class of 
Mammalia was called Quadrupedia, and did not contain 
the Cetaceans, wliich were still included among the Fishes. 
There seems never to have existed any discrepancy among 
naturalists respecting the natural limits of the chiss of 
Birds, since it w^as first characterized by Linnaeus, in a 
manner which excluded the Bats and referred them to 
the class of Mammalia. In the early editions of the 
" Systema Naturae," the class of Reptiles embraces the 
same animals as in the systems of the most recent inves- 
tigator's ; but since the tenth edition, it has been encum- 
bered with the addition of the cartilaginous and semi- 
cartilaginous Fishes, a retrograde movement suggested by 
some inaccurate obsci-vations of Dr. Garden. The class 
of Fishes is very well limited in the early editions of the 
Systema, \\ath the exception of the admission of the Ceta- 
ceans (Plagiuri), which were correctly referred to the 



PERIOD OF LINNiEUS. 305 

daas of Mammalia, in the tenth edition. In the later 
editions, however, the Cyclostoms, Plagiostoms, Chimaerae, 
Sturgeons, Lophioids, Discoboli, Gymnodonts, Scleroderms, 
and Lophobranches are excluded from it, and referred to 
the class of Eeptiles. The class of Insects,^ as limited by 
Linnseus, embraces not only what are now considered as 
Insects proper, but also the Myriapods, the Arachnids, 
and the Crustacea; it corresponds more accurately to the 
division of Arthropoda of modem systematists. The class 
of Worms, the most heterogeneous of all, includes besides 
all the Eadiata or Zoophjrtes and Mollusks of modem 
writers, also the Worms, intestinal and free, the Cirripeds, 
and one Fish (Myxine). It was left for Cuvier^ to intro- 
duce order into this chaos. 

Such, with its excellences and short-comings, is the 
classification which gave a most imexpected and unpre- 
cented impulse to the study of Zoology. It is useftd to 
remember how lately a performance, even so imperfect, 
has so greatly influenced the progress of science, in order 
to imderstand why it is still possible that so much may 
remain to be done in systematic Zoology. Nothing, 
indeed, can be more instractive to the student of Natu- 
ral History than a careful and minute comparison of the 
different editions of the " Systema Naturae '^ of Lin- 
naeus, and of the works of Cuvier and other prominent 

1 Aristotle diyides this group more ' It would be injustice to Aristotle 

correctly than Linnieus, as he admits not to mention that he already under- 

already two classes {ydtui fi4yurra) stood the relations of the animals 

among them, the Malacostraca (Cms- united into one class byLinn»u8,under 

tacea), and the Entoma (Insects), the name of Worms, better than the 

Hist. Anim., Chap. yi. He seems great Swedish naturalist. Speaking, 

also to have understood correctly the for instance, of the great genera or 

natural limits of the classes of Mam- classes, he separates correctly the 

malia and Reptiles, for he distin- Cephalopods from the other Mollusks, 

goishes the Viviparous and Oyipa- under the name of Malakia. Hist. 

Tous Quadrupeds, and nowhere con- Anim., Lib. I, Chap. ti. 
finmda Fiahet with Reptiles. Ibid. 



306 ESSAY ON CLASSIFICATION. 

zoologists, in order to detect the methods by which real 
progress is made in our science. 

Since the publication of the " Systema Naturae,*^ up to 
the time when Cuvier published the results of his ana- 
tomical investigations, all the attempts at new classifica- 
tions were, after all, only modifications of the principles 
introduced by Linnaeus in the systematic arrangement of 
animals. Even his opponents laboured under the influ- 
ence of his master spirit, and a critical comparison of the 
various systems which were proposed for the arrangement 
of single classes, or of the whole animal kingdom, shows 
that they were framed according to the same principles, 
namely, under the impression that animals were to be 
arranged together into classes, orders, genera, and species, 
according to their more or less close external resemblance. 
No sooner, however, had Cuvier presented to the scientific 
world his extensive researches into the internal structure 
of the whole animal kingdom, than naturalists vied with 
one another in their attempts to remodel the whole classi- 
fication of animals, establishing new classes, new orders, 
new genera, describing new species, and introducing all 
maimer of intermediate divisions and subdivisions, under 
the name of families, tribes, sections, etc. Foremost in 
these attempts was Cuvier himself, and next to him 
Lamarck. It has, however, often happened that the divi- 
sions introduced by the latter under new names were 
only translations into a more systematic form of the re- 
sults Cuvier had himself obtained from his dissections, 
and pointed out in his " Le9ons sur Tanatomie compar6e" 
as natural divisions, but without giving them distinct 
names. Cuvier liimself beautifully expresses the influence 
which his anatomical investigations had upon Zoology, 
and how the improvements in classification have contri- 



PERIOD OF LINN^US. 307 

buted to advance comparative anatomy, when he sajrs, in 
the prefiace to the Regne Animal^ page vi : " Je dus done, 
et cette obligation me prit im temps considerable, je dus 
fjBure marcher de fix)nt Tanatomie et la zoologie, les dis- 
sections et le classement; chercher dans mes premieres 
remarques sur Torganisation, des distributions meilleures ; 
m'en servir pour arriver d» des remarques nouvelles ; em- 
ployer encore ces remarques d» perfectionner les distribu- 
tions ; faire sortir enfin de cette f^condation mutuelle des 
deux sciences Time par Tautre, un syst^me zoologique 
propre st servir d'introducteur et de guide dans le champ 
de Tanatomie, et un corps de doctrine anatomique propre 
ik servir de d6veloppement et d'explication au systfeme 
zoologique/' 

Without entering into a detailed account of all that 
was done in this period towards improving the system of 
2kx)logy, it may suffice to say, that, before the first decade 
of this century had passed, more than twice as many 
classes as Linnaeus adopted had been characterized in this 
manner. These classes are : the Mollusks, Cirripeds, Crus- 
tacea^ Arachnids, Annelids, Entozoa (nitestinal Worms), 
Zoophytes, Eadiata, Polyps, and Infusoria. Cuvier^ ad- 
mitted at first only eight classes, Dumeril^ nine, Lamarck^ 
eleven and afterwards fourteen. The Cephalopoda, Gas- 
teropoda, and Acephala, first so named by Cuvier, are in 
the beginning considered by him as orders only in the 
class of Mollusks; the Echinoderms also, though for the 
first time circumscribed by him within their natural 
limits, constitute only an order of the class of Zoophytes, 

' * CiTTiEB (Q.), Tableau 6I6mentaire ' Lamarck (J. B. de), Syst^mo 

de rHifitoire naturelle des Animaux; des Animaux sans Vert^bres, ou Ta- 

Paris, 1798, 1 vol. 8 vo bleau g^n^ral, etc.; Paris, 1801, 1 

' DuM^BiL (A. M. C), Zoologie vol. 8vo. — H is toire naturelle des An i- 

analjtique, etc.; Paris, 1806,1vol. maux sans Vertdbres, etc.; Paris, 

Bvo. 1815-1822, 7 vols. 8vo. 

X 2 



308 ESSAY ON CLASSIFICATION. 

not to speak of the lowest animals, which, from want of 
knowledge of their internal structure, still remain in great 
confusion. In this rapid sketch of the farther subdivi- 
sions which the Classes Insecta and Worms of Linn^us 
have undergone under the influence of Cuvier, I have not, 
of course, alluded to the important contributions made to 
our knowledge of isolated classes by special writers, but 
limited my remarks to the works of those naturalists who 
have considered the subject upon the most extensive 
scale. 

Thus far no attempt had been made to combine the 
classes among themselves into more comprehensive divi- 
sions, under a higher point of view, beyond that of divid- 
ing the whole animal kingdom into Vertebrata and Inver- 
tebrata, a division which corresponds to that of Aristotle, 
into fSa evaifm and fSa avcufia. All efforts were rather 
directed towards establishing a natural series, from the 
lowest Infusoria up to Man; which, with mimy, soon be- 
came a favourite tendency, and ended in being presented 
OS a scientific doctrine by Blainville. 



SECTION IV. 

PEEIOD OF CUYIER, AND ANATOMICAL SYSTEMS. 

The most important period in the history of Zoology 
begins, however, with the year 1812, when Cuvier laid 
before the Academy of Sciences in Paris the results of 
his investigations upon the more intimate relations of 
certain classes of the animal kingdom to one another,^ 
which had satisfied him that all animals are constructed 
upon four different plans, or, as it were, cast in four dif- 

^ Add. du Mus^'um d'llistoire Naturcllc, vol. xiz; Paris, 1812. 



PERIOD OF CUVIER. 309 

ferent moulda A more suggestive view of the subject 
never was presented before to the appreciation of investi- 
gators ; and, though it has as yet by no means produced 
' all the results which certainly must flow from its further 
consideration, it has already led to the most imquestion- 
able improvements which classification in general has 
made since the days of Aristotle ; and, if I am not greatly 
mistaken, it is only so far as that fundamental prin- 
ciple has been adhered to that the changes proposed in 
our systems by later writers have proved a real progress, 
and not so many retrograde steps. 

This great principle, introduced into our science by 
Cuvier, is expressed by him in these memorable words : 
" Si Ton considfere le r^gne animal d'aprfes les principes 
que nous venons de poser, en se d^barrassant des pr6- 
jug& ^tablis sur les divisions anciennement admises, en 
n'ayant 6gard qu'Jl Torganisation et i la nature des ani- 
maux, et non pas k leur grandeur, k leur utiHt^, au plus ou 
moins de connaissance que nous en avons, ni k toutes les 
autres circonstances accessoires, on trouvera qu'il existe 
quatre formes principales, quatre plans g^n^raux, si Ton 
pent s'exprimer ainsi, d aprfes lesquels tons les animaux 
semblent avoir 6t6 model^s et dont les divisions ult^ri- 
eures, de quelque titre que les naturalistes les aient d6- 
cor6es, ne sont que des modifications assez l^g^res, fondees 
sur le d^veloppement ou Faddition de quelques parties, 
qui ne changent rien st Tessence du plan." 

It is therefore incredible to me how, in presence of 
such explicit expressions, Cuvier can be represented, as 
he still is occasionally, as favouring a division of the ani- 
mal kingdom into Vertebrata and Invertebrata.^ Cuvier, 

^ Fhrehbebo (C. G.), Die Corallenihiere des rothen Meeres ; Berlin^ 1634, 
4to., p. 30, note. 



310 ESSAY ON CLASSIFICATION. 

moreover, was the first to recognize practically the in- 
equality of all the divisions he adopts in his system ; and 
this constitutes further a great and important step, even 
though he may not have foimd the correct measure for 
aU his groups. For we must remember that at the time 
he wrote, naturalists were bent upon establishing one 
continual uniform series to embrace all animals, between 
the links of which it was supposed there were no unequal 
intervals. The watchword of their school was: Natura 
nonfacit saUum. They called their system la chaine des 
ttres. 

The views of Cuvier led him to the following arrange- 
ment of the animal kingdom : — 

CLASSIFICATION OF CUVIEE.^ 

First Branch. An im alia Vebtbbbata. 

Cl. 1. Mammalia. Orders: Bimana, Quadrumana, Camiyora, Mar- 
supialia, Rodentia, Edentata, Pachjdermata, Buminantia, Ce- 
tacea. 

Cl. 2. Birds. Ord, Accipitres, Passeres, Scansores, Gallin», Grallse, 
Palmipedes. 

Cl. 3. Reptilia. Ord. Chelonia, Sauria, Ophidia, Batrachia. 

Cl. 4. Fishes. Ist Series: Fishes Peopeb. Orrf. Acanthopterygii; — 
Abdomlnales, Subbrachii, Apodes; — Lophobranckii, Plecto- 
gnathi; 2nd Series: Chondboptebtoii. Ord, Sturiones, S^ 
lachii, Cyclostomi." 

Second Branch. An im alia Mollusca. 

Cl. 1. Cephalopoda. No subdivisiens into orders or families. 

Cl. 2. Pteropoda. No subdivisions into orders or families. 

Cl. 3. Gasteropoda. Ord, Pulmonata, Nudibranchia, Inferobranchia, 

Tectibranchia, Heteropoda, Pectinibranchia, Tubuiibranchia, 

Scutibranchia, Cjclobranchia. 

^ LelUprne animal distribu6d'apr^s gone, compare his "Tableau 61emeQ- 

son orgjinisation ; Paris, 1829, 2de tairc," q. a., p. 307; his paper, q. a,, 

6dit., 5 vols., 8vo. The classes of p. 308 ; and tbe first edition of the 

Crustacea, Arachnids, and Insects, " Riignc Animal," published in 1817, 

have been elaborated by Latreille. in 4 vols. 8vo. 

For the successive modifications the ^ Comp. ll<^^e Anim., 2de edit., 

classification of Cuvier has under- 2ud vol., pp. 128 and 383. 



PERIOD OP CUVIER. 311 

Cl. 4. AcxPHALA. Ord, Testftcea, Tunicata. 

Cii. 6. Brachiopoda. No subdiyiuonB into orders or families. 

Gil. 6. Ci&BHOPODA. No subdivisions into orders or families. 

Third Branch. Avikalia Abticulata. 

Cl. 1. AirvBLiDBS. Ord, Tubicolse, Dorsibranchise, Abranchiss. 

Cl. 2. Cbustacea. Itt Section: Malacostraca. Ord. Decapoda, Sto- 
mapoda, Amphipoda, Lsemodipoda, Isopoda. 2nd Section: 
Ebtomostraoa. Ord, Branchiopoda, Poecilopoda, Trilobitn. 

Cl. 3. A&ACHVIDB8. Ord. PulmonarisD, Trachearise. 

Cl. 4. IvBBOTS. Ord. Myriapoda, Thysanura, Parasita, Suctoria, Co- 

leoptera, Orthoptera, Hemiptera, Neuroptera, Hymenoptera, 

Lepidoptera^ Rhipiptera, Diptera. 

Fourth Branch. Ahixalia Raoiata. 

Cl. 1. EcHUiODBBMS. Ord. Pedicellata, Apoda. 

Cl. 2. IvTXSTiVAL Worms. Ord. Nematoidea (incl. Epizoa and Ento- 
goa), Pare nchyma tosa. _ . .,. -" 

Cl. 3. AcALEPHA Ord. bimpuces, IlyilrostaticsD. 

Cl. 4. PoLTPi. (Including Anthozoa, Hydroids, Biyozoa, Corallinss, 
and Spongisd.) Ord. Camosi, Gelatinosi, PoIypiariL 

Cl. 6. Ikfusoria. Ord. Rotifera and Homogenea (including Polygas- 
trica and some Algse). 

When we consider the zoological systems of the past 
century, that of Linnaeus, for instance, and compare them 
with more recent ones, that of Cuvier, for example, we 
cannot overlook the fact, that, even when discoveries have 
added little to our knowledge, the subject is treated in a 
diflferent manner; not merely in consequence of the more 
extensive information respecting the internal structure of 
animals, but also respecting the gradation of the higher 
groups. 

LinnsBUS had no divisions of a higher order than classes. 
Cuvier introduced, for the first time, four great divisions, 
which he called ** embrancheTnens" or branches, imder 
which he arranged his classes, of which he admitted three 



1. . 



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PERIOD OF CUVIER. 



313 



equality between all the divisions of Cuvier is, no doubt, 
partly owing to the state of Zoology and of zoological 
museums at the time he wrote, and to his detennination 
to admit into his work only such representatives of the 
animal kingdom as he could, to a greater or less extent, 
examine anatomically for himself ; but it is also partly to 
be ascribed to his conviction, often expressed, that there 
is no such uniformity or regular serial gradation among 
animals as many naturalists have attempted to introduce 
into their classifications. 



CLASSIFICATION OF LAMARCK. 

Hisioire natnrelle des Animaux sans yert^bres, etc.; Paris, 1815-1822, 7 
Tols. 8to. — A second edition with notes has been published by Messrs. Des 
Hajes and Milne-Edwards; Paris, 1835-1843, 10 vols. 8to. — For the suc- 
cessive modifications this classification has undergone, see also : Sjst^me des 
animaux sans vert^bres, etc.; Paris, 1801, 8vo. — ^Philosophic zoologique, 
etc. ; Paris, 1809, 2 vols. 8vo. — ^Extrait du Cours de Zoologie du Mus6um 
d'Histoire naturelle, etc.; Paris, 1812, 8vo. 



INVEBTEBRATA. 

I. Apathetic Aiiiiialb. 

Cl. 1. Ihfubobia. Ord. Nuda, Appendi- 
culata. 

Cl. 2. Polypi. Ord, Ciliati (Rotifera), De- 
nudati (Hydroids), Yaginati (An- 
thozoa and Bryozoa), and Natantes 
(Crinoids, and some Halcyonoids). 

Cl. 3. Badiabia. Ord, Mollia (Acale- 
phse), Echinoderms (including Ho- 
lothurise and Actiniae). 

Cl. 4. TvvioATA. Ord. Bothryllaria (Com- 
pound Ascidians), Ascidia (Sim- 
ple Ascidians). 

Cl. 5. Ybbmbs. Ord. MoUes and Rigi- 
duli (Intestinal Worms and Gor- 
dius), Hispiduli (Nais), Epizoarise 
(Epizoa, Lemteans). 



Do not feel, and move 
only by their excited 
irritability. No brain, 
>'nor elongated medul- 
lary mass; no senses; 
forms varied ; rarely ar- 
ticulations. 




314 



ESSAY ON CLASSIFICATION. 



II. Sensitiyb Avixals. 

Cl. 6. Insects. (Hexapods). (M, Apte- 
ra, Diptera, Hemipt^ra, Lepidopie- 
ra, Hjmenopteray Nearoptera^ Or- 
thoptera, Coleoptera. 

Cu 7. A&ACHXIP8. Ord, Antennato-trache- 
ales (Thysanuia and Mjriapoda), 
Exantennato-tracheales and Exan- 
tennato-branchiales (Arachnids pro- 
per). 

Cl. 8. Crustacea. Ord. Heterobranchia 
(Branchiopoda, Isopoda, Amphipo- 
da, Stomapoda), and Homobranchia 
(Decapoda). 

Cl. 9. Annelids. Ord, Apoda, Anten- 
nata, Sedentaria. 

Cl. 10. CiBBiPEDS. Ord. Sessilia and Pe- 
dunculata. 

Cl. 11. CoNCHiFEBA. Ord. Dimyaria, Mo- 
nomyaria. 

Cl. 12. Mollusks. Ord. Pteropoda, Gas- 
teropoda, Trachellpoda, Cephalopo- 
da, Heteropoda. 



Feely but obtain frooi 
their sensatioDS onlj 
perceptions of objects, 
a sort of simple ideas, 
which they are unable 
to combine to obtain 
complex ones. No Ter- 
tebral column ; a brain 
and mostly an elongated 
medullary mass; some 
distinct senses; muscles 
attached under the skin; 
form symmetrical, the 
parts being in pairs. 



VERTEBBATA. 



III. Intelligent Animals. 
Cl. 13. Fishes. 
Cl. 14. Reptiles. 
Cl. 15. Birds. 
Cl. 1G. Mammalia. 



< 



Feel; acquire preservable ideas; per- 
form with them operations by which they 
obtain others ; are intelligent in different 
degrees. A Tertebral column; a brain 
and a spinal marrow ; distinct senses ; the 
muscles attached to the internal skeleton ; 
form symmetrical, the parts being in pairs. 



It is not easy to appreciate correctly the system of 
Lamarck, as it combines abstract conceptions with struc- 
tm-al considerations, and an artificiiil endeavour to ar- 
range all animals in continuous series. The primary 
subdivision of the animal kin^jdom into Invertebrata and 
Vertebrata^ corresponds, as I have stated above, to that 
of Anal ma and Enaima of Aristotle. The three leading 
groups designated imder the name of Apathetic, Scnsi- 

^ See above, Chap. 2, Sect. 1. 



PERIOD OF CUVIEE. 315 

tive, and Intelligent animals, are an imitation of the four 
branches of Cuvier; but, far from resting upon such a 
definite idea as the divisions of Cuvier, which involve a 
special plan of structure, they are founded upon the 
oLumption that the psychical faculties of animals present 
a serial gradation, which, when apphed as a principle of 
classification, is certainly not admissible. To say that 
neither Infusoria, nor Polypi, nor Eadiata, nor Tunicata, 
nor Worms feel, is certainly a very erroneous assertion. 
They manifest sensations quite as distinctly as many of 
the animals included in the second type, which are called 
Sensitive. And as to the other assertion, that they move 
only by their excited irritabiUty, we need only watch the 
Starfishes to be satisfied that their motions are deter- 
mined by internal impulses, and not by external excita- 
tion. Modem investigations have shown that most of 
them have a nervous system, and many even organs of 
the senses. 

The Sensitive animals are distinguished fix)m the third 
type, the Intelligent animals, by the character of their 
sensations. It is stated, in respect to the Sensitive ani- 
mals, that they obtain fix)m their sensations only percep- 
tions of objects, a sort of simple ideas which they are 
imable to combine so as to derive fix)m them complex 
ones, while the Intelligent a,nimals are said to obtain 
ideas which they may preserve, and to perform with 
them operations by which they arrive at new ideas. They 
are said to be Intelligent. Even now, fifty years after 
Lamarck made those assertions, I doubt whether it is 
possible to distinguish in that way between the sensa- 
tions of the Fishes, for instance, and those of the Cepha- 
lopods. It is true, the structures of the animals called 
Sensitive and InteUigent by Lamarck differ greatly, but 



316 ESSAY ON CLASSIFICATION. 

a large number of his Sensitive aniTnala are constructed 
upon the same plan as many of those he includes among 
the Apathetic. They embrace, moreover, two dijfferent 
plans of structure, and animal psychology is certainly not 
so far advanced as to afford the least foundation for the 
distinctions here introduced. 

Even from his own point of view, his arrangement of 
the classes is less perfect than he might have made it, as 
the Annelids stand nearer to the Worms than the Insects, 
and are very inferior to them. Having failed to perceive 
the value of the idea of plan, and having substituted for 
it that of a more or less complicated structure, Lamarck 
unites, among his Apathetic animals. Radiates (the Polypi 
and Radiaria) with MoUusks (the Tunicata) and with 
Articulates (the Worms). Among the Sensitive animals, 
he unites Articulates (the Insects, Arachnids, Crustacea, 
Annelids, and Cirripeds) with MoUusks (the Conchifera, 
and the MoUusks proper). Among the Intelligent ani- 
mals, he includes the ancient four classes of Vertebrates, — 
the Fishes, Reptiles, Birds, and MammaUa. 

CLASSIFICATION OF DE BLAINVILLE.^ 

1. Sub-Kingdom, Artiomorpha or Artiozoaria. Form bilateral. 
First Type : Obteozoaria. (Vertebrata.) 
Sub-Type : Vivipara. 

Cl. 1. PiLiFEBA, or Mammifera. Ist. Monadelphya. 2nd. 
Didelpbya. 
Sub-Type: Ovipara, 

Cl. 2. Pennifeba, or Aves. 
Cl. 3. Squamifeba, or Rcptilia. 
Cl. 4. NuDiPELLiFEKA, or Ampbibia. 
Cl. 5. PiNMFEBA, or Pisces. 
A nosteozoaria. 
Second Type: Entomozoaria. (Articulata.) 

Cl. 6. Hex A POD A. (Insecta proprie sic dicta.) 

' De rOrganisatioD dcs Auimaux ; Paris, 1822, 1 vol. 8vo. 



PERIOD OP CUVIER. 317 

Cik 7. OcTOPODA. (Arachnida.) 

Cl. 8. Dbcapoda. (Crustacea, Decapoda, and Limulus.) 

Cl. 9. Hetbbopoda. (Squilla, Entomostracay and Epizoa.) 

Cl. 10. Tetradecapoda. (Amphipoda and Isopoda.) 

Cl. 11. Mtbiapoda. 

Cl. 12. Chatopoda. (Annelides.) 

Cl. 13. Apoda. (Hinido, Cesioidea, ABcaris.) 

Third Tjpe : Malbetozoabia. 

Cl. 14. Nematopoda. (Cirripedia.) 
Cl. 15. PoLTPLAXiPHOBA. (Chiton.) 

Fourth Type : Malacozoabia. (Mollusca.) 

Cl. 16. Cephalophoba. Dioica (Cephalopoda and Gastero- 
poda, p. p.), Hermaphrodita and Monoica (Gastero- 
poda reliqua). 

Cl. 17. AoEPHALOPHOBA. Palliobranchia (Brachiopoda), La- 
mellibranchia (Acephala), Heterobranchia (Ascidlse.) 

i. Sub-Kingdom. Aetinomorpha or Aetinozoaria, Form radiate. 

Cl. 18. Ajteelidaeta, or Gastrophjsaria (Sipunculus, etc.) 

Cl. 19. Cebatodebmia. (Echinodermata.) 

Cl. 20. Abacheodebmabia. (Acalephse.) 

Cl. 21. ZoAETHABiA. (Actinis.) 

Cl. 22. PoLTPiABiA. (Polypi tentaculis simplicibus), (An- 

thozoa and Brjozoa.) 
Cl. 23. ZooPHTTABiA. (Polypi tentaculis compositis), Hal- 
cyonoidea.) 

3. Sub-Kingdom, ffeteromorpha or Heterozoaria, Form irregular. 
Cl. 24. Spoeoiabla. (Spongiee.) 
Cl. 25. MoEADABiA. (Infusoria.) 
Cl. 26. Deedbolithabia. (CorallinsD.) 

The classification of De Blainville resembles those of 
Lamarck and Cuvier much more than a diagram of the 
three would lead us to suppose. The first of these sys- 
tems is founded upon the idea that the animal kingdom 
forms one graduated series ; only that De Blainville in- 
verts the order of Lamarck, beginning with the highest 
ftnimalft and ending with the lowest. With that idea is 
blended, to some extent, the view of Cuvier, that anima l s 
are framed upon different plans of structure ; but so im- 
perfectly has this view taken hold of De Blainville, that. 



318 ESSAY ON CLASSIFICATION. 

instead of recognizing at the outset these great plans^ he 
allows the external form to be the leading idea upon 
which his primary divisions are founded, and thus he 
divides the animal kingdom into three sub-kingdoms : the 
first including his Artiozoaria, with a bilateral form; 
the second his Actinozoaria, with a radiated form; and 
the third his Heterozoana^ with an irregular form (the 
Sponges, Infusoria, and Corallines). The plan of struc- 
ture is only introduced as a secondary consideration, upon 
which he establishes four types among the Artiozoaria: 
1st. The Osteozoaria, corresponding to Cuvier's Verte- 
brata; 2nd. The Entomozoaria, corresponding to Cuvier's 
Articulata ; 3rd. The Malentozoaria, which are a very 
artificial group, suggested only by the necessity of esta- 
blishing a transition between the Articulata and Mol- 
lusca; 4th. The Malacozoaria, corresponding to Cuvier's 
Mollusca. The second sub-kingdom, Actinozoaria, cor- 
responds to Cuvier's Radiata, while the third sul>king- 
dom, Heterozoaria, contains organized beings which for 
the most part do not belong to the animal kingdom. 
Such at least are his Spongiaria and Dendrolitharia, whilst 
his Monadaria answer to the old class of Infusoria, alx)ut 
which enough has already been said above. It is evident, 
that what is correct in this general arrangement is bor- 
rowed from Cuvier; but it is only justice to De Blainville 
to say, that, in the hmitation and arrangement of the 
classes, he has introduced some valuable improvements. 
Among Vertebrata, for instance, he has distinguished, for 
the first time, the class of Amphibia from the true Rep- 
tiles. He was also the first to remove the Intestinal 
Worms from among the Radiata to the Articulata ; but 
the establishment of a distinct type for the Cirripedia and 
Chitons was a very mistaken conception. Notwithstimd- 



PERIOD OP CUVIER. 319 

ing some structural pecuKarities, the Chitons are built 
essentially upon the same plan as the MoUusks of the 
clasd Gasteropoda, and the investigations made not long 
after the publication of De Blainville's system have left 
no doubt that Ciiripedia are genuine Crustacea. The 
supposed transition between the Articulata and Mollusks, 
which De BlainviUe attempted to establish with his type 
of Malentozoaria, certainly does not exist in nature. 

If we apply to the classes of De Blainville the test 
introduced in the preceding chapter, it wiU be obvious 
that his Decapoda, Heteropoda, and Tetradecapoda par- 
take more of the character of orders than of that of 
classes, whilst among Mollusks, his class Cephalophora 
certainly includes two classes, as he has himself acknow- 
ledged in his later works. Among Eadiata his classes 
Zoantharia, Polj^iaria, and Zoophytaria partake again of 
the character of orders and not of that of classes. One 
great objection to the system of De Blainville is the use- 
less introduction of so many new names for groups which 
had already been correctly limited and well named by his 
predecessors. He had, no doubt, a desirable object in 
view in doing this, — he wished to remove some incorrect 
names ; but he extended his reform too far when he 
undertook to change those also which did not suit his 
system. 

CLASSIFICATION OF EHRENBERG. 

The characteristics of the following twenty-eight classes of animals, with 
a twenty-ninth for Man alone, are giyen more fully in the Transactions of 
the Academy of Berlin for 1836, in the paper q. a., p. 208. 

Ist Cycle : Nations. Mankind, constituting one distinct class, is charac- 
terized by the equable deyelopment of all systems of organs, 
in contradistinction of the 

2nd Cycle: Animals, which are considered as characterized by the promi- 
nence of single systems. These are dirided into : 



320 



ESSAY ON CLASSIFICATION. 



A. Myeloneura. 

I. NuTBiBNTiA. Warm-bloodedVer- I II. Obphahozoa. Cold-blooded Ye- 
tebrata, taking care of their tebrata, taking no cue of 



young. 
Cl. 1. Mammalia. 
Cl. 2. Birds. 



their young. 
Cl. 3. Amphibia. 
Cl. 4. P18OB8. 



A, SphygfMzoa, Cordata. 

Circulation marked by a heart 
or pulsating vessels. 

III. Aetioulata. Real articulation, 
marked by rows of ganglia 
and their ramifications. 
Cl. 6. Insects. 
Cl. 6. Arachnoidba. 
Cl. 7. Crustacea (including 
Entomostraca, Cirripe- 
dia, and Lernaea). 
Cl. 8. Annulata. (The genu- 
ine Annelids, exclusive 
ofNais.) 
Cl. 9. SoMATOTOMA. (Naidina.) 

IV. Mollusca. No articulation. 
Ganglia dispersed. 

Cl. 10. Cephalopoda. 

Cl. 11. Pteropoda. 

Cl. 12. Gasteropoda. 

Cl. 13. Acephala. 

Cl. 14. Brachiopoda. 

Cl. 15. TuNicATA.(A8cidi»8im- 

plices.) 
Cl. 16. AoGREGATA. (Ascidifc 

compositce.) 



B. Ganglioneura. 



B. Asphycta VobcuIom. 
Vessels without pulsation. 
V. TuBULATA. No real articulation. 
Intestine, a simple sac or 
tube. 
Cl. 17. Brtozoa. 
Cl. 18. DiMORPHiEA. (Hydio- 

ids.) 
Cl. 19. TuRBELLARiA. (Rhab- 
docoela : Derostomai 
Turbella, Vortex.) 
Cl. 20. Nematoidba. (Entozoa, 
with simple intestine; 
also Gk>rdiu8 and An- 
guillula.) 
Cl. 21. Rotatoria. 
Cl. 22. EcHiKoiDEA. (Echinus, 
Holothuria, Sipuncu- 
lus.) 

VI. Racemifera. Intestine divided, 
or forked, radiating, dendri- 
tic, or racemose. 
Cl. 23. Asteroidea. 
Cl. 24. AcALEPH^. 
Cl. 25. Anthozoa. 
Cl. 26. Trematodea. (Ento- 
zoa with ramified in- 
testine, also Cercaria.) 
Cl. 27. Complanata. (Dendro- 
coela, Planaria, etc.) 

Cl. 28. POLYOASTRICA. 

The system of Zoology published by Ehrenberg in 
1836 presents many new views in almost all its pecu- 



ANATOMICAL SYSTEMS. 321 

liarities. The most striking of its features is the prin- 
ciple laid down that the type of development of nniiTinlfl 
is one and the same from Man to the Monad, impljdng a 
complete negation of the principle advocated by Cuvier, 
that the fom* primary divisions of the animal kingdom 
are characterized by different plans of structure. It is 
very natural that Ehrenberg, after having illustrated so 
fully and so beautifully as he did the natural history of 
many organized beings, which, up to the publication of 
his investigations, were generally considered as entirely 
homogeneous ; after having shown how highly organized 
and complicated the internal structure of many of them 
is ; after having proved the fiJlacy of the prevailing 
opinions respecting their origin,— should have been led to 
the conviction that there is, after all, no essential differ- 
ence between these animals, which were then regarded as 
the lowest, and those which were placed at the head of 
the animal creation. The investigator who had just 
revealed to the astonished scientific world the compli- 
cated systems of organs which can be traced in the body 
of microscopically small Rotifera must have been led 
irresistibly to the conclusion that aU animals are equally 
perfect, and have assumed, as a natural consequence of 
the evidence he had obtained, that they stand on the 
same level with one another, as far as the complication 
of their structure is concerned. Yet the diagram of his 
own system shows that he himself could not resist the 
internal evidence of their unequal structural endowment. 
Like all other naturalists, he places Mankind at one end 
of the animal kingdom, and such types as have always 
been considered as low at the other end. 

Man constitutes, in his opinion, an independent cycle, 
that of nations, in contra-distinction to the cycle of 

Y 



322 ESSAY ON CLASSIFICATION. 

animals, which he divides into Myeloneuba, those with 
nervous marrow (the Vertebrata,) and Ganglioneura, 
those with ganglia (the Invertebrata.) The Vertebrata 
he subdivides into Nvtrientia, those which take care of 
their yoimg, and OrpJianozoa, those which take no care 
of their young ; though this is not strictly true, as there 
are many Fishes and Reptiles which provide as carefully 
for their young as some of the Birds and Mammalia, 
though they do it in another way. The Invertebrata are 
subdivided into Sphygmozoa, those which have a heart 
or pulsating vessels, and Asphycta, those in which the 
vessels do not pulsate. These two sections are further 
subdivided : the first, into Articulata with real articula- 
tions, and rows of ganglia and Mollusks without articula- 
tion and with dispersed ganglia ; the second, into Tubulata 
with a simple intestine, and Racemifera with a branching 
intestine. These characters, which Ehrenberg assigns to 
his leading divisions, imply necessarily the admission of 
a gi-adation among animals. He thus negatives, in the 
form in which he expresses the results of his investiga- 
tions, the very principle which lie intends to illustrate by 
his diagTam. The peculiar view of Elu:enberg, that all 
animals are equal in the perfection of their organiziition, 
might be justified, if it was qualified so as to imply a 
relative perfection, adapted in all to the end of their 
special mode of existence. As no one observer has con- 
tributed more extensively than Ehrenberg to make known 
the complicated structure of a host of living beings, which 
before him were almost universally believed to consist of 
a sim])le mass of homogeneous jelly, such a \'iew would 
naturally be expected of him. But this qualified pi^r- 
fection is not what he moans. He does not wish to 
convoy the idea that all animals are equally perfect in 
thoir way, for ho states distinctly that " Infusoria have 



ANATOMICAL SYSTEMS. 323 

the same sum of systems of organs as Man," and the whole 
of his system is intended to impress emphatically this 
view. The separation of Man from the animals, not 
merely as a class but as a still higher division, is especially 
maintained upon that ground. 

The principle of classification adopted by Ehrenberg 
is purely anatomical; the idea of type is entirely set 
aside, as is shown by the respective position of his 
classes. The Myeloneura, it is true, correspond to the 
branch of Vertebrata, and the Sphygmozoa to the Articu- 
lata and Mollusca ; but they are not brought together on 
the ground of the typical plan of their structure, but 
because the first have a spinal marrow, and the other a 
heart or pulsating vessels with or without articulations 
of the body. In the division of Tubulata it is still more 
evident how the plan of their structure is disregarded, as 
that section embraces Kadiata, (the Echinoidea and the 
Dimorphsea,) Mollusca, (the Bryozoa,) and Articulata, (the 
Turbellaria, the Nematoidea, and the Rotatoria,) which 
are thus combined simply on the groimd that they have 
vessels which do not pulsate, and that their intestine is a 
simple sac or tube. The Racemifera contain also animids 
constructed upon different plans, united on account of the 
peculiar structure of the intestine, which is either forked 
or radiating, dendritic or racemose. 

The limitation of many of the classes proposed by 

Ehrenberg is quite objectionable, when tested by the 

principles discussed above. A large proportion of them 

are, indeed, foimded upon ordinal characters only, and 

not upon class characters. This is particularly evident 

with the Rotatoria, the Somatotoma, the Turbellaria, the 

Nematoidea, the Trematodea, and the Complanata, all of 

which belong to the branch of Articulata. Tlie Tunicata, 

Y 2 



324 ESSAY ON CLASSIFICATION. 

the Aggregata, the Brachiopoda, and the Bryozoa are also 
only orders of the class Acephala. Before Echinoderms 
had been so extensively studied as of late, the separation 
of the Echinoidea from Asteroidea might have seemed 
justifiable ; at the present day it is totally inadmissible. 
Even Leuckart, who considers the Echinoderms as a 
distinct branch of the animal kingdom, insists upon the 
necessity of imiting them as a natural group. As to the 
Dimorphaea, they constitute a natural order of the class 
AcalephaB, which is generally known by the name of 
Hydroids. 

CLASSIFICATION OF BURMEISTER, 

The following diagram is compiled from the author^s Geschichte der 

Sch6pfung ; Leipzig, 1843, 1 voL Sto. 

Tjpe I. Ibregulab Animals. 

Ist Sub- Type. Cl. 1. Infusoria. 
Type II. Regular Animals. 

2nd Sub-Type. Cl. 2. Polypina. Ord, Bryozoa, Anthozoa. 
3rd Sub-Type. Cl. 3. Radiata. Ord, AcalephaB, £chinodermata, 

Scytodermata. 
Type III. Symmetrical Animals. 

4th Sub-Type. Cl. 4. Mollusca. Ord. Perigymna (Tunicata); Cor- 

mopoda (Acephala) ; Brachiopoda, Cephalophora 
(Pteropoda and Qasteropoda) ; Cephalopoda. 
5th Sub-type. Arthrozoa. 

Cl. 5. Vermes. Ord. Ilelminthes, Trematodes, and 

Annulati. 
Cl. 6. Crustacea. 1°. Ostracoderma. Ord. Prothes- 
mia (Cirripedia, Siphonostoma, and Rotatoria) ; As- 
pidostraca (Entomostraca : Lophyropoda, Phyllopo- 
da, Paecilopoda, Trilobitse). 2°. Malacostraca. 
Ord. Thoracostraca (Podophthalma) ; and Arthro- 
straca (Edriophthalma). 
Cl. 7. Arachnoda. Ord. Myriapoda, Arachnidas. 
Cl. 8. Insecta. Ord. Rhynchota, Synistata, Antliata, 
Piezata, Glossata, Eleutherata. 
Cth Sub-type. Ostkozoa. (Vertebrata.) 

Cl. 9. Pisces. 
Cl. 10. Amphibia. 
Cl. 11. Ayes. 
Cl. 12. Mammalia. 



ANATOMICAL SYSTEMS. 



325 



The general arrangement of the classification of Bnr- 
meister recalls that of de Blainville ; only that the order 
is inverted. His three tjrpes correspond to the three 
Bubkingdoms of de Blainville : the Irregular Animals to 
the Heterozoaria* the Regular Animals to the Actinozoaria, 
and the Symmetrical Animals to the Artiozoaria ; while 
his subtypes of the Symmetrical Animals correspond to 
the types de Blainville admits among his Artiozoaria, 
with this important improvement, however, that the 
Malentozoaria are suppressed Burmeister reduces, un- 
happily, the whole branch of Mollusks to one single class. 
The Arthrozoa, on the contrary, in the investigation of 
which Burmeister has rendered eminent service to science, 
are presented in their true light. In his special works,^ 
his classification of the Articulata is presented with more 
details. I have no doubt that the correct views he 
entertains respecting the standing of the Worms in the 
branch of Articulata are owing to his extensive acquaint- 
ance with the Crustacea and Insects, and their meta- 
morphoses. 



CLASSIFICATION OF OWEN. 

The following diagram is compiled from R. Owen^s Lectures on the Com- 
paratiye Anatomy and Physiology of the Inyertebrate Animals ; 2nd edit., 
London, 1855, 1 vol. 8to. 



Proyince. Vebtbbbata. Myelencephala. (Owen.) 

Cl. Mammalia. 
Cl. Ayes. 
Cl. Reptilia. 



1 



The olMses Mammalia, Ayes, and Reptilia, are not yet included 
in the second Tolume of the" I/eclures," the only one relating to 
Vertebrata thus far published. 



1 These works are: Beitrage zur 
Naturgeschichte der Rankenfasser 
(Cirripedia) ; Berlin, 1834, 1 vol. 4to. 
— Handbuch der Entomologie ; Ber- 
lin, 1832-47, 5 vols. 8vo.; Engl, by 
W. E. Shuckard, London, 1836.— Die 
Organisation der Trilobiten,au8 ihrcn 



lebenden Verwandten entwickelt ; 
Berlin, 1843, 1 vol. 4to.; Engl, by the 
Ray Society, London, 1847, I vol. 
fol. Compare also his recent work, 
Zoonomische Briefe, allgemeine Dar- 
stellungder thierischen Organisation; 
Leipzig, 1856, 2 vols. 8vo. 



326 ESSAY ON CLASSIFICATION. 

Cl. Pisces. Ord, Dermopteri, Malacopfeori^ Pharyngognathiy Anican- 
thini, Acanthopteri, Plectognathi, Lophobranchii, Q&noidei, Pro- 
topteri, Holocephali, Plagiostomi. 
Province. Artioulata. Homogangliata. (Owen.) 

Cl. Abaohnida. Ord» Dermophysa, Trachearia, Pulmotrachearia, and 
Pulmonaria. 

Cl. IirsEOTA. Svh-^iass: Mtriapoba. Ord, Chflognatha and Chilo- 
poda. Sztb-dois: Hexapoba. Ord, Aptera, Diptera^ Lepido- 
ptera, H jmenoptera, Homoptera, Strepsiptera, Neuroptera, Or- 
thoptera, and Coleoptera. 

Cl. Crustacea. Sub-class : Ektomost&aoa. Ord, Trilobitea, Xipho- 
sura, Phjllopoda, Cladocera, Osiracopoda, Copepoda. Sub-doss: 
Malacostraca. I°. Edriophthalma. Ord, Lsomodipoda, ho- 
poda, Amphipoda. 2°. Podophthalma. Ord, Stomapoda, De- 
capoda. 

Cl. Epizoa. Ord, Cephaluna, Brachiuna, and Onchnna. 

Cl. Annellata. Ord. Suctoria, Terricola, Errantia, Tubicola. 

Cl. Cirripedia. Ord, Thoracica, Abdominalia, and Apoda. 
Province. Mollusca. Heterogangliata. (Owen.) 

Cl. Cephalopoda. Ord, Tetrabianchiata and Dibranchiata. 

Cl. Qasteropoda. A. Monobcia : Ord, Apneusta (R5I1.), Nudibran- 
chiata, Inferobranchiata, Tectibranchiata, Pulmonata. B. Di<b- 
CIA. Ord, Nucleobranchiata, Tabulibranchiata, Cyclobranchi- 
ata, Scutibranchiata, and Pectinibranchiata. 

Cl. Pteropoda. Ord, Thecosomata and Qjmnosomata. 

Cii. Lamellibranchiata. Ord, Monomyaria and Dimyaria. 

Cl. Brachiopoda. Only subdivided into families. 

Cl. Tunicata. Ord. Saccobranchiata and Tseniobranchiata. 
Sub-province. Radiaria.^ 

Cl. EcniNODERMATA. Ord, Crinoidea, Asteroidea, Echinoidea, IIolo- 
thurioidea, and Sipunculoidea. 

Cl. Bryozoa. Only subdivided into families. 

Cl. Anthozoa. Only subdivided into families. 

Cl. AcALEPHiE. Ord. Pulmograda, Ciliograda, and Physograda. 

Cl. Htdrozoa. Only subdivided into families. 
Sub-province. Eittozoa. 

Cl. C<ELELMiirTHA. Ord, Gordiacea, Nematoidea, and Onchopbora. 

Cl. Sterelmimtha. Ord, Tasnioidea, Trematoda, Acanthocepbala. — 
Turbellaria. 
Sub-province. Infusoria. 

Cl. Rotifera. Only subdivided into families. 

Cl. Poltoastria. Ord. Astoma, Stomatoda. — Rbizopoda. 

* Id the first edition of the work three sub-provinces, Radiaria, Ento- 
<jUotcd above, published in 1843, the zoa, and Infusoria, are considered as 



ANATOMICAL SYSTEMS. 327 

The classification with which Owen^ introduces his 
" Lectures on Comparative Anatomy'' is very instructive, 
as showing, more distinctly than other modem systems, 
the imfortunate ascendancy which the consideration of the 
complication of structure has gained of late over the idea 
of plan. His provinces, it is true, correspond in the main 
to the branches of Cuvier, with this marked difference, 
however, that he does not recognize a distinct province 
of Eadiata coequal with those of Mollusca, Articulata, and 
Vertebrata, but only admits Eadiaria as a subprovince on 
a level with Entozoa and Infusoria. Here the idea of 
simplicity of structure evidently prevails over that of 
plan, as the subprovinces Eadiaria, Entozoa, and In- 
fusoria embrace, besides true Eadiata, the lowest types of 
two other branches, MoUusks and Articulates. On the 
other hand, his three subprovinces correspond to the first 
three types of von Siebold ; the Infusoria^ of Owen em- 
bracing the same animals as the Protozoa of Siebold, his 
Entozoa^ the same as the Vermes, and his Eadiaria the 
same as the Zoophyta, with the single exception that 
Owen refers the Annellata to the province of Articulata, 
whilst Siebold includes them among his Vermes. Beyond 

one sub-kingdom called Radiata, in orders and families were only added 

contradistinction of the sub-kingdoms, to the second edition in 1855. I 

Mollusca, Articulata, and Vertebrata, mention this simply to preyent the 

and that sub-kingdom is subdivided possibility of bemg understood as 

into two groups, Nematoneura and ascribing to Owen aJl those subdivi- 

Acrita, sions of the classes which he admits, 

1 I haye given precedence to the and which do not appear in the sys- 

classification of Owen over those of tems considered before his. 
von Siebold and Stannius, Milne- ' The Rhizopoda are considered as 

Edwards, Leuckart, etc., because the a group coequal to Rotifera and Po- 

first edition of the ^' Lectures on Com- lygastria, on p. 16 of the " Lectures^*; 

parative Anatomy" was published in but on p. 59 they stand as a sub- 

1843 ; but in estimating its features, order of Polygastria. 
as expressed in the preceding dia- ' The Turbellaria are represented 

gram, it should bo borne in mind, as an independent group on p. 16, 

that, in the first edition, the classes and referred as a sub-order to the 

alone arc considered, and that the Trematoda on p. 118. 



328 ESSAY ON CLASSIFICATION. 

this, the types of Mollusca and Articulata (Arthropo<la) 
of the two distinguished anatomists entirely agree. The 
position assigned by Owen to the provinces Articulata 
and Mollusca, not one above the other, but side by side 
of one another,! is no doubt meant to express his con- 
viction that the complication of structure of these two 
types does not justify the idea that either of them stands 
higher or lower than the other; and this is perfectly 
correct. 

Several groups, established by previous writers as 
families or orders, are here admitted as classes. His 
class Epizoa, which is not to be confounded with that 
established by Nitzsch under the same name, corresponds 
exactly to the famUy called Lernees by Cuvier. His 
class Hydrozoa answers to the order Hydroida of 
Johnston, and is identical with the class called Dimorph^a 
by Ehrenberg. His class Ccelelmintha corresponds to the 
order of Intestinaux Cavitaires established by Cu\aer, 
with the addition of Gordius ; while his class Sterel- 
MiNTHA has the same circumscription as the order In- 
testinaux Parenchymateux of Cuvier. Generally 
speaking, it should not be understood that the secondaiy 
divisions mentioned by the different authors, whose 
systems I have analyzed here, were established by them. 
They are frequently borrowed from the results obtained 
by special investigators of isolated classes. But it would 
lead me too far to enter here into a discussion of all these 
details. 

Tliis growing resemblance of the modem systems of 
Zoolog}^ is a ver}' favourable sign of our times. It would, 

' Fn)ni want of space, I have been culata an<l Mollusca one below the 

compelleJ, in reproducing the classi- other upon my page; according to 

fication of Owen in the preceding his views they should stand on a 

diagram, to place his provinces Arti- level, side by side with one another. 



ANATOMICAL SYSTEMS. 329 

indeed, be a great mistake to assume that it is solely 
owing to the influence of different authors upon one 
another ; it is, on the contrary, to a very great extent, 
the result of our better acquaintance with Nature. When 
investigators at all conversant with the present state of 
our science must possess nearly the same amoimt of 
knowledge, it is self-evident that their views can no 
longer differ so widely as they did when each was fa- 
miliar with a part only of the subject. A deeper insight 
into the animal kingdom must, in the end, lead to the 
conviction that it is not the task of zoologists to introduce 
order among animals, but that their highest aim should 
be simply to read the natural affinities which exist among 
them, so that the more nearly our knowledge embraces 
the whole field of investigation, the more closely will our 
opinions coincide. 

As to the value of the classes adopted by Owen, I may 
further remark, that recent investigations, of which he 
might have availed himself, have shown that the Cirri- 
pedia and his Epizoa are genuine Crustacea, and that the 
Entozoa can no longer be so widely separated from the 
Annellata as in his system. With reference to the other 
classes, I refer the reader to my criticism of older systems, 
and to the first section of this Chapter. 

It is a great satisfaction to me to find that the views I 
have advocated in the preceding sections, respecting the 
natural relations of the leading groups of the animal 
kingdom, coincide so closely with the classification of 
that distinguished zoologist, Milne-Edwards, lately pre- 
sented by him as the expression of his present views of 
the natural affinities of animals. He is the only original 
investigator who has recently given his unqualified ap- 
probation to the primary divisions first proposed by 



330 ESSAY ON CLASSIFICATION. 

Cuvier, admitting, of course, the rectifications among the 
groups of secondary rank, rendered necessary by the 
progress of science, to which he has himself so largely 
contributed. 

As to the classes adopted by Milne-Edwards, I have 
little to add to what I have already stated before with 
reference to other classifications. Though no longer 
overruling the idea of plan, that of complication of 
structure has still too much influence with Milne-Edwairds, 
inasmuch as it leads him to consider as classes, groups of 
animals which differ only in degree, and are therefore 
only orders. Such are, no doubt, his classes of MoUus- 
coids and those of Worms, besides the Myriapoda and 
Arachnids. Eespecting the Fishes, I refer to my re- 
marks in the first section (p. 298) of this Chapter, 

CLASSIFICATION OF MILNE-EDWABDS. 

The following diagram is drawn from the author's " Count 6Idmentairo 
d'Histoire naturelle'*; Paris, 1855, I toI. 12mo., 7th edit.; in which he has 
])resented the results of his latest inyestigations upon the classification of 
the Vertebrata and Articulata ; the minor sub-divisions of the Worms, Mol- 
lusks, and Zo5phjtes, however, are not considered in this work.i 

I. OSTEOZOABIA, OK YeBTBBBATA. 

Sub-branch. AUantoidians. Sub -branch. AnallatUo- 

idians. 

Class Batbachiaxs. 

Ord, Anura, Urodcla, Pc- 
Insectivora, Rodentia, Edentata, Carnivora, Am- I ., u- /^ -i- 

' ' \, . ^. .- rennibranchia, Cajciluc. 

phibia, Pachydermata, Ruminantia. b. Piscifor- q p l^ O - 

mia. Ord. Cetacea. 2°. Didelphja. Ord. Mar- 

supialia, Monotremata. 



Cl. Mammalia. 1**. Monodelphya. a. Pro- 
pria. Ord. Bimana, Quadrumana, Cheiroptera, 



Cl. Bibds. Ord. Rapaces, Passeres, Scanso- 
res, Gallinac, Grallro, and Palmipedes. 



sei. Ord. Acanthoptery- 
gii, Abdominalcs, Sub- 
brachii, Apodcs, Lopho- 
branchii, and Plectogua- 
thi. 2**. Chondropterygii. 
Cl. Reptiles. Ord. Chelonia, Sauria, Ophi- , Ord. Sturiones, Sclachii, 
dia. and Cyclostomi. 

* Consult, for these, his recent papers upou Polyps, Mollusks, and Crus- 
tacea, iu the Ann. des Sc. Nat. 



ANATOMICAL SYSTEMS. 



331 



II. EnTOMOZA, or A55ELLATA. 

Sub-branch. Arthropoda, 

Gl. Ixsbota. Ord, Goleoptera, Orthoptera, Neu- 
roptera, H jmenoptera, Lepidoptera, Hemiptera, Diptera, 
Rhipiptera, Anopleura, and Thjsanura. 

Ol. Mtbiapoda. Ord. Ohilognatha and Ghilopoda. 

Gl. AaAOHiriDS. Ord. Pulmonaria and Trachearia. 

Gl. Gbustacea. I^. Podophthalmia. Ord. Deca- 
poda and Stomopoda. %^. Edriophthalma. Ord. Amphi- 
poda, Lsemodipoda, and Isopoda. 3*^. Branchiopoda. 
Ord. Ostrapoda, Phjllopoda, and Trilobitse. 4°. £nto- 
mostraca. Ord. Gopepoda, Gladocera, Siphonostoma, 
Lemseida, Cirripedia. 5^. Xiphosura. 

III. MaLACOZOARIA, OB MOLLUSCA. 



Sub-branch. Ver- 

mes, 
Gl. Annelids. 
Gl. Helminths. 
Gl. Tubbellabia. 
Gl. Gestoidea. 
Gl. Rotatobia. 



Sub-branch. JfoUtuks proper, 
Gl. Gephalopods. 
Gl. Ptebopods. 
Gl. Gastebopods. 
Gl. Acephala. 



Sub-branch. MoUuscoids. 
Gl. Tunicata. 
Gl. Bbtozoa. 



Sub-branch. Radiariay or Radiata* 
Gl. Echinodebms. 
Gl. Aoalephs. 
Gl. Goballabia, or Polypi. 



IV. Zoophytes. 

Sub-branch. Sarcodaria. 
Gl. Infusobia. 
Gl. Sponqiabia. 



CLASSIFIGATION OF VON SIEBOLD AND STANNIUS. 

This classification is adopted in the following work : Siebold (G. Th. v.) 
and Stannius (H.), Lehrbnch der yergleichenden Anatomie ; Berlin, 1845, 
2 Tols. Svo. A second edition is now in press. 

EVERTEBRATA. 
I. Protozoa. 

Gl. I. IirpvsoRiA. Ord. Astoma and Somatoda. 

Gl. 2. Rhizopoda. Ord. Monosomatia and Polysomatia. 

II. ZOOPHYTA. 

Gl. 3. Polypi. Ord. Anthozoa and Biyozoa. 

Gl. 4. AoALEPHiB. Ord. Siphonophora, Discophora, Gtenophora. 

Gl. 5. EoHiNODEBMATA. Ord. Grinoidea, Asterioidea, Echinoidea, 

Holothurioidea, and Sipunculoidea. 
IIL Vebmss. 

Cu 6. H.LHIKTHB8. Ord. Cystici, . J^ 'r.^'r^M h^.:^ 

Gestodes, Trematodes, Acan- I duc«d most imporUnt improve- 

thocephali, Gordiacei, Nema- f "»•"'* *" ^^« oiasHiflcaUon of tb« 

^. '^ I Worms, aud greatly incroaMd our 

wfl^^ J kuowledgo of these animals. 



332 ESSAY ON CLASSIFICATION. 

Cl. 7. TuBBBLLABii. Ord. Rhabdocceli, DendrocoDli. 
Cl. 8. RoTATOBiL Not subdirided into orders. 
Ol. 9. AiTNULATi. Ord, Apodes and Ohsetopodes. 
lY. Mollusc A. 

Cl. 10. AoEPHALA. Ord, Tunicata, Brachiopoda, Lamellibranchia. 
Cl. 11. Cephalophoba, Meek (Gasteropoda). Ord. Pteropoda, He- 

teropoda, Gasteropoda. 
Cl. 12. Cephalopoda. Not subdivided into orders. 
V. Abthbopoda. 

Cl. 13. Cbustacea. Ord, Cirripedia, Siphonostoma, Lophyropoda, 

Phjilopoda, Poecilopoda, Lsomodipoda, Isopoda, Amphipoda, 

Stomapoda, Decapoda, Myriapoda. 
Cl. 14. Arachnida. Orders without names. 
Cl. 15. Insecta. a. Ametabola. Ord, Aptera. b, Hbmimbtabola. 

Ord, Hemiptera, Orthoptera. c, Holombtabola. Ord, 

Diptera, Lepidoptcra, Qjmenoptera, Stropsiptera, Neuro- 

ptera, and Coleoptera. 

VERTEBRATA. 
VI. Vebtebbata. 

Cl. 16. Pisces. Svh-dasses: 1st. Leptooabdii. 2nd. Mabsipo- 
BBANCHii. 3rd. Elasmobbanchii ; Ord. Holocephali, Pla- 
giostomi. 4th. Ganoibei; Ord, Chrondrostei, Holostei. 
5th. Teleostei ; Ord. Acanthoptori, Anacanthini, Pharyn- 
gognathi, Physostomi, Plectognathi, Lophobranchii. 6th. 
Dipnoi. 

Cl. 17. Reptilia. Subclasses: Ist. Dipnoa; Ord, Urodela, Ba- 
trachia, Gymnophiona. 2nd. Monopnoa : a, Streptosty- 
lica ; Ord, Ophidia, Sauria. b, Monimostylica ; Ord. Che- 

lonia, Crocodila. «. The snb-diviBions of the classes Pisces and R€p- 

I iilia are taken from the secoud edition, published in 

Cl 18 AvES ^ 1854-56, in which J. Muller's arrangement of the 

I Fishes is adopted; that of the lieptiles is partly StsD- 
! uius' own. The classes Aves and Mammalia, and 

Cl. 19. Mammalia. the ftrst volume of the second edition, are not yet ouL 

The most original feature of the classification of von 
Siebokl is the adoption of the types Protozoa and Vermes, 
in the sense in which they are limited here. The t}^e 
of Worms has growTi out of the investigations of the hel- 
minthologists, who, too exclusively engaged with the para- 
sitic Worms, have overlooked their relations to the other 
Articulata. On the other hand, the isolation in which 
most entomologists have reniiiined from the zoologists in 



ANATOMICAL SYSTEMS. 333 

general, has no doubt had its share in preventing an 
earUer thorough comparison of the Worms and the larval 
conditions of Insects, without which the identity of type 
of the Worms, Crustacea, and Insects can hardly be 
correctly appreciated Concerning the classes^ adopted 
by von Siebold and Stannius, I have nothing to remark 
that has not already been said. 

CLASSIFICATION OF R. LEUCKART. 

The classification of Leuckart is compiled from the following work : Ledck- 
ART (R.), Ueber die Morphologie und die Verwandtschaftsverhaltnissc dcr 
wirbellosen Thiere ; Braunschweig, 1848, 1 toI. 8vo. 

I. COBLSNTBRATA, Lkt. 

Cl. 1. PoLTPi. Ord, Anthozoa and Cjlicozoa (Lucemaria). 
Cl. 2. AcALEPHJB. Ord. Discophorse and Ctenophorce. 

II. ECHINODERMATA, Lkt. 

Cl. 3. Pelmatozoa, Lkt. Ord. Cjstidea and Crinoidea. 
Cl. 4. AoTiNOZOA, Latr. Ord. Echinida and Asterida. 
Cl. 5. SoTTODBRMATA, Brmst. Ord. Holothurin and Sipunclida. 
III. Vermes. 

Cl. 6. Anentbrati, Lkt. Ord, Cestodes and Acanthocephali. (Hel- 

minthes, Burm.) 
Cl. 7. Apodes, Lkt. Ord, Nemertini, Turbellarii, Trematodcs, and 

HirudineL (Trematodes, Burnt,) 
Cl. 8. CiLiATi, Lkt. Ord, Bryozoa and Rotiferi. 
Cl. 9. Ann ELIDES. Ord. Nematodes, Lumbricini, and Branchiati. 

(Annulati, Burm., excl. Nemertinis et Hirudineis.) 
lY. Arthropoda. 

Cl. 10. Ckustaoea. Ord, Entomostraca (Neusticopoda Car.) and 

Malacostraca. 
Cl. 1 1. Insect A. Ord. Myriapoda, Arachnida (Accra, Latr.) and 

Hexapoda. 
y. Mollusc A, Cut. (Palliata, Nitzsch.) 

cu 12. Tc»,c.,A. Ord. A8cidi« ^ jra:vi'Trc:;'i'r;^ :: 

(Tethyes Sav.) and SalpSO LaclasB.butevon as another gi-eatiype 
(Thalides Say.) I ofbrauch.interruediaiebetweeoKchi- 

J noderms and Worms. 

* The names of the types, Proto- various ways for nearly half a cen- 

zoa and Vermes, are older than their tury ; while that of Worms was first 

limitation in the classification of 8ie- adopted by Linnaeus, as a great divi- 

bold. That of Protozoa, first intro- sion of the animal kingdom, but in a 

duced by Qoldfuss, has been used in totally different sense. 



334 ESSAY ON CLASSIFICATION. 

Cl. 13. AcEPHALA. Ord, Lamellibranchiata (Cormopoda Niissch, 

Pelecypoda Oar.) and Brachiopoda. 
Ol. 14. Gasteropoda. Ord, Heterobranchia (Pteropoda, Infero- 

branchia, and Tectibranchia), Dermatobranchia (Gjmno- 

branchia and Phlebenterata), Heteropoda, Otenobranchia, 

Pulmonata, and Cyclobranchia. 
Cl. 15. Cephalopoda. 
VI. Vertbbbata. (Not considered.) 

I need not repeat here what I have ah-eady stated, in 
the first section, respecting the primary divisions adopted 
by Siebold and Leuckart. As to the classes, I may add 
that his three classes of Echinodcrms exhibit only ordinal 
characters. Besides Birds and Cephalopods, there is not 
another class so well defined, and so little susceptible of 
being subdivided into minor divisions presenting any- 
thing like class characters, as that of Echinoderms. Their 
systems of organs are so closely homological, (compare 
p. 293,) that the attempt here made by Leuckart, to sub- 
divide them into three classes, can readily be shown to 
rest only upon the admission, as classes, of groups which 
exhibit only ordinal characters, namely, difierent degrees 
of complication of structure. With reference to the 
classes of Worms, the same is equally true, as shown 
above. The arrangement of these animals proposed by 
Burmeister is certainly more correct than those of von 
Siebold and of Leuckiirt, inasmuch as he already rightly 
refei-s the Eotifera to the class of Crustacea, and does 
not, like Leuckart, associate the Bryozoa with the Worms. 
I agree, however, with Leuckart, respecting the propriety 
of removing the Nemertini and Hirudinei from among 
the true Annelides. Again, Burmeister appreciates also 
more correctly the position of the whole type of Worms, 
in referring them, with De BlainviUe, to the branch of 
Ailiculata. 

The common fault of all the anatomical classifications 



ANATOMICAL SYSTEMS. 335 

which have been proposed since Cuvier consists, firstly, in 
having given up, to a greater or less extent, the funda- 
mental idea of the plan of structure, so beautifully brought 
forward by Cuvier, and upon which he has insisted with 
increased confidence, and more and more distinct consci- 
ousness, ever since 1812; and, secondly, in having fre- 
quently allowed that of complication of structure to take 
the precedence over the more general features of plan, to 
correctly appreciate which requires, it is true, a deeper 
insight into the structure of the whole animal kingdom 
than is needed merely for the investigation of anatomical 
characters in single types. 

Yet, if we take a retrospective glance at these systems, 
and especially consider the most recent ones, it must be 
apparent to those who are conversant with the views now 
obtaining in our science, that, after a test of half a cen- 
tury, the idea of the existence of branches characterized 
by different plans of structure, as expressing the true rela- 
tions among animals, has prevailed over the idea of a 
graduated scale including all animals in one progressive 
series. When it is considered that this has taken place 
amidst the most conflicting views respecting Classifica- 
tion, and even in the absence of any ruling principle, it 
must be acknowledged that this can be only owing to the 
internal truth of the views first propounded by Cuvier. 
We recognize in the classifications of Siebold, Leuckart, 
and others, the triumph of the great conception of the 
French naturalist, even though their systems difier greatly 
fix>m his ; for the question, whether there are four or more 
great plans, limited in this or any other way, is not a 
question of principle, but one involving only accuracy and 
penetration iu the investigation; and I maintain that the 
first sketch of Cuvier, with all its imperfections of details, 



336 ESSAY ON CLASSIFICATION. 

presents a picture of the essential relations existing among 
animals more true to nature than the seemingly more cor- 
rect classifications of recent writers. 



SECTION V. 

PHTSIOFHILOSOPHICAL SYSTEMS. 

About the time that Cuvier and the French naturalists 
were tracing the structure of the animal kingdom, and 
attempting to erect a natural system of Zoology upon this 
foundation, there arose in Germany a school of philosophy, 
under the lead of Schelling, which extended its powerful 
influence to all the departments of physical science. Oken, 
Kieser, Bojanus, Spix, Buschke, and Cams, are the most 
eminent naturalists who applied the new philosophy to 
the study of Zoology. But no one identified his philoso- 
phical views so completely with his studies in natural 
history as Okcn. 

Now that the current is setting so strongly against 
everything which recalls the German physiophilosophers 
and their doings, and it has become fashionable to speak 
ill of them, it is an imperative duty for the impartial 
reviewer of the history of science to show how great and 
how beneficial the influence of Oken has been upon the 
progi*ess of science in general and of Zoology in particu- 
lar. It is, moreover, easier, wliUe borrowing his ideas, to 
sneer at his style and his nomenclature, than to discover 
the true meaning of what is left unexplained in his mostly 
paradoxical, sententious, or aphoristical expressions. But 
the man who has changed the whole method of illustrat- 
ing comparative Osteology; who has cai-efuUy investigated 
the embryology of the higher animals at a time wh(^n few 
physiologists were paying any attention to the subject; 



PHYSIOPHILOSOPHICAL SYSTEMS. 337 

who has classified the three kingdoms of nature upon 
principles wholly his own ; who has perceived thousands 
of homologies and analogies among organized beings 
entirely overlooked before ; who has published an exten- 
sive treatise of natural history, containing a condensed 
account of all that was known at the time of its publica- 
tion; who has conducted, for twenty-five years, the most 
extensive and most complete periodical review of the 
natural sciences ever published, in which every discovery 
made during a quarter of a century is faithfully recorded ; 
the man who inspired every student who knew him with 
an ardent love for science, and with admiration for his 
teacher, — ^that man will never be forgotten, nor can the 
services he has rendered to science be overlooked so long 
as thinking is connected with investigation^/ 

CLASSIFICATION OF OKEN. 

The foUowing diagram of Oken's classification is compiled from his All- 
gemeine Katurgeschichte flir alle St&nde ; Stuttgardt, 1833-1842, 14 vols. 
8to., Tol. 1, p. 5. The changes this system has undergone may be ascer- 
tained by comparing his Lehrbuch der Naturphilosophie ; Jena, 1809-1811, 
3 Tols. 8^0.; 2nd edit., Jena, 1831; 3rd edit., Zurich, 1843; Engl., Ray 
Society, London, 1847, 1 vol. Svo. — Lehrbuch der Katurgeschichte ; Leipzig, 
1813; Weimar, 1815 and 1825, Syo. — Handbuch der Naturgeschichte zum 
Gebrauch bei Yorlesungen; Numberg, 1816-1820, Svo. — Naturgeschichte 
tOa Schulen ; Leipzig, 1820, 1 vol. 8vo.; and various papers in the Isis. 

Ist Grade. Intestinal Animals ; also called j2?0(/y-animals and Tottch- 
animals. Only one cavity ; no head with a brain ; only the 
lowest sense perfect ; intestines and skin organs, but no flesh ; 
that is, no bones, muscles, or nervous marrow = InvertehrcUa, 
Characterized by the development of the vegetative systems 
of organs, which are those of digestion, circulation, and re- 
spiration. Hence — 

Cycle I. Digestive iimTTuz/^. = Radiata. Essential character: no deve- 
lopment beyond an intestine. 
Cl. 1. Infusoria (Stomach animals). Mouth with cilia only, to 
vibrate. 



338 ESSAY ON CLASSIFICATION. 

Cl. 2. PoLTPi (Intestine animalB). Mouth with lips and tentacles, 
to seize. 

Cl. 3. AcALEPHJB (Lacteal animals.) Body traversed by tubes simi- 
lar to the lymphatic vessels. 

Cycle II. Ctrctdative iln«ma^.= Mollusks. Essential character: intes- 
tine and vessels. 

Cl. 4. AoEPHALA (Biauriculate ammab). Membranous heart with 
two auricles. 

Cl. 5. Qasteropoda (Uniauriculate animals). Membranous heart 
with one auricle. 

Cl. 6. Cephalopoda (Bicardial animals). Two hearts. 

Cycle III. Jteipir(Uive AnimaU. == kiticulhitk. Essential character: in- 
testine, vessels, and spiracles. 

Cl. 7. WoBMB (Skin animals). Respire with the sldn itaeLf, or part 
of it ; no articulated feet. 

Cl. 8. Crustacea (Branchial animals). Gills or air tubes arising 
from the homy skin. 

Cl. 9. Insects (Tracheal animals). Trachess internally ; gills ex- 
ternally as wings. 

2nd Grade. Flesh Animals ; also called Head-asiimtAs = VertdnxUa. Two 
cavities of the body, surrounded by fleshy walls (bones and 
muscles) enclosing nervous marrow and intestines. Head with 
brain ; higher senses developed. Characterized by the deve- 
lopment of the animal systems, namely, the skeleton, the 
muscles, the nerves, and the senses. 

Cycle IV. Carnal Animals proper. Senses not perfected. 

Cl. 10. Fishes (^OTi^-animals). Skeleton predominating, very much 

broken up ; muscles white, brain without gyri, tongue without 

bone, noso not perforated, ear concealed, eyes without lids. 
Cl. 11. Reptiles (MuscU-VLmmtAs), Muscles red, brain without 

convolutions, nose perforated, ear without external orifice, eyes 

immovable, with imperfect lids. 
Cl. 12. Birds (^i^rr^-animals). Brain with convolutions, ears open, 

eyes immovable, lids imperfect. 

Cycle V. Semual Animals, All anatomical systems, and the senses per- 
fected. 
Cl. 13. Mammalia («%n««-animals). Tongue and nose fleshy, ears open, 
mostly witb a conch, eyes movable, with two distinct lids. 

The principles laid down by Oken, of which this classi- 
fication is the practical result for Zoology, may be summed 
up in the following manner : The grades or great types 



PHYSIOPHILOSOPHICAL SYSTEMS. 339 

of Animals are determined by their anatomical systems, 
such as the body and head; or the intestines, and the 
flesh and senses. Hence two grades in the animal king- 
dom. Animals are, as it were, the dismembered body of 
man made alive. The classes of animals are the special 
representation in living forms of the anatomical systems 
of the highest being in creation. 

Man is considered, in this system, not only as the key 
of the whole animal kingdom, but also as the standard 
measure of the organization of animals. There exists 
nothing in the animal kingdom which is not represented 
in higher combinations in Man. The existence of several 
distinct plans of structure among animals is virtually 
denied They are all built after the pattern of Man : the 
differences among them consist only in their exhibiting 
either one system only or a larger or smaller number of 
sysbemB of organs of higher or lower physiological import- 
ance, developed either singly or ki connexion with one 
another, ia their body. The principles of classification of 
both Cuvier and Ehrenberg are here entirely negatived. 
The principle of Cuvier, who admits four different plans 
of structure in the animal kingdom, is, indeed, incompati- 
ble with the idea that aU animals represent only the 
organs of Man. The principle of Ehrenberg, who con- 
siders all animals as equally perfect, is as completely 
irreconcileable with the assumption that all animals repre- 
sent an unequal sum of organs ; for, according to Oken, 
the body of animals is, as it were, the analyzed body of 
Man, the organs of which live singly, or in various com- 
biaations as independent animals. Each such combina- 
tion constitutes a distiact class. The principle upon which 
the orders are founded has already been explained above. 
(Chap. II, Sect, iii, p. 235.) 

z 2 



340 ESSAY ON CLASSIFICATION. 

There is something very taking in the idea that Man is 
the standard of appreciation of all animal structures. But 
all the attempts which have thus far been made to apply 
it to the animal kingdom as it exists must be considered 
as complete failures. In his different works, Okcn has 
successively identified the systems of organs of Man with 
different groups of animals; and different authors, who 
have adopted the same principle of classification, have 
identified them in different ways again. The impractica- 
bility of such a scheme must be obvious to any one who 
has satisfied himself practically of the existence of differ- 
ent plans of structure in the organization of animals. Yet 
the unsoundness of the general principle of the classifica- 
tions of the physiophilosophers should not render us blind 
to all that is valuable in their special writings. The 
works of Oken, in particular, teem with original sugges- 
tions respecting the natural afl&nities of animals ; and his 
thorough acquaintance with every investigation of his 
predecessors and contemporaries shows him to have been 
one of the most learned zoologists of this century. 

CLASSIFICATION OF FITZINGER. 

This diagram is extracted from Fitzinger's Systema Reptilium ; Vindo- 
bonsD, 1843, 1 vol. 8vo. 

I. Provincia. Evertebrata. 

Animalia sjstematum anatomicorum vegetativonim gradum evolutlonlfl 
exhibentia. 

A. Gradus eyolutionis sjstematum physiologiconim vegetativorum. 

I. Circulus. Oastrozoa. 

Evolutio sjstcmatis nutritionis. 

(7. Evolutio praevalcns b. Evolutio prscvaleus c. Evolutio praevaleDS 
systcinatis digestionis. systematis circulationis. systematis respiratioDis. 

Cl. 1. Infusoria. Cl. 2. Zooputta. Cl. 3. AcALErn^B. 



PHYSIOPHILOSOPHICAL SYSTEMS. 341 

II. Circulus. Phtsiozoa. 

Evolutio systematis generationis. 

Cl. 4. Ybrmes. Gl. 5, Radiata. Ol. 6. Annulata. 

B. Gradus eyolutionis sjstematum physiologicorum animalium. 

III. Circulus. Debmatozoa. 

Eyolutio systematis sensibilitatis. 
Cl. 7. AcEPHALA. Cl. 8. Cephalopoda. Cl. 9. Mollusoa. 

lY. Circulus. Arthbozoa. 

Evolutio systematis motus. 

Cl. 10. Cbustaoea. Cl. 11. Abacunoidba. Cl. 12. Ihbbota. 

II. Provincia. Yebtebbata. 

Animalia systematum anatomicorum animalium gradum evolutionis 
exhibentia. 

A. Qradus eyolutionis systematum physiologicorum vegetatlTorum. 

a. Eyolutio systematis nutritionis, simul- 

que ossium .... Cl. 13. Pibcbs. 

b. Evolutio systematis generationis, simul- 

que musculorum . . . Cl. 14. Reptilia. 

B. Gradus evolutionis systematum physiologicorum animalium. 

c. Evolutio systematis sensibilitatb, simul- 

que nervorum . . Cl. 15. Aveb. 

d. Evolutio systematis motus, simulque , 

sensuum .... Cl. 16. Mammalia. 

The fundamental idea of the classification of Fitzinger 
is the same as that upon which Oken has based his sys- 
tem. The higher divisions, called by him provinces, 
grades, and cycles, as well as the classes and orders, are 
considered as representing either some combination of 
different systems of organs, or some particular system of 
organs, or some special organ. His two highest groups 
(provinces) are the Evertebrata and Vertebrata. The 
Evertebrata represent the systems of the vegetative organs, 
and the Vertebrata those of the animal organs, as the Gut- 
animals and the Flesh-animals of Oken. Instead, how- 
ever, of adopting, like Oken, anatomical names for his 



342 ESSAY ON CLASSIFICATION. 

divisions, Fitzinger employs those most generally in use. 
His subdivisions or grades of these two primary groups 
are based upon a repetition of the same differences within 
their respective limits. The Invertebrata, in which the 
vegetative organs prevail, are contrasted with those in 
which the animal organs prevail; and the same distinc- 
tion is again drawn among the Vertebrata. Each of these 
embraxjes two circles, founded upon the development of 
one particular system of organs, etc. It cannot be ex- 
pected that the systems founded upon such principles 
should present a closer agreement with one another than 
those which are based upon anatomical differences; yet I 
would ask, what becomes of the principle itself, if its ad- 
vocates cannot even agree upon what anatomical systems 
of organs their classes are founded ? According to Oken, 
the MoUusks (Acephala, Gasteropoda, and Cephalopoda) 
represent the system of circulation ; at least, in the last 
edition of his system, he views them in that light, whilst 
Fitzinger considers them as representing the system of 
sensibility. Oken identifies the Articulata (Worms, Crus- 
tacea, and Insects) with the system of respiration; Fitz- 
inger with that of motion, with the exception of the 
Worms, including Radiata, which he parallelizes with the 
system of reproduction, etc. Such discrepancies must 
shake all confidence in these systems, though they should 
not prevent us from noticing the happy comparisons and 
suggestions to which the various attempts to classify the 
animal kingdom in this way have led their authors. It 
is almost superfluous to add, that, great as the disagree- 
ment is between the systems of different physiophiloso- 
phers, we find quite as striking discrepancies between the 
different editions of the system of the same author. 



PHYSIOPHILOSOPHICAL SYSTEMS. 



343 



The principle of the subdivision of (he classes among Invertebrata is here 
exemplified from the Radiata (Echinodermata). Each series contains three 
orders. 



1st Series. 

Evolutio prsQvalons 

sjstematis digestionis. 

ASTEBOIDSA. 

1. Encrinoidea. 

2. Comatulina. 

3. Asterina. 



2nd Series. 

Eyolutio prsBvalens 

sjstematis circulationis. 

EOHINODEA. 

1. Aprocta. 

2. Echinina. 

3. Spatangoidea. 



3rd Series. 

Evolutio prsQvalens 

sjstematis respirationis. 

SOTTODEBMATA. (IIolo- 

thurioids). 

1. Sjnaptoidea. 

2. Holothurioidea. 

3. Pentactoidea. 



In Vertebrata each class has five series, and each series throe orders ; so 
in Mammalia, for example : 



1st Series. 

Evolutio prsQvalens 

sensus tactus. 

Oetaoba. 

1. Balanodea. 

2. Delphinodea. 

3. Sircnia. 



2nd Series 

Evolutio praavalens 

sensus gustus. 

Paohtdermata. 

1. Phocina. 

2. Obesa. 

3. Buminantia. 



3rd Series. 

Evolutio prsQvalens 

sensus olfactus. 

Edentata. 

1. Monotremata. 

2. Lipodonta. 

3. Tardigrada. 



4th Series. 

Evolutio prsBvalens 

sensus auditus. 

Unquiculata. 

1. Glires. 

2. Bruta. 

3. Ferse. 



5th Series. 

Evolutio prsDvalens 

sensus visus. 

Primates. 

1. ChiropterL 

2. Hemipitheci. 

3. Anthropomorphi. 



Instead of considering the orders as founded upon a 
repetition of the characters of higher groups, as Oken 
would have it, Fitzinger adopts series as founded upon 
that idea, and subdivides them further into orders as 
above. These series, however, have still less reference to 
the systems of organs which they are said to represent, 
than either the classes or the higher divisions of the ani- 
mal kingdom. In these attempts to arrange minor groups 
of animals into natural series, no one can fail to perceive 
an eflFort to adapt the frames of our systems to the impres- 
sion we receive from a careful examination of the natural 



344 ESSAY ON CLASSIFICATION. 

relations of organized beings. Everywhere we notice sach 
series; sometimes extending only over groups of spedea* 
at other times embracing many genera, entire families.- 
nay, extending frequently to several families. Even the 
classes of the same branch may exhibit, more or less dis- 
tinctly, such a serial gradation. But I have failed, thus 
far, to discover the principle to which such relations may 
be referred, as far as they do not rest upon complication 
of structure,^ or upon the degree of superiority or inferi- 
ority of the features upon which the different kinds of 
groups are themselves founded. Analogy plays also into 
the series ; but before the categories of analogy have been 
as carefully scrutinized as those of affinity, it is impossible 
to say within what limits this takes place. 



CLASSIFICATION OF m'lEAY. 



The great merit of the system of M'Leay^ — and in my 
opinion it has no other claim to our consideration — con- 
sists in having called prominently the attention of natu- 
ralists to the difference between two kinds of relationship 
almost universally confounded before, — affinity and ana- 
logy. Analogy is shown to consist in the repetition of 
similar features in groups otherwise remote, as far as their 
anatomical characters are concerned, whilst affinity is 
based upon similarity in the structural relations. On 
account of the similarity of their locomotion. Bats, for 
instance, may be considered as analogous to Birds ; Whales 
are analogous to Fishes on account of the similarity of 
their form and their aquatic mode of life; whilst both 

^ Compare Chap. II, Sect. 3, p. 233. of the German physiophilosophers, 

' 1 have intro'liiced the olassifioa- but on a<*co\int of its i^eneral charac- 

tion of ArLeay into this section, not ter, and because it is based upon an 

because of any resemblance to those ideal view of the affinities of animals. 



PHYSIOPHILOSOPHICAL SYSTEMS. 345 

Bats and Whales are allied to one another and to other 
Mammalia on account of the identity of the most charac- 
teristic features of their structure. This important dis- 
tinction cannot fail to lead to interesting results. Thus 
far, however, it has only produced fanciful comparisons 
from those who first traced it out. It is assumed, for in- 
stance, by M'Leay, that all animals of one group must be 
analogous to those of every other group, besides forming 
a circle in themselves ; and in order to carry out this idea 
all animals are arranged in circular groups, in such a 
manner as to bring out these analogies, whilst the most 
obvious afl^ties are set aside to favour a preconceived 
view. But, that I may not appear to underrate the merits 
of this system, I will present it in the very words of its 
most zealous admirer and self-complacent expounder, the 
learned William Swainson.^ 

"The *Hor8B Entomologicfie,'^ unluckily for students, 
can only be thoroughly understood by the adept, since the 
results and observations are explained in different parts; 
the style is somewhat desultory, and the groups, for the 
most part, are rather indicated than defined. The whole, 
in short, is what it professes to be, — more a rough sketch 
of the leading peculuirities of the great divisions of ani- 
mals, and the manner in which they are probably con- 
nected, than an accurate determination of the groups 
themselves, or a demonstration of their real afl&nities. 
More than this, perhaps, could not have been expected, 
considering the then state of science, and the Herculean 
difficulties which the author had to surmount. The work 
in question haa now become exceedingly scarce ; and this 

1 SwAiNSOX (W.), A Treatise of the " M'Leay (W. S.), Horo) Entomo- 

Qeography and Classification of Ani- logicic ; or Essays on the Annulose 

Dials; London, 1835, 1 vol. 12mo.; Animals; London, 181D-21, 2 vols., 

p. 201 205. 8vo. 



346 ESSAY ON CLASSIFICATION. 

will be an additional reason with us for communicating 
occasional extracts from it to the reader. Mr. M'Leay's 
theory wlQ be best understood by consulting his diagram; 
for he has not, as we have already remarked, defined any 
of the vertebrated groupa Condensing, however, the 
result of his remarks, we shall state them as resolvable 
into the following propositions: 1, that the natural series 
of animalft is coutinuous, forming, as it were, a circle, so 
that upon commencing at any one given point, and thence 
tracing all the modifications of structure, we shall be im- 
perceptibly led, after passing through numerous forms, 
again to the point from which we started; 2, that no 
groups are natural which do not exhibit such a circular 
series; 3, that the primary divisions of every large group 
are ten, five of which are composed of comparatively large 
circles, and five of smaller, — ^these latter being termed 
osculant, and being intermediate between the former, 
which they serve to connect; 4, that there is a tendency, 
in such groups as arc placed at the opposite points of a 
circle of affinity, * to meet each other ; 5, that one of the 
five larger groups into which every natural circle is divided, 
* bears a resemblance to all the rest, — or, more strictly 
speaking, consists of types which represent those of each 
of the four other groups, together with a type peculiar to 
itself/ These are the chief and leading principles which 
Mr. M'Leay considers as belonging to the natural system. 
We shall now copy his diagram, or table of the animal 
kingdom, and then endeavour, with this help, to explain 
the system more in detail." 



PHYSIOPHILOSOPHICAL SYSTEMS. 



34: 




OS 



** We must, in the first instance, look to the above tabu- 
lar disposition of all animals, as forming themselves col- 
lectively into one great circle, which circle touches or 
blends into another, composed of plants, by means of the 
* least organized beings of the vegetable kingdom'. Next 
we are to look to the larger component parts of this great 
circular assemblage. We find it, in accordance with the 
tiiird proposition, to exhibit five great circles composed of 
the MoLLUSCA, or shell-fish ; Acrita, or polyps : Radiata, 
or star-fish; AyxuLOSA, or insects; and Vertebrata, or 
vertebrated animals ; each passing or blending into each 
other by means of five other groups of animals, much 
smaller, indeed, in their extent^ but forming so many con* 



348 ESSAY ON CLASSIFICATION. 

necting or osculant circles.-^ The number, therefore, as 
many erroneously suppose, is not five, but ten. This is 
quite obvious ; and our opinion on this point is confinned 
by the author himself in the following passage, when 
alluding to his remarks upon the whole : * The foregoing 
observations, I am well aware, are far from accurate, but 
they are sufl&cient to prove that there are five great circu- 
lar groups in the animal kingdom, each of which possesses 
a peculiar structure ; and that these, when connected by 
means of five smaller osculant groups, compose the whole 
province of Zoology/ Now these smaller osculant groups 
are to be viewed as circles; for, as it is elsewhere stated, 
* every natural group is a circle more or less complete.' 
This, in fact, is the third general principle of Mr. M'Leay s 
system ; and he has exemplified his meaning of a natural 
group in the above diagram, where all animals are arranged 
imder five large groups or circles, and five smaller ones. 
Let us take one of these groups, the Vertebrata. Does 
that form a circle of itself ? Yes ; because it is intimated 
that the Reptiles {Kept ilia) pass into the Birds {Aves); 
these, again, into the Quadrupeds {Mammalia) ; Quadru- 
peds unite with the Fishes (Pisces); these latter \\dth the 
amphibious Reptiles ; and the Frogs bring us back again 
to the Reptiles, the point from whence we started Thus 
the series of the vertebrated group is marked out, and 
shown to be circular ; therefore it is a natural group. This 
is an instance where the circular series can be traced. 
We now turn to one where the series is imperfect, but 
where there is a decided tendency to a circle. This is the 
MoUusca. Upon this group our author says : ' I have by 
no means determined the circular disposition to hold good 

* In the original diagram, as in merely indicated by the names ar- 
that above, these five smaller circles ranged like rays between the five 
are not represented graphically, but large circles. 



PHYSIOPHILOSOPHICAL SYSTEMS. 349 

among the MoUusca; still, as it is equally certain that 
this group of animals is as yet the least known, it may be 
improper at present to conclude that it forms any excep- 
tion to the rule : it would even seem unquestionable that 
the Gasteropoda of Cuvier return into themselves, so as 
to form a circular group ; but whether the Acephala form 
one or two such, is by no means accurately ascertaiaed, 
though enough is known of the MoUusca to incline us to 
suspect that they are no less subjected, in general, to a 
circular disposition than the four other great groups/ 
This, therefore, our author considers as one of those groups 
which, without actually forming a circle, yet evinces a 
disposition to do so ; and it is therefore presumed to be a 
natural group. But, to illustrate this principle farther, let 
us return to the circle of Vertcbrata. This, as we see by 
the diagram, contains five minor groups or circles, each of 
which is again resolvable into five others regulated pre- 
cisely in the same way. The class Aves, for example, is 
first divided into rapacious birds (Raptores), perching 
birds {Inse8Sores)y gallinaceous birds {Rasores), wading 
birds {GraUatores), and swimming birds {Natatores) ; and 
the proof of this class being a natural group is in all these 
divisions blending into each other at their confines and 
forming a circle. In this manner we proceed, beginning 
with the higher groups and descending to the lower, until 
at length we descend to genera properly so called, and 
reach at last the species; every group, whether large or 
small, forming a circle of its own. Thus there are circles 
within circles, * wheels within wheels' — ^an infinite nimiber 
of complicated relations ; but all regulated by one simple 
and uniform principle, — that is, the circularity of every 
group." 

The writer who can see that the Quadrupeds imite with 



350 ESSAY ON CLASSIFICATION. 

the Fishes, and the like, and yet says that Cuvier **wa« 
totally unacquainted with the very first principles of the 
natural system,'' hardly deserves to be studied in our 
days. 

The attempt at representing graphically the compli- 
cated relations which exist among animals has, however, 
had one good result, — ^it has checked, more and more, the 
confidence in the uniserial arrangement of animals, and 
led to the construction of many valuable maps exhibiting 
the multifarious relations which natural groups, of any 
rank, bear to one another. 

SECTION VI. 

EMB&TOLOOICAL SYSTEMS. 

Embryology, in the form it has assumed within the last 
fifty years, is as completely a German science as the 
" Naturphilosophie." It awoke to this new activity con- 
temporaneously with the development of the Philosophy 
of Nature. It would hardly be possible to recognize the 
leading spirit in tliis new development, from his published 
works; but the man whom Pander and K. E. von Baer 
acknowledge as their master must be considered as the 
soul of this movement, and this man is Ignatius DoUinger. 
It is with deep gratitude I remember, for my own part^ the 
influence which that learned and benevolent man had upon 
my studies and early scientific application during the four 
years I spent in his house, in Munich, from 1827 to 1831. 
To him I am indebted for an acquaintance with what was 
then known of the development of animals prior to the 
publication of the great work of Baer; and from his lec- 
tures I fii'st learned to appreciate the importance of Em- 
bryology to Physiology and Zoology. The investigations 



PHYSIOPHILOSOPHICAL SYSTEMS. 351 

of Pander^ upon the development of the chicken in the 
egg, which have opened the series of those truly original 
researches in Embryology of which Germany may justly 
be proud, were made imder the direction and with the 
cooperation of Dollinger, and were soon followed by the 
more extensive works of Rathke and Baer, whom the civi- 
lized world acknowledges as the founders of modem Em- 
bryology. 

The principles of classification propounded by K R von 
Baer seem never to have been noticed by systematic 
writers ; and yet they not only deserve the most careful 
consideration, but it may fairly be said that no naturalist, 
besides Cuvier, has exhibited so deep an insight into the 
true character of a natural system, supported by such an 
extensive acquaintance with the subject, as this great 
embryologist has in his " Scholien und Corallarien zu der 
Entwickelungsgeschichte des Hiihnchens in Eie."^ These 
principles are presented in the form of general proportions 
rather than in the shape of a diagram with definite syste- 
matic names ; and this may explain the neglect which it 
has experienced on the part of those who are better satis- 
fied with words than with thoughts. A few abstracts, 
however, may show how richly the perusal of his work is 
likely to reward the reader. 

The results at which K. E. von Baer had arrived by his 
embryological investigations, respecting the fundamental 
relations existing among animals, differed considerably 
from the ideas then prevailing. In order, therefore, to be 
correctly understood, he begins, with his accustomed ac- 

^ Paudki, Beitrage zur Entwicke- flexion von Dr. Karl Ernst von Baer; 

lungsgeschichte des Huhnchens im Kdnigsberg, 1828,4to. — See also Acta 

Eie; Wurzbarg, 1817, 1 yoI. fol. Nova Acad. Leop. Ceesar, vol. 13, and 

' Ueber Entwickelungsgeschichte MeckePs Arch., 1826. 
der Thiere, Beobachtong iind Re- 



352 ESSAY ON CLASSIFICATION. 

curacy and clearness, to present a condensed account of 
those opinions with which he disagreed, in these words: 

"Few views of the relations existing in the organic 
world have received so much approbation as this: that 
the higher animal forms, in the several stages of the deve- 
lopment of the individual, from the beginning of its exist- 
ence to its complete formation, correspond to the perma- 
nent forms in the animal series, and that the development 
of the several animals follows the same laws as those of 
the entire animal series; that consequently the more 
highly organized animal, in its individual development, 
passes, in all that is essential, through the stages that are 
permanent below it, so that the periodical differences of 
the individual may be reduced to the differences of the 
permanent animal forms." 

Next, in order to have some standard of comparison 
with his embryological results, he discusses the relative 
position of the different permanent t}'pes of Rnim filsi as 
follows : 

" It is especLally important that we should distinguish 
between the degree of perfection in the animal structure 
and the type of organization. The degree of perfection 
of the animal structure consists in the greater or less 
heterogeneousness of the elementary parts, and the sepa- 
rate di\4sions of a complicated apparatus, — in one word, 
in the greater histological and morphological differentia- 
tion. The more uniform the whole mass of the body Ls 
the lower the degree of perfection : it is a stage higher 
when nerve and muscle, blood and cellular tissue, are 
sharply distinguished. In proportion to the difference 
between these parts is the development of the animal life 
in its different tendencies ; or, to express it more accu- 
rately, the more the animal life is developed in its several 



PHYSIOPHILOSOPHICAL SYSTEMS. 353 

tendencies, the more heterogeneous are the elementary 
parts which this life brings into action. The same is true 
of the single parts of any apparatus. That organization 
is higher in which the separate parts of an entire system 
differ more among themselves, and each part has greater 
individuality, than that in which the whole is more uni- 
form. I call type the relations of organic elements and 
organs, as far as their position is concerned. This relation 
of position is the expression of certain fimdamental con- 
nexions in the tendency of the individual relations of life ; 
as, for instance, of the receiving and discharging poles of 
the body. The tjrpe is altogether distinct from the de- 
gree of perfection; so that the same type may include 
many degrees of perfection, and, vice versa, the same de- 
gree of perfection may be reached in several types. The 
degree of perfection, combined with the tjrpe, first deter- 
mines those great animal groups which have been called 
classes.^ The confounding of the degree of perfection 
with the tjrpe of organization seems the cause of much 
mistaken classification; and in the evident distinction 
between these two relatious we have sufficient proof that 
the different animal forms do not present one imiserial 
development from the Monad up to Man.'' 

The tjrpes he has recognized are : 

I. The Per{j)henc Tijpe, The essential contrasts in 
this tjrpe are between the centre and the periphery.^ The 

* From this statement it is plain complication of structure as deter- 
that Baer has a very definite idea of mining the relative rank of the orders, 
the plan of structure, and that he and the different ways in which, and 
has reached it by a very different the different means by which, the 
road from that of Cuvier. It is clear plans are executed, as characteristic 
also that he understands the distinc- of the classes. 

tlon between a plan and its execu- ' Without translating verbatim 

tion. But his ideas respecting the the descriptions Baer gives of his 

different features of structure are not types, which are greatly abridged 

quite so precise. He does not dis- here, they are reproducea as nearly 

tmguish, for instance^ between the as possible in his own words. 

AA 



354 ESSAY ON CLASSIFICATION. 

oiganic fimctioDB of life are carried on in antagonistic 
relations, firom the centre to the circumference. Corre- 
sponding to this, the whole organization radiates around 
a common centre. There exists, besides, only the contrast 
between above and below, but in a weaker degree ; that 
between right and left, or before and behind, is not at all 
noticeable, and the motion is therefore undetermined in 
its direction. As the whole organization radiates firom 
one focus, so are the centres of all the organic systems 
arranged, ring-like, around it; as, for instance, the sto- 
mach, the nerves and the vessels (if these parts are deve- 
loped), and the branches extending from them into the 
rays. What we find in one ray is repeated in every other, 
the radiation being always firom the centre outwards, and 
every ray beaxing the same relation to it. 

II. The Lo7igitudinal Type, as observed in the Vibrio, 
the Filaria, the Gordius, the Nais, and throughout the 
whole series of articulated animals. The contrast between 
the receiving and the discharging organs, which are placed 
at the two ends of the body, controls the whole organiza- 
tion. The mouth and the anus are always at opposite 
ends, and usually also the sexual organs, though their 
opening is sometimes farther forward: this occurs, how- 
ever, more frequently in the females, in which these organs 
have a double function, than in the males. When both 
sexual organs are removed from the posterior extremity, 
the opening in the female usually lies farther forward thim 
in the male. So is it in the Myriapods and the Crabs. 
The Leeches and Earthworms present a rare exception. 
The receptive pole being thus definitely fixed, the organs 
of senses, as instrumental to the reception of the ner- 
vous system, early reach an important degree of perfec- 
tion. The intestinal canal, as well as the vascular stems 



4 



EMBRTOLOOICAL SYSTEMS. 355 

and the nervous system, extends through the whole length 
of the body, and all organic motion in these animals has 
the same prevailing direction. Only subordinate branches 
of these organs arise laterally, and chiefly wherever the 
general contrast, manifested in the whole length, is re- 
peated in such a manner, that, for each separate segment, 
the same contrast arises anew in connexion with the essen- 
tial elements of the whole organism. Hence the tendency 
in these animds to divide into maay segments, in the 
direction of the longitudinal axis of the body. In the 
true Insects undergoing metamorphosis, these segments 
unite again into three principal regions, in the first of 
which the life of the nerves prevails; in the second, mo- 
tion ; in the third, digestion ; though neither of the three 
regions is whoUy deprived of any one of these functions. 
Besides the opposition between before and behind, a less 
marked contrast is observed in a higher stage of develop- 
ment between above and below, A diflFerence between 
•right and left forms a rare exception, and is generally 
wanting. Sensibility and irritability axe particularly de- 
veloped in this series. Motion is active, and directed 
more decidedly forward in proportion as the longitudinal 
axis prevails. When the body is contracted, as in spiders 
and crabs, its direction is less decided. The plastic organs 
are little developed; glands, especially, are rare, and 
mostly replaced by simple tubes. 

III. The Massive Type. We may thus call the type 
of MoUusks, for neither length nor surface prevails in 
them; but the whole body and its separate parts are 
formed rather in round masses, which may be either hol- 
low or solid. As the chief contrast of their structure is 
not between the opposite ends of the body, nor between 
the centre and periphery, there is almost throughout this 

AA 2 



356 ESSAY ON CLASSIFICATION. 

type an absence of Bymmetty. Generally the discharging 
pole is to the right of the receptive one. The discharging 
pole, however, is either near the receptive one, or removed 
from it, and approximated to the posterior extremity of 
the body. As the tract of the digestive apparatus is 
always determined by these two poles, it is more or less 
arched ; in its simplest form it is only a single arch, as in 
PlumateUa. When that canal is long, it is curled up in 
a spiral in the centre, and the spiral probably has its defi- 
nite laws. For instance, the anterior part of the alimen- 
tary canal appears to be always placed under the poste- 
rior. The principal currents of blood are also in arches, 
which do not coincide with the medial line of the body. 
The nervous system consists of diffused ganglia, united 
by threads, the larger ones being around the oesophf^s. 
The nervous system and the organs of sense appear late; 
the motions are slow and powerless. 

IV. Tlie Vertebrate Type, This is, as it were, composed 
of the preceding typos, as we distinguish an animtU and a« 
vegetative system of the body, which, though influencing 
one another in theii' development, have shigly a peculiiu* 
ty[ncal organization. In the animal system the ailieula- 
tion reminds us of the second type, and the discharging 
and receiving organs are also placed at opposite taids. 
There is, however, a marked difference betw<:'en the Arti- 
culates and the \ ertebrates, for the animal system of the 
\'ertel)rates is not only doubled along the two sides, but 
at the same time upwards and downwards, in such a way 
that the two lateral walls which unite below circumserilH.^ 
the vegetative system, while the two tending upward sur- 
round a eentral ort^^an of the animal life, -the brain and 
spinal marrow, which are wanting in Invertebrates. The 
solid frame represents this type most completely, as fixjm 



EMBRYOLOGICAL SYSTEMS. 357 

its medial axis, the backbone, there arise upward, arches 
which close in an upper crest; and do^^^lward, arches 
which unite, more or less, in a lower crest. Corresponding 
to this we see four rows of nei-vous threads along the 
spinal marrow, which itself contains foiu' strings, and a 
quadripartite gray mass. The muscles of the trunk foim 
also four principal masses, which are particularly distinct 
in the Fishes. The animal system is therefore doubly 
symmetrical in its arrangement. It might easily be shown 
how the vegetative systems of the body correspond to the 
type of Mollusks, though influenced by the animal system. 

From the iQustrations accompanying this discussion of 
the great types or branches of the animal kingdom, and 
still more from the paper published by K. E. von Baer in 
the " Nova Acta,"^ it is evident that he perceived more 
clearly and earlier than any other naturalist the true rela- 
tions of the lowest animals to their respective branches. 
He includes neither Bryozoa nor Intestinal Worms among 
Radiata, as Cuvier, and after him so many modem writers, 
did, but correctly refers the former to the Mollusks, and 
the latter to the Articulates. 

Comparing these four tj^es with the embryonic deve- 
lopment, von Baer shows that there is only a general 
similarity between the lower animals and the embryonic 
stages of the higher ones, arising mainly from the absence 
of differentiation in the body, and not from a typical 
resemblance. The embryo does not pass from one type 
to the other; on the contrary, the type of each animal is 

* Bcitrago zur Kenntniss der nie- animals. These " Beitriige" and the 

dem Thiere, NoTa Acta AcademiaB papers in which Cuvier characterized 

NatursQ Curiosum, toI. 13, Part 2, for the first time the four great types 

1827, containing seven papers, upon of the animal kingdom, are among 

Aspidogaster, Distoma, and others, the most important contributions to 

Cercaria, Nitzschia, Poly stoma, Pla- general Zoology ever published. 
naria, and the general affinities of all 



358 ESSAY ON CLASSIFICATIOK. 

defined from the beginning, and controls the whole deve- 
lopment. The embryo of the Vertebrate is a Vertebrate 
from the beginning, and does not exhibit at any time a 
correspondence with the Invertebrates. The embryos of 
Vertebrates do not pass, in their development, through 
other permanent types of animals. The fundamental type 
is first developed, and afterwards more and more subordi- 
nate characters appear. From a more general type the 
more special is manifested; and the more two forms of 
animals differ, the earlier must their development be traced 
back to discern an agreement between them. It is barely 
possible that, in their first beginning, all animals are alike, 
and present only hoUow spheres ; but the individual de- 
velopment of the higher animals certainly does not pass 
through the permanent forms of lower ones. What is 
common in a higher group of animals is always sooner 
developed in their embryos than what is special : out of 
that which is most general arises that which is less gene- 
ral, until that which is most special appears. Each em- 
bryo of a given type of animals, instead of passing through 
other definite types, becomes, cih the contrary, more and 
more unlike them. An embryo of a higher type is there- 
fore never identical with another animal tjrpe, but only 
with an embryo. 

Thus far do the statements of von Baer extend.^ It is 

^ The account which Huxley gives protests against an identification of 

of Bacr's yiews (see Baden Powell's his views with those of Ouvier. (Ba- 

Essajs, Appendix 7, p. 495) is incor- er's Entwick. p. 7.) Nor has Baer 

rect. Baer did not ^' demonstrate demonstrated the ^^ doctrine of the 

that the classification of Cuvicr was, unity of organization of all animals," 

in the main, simply the expression and placed it *^upon a 'footing as 

of the fact, that there are certain secure as the law of gravitation/* 

common phnis of development in the and arrived at " the grandest law," 

animal kingdom," etc.; for Cuvicr that, up to a certain point, the deve- 

recognized these plans in the struc- loument ^^ followed a plan common to 

ture of the animals before Baer traced aU animals.^^ On the contrary, Baer 

their development ; and Baer himself admits four distinct types of animab, 



EMBRYOLOOICAL SYSTEMS. 



359 



evident from this that he has clearly perceived the limita- 
tion of the different modes of embryonic development 
within the respective branches of the animal kingdom; 
but it is equally certain that his assertions are too general 
to furnish a key for the comparison of the successive 
changes which the different types undergo within their 
respective limits, and that he is still vaguely under the 
impression that the development corresponds, in its indi- 
vidualization, to the degrees of compUcation of structure. 
This could hardly be otherwise as long as the different 
categories of the structure of animals had not been clearly 
distinguished.^ 



CLASSIFICATION OF K. E. VON BAEK. 

In confonnity with his embrjological investigations, K. £. von Baer pro- 
poses the following classification : 

I. Peripheric Type. (Radiata.) Evolutio radiata. The development 
proceeds from a centre, producing identical parts in a radiating 
order. 

II. Massive Type. (Mollusc a.) Evolutio contorta. The development 
produces identical parts curved around a conical or other space. 

III. Longitudinal Type. (Artioulata.) EvoliUio gemina. The develop- 
ment produces identical parts arising on both sides of an axis, 
and closing up along a line opposite the axis. 



and four modes of development. He 
only adds: "It is barely possible, 
that, in their first beginning, all ani- 
mals are alike.'* Huxley must also 
have overlooked Cuvier's introduc- 
tion to the "lUgne Animal" (2nd 
edit., vol. 1, p. 48, quoted verbatim 
above, p. 309), when he stated that 
Cuvier '^ did not attempt to discover 
upon what plans animals are con- 
structed, but to ascertain in what 
manner the facts of animal organiza- 
tions could be thrown into the fewest 
possible propositions." On the con- 



trary, Cuvier's special object for 
many years was to point out these 
plans, and to show that they are 
characterized by peculiar struc- 
tures ; while Baer*s merit consists in 
having discovered four modes of de- 
velopment, which coincide witn the 
branches of the animal kingdom, in 
which Cuvier recognized four differ- 
ent plans of structure, Huxley is 
equally mistaken when he says that 
Cuvier adopted the nervous system 
"as the base of his great divisions." 
1 Compare Chap. II, Sect. I to 9. 



360 ESSAY ON CLASSIFICATION. 

y. Doublj Symmetrical type. (Ybbtebbata.) Evolutio Hgemina. The 
dcYelopment produces identical parts arising on both sides of an 
axis, gr(ming upwards and downwards, and shutting up along 
two lines, so that the inner layer of the germ is inclosed below, 
and the upper layer above. The embryos of these animals have 
a dorsal cord, dorsal plates, and ventral plates, a nervous tube 
and branchial fissures. 
1**. They acquire branchial fringes; 

a. But no genuine lungs are developed. 

a. The skeletdh is not ossified. Oartilaqinous Fishes. 
3. The skeleton is ossified. Fishes Propee. 

b. Lungs are formed. Amphibia. 

a. The branchial fringes remain. Sirens. 
3. The branchial fringes disappear. Urodel\ and Axuka. 
2°. They acquire an allantois, but 
a. Have no umbilical cord ; 

a. Nor wings and air sacs. Reptiles. 
3. But wings and air sacs. Birds. 
h. Have an umbilical cord. Mammalia. 
a. Which disappears early ; 

1^. Without connection with the mother. Monotremata. 
2^. After a short connection with the mother. Marsd- 

PIALIA. 

3. Which is longer persistent ; 

1°, The yolk sac continues to grow for a long time. 
The allantois grows little. Rodentia. 
The allantois grows moderately. Inbectivora. 
The allantois grows much. Oarnivora. 
2°. The yolk sac increases slightly. 

The allantois grows little. Umbilical cord very long. 

Monkeys and Man. 
The allantois continues to grow for a long time. Pla- 
centa in simple masses. Ruminants. 
The allantois continues to grow for a long time. Pla- 
centa spreading. Pachyderms and Cetacea. 



CLASSIFICATION OF VAN BENEDEN. 

Van Bencden has also proposed a classification based upon Embryology, 
which was first sketched in his paper upon the Embryology of the Bryozoa: 
Recherches sur Tanatomie, la physiologic, et Tembryogenie des Bryozoaircs; 
Bnixelles, 1845, 4to. ; and afterwards extended in his Comparative Ana- 
tomy : Anatomic comparoe (BruxoUcs, without date, but probably of the 
year 1855), 1 vol. 12mo. 



m 



EMBRYOLOGTCAL SYSTEMS. 361 

I. IIypocotylbdonks, or IlTpoyiTELLiANS. (Vcrtebrata.) The vitellus 
enters the body from the ventral side. 

Cl. 1. Mammalia. (Primates, Cheiroptera, Inscctivora, Rodeutia, 

Oamivora, Edentata, Proboscidea, Ungulata, Siicnoidea, Ce- 

tacea.) 
Ol. 2. BiBPS. (PsittacesES, Rapaces, Passcres, Columbas, Gallinas, Stru- 

thiones, Qralla;, Palmipedes.) 
Cl. 3. Reptiles. (Crocodili, Chelonii, Ophidii, Saurii, Pterodactyli, 

Simosauri, Plesiosauri, Ichthyosauri.) 
Cl. 4. Batbachians. (Labyriuthodontes, Peromelia, Anura, Urodcla, 

Lepidosirenia.) 
Cl. 5. Fishes. (Plagiostomi, Qanoidei, Telcostei, Cyclostomi, Lepto- 

cardii.) 

II. Epicottledones, or Epivitellians. (Articulata.) The vitellus enters 

the body from the dorsal side. 
Cl. 6. Insects. (Coleoptera, Neuroptera, Stropsiptera, Ilymenoptera 

Lepidoptera, Diptera, Orthoptera, Hemiptera, Thysanura, Pa- 

rasita.) 
Cl. 7. Mybiapodes. (Diplopoda, Chilopoda.) 
Cl. 8. Abaohnides. (Scorpiones, AranesD, Acari, Tardigrada.) 
Cl. 9. Cbustacea. (Decapoda, Stomapoda, Amphipoda, Isopoda, Lao- 

modipoda, Phyllopoda, Lophyropoda, Xiphosura, Siphono- 

stoma, Myzostoma, and Cirripedia.) 

III. Allocotyledo5£S ot Alloyitellians. (Mollusco-Radiaria.) The vi- 
tellus enters the body neither from the ventral nor from the 
dorsal side. 

Cl. 10. MoLLUscA. Including Cephalopoda, Gasteropoda, Poecilopoda, 
and Brachiopoda. (Acephala, Tunicata, and Bryozoa.) 

Cl. 11. WoBMS. (Malacopoda, Annelides, Siponculides, Nemertini, 
Nematodes, Acanthocephali, Scoleides, Hirudinei, Trematodes 
Cestodes, Rotiferi, Planaria;.) 

Cl. 12. Eohinodebms. (Holothurise, Echinides,Stellerides,Crinoides.) 

Cl. 13. Polyps. Including Tunicata, Bryozoa, Anthozoa, Alcyonaria, 
and Medusae, as orders. (Ctenophorae, Siphonophorae, Disco- 
phorae, Hydroids, Anthophoridao.) 

Cl. 14. Rhizopods. Only the genera mentioned. 

Cl. 15. Infusobia. Only genera and families mentioned. 

Van Beneden thinks the classification of Linnaeus truer 
to nature than either that of Cuvier or of De Blainville, 
as the class of Worms of the Swedish naturalist corre- 
sponds to his Allocotyledones, that of Insects to his Hypo- 



362 ESSAY ON CLASSIFICATION. 

cotyledones, and the four classes of Pisces, Amphibia, A ves, 
and Mammalia, to his Hypocotyledones. He compares 
his primary divisions to the Dicotyledones, Monocotyle- 
dones, and Acotyledones of the vegetable kingdom. But 
he overlooks that the Cephalopods are not Allocotyledones, 
and that any group of animals which unites MoUusks, 
Worms, and Radiates in one great mass, cannot be 
founded upon correct principles. As to his classes, I can 
only say, that, if there are natural classes among animals, 
there never was a combination of animals proposed since 
Linnaeus less likely to answer to a philosophical idea of 
what a class may be, than that which imites the Tunicata 
with the Polyps and Acalephs. In his latest work. Van Bene- 
den has introduced in this classification many important 
improvements and additions. Among the additions, the 
indication of the orders (which are introduced in brackets 
in the diagram above) deserves to be particularly noticed. 
The changes relate chiefly to the Mollusks and Polyps, 
the Tunicata and Bryozoa being removed from the Polyps 
to the Mollusks. The Acalephs and Polypi, however, are 
still considered as forming together one single class. 

The comparison instituted by Van Beneden between 
his classification of the animal kingdom and that of plants, 
as now most generally adopted, leads me again to call 
attention to the necessity of carefully scrutinizing anew 
the vegetable kingdom, with the view of ascertaining how 
ftxr the results at which I have arrived concerning the value 
of the different kinds of natural groups existing among 
animals,^ ^Pply ^^ to plants. It would certainly be 
premature to assume that, because the branches of the 
animal kingdom are founded upon diff'erent jJans of struc- 
ture, the vegetable kingdom must necessarily be built also 

' Sec Chup. II. 



EMBRYOLOGICAL SYSTEMS. 363 

upon different plans. There axe probably not so many 
different modes of development among plants as among 
animals; unless the reproduction by spores, by naked 
poly embryonic seeds, by angiospermous monocotyledonous 
seeds, and by angiospermous dicotyledonous seeds, con- 
nected with the structural differences exhibited by the 
Acotyledones, Gymnospermeae, Monocotyledones, and Di- 
cotyledones, be considered as amounting to an indication 
of different plans of structure. But, even then, these 
differences would not be so marked as those which dis- 
tinguish the four branches of the animal kingdom. The 
limitation of classes and orders, which presents compa- 
ratively little difficulty in the animal kingdom, is less 
advanced among plants; whilst botanists have thus far 
been much more accurate than zoologists in character- 
izing families. This is, no doubt, chiefly owing to the 
peculiarities of the two organic kingdoms. 

It must be further remarked that, in the classification 
of Van Beneden, the animals imited under the name of 
Allocotyledones are built upon such entirely different 
plans of structure, that their combination must of itself 
satisfy any unprejudiced observer that any principle which 
unites them in that way cannot be true to nature. 

DIAGRAM OF THE DEVELOPMENT OF ANIMALS BY 

KOLLIKER. 

KoLLiKER (A.), in his Entwickelungsgeschichte der Cophalopoden (Zurich, 
1844, 1 vol., 4to., p. 175), has submitted the following diagram of the deve- 
lopment of the animal kingdom. 

A. The embryo arises from a primitive part. (EvoltUio ex una parte,) 

1®. It grows in two directions, with bilateral symmetry. {Evolutio bi- 

gertiina.) 
a. The dorsal plates close up. Vebtebbata. 
h. The dorsal plates remain open and are transformed into limbs. 
Aktxculata. 



364 ESSAY ON CLASSIFICATION. 

2^. It grows uniformly in every direction. (EvoltUto radiata.) And 

a. Incloses the embryonal vesicle entirely. 

a. This takes place very early . Gastebopoda and Acephala. 
/3. This takes place late. (Temporary vitelline sac.) Limax. 

b. Contracts above the embryonal vesicle. (Genuine vitelline 

sac.) Cephalopoda. 

B. The whole body of the embryo arises simultan^usly. (EvoltUio ex om- 

nibus partibus.) 
V. It grows in the direction of its transverse axis, 

a. With its hind body. Radiata. (Echinoderms.) 

b. With the fore body, and 

a. The hind body does not grow. Acalephs. 
0, The hind body grows longitudinally. Polypi. 
2". It grows in the direction of its longitudinal axis. Worms. 

I have already shown how unnatural a zoological sys- 
tem must be which is based upon a distinction between 
total or partial segmentation of the yolL^ No more can 
a diagram of the development of animals which codopts 
this difference as fundamental be true to nature, even 
though it is based upon real facts. We ought never to 
single out isolated features, by which animals may be 
united or separated, as most anatomists do ; our aim 
should rather be to ascertain their general relations, as 
Cuvier and K. E. von Baer have so beautifully shown.^ 
I think, also, that the homology of the limbs of Articulata 
and the dorsal plates of Vcrtebrata is more than ques- 
tionable. The distinction, introduced between Pol}^s and 
Acalephs and these and the other Radiates, is not at all 
better founded. It seems also quite inappropriate to call 

* Chap. III., Sect. 1, p. 288. die gcgenseitige Verwandtschaft der 

^ The principles of classi6cation l!h'icTQ zu erltingeUydi^ versc/iied^nen 

advocated by Baer arc so clearly ex- Orf^anisationsti/pen von den vfrschi- 

pressed by him that I cannot resist edenen Stufen der Aushitdung stcts 

the temptation of quoting some pas- unterscheiclen. Das man diesen Un- 

sagcs from the paper already Dien- terschied gewohnlich nicht im Auge 

tioned above (p. 351), especially now, behalten hat, scheint uns zu den son- 

when I feel called upon to oppose the derbarsten Zusammcnstellungen ge- 

views of one of his most distinguished fiihrt zu haben." Bcitriige, etc., 

colleagues. " Vor alien Dingcn muss Acta Nova, vol. 13, p. 739. 
man, um cine richtigc Eiusicht in 



EMBKYOLOGICAL SYSTEMS. 365 

the development of MoUusks evolutio radiata^ especially 
after Baer had designated, under that same name, the 
mode of formation of the branch of Kadiates, for which it 
is far better adapted. 

CLASSIFICATION OF VOGT. 

Contrast between the Embryo and the Yolk, 

I. Vertebrata. Yolk ventral. 

Cl. 1. Mammalia. 1°. Aplacektabia; Ord, MoDotremata, Marsu- 

pialia. 2®. Pl a cent aria. Ser, 1. Ord, Cetacea, Pachy- 

dermata, Solidungula, RuminaDtia, and Edentata; Ser, 2. 

Plunipedia, Camiyora ; Ser, 3. Insectivora, Volitantia, Gli- 

res, Quadrumana, Bimana. 
Cl. 2. Ayes. ^S^. 1. Insessores; Orcf. ColumbsCjOscines^Clamatorcs, 

Scansores, Raptatores ; Ser, 2. Autophagi ; Ord, Natatores, 

Grallatores, Gallinaceae, Cursores. 
Cl. 3. Reptilia. Ord. Ophidia, Sauria, Pterodactjlia, Hydrosauria, 

and Chelonia. 
Cl. 4. Amphibia. Ord, Lepidota, Apoda, Caudata, Anura. 
Cl. b, Pisces. Ord, Leptocardia, Cyclostomata, Selachia, Ganoidoa, 

Teleostia. 

II. Articulata. Yolk dorsal. 

Cl. 6. Insect A. Subcl, I. Ametabola ; Ord. Aptera. Sulci. 2. lie- 

mimetabola ; Ord, Hemiptera and Orthoptera. Subd, 3. 

Holometabola ; Ord. Dlptera, Lepidoptera, Strepsiptera, 

Neuroptera, Coleoptera, Hymenoptera. 
Cl. 7. Mtriapopa. Only divided into families. 
Cl. 8. Arachnida. Ser.\. Pycnogouida and Tardigrada ; Ord.ActL- 

rina, Amneida. Ser. 2. With three families. 
Cl. 9. Crustacea. Subcl.l. Ewtomostraca ; Or^. Cirripedia, Para- 

sita, Copepoda, Phyllopoda, Trilobita, Ostracoda. Subcl. 2. 

Xipuosura. Subcl. 3. Podophthalma ; Ord. Stomapoda, 

Decapoda. Subcl. 4. Edriophtualla ; Ord. Lacraipoda, 

Amphipoda, Isopoda. 

Transformation oj' the whole Yolk into the Embryo, 

III. Cephalopoda. Yolk cephalic. 

Cl. 10. Cephalopoda. Ord, Tetrabranchiata and Dibranchiata. 

IV. Mollusca. Irregular disposition of organs. 

Cl. 11. Cephalophora. Subcl. 1. Pteropoda. Subcl. 2. Hetero- 
PODA. Subcl. 3. Gasteropoda ; Ord, Brauchiata and Pul- 
monata. — Ch iton ida. 



366 ESSAY OK CLASSIFICATION. 

Cl. 12. AcEPBALA. Subd, 1. Bbachiopoda ; Ord. RqdiBta, Brmchi- 
opoda. Subd, 2. Lamellibban chia ; Ord, Pleurochoncha, 
Orthoconcha, Inclusa. 
Cl. 13. Tu5iCATA. Ord. Ascidise, Biphora. ^ 

Cl. 14. Ctesophora. Ord. Only subdivided into familes. > * ** "®" 
Cl. 15. Bkyozoa. Ord. Stelmatopoda, Lopbopoda. ) ^^* ®** 

y. Vermes. Organs bilateral. 

Cl. 16. AififfiLiDA. Ord. Hirudinea, €kpbjrea, Scolcina, Tubicola, 

Errantia. 
Cl. 17. Rotatoria. Ord. Bessilia, Natantia. 
Cl. 18. Plattelmia. 1**. Ord. Cestoidea, Trematoda. 2°. Ord. Pla- 

narida, Nemertina. 
Cl. 19. Nematelxia. Ord. Gregarinea, Acantbocepbala, Gordiacci, 

Kematoidei. 

YI. Radiata. Organs radiate. 

Cl. 20. Echinodermata. Ord. Crinoidca, Stcllerida, Ecbinida, Ho- 

lotburida. 
Cl. 21. SiPHONOPHOBA. Only subdivided into families. 
Cl. 22. Htdromedusjs. Not clearly subdivided into orders. 
Cl. 23. Polypi. Ord. Hexactinia, Pentactinia, Octactinia. 

No Egg. 
VIL Protozoa. 

Cl. 24. Infusoria. Ord. Astoma and Stomatoda. 

Cl. 25. Rhizopda. Ord. Monosomatia and Poljtbalamia. 

The classification of Vogt (Zoologische Briefe, q. a., 
p. 288) presents several new features, one of which is 
particularly objectionable. I mean the separation of the 
Cephalopoda from the other MoUusks, as a distinct primary 
division of the animal kingdom. Having adopted the 
fundamental distinction introduced by KoUiker between 
the animals in which the embryo is developed from the 
wliole yolk, and those in which it arises from a distinct 
part of it, Vogt was no doubt led to this st<3p in conse- 
quence of his interesting investigations upon Acta^on, in 
which he found a relation of the embryo to tlie yolk dif- 
fering greatly from that observed by Kiilliker in the Ce- 
phalopods. But, as I have already shown above, this can 
no more justify their separation as branches, than the total 



EMBRYOLOGICAL SYSTEMS. 367 

segmentation of the yolk of the Mammalia could justify 
the separation of the latter firom the other Vertebrates. 
Had the distinction made by Vogt between the Cephalopods 
and the other MoUusks the value he assigns to it, Limax 
should also be separated firom the other Gasteropods. 
The assertion, that the Protozoa produce no eggs, deserves 
no special consideration after what has already been said in 
the preceding sections respecting the animals themselves. 
As to the transfer of the Ctenophora to the type of Mol- 
lusks, it can in no way be maintained. 

Before closing this sketch of the systems of Zoology, 
I cannot forego the opportunity of adding one general 
remark. When we remember how completely independent 
the investigations of EL K von Baer were firom those of 
Cuvier, how diflferent the points of view were firom which 
they treated their subject, — the one considering chiefly the 
mode of development of animals, while the other looked 
mainly to their structure ; when we further consider how 
closely the general results at which they have arrived 
agree throughout, — it is impossible not to be deeply im- 
pressed with confidence in the opinion they both advocate, 
that the animal kingdom exhibits four primary divisions, 
the representatives of which are organized upon four dif- 
ferent plans of structure, and grow up according to four 
dififerent modes of development This confidence is fur- 
ther increased when we perceive that the new primary 
groups which have been since proposed are neither cha- 
racterized by such different plans, nor developed accord- 
ing to such different modes of development, but exhibit 
simply minor differences. It is, indeed, a very unfortu- 
nate tendency, which prevails now almost universally 
among naturalists with reference to all kinds of groups, 
of whatever value they may be, from the branches down 



368 ESSAY ox CLASSIFICATION. 

to the species, to separate at once from one another any 
types which exhibit marked differences, without even 
inquiring first whether these differences are of a kind 
that justifies such separations. In our systems, the quan- 
titative element of differentiation prevails too exclusively 
over the qualitative. K such distinctions are introduced 
under well-sounding names, they are almost certain to be 
adopted; as if science gained any thing by concealing a 
difficulty under a Latin or Greek name, or was advanced 
by the additional burden of a new nomenclature! Ano- 
ther objectionable practice, prevailing quite as extensively 
also, consists in the change of names, or the modification 
of the extent and meaning of old ones, without the addi- 
tion of new information or of new views. K this practice is 
not abandoned, it will necessarily end in making Natural 
History a mere matter of nomenclature, instead of foster- 
ing its higher philosophical character. Nowhere is this 
abuse of a useless multiplication of names so keenly felt 
as in the nomenclature of the fruits of plants, which 
exhibits neither insight into vegetable morj^holog}', nor 
even accurate observation of the material facts. 

May we not rather return to the methods of such men 
as Chivier and Baer, who were never ashamed of express- 
ing their doubts in difficult cases, and were always ready 
to call the attention of other ol)serv'ers to questionable 
points, instead of covering up the deficiency of their 
information by high-sounding words ? 

In this rapid review of the history of Zoiilogy, I have 
omitti.Ml several ehissifications, such as those of Kaup and 
Xan der lloeven, which miglit have afforded an opix)r- 
tunity for other remarks; but 1 have already extended this 
digression far enougli to sliow how the standards which I 
have proposed in my second chapter may assist us in 



EMBRYOLOGICAL SYSTEMS. 369 

testing the value of the different kinds of groups gene- 
rally adopted in our classifications, and this was, from 

the beginning, my principal object in this inquiry.^ The 

^ In this edition of the Esmy on representatives. The time has truly 

Classifimtionj which is intended as come when the whole Animal King- 

an Introduction to the study of Na- dom should he represented in its 

tural History in general, Van der development through all geological 

Hoeven's Text-book deserves more periods as fullyas the mode of growth 

than a passing notice, especially since of the living is, in our days, connected 

its translation by Professor Clark is with their general history, 

likely to be in the hands of every Respecting the classes, I believe, 

English student of Natural History, for reasons already stated (see p. 289), 

The manner in which the charac- that the Infusoria ought to be divided 

teristics of the minor groups are pre- off according to their natural affinity, 

sen ted in this work is so admirable, partly among the AlgSB, partly among 

the reference to the proper authori- the Worms, and partly among the 

ties so full, the evidence of a personal Bryozoa. The relation of the Rhizo- 

acquaintance with the objects de- pods to the lower Algse, and especi- 

scribed so general, and the freedom ally to the Corallines, seems to me 

from mere compilation so praise- daily more probable, and I consider 

worthy, that it is not only to be con- the evidence thus adduced of the 

sidered as a text-book for beginners, vegetable character of the Anentera 

but truly as a compendium of the as amounting almost to a demonstra- 

present state of Zoology, that may tion. 

be useful even to the professional Intheclassof Acalephs,theCteno- 
naturalist. phorsB occupy a position inferior to 

Although taking the views of Cuvier the DiscophorsB. It seems to me 
respecting the primary divisions of hardly questionable that they should 
the Animal Kingdom as a guide, the occupy the highest position in that 
author does not seem to hold them class. The Sipunculidse, which I am 
of such importance, or sufficiently inclined to refer to the class of worms, 
defined, to deserve a special consider- are included among the Echinoderms. 
ation. He has thus deprived himself. The ambulacral system, with or with- 
in a great measure, of the opportu- out external suckers, constitutes the 
nity of presenting in a connected essential character of the Echino- 
manner, those broader generaliza- derms. Sipunculus has none. The 
tions respecting the affinities and distinction of the intestinal worms 
homologies of the different classes of and the Annulata as two distinct 
animals, which, however, constitute classes, separated by the Rotatoria, 
the most important progress of mo- seems to me unnatural. The Turbel- 
dem Zoology, and have secured for laria and Suctoria unite the Annu- 
our science so important a place lata with the Trematodes and other 
among the philosophical studies of worms as one class, and the most re- 
cur age. It seems to me also that, cent investigations show unquestion- 
though not entirely neglected, the ably that the Rotatoria are Crusta- 
history of the fossil remains is not cea. It seems to me also unnatural 
sufficiently prominent, and the man- to separate the insects and spiders 
ner in which they are frequentlv pre- as two classes. The Tardigrada and 
sented, without connexion with the Acarina form the transition to the 
living types, is particularly unfa- PoduraandEpizoa. Theclassof Cms- 
vourable to a true appreciation of tacea, though well defined, if we add 
their natural relation to their living the Rotatoria to it, should be placed 

BB 



370 ESSAY ON CLASSIFICATION. 

next step should now be to apply these standards also to 
the minor divisions of the animal kingdom, down to the 
genera and species, and to do this for every class singly, 
with special reference to the works of monographers. 
But this is such an herculean task, that it can only be 
accomplished by the combined efforts of all naturalists, 
during many years to come. 

below the inBeets. The general cIm- Cephalopoda would easily have eatif- 
sificaiion of the branch of MoUusks fieol the author that these 



appears the least satis&ctory in this constitute for themselyes an inde- 
work, for while the Tunicata are con- pendent class, 
sidered as a distinct class, and the Since the publication of the Ani- 
Conchifera as another, including the mal Einffdom of Cuyier, Van der 
Brachiopods, the class of MoUusca Hoeven's Text-book is the only gene- 
proper includes not only the Ptero- ral work on Zoology, in which the 
poda and Ghuteropoda.. but also the dass of fishes is presented in a manner 
Cephalopoda. Evidenuy, the Cepha- indicating a thorough acquaintance 
lopoda are brought here into too with this class of animals. The treat- 
dose connexion with the Gasteropoda, ment of the other Classes of Verte- 
A fuller consideration of the fossil brata is equally deserving of praise. 



THE END. 



371 



INDEX. 



AcaUphMy their occuireDce in past 
ages, 33, n. 1; their standing, 40; 
their characteristics, 222; their li- 
mits as a class, 287, n. 

Aeari^ 121 

Aeephala, their standing, 40 

Acrita, as a primary division of the 
animal kingdom, 347 

AettnariOf their standing, 161, 223 

Actinozoaria, 217 

A]>1JI8, his worl^ 52, n. 

AoASSiz, his works, 14, n.; 19, n.; 24, 
n. 2; 28, n« 1; 35, n. 1 and 2; 37, 
n. 8; 39, n. 1 and 2; 44, n. 1, 45, 
n. 1; 46, n. 1; 48, n. 1; 58, n.; 80, 
n. 2; 92, n. 3; 113, n. 2; 116, n. 1; 
122, n. 1; 134, n. 3; 145, n. 1; 161, 
n. 1; 180, n. 9; 196, n. 2; on Pro- 
tozoa, 113; Rhizopoda, 113, 289; 
Infusoria, 113 

Albebti, his work, 142, n. 4 

AUiXAir, his papers, 105, n.; 108, n. 1 

AUocotifledoru» or AUaviUiliaru, as a 
primary division of the animal 
kingdom, 361 

Alternate generation, 135-140; differs 
from metamorphosis, 138 

Alto5 (D'), his work, 145, n-. 1 

Atnblyonsis spdcnu, 19 

AmorpKozoariay 217 

Amphilnant, a distinct class of Yer- 
tebrata, 124 

AmphioxuSy 122, n. 1 

Anaima, correspond to the Inverte- 
brata, 208 

Analogy, first distinguished from ho- 
molo^ by Swainson, 26, 130; ca- 
tegones of analogy, 271-281 

AneiUera^ Infusoria belonging to the 
vegetable kingdom, 290 

Animals, their multiplication and ori- 
gin, 15, n.; difference between them 
and man, 97, n. 2 



AnnvlcUa, 114, 116-118 

Aquatic animals, their geographical 
limitation, 43; their size, 73 

ArachnoidSy 120 

Abchiao (D'), bis works, 113, n. 2; 
141, n. 1; 142, n. 4 

Aristoteles, homological structures 
known to him, 25; his work, 25, 
n.; his distinction of man and mon- 
keys, 97, n. 2; his views of the affi- 
nities of animals, 301, 305; his di- 
vision of Articulata, 305, n. 1 ; his 
malakia, 305, n. 2 

Arthropoda, as a primary group of the 
animal kingdom, 237 

ArtictUatOy a primary division of the 
animal kingdom, 40; their classes, 
112 

Artiozoariay 217 

Association of animals, 43 

Atterioids, their standing and succes- 



sion, 162 



AuBEBT, his papers, 115, n. 1; 116, 
n. 1; 123, n. 

Audubon, his work, 85, n. 2; 214 

AuEBBACH, his paper, 113, n. 2 

AusTiK (Th. and Th. jr.), their work, 
145, n. 1 

Average size of animals, 70 

Aves, see Birds 

Babbaoe, Ninth Bridgewater Trea- 
tise, 12, n. 

Baeb, his works, 24, n. 2; 101, n. 2; 
116, n. 1; 122, n. 1; 124, n. 1 and 
2 ; his embryological researches, 
130; his principles of classification, 
350-360 

Bagoe, his paper, 114, n. 2 

Baibd, his paper, 68 n. 

Babraude, his work, 32, n. 1 

Babbt, his paper, 125, n. 3 

Bate, his papers, 119, n. 1 and 2 

Batbachia, their succession, 173 

BB 2 



372 



INDEX. 



BAin>iME5Ty his work, 125, n. 1 

BsAUMOKT (Elie de), his works, 155, 
n. 2; 157, n. 1; ms iiiTestigations 
upon the changes in the physical 
conditions of the earth's surface 
and the systems of mountains, 157 

Bell (Ch.), Bridgwater Treatise, 11 n. 

Bell (Th.), his paper with Owen, 
145, n. 1 

Bellabdi, his work, 145, n. 1 

Bevedek, see Van Beneden 

Bebeitdt, his work, 142, n. 4 

BEBOHAirB, his work, 90, n. 

Bebomak, his work, 38, n. 

Bernhabbt, his work, 125, n. 3 

Bewick, 214 

Betbich, his papers, 142, n. 4; 145, 
n. 1 

Bezold, his paper, 73, n. 

BiBBON, his work with Dumeril, 45, 
n. 2 

BiLLHABZ, his paper, 116, n. 1 

Binolet, his work, 97, n. 1 

Birds f their standing, 40; their deve- 
lopment, 125 

BiscHorF (Th. L. W.), his works, 101, 
n. 1; 114, n. 2; 125, n. 3 

Blaintillb (De), his works, 31, n. 
1; 37, n. 1; 145, n. 1; his classifi- 
cation, 316 

Blanchard (E.), his works, 92, n. 3; 
114, n. 1; 121, n. 1; 163, n. 2 

Blind Ji^h of the Mammoth Cave, 19 

Blu MEN bach, his i!?ork, 37, n. 2 

BoJANUS, his works, 116, n.l; 125, n. 3 

Bonaparte, his works, 46, n. 

Bonnet, his works, 36, n. 2; 139, n. 2 

Bosset (De), his paper, 1 10, n. I 

Bosquet, his papers, 145, n. 1 

Brachiopods, their affinity to Bryozoa, 
108; their standing and succession, 
163 

Branch Analogies, 274 

Branches of the animal kingdom, 5, 
207-219 

Braun (AI.), his works, 24, n. 3; 103, 
n; 113, n. 2 

Breathing, 20 

Bremser, his work, 186 

Bridgewater Treatises, 1 1 

Brodie, his paper, 145, n. 1 

Brooch I, his work, 142, n. 4 

Brongniart (Ad.), his works, 141, 
n. 1 

Brongniart (A1.), his works, 145, n. 



Bbovh, his works, 141, n. 1; 142, n. 
4; 144, n.1; 145, n. 1 

Bbown (R.), his work, 19, n. 

Bbuch, his paper, 116, n. 2; 122, n. 1 

Bryozoa, their standing and succes- 
sion, 162 

BucH (L. Yon), his works on fossils, 

144, n. 1; 145, n. 1; 157, n. 1 
BucKLAiTD, Bridgwater Treatise, 12, 

n.; his works on fossils, 142, n. 3; 

145, n. 1; 150, n. 3 

Buffo V, his views of classification, 2; 
his works, 85, n. 1; 99, n. 1; his 
descriptions of species, 213 

BuBBACH, his work, 101, n. 1 

BuBMEiSTEB, his works, 118, n. 2; 
119, n. 1; 134, n. 4; 145, n. 1; 248, 
n. 1 ; his classification, 324 

Burnett, his work, 120, n. 1 

BuscH, his work, 104, n. 

Busk (G.), his paper, 163, n. 1 

Canino, see Bonaparte 

Cabpenteb, hb works, 111, n.; 113, 
n. 2 

Oabteb (H. T.), his paper, 113, n. 2 

Cabus (0. G.), his works, 24, n.; 37, 
n. 2; 109, n. 1; 110, n. I; 116, n.l; 
121, n. 1 

Cabus (J. V.), his works, 24, n. 2; 38, 
n.; 116, n. 1; 136, n. 3 

Categories of Analogy, 271-281 

Cactley, his work with Falconer, 
145, n. 1 

Centres of distribution of animals, 57 

Cephalopoda, their standing, 40; can- 
not be considered as a primary di- 
vision of the animal kingdom, 288, 
366; a class of mollusks, 294; par- 
tial segmentation of their yolk, 295 

Cestoids, 114 

Chalmers, Bridgewater Treatise, 11, 
n. 

Chamisso, his work, 109, n.; on al- 
ternate generation, 136 

Chemnitz, see Martini 

CiENKOwsKT, his papcr, 113, n. 2 

Cirn'peds, 118, 129 

Claparrde, his papers, 110, n. 2; 
113, n. 2; 114, n. 2; 116, n. 4 

Clark (Br.), his paper, 188 

Classes of animals, 6, 219-228; class- 
analogies, 275; class-identity, 22 

Classification, of Aristotle, 301 ; of 
Bauer, 359; of Blainville, 316; of 
Burmeister, 324; of Cuvier, 310; of 



INDEX. 



373 



Ehrenberg, 319; of Fitzinger, 340; 
of KSlliker, 363; of Lamarck, 313; 
of Leuckart, 333; of Linnffius, 302; 
of M'Leaj, 344; of Milne-Edwards, 
330; of Oken, 337; of Owen, 325; 
of Van Beneden, 360; of Vogt, 365; 
importance of special classifications 
for the animals of each geological 
period, 7, n.; a natural classifica- 
tion might be based upon repro- 
duction, 210, n. 

Climate, 21 

OocTEAU, his paper, 64, n. 

CcddmifUha, as a class, 328 

CcdenUrata^ a primary division of the 
animal kingdom, 287 

CoHN, his papers, 113, n. 2; 118, n. 2 

OoLPST&EAM, his papers, 111, n. 1; 
119, n. 1 

Comatula, 128 

Combinations in time and space of 
various kinds of relations among 
animals, 192-199 

Community of structure among ani- 
mals living in the same region, 
60-64 

Complication of structure character- 
izes the orders of animals, 228 

Conclusions, 281-284 

Co5RAD, his works, 142, n. 4 

Corallines are genuine algse, 290 

CoRNiTEL, his paper, 145, n. 1 

CoRPA, his work, 145, n. 1 

Cosmic influences, 21 

CosTE, his works, 122, n. 1; 125, n. 3 

Crinoids, 129; their standing and 
succession, 162 

Cnutaeea, 4b, 118, 128; their geo- 
logical succession, 149; the stand- 
ing and succession of their orders, 
164; their development, 172; their 
structural gradation, 180 

Cboizet, his work, 145, n. 1 

CtenophoraSy an order of Acalephs, 
294; cannot be referred to Mol- 
lusks, 367 

Cultivated plants, 81 

CuYiER (Q.), his works, 24, n. 2; 31, 
n. 1; 37, n. 2; 45, n. 2; 75, n.; 141, 
n. 1; 163, n. 1; 163, n. 2; his four 
types or branches of the animal 
kingdom based upon the plan of 
their structure, 214; his departure 
from his own principles, 216; his 
orders, 230; does not divide the 



animal kingdom into Yertebrata 

and Invertebrata, 285; his classifi- 
cation, 308 
CuviER (Fr.), his work, 88, n. 1 ; 97, n. 
Ci/stici, 114 
Cyclostomes, 123, n. 1 
Dalman, his work, 145, n. 1 
Dalrtmple, his paper, 118, n. 2 
Dalzell, his work, 104, n. 
Dana (J. D.), his works, 44, n. 1 ; 45, 

n. 1; 136, n. 3; 142, n. 1; 248, n. 

1; 263, n. 1 
Danielson, see Kosen 
Dareste (C), his papers, 106, n.; 

125, n. 1 
Darwin (Ch.), his works, 118, n. 3; 

119, n. 1; 145, n. 1 
Dayaisne, his paper, 109, n. 1; 114^ 

n. 2 
Davidson, his work, 145, n. 1 
Davt, his paper, 122, n. 1 
De Canpole (A. P.), his work, 24, 

n. 3 
De Candole (Alph.), his work, 19, n. 
Degrees and kinds of relationship^ 

29-31 
Degrees of organisation, 37, 230 
De Haan, his work, 145, n. 1 
De Eoninck, see Koninck 
De la B^che, his work, 144, n. I 
Delle Chiaje, his work, 37, n. 2 
Derb^, his paper, 103, n. 3 
Des Haves, his works, 44, n. 3; 142, 

n. 4 ; 145, n. 1 
Desmidieas, not animals, but algao, 

290 
Des Lonoohamps, his work, 145, n. 1 
Des Marest, his work with Bboqni- 

ART, 145, n. 1 
Des Moulins, his works, 145, n. I 
Desor, his papers, 103, n. 3; 113, n. 

2; 145, n. 1 
Development of animals, 264 
Dibranchiata, their standing and suc- 
cession, 164 
Diesinq, his paper, 45, n. 1 
Dimorphcea, as a class, 328 
Dtmyaria, their standing, 1 63 
Dingo, its origin doubtful, 60 
Diversified types found everywhere, 

15-21 
DOllinqeb, 101, n. 1 
Domesticated animals, 81 
DowLEB, his paper, 122, n. 1 
Duress^ his paper, 122, n. 1 



374 



INDEX. 



DuFOUR) his work, 116, n. 2 
DuQ^, his works, 111, n. 1; 188, n. 1 
DuJARDiN, his works, 45, n. 1; 104, 

n.; 121, n. 1 
Pumas, his paper with Pr6vost, 125, 

n. 3; his work, 185, n. 1 
PuMERiL (A. M. C), his work, 45, 

n. 2; 64, n.; 307, n. 2 
DuMORTiER, his papers, 108, n. 1; 

110, n. 1 

PuTRocHET, his work, 125, n. 

PuvERNOY, his paper, 1 22, n. 1 

Puration of life, 133-135 

Early attempts to classify animals, 
300-302 

Earliest types of animals, 31-36 

Echinodemu, their standing, 40; their 
geological succession, 149; their 
development and geological succes- 
sion, 170; their structural grada- 
tion, 180; their characteristics, 222 ; 
not to he considered as a primary 
division of the animal kingdom, 
287; a class of Radiata, 294; cte- 
nophoroid characters of the young 
Ecninoderms, 294 

Echinoidsy their standing and succes- 
sion, 162 

EcKER, his paper, 104, n. 

Edwards (F. E.), his works, 142, 
n. 4 

Edwards (H. Milne), his works, 44, 
n. 1; 44, n. 3; 45, n. 1; 109, n.; 

111, n. 1; 115, n. 1; 117, n. 2; 118, 
n. 3; 119, n. 1; 139, n. 1; 169, n. 
1 ; his classification, 330 

Eqeuton (Sir Ph.), his paper, 145, 
n. 1 

Eggs in all animals, 101; classifica- 
tion based upon eggs, 210, n. 1; by 
Vogt, 365 

Egyptian monuments, 82 

EiiRENBERO, his works, 16, n. 1; 108, 
n. 3; 136, n. 3; 145, n. 1; 285, n. 
1 ; his classification, 319 

Elephanty the young compared to 
Mastodon, 174 

Embryological systems, 350-369 

Embryology, its bearing upon classi- 
fication, 4, 99, 126 

Embryonic types, 174 

Emmkricii, his work, 145, n. 1 

Enaima, correspond to Vertebrata, 
208 

Entomostraca, 118 



Epicotyledones or EpivUdUaiMy a pri- 
mary division of the animal king- 
dom, 361 

Epizoa^ as a class, 328 

Erdl, his paper, 119, n. 2 

ESCHEB VON DEB LiHTH, hifl papCT 

with Uier, 145, n. 1 
Eschricht, his work, 109, n. 
EscHSCHOLTZ, his work, 44, n. 1 
Falconer, his work, 145, n. 1 
Fabre, his paper, 120, n. 1 
Families, 6, 236-247 
Family analogies, 276 ; £Eunilj iden- 
tity, 22 
Faunae, 48 

Favre (A.), his paper, 145, n. 1 
F^NissAC, his work, 44, n. 3 
FiLipPi (Fil. de), hia paper, 117, n. 

2; 122, n. 1 
(Theo. de), his papers, 116, 

n. 1 
FishtSy their standing, 40, 122; the 

fishes proper form a distinct class 

of Vertebrata, 299 
FiTziNOER, his works, 45, n. 2 ; 234; 

his classification, 340 
Flesh-animals, 208 
Florae, 48 
Forbes (Ed.), his works, 103, n.; 103, 

n. 3; 128, n. 1; 145, n. 1 
Forchhammer, his work, 122, n. 1 
Form, different meanings of the term, 

236; characterizes the families of 

animals, 236 
Frantzius, his paper, 104, n.; 108, 

n. 1; 116, n. 2 
Fr^my, his paper with Valenciennes, 

102, n. 
Fresh water animals, 73 
Fret, his works, 37, n. 2; with Leuck- 

art, 104, n. 
Fundamental relations of animals, 

1-14 
FuxK, his work, 124, n. 2 
Ganoids jQ.dAsimci class of Vertebrata, 

299 
Ganglioneura, 208 
Gasteropoda, their standing, 40 
Gegenbauer, his works, 44, n. 1; 103, 

n. 3; 110, n. 1; 118, n. 3 
Oeinitz, his work, 142, n. 4 
Genera, 6,247-249; views of Aristotle, 

301 
General remarks upon modem sys- 
tems, 285 300 



INDEX. 



375 



Generic analogies, 278 ; generic iden- 
tity, 22 
Geoffbot St. Hilaire (£t.), his 

works, 24, n.; 97, n. 1; 145, n. 1 
Geoffbot St. Hilaire (Isip.), his 

works, 73, n.; 98, n.; 215, n. I 
Geographical range of animals, 42-52; 

not accidental, 60; in past ages, 152 
Gebtais, his work, 145, n. 1 
Gebmab, his work, 142, n. 4 
Gibes, lus paper, 145, n. 1 
Giebel, his work, 144, n. 1 
Gills and lungs compared, 92 
GiBABP, his paper, 113, n. 2 
GLIDD05, ue NOTT 
Goethe, works on Natural History, 

24, n. 3 
GoLDFUss, his works, 141, n. 1; 145, 

n. 1 
GooDsiB (H. D. S.), his paper, 11 9, n.l 
Goppebt, his work on fossil plaiits, 

141, n. 1 
GossE, his work, 105, n.; 106, n.; 118, 

n. 2 
Gould (A. A.), his works, 37, n. 2; 52, 

n.; 244, n. 1 
Gradation of structure among ani- 
mals, 34, 36-42; how it corresponds 

to the order of their succession in 

geological times, 42 
Gba5T, his works, 37, n. 2 
Grateloup, his work, 142, n. 4 
Gray (G. R.), his work, 45, n. 2 
Great types or branches of the animal 

kingdom, 207-219 
Gbee5, his work, 145, xl 1 
OregarincBy 116 
Gbube, his work, 45, n. 1; 114, n. 2; 

117, n. 2 
Gublt, his catalogue of worms, 45, 

n. 1 
Gut-animals, 208 
GuTBiEB, his work, 142, n. 4 
Habitat of animals, 48 
Hackel, his paper, 122, n. 1 
Haoenow, his work, 145, n. 1 
Haime, his paper with Edwabds, 44, 

n. 1; his paper on Cerianthus, 103, 

n. 1; his work with D'Archiac,113, 

n. 2; 162, n. 1; 169, n. 3 
Halcyonaria^ their standing, 161, 223 
Hall (J.), his works, 32, n. 1; 142, 

n. 4; 145, n. 1 
Hanmebschmidt, his paper, 116, n.2 
Hancock, his paper, 108, d. % 



ITabbis (T. W.), his work, 85, n. 2. 

Hasselt, his paper, 124, n. 1 

Haw5 (F.), his paper, 142, n. 4 

IIawle, his paper with Oorda, 145, n. 1 

Hatpen, his paper, 133 

H ECKEL, his paper, 145, n. I 

Heeb, his papers, 145, n. 1 ; 150, n. 3 

HelmirUhty 114 

Henle, his work with Miiller, 45, n. 

2; his paper, 116, n. 2 
Hebold, his works, 120, n. 1; 121, n. 

1; 134, n.2 
Hi5CKS, his papers, 105, n.; 108, n. 1 
Hooo, his paper. 111 n. 
Holbbook, his work, 68 n. 
Holothurioids, their standing, 162 
Holmes, see Tuomet and Holmes 
Homarus Americanue^ 6 
Homology, 26, 130,172 
Homologies of disconnected animals, 

25-29; limited to animals of the 

same branch, 226 
HSxivaHAUss, his paper, 145, n. 1 
H5B5ES8, his work, 142, n« 4 
HoBiTEB (F. R.), his paper, 125, n. 1 
HoTEB (H.), his paper, 125, n. 1. 

HUBEB, 214 

Humboldt (A. v.), his works, 19, n. 1 
(W. v.), his works, 19, n.; 

98 n. 
Hun TEE (J.), his works, 125, n. 1. 
HuTTOH (W.), his work with Likdlbt, 

141, n. 1 
HuxLET, his works, 102, n. 1; 105, 

n.; 106, n.; 108, n.l; lll,n.; 113, 

n. 2; 115, n. 1; 118, n. 2 and 3; 

his account of Baer*s view, 358, n. 
Hybridity, 250 
Bvdroids, 136 
ifydrozoaj as a class, 328 
HypembiTonic types, 175 
IJi/po€otyledone9y or Iltfpovitdlians, 

correspond to Yertebrata, 361 
Identical types found everywhere, 21- 

23 
Identity of structure of widely distri- 
buted animals, 52-60 
Immaterial principle of the animal8,97 
Immutability of species, 3, 75-84 
Independence of organixed beings of 

physical causes, 22 
Individuals, 8, 30. 256, 266 
Individuality among animals, 97, 252 
Inequality of all the natural groups 

of the animal kingdom, 263 



376 



INDEX. 



Infusoria are not a natural division 

of animals, 290,113 
Insecta^ a class in the system of Lin- 
naeus, 304, 120 
IntectSf their standing, 40 
Intestinal Worms not Badiata, 292 
Invertebrata, 208 
Jacquemik, his paper, 110, n. 1 
Jaoer, his works, 145, n. 1 
JoBEBT, his work, 145, n. 1 
JoHHSTOir (Al. E.), his work, 90, n. 
Jones (T.R.),hisworks,37,n.2; 145,n.l 
J URINE, his works, 118, n. 3 
JussiEu, his characteristics of genera, 

214 
Kaisebltno, his works, 32, n. 1 
Kaufman, his paper, 121, n. 2 
Kaup, his work with 6R0NN,i45,n. 1; 

his Tiews of orders, 234 
Keber, his paper, 114, n. 2 
Keferstein, his work, 141, n. 1 
KiDD, Bridgwater Treatise, 11 n. 
KiENER, his work, 44, n. 3 
Kino, his work, 142, n. 4 
Kingdoms of nature, 215, n. 1 
KiRBT, Bridgwater Treatise, 12, n.; 

86, n. 2; 132, n. 2; 134, n. 4 
Koch, his paper, 117, n. 2 ; 188, n. 1 
K6LLIKER, his works, 44, n. 1; 101, 

n. 1 ; 103, n. 3; 108, n. 3; 110, n. 

1; 111, n. 1; 113, n. 2; 114, n. 1 

and 2; 116, n. 2; 120, n. 1; his 

classification, 303 
KoNiNCK (De), his works, 142, n. 4; 

145, n. 1 
KoREN and Danielbon, their papers, 

106, n.; 110, n. 1 
Krohn, his papers, 104, n.; 105, n.l; 

108, n. 3; 110, n. 1; 117,n. 2;118, 

n. 1; 118, n. 3. 
KucHENMEiSTER, his works, 1 15, n. 1 ; 

186, n. 1 
Kdnth, his paper, 78, n. 
KuTziNG, his paper, 113, n. 2 
LACAZE-DuTiiiERSjhis papcf, 109, n. 1 
Lachman, his paper, 108, n. 1 
Lacordaire, his work, 134, n. 1 
Lam ARK, his works, 3, n.; 36, n. 3; 

44, n. 3; 141, n. 1; 307, n. 3; his 

classification, 313 
Lamellibranchiata^ their standing and 

succession, 163; their young, 172 
Latreille, his work, 248, n. 2; anec- 
dote, 248 
Laurent, his paper, 110, n. 1 



Latalbttb (A. de), 116, n. 1 

Lea, his papers, 142, n. 4; 145, n. 1 

Leading groups of the existing sys- 
tems of animals, 207 

Lebert, his papers with P&tvosT, 
124, n. 2; 125, n. 1 

Ls Conte, his paper, 145, n. 1 

Leidt, his papers, 103, n. 3 ; 114, n. 
2; 116, n. 1 and 2; 117, 2; 145, n. 
1; 153, n. 3 

Le Hon, his paper with Koninck, 145, 
n. 1 

Lenz, his work, 85, n. 2 

Lfpidost€us, its young, 173 

Lereboullet, his papers, 119, n. 2; 
122, n. 1 

Lernjbans, 118, 129 

Lesson, his work, 44, n. 1 

Leuckart (F. S.)> his works, 122, n. 
1; 144, n.l 

Leuckart (B.), his works, 24, n. 2 ; 
37, n. 2; 38, n.; 44, n. 1; 92, n. 2; 
102, n. 1; 104, n.; 105, n.; 108, n. 
2; 109, n.; 115, n.l; 117, n. 2; 120, 
n. 1; 136, n. 3; 186, 286; his pri- 
mary divisions of the animal king- 
dom, 333 

LETniG, his works, 104, n.; 109, n.l ; 

110, n. 1; 116, n. 2; 118, n. 2 and 
3; 120, n.l; 122, n.l; 165, n.l; 293 

Ltebio, his work, 185, n. 2 

LiEBERKunN, his papers, 113, n. 2; 
114, n. 2; 116, n. 2 

Limitation of species to particular 
geological periods, 155-159 

LiNDLEY, his works, 141, n. 1 

LiNNfus, fauna Suecica, 98, n. ; the 
editions of his system, 303, n. 1; 
orders, 214, 230; genera, 247; he 
first introduced classes and orders 
as natural divisions among animals, 
220; his classification, 304 

Localization of special structures,62-64 

Localization of types in past ages, 
152-155 

Locomotion, 20 

LoNGCHAMPS (Db Selys), 250 

LoNGET, his work, 101, n. 1. 

LoxsDALE, his work, 145, n. I 

LovEN, his work, 103, n. 3; 109, n. 1 ; 

111, n.; 117, n. 2. (Correct "Lo- 
ren'' to " Lovcn", 1 1 1 ) 

Lund, his paper, 152, n. 1; his inves- 
tigations upon the fossils of the 
Brazils, 152 



INDEX. 



377 



LuscHKA, his paper, 114, n. 2 
Ltcett, see Mokbis 
Ltell, his work, 144, n. 1 
M'CoT, his works, 32, n. 1; 142, n. 4; 

145, n. 1 
M'Cbadt, his paper, 105, n. 
McDonald, his paper. 111, n.; 163, 

n. 2 
M'Leat, his work, 345, n. 2; his clas- 
sification, 344 
Maillet (Db), his work, 179, n. 1 
Mammalia, their standing, 40; their 

development, 1 25 ; their yolk under- 
goes a complete segmentation, 2b8; 

peculiar to New Holland, 60 
Man and Animals, difference between, 

65, n. 
Maroott, his work, 142, n. 4 
Marine animals, their size, 73 
Martin St. Anqe, see St. Anob 
Martin and Chemnitz, their work, 

44, n. 3 
Mariupialia, cannot be considered as 

a distinct class, 298 
Mathbron, his work, 142, n. 4 
Meek (F. B.), his paper, 142, n. 4 
Meckel t. HEMSBAOH,his paper, 125 
Meckel, his works, 37, n. 2; 125, n. 1 
Medusa, 138 

Meigs (Oh.), his paper, 125, n. 3 
Meissner (G.), his papers, 114, n, 2; 

115, n. 1 
Menoe, his paper, 117, n. 2 
Metamorphoses of animals, 99-132 
Metamorphosis, differs from alternate 

generation, 100, n. 3 
Met en, his work, 109, n. 
Meter (H.), his work, 120, n. 1 
Meter (H. v.), his work, 145, n. 1 
MiOHELiN, his work, 145, n. 1. 
Michelotti, his work with Bellandi, 

145, n. 1 
MiUepora, not a Polyp but a Hy- 

droid, 34 
Miller (Hugh), his works, 12, n.; 

163, n. 3 
Miller (J. C), his work, 145, n. 1 
Milne-Edwards, see Edwards 
Modern System in Zoology, 285-300 
MoUtuks. a primary division of the 

animal kingdom, 40, 287; their 

classes, 108 
MoNOEOT, his work with Schimper, 

150, n. 2 
Monomyaria, their standing, 163 



Monstrosities, 131 

Moral faculties in man and the higher 

animals, 97 
Morris and Ltoett, their work, 142, 

n. 4; 155, n. 3 
Morton, his works, 142, n. 4; 250, n. 1 
MuLLER (A.), his paper, 122, n. 1 
MiiLLER (J.), his works, 24, n. 2; 44, 

n. 1 ; 45, n. 2; 101, n. 1 ; 103, n.; 

105, n. 1; 110, n. 1; 113, n. 2; 116, 

n. 2; 122, n. 1; 142, n. 4; 145, n. 1; 

162, n. 4; 180, 1; 290, n. 2; his 

embryological researches on Echi- 

noderms, 138 
MiiLLER (H.), his papers, 109; 111, 

n. 1 
MuLLER (M.), his papers, 117, n. 2; 

118, n. 1 
MuNSTER, his works, 145, n. 1 ; 149, 

n. 2 
MuROHisoN, his works, 32, n. 1 
Mutual dependance of the animal and 

vegetable kingdoms, 185-186 
Mveloneura, 208 
MyriapodSy 120 
Hyzontes, a distinct class of Yerte- 

brata, 123, n. 1 
NaoELi, his papers, 113,n. 2; 118,n. 1 
Narrowest limits within which ani- 
mals may be circumscribed, 49-52 
Natural System, 8, 31 
N Air MANN, his works, 144, n. 1; 814 
Natural provinces of animals and 

plants, 48 
Nelson, his paper, 114, n. 2 
NematoidB, 114 

Newberrt, his paper, 145, n. 1 
Newport, his papers, 114, n. 2; 120, 

n. 1; 124, n. 2 
Nitzsoh, his work, 188 
NoRDMAN, his works, 104, n.; 110, n. 

1; 116, n.l; 118, xl 3; 129, n. 2 
NoTT and Gliddon, their works, 79, n. 
Notice of the principal Systems of 

Zoology, 285 
Oersted (A. S.), paper, 117, n. 2 
Oken, his works, 24, n. 1, 2; 179; 

235; 236, n.; his classification, 337 
Oldest fossil remains, 17, n.; 31-36 
Opalina, genus of Infusoria based 

upon embryos of Distoma, 291 
Orbiqnt (D'), his works, 142, n. 4; 

144, n. 1; 145, n. 1; 155, n. 3; 162, 

n. 3 ; 163, n. 1 ; his work with 

FlNissAc, 44, n. 3 



378 



INDEX. 



Orders among animals, 6; 228-236; 
their gradation, 41 

Ordinal analogy, 275 

Ordinal identity, 22 

Organised beings, their relations to 
physical causes, 13, n. 

Organs without function, 12 

Origin of animals and plants, 15, n. 

Ornamentation a specific character, 
259 

Other natural divisions among ani- 
mals, 261-264 

Otto, his work with Oaittb, 37, n. 2 

Oviparous animals, 131, n. 1 

Owen (D. D.), his work, 145, n. 1 

Owen (R.), his works, 24, n.; 37, n. 2; 
61, n. 2; 101, n. 1; 125, n. 1 and 3; 
136, n. 3; 145, n. 1; 153, 2 and 3; 
163, 163, n. 2; 299, n. 3; his clas- 
sification, 325; his investigations 
upon the fossils of Australia, 153 

Pan PER, his works, 125, n. 1 ; 351, n. 1 

Parallelism between the geological 
succession of animals ana the em- 
bryonic growth of their living re- 
presentatives, 168-175 

Parallelism between the structural 
gradation of animals and their em- 
bryonic growth, 178-181 

Parallelism between the geological 
succession of animals and plants 
and their present relative standing, 
159-168 

Paramecium f genus of Infusoria based 
upon embryos of Planaria 

Parasites, 45 

Parasitic animals and plants, 186-191 

Peach, his paper, 105, n. 

Pedicellina forms the connecting link 
between the ordinary Bryozoa and 
Vorticellae 

Peirce (Benj.), his discovery of the 
relations between the laws regu- 
latiug revolutions of the members 
of our solar system and the arrange- 
ment of leaves in plants, 193 

Pebcheron, his work, 45, n. 1 

Period of Linnaeus, 302-308 

Period of Cuvier and anatomical sys- 
tems, 308-336 

Permanency of specific peculiarities of 
all organized beings, 75-84 

Perty, his works, 113, n. 2 

Peters (W.), his paper, 118, n. 1 

Pfeiffer, his work, 44, n. 3 



Pheasants do not exist in America, 62 

Phillips, his works, 142, n. 4 

Phyllotaxis, 193 

Physical causes, 16, n. ; 21, 23,47, 47, il 

Physiophilosophers, 235 

Physiophilosophical systems, 336-350 

PiOTBT, his works, 142, n. 4; 144, n. 1; 
145, n. 1; 148, n. 1; 156, n. 6 

Pisces, see Fishes 

Plagiostoms, their developnient, 123, 
n. 1; constitute a distinct clasSy 
133, n. 1 

Plans of Structure, 34 

Plan of structure characterizes the 
branches of the animal kingdom, 207 

Plants, their geological succession, 
150, 167 

Plieninqer, his work with H. t. 
Meyer, 145, n. 1 

PoL^ his paper, 163, n. 1 

Polymorphism among Acalephs, 137, 
n. 1 ; among Polyps, 137, a. 1 ; 
among MoUusks, 137, n. 1; among 

Articulata, 137, n. 1 

Polycistince no animals, 290, n. 

Polyps, their standing, 40; their limits 
as a class, 287, n.; their character- 
istics, 222; their development, 169; 
the freshwater Polyps are Bryozoa, 
with the exception of Hydras, 44, n. 

PoMppER, his work, 46, n. 

PoucHET, his works, 31, n. 1 ; 1 10, n. 1 

Powell, his work, 3, n.; 11, n.; 17, n.; 
76, n. 

Prevost, his papers, 109, n. 1; 110, 
n. 1; 122, n. 1; 124, n. 2; 125, n. 1; 
125, n. 3 

PriinateSy their standing in the sys- 
tem of Linnaeus, 230 

Primitive limits of distribution of 
animals, 58 

Progressive types, 177 

Prophetic types among animals, 1 75- 
178 

Proportions characterize species, 249 

Proscu, his paper, 136, n. 3 

Protozoa as a primary group of the ani- 
mal kingdom,113;287;289; 333,n.l 

Proteus aiiguinuSj 20 

Protozoa, 113; as a primary group of 
animals, 287, 289 

pROUT, Bridgwater Treatise, 12, n. 

Psorospemiia, 116 

Pdrkinje, his work, 101, n. 2 

PuscH, his work, 142, n. 4 



INDEX. 



379 



Pycnogonwn^ 121 

QuATSEFAOEB, his works, 105, n. ; 

109, n.; 109, n. 1; 110, n. 1; 117, 

n. 2; 122, n. 1; 163, n. 2 
QuEKSTEDT, his works, ] 42, n. 4; 144, 

n. 1 ; 145, n. 1 
QuETELST, his work, 133, n. 1 
Radiatn, a primary division of the 

animal kingdom,40 ; their cla88e8,106 
Rang, lee Sardeb-Rano 
Rangeof distribution of animals, 31 , n. 
Rathke, his works, 103, n. 1; 111, n. 
' 1; 119, n. 2; 120, n. 1; 121, n. 1; 

122, n. 1; 124, n. 1 and 2; on the 

embryology of Articulata, 130 
Ratzebubq, his works, 85, n. 2; 188 
Reality or ideality of the existence of 

species, genera, families, etc., 252 
Recapitulation, 199-206 
Reaumub, his work, 85, n. 1; 213 
Reeve (Loyell), his work, 44, n. 3 
Reichekt, his works, 102, n. 1; 122, 

n. 1; 124, n. 2 
Reid, his paper. 111, n. 
Relations between animals and plants 

and the surrounding world, 84-94 
Relations between the structure, the 

embryonic growth, the geological 

succession, and the geographical 

distribution of animals, 181-185 
Relation of Individuals to one ano- 
ther, 94-99 
Relative standing of the four branches 

of the animal Kingdom, 38 
Remak, his work, 124, n. 2 
Beptilesy their standing, 40; a distinct 

class of Yertebrata, 124 
Representative species in the succes- 

sive geological periods, 81 
Retzius, his work, 122, n. 1 
Reuss, his work, 142, n. 4 
Revolutions (The) of the members of 

our Solar System compared to the 

arrangement of leaves in plants, 192 
Rhizopoda, their true nature still 

doubtful, 113, probably AlgsB, 289 
RiGHABDBOiR (SiB John), his works, 

45, n. 2 
RiDiNGEB, his works, 97, n. 1 
Robin (Ch.), his work, 186, n. 1 
RooET, Bridgwater Treatise, 11, n. 
R5MEB (F. A.), his work, 142, n. 4; 

144, n. 1 ; 145, n. 1 
RoQUAir, his work, 145, n. 1 
Rotifera are Crustacea, 164 



R5sel, hiB works, 100, n. 1; 124, n. 2; 

213 
RonoET, 104, n. 
RouLiif, his paper, 111, n. 1 
Ronx, his work, 142, n. 4 
RuDOLPHiir, his works, 45, n. 1 
Rugosa^ 162; their affinities, 170, n. 
RiippELL, his paper, 190, n. 3 
Rusooiri, his works, 122, n. 1; 124,n.2 
SalpcBy 138 

Saltbb, his paper, 145, n. 1 
Sandbeboxb (G. & Fb.), their works, 

142, n. 4 
Sandeb-Rang, his work with F^i8- 

SAO, 44, n. 3 
Sabs, his works, 103, n. 1; 109, n.; 

110, n.l; 113, n. 2; 138, n. 1 
Saussine (H. db), his paper, 120, n. 1 
Sayight, his works, 24, n. 2; 108, n. 3 
Sohbitlin, his work, 88, n. 
Soheuohzeb, his work, 142, n. 3 
SoHEUTEB ^A.), his paper, 121, n. 1 
Sohimpeb, his work, 150, n. 2 
SoHLEGEL (Fb.), his work, 98, n. 
ScHLOTTHXiM, his work, 141, n. 1 
ScHMABDA, his work, 19, n.; 48, n.; 

118, n. 1 
Sghmebling, his paper, 145, n. 1 
Schmidt (A.), his paper, 116, n. 2 
Schmidt (0.), his paper, 109, n. 1; 

110, n. 1 
SoHNEiDXB,hispaper,lll,n.; 113,n.2 
SoHocw, his work, 19 n. 
ScHUBEBT (T. !>.)» his paper, 121, n. 2 
Sou n BLEB, his work, 133, n. 1 
ScHULTZE (M.), his works, 105, n.; 
106, n.; 110, n. 1; 113, n. 2; 117, 
n. 2; 122, n. 1; 290, n. 
Science, its true limits, 13, 281 
SoiLLA (Ag.), his work, 142, n. 2 
Scincoidsy their classification and geo- 
graphical distribution, 65 
Sedgwick, his works, 32, n. 1 
Selachians, a distinct class of Yerte- 
brata, 123, n. 1; first distinguished 
by Aristotle, 302 
Sempeb, his papers. 111, n.; 120, n. 

1; 121, n. 2 
Series in the animal kingdom, 20, 34, 

36, 38, 40, 69, 343 
Serial connexion among animals, 64- 

69 
Sexual relations among animals con- 
sidered as a criterion of specific dif- 
ferences, 250 



380 



INDEX. 



Sharps, his paper, 142, n. 4 
Shaw, his paper, 122, n. 1 
Shumard, his paper, 145, n. 1 
SiEBOLD (C. Theo. t.), his works, 37, 

n. 2; 103, n. 3; 115, n. 1; 116, n. 

1; 120, n. I; 139, n. 2; his primary 

diyisions of the animal kmgdom, 

287; his classification reviewed, 331 
/SipunctUoidSy 118 
Sismonda (£.), his paper, 145, n. 
Size and structure of animals, 70-72 
Size of animals in its relations to the 

medium in which thej live, 73-75 
Smeathman, 214 

SowERBT (Jam.), his work, 141, n. 1 
Species, p. 6, 249-261; yiews of Aris- 
totle, 301 
Specific analogies, 279 
Specific identity between living and 

fossil animals difficult to ascertain, 

155 
Specific differences, 22 
Speuce, his work with Kirbt, 85, n. 

2; 132, 1 n.; 134, n. 1 
Spix, his works, 24, n.; 31, n. 1 
Spbikg, his work, 148 
St. Asqe (Martin), his paper, 119, 

n. I; 125, n. 1; 129, n. I 
Stannius, his work with Siebold, 37, 

n. 2; his papers, 101, n. 1; his clas- 
sification, 331 
Steumbero, his work, 141, n. 1 
Steenstrup, his works, 104, n.; 109, 

n.; 112, n.; 116, n. 1; 136, n. 2; 

on alternate generation, 136 
Stein (F.),hi8 works, 108, n. 1; 114, 

n. 2; 116, n. 2; 120, n. 1 
Steinheim, his paper, 124, n. 2 
Stein thal, his work, 98 n. 
Sterelminthay as a class, 328 
Stimpson, his paper, 105, n. 
Strata, the lowest strata known to 

contain fossils, 17, n. 
Structural gradation of animals and 

their embryonic growth, 179 
Structure of parts characterizes the 

genera, 247 
Strauss-Durkheim, his work, 12, n. 
Sub-branches, 263 
Sub-classes, 262 
Sub-families, ib. 
Sub-genera, ih. 
Sub-orders, ib. 
Succession of animals and plants in 

geological times, 140-162, 159 



Successive development of characters, 

264-271 
Swallow (J. C), his paper, 142, n. 4 
SwAiNSON, his work, 19, n.; 26, n.; 

130, n. 2; 345 
SwAMME&DAM, his work, lOOy n. 1 
St/napta di^iUUa, harbours yoang 

snails, 110, n. 
Synthetic types, 177 
Systems of zooloffy, 286 
Tabulata are Hyaroids, and not genu- 
ine Polyps, 162 
Tellkampf, his paper, 19, n. 
Terrestrial animals, their geographi- 
cal distribution, 43; their size, 73 
Tetrabranchiataf their standing and 

succession, 164 
Thalassicokgy no animals, 290, n. 
Thomas, his paper, 124, n. 2 
Thompson (Allen), his papers, 114, 

n. 2; 129, n. 1; 130, n. 1 
Thompson (W. Y.), his paper, 119, 

n. 1 
Thought in nature, 18, 166 
TiEDEMANN, his works, 124, n. 1 ; 162; 

n. 4 
Todd, his work, 37, n. 2 
Tremaiods, 115 
Tremblev, 214 
Treviranus (G. R.), his work, 37, 

n. 2 
Tropical families, generally highest 
I in their class, or representatives of 

older types, 182 
I TuoscuEL, his works with Muller, 

44, n. 1; 112, n.; 162, n. 4 
TsGHUDi, his works, 45, n. 2; 68, n. 
TuoMET and Holmes, their work, 142, 

n. 4 
Turbellarxce, 114 
Types, 5, 21; different meanings of 

the word, 218; v. Baer's views, 353 
Typical identity, 22 
Udekem (J. de), his paper, 117, n. 2 
Unoer, bis work, 150, n. 4 
Unity of plan in diversified types, 23 
Valenciennes, his works, 45, n. 2; 

102, n.; 115, n. 1; 121, n. 2; 122, 

n. 1; 163, n. 2 
Valentin, his works, 101, n. 1; 122, 

n. 1; 162, n. 4 
Van Beneden, his work, 104, n.; 108, 

n. 1; 109, n.; 110, n. 1; HI, n. 1; 

115, n. 1; 118, n. 3; 121, n. 1 and 

2; his classification, 360 



IXDEX. 



381 



Van deb Hoeven, his works, 38, n.; 
112, n.; 163, n. 2; his Text-Book, 
369, n. 

Varieties, 268 

Veraxt, his work. 111. n. 1 

Vermes, see Worms, considered as a 
primary group of the animal king- 
dom, 287, 332; this view not cor- 
rect, 296; a class in the system of 
Linnaeus, 304 

Yebveuil (De), his works, 32, n. 1; 
142, n. 4 

Vertebrata, a primary division of the 
animal kingdom, 40,208, 287; their 
succession in geological times, 165 

Viviparous animals, 131, n. 1 

VooT, his works, 44,n.l; 103, n.3; 108, 
n. 3; 110, n.l; 122, n. 1; 124, n. 2- 
144. n. 2; 163, n. 1; his paper with 
Vebant,! 1 1, n. 1 ; his primary divi- 
sions of the animal kingdom, 288; 
his classification reviewed, 365 

VoLKMAN, his work, 124, n. 1 

VoLTZ, his paper, 145, n. 1 

Volvocincgf not animals, hut algas, 290 

VorticeUcB are genuine Bryozoay 108, 
291 

Waqexeb, his work, 115, n. 1 

Wagxeb (A.), his work, 46, n. 

Wagneb (R.), his works, 37, n. 2; 
101, n.l; 101, n.2; 114,n.2; 115,n.l 

Walteb (G.), his paper, 114, n. 2 

Waeneck, his paper, 110, n. 1 

Wabeen, his work, 145, n. 1 

Watebhouse, his work, 61, n. 



Ways in which and means by which 

the plan of structure of animals 

is carried out characterises the 

classes, 219 
Webeb, his paper, 117, n. 2 
Wei5LANd, his papers, 124, n. 1 and 

2; 125, n. 1; 190, n. 1; 263, n. 1 
Whewell, Bridgwater Treatise, 

11, n. 
WiEOMAN, his work, 250 
WiED (Pb. Max. y. Nbu-), his work, 

269 
Will, his work, 104, n. 
Willi AM805, his paper, 118, n. 2 
Wilms, his paper, 118, n. 3 
Wilson (£.), his paper, 121, n. 2; 214 
WiXDi8CHMAir5, tiis paper, 110, n. 1 
WiTTiCH, his papers, 121, n. 1; 124, 
• n. 2 

W0LLA8T05, his work, 248, n. 1 
Wood, his work, 142, n. 4 
WooDWABD (8. P.), 145, n. 1 
WomUy their standing, 40 
Wbioht (T. S.), his paper, 105, n. 
Wbiqht (C), his paper, 193, n. 2 
Wtmav (J.), his works, 19, n.; 122, 

n. 1; 124, n.2; 125, n. 3; 145, n.l; 

153, n. 3; rudimentary eye in the 

blind fish, 20 
Tabbell, his work, 122, n. 1 
Zaddach, his works, 118, n. 3; 120, 

n. 1 
ZiETEir, his work, 142, n. 4 
ZiMMEBMANK, his work, 19, n. 
Zoological realms, provinces, etc., 49 



T. RICHARDfi, 37, ORRAT (jl'RKN KTRSET. 



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