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E. D. COPE, A. M., Ph. D. (Heidelberg) 






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The twenty-one essays which constitute the present volume represent 
the reflections which have suggested themselves to the author while engaged 
in special zoological and paleontological studies. While the original work 
of the author has been nearly confined to the vertebrata, his studies have 
taken in a wider range. These have convinced him that the conclusions 
derived from the investigations of the vertebrata are applicable to inverte- 
brate animals and to plants. 

In reaching conclusions, the author has endeavored to avoid, as much 
as possible, any bias due to the influence of any opinions whatsoever on 
evolution and allied subjects which were already in the field. He therefore 
avoided, for a time, reading the works of the masters of the subject, apply- 
ing to them for confirmation or criticism only after the publication of his 
own results. It is therefore true that the generalizations contained in these 
essays have been worked out by tlie author from such material as has come 
under his own eyes, with little other aid. It has also followed that not a 
few of the conclusions he has reached were not new. On the other hand, 
some of the principles enunciated had not been clearly stated prior to the 
publication of these essays. In some cases the work accomplished has con- 
sisted in throwing well-known principles into accord with each other, as in 
the case of the laws of acceleration and retardation. 

The earlier essays are the more hypothetical, and the later present more 
numerous demonstrations. The latter have resulted chiefly from the author's 
researches in the field of vertebrate paleontology, which have thrown the 
greatest possible light on the fact and method of evolution. For the his- 
tory of this subject the reader is referred to the author's forthcoming 
*' Manual of the Vertebrate Paleontology of North America" ; and, for the 
more detailed work, to the author's publications in the "Final Reports of 
the United States Geological Surveys," under "Wheeler and Hayden, and 
to the "Proceedings of the American Philosophical Society of Philadel- 

The present essays are arranged (see table of contents) into four series, 
as follows : First, on General Evolution ; second, on the Structural Evidences 
of Evolution ; tliird, on Mechanical Evolution ; fourth, on Metaphysical Evo- 
lution. In the first series the author's earlier essays are arranged. The 
general principles are here laid down or foreshadowed. The essays of the 


succeeding sections are occupied with the demonstration of these and other 
generalizations, so far as practicable. In each of the sections some essays 
will be found to be more, and others less, adapted to popular use. It 
is believed that the general reader can select a sufficient number of articles 
of minimum technicality to convey to his or her mind a sufficient idea 
of the views set forth. In Part I, articles first, fourth, and sixth are of 
this character. In Part II, the first, second, and third essays are the 
least technical. In Part III, the first article is the most popular, although 
the others are essential to an understauding of the doctrine of mechani- 
cal evolution. In Part IV, all are sufficiently popular for the reader who 
has some knowledge of mental science. 

A historical synopsis of the essays may be now given. The attempt is 
made to point out the aim of each, with an indication of what may have 
been new in its contents. They are taken up in the order of date of pub- 
lication : 

II. The Origin of Genera. From the "Proceedings of the Philadel- 
phia Academy of Natural Sciences" for October, 1868, and published sepa- 
rately by the author early in 1869. In this essay the following doctrines 
were taught : 

First, that development of new characters has been accomplished by an 
acceleration or retardation in the growth of the parts changed. This was 
demonstrated by reference to a class of facts, some of which were new, which 
gave ground for the establishment of the new doctrine. 

Second, that oi exact parallelism between the adult of one individual or 
set of individuals, and a transitional stage of one or more other individuals. 
This doctrine is distinct from that of inexact parallelism which had already 
been stated by von Baer. And that this law expresses the origin of gen- 
era and higher groups, because — 

Third, they can only be distinguished l)y single characters when all their 
representatives come to be known. 

Fourth, that genera and various other groups have descended, not from 
a single generalized genus, etc., of the same group, but from corresponding 
genera of one or more other groups. This was called the doctrine of 
homologous groups. 

Fifth, the doctrine that these homologous groups belong to different 
geological periods, and. 

Sixth, to different geographical areas, which, therefore, in some in- 
stances, are. 

Seventh, related to each other in a successional way like the epochs of 
geological time. 

Of these doctrines it may be observed that the first and second are now 
the common property of evolutionists, and are recognized everywhere as 
matter of fact. The names which I selected to express them have, however, 
only come into partial use. The author beHeves that, although the doctrine 
was vaguely shadowed out in the minds of students prior to the publication 
of this essay, it had not previously been clearly expressed, nor been reduced 


to a demonstration. Of the truth of the doctrine the author is more 
than ever convinced, and he believes that paleontological discovery has 
demonstrated it in many instances, and that other demonstrations will fol- 
low. The fourth proposition (that of homologous groups) is now held 
as a hypothesis explaining the phylogeny of various groups of animals. 
For the descent of one homologous group from another, the term poly- 
phyletic has been coined. It remains to be seen whether the doctrine 
is of universal application or not. That homologous groups belong to 
different geological horizons, as stated under the fifth head, has been 
frequently demonstrated since the publication of the essay. That the sixth 
proposition is true in a certain number of cases is well known, and it 
follows that the seventh proposition is also true in those cases. The 
latter hypothesis, which was originally advanced by Prof. Agassiz, is, how- 
ever, only partially true, and the advance of paleontological study has not 
demonstrated that it has had a very wide application in geological time. 

A proposition which was made prominent in this essay was, that the 
prevalence of non-adaptive characters, in animals, proves the inadequacy of 
hypotheses which ascribe the survival of types to their superior adaptation 
to their environment. Numerous facts of this kind undoubtedly indicate 
little or no activity of a selective agency in nature, and do point to the 
existence of an especial developmental force acting by a direct influence on 
growth. The action of this force is the acceleration and retardation ap- 
pealed to in this paper. The force itself was not distinguished until the 
publication of the essay entitled " The Method of Creation " (No. V), where 
it was named growth-force, or bathmism. The energetic action of this force 
accounts for the origin of characters, whether adaptive or non-adaptive, the 
former diftering from the latter in an intelligent direction, which adapts 
them to the environment. The numerous adaptive characters of animals 
had by that time engaged the attention of the author, and he found that they 
are even more numerous than the non-adaptive. Some of the latter were ac- 
counted for on the theory of the " complementary location of growth-force." 

IV. The Hypothesis of Evolution, Phtsioal and Metaphysical. 
" Lippincott's Magazine," Philadelphia, 1870 ; reprinted by Charles C. Chat- 
field & Co. New Haven, 1870. 

This essay embraces a popular exposition of the principles maintained in 
the essay entitled the " Origin of Genera," with some conclusions derived 
from the general facts of anthropology. To this were added some facts in 
the evolution of human physiognomy and human character, which had not 
been previously thrown into harmony witli the laws already set forth. Un- 
fortunately, the author attempted to correlate these again with the theories 
of some theologians, and, in some instances, without success. A few 
paragraphs have been stricken from this part of the essay, and others are 
allowed to remain as illustrations of far-reaching hypotheses resting on 
little information. 

V. The Method of Creation of Organic Types. From the "Pro- 
ceedings of the American Philosophical Society," December, 1871; repub- 

viii PREFACE. 

lished by McCiilla & Stavely the same year. Eead before the American 
Association for the Advancement of Science, at Detroit, August 27, 1871. 
Received the Walker prize of the Boston Society of Natural History. 
In this essay were added to the preceding, the following hypotheses : 

1. The law of repetitive addition, in which the structures of animals 
were shown to have originated from simple repetitions of identical ele- 

2. The existence of an especial force which exhibits itself in the growth 
of organic beings, which was called growth-force, or bathmism. 

3. That development consists in the location of this energy at certain 
parts of the organism. 

4. That this location was accomplished by use or effort, modifying and 
being modified by the environment; or the doctrine of kinetogenesis. 

5. That the location of this energy at one point causes its abstraction 
from other points, producing "complementary diminution" of force at the 

6. That the location of this energy, so as to produce the progressive 
change called evolution, is due to an influence called " grade influence." 

7. That inheritance is a transmission of this form of energy, which builds 
in precise accord with the sources from which it is derived, 

8. That this " grade influence " is an expression of the intelligence of 
the animal, which adapts the possessor to the environment by an " intel- 
ligent selection." 

9. An attempt to account for the origin of " mimetic analogy " by 
"maternal impressions." 

On these propositions, the following comments may be made : First, 
the law of repetitive addition is much like the law of rhythm previously pro- 
posed by Herbert Spencer.* Second, the force of growth, or bathmism, 
had already been called constructive force by Carpenter, who, however, 
did not treat of its evolutionary or " grade " characteristics. That such 
force exists there can be no doubt at the present time, but it may be that 
its varied aspects should each be considered a separate species of force (i. e., 
energy). Third, the relations of the energetic and static conditions of this 
force were considered, but were not sufficiently followed out to be clear. 
It is hoped that greater clearness has been attained by the omission of 
a few paragraphs and the insertion of an explanatory foot-note. 

Fourth, that the location of this energy is due to the influence of use 
and effort. The doctrine of the development of parts of living beings by 
use, and their loss by disuse, is well known to have been put forth by 
Lamarck in 1809, who devotes one of the longest chapters (No. YII) of his 
" Philosophie Zoologique " to its discussion. He did not, however, include 
the element of effort^ prior to the appearance of any rudiment of an organ, 
in his hypothesis, which was proposed, so far as I know, for the first time 
in the present essay. The doctrine of use and disuse has been sustained 

* "Principles of Biology." 


by Spencer in his " Principles of Biology " as respects the effect of motion 
on structure in general,* and in the particular case of the origin of verte- 
■ braa.t Fifth, the complementary development of parts had also been 
pointed out by Herbert Spencer, J 

Seventh, the explanation of inheritance by the transmission of the type 
of growth-force possessed by one generation to another. This doctrine was 
subsequently announced by Haeckel, under the name of perigenesis,* 
and is the only good hypothesis yet proposed for the explanation of this 
phenomenon. Eighth, the theory of "intelligent selection," or the agency 
of the intelligence of a living being in directing its movements, and there- 
fore its growth, although a plain and necessary consequence of the " law of 
use and effort," had not been, so far as I am aware, announced prior to 
the publication of this paper. This important theory at once opened the 
way for an investigation of the general relations of mind to evolution, which 
involved the question of the origin and development of mind itself. These 
questions were more fully discussed in the papers of Part IV, on " Metaphys- 
ical Evolution." Ninth, the origin of mimetic analogy. The explanation 
offered is almost necessary, if the doctrine of the influence of effort on struct- 
ural growth be true. 

I. EvoLTJTioN AND ITS CONSEQUENCES. From the " Penn Monthly Maga- 
zine," Philadelphia, for May, July, and August, 1872. 

This is a popular exposition, with elaboration, of the doctrines contained 
in the preceding essays. The evolution of mind is more fully stated, the 
hypothesis adopted being that proposed by Spencer in his " Principles of 
Psychology," published in 1855. 

VII. The Homologies and Origin of the Types of Molae Teeth 
OF the Mammalia Eduoabilia. From the " Journal of the Academy of 
Natural Sciences," Philadelphia, March 30, 1874. 

The object of this paper was to show that the various more or less com- 
plex types of molar teeth displayed by the Ungulate Mammalia are referable 
to modifications of a primitive quaditubercular type, from which they were 
supposed to have been descended. The histories and homologies of the 
carnivorous dentition were not included in this piiper. In order to com- 
plete the subject, I have inserted brief notes of the conclusions I have since 
attained in this field : first, as to the type of inferior sectorial teeth, in 1875 ; 
and, second, as to the superior molars, in 1883. 

At the end of the paper a similar comparison between the feet of the 
same type of mammals is made, and general conclusions reached in the fol- 
lowing language : " I trust that I have made it sufficiently obvious that the 
primitive genera of this division of mammals [Mammalia Educabilia = Un- 
guiculata and Ungulata sensu lata] must have been bunodonts with penta- 
dactyl plantigrade feet." 

* Vol. ii, p. 167. f Vol. ii, p. 195. J " Principles of Biology." 

* Sec Piydcr, "American Naturalist," January, 1879. 


The nearest approaches to a similar anticipation on the part of other 
naturalists, which I have been able to find, refer to the number of toes only 
and are of restricted application. Thus Kowalevsky remarks (" Monographie 
der Gattung Anthracotherium, Palaeontographica," xxii, p. 1452) : " So we 
can assume a tetradactyl foot as our point of departure, although it can 
not have the least effect on the result in case the original ungulate foot 
should have been pentadactv]. If I have set out with a tetradactyl foot 
it is simply because I wish to adhere so far as possible to facts." This was 
written August, 1873, but how soon thereafter it was printed I do not know. 
I did not meet with it until at least a year after the publication of my paper 
of March, 1874, cited. Secondly, Marsh, in writing on the genealogy of 
the horses (" xVmerican Journal of Science and Arts," March, 1874, p. 257), 
says: "A still older ancestor [of the horse], possibly in the Cretaceoui=, 
doubtless had five toes on each foot, the typical number in mammals." My 
paper was published during the same month as the above; but I communi- 
cated the substance of the generalization in question to the Philadelphia 
Academy the day it was read, November 18, 1873, which was published in 
the "Proceedings of the Society, " January 18, 1874, p. 2. 

XVIII. Consciousness in Evolution. From the " Penn Monthly Maga- 
zine," Philadelphia, July, 1875. 

In this paper the doctrine of intelligent selection is analyzed, and the 
problem reduced to its essential — the relations of consciousness to matter. 
The doctrine of the origin of reflex and automatic acts from conscious states, 
or archaesthetism, is here first proposed. From the characters of proto- 
plasm the inference is derived that that substance is not necessarily the only 
one capable of supporting consciousness. The author is not aware of any 
previous attempt to render these propositions probable. 

VIII. The Relation of Man to the Tertiaey Mammalia. From the 
" Penn Monthly Magazine," December, 1875. Read before the American 
Association for the Advancement of Science, at Detroit. 

The fact that the hard tissues, and probably the digestive system, of man, 
are constructed on the type of the Mammalia of the early Eocene period 
is here pointed out for the first time. 

III. The Theory of Evolution. Remarks made before the Academy 
of Natural Sciences of Philadelphia, February 22, 1876, and published in the 
"Proceedings of the Society," 1876, p. 15. 

These remarks exhibit the correspondence between the evolutionary 
systems of Haeckel and of the writer, and combine them into a symmetrical 

XXI. The Origin of the Will. From the "Penn Monthly Magazine," 
Philadelphia, June, 1877. 

In this paper the attempt is made to render the existence of freedom of 
will probable by a process of argument, and also to demonstrate its exist- 
ence by another kind of argument. As is well known, there are two op- 
posed doctrines respecting this important question. One of these, which 
has by far the larger number of adherent?, is that the human mind embraces 


among its powers a freedom of will, or spontaneity in action. The other 
view is, that there is no such power, but that the actions are merely the 
necessary result of the strongest pressure of the strongest inducement or 
motive. The doctrine of evolution is known to lend support to the latter 
doctrine. In the present paper the attempt is made to prove that free will 
is a new power which supervenes on the process of evolution. This is done 
by assuming the existence of a class of acts for which the term altruistic is 
retained, which, undoubtedly, would require freedom for their perform- 
ance. The only question here is, whether there be any such class of acts as 
are defined under the above name in this essay. If tliere be no such class 
of acts, the demonstration based on it falls to the ground ; and the author 
is not at present sure whether there be such a class of acts or not. 

The argument by which freedom of will is rendered probable is not 
open to any serious objection, and rests on the necessity for action which 
sometimes arises in cases where there is no experience or knowledge to serve 
as a determining motive or power. These cases are supposed to involve 
moral questions. The doctrine is then intermediate between the two oppos- 
ing ones which have long divided the world of thought.* It permits of the 
development of a free will in previously automatic beings, as a phenomenon 
superposed on mental evolution. The argument demonstrates nothing more 
than that freedom is possible; a conclusion which is, however, important, 
since it shows that the position of the determinists is not impregnable. 

XII. The Relation of Animal Motion to Animal Evolution, From 
" The American Naturalist," January, 1878. Read before the American 
Association for the Advancement of Science, at Nashville, August, 1877. 

The effects of the actions of animals on their structure are considered, 
as in previous papers, and especial attention is paid to the influence of ani- 
mals in the changes they produce in their environment.! 

XIV. The Oeigin of the Specialized Teeth of the Caenitoea. From 
" The American Naturalist," March, 1879. 

The mechanical reasons for the changes in the dentition of carnivorous 
mammals during geologic time are pointed out for the first time. 

VI. A Review ok the Modern Doctrine of Evolution. From " The 
American Naturalist," March and April, 1880. A lecture delivered before 
the California Academy of Sciences, October 27, 1879. It is a general 
synopsis of views presented in preceding papers. 

XV. On the Origin of the Foot-Structuee of the Ungulates. 
From "The American Naturalist," April, 1881. 

This essay embraces an explanation of the cause of the diminution of the 
number of digits in the diplarthrous ungulate mammals; of the reasons 
why some are even- and some odd-toed ; and of the origin of some of the 

* This view is adopted by President Xoah Porter in one of his latest metaphysi- 
cal works. 

f A synopsis of the relations of animals to their environment is given by Spen- 
cer, " Principles of Biologj'," vol. i, p. 466. 


articulations of the tarsus. These explanations, so far as based on paleonto- 
logical grounds, were new at the time. 

XVI. The Effect of Impact and Steains on the Feet of Mammalia. 
From " The American Naturalist," July, 1881. 

The origin of the structures of all the articulations of the limbs of all the 
Mammalia are explained as the effects of impacts and strains. The demon- 
stration is based largely on paleontological evidence, and is new. 

XIX. On Aechaesthetism. From " The American Naturalist," June, 

This doctrine is discussed and illustrated on the basis laid down in the 
essay " Consciousness in Evolution," and a classification of theories of crea- 
tion is presented. 

IX. The Developmental Significance of Human Physiognomy. From 
"The American Naturalist," June, 1883. 

In this paper suggestions presented in Art. I Y, entitled " The Hypothe- 
sis of Evolution, Physical and Metaphysical," are developed, and the physical 
significance of the form-characters of men in general are considered. Noth- 
ing except reference to a few leading points of the subject had been pub- 
lished prior to this paper, so far as the author has been able to discover. In 
connection with a paper on the " Evolutionary Significance of Human Char- 
acter," a foundation was laid for a scientific physiognomy. 

X. The Evidence for Evolution in the History of the Extinct 
Mammalia. A lecture delivered before the American Association for the 
Advancement of Science, at Minneapolis, August, 1883. 

In this paper are collected the evidences of descent displayed by the 
Mammalia (and in one instance by the Batrachia), as derived from the pale- 
ontological researches of the author. These had been in some points fore- 
shadowed in the author's memoir on the homologies and origin of the struct- 
ure of the molar teeth in the Mammalia Educabilia in 1874, which were 
here shown to have been realized by subsequent discovery, and a number 
of other evidences added. Restatements of the laws of kinetogenesis, and 
of the origin of morals, were made. 

XVII. The Evolutionary Significance of Human Character. From 
the " American Naturalist," September, 1883. 

The characters of the adult mind are compared with those of the child, 
and with those of the lower animals, and the direction of their evolution 
pointed out. Most of the propositions contained in this paper were new at 
the time of its publication. 

XIII. The Tritubercular Type of Molar Teeth in the Mammalia. 
From the proceedings of the American Philosophical Society, 1883, page 
324;* published in advance in the "Paleontological Bulletin," No. 37, 
January 2, 1884. 

The origin of the ungulate molar tooth had already been traced to a 
quadritubercular type in paper No. VII (March and January, 1874). The 

* Not published until 1884. 

PREFACE. xiii 

present paper shows that this type in the upper jaw is a derivative of a tri- 
tubercular type, while that of the lower jaw is a derivative of a quinquetu- 
bercular type, or a tritubercular type With a heel, which may support two 
additional tubercles. The tritubercular type was again traced to the sim- 
ple cone. This generalization was new at the time of publication. 

XX. Catagenesis. Vice-presidential address delivered before the bio- 
logical seciion of the American Association for the Advancement of Sci- 
ence, Philadelphia, September 4, 1884. 

The hypothesis of catagenesis which is put forth in this paper teaches 
that primitive energy was and is conscious, and that all unconscious forms 
of energy, whether " vital " or non-vital, have been derived from it by a 
process of retrograde metamorphosis. The first stage of this retrogression 
is the loss of consciousness, or cryptopnoy. Evidence for this kind of meta- 
morphosis is derived from every-day experience, and from the designed 
character of automatic acts. That a form of energy is conscious is inferred 
from the nature of designed conscious acts of animals. The author had not 
met with any scientific statement of this theory prior to the preparation of 
this lecture. 

XI. The Evoltition of the Veetkbeata, Peogeesstve and Reteo- 
GEESsivE. From the " American Naturalist," February, March, and April, 

This paper sets forth the results of paleontological investigation of the 
Vertebrata, in a series of phylogenies. These are, first, the phylogeny 
of the classes ; then the special phylogenies of their contents or of the 
orders. Here are introduced the newly-discovered relations of the Anti- 
archa and the Ichthyotomi to the fish-like vertebrates, and of the thero- 
morphous reptiles to the Mammalia. Also, the ancestral relation of the 
Theromorpha to most other reptiles, and of the Condylarthra to the placental 
Mammalia, and to man. Many of the other results set forth in this essay 
are derived from the paleontological researches of the author. Some of 
them, especially the lemurine (condylarthrous) ancestry of the placental 
Mammalia, had been anticipated on theoretical grounds by Haeckel in his 
" History of Creation " (" Schopfungsgeschichte "). Haeckel was very 
general in his proposition, and did not anticipate the details of the demon- 
stration. My investigations enabled me to produce these, which bring out 
in a striking manner the sagacity of Prof. Haeckel. I consider further the 
question of degeneracy, and the significance of the phylogeny with refer- 
ence to this subject is pointed out. 

In conclusion, it may be said that the principal object which the author 
set before him, in the studies here recorded, has been tbe discovery of 
the laws of variation, or of the "Origin of the Fittest." These essays 
express the light which he has been able to obtain on this difiicult question 
up to the present time. The results could be better and more briefly pre- 
sented in a systematic form, but the author reserves this for a future occa- 



I. — Evolution and its Consequences 

II. — The Origin of Genera 

III. — The Theory of Evolution 

IV. — The Hypothesis of Evolution, Physical and Metaphysical 

V. — The Method of Creation of Organic Forms . 
VI. — Re^^iew of the Modern Doctrine of Evolution 





VII. — The Homologies and Origin of the Types of Molar Teeth of the 

Mammalia Educabilia . .241 

VIII. — The Relation of Man to the Tertiary Mammalia . . . 268 

IX. — The Developmental Significance of Human Physiognomy . . 281 
X. — The Evidence for Evolution in the History of the Extinct 

Mammalia 294 

XI. — The Evolution of the Vertedrata, Progressive and Retrogres- 
sive 314 


XII. — The Relation of Animal Motion to Animal Evolution 
XIII. — On the Trituberculate Tooth in the Mammalia . 
XIV. — The Origin of the Specialized Teeth of the Carnivora 

XV. — The Origin of the Foot Structures of the Ungulates 
XVI. — The Effect of Impacts and Strains on the Feet of Mammalia 





XVII. — The Evolutionary Significance of Human Characteu . . 378 

XVIII. — Consciousness in Evolution 3dO 

XIX. — Arch^sthetism 405 

XX. — Catagenesis 422 

XXI. — The Origin of the Will . • . . . , , . . 437 




I. Figures and Diagrams of the Circulatory Centers of Vertebrata. Copied 

from Gegenbaur and His, mostly enlarged 60 

II and Ila. Figures of Lizards of the families Iguanidae and Agamidaa 

compared 97 

III and Ilia. Mimetic analogy in the colors and patterns in snakes of dif- 

ferent genera and species ........ 105 

IV and V. Series of Crania of Different Families of Tailless Batrachia 

showing similar stages of development. Original . . . 220, 221 

Explanation 222 

VI. Succession of Modifications of Feet of Diplarthrous Ungulata. Original 271 
VII. Succession of Dental Forms, mostly of Ungulata. From Gaudry, Wort- 
man, and Cope . . . 275 

VIII. Uintatherium rornutum Cope, restored, one twenty-seventh natural size. 

From Cope, Marsh, and Osborn 277 

IX. Anaptomorphus and Homo ; Cranium, Brain, and Teeth. Original, ex- 
cept Figs. 8 and 9 from Allen 279 

X. Esequibo Indians. From photographs by Endlich .... 286 

XI. The Wrestler. From the Vatican . . .... 289 

XII. Venus of the Capitol 292 

XIII. Phenacodus primwvus Cope, Skeleton as found in matrix, one seventh 

natural size. Original 300 

XIV. Brains of Extinct Mammalia. Original, except Fig. 2 from Marsh . 308 
XV. Bidonius mirabilis, Skull Profile. Original 338 

XVI. Didonius mirabilifs, Skull from below, one half the mandible removed. 339 
XVII. Phenacodus vortmani, Skeleton as found in Matrix, two ninths natural 

size. Original 345 

XVIII. Hy(Bnodon horridus Leidy, Skull one half natural size. From Lcidy . 364 

Wo on- Cuts. 


1. Diagram illustrating acceleration and retardation 10 

2. Diagram illustrating relations of genera of batrachia anura . . . 80 
3 to 6. Diagrams illustrating development of genera of batrachia anura . 81 
7. Same as Fig. 1 176 





8. Sternum and adjacent parts of ScapMopus holbrooki 
9.' Sternum of Tadpole of Rana temporaria . 

10. Sternum of adult Rana temporaria 

11. Metacarpus, carpus, and distal extremity of radius of Po'ebrotherium vilsoni 

12. The same, less radius, with first phalanges of Procamelus Occident alls 

13. Skull of Protolahis transmontanus 

14. '^^wW oi Procamelus occidentalls . ... 

15. Tooth of Globicephalus 

16. Tooih. of Jaculus hudsonicus .... 

17. 'iooih oi Lcptochcerus spcctabilis. From Leidy . 

18. Tooth of Rhinocerus, milk superior molar . 

19. 1ooi\\ oi Achcenodon insolens .... 

20. Tooth of Hippopotamus amphibius. From Cuvier 

21. Tooth of Hyopotamus velaunus. From Blainville 
■ 2 i. Tooth of Hyojjotamus americanus. From Leidy 

23. Tooth of Procamelus 7-obustus. From Leidy 

24. Tooth of Merychyus major. From Leidy . 

25. Tooth of Tapirus 

26. Tooth of Mastodon angustidens. From Cuvier 

27. Tooth of JIastodon americanus. From Cuvier 

28. Tooth of Dinotherium. From Cuvier 

29. Tooth of Elcphas indicus. From Cuvier . 

30. Tooth of Microsyops elegans. From Leidy 
81. Tooth oi Jlyopsodus paulus. From Leidy . 

32. Tooth of Palceosyops kcvidens. From Leidy 

33. Tooth of Anchippodus ripariv^. From Leidy 

34. Tooth of Palceosyops vallidens. From Leidy 

35. Tooth of Palceotherium. From Cuvier 

36. Tooth of Hipposyus. From Leidy 

37. Tooth of Hipposyus more worn. From Leidy 

38. Tooth of Hypohippus. From Leidy . 

39. Tooth of Equus, superior molar. From Leidy 

40. Tooth of Eqims, inferior molar. From Leidy 

41. Tooth of Bathmodon radians 

42. Tooth of Uintatherium robusium, superior molar. From Leidy 

43. Tooth of Uintatherium 7'obustum, inferior molar. From Leidy 

44. Periplychus rhabdodon, part of posterior foot 

45. Coryphodon elcpJianiopus, right fore foot, one third natural size 

46. Coryphodon elephantopus, right posterior foot . 

47. Phenacodus primeevus, right anterior foot, one third natural size, 

48. Phenacodus primcBvus, left posterior foot, one third natural size 

49. Homo sapiens, left anterior foot (hand), one third natural size . 

50. Homo sapiens, left posterior foot, one third natural size 
61. Phcnacodus primeevus Cope, skull, one third natural size, from below 

52. Simia satyrus, section of skull of adult 

52a. Simia satyrus, section of skull of young 

53. Homo sapiens, infant at term .....•• 


. 217 
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54. Homo sapiens, portrait of girl at five years 

55. Homo sapiens, portrait of same at seventeen years 

56. Homo sapiens, portrait of Luchatze negro woman 

57. Homo sapiens, portrait of Lucliatze negro woman 

58. Homo sapiens, portrait of Satanta, chief of the Kiowa Indians of North 

America ............ 

59. An Australian native .......... 

60. Eryops megaceplialus, a batrachian of the Permian epoch of Texas ; vertebral 

column ............. 

61. Sleeve of coat, showing folds 

62. Bothriolepis canadensis, from above ........ 

6.3. Chelyosoma maclovianum, a tunicate from Point Barrow, Alaska, from above 
64. Stypolophus whidce, skull and dentition, displaying the tritubercular type of 


Q5.~ Deltatherium fundaminis, skull, profile 

66. Oxycena lupina, jaws and teeth . 

67. ProceJums julieni, skull. From Filhol 

68. Dinidis cyclops, skull 

69. Smilodon ncogceus, skull 

70. Coryphodon elephantopus, hind foot above 

71. Aphelops megalodus, hind tarsus and metatarsus, from front and above 

72. Proiohippus sejundus, posterior foot, front 

73. Poebrotherium lahiatum, posterior foot, front 

74. Poebrotherium vilsoni, carpus, metacarpus, and end of radius, from front 

75. Amblydonus sinosus, a creodont ; distal end of tibia 

76. Oxyeena morsitans, a creodont ; distal end of tibia 

77. Arclicdurus debilis, an extinct cat; distal end of tibia, 

78. Nimravus gomphodus, a cat ; femur . 

79. Procamelus occidcntalis, part of fore foot 

80. Cosoryx furcatus, part of fore foot 

81. Poebrotherium vilsoni, part of fore foot 

with astraaralus 









The broad theory of evolution includes the theories of devel- 
opment of the solar system and its members, as expressed by the 
nebular hypothesis ; the theory of development of life by molecu- 
lar movements consequent upon certain combinations of non-living 
matter ; and, lastly, the theory of development of the species of 
animals and plants by descent, the later from the earlier, with 
accompanying change of form and character. It attempts noth- 
ing less than a history of the process of creation of the universe, 
so far as we can behold it ; and is, therefore, an attempt to formu- 
late the plans and thoughts of tlie Author of that universe. 
Hence, it is not surprising that it excites the interest of the best 
of men, especially as it is one of the results of the efforts of a 
class of these, crowning many centuries of labor and thought. 

The object of the present essay is to discuss familiarly the 
latter of these theories of evolution, viz., that respecting the 
species of animals and plants. As all are aware, this mode of 
accounting for the creation of organized beings has attained 
especial prominence at the present time, and possesses more of 
interest to most readers because of its explanation of our own 
origin. Moreover, it rests on more indubitable evidence than the 
two other theories. The constitution and arrangement of the 
members of the solar system point to their origin by derivation 
from primal masses of vaporous matter through the mutual opera- 
tion of the ordinary laws of attraction and motion. The position- 
ing is precisely as it should be hud such process taken i>lace, but 
the process itself, that is, the change from type to type of celes* 

tial body, has not been observed. 


The Cease is far different with the theory as regards organized 
or living beings. Not only are the mutual relations of animals 
and plants to each other such as should have resulted from a de- 
scent or development, but the changes from type to type have 
been actually observed, and in sufficient number to place the 
hypothesis on the basis of ascertained fact, as referring to a cer- 
tain range of objects — say, in the case of the animal kingdom, to 
individuals distinguished by structural characters vrithin the range 
of each of the three to six great primary divisions or " branches." 

There are two totally distinct propositions involved in this 
question, which are confounded by the general public, and not 
unfrequently by students and writers on it. These are, first, the 
evidence which seems to prove that this evolution has taken place ; 
secondly, the evidence as to the nature of the laws of its progress. 
A want of constant distinction between these views of the case 
has greatly obscured it and injured the evidence on one side or 
the other. 

The evidence in favor of evolution is abundant, and is cited 
in fragments by various contemporary writers, foremost among 
whom, both in time and abundance of waitings, comes Charles 

Much less has been done in explanation of the laws of evo- 
lution. Darwin and his immediate followers have brought out 
the law of "natural selection''; Spencer has endeavored to ex- 
press them in terms of force ; while Hyatt, Cope, Packard, and 
others have advanced the law of "acceleration and retardation." 

In earlier days, when information was distributed slowly and 
books were few, it was long before any new truth or doctrine 
reached the majority of people, still less was adopted by the rul- 
ing classes. But the modern theory of evolution has been spread 
everywhere with unexampled rapidity, thanks to our means of 
printing and transportation. It has met with remarkably rapid 
acceptance by those best qualified to judge of its merits, viz., the 
zoologists and botanists, while probably a majority of the public, 
in this region at least, profess to reject it. This inconsistency is 
due to two principal causes. In the first place, Darwin's demon- 
stration contained in the " Origin of Species" extends little fur- 
ther than as stated in the title of his work. He proves little more 
than that species of the same genus or other restricted groups 
have had a common origin ; and, further, his theory of natural 
selection is to the plainest understanding incomplete as an ex- 


planation of their " origin," as its author indeed freely allows. 
Besides, the unscientific world is particularly unreasonable on 
one point. Little knowing the slow steps and laborious effort by 
which any general truth is reached, they find in incompleteness 
ground of condemnation of the whole. Science is glad if she can 
prove that the earth stands on an elephant, and gladder if she can 
demonstrate that the elephant stands on a turtle ; but, if she can 
not show the support of the turtle, she is not discouraged, but 
labors patiently, trusting that the future of discovery will justify 
the experience of the past. 

If, then, some of the people find Mr. Darwin's argument in- 
complete, or in some points weak, it may be answered, so do the 
student classes, who, nevertheless, believe it. This is largely be- 
cause Darwin's facts and thoughts repeat a vast multiplicity of 
experiences of every student, which are of as much significance 
as those cited by him, and which only required a courageous 
officer to marshal them into line, a mighty host, conquering and 
to conquer. These will slowly find their way into print, some in 
one country and some in another. 


As to the truth of the theory, the proof has been stated in 
more than one form. The first and simplest, and essentially the 
central argument of Darwin, is as follows : 

In every family or larger group of animals and plants there 
exists one or more genera in which the species present an aggre- 
gation of specific intensity of form ; that is, that species become 
more and more closely related, and finally varieties of single spe- j 
eies have to be admitted for the sake of obtaining a systematic/ 
definition or " diagnosis," which will apply to all the individuals. 
These varieties are frequently as well marked as the nearly-related 
species, so far as amount of difference is concerned, the distinc- 
tion between the two cases being that in the varieties there is a 
gradation from one to the other ; in the species, none. Neverthe- 
less, T)eTween some of the varieti^ transitions mav be of rare oc- 
currence, and in the case of the *' species " an intermediate indi- 
vidual or two may occasionally be found. Thus it is that differ- 
ences, called varietal and specific, are distinguished by degree 
only, and not in kind, and are, therefore, the results of the opera- 
tion of uniform laws. Yet, according to the old theory, the varie- 
ties have a common origin, and the species an independent one ! 


To find exampbs of wliat is asserted, it is only necessary tp refer 
to the diagnostic tables and keys of the best and most honest 
zoologists and botanists. It is true that these 'diagnoses are dry 
reading to the non-professional, yet they embrace nearly all that is 
of value in this part of biological science, and must be mastered in 
some department before the student is in possession of the means 
of forming an opinion. The neglect to do this explains why it is 
that, after all that has been written and said about protean spe- 
cies, etc., the subject should be so little understood. 

It is true that in but few of these cases have the varieties been 
seen to be bred from common parents, a circumstance entirely 
owing to the difficulties of observation. The reasoning derived 
from the relations of differences appears to be conclusive as to 
their common origin, unless we are prepared to adopt the oppo- 
site view, that the varieties have originated separately. As these 
avowedly grade into individual variations, we must at once be led 
to believe that individuals have been created independently — a 
manifest absurdity. 

But variations in the same brood have been found among wild 
animals ; for example, both the red and gray varieties of the little 
horned owl {Scops asio) have been taken from the same nest. 

As further examples of gradation between species and variety, 
found in nature, I only have to select those genera most numerous 
in species, and best studied. Among birds, Corvus, Empidonax, 
Biiteo, Falco, etc. Reptiles, Eutaenia, Aiiolis, Lycodoji, Naja, 
Caudlsona, Elaps, Oxyhrropus, etc. Batrachia, Rana, Hyla, 
Clioroj)Mlus, Borhorocoetes, Amblystoma, Spelerpes, etc. Fishes, 
Ptycliostomus, Plecostomus, Amiurus, Salmo, Perca, and many 

In all these groups of species, or '^'genera," it is impossible in 
some cases to determine what is variety and what species. This 
is notoriously the case with the salmon and trout {Salmo), for one 
of the greatest opponents of close division of species. Dr. Gilnther, 
of London, thought himself necessitated, a very few years ago, to 
name and describe half a dozen new species of trout from the 
lakes of the British Islands, and, from being a stanch supporter 
of the old view of distinct creations, was completely converted to 

Such is one of the views which has forced conviction on the 
minds of thoroughly honest men who were not only desirous of 
knowing the truth, but were in many cases brought over from a 


position of strong opposition. But the earnest objector says, you 
have not after all shown me any real transitions from species to 
species ; until that is done your development is but a supposition. 

The all-sufficient answer to this statement is to be found in 
the imperfection of our system of classification. Thus, if we first 
assume, with the anti-developmentalist, that varieties have a com- 
mon parentage, and species distinct ones, when intermediate forms 
connecting so-called species are discovered, we must confess our- 
selves in error, and admit that the forms supposed to have had 
a different origin really had a common one. Such intermediate 
forms really establish the connection between species, but the 
question is begged at once by asserting unity of species, and, 
therefore, of origin, so soon as the intermediate form is found ; 
for, as before observed, it is not degree, but constancy of distinc- 
tion, which establishes the species of the zoological systems. 
Transitions between species are constantly discovered in existing 
animals ; when numerous in individuals, the more diverse forms 
are regarded as "aberrant"; when few, the extremes become 
"varieties," and it is only necessary to destroy the annectant 
forms altogether to leave two or more species. As the whole of a 
variable species generally has wide geographical range, the vari- 
eties coinciding with sub-areas, the submergence, or other change 
in the intervenmg surface, would destroy connecting forms, and 
naturally produce the isolated species. 

Formerly naturalists sometimes did this in their studies. A 
zoologist known to fame once pointed out to me some trouble- 
some specimens which set his attempts at definition of certain 
species at defiance. "These," said he, "are the kind that I 
throw out of the window." Naturalists having abandoned throw- 
ing puzzling forms out of the window, the result of more honest 
study is a belief in evolution by nine tenths of them. 

But, says the inquirer again, your variations and transitions 
are but a drop in the ocean of well-distinguished species, classes, 
etc. The permanent distinction of species is matter of every-day 
observation ; your examples of changes are few and far between, 
and utterly insufficient for your purpose. 

It is true that the cases of transition, intermediate forms, or 
diversity in the brood, observed and cited by naturalists in proof of 
evolution, are few compared with the number of well-defined, iso- 
lated species, genera, etc., known ; though far more numerous 
than the book-student of natural history is apt to discover. But 


although the origin of most species by descent has not been ob- 
served, every one knows the worthlessness of argument based on a 
negative. Unless these cases exhibit opposing evidence of a posi- 
tive character, they are absolutely silent witnesses. 

He who cites them against evolution commits the error of the 
native of the Green Isle who testified at a murder trial. "Al- 
though the prosecuting attorney brought three witnesses to swear 
positively that they saw the murder committed, I could produce 
thirty who swore they did not see it done ! " 

By the inductive process of reasoning we transfer the unknown 
to the known, for it is the key of knowledge. It rests upon the 
invariability of Nature's operations under identical circumstances, 
and for its application merely demands that analysis and com- 
parison shall fix that the nature of that of which something is 
unknown is identical with that of which the same thing is 
known. We then with certainty refer that which is known as 
an attribute of that object of which the same quality had been 
jjreviously unknown. The following form exhibits its applica- 
tion to the question of evolution. As preliminary facts it may 
be assumed that : 

1. Many species are composed of identical elemental parts 
which present minor differences. 

2. Some of these differences have been seen to originate spon- 
taneously from parents which did not possess them, or, what is the 
same thing, are known to exist in individuals whose parentage is 
identical with others which do not possess them. 

3. The gradation of differences of the same elemental parts is 
one of degree only, and not of kind. 

4. Induction. — Therefore all such differences have originated 
by a modification in growth, or have made their appearance with- 
out transmission in descent. 


In discussing this point, new evidence in favor of develop- 
ment must be produced, and some statements of the history of 
the opinion made. 

The laws which are expressed by all that we find of structure 
in animals are four, viz. : 

1. Homology. — This means that animals are composed of cor- 
responding parts ;' that the variations of an original and fixed 
number of elements constitute their only differences. A jiart 


large in one animal may be small in another, Or vice versa ; or 
complex in one and simple in another. The analysis of animals 
with skeletons or vertebrata has yielded several hundred original 
elements, out of which the 28,000 included species are con- 
structed. Different this from the inorganic world, which can 
only claim about sixty-two elemental substances. The study of 
homologies is thus an extended one, and is far from complete at 
the present day. 

2. Successional Relation. — This expresses the fact that species 
naturally arrange themselves into series in consequence of a mathe- 
matical order of excess and deficiency in some feature or features. 
Thus species with three toes naturally intervene between those 
with one and four toes. So with the number of chambers of the 
heart, of segments of the body, the skeleton, etc. There are 
greater series and lesser series, and mistakes are easily made by 
taking the one for the other. 

3. Parallelism. — This states that while all animals in their 
embryonic and later growth pass through a number of stages and 
conditions, some traverse more and others traverse fewer stages ; 
and that, as the stages are nearly the same for both, those which 
accomplish less resemble or are parallel with the young of those 
which accomplish more. This is the broad statement, and is 
qualified by the details. 

4. Teleology. — This is the law of adaptation so much dwelt upon 
by the old writers, and admired in its exhibitions by men gener- 
ally. It includes the many cases of fitness of a structure for its 
special use, and expresses broadly the general adaptations of an 
animal to its home and habits. 

Of course, these laws must be all laws of evolution, if evolution 
be true. And such they are ; but this is far from being perceived 
by some students, for some of them were in abeyance or neglect 
prior to the stimulus to thought caused by the appearance of the 
"Origin of Species." 

Forty or fifty years ago Germany had been flooded with the 
writings of the " physiophilosophs." Oken and Goethe had ob- 
tained glimpses of the wonderful " unity in variety " expressed 
by the laws of homology. The latter saw vertebrse in the seg- 
ments of the skull, and leaves in the floral organs of plants. He 
had found the magic wand, and many were the harmonious visions 
that delighted the laborious toilers among old bones and dusty 
skins ; the patient haruspices saw omens in the intestines of birds 


and snakes, and he whose hours were spent over his lens ceased 
to be a mere wondermonger. But fashion is fashion, and always 
ends in absurdity and stagnation. The physiophilosophs became 
extravagant, and mistook superficial appearances for realities. 
They did not dream how misleading some of the resemblances 
between different elements, for example, of the skeleton may be, 
and for once German students did not analyze exhaustively. Cu- 
vier laughed at these seekers for beauty, and confounded the true 
and the untrue in one condemnation. But the best men labored 
forward ; errors began to be exposed, and soon a reaction set in. 
Another extreme followed, and the school of Miiller, at Berlin, 
denied the meaning of these resemblances and ceased to see any- 
thing but differences. Minute and thorough investigation flour- 
ished in their hands, and the modern school of German anatomists 
has seen no superiors. So the theory of evolution found Berlin. 
The disfavor in which physiophilosophy was held secured to evo- 
lution a cold welcome, and it has been for Jena and other univer- 
sities to give it its true impetus in Germany. 

So it has been with the law of parallelism. Some of the 
physiophilosophs declared it, stating that the inferior animals 
were merely the repressed conditions of the higher. This view 
was taught by some men in high position in France. Their state- 
ments were, however, too broad and uncritical. The father of 
embryology, von Baer, of Koenigsberg, declared there was "heine 
Rede" of such theory, and Lereboullet stated " that it is founded 
on false and deceptive appearances." Even Professor Agassiz in 
our day has asserted that no embryonic animal is ever the same as 
the adult of another, though he also once informed the writer that 
the embryology of two nearly related species had never been studied 
and compared. This was subsequently done by Professor Hyatt, 
of Salem, for the nautilus and ammonite division of mollusks, and 
at about the same time by the writer, for many species of our na- 
tive frogs and salamanders, and the result has been a complete 
clearing up of the confusion about parallelism, and the clear estab- 
lishment of the law. 

The results attained are these : The smaller the number of 
structural characters which separate the two species when adult, 
the more nearly will the less complete of the series be identical 
with an incomplete stage of the higher species. As we compare 
species which are more and more different, the more necessarily 
must we confine the assertion of parallelism to single parts of the 


animals, and less to the whole animal. When we reach species as 
far removed as man and a shark, which are separated by the ex- 
tent of the series of vertebrated animals, we can only say that the 
infant man is identical in its numerous origins of the arteries from 
the heart, and in the cartilaginous skeletal tissue, with the class of 
sharks, and in but few other respects. But the importance of this 
consideration must be seen from the fact that it is on single char- 
acters of this Mnd that the divisio7is of the zoologist depend. 
Hence we can say truly that one order is identical with an incom- 
plete stage of another order, though the si^ecies of the one may 
never at the present time bear the same relation in their entirety 
to the species of the other. Still more frequently can we say that 
such a genus is the same in character as a stage passed by the next 
higher genus ; but when we can say this of species, then their dis- 
tinction is almost gone. It will then depend on the opinion of 
the naturalist as to whether the repressed characters are perma- 
nent or not. Parallelism is then reduced to this definition : that 
each separate character of every kind, which we find in a species, 
represents a more or less complete stage of the fullest growth of 
which the character appears to be capable. In proportion as those 
characters in one species are contrasted with those of another by 
reason of their number, by so much must we confine our compari- 
son to the characters alone, and the divisions they represent ; but 
when the contrast is reduced by reason of the fewness of differing 
characters, so much the more truly can we say that the one species 
is really a suppressed or incomplete form of the other. The denial 
of this principle by the authorities cited has been in consequence 
of this relation having been assigned to orders and classes, when 
the statement should have been confined to single characters; and 
divisions characterized by them. There seems, however, to have 
been a want of exercise of the classifying quality or power of "ab- 
straction " of the mind on the part of the objectors. This faculty 
seems to be by no means so common as one would expect, judging 
from the systematic ideas of many. 

To explain by a few examples selected at random : First, of 
species characters, I may cite the fact that all deer arc spotted 
When young, and that some of the species of eastern and southern 
Asia retain the spotted coloration throughout life. All salaman- 
ders are uniform, often olive during a larval stage ; some species, 
and some individuals of other species, retain the color in maturity. 
To take a genus character : all the deer in the second year develop 


their first horn, which is unbranched and small, or a " spike," A 
genus of deer inhabiting South America never develops anything 
else. To take a character of higher grade : tbe exogenous plants 
usually present net- veined leaves, but the first pair, or those of 
the plumule, are of much simpler structure, being often parallel- 
veined ; for example, the cucumbers and squashes. Now, the en- 
dogens usually produce nothing else than parallel-veined leaves, and 
no case is known where a plant bearing this type of leaf exhibits 
the net-veined type as its earliest growth. 

But what do these facts mean ? As in growth the genus char- 
acters usually appear last, I will suppose a case where one genus 
represents truly, or is identical with, the incomplete stage of an- 
other one. 

In A we have four species whose growth attains a given point, 
a certain number of stages having been passed prior to its termi- 

nation, or maturity. In B we have an- 

^^^ A other series of four (the number a mat- 
ter of no importance), which, during the 
period of growth, can not be distin- 
h guished by any common, i. e., generic 
■ character, from the individuals of group 

■ A, but whose growth has only attained 

^^' ' to a point short of that reached by those 

of group A at maturity. Here we have a parallelism, but no true 
evidence of descent. But if we now find a set of individuals be- 
longing to one species (or, still better, the individuals of a single 
brood), and therefore held to have had a common origin or parent- 
age, which present differences among themselves of the cliaracter 
in question, we have gained a point. "VVe know in this case that 
the individuals, a, have attained to the completeness of character 
presented by group A, while others, b, of the same parentage have 
only attained to the structure of those of group B. It is perfectly 
obvious that the individuals of the first part of the family have 
grown further, and, therefore, in one sense faster, than those of 
group b. If the parents were like the individuals of the more 
completely grown, then the offspring which did not attain that 
completeness may be said to have been retarded in their devel- 
opment. If, on the other liand, the parents were like those less 
fully grown, then the offspring which have added something 
have been accelerated in their development. I claim that a con- 
sideration of the uniformity of nature's processes, or inductive 


reasoning, requires me to believe that the groups of species, that 
is, groups A and B, are also derived from common parents, and 
the more advanced have been accelerated or the less advanced re- 
tarded, as the case may have been with regard to the parents. 

This is not an imaginary case, but a true representation of 
many cases which have come under notice. I can not repeat 
them here, but refer to the original memoirs, where they may be 

This is a simple statement of the law of " acceleration and re- 
tardation " of some American naturalists, which probably expresses 
better than any other the " manner of evolution," the proposition 
with which we started. 

Hyatt thus defines it as seen in a group of ammonites which 
he studied : " The young of higher species are thus constantly 
accelerating their development, and reducing to a more and more 
embryonic condition the stages of growth corresponding to the 
adult periods of preceding or lower species." f 

This form of demonstration of evolution is of far wider appli- 
cation than that which I first brought forward. J In the latter 
case the induction may be limited to a certain range of variation, 
but the present law is as extensive as the organic world ; that is, 
the "positioning" essential to it is found everywhere, from the 
lowest to the highest, and in characters from the least to the 
greatest in import. 

Let an application be made to the origin of the human species. 
It is scarcely necessary to point out at the start the fact, univer- 
sally admitted by anatomists, that man and monkeys belong to 
the same order of Mammalia, and differ in those minor charac- 
ters, generally used to define a "family" in zoology. 

Now, these differences are as follows : In man we have the 
large head with prominent forehead and short jaws ; short canine 
teeth without interruption behind (above) ; short arms, and thumb 

* See " Origin of Genera, and Method of Creation," Naturalists' Agency, Salem, 
Massachusetts ; or McCalla & Stavely, 237 Dock Street, Philadelphia. 

f "On the Parallelism between Stai;es'in the Individual and those in the Group 
of the Tetrabranchiata." "Boston Society of Natural History," 4to, 1866, p. 203. 

I It is quite misunderstood by Darwin, as will be sufficiently evident from the 
following quotation from the last edition of his " Origin of Species," 1872, p. 149: 
" There is another possible mode of transition, namely, through the acceleration or 
retardation of the period of reproduction. This has lately been insisted on by 
Prof. Cope and others in the United States." This has only been dwelt on as 
accounting for a very minor grade of differences seen in race and sex. 


of hind foot not opposable. In monkeys we have the reverse of 
all these characters. But what do we see in young monkeys ? A 
head and brain as large relatively to the body as in man ; a facial 
angle quite as large as in many men, with jaws not more promi- 
nent than in some races ; the arms not longer than in the long-armed 
races of men, that is, a little beyond half way along the femur. 
These observations are made on a half-grown Cebus apella, from 
Brazil, a member of a group more remote from men than are the 
Old World apes, yet with an unusually large facial angle. At 
this age of the individual the distinctive characters are therefore 
those of homo, with the exception of the opposable thumb of the 
hind foot, and the longer canine tooth ; nevertheless, the canine 
tooth is shorter in the young than in the adult. 

Now, in the light of various cases observed, where members of 
the same species or brood are found at adult age to differ in the 
number of immature characters they possess, we may conclude 
that man originated in the following way : that is, by a delay or 
retardation in growth of the body and fore limbs as compared with 
the head ; retardation of the jaws as compared with the brain 
case, and retardation in the protrusion of the canine teeth. The 
precise process as regards the hinder thumb remains obscure, but 
it is probably a very simple matter. The proportions of the 
young Cehus apella enable it to walk on the hind limbs with great 
facility, and it does so much more frequently than an adult C. 
capucinus with which it is confined.* 

The "retardation" in the growth of the jaws still progresses. 
Some of our dentists have observed that the last (3d) molar teeth 
(wisdom teeth) are in natives of the United States very liable to 
imperfect growth or suppression, and to a degree entirely unknown 
among savage or even many civilized races. The same suppres- 
sion has been observed in the outer pair of superior incisors. 
This is not only owing to a reduction in the size of the arches of 
the jaws, but to successively prolonged delay in tlie appearance of 
the teeth. In the same way men, and the man-like apes, have 
fewer teeth than the lower monkeys, and these again fewer than 
the ordinary Mammalia, and this reduction has proceeded m rela- 
tion to an enlargement of the upper part of the head and of the 

The cause of development may be next considered, and under 

* The same relations of man to the anthropoid apes have been dwelt upon by 
Prof. C. Vogt. 


this head may be discussed the natural selection of Wallace and 
Darwin and other propositions of similar import. 

" Eetardatiou " continued terminates in extinction. Examples 
of this result are common ; among the best known are those of 
the atrophy of the organs of sight in animals inhabiting caves. It 
is asserted that the young of both the blind crawfish ( Orconedes 
pellucidus) and the lesser blind fish {TijphlicMhijs suUerraneus) 
of the Mammoth Cave possess eyes. If these statements be accu- 
rate, we have here an example of what is known to occur else- 
where, for instance, in the whalebone whales. In a foetal stage 
these animals possess rudimental teeth like those of many other 
Cetacea when adult, which are subsequently absorbed. So also 
with the foetal ox ; the upper incisor teeth appear in a rudimental 
condition, but are very early removed. The disappearance of the 
eyes is regarded by Dr. Packard, with reason, as evidence of the 
descent of the blind forms from those with visual organs. I would 
suggest that the process of reduction illustrates the law of ''re- 
tardation " accompanied by another phenomenon. "Where charac- 
ters which appear latest in embryonic history are lost, we have 
simple retardation, that is, the animal in successive generations 
fails to grow up to the highest point of completion, falling farther 
and farther back, thus presenting an increasingly slower growth 
in the special direction in question. Where, as in the presence of 
eyes, we have a character early assumed in embryonic life, retarda- 
tion presents a somewhat different phase. Each successive genera- 
tion, it is true, fails to come up to the completeness of its prede- 
cessor at maturity, and thus exhibits "retardation," but this 
process of reduction of rate of growth is followed by its termina- 
tion in the part long before growth has ceased in other organs. 
This is an exaggeration of retardation, and means the early termi- 
nation of the process of force-conversion, which has been previ- 
ously diminishing steadily in activity. 

Thus the eyes of the Orconedes probably exhibited for a time 
at maturity the incomplete character now found in the young, a 
retarded growth continuing to adult age, before the termination 
of growth was withdrawn by degrees to earlier stages. With this 
early termination of growth came the phase of atrophy, the in- 
complete organ being removed and its materials transferred to 
other parts through the greater activity of " growth-force." Thus, 
for the reduction of organs, we have "retardation " ; bat for their 
extinction, "retardation and atrophy." 



1. Inductive Reasoning. 

In the present investigation we are endeavoring to discover 
new principles, not to apply old ones. The work is similar to 
that which occupied Newton in his investigation of the law of 
attraction or gravitation. The jirocess by which we arrive at 
general truths rests on the consideration of a sufficient number 
of observed facts, and the determined qualities which are common 
to all we regard as a law. This process requires for its proper 
conduct a careful analysis and discrimination of the nature of the 
objects considered ; otherwise fallacy will result. As exact analy- 
sis is not always observed by the average mind, this inductive 
reasoning is not always successfully employed by it, nor under- 
stood when presented by others. In the deductive process it is 
more at home. With an ascertained principle given, as some- 
thing like a staff for the mind to lean on, its application is not so 
difficult ; but to such a mind induction presents an appearance 
of uncertainty and eVen of confusion, and these will certainly 
exist until order is evoked by the first step — classification. The 
theory of evolution has thus been charged with confusion, as 
though it asserted that which oyertiirew the order of nature. But 
the confusion only exists in the mind of such critics. The order 
of the creation is one of the foundation facts, and thus enters 
the inductive argument as one of its elements. That conclu- 
sion which is consistent with this order can not be regarded as its 



2. On Natural Selection. 

In endeavoring to assign a cause for the existence of the pecul- 
iar structures which define the divisions among animals, Messrs. 
Wallace and Darwin have proposed the now well-known law of 
natural selection. This states, that, inasmuch as slight variations 
appear continually in all species, it is evident that some will be 
more beneficial to the animal than others, in its exertions to sup- 
ply itself with food, protect itself from enemies, the weather, etc. 
It then asserts that those whose peculiarities are beneficial will 
excel those less favored, in the successful use of their powers, and 
hence will live better, grow better, and increase more rapidly. 
That by the force of numbers, if not by direct conflict, they will 
ultimately supersede the weaker and destroy or drive them away. 


Then, as there are many fields of action and possibilities of ob- 
taining support in the world, that the weaker will first be driven 
to adopt such of these as their peculiarities may adapt them for, 
or not exclude them from. Thus all the positions in the world's 
economy are filled and the surplus destroyed. This is styled by 
Spencer the ^'survival of the fittest" ; an expression both com- 
prehensive and exact. 

This doctrine is no doubt a true one, and has regulated the 
preservation of the variations of species, and assigned them their 
locations in the economy of nature. It was natural that this great 
law should have been brought out by such men as Darwin and 
AYallace, who are bv nature much more of observers of life in the 
field, or out-door physiologists, than they are (or were) anatomists 
and embryologists. Their wi'itings in their chosen field of the 
mutual relations of living beings in their search and struggle for 
means of existence are admirable, and almost unique, especially 
some of those of Darwin. 

It is to be observed, however, that they both (especially Dar- 
win) start with the variations observed. This is assumed at the 
outset, and necessarily so, for " selection " requires alternatives, 
and these are the product of variation. Great obscurity has arisen 
from the supposition that natural selection can originate anything, 
and the obscurity has not been lessened by the assertion often made 
that these variations are due to inheritance ! What is inheritance 
but repetition of characters possessed by some (no matter what) 
ancestor; and if so, where did that ancestor obtain the peculiarity? 
The origin of variation is thus only thrown upon an earlier period. 

Another reason why natural selection fails to account for the 
structures of many organic beings is the fact that in expressing 
" the survival of the fittest " it requires that the structures pre- 
served should be especially useful to their possessors. Now, per- 
haps half of all the peculiarities of the parts of animals (and 
probably of plants) are of no use to their possessors, or not more 
useful to them than many other existing structures would have 
been. It fails to account for many characters which express the 
relations of homology and parnllelism, and is almost confined in 
its exhibitions to features which express teleology. This objection 
has been insisted on by Kolliker, the writer, and by Mivart ; and 
now Huxley, while defending Darwinism proper against the last- 
named author, says that "wliat the hypothesis of evolution wants 
is a good theory of variation.'" 


Plainly enough, tlien, nothing ever originated by natural se- 
lection, and as the present essay relates to the origin of types, lit- 
tle space can be given to its discussion ; for natural selection, 
important though it be, is but half the question, and indeed the 
lesser half. It is to the great causative forces as are the gutters 
and channels which conduct the water in comiiarison with the 
pump and the man who pumps it. 

3. On Teleology. 

Two classes of structures have been alluded to : those which 
are useful to an animal, and those which are not useful ; or the 
adaptive and non-adaptive. Nothing is better known than that 
animals are well adapted to their situations in the world, and for 
their needs as to supplying themselves with food, etc. Some part 
of every species is so constructed as to enable it to live under con- 
ditions where most other kinds of animals would perish. Thus 
the sea-rangers, among birds, as the great albatross, etc., possess 
long and pointed wings ; while those that live in thickets or 
under cover have short, round ones, as grouse, woodcock, etc. 
Even our sparrows — those that love the bu.shes and swamps, as 
the song-sparrow {Melospiza melodia) — have short, rounded wings, 
while those that haunt trees have them sharper and pointed, as 
the chipping and tree sparrow {Spizella socialis, pusilla, etc.). 
Water-frogs have their feet webbed ; land-frogs have small or no 
webs ; while tree-toads possess sucker-like expansions of the ends 
of the toes, which secrete a glutinous fluid, by which they adhere 
to the trunks and leaves of trees. Finally, frogs that burrow have 
one or more of the bones of the base of the hind foot {tarsus) 
modified into a projecting blade, like that of a shovel ; and, as they 
squat down, they literally sit into the ground, and are soon out 
of sight in the hole which they dig with these busy trowels. 

Cave insects have long and delicate antennse and limbs, ex- 
ceeding those of their out-door relations by much. Moreover, 
their usual lack of eyes is a clear case of the reverse of adaptation, 
i. e., the absence of an organ where not needed. 

Less attention has been directed to the non-adaptive charac- 
ters, yet they are as numerous as the adaptive. I do not include 
under this head useless organs or parts only, but also those which 
are useful, but whose peculiarities do not relate to that use as 
advantageous to it. 

Notable examj^les of this kind are to be found in the characters 


which distinguish all of the higher groups of animals and of plants 
among themselves. It is easier to ask than to answer what advan- 
tages the mammalian skeleton possesses over the reptilian that it 
should have superseded it. What end was served by aborting 
the coracoid bone, which in reptiles supports the shoulder-joint 
from behind, answering to the ischium of the pelvis ? I do not 
know how to answer this question on a teleological basis, although 
it involves one of the principal characters of the class of reptiles. 
What mechanical end was gained by withdrawing the rib-bones 
of two cranial segments into the cavity of the ear, to become the 
hammer, anvil, and stirrup of the organ of hearing ? * Was it to 
perfect the auditory faculty ? Scarcely ; for birds possess as re- 
fined and as musical an ear as any mammals, and appear to be 
superior to them in discriminating power, yet in them the ham- 
mer is the basal element of the lower jaw, and the anvil supports 
it, being entirely outside the cranial walls. See again one ground 
of distinction between reptiles and batrachians. The base of the 
brain-case in the former consists of an axis of bony segments de- 
veloped in the primordial cartilage, while in the batrachian it is a 
single bony plate, formed by deposit in the membrane which origi- 
nally bounded this cartilage. Who can assign any advantage of the 
one type above the other which can be looked upon as m any way 
related to the external needs of the animals of those classes ? 

Another example may be found in the ankle-joints of reptiles, 
birds, and mammals. In the first two the hinge is between the 
first and second series of tarsal bones ; in the mammals, between 
the bones of the lower leg and the first row of tarsal bones. Some- 
thing besides the superior mechanical advantages of the latter has 
given it predominance over the former. 

To turn to the nautilus and ammonite types of Mollusca, we 
observe beautiful illustrations of all the laws already stated. As 
is well known, these shells have their tubular cavity divided by 
transverse partitions. In the nautilus these unite with the outer 
wall by a plain angle, but in various genera which lead toward the 
ammonites this margin becomes complicated. This results from 
an excessive growth of the peripheral part- of the partition or sep- 
tum, so that in order to confine it to the same space of contact it 
must be folded. This plication takes place in a symmetrical man- 
ner. The folded edge in Aturia forms a tongue-like loop on each 

* The homoloj^ics here expressed have been rendered improbable by late investi- 
gation. The argument is, however, not affected. 


side, on the outer surface. In Goniatites a fold is added on the 
back. In successive genera other main folds are added, the last 
appearing nearest the center of the coil. These then become 
complicated by suboi'dinate undulations which in the more com- 
plex forms become the axes of a double row of new lobes and folds, 
the whole presenting symmetrical lobate outlines of much com- 
plexity and beauty. 

But another series of changes accompanies those of the septa, 
and are entirely independent of them. These relate to the vari- 
ous degrees of winding of the shell. The early form with simple 
sejDta ( OrtJioceras) was straight, but others which succeeded began 
to turn their shell-making round an axis, thus commencing a par- 
tial coil. In some the coil was very open ; in others it began 
close, and then ceased, the shell finishing straight. Others after 
such a course began to wind again, while some made a single turn 
near the middle. The most remote from the starting-point {Ain- 
monites, sp.) made a tight and complete flat coil, while some, 
whose septa remained simple, did the same {Nautilus). 

The direct uses of these various forms of septum and coil are 
simply inexplicable, and that one of them was any '^ fitter" to 
"survive" than another, by virtue of its usefulness, is for me 
more than doubtful. 

I am tempted to continue this theme, for it might be pro- 
longed indefinitely by any one familiar with the details of ana- 
tomical structure, but I will only repeat that the illustrations 
would be drawn chiefly from the characters of the classes, orders, 
families, and other higher groups. 

It is not difficult to believe, in the case of the useful structures 
first cited, that the law of natural selection has had much, prob- 
ably everything, to do with the preservation of the animals pos- 
sessing them in the various localities to which they are adapted. 
But that it has had opportunity to direct the lines of progress in 
the second series is not likely. That it had nothing to do with 
the oriffin of either, is certain. 


4. On Groiuth- Force. 

Every change by complication of structure is hy addition; 
every simplification is by subtraction. Every addition is a matter 
of growth, which is carried on by a process of nutrition. The in- 
quiry respecting the origin of new forms centers itself at once on 
the history of growth and the influences affecting it. 


If, as I suppose, these additions, either adaptivo or non-adapt- 
ive, be produced by an acceleration * of growth, it is evident that 
the same immediate cause of that increase must be potent in both 
cases. That one of the "forces" is concerned in growth as well 
as in all the active animal and vegetable processes, is obvious to 
those who have carefully observed it. The fact that growth, like 
work, requires food for its progress and continuance, is reason 
enough for suspecting the existence of a force, and in some cases 
the relation between this force and other known forces may be 

Prof. Henry pointed out these facts many years ago, and 
illustrated them by observations on the growth of the potato and 
of the egg. The starch of the former, a complex *' organic" 
chemical compound, weighs much more than the young shoot 
of cellulose, etc., into which it is converted by the process of 
growth, so that a portion of the substance of the tuber has evi- 
dently escaped in some other direction. This was found to be 
carbonic-acid gas and water, derived from the slow combustion of 
the starch, which, in thus "running down " from the complex or- 
ganic state, to the more simple inorganic comjiounds, evolves an 
amount of force precisely equal in amount to the chemical force 
(chemism) requisite to bind together the elements in the new and 
complex substance cellulose, f 

It is well known that substances differ in their capacities for 
giving out different kinds of force. This, of course, means their 
capacity for converting one kind of force into another. Thus, if 
glass be rubbed with silk, the motion is converted into electricity, 
while, if it be rubbed by the hand, heat is the principal result. 
In some cases chemical force, set free by decomposition, is con- 
verted into light ; in others, heat ; in others, to electricity, often- 
er to several at once. But one substance, so far as known, pos- 
sesses the power of converting this chemical force or heat into 
growth-activity, and that is the material out of which the living 
parts of animals and plants are composed. This is a protein, a 
compound of carbon, oxygen, and nitrogen .in the order of rela- 
tive quantity, with a smaller proportion of hydrogen, the whole 
being often associated with still smaller quantities of sulphur 

* For the definition of this term see first article, in May number of " Penn 
Monthly." (Antea, p. 11.) 

f "Agricultural Report of Patent Office," 1857. 


and phosphorus. In its mechanical aspect, as the material out 
of which structures and tissues are made, it is called protoplasm. 

This substance exhibits two different phenomena of force- 
energy, viz., motion and groiuth. Motion is exhibited by con- 
traction and expansion, but which is the active state and which 
the passive state is matter of question. Some physiologists regard 
''contractility" as the energetic state. Eadcliffe believes that 
extension is the energetic condition, and contraction a rebound 
or discharge of the extending force. He finds dead protoplasm 
to be a dielectric, and believes that in life each muscular fibrilla 
acts like a Leyden jar. It has been demonstrated that the outer 
layer of the sheath of a muscular fibrilla is positively electrified in 
life, while the cut extremities are negative, and it is shown by 
Radcliffe that the inner side of the sheath becomes negatively 
electrified by induction. The attraction of the opposite electrici- 
ties on opposite sides of the sheath compresses and elongates it, 
thus, according to his theory, producing muscular extension. The 
nervous cells and tubes he believes to act in the same way ; the 
difference being that the walls and sheaths are in a state which 
prevents compression and extension. The phenomena of mus- 
cular extension and nervous tension he believes to be terminated 
by a discharge of the force, such as takes place in electrical fishes, 
but in much smaller quantity. Thus motive force resides as a 
form of electricity in protoplasm, and in highly organized animals 
is specialized into neurism. 

As to growth-force, all its exhibitions may be reduced to cell- 
division, cell-nutrition, and cell-origin. Cell-division exhibits 
two prominent varieties. In both the cell nucleus first divides ; 
in the ordinary mode, the cell-wall contracts at opposite points, 
forming approaching plications, which, when they meet, divide 
the cell. In the other mode or proliferation, the divisions of the 
nuclei approach the cell- walls, which bulge opposite to them, 
forming diverticula, which isolate themselves by opposing con- 
tractions at the base, which meet as before. The nature of the 
force thus displayed is as yet only speculative, and its demonstra- 
tion will result largely from observation on cell-origin from homo- 
geneous protoplasm. Eadcliffe suggests an ingenious theory. 
He supposes that the protoplasm acquires an external layer differ- 
entiated from the internal mass by exposure to and contact with 
external substances, and that the electricity generated in the in- 
terior is distributed on the under surface of this stratum. That 


this induces opposite electricity on the external surface, which, as 
in the muscular cell, causes compression, and therefore extension 
of the stratum. This extends itself beyond its contents, which 
may be attenuated, filling the space, or contracting, forms the 

This view will not, however, account for nucleus and cell- 
division, which are the subsequent and principal exhibitions of 
growth-force. Perhaps the following suggestions may throw some 
light on it. Should a polar tendency appear in the nucleus, were 
the protoplasm of the proper viscidity, the poles being of like 
electric name, would tend to separate by repulsion, thus forming 
the hour-glass shape so well known, and afterward division. 
This nucleus division would inevitably be followed by division 
of the cell-wall, if its inner face were electrified in opposition to 
the nucleus. For the wall being attracted toward it equally all 
round, the separation of the two nuclei would be followed by an 
incurvature of the walls opposite the interval between the nuclei, 
in order that each should maintain a position equidistant from 
its center. Further divergence would result in the completion 
of the cell-wall of each, apart from the other. This process 
would be supported by nutrition of the cell, which proceeds by 
the passage through tlie cell-wall to the nucleus, of additional 
protoi>lasm from the blood. Of course, the prime question is as 
to whether polarity can appear in the nucleus. That growth 
is first polar appears probable on consideration of the globular 
and discoidal forms of the lower animals, and that this principle 
lies at the basis of the growth of the higher is rendered equally 
probable by the phenomena of symmetry of different kinds, as 
bilateral, anteroposterior, etc. The electricity supplied to the 
outer sheaths of muscular fibrillge is, according to Dubois Eey- 
mond, positive. That covering the surface of the nucleus must 
be thought to be positive also, if it be effected in opposition to the 
inner wall of the cell-wall, which is known to be negative by ex- 
periment. But in that case it would be difficult to perceive why 
it should not fill the cell by attraction to the wall. If, on the 
other hand, it be a generator of negative electricity, it would re- 
tain its integrity and induce a temporary change in the wall. 
The transmission of protoplasm through the cell-wall to the 
nucleus would produce an accumulation of electricity to be dis- 
charged in extension, or a disturbance of equilibrium, to be fol- 
lowed by polarity and division ; but the conditions under which 


these results would appear are, of course, unknown. The me- 
chanical arrangement and condition of the parts would have 
much to do with it. 

We are, however, here in the arcana of life, and the forms of 
law which rise before the mental vision are but as the statues of 
Memnon that greet the toiler on the river of mysteries ; they loom 
upon its banks in twilight,, and the when, the how, and the where- 
fore remain unanswered. But the river of Africa is yielding, her 
secrets, and, though the life that she nourishes may be the last she 
will give up, it is no less surely promised to the patient inquirer. 

A great advance toward an explanation of the operation of this 
growth-force was made in the demonstration of the fact that its 
highest exhibitions are confined to the multiplication of cells by 
division of pre-existent ones, by contraction of their nuclei and 
walls in lines which finally meet. 

The construction of additional parts consists solely of this cell- 
growth, but the character of the result is, of course, dependent on 
the position at which this addition takes place. It may be at the 
terminus of a limb to add another toe, or on the wall of an artery 
to add a valve. It may be in the brain to add a band of fibers, 
or on the edge of a muscle to extend its width. 

That tissues are made of cells of original or altered shape, sepa- 
rate or confluent (flown together) is well known. That the ar- 
rangement of tissues into organs is due to the direction of this 
multiplication is also true. Thus a gland is a collection of folli- 
cles, each of which is a bagging of a plane tissue. This bagging 
is an exaggerated convexity, which is occasioned mechanically by 
excess of cell-growth at one spot on a uniform surface. Solid 
parts are all formed, in the first i7istance, of simple segments. 
These are parts produced in a straight rod by excessive elongation 
or growth ; the process being as before, the division of cells and 
distribution of homogeneous protein between them. All this is 
derived from the study of homologies combined with embryology, 
and the result is wonderful, and simplifies at once our ideas of the 
action of the growth-force. It is mainly a repetition of cell-divis- 
ion, the result as to structure being entirely dependent on the 
influences which locate its activity and regulate its amount. 

Now, its amount will depend on the capacity of the existing 
organism to convert heat, etc., into it ; and the form, as to tissue, 
etc., in which it appears, depends no doubt on the complexity of 
the machines or organs of which the organism is composed. In 


the case of the higher organisms we have muscle, converting the 
results of nutrition into muscle ; skin and nails making more skin, 
etc. ; brain making more brain ; bone making more bone. 

The prime question is the cause of the location of growth- 
force. Experiments on this point are greatly needed, and in their 
absence it will be necessary to take a wide survey of facts. 

A given animal organism can only convert a given amount of 
force, and that capacity must remain uniform so long as the 
machine or structure remains the same. If, however, an addition 
to its work is developed in one quarter, a subtraction from some 
other region must take place if the whole amount remain the same. 
When, then, a useful organ is added, subtraction from some less 
important locality must result, and, as a consequence, the latter 
must become still less prominent in the general economy. Hence, 
the development of the useful class of organs already cited must 
always be accompanied by a corresponding disappearance of use- 
less ones. This would be by reduction or retardation. But, in 
the case of the complex folds of the margins of the septa in the 
ammonite, useless parts are added by acceleration. Here a gradual 
increase in the amount of growth-force must be believed in. 

The representation of simple growth-force, i. e., the result of 
bathmism, not specially located, is seen in general addition to size. 
In domestication careful feeding, associated with protection against 
all exhausting exposure or exertion, tends to this increase of size. 
This is well known to be the case in hogs and cattle and animals 
of quiet and easy life. The reverse conditions, as poor food, ex- 
posure, and disproportionate exertion, reduce the size ; witness the 
Maryland breed of cattle, and the semi-wild hogs of the Southern 
States. This matter is, however, nicely balanced with the pro- 
duction of motion, for if the latter be excessive, or the supply of 
material for consumption be insufficient, growth-force must be 
evolved in less amount. 

It will be necessary here to state that the supply for the con- 
version of all the forces of the body is derived from the nutriment 
as circulated in the blood. 

But the condition of plethora of growth-force is also the one 
highly favorable for the appearance of variations of structure, or 
the location of growth-force in new places. Domesticated animals 
are notorious for this variation, while the still more numerous ex- 
amples of " protean " species in nature are always predominant 
forms, abundant in individuals and widely spread. For example. 


the wolf, the red fox, the red-tailed hawk, the garter-snake, the 
tiger, salamander, etc. 

That the variability depends on a peculiar condition of the ani- 
mals themselyes, and not on domestication, excepting in so far as 
it produces these conditions, is plain, not only from the above 
facts, but from those observed in domestication. It is well known 
that while pigeons, fowls, cattle, dogs, etc., are variable, or ''pro- 
tean," the peafowl (Pavo) has maintained its specific characters 
with great accuracy during a period of domestication as long as 
that of the other species named. The same may be said of the 
guinea {Numida) and the turkey {Meleagris). These facts show 
that domestication is only a remote cause of variability. 

5. 071 the Location of Growth-Force. 

With the fact of increase of general growth-force before us, 
have we any others which can guide us in fixing on a cause for its 
special location ? It is plain that the useful additions which have 
constituted certain genera, families, orders, etc., what they are, 
must have been produced as a consequence of the existence of a 
need for them ; or, on the other hand, being created first, they 
must have sought for use, and found it. But what are the rela- 
tive chances of truth for these two propositions ? In the second 
case, admitting evolution as proved (see Part I), we perceive that 
an almost infinite chance exists against any usual amount of 
variation, as observed, producing a structure which shall be fit to 
survive in consequence of its superior adaptation to external cir- 
cumstances. It would be incredible that a blind or undirected 
variation should not fail in a vast majority of instances to produce 
a single case of the beautiful adaptation to means and ends which 
we see so abundantly around us. The amount of attempt, failure, 
and consequent destruction, would be preposterously large, and 
in no wise consistent with the facts of teleology as we behold 

What of the opposite view ? We have in its support the well- 
known facts of [determination of nutritive fluid during use of 
partsAnot only for supplying fuel for the motions of use, but also 
for growth-force and material for the increase in bulk of the part 
used. Who has not remarked the large size of the hands of the 
laborer, and of the nails of the working-woman ? Who can not 
remember some of the countless examples of certain modifications 
of form being associated with special excellence of use of the parts 


in different races of the same species of individuals of common 
parentage, showing that they must have grown with the history 
of those races ? Who does not know the short, wide jaws of the 
bull-dog, with their oblique teeth, produced by the expansion of 
the zygomata to accommodate the huge temporal muscles so neces- 
sary for maintaining a firm hold of its enemy. Then the long and 
full nose of the hound, and its more extended turbinate bones — 
how closely is this connected with its developed scent ; while the 
light muscular forms of the greyhound are undoubtedly necessary 
to its well-known speed. If it be said that these variations have 
not resulted in a single change of structure worthy of note by a 
systematist, we can point to the Japanese dog, where the excessive 
reduction of the Jaws anteriorly has resulted in a total loss of some 
of the premolars and molars. The loss of molar and incisor teeth 
from shortening of the Jaws, in the human species, has been al- 
ready noted. The number of such instances is very great, but, as 
space to enumerate them fails, it is only necessary to add that they 
are characters of high importance in a systematic sense. Their 
importance will be more readily conceded in remembering the 
proposition, already stated, that species are simply isolated varie- 
ties, and of similar origin. 

Confirmatory of this view are the facts already cited with ref- 
erence to the relation of motive to growth-force. The force in- 
volved in both being seen to be similar, perhaps identical, the 
former represents its energetic state as discharge and motion, the 
other energetic without discharge, in the growth of cells. And 
whatever determines this force to a given part of the body must 
then probably result in both of its exhibitions, dependent on the 
kind of cells which receive it. As above remarked, the conditions 
which determine the result are unknown, except that the two 
kinds of muscular cells are the only ones in which elongation is 
strongly marked. 

Another reason for believing in use as a cause of structural 
change is the manner in which the same useful structures have 
evidently appeared on totally distinct stems, as an evident adapta- 
tion to the same circumstances in which the different types have 
been equally placed. Thus the birds of prey possess the hooked, 
often toothed, beak, appropriate for tearing and destroying ani- 
mals. Their stock is the same as that of the cuckoos and parrots, 
and even of the pigeons. The butcher-birds are of the division of 
songsters, not widely removed from the thrushes, and far enough 


from the raptores, yet the same hook and dentate bill reappears in 
them, as adapted to flesh-eating habits. 

Among the reptiles, wliich were no doubt originally land ani- 
mals, and derived from batrachians, we have a large number 
adapted to swimming in the ocean, and these not all of the same 
stock. Thus the Plesiosauri are crocodilian in relationship, while 
the Pytlionomorpha of America were of the same that i^roduced 
the snake and lizard. Again, the same modification appears in the 
Cetaceans, or whale, etc., among mammals which are primarily a 
terrestrial division. 

It is a nice point of pliylogeny (or the science of genealogy) to 
ascertain whether adaptive or strictly "bathmic" (or embryonic 
grade) characters came first in a time in a given group. Among 
frogs we have four divisions. One has an embryonic mouth and 
embryonic breast-bones ; another, embryonic mouth and complete 
breast-bones ; the third, embryonic breast - bone but complete 
mouth; and the fourth, with both complete. The first is the lowest 
and probably the oldest in time ; agreeably to this supposition, it 
is distributed over the whole earth. The second is East Indian 
and African ; the third and most extensive is Australian and 
American ; while the fourth is confined to the Old World and 
North America. The second, third, and fourth divisions possess 
corresponding series of genera of different structure adapted to 
different modes of life. Some have shovels for burrowing, some 
webs for swimming, and some palettes for adhering to branches 
and leaves of trees. If these characters were first fixed, then those 
with the more perfect breast-bone and mouth are descendants of 
those with the less perfect ; if, on the other hand, the conditions 
of mouth and breast-bone were first fixed, then each division thus 
defined in its special region was modified into the subdivisions, 
each adapted to a special mode of life. I have called these parallel 
divisions "homologous groups," and probably the origin of the 
embryonic modifications has sometimes come first, and sometimes 
the adaptive structures have preceded. Nevertheless, the lowest or 
most embryonic division will often have developed its own adapt- 
ive divisions, and each of these will agree in producing descend- 
ants which have advanced in the embryonic scale, and so produce 
homologous groups. 

For these and other reasons it is concluded that the useful 
characters, defining natural divisions of animals, have been pro- 
duced by the special " location of growth-force " by use. Useless 


ones have been produced by location of growth-force without the 
influence of use, or by its subtraction, due to a disturbance of 
equilibrium, consequent on the special location elsewhere. 

But we go back to the origin of the question in investigating 
the action of growth-force undisturbed by the interference of lo- 
cating influences. This is only to be ascertained by an examina- 
tion of lower organisms in connection with the higher. A point 
that first strikes the student of higher animals is, that after he has 
proved the law of homology to be true, as regards different animals 
when compared, he further finds that the parts of the same ani- 
mal are also homologous, that is, right hand and left, front and 
behind, bottom and top are also constructed on the same plan, so 
as to be reduced to the same elemental parts. This is described 
under the names of "anteroposterior" and "bilateral symmetry," 
etc.* These laws apply to all parts of the organism, and, though 
there appear to be exceptions, these are traceable to a common 
symmetrical t}^e, the change wrought being one form of speciali- 
zation. It is not surprising then that the lower we descend in the 
scale of life the less marked is the departure from the entirely 
symmetrical disposition of parts as regards the common center. 
This is beautifully seen in the Radiata, etc., where the jelly-fish, 
the star-fish, and the sea-urchin are familiar examples. 

But these are complex compared with forms below them. The 
minute Polycystina construct shells of beautiful sculpture or 
tracery ; but, though they present many forms, they may be all 
referred as modifications, to the symmetrically-marked disk. Of 
cellular animals, Trichodiscus represents a discoidal aggregate, 
and Adinoplirys a globular mass of cells. Monas and its allies 
consist of one or several cells in globular form. 

Lastly, in the first appearance of life in the most complex ani- 
mal we have first a cell, which, then "segmenting," divides itself 
so as to become a globular mass of identical cells, arranged about 
the center. 

From the cellular animal upward the operation of addition of 
parts is then one of repetition, and that centrifugally in the case 
of bodies which are developed in all planes, or peripherally in those 
which are in one plane. 

Thus the complication of the edges of the septa of the am- 
monites is accounted for. First, the growing animal was supplied 

* See Prof. B. Wilder, in Proceed. Boston Society Nat. Hist. 


witli an excess of growth-force. The type of the preceding gen- 
eration being strictly adhered to according to the laws of inherit- 
ance, the only opportunity for its exhibition was necessarily after 
the inherited parts were completed by acceleration. The results 
could only, therefore, be exhibited on the edges of the new septa 
and free margin of the outer wall. As the older growths me- 
chanically restrained the new septa from mere extension, folding 
or plication must have resulted from the crowding of additional 
surface into the small space. This folding would take the form 
of simple branching, and then " repetition " of the process by a 
refolding of the outlines of the first fold. The edge would thus 
have the digitate or pinnately branched appearance it is known to 

Another case of folding is that of the brains of the higher 
mammals, including man. This was occasioned by excess of 
growth-force distributed to the circumference (from an inherited 
central region), exceeding in amount that of the space (skull) in 
which it was inclosed. Folding was necessary for its accommoda- 
tion in the contracted space. This is a highly useful modification. 
Another case like that of the ammonite above cited, whose use is 
not so readily determined, but which illustrates excess of growth- 
force on some other account, is that of cotyledonary leaves in some 
plants. In these cases the growth of the leaf is accelerated, re- 
quiring plication for its accommodation. 

We therefore have the two laws regulating the " location of 
growth-force " irrespective of use, viz. : 1, the centripetal or po- 
lar tendency ; 2, the peripheral tendency ; both more or less de- 
termined by the inherited central or first grown parts. 

There is, however, another element which in animals disturbs 
the symmetrical direction of growth-force besides use, and which 
precedes use, i. e., effort. Use presupposes a part to use, and a 
simple part is sufficient for its influence, so that it be usable ; but 
the first beginnings of few structures are usable. As Mivart has 
objected to natural selection, that the first rudiments of organs 
could never be sufficiently important to an animal to give it a 
preference in the struggle for existence, so it might be urged 
against the theory of use that rudiments are generally useless, 
and could not have been originated by use. 

The effect of use is, however, twofold. The contact with ob- 
jects used has some effect in stimulating nutrition, as well as the 
exertion of the muscles necessary to use. But determination of 


nutritive fluid is well known to be under the influence of nerve- 
force. How imagination stimulates secretion is seen in the famil- 
iar example of the flow of saliva in anticipation of food ; a very 
different example is the phenomenon of blushing under emotional 
stimulus. Nevertheless, it is not evident that growth can result 
with any such facility in a fully grown animal. It is thought that 
the effort becomes incorporated into the metaphysical acquisitions 
of the parent, and is inherited with other metaphysical qualities 
by the young, which during the period of growth is much more 
susceptible to modifying influences and is likely to exhibit struct- 
ural change in consequence. Certain it is that acceleration ceases 
with growth, and, as the young of animals are not in complete re- 
lation with the surrounding world, the influences controlling it 
must be inherited. This consideration renders it doubly probable 
that the results of effort on the part of the parent appear in change 
of structure in the offspring. 

Of course, immense numbers of cases of continued effort can be 
produced by the objector, in which no structural modification has 
resulted. There are various reasons why a modification should 
not take place. In the first place, the exertion of use must be 
great, habitual, and long-continued ; in the next place, abundant 
food must be at hand ; finally, growth-force must be to spare in 
the growing young, either from some less necessary part or by ex- 
cess. Now, cases are probably not rare where none can be spared 
from another part without injuring the efficiency or viability of 
the animal ; hence, all such changed individuals would perish 
through some form of natural selection or disease. 

Domesticated animals can be pointed out where effort and use 
have long been put forth in the service of man without changing 
structure. But such effort is not to be compared for a moment 
with that put forth by animals in a wild state, in seeking food or 
protection from enemies. The protection furnished by man, and 
consequent release from the struggle for existence, has reduced 
tlie chances for such variations greatly. Nevertheless, variations 
profitable to man have resulted ; witness the race-horse and carter. 

In cases where one side of the body is used in excess of the 
other, unsymmetrical development would be counteracted by the 
law of polar or centrifugal growth, all that might be acquired by 
the one side being inherited by both. Even this original sym- 
metry has, how^ever, been overcome in some types, as in the 
flounders (in the jaws and teeth as used parts). This part of 


the subject is purely hypothetical, however probable, but the as- 
pect of the discussion will be materially brightened to the reader, 
if he have previously adopted, with the author, the principle that 
evolution has been the mode of origin of the present life-forms of 
the earth. 

Eeverting now to those beings which are either in part or en- 
tirely destitute of the power of determining these movements, as 
plants, various causes present themselves as modifiers of the polar 
or centripetal activity of growth-force. In the case of a plant, the 
medium in which it grows modifies the result ; for example, the 
downward growing axis or root differs much from the upward 
aerial portion or stem. Aquatic plants, supported beneath or on 
the surface of the water, lack the strong stems and braces neces- 
sary to air-growing plants ; while of the latter, those with wealc 
stems develop tendrils and other supports. In these cases physical 
laws have been the guides of growth-force. In the case of bright 
colors, which we know to be impossible in vegetation without sun- 
light, the influence is chemical. 

The first physical law is, that growth-force, uninfluenced by 
inherited peculiarity,* or any stronger influence locating a nutri- 
tive fluid, must develop extent in tlie directio7i of least resistance, 
and density on the side of greatest resistance, when not too great. 
The illustration of this statement would be that a globular mass of 
cells brought to the point of junction of two media, as water and 
earth or air and earth, elongates in the direction of the medium pre- 
senting the least resistance, i. e., air. Thus a longitudinal develop- 
ment would originate from a centrifugal, and a repetition of the 
same process would produce branches. The reason why repetition 
should appear along the sides instead of as continued prolongation 
of the axis, arises probably from the difficulty of conveying fluid 
nutritive material far from the base as a source of supply, and the 
occurrence of various mechanical obstacles easy to be conceived. 
In low plants, where nutrition is absorbed by all parts of the axis, 
which branch, as the subterranean parts of fungi {mycelium), dif- 
ference of local supply would produce an effect. In higher plants, 
where fluid nutriment is only introduced at one point (the root), 
and conveyed by special layers of cells or tubes, the difficulty of 
maintaining supply at a distance from its source would encourage 
lateral repetition or branching, f 

* This is supposed to be due to atomic peculiarity of cell-substance. 

f The great power exerted in a given direction by growth-force due to gradual 


6. On the Origin of Intelligence. 

Leaving this part of the subject, we approach one of higher 
interest, viz., the effects of the metaphysical or mental acquire- 
ments of animals on their exertions in effort and use. The growth 
of the mind in animals has, no doubt, followed the same laws 
obeyed by that of man : the difference being that the lower forms 
have remained permanently fixed in stages early passed by the 
lord of living beings. The foundation qualities from which all 
the phenomena of intellect may be derived are, the powers of re- 
tentiveness (memory) and of perceptions of resemblance and dif- 
ference. These traits are well known to be possessed by many 
animals, and perhaps in some degree by all. Their possession 
will be modified by the power of exercising attention, which, in 
its turn, will depend on the sensitiveness of the animal to impres- 
sions — in other words, the ease with which consciousness may be 

The origin of the disposition to take food will be the rudiment 
of all that appears as will in higher animals, and which, though 
supposed to guide, is the creature of so many stimuli. This ori- 
gin is supposed by metaphysicians to be the result of education 
of the '* spontaneous activity" of animals by their pleasures and 

The brain of man and of other animals is an organ which re- 
ceives and retains pictures and impressions, both painful and 
pleasurable. The retention of these pictures is not a state of con- 
sciousness, but they may be brought into the consciousness accord- 
ing to the law of "contiguity," or association. That is, that the 
recurrence in the actual of some object or event, which was per- 
ceived on a former occasion, at or near the same time as another 
object or event not again repeated in the actual, will bring the 
latter before the consciousness. So, also, the revival of one such 
picture will bring within the mental vision others impressed on 
the mind at or near the same time as the first. These events may 
have been in the reality either painful or pleasurable. On the 
recurrence of circumstances which on a former occasion resulted 
in pain, the resuscitation of the mental picture, then impressed on 

acquisition and inheritance is illustrated by the plantain, Flantago major. Although 
without axis, it has been observed by James C. Crcsson, in the Philadelphia Park, 
and Alfred Cope, on his drive, to force itself through a solid bed of hard vulcanite 
pavement, several inches in thickness. 


the memory, produces an anticipation of the pain, and the ani- 
mal at once flies from the source of danger. So, also, with pleasur- 
able objects, the resultant action being the reverse, or an attraction 
to the object. In botli cases a previous experience of the relation 
between the object and the sensation of j^leasure or pain must have 
been had. 

There is, in addition, the power of determining differences and 
likenesses, by which contiguities or associations are originated in 
the mind, of a character different from that resulting from the 
relations of times of receipt of the impression. Such contiguities 
recall pictures to the consciousness in consequence of their resem- 
blances in essential qualities. 

On these two bases, together with the perceptive faculties, rest 
the complex phenomena of the animal and human minds. They 
are probably physiological functions of brain tissue, for the follow- 
ing reasons, among others : 

1. Impressions are conveyed by physical means to the brain. 
The brain can only receive a given number at a time without ex- 
haustion, and is prepared to receive more after being nourished. 
Impressions long forgotten are revived in certain states of disease. 
Impressibility and memory are most marked during growth, and 
diminish with age. 

2. If impressions are physically produced and preserved in the 
brain, those made at or near the same time would remain close 
together in tlie brain, and this material proximity would be the 
"contiguity" according to which they would come before the 

3. Classification or appreciation of resemblances takes place 
unconsciously in the mind (by " unconscious cerebration "). Ee- 
semblances not seen at the time of impression suddenly flash into 
the consciousness on a subsequent revival of it. The " contigu- 
ity" to like things thus established may be more or less lasting in 
the mind than the contiguity of circumstances under which the 
impression was made. 

4. As "contiguity" in time is believed to be revived by 
contiguity in location of impressions in the "perceptive" part 
of the brain, so "contiguity" of resemblance may be believed to 
depend on contiguity of location in the " reflective " part of the 

The retention of the contiguities of time and of resemblance 
constitute the basis of education of an animal, and its intelligence 


will be in proportion to the number and complexity of these ac- 

The lowest exhibitions of contiguity, or association in time, 
do not require a nervous system for their disj^lay. The Protozoa, 
which are without nervous system, exhibit its results in their de- 
terminate seizure of some small objects as food and rejection of 
others. The sea anemones (Actinia) display some preferences as 
to the substances to which they attach themselves. All power of 
taking food implies the retention of the impression of pleasure on 
first accidentally coming in contact with it. This power is then 
present in protoplasmic beings of the simplest type. 

All the movements of animals have been shown to dejiend on 
a direction of this motive force, consequent on a necessity for 
avoiding pain and obtaining pleasure. It may be regarded, more- 
over, as a truth that heightened vitality or energetic conversion 
of force is always a state of pleasure, while depressed vitality is 
generally the cause (as well as a consequence) of pain. Hence the 
pleasurable nature of taking food, and the early education of an 
animal in the distinction between objects nutritive and non-nutri- 

It is well known, however, that food may be taken, and many 
or all other functions and acts be performed automatically, or in 
a state of unconsciousness. This is as much the case with the 
highest powers of thought (as in unconscious cerebration) as with 
the humblest acts which satisfy bodily wants. The question then 
arises whether these acts may not arise in a state of unconscious- 
ness. So far as our own self-knowledge goes, we would reply in 
the negative. All intellectual functions are i^roduced by educa- 
tion, and education involves consciousness at every step. Other 
habitual and automatic acts were originated consciously, but the 
contiguity of parts of the act becoming impressed on the brain, 
future repetitions of it are reflex or unconscious. We have seen 
that the development of the habits of animals is in strict obedi- 
ence to the preference for pleasure and avoidance of pain. Pleas- 
ures and pains of course express sensations which involve con-, 
sciousness. It then appears to me that, in the lowest animal, con- 
sciousness must be present at the time of origin of every habit, 
but that it may have been soon lost in each case, and the habit 
become automatic. 

If this position be true, every subsequent addition to or change 
of habits must have been accompanied by a resuscitation of con- 


scionsness. But how is consciousness aroused in the cases which 
we can investigate — that is, in our own species ? In the common 
case of sleep, a mere sound is sufficient to cause its rerurn. In 
syncope and other forms of loss of consciousness, a sudden shock, 
as of cold water thrown on the face, will often restore it. In 
ordinary states, compulsion or pressure will produce a more in- 
tense degree of consciousness. Indeed, in many persons conscious- 
ness varies greatly under different influences ; thus a dreamy state 
naturally follows a lack of nutrition of the brain, as during a fast, 
but the mind is readily aroused from it by a strong or sudden im- 
pression made on the senses or by an effort of will. It is, hence, 
to be believed that in animals whose acts may be largely automatic 
consciousness is aroused by exceptional sights, sounds, hunger, 
and other sensible impressions, the more readily in proportion to 
the development of the sensory ganglia of the brain. In the low- 
est animals, consciousness will be aroused with much greater diffi- 
culty, and life must be in part a blank, and in part a dream, at 
rare intervals illumined by gleams of consciousness produced un- 
der the influence of strong external stimulus. At these times of 
awakening we must believe that new movements are instituted, 
which will become habitual in proportion to the extent to which 
they are repeated. 

From what is known of reflex actions, it is evident that move- 
ments may become habitual, and hence automatic, wherever cellu- 
lar or gray nerve-substance exists. Thus, movements instigated by 
the spinal nerves derive their automatism from the spinal medul- 
la. This axis no doubt derived the original nerve-force from the 
brain, but repetition of the act under the original stimulus con- 
fers the automatic power on the spinal cord or ganglionic center 
as certainly as on the brain. This must of necessity follow the 
complication of nervous structures by addition to the original 
center. Thus are explained the automatic movements of the 
frog's or centipede's legs in the well-known experiments, when 
separated from the brain or principal nervous center. 

Greater difficulties are experienced in accounting for the origin 
of the automatic movements of plants. It is evident, however, 
that many of these, perhaps all, are not due to the energy of mo- 
tive-force, but are phenomena of growth-force alone. Motion is 
produced by the change of direction imparted to growth-force by 
the influence of heat, light, contact, etc. This will largely follow 
as a consequence of the longer persistence of growth in plants 


than in animals. In some of the rery lowest pLmts movement 
would seem to be similar to that seen in the lowest animals. The 
origin of intelligence is then to be found in the first traces of con- 
sciousness. But inquiry will go further in the search for truth. 
One school of physiologists believes consciousness to be due to cer- 
tain molecular changes of nerve (i. e., brain) substance. No doubt, 
these are essential to consciousness ; yet it is, at least, utterly 
inconceivable that any molecular condition should be capable of 
recognizing either pleasure or pain. Here we find the first ap- 
pearance of the "feelings," that part of the human mind which 
deserves to be called, par excellence, "the soul," and which is 
the "locator" of all the forces which go to build up the tis- 
sues, organs, and parts of the body ; and hence the organic type 
of the intellect and even of the will. For if we find growth-force 
to be a correlative of physical force, and subject to motive-force 
for its "location," so, while we find that motive-force is in like 
manner but another equivalent of ordinary force, we find it also 
subordinate to this princii^le which "locates" it. 

7. On Intelligent Selection. 

We will now retrace our steps along the line of causes and 
effects, and see, if possible, the nature and results of "intelligent 

Protoplasm, homogeneous or cellular, discharges a force called 
"motive-force," or neurism, which it converts from surrounding 
forces by virtue of its molecular (chemical) or atomic constitu- 
tion. Its spontaneous exhibitions as movements bring it into 
contact with surrounding objects, when, if sufficiently sensitive 
to impressions, consciousness of a pleasurable or painful charac- 
ter is aroused. Then in proportion to its sensitiveness, and the 
strength of the impression, the protoplasm retains the latter in 
an unconscious way, and, on the subsequent recurrence of the ob- 
ject to the consciousness, the pleasurable or painful attribute is 
also revived by the law of "contiguity." The "vital principle" 
interfering restrains the motive-force from exercise toward it, if 
it be painful, or releases it for motion toward it, if it be pleasur- 
able. This quality of the vital principle is a power of choice, and, 
in so far as consciously exercised, is will* Nothing is better 
known than that acts originated consciously may, by repetition, 

* For further development of this subject see Part IV of this book. 


come to be exercised unconsciously, or as habits. The form these 
habits take, will depend on the opportunities and conditions 
offered, for instance, in the matter of food, by the surrounding 
order of things. Motive-force is, of course, only another name 
for effort and use ; the former being a putting forth by means of 
conducting material or organs, without executive apparatus ; the 
latter always requiring organs or parts by which to execute. 

If, as previously assumed, effort and use locate growth-force, 
cellular structure will apjDear in the directions indicated by the 
activity of motive-force. It is converted by protoplasm from heat 
and chemism, or one only of these. That it does not require dif- 
ferentiated '^ motive-force " as a source, is proved by the growth 
of 25lants, which have no motion projser. 

Growth-force, by its "repetitive" action,* creates organs. 
These at first will be extremely simple, but, as machines, at once 
increase the power of the animal to produce motive-force by con- 
version, whether the machine be a digestive apparatus for the ap- 
propriation of the material, or a mechanical one for the exercise 
of the force, the former necessarily preceding the latter in time. 

With the increased power of assimilation (digestion) comes a 
larger amount of material for increased exhibition of growth-force, 
a j)art being burned or otherwise converted into the force, and a 
part remaining as the material from which the cells are construct- 
ed. In the latter part of the gi-owth-j^eriod a considerable j)ortion 
is usually consumed for motive-force. 

In the history of the material environment, various changes of 
condition succeeded each other. Changes of level took place ; 
waters were i^urified by precipitation of chemical compounds ; 
fresh waters were established ; the atmosphere deprived of various 
gases ; new mineral, and especially vegetable, products took their 
appropriate places. All these offer a vast variety of food-supply 
and opportunity for the pleasurable discharge of motive-force, and, 
under the laws pointed out, efforts of animals were directed in va- 
rious lines, as the conditions ^jresented themselves. Thus execu- 
tive organs were produced of varied character. Some acquired 
limbs and others wings for transportation from place to place. 
What a vast addition to their impressions must have been acquired 
by the first animals which could thus leave the place of their 
birth ! How many new '* contiguities" were established, and how 

* See " Method of Creation," on the Law of Repetition. 


many new habits originated ! Look again at the acquisition of 
teeth. From a soft uniform diet the animal no doubt gradually 
learned to appropriate hard substances, and what a world of ex- 
perience and consequent habit must haye been at once placed in 
its way ! 

These acquisitions are of course mental, and include both 
kinds of contiguity, viz., that of succession in time, and that of 
association through resemblance. Animals choose between objects 
chiefly in accordance with the first mode, but are not lacking in 
the second quality. As an example of the latter, classification ac- 
cording to color' is exhibited by some birds, which choose brightly 
colored objects and reject dull ones— the Australian bower-bird, 
for instance. 

As is well known to metaphysicians, these acquisitions lead to 
"predication" and "forethought." Thus a hound becomes ac- 
quainted with the habit of a buck or rabbit in doubling, or in fol- 
lowing a given circuit. The recurrence of the chase recalls the 
habit in consequence of contiguity of the impression of the former 
pursuit of the animal and the course it took. The hound then 
supposes or " predicates " that the deer will repeat the course. We 
know that some do so from the fact that they have been observed 
to cut off the curves in the animal's track, or to station themselves 
at the point where the deer, for instance, will pass. In the sec- 
ond act forethought is also involved. The hound sacrifices the 
lesser pleasure of the chase for the greater one of securing the 
prey. In forethought, experience having taught which circum- 
stance results in greater and which in less pleasure, action is re- 
strained in the presence of the second for the sake of procuring 
the first. Thus in ants, immediate pleasure suggests a life of labor 
enough for present wants, and ease for the remaining time ; but 
the greater pleasure of existence during some time of scarcity has 
induced some of them to lay up a store, which has developed into 
the complete protection against winter they display in cold cli- 

In the cases cited it is perfectly evident that the hound would 
never have learned to predicate had he not had limbs to bring him 
in contact (by pursuit) with the habits of the buck. Nor would 
the ant have learned to provide if it had not been furnished with 
the jaws necessary to the excavation of chambers and the carrying 
of food. And neither would have performed these mental acts 
had they not possessed nervous centers capable of sensation, rcten- 


tion, and classification. But the deyelopment of these qualities 
depended on the possession of the executive organs. 

Thus intelligence of various degrees has resulted — first, from 
possession of executive organs ; secondly, establishment of con- 
tiguities by their use ; thirdly, from classifications based on con- 

There are two notable examples of the great advance in mental 
accomplishment inaugurated by the acquisition of an executive 
organ. The first is the acquisition of the hand by the monkey. 
Any one who has compared their manners with those of the spe- 
cies of unguiculate (clawed) animals — as, for example, the dog — 
must be struck by the immense advantage possessed by the for- 
mer. To begin with, it renders the monkey an exj)ert climber 
and catcher of moving objects. Then he greatly increases his 
habits of observation by the facility with which he brings objects 
before his eyes. The minuteness of his criticism is aided by his 
power of manipulating with his fingers. He learns the results of 
throwing. A cautious monkey, set on a strange animal or jier- 
son, does not rush at them to bite like the dog, but takes the more 
refined method of throwing sticks and stones. In obtaining ob- 
jects, if they be out of reach, a monkey uses a stick to draw them 
in with. In a Cebus capucinus, in my possession, a leather sti'ap 
was preferred, and was thrown with great dexterity, and the ob- 
ject always secured by drawing it nearer in loops of the strap. If 
the strap were sometimes thrown out of reach, the monkey would 
use a stick or poker in order to obtain it again. All this would 
have been quite impossible without a hand. This facility has not 
been lost on the intelligence of the monkeys. Their curiosity is 
proverbial, and no animal can com^jare with them as successful 
thieves ; moving in bands, with watchers stationed, and taking 
pains to store their booty in their cheek-pouches while they have 
opportunity, and not wasting time in eating exclusively. 

Another instance is that of man. Here the acquisition con- 
sisted of vocal organs capable of speech. Any means of com- 
municating and recording thoughts had the stupendous conse- 
quence of rendering the acquisitions of one man or class of men 
the common property of all. Another consequence, equally im- 
portant, is the preservation of successive races of men from the 
necessity of passing through the experiences of those that pre- 
ceded them, and the enabling them to commence their intellectual 
life nearly where the others left off. So great would necessarily 


De the location of activity in the brain, that its stages of growth 
would be the principal changes of structure to be witnessed in 
human history, together with those which should result from loss 
of growth-force in other regions by abstraction. 

To return to the material aspect of the case. The discrimina- 
tion between pleasure and pain locates motive-force, which is 
derived from without. Motion or use locates growth-force, also 
derived from without, and thus produces organs out of material 
derived from without. These organs diversify the directions of 
motion. From new movements arise new pleasures and pains, 
and motion is again "located" in its exhibitions in some particu- 
lar directions, and restrained in others. These directions depend 
on external circumstances at the first. The determination of 
motion to certain lines locates growth-force in those lines, and 
new parts are produced, which are further executive organs and 
types of structure. We now repeat the circuit. New executive 
organs introduce new contiguities, the number depending on the 
general complication of the animal in connection with that of the 
organ, and new pleasures and pains result. The pleasures again 
determine activity, and, under the circumstances already men- 
tioned, growth-force is again located. 

In these facts lies the explanation of the principle of direction 
or location of executive structures about the head, termed by 
Prof. Dana "cephalization." The increasing demands of in- 
telligence locate growth-force round its organ, the brain, etc., 
while such location reacts by furnishing means of increased ac- 
tivity of mind. 

These conjunctions of growth with executive capacity, consti- 
tute a class of "expression points"; points attained without 
leaps, and abandoned without abruptness, but constituting great 
steps of i^rogress, pregnant with future results. 

The part played by "intelligent selection" remains to be 
considered. I have heretofore spoken only of variation of types, 
and not dwelt on their persistence. This is a most important 
consideration, for most men see a great deal more of tlie latter 
than the former. Species present their characters intact for long 
periods, and many structural peculiarities have had great range 
in time. 

I recur to the origin of the "location of growth-force," i. e., 
the direction of motive-force. This is located by the appreciation 
of pleasure and pain. Now, every one knows that different ani- 


mals of the same species vary exceedingly in their sensitiveness 
to exterior influences ; that is, they differ in the degree in which 
the same object affects their consciousness. That which excites 
one is unnoticed by another ; what fills one with alarm scarcely 
rouses the attention of another. It is well known also that differ- 
ences in the power of retention are to be found in the same spe- 
cies of animals. The variations in persistence of memory are 
very great. While, therefore, one individual of a species will ac- 
quire a store of "contiguities," another of the same will possess 
but few. In other words, the degree with which objects are 
impressed on the consciousness, and the degree with which they 
are returned to the consciousness, vary greatly in the same spe- 
cies. Here we have the basis for the origin of totally different 
unconscious habits and reflex actions, and consequent divergences 
in the "location of growth-force." 

Those in which these impressibilities are most highly devel- 
oped will accumulate mental acquisitions most rapidly ; in other 
words, they will be the most intelligent of their species. While 
others follow the old routine of once acquired and then inherited 
habits, those in whom consciousness most frequently recognizes 
events will originate new acts and new habits. 

Intelligence is a conservative principle, and always will direct 
effort and use into lines which will be beneficial to its possessor. 
Here we have the source of the fittest— i. e., addition of parts by 
increase and location of growth-force, directed by the influence of 
various kinds of compulsion in the lower, and intelligent option 
among higher animals. 

Thus, intelligent choice, taking advantage of the successive 
evolution of physical conditions, may be regarded as the originator 
of tlie fittest, while natural selection is the tribunal to which all 
the results of accelerated growth are submitted. This preserves 
or destroys them, and determines the new ]wints of departure on 
which accelerated growth shall build. 

If the above positions be true, we have here also the theory of 
the development of intelligence and of other metaphysical traits. 
In accordance with it, each trait appropriates from the material 
world the means of perpetuating its exhibitions by constructing its 
instruments. These react by furnishing increased means of exer- 
cise of these qualities, which have thus grown to their full expres- 
sion in man. 



Introduction. — The present fragmentary essay is a portion of 
what other occupation has prevented the author from comi^leting. 
It does not, therefore, amount to a complete demonstration of the 
points in question, but it is hoped that it may aid some in a classi- 
fication of facts with a reference to their signification. When all 
the vast array of facts in possession of the many more learned 
than the writer are so arranged, a demonstration of the origin of 
species may be looked for somewhere in the direction here at- 
tempted to be followed. 

Conclusions of any kind will scarcely be reached, either by 
anatomists who neglect specific and generic characters, or, secondly, 
by systematists who in like manner neglect internal structure. 
Such will never perceive the system of nature.* 


I. Relations of allied genera. 

First : in adult age. 

Second : in relation to their development. 

a. On exact parallelism. 

p. On inexact or remote parallelism. 

y. On parallelism in higher groups. 

S. On the extent of parallelisms. 

II. Of retardation and acceleration in generic characters. 
First : metamorphoses in adult age. 

a. The developmental relations of generic and specific char- 

* It might seem incredible that either class should systematize with confidence, 
yet a justly esteemed author writes even at the present day, " However, there is 
scarcely a systematist of the present day who does not pay more or less attention to 
anatomical characters, in establishing the higher groups!" (The italics are our 
own.) As though a system were of any value which is not based on the whole struct- 
ure, and as though lotoer groups were only visible in external characters ; in a word, 
as though external (muco-dcrmal, dental, etc.) characters were not " anatomical " ! 


ft. Probable cases of transition. 
y. Ascertained cases of transition. 
Second : earlier metamorphoses. 

S. The origin of inexact parallelisms. 

III. Eelations of higher grouj^s. 

a. Of homologous groups. 

ft. Of heterology. 

y. Of mimetic analogy. 

IV. Of natural selection. 

a. As affecting class and ordinal characters. 
ft. As affecting family characters. 
y. As affecting generic characters. 
S. As affecting specific characters. 
e. On metaphysical species. 

V. Of epochal relations. 

The laws which have regulated the successive creation of or- 
ganic beings will be found to be of two kinds, as it appears to the 
writer. The first, that which has impelled matter to produce_j->, 
numberless ultimate types from common origins ; second, that / 
which expresses the mode or manner in which this first law has 
executed its course, from its commencement to its determined 
end, in the many cases before us. 

That a descent, with modifications, has progressed from the 
beginning of the creation, is exceedingly probable. The best 
enumerations of facts and arguments in its favor are those of 
Darwin, as given in his various important works, "The Origin of 
Species," etc. There are, however, some views respecting the 
laws of development on which he does not dwell, and which it is 
proj)Osed here to point out. 

In the first place, it is an undoubted fact that the origin of 
genera is a more distinct subject from the origin of species than 
has been supposed. 

A descent with modification involves continuous series of or- 
ganic types through oiie or many geologic ages, and the co-exist- 
ence of such parts of such various series at one time as the law of 
mutual adaptation may permit. 

These series, as now found, are of two kinds : the uninter- 
rupted line of specific, and the same uninterrupted line of generic 
characters. These are independent of each other, and have not, 
it appears to the writer, been developed pari passu. As a general 


law, it is proposed to render bighly probable that the same specific 
form has existed through a succession of genera, and perhaps in 
different epochs of geologic time. 

"With regard to the first law of development, as above proposed, 
no one has found means of discovering it, and perhaps no one ever 
will. It would answer such questions as this : What necessary- 
coincidence of forces has resulted in the terminus of the series of 
fishes in the perches as its most specialized extreme ; or, of the 
Batracliia, in the fresh- water frogs as its ultimum ; or, of the 
thrushes, among birds, as their highest extreme : in a word, what 
necessity resulted in man as the crown of the mammalian series, 
instead of some other organic type ? Our only answer and law for 
these questions must be, the will of the Creator. 

The second law, of modes and means, has been represented to 
be that of natural selection, by Darwin. This is, in brief, that a 
disposition to a general variation on the part of species has been 
met by the greater or less adaptation of the results of such varia- 
tion to the varying necessities of their respective situations. That 
the result of such conflict has been the extinction of those types 
that are not adapted to their immediate or changed conditions, 
and the preservation of those that are. 

In determining those characters of plants and animals which 
constitute them what they are, we have, among others of higher 
import, those which constitute them species and those which con- 
stitute them genera. What we propose is : that, of the latter, 
comparatively very few in the whole range of animals and plants 
are adaptations to external needs or forces, and of the former a 
large proportion are of the same kind. How, then, could they owe 
their existence to a process regulated by adaptation ? 

Darwin is aware of these facts to some degree, but, as already 
said, he does not dwell on them. Where he does, he does not at- 
tempt to account for them on the princij)le of natural selection. 

There are, it appears to us, two laws of means and modes of 
development : I. The law of acceleration and retardation. II.' 
The law of natural selection. 

It is my purpose to show that these propositions are distinct, 
and not one a part of the other : in brief, that, while natural selec- 
tion operates by the "preservation of the fittest," retardation and 
acceleration act without any reference to "fitness" at all; that, 
instead of being controlled by fitness, it is the controller of fitness. 
Perhaps all the characteristics sujjposcd to mark generalized groups 


from genera up (excepting, perhaps, families) have been evolved 
under the first mode, combined with some intervention of the sec- 
ond, and that specific characters or species have been evolved by a 
combination of a lesser degree of the first with a greater degree of 
the second mode. 

I propose to bring forward some facts and propositions in the 
present essay illustrative of the first mode. 


First. The writer's views of the relations of genera have al- 
ready been given at the close of an "Essay on the Cyprinoid 
Fishes of Pennsylvania."* It is easy enough to define isolated 
genera which have few immediate affines ; but among extensive 
series of related forms the case is different. One principle, how- 
ever, pervades the conception and practice of all zoologists and 
botanists, which few take pains to analyze or explain. It is 
simply that they observe a successional relation of groups, by 
which they pass from one type of structure to one or several other 
types, and the presence or absence of the steps in this succession 
they regard as definitions of the genera. 

It is true that the reader will often find introduced into diag- 
noses of genera characters which indicate nothing of this sort. It 
is often necessary, indeed, to introduce characters which are not 
peculiar to the genus characterized, for the sake of distinguishing 
it from similar ones of other series, but this only in an imi^erfect 
state of the record. Moreover, the ability of the writer to distin- 
guish genera being thus tested, he too often fails by introducing 
family and sisecific characters, or by indulging in an unnecessary 
redundancy. In general, it may be said that adjacent genera of 
the same series differ from each other by but a single character ; 
and, generally, that the more remote differ by characters as numer- 
ous as the stages of their remove. 

It is precisely as, among the inorganic elements, we pass from 
the electro-negative, non-oxidizing extreme of the halogens, with 
fluorine as the extreme, to the electro-positive, violently oxidizing 
extreme of the alkaline metals, whose extreme is potassium, by 
steps whose relative position is measured or determined first by 
these tests ; and as these steps have each their included, series of 

* " Trans. Amer. Philos. Soc," 1866, from " Proc. Acad. Nat. Sci.," Phil, 1859, 
p. 332. 


bodies, characterized by their successive relations on the lower 
level of a subordinate range of characters. This principle is dis- 
tinctly admitted by many zoologists,* those who deny it generally 
failing to perceive it because they attempt to gauge a major scale 
by characters which are really the test of one or all of the subordi- 
nate or included scales. It holds true of most of the groups of 
organic beings ; thus the class is a scale of orders, the order of 
tribes. I will not now say that the tribe is a scale of families, as 
the case is here much modified ; but what is chiefly to be consid- 
ered in this essay is, that the family is comj)osed of one or several 
scales of genera. 

Second. Now, the more nearly allied genera are, the more 
surely will these generic steps be found to fall into the direct line 
of the steps of the development of the highest, or that with the 
longest scale, the former being truly identical with the latter in 
generic characters. Less allied genera will offer an inexact or in- 
complete imitation of such identity — some additional character 
being present to disturb it. Such genus belongs to another 
series, characterized by the disturbing feature, whose members, 
however, l)ear to each other the relation claimed above for such. 

The relation of genera, which are simply steps in one and the 
same line of development, may be called exact parallelisin, while 
that of those where one or more characters intervene in the 
maturity of either the lower or higher genus, to destroy identity, 
may be called incomplete parallelism. 

The latter relation has been dwelt on by von Baer, Agassiz, and 
other writers, but none have accepted the existence of exact paral- 
lelism, or seen its important relation to the origin of genera. 

Third. That the lowest or most generalized terms or genera 
of a number of allied series will stand to each other in a relation 
of exact parallelism. That is, if we trace each scries of a number, 
up to its lowest or most generalized genus, the latter together will 
form a series, similar in kind to each of the sub-series ; i. e., each 
genus will be identical with the undeveloped conditions of that 
which progresses the farthest, in respect, of course, to the char- 
acters which define it as a series. 

Those characters of the skeleton which we are accustomed to 
call embryonic are only so because they relate to the develop- 

* Prof. Bronn, in his " Classen u. Ordnungen des Thierreiches," has everywhere 
a chapter on " Die aufstcigende Rcihe" (" the ascending scale "). 


mental succession witnessed in animals at the present time. 
Characters not so called now were probably as much so at one 
period now passed. Hence embryonic characters of the bony 
system do not, as I have often had occasion to observe, charac- 
terize the types of the highest rank, but only subordinate divis- 
ions of them. Thus the elasmobrauchs are j^robably repressed 
forms of groups of a really higher gi'ade than the bony fishes, or 
teleostei, which may be known to us. In their early presence in 
the geologic series we have evidence of the first beginning of a 
higher type. 

In the same manner it has been discovered that the molecular 
aggregation of the elementary substances does not characterize 
their highest or most distinct series, but rather the substances 
themselves within the group or family to which they belong. 
The gaseous, liquid, and solid molecular conditions, being charac- 
ters distinguishing otherwise allied substances in the same way 
morphologically (we can not say yet developmentally), as the car- 
tilaginous, osseous, and exostosed or dermosseous characters dis- 
tinguish otherwise nearly allied genera. 

The ''family " group embraces one or many of such series. 
If we trace the series in several families to their simplest or most 
generalized terms or genera, and compare them, we will not find 
the relation to be one of exact parallelism in the series of the 
'* order," so far as our present knowledge extends, but, in a devel- 
opmental sense, one of divergence from the commencement. 

If we could know the simplest known terms or family charac- 
ters of a number of groups of families, or " orders," we would 
probably find them to represent a series of exact parallelism, 
though to find such simplest terms we must go far into past 
periods, since the higher the group the more extensive the range 
of its character, and the less likely to be found unmixed with ad- 
ditions and extensions, in modern times. 

Finally, the series of classes is in the relation of the essential 
characters of the same, as expressed in their now extinct, most 
generalized and simple representatives, also one of "exact paral- 

a. Examples of Exact Parallelism.^ 

1. As an example we may take the genus Trachycephalus 
{Batrachia anura). Nearly allied to it is the genus Osteo- 

* In generic series. 


ceplialus, which differs in the normal exostosis of the cranium 
not involving the derm, as in the former. Close to this is 
Scytopis, where the fully ossified cranium is not covered by an 
exostosis. Next below Scytopis is Hyla, where the upper surface 
of the cranium is not ossified at all, but is a membranous roof 
over a great fontanelle. Still more imperfect is Hylella,* which 
differs from Hyla in the absence of vomerine teeth. Now, the 
genus Trachycephalus, after losing its tail and branchiae, pos- 
sesses all the characters possessed by the genera Hylella and Hyla, 
either at or Just before the mature state of the latter, as the 
ethmoid bone is not always ossified in advance of the parietals. 
It soon, however, becomes a Scytopis, next an Osteocephalus, 
and finally a Trachycephalus. It belongs successively to these 
genera, for an exhaustive anatomical examination has failed to 
reveal any characters by which, during these stages, it could be 
distinguished from these genera. 

Now, it would be a false comparison to say that the young of 
Trachycephalus was identical with the genus Agalychnis, which 
in truth it resembles, because that genus is furnished with one 
other character — the presence of a vertical pupil — and belongs to 
another series in consequence, which is represented as yet, with 
our present imperfect knowledge — or perhaps imj)erfect fauna — 
by three genera only. 

2. The lowest type of the near allies of our common fresh- 
water frogs is the genus Eanula, where the prefrontal bones are 
narrow strips on each side the ethmoid cartilage ; the ethmoid 
cartilage itself entirely unossified above, and the vomerine teeth 
very few and on a small elevation. There are two species, R. 
affinis and R. palmipes.\ The other species have the ethmoid 
cartilage ossified above, at least beneath the extremities of the 

Those of the latter most like Eanula possess the same tjrpe of 
narrow prefrontals, separated by a broad area of cartilaginous 
ethmoid, and fasciculi of teeth. Of this type is Ra7ia delalandii, 
and probably R. porosissima, Steind., of the South Ethiopian 
region. Other species of the same type extend their vomerine 
patches into lines ; such are R. mascariensis, R. fasciata, R. 
oxyrhynchus, R. grayi, and other South African species. 

* I refer to H. carnea m., not having Rcinhardt and Liitken's type of this genus, 
f These species are now believed to be identical, but three others have been dis- 
covered (18S6). 


The prefrontals are subtriangular, and approacli each other 
more or less in the numerous species of North America and of 
the Eegio Palsearctica, while generally the vomerine teeth are in 
fascicles or very short series. In the Ethiopian Rmia fuscigula 
the prefrontals unite on the median line, roofing over the ethmoid 
cartilage and reducing it, while the vomerine teeth are in very 
short lines. 

In the species of the Palseotropical region, Rana tigrina, R. 
vittigera, R. cyanoplilyctis, R. grunnietis, R. hexadactyla, R. 
corrugata, R. elirenhergii, R. gracilis, and the Ethiopian R. occi- 
pitalis, the prefrontals not only unite solidly (the suture remain- 
ing on the median line), but extend and closely fit to the fronto- 
parietals. The vomerine patches have lengthened out into series. 

Now, the young of the latter type of Rana (I take as an ex- 
ample the R. tigrina, one of the most abundant and largest of 
Indian frogs) presents the subtriangular prefrontals neither in 
contact with each other or with the frontoparietals, and the 
vomerine series is much reduced ; in fact, it belongs in all 
respects to the Palsearctic group. I have not examined younger 
specimens, but have no doubt they are like those of the Palae- 
arctic ; which are, in their young stage, precisely of the type 
of the -Ethiopian Rana, with fasciculate teeth like the young of 
those of the same region with teetli in series, since the prefrontals 
are still more reduced, becoming linear. Finally, the first stage 
of the Nearctic Rana, after losing the larval tail, is the genus 
Ranula, having linear prefrontals, minute vomerine teeth, and 
the ethmoid ring cartilaginous above. 

These points of structure are of generic quality, but I have 
not regarded any group as sufficiently defined to be so regarded, 
except Ranula, as the adults of some species appear not to be con- 
stant in possessing them. Thus a very large Rana catesheyana 
sometimes exhibits prefrontals in contact on the median line, 
while it is difficult to say whether R. areolata of North America 
is of the Nearctic type so much as of the ^Ethiopian. Neverthe- 
less, the groups are generally quite geographically restricted. 

3. A similar relation exists between the genera Hyperolius, 
Staurois, and Heteroglossa in respect to the prefrontal bones and 
the separation of the outer metatarsi, and — 

4. Between Ixalus, Rhacophorus, and Polypedates also, in 
reference to vomerine teeth, bifurcation of last phalange, and 
dermoossification of the cranium. 


5. When the larvoe of certain salamanders (Spelerpes) possess 
branchiae, they also lack one digit of the hind foot, also the max- 
illary, nasal, and prefrontal bones, and exhibit a broad continuous 
palatopterygoid arch, in close contact with the parasphenoid. 
The prootic is separated from the exoccipital by a membranous 
space, and the exoccipitals themselves are not yet united above 
the foramen magnum. There is at the same time a series of 
splenial teeth. Both ceratohyals are confluent, the posterior is 
present, and there are but three superior hyoid arches. After 
they lose the branchice, the hinder foot, which has four toes only 
for a time, gradually adds another at first rudimental digit, in the 
Mexican species ; in most North American species the fifth digit 
appears at an early larval stage. Five digits are finally present in 
all Spelerpes. 

We have thus four combinations of the above characters, at 
different periods of the life history of certain (but not of all) of 
the species of Spelerpes. There exist four permanent series of 
species or genera, equivalent to these stages. The well-known 
*'perennibranchiate" Necturus is nearly identical with the first, 
Batrachoseps with the second, the half-toed Spelerpes with the 
third, and the typical Spelerpes is the last. 

In one character of generic value only do I find that Necturus 
differs from the early larval Spelerpes. It closes the premaxillary 
fontanelle with which it commences, by an approximation of the 
premaxillary spines, but not by a sutural union, as takes place in 
Amblystoraa. It thus, in this one point, advances a stage beyond 
the condition to which Spelerpes attains, though it may be a 
question whether such a closure without union should not be 
classed among the specific characters by which iY. maculatus dif- 
fers from the young of the various Spelerpes, as they do from 
each other. Characters of the latter kind are the following : in 
N. maculatus the frontals are more deeply emarginate behind ; it 
has little or no ala on the inferior keel of the caudal vertebrae, 
which is prominent in Spelerpes larvae. 

It may be that the parallelism in the case of Spelerpes is inex- 
act by one character, and that a strictly developmental one ; or 
it may be regarded otherwise.* 

6. It is well known that the Cervidce of the Old World devel- 

* Necturus differs from these l;irvie by another aud more important character, 
viz., the presence of the 03 intercalare. 


op a basal snag of the antler (see Cnvier, "Ossem. Fossiles"; 
Gray, "Catal. Bi'it. Mus.") at the third year; a majority of those 
of the New World (genera Cariacus, Subulo) never develoj) it 
except in "abnormal" cases in the most vigorous maturity of the 
most northern Cariacus {C. virginianus) ; while the South Ameri- 
can Subulo retains to adult age the simple horn of the second 
year of Cervus. 

Among the higher Cervidae, Rusa and Axis never assume char- 
acters beyond an equivalent of the fourth year of Cervus. In 
Dama the characters are on the other hand, assumed more rapidly 
than in Cervus, its third year corresponding to the fourth of the 
latter, and the development in after years of a broad plate of 
bone, with points, being substituted for the addition of the corre- 
sponding snags, thus commencing another series. 

Returning to the American deer, we have Blastocerus, whose 
antlers are identical with those of the fourth year of Cariacus. 

Now, individuals of the genus Cervus of the second year do 
not belong to Subulo, because they have not as yet their mature 
dentition. Rusa, however, is identical with those Cervi whose 
dentition is complete before they gain the antlers of the fifth 
year. When the first trace of a snag appears on one beam of 
Cariacus virginianus, the dentition includes the full number, but 

there remain - milk molars much worn and ready to be shed. 

Perhaps the snag is developed before these are displaced. If so, 
the Cariacus is never a Subulo, but there can be little doubt that 
the young Blastocerus belongs to that genus before its adult char- 
acters appeal'. 

7. Leidy states * that certain Perissodactyl remains, contain- 
ing a foot of a horse, contained the teeth of a genus, Protohippus, 
which has the permanent teeth of Equus, and the deciduous 
dentition of Anchitherium. He observes : " The deciduous and 
permanent dentitions of both these genera are alike ; therefore 
the new genus is in early life an Anchitherium, and later in life a 
true horse." This is therefore a case of exact parallelism, always 
providing that the Protohippus has not added to its immature 
equine characters others in other parts of the body, which in- 
validate the identity. In the latter case it will still be an inter- 
esting example of the ''inexact parallelism." f 

* "Proceed. Acad. Nat. Sci," 1858, p. 7. 

f This is not a proper example of parallelism if, as some zoologists believe, the 


8. It is well known that the Cephalopoda form a number of 
series of remarkable regularity, the advance being, in the first 
place, in the complication of the folds of the external margins of 
the septa, and, in the second place, in the degree of involution of 
one or both extremities of the shell to the spiral ; third, in the 
position of the siphon. 

Alpheus Hyatt, in an important essay on this subject,* 
points out that the less complex forms are in many cases iden- 
tical with the undeveloped conditions of the more complex. 
He says : '' There is a direct connection between the position of 
a shell, in the completed cycle of the life of this order, and its 
own development. Those shells occuppng the extremes of the 
cycle" (in time), "the polar forms, being more embryonic than 
the intermediate forms, f The first epoch of the order is 
especially the era of rounded, and, in the majority of the spe- 
cies, of unornamented shells with simple septa ; the second is 
the era of ornamentation, and the septa are steadily complicat- 
ing ; in the third the complication of the septa, the ornamen- 
tation, and the number of species, about twice that of any 
other epoch, all combine to make it the zenith of development 
in the order ; the fourth is distinguishable from all the preced- 
ing as the era of retrogression in the form, and partially in the 

" The four periods of the individual are similarly arranged, 
and have comparable characteristics. As has been previously 
stated, the first is rounded and smooth, with simple septa ; the 
second tuberculated, and the septa more complicated ; the third 
was the only one in which the septa, form, and ornamentation 
simultaneously attained the climax of individual complication ; 

deciduous or temporary dentition is not a remnant of the primitive dentition, but is 
a later product of mammalian evolution. If it be a case of parallelism, it is inexact, 
because the genus Protohippus was discovered by the writer to have three toes, 
while Equus has but one. 

* " Memoirs Boston Soc. Nat. Hist.," 18G6, p. 193. 

f He adds here : "Although in regard to geological sequence and structural po- 
sition one of the extremes must be of higher geological rank." The " highest " ex- 
treme will be of higher geological rank, according to the complexity of structure and 
length of developmental scale, whether it come at the middle or end of the history 
of the class in time. If, as has been the case, so far as known, a decline has termi- 
nated the history of a class, its later forms arc zoologically lower than its older 
ones. Hence the adjective hifjh is only appropriate to types of the latter kind^ 
when used as synonymous with extreme. 


the fourth, wLien amounting to anything more important than 
the loss of a few ornaments, was marked by a retrogression of the 
whorl to a more tabular aspect, and by the partial degradation of 
the septa." 

I will here quote an entirely antagonistic statement of 
Bronn's,* as follows : " In the development of lamellibranchiate 
mollusks it is not possible to estimate the successional changes of 
one genus by those of another, though nearly related ; so diverse 
are the most significant relations in the manner of progress among 
nearest allies. Therefore, embryologic indications are throughout 
useless in classification, and it is necessary to keep carefully sepa- 
rate the statements of observations on development of a given 
species, and not transfer such facts to the history of another spe- 
cies for the purpose of completing it. "We can not even range 
these histories in conformity with family groups." For us this 
statement, though no doubt largely true, is an indication of im- 
perfection — first, of knowledge of true affinities of recent, but 
especially of extinct adults, and, second, of imperfection of knowl- 
edge of development. The position appears to be based on nega- 
tive evidence, while the opposing can and does stand on nothing 
but positive. 

/3. Examples of the Inexact Parallelism. 

1. The genera of the batrachian family Scaphiopodid^ form 
a series of steps differing a little more than as repressions or per- 
manent primary conditions in the development of the highest. f 
Thus two of the genera, which are North American, maintain 
their tubfe eustaehii and tympanum through life, while three 
European lose them at an early period. J The three European 
genera also advance beyond the larval character of the Ameri- 
can in the ossification of the basis of the xiphisternum into a 
broad style. Thus we have two series established, which differ 
only in the two characters named. Each shows its develop- 
mental steps in a similar manner, the European series extending 
further ; thus : 

* " Classen u. Ordnungen des Thierreichs," iii, p. 445. 

f See "Journal Academy," Philadelphia, 1866, on Arcifera. 

\ According to Bruch and Tschudi, in Pelobates. I have found traces of the 
eustachian diverticula, in a tailed Pelobates fuscus, whose body measured 1 in. 4 lin., 
from Mus. Peabody Institute, Salem, Mass. 


European. North American. 

1. Temporal fossa over arched. 

Cultripes. * * 

Temporal roof not ossified. 

2. Fronto-parietal bones ossified, involving 


Pelobates. Scapliiopns. 

3. Fronto-parietals ossified, distinct from 


* * (Unknown.) * * 

4. Fronto-parietals not ossified, distinct 

from derm. 

Didocus. Spea. 

In this case Didocus can not be said to be identical as a genus 
with an undeveloj^ed stage of Cultripes, since, while the cranium 
of the latter is in the condition of Didocus, it bears a long tail, 
and the limbs are but little developed. Xor is Didocus identical 
with the undeveloped condition of Pelobates, since both cranium 
and limbs of the latter are developed before the tail is absorbed. 
Nor is Pelobates identical with the undeveloped condition of Cul- 
tripes, since, while the cranium of the latter is that of the former, 
the limbs and tail are still larval. The same relations exist be- 
tween the other members of the family. The genus Scaphiopus 
is not an undeveloped form of Pelobates as to its auditory organs, 
for, when the latter is identical with the former in this respect, it 
bears otherwise entirely larval characters. Nor is Spea an arrested 
Scaphiopus, the relation being here precisely that between Dido- 
cus and Pelobates. Spea approaches more closely an arrested 
Didocus in all respects, but that when the latter possesses the au- 
ditory apparatus * of the former, it is a larva in limbs and tail, 
and that it loses this apparatus before reaching the other charac- 
ters of Spea. The relations of these genera, as compared with 
those of the Trachycephalus, Cystignathidse, and Bufo series, may 
be represented as follows : the lines represent the developmental 
scale of each. 

This is an example of the simplest case of inexact parallelism, 
as distinguished from the exact parallelism or identity. As the 
fauna of the present period is but a fragment, so the simple inex- 

* Tlio possession of cavum tympani and tuba Eustachii in the undeveloped con- 
dition of this genus is only assunied from its close relation to Pelobates. 



Eelations between the terms of 
the different series, Heterol- 
ogy or Remote Parallelism. 


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act is a more frequent relation than the 
exact, while the more complex inexact 
relation is still more common. The 
greater the inexactitude, the more fre- 
quently do such parallels occur till we 
have those of the most remote character, 
as, for instance, the parallelism between 
the different stages of the development 
of the mammal, in the structure of the 
heart and origins of the aorta, and the 
existing classes of vertebrates. The re- 
lation of these facts to the origin of 
genera will be noted hereafter. 

It will be borne in mind that in the 
Scaphiopodidse the generic types are 
identical for a long portion of their 
developmental history. (See figures on 
plate iv for the representation of these 
facts. ) 

3. In both Perissodactylous and Ar- 
tiodactylous Mammalia, certain types 
develop their family character of ca- 
nines at the earliest appearance of den- 
tition, others not till a comparatively 
late period of life (Equus), and the ex- 
treme individuals never produce them. 

3. Among cetaceans the genus Orca 
maintains a powerful and permanent 
series of teeth, which is an important 
generic character. In Beluga the se- 
ries is shed in old age, in Globiocepha- 
lus, or the Caing whales, they are shed 
at middle age, while in the Balffinidas, 
of which the absence of teeth is an es- 
sential character, these organs are de- 
veloped and absorbed during fcetal life 
(Eschricht). Though the condition 
of the teeth is not of systematic value 
in the two named intermediate genera, 
it is the important feature in the his- 
tory of progress to such value. 


4. Among the tortoises, the Testudinidge rapidly extend the 
ribs into a carapace, which fits closely the marginal bones, while 
equally early in life the elements of the sternum unite together. 
This is also the case with most Emydid« ; among whose genera, 
however, we find the transitional scale. In Dermatemys and 
Batagur the carapace is very late in attaining its complete ossifi- 
cation, while the plastron is early finished. In Chelydra, on the 
other hand, while the carapace is even more slowly developed, the 
plastron is never free from its larval fontanelles. In the marine 
turtles neither plastron nor caraj)ace is ever completed, while 
in the Trionychidse the marginal bones are also entirely unde- 

In order that this last illustration be a true one for the theory 
in question, as applied to i\\e families, these developmental char- 
acters should be the true distinctive features of these families re- 
spectively. This, as is well known, they are not. The Chelo- 
niidtB are characterized by the form of their anterior limbs, which 
is in an adaptive structure, while the Testudinidse similarly are 
distinguished by an extreme opposite modification of foot-struct- 
ure, adapted to an extreme difference of habit. Here there is an 
example of the co- working of both laws. Nevertheless, we only 
claim at present to show the developmental relation of genera of 
the same- family and the same series. This we see among the 

5. In the important character of the scutellation of the tarsi 
among the Passerine birds, the "boot" appears early in life in the 
highest Oscines, later in the lower, and does not appear at all in 
the majority. In respect to the still more important feature of 
the long posterior plates which appear very early in most Oscines, 
in the Myiadestes type * they appear late, the squamse remaining 
long, while the Clamatores never develop the plates, not advancing 
beyond the infantile squamous stage. 

6. It has been shown by Falconer that the genera of great 
Proboscidians form a remarkably regular and graded series, dis- 
tinguished by their dentition. These are Dinotherium Kanp, 
Trilophodon Falc, Mastodon Cuv., Pentalophodon Falc, Stego- 
don Falc, Loxodon F. Cuv., and Elephas Linn. In the first 
there are but two cross crests on the third molars, and a pair of 
permanent mandibular tusks ; in the second, three cross crests 

* Baird, " Review of Birds of North America." 


and mandibular tusks permanent in some males ; in the third, 
four cross crests and the mandibular tusks yariable ; in the fourth, 
five cross crests on the third molar ; tusks unknown. In Stego- 
don the mandibular tusks cease to appear, the crests of the third 
molar become more numerous, and embrace between them, in the 
bottoms of the valleys, a strong deposit of cementum. In Loxo- 
don the crests have the whole interspaces filled with cementum, 
while the same thing holds in Elephas, with a greatly increased 
number of cross crests, which become vertical laminas. The lami- 
nar character has become apparent from its rudimental condition 
in Stegodon. 

Now, these are stages of development, though not in a con- 
tinuous, single line. The shedding of the inferior tusks takes 
place earlier and earlier in the genera from Dinotherium, till 
they never appear in Stegodon. The molar teeth, it is well 
known, present, as they succeed each other from back to front, 
a regularly increasing number of transverse crests in the same 
species. Thus, in Trilopliodoii ohioticus the first molar presents 
but two, while the last presents six. The last molars of other 
genera present a very much increased number. What is it, 
then, but that the increased number of crests in the third molar, 
definitive of these genera, is an acceleration of growth ; the 
fourth in Trilophodon is structurally third in Mastodon, and the 
fourth of Mastodon being third in Pentalophodon ; the fourth 
of Pentalophodon becoming third in Stegodon, and so to the 
end ? This is confirmed from the proved fact of the disap- 
pearance of the premolars. They are fewer in Trilophodon 
than in Dinotherium, and are soon shed ; they are also early 
shed in Mastodon and Stegodon {insignis Falc. Caut.), and are 
not known to exist in the succeeding types ; the acceleration of 
succession of teeth has caused them to be entirely omitted. The 
young tooth of Elephas, moreover, is represented by a series of 
independent parallel laminae at first, which, when they unite, 
form a series of crests similar to the type of the genus ]\Iastodon 
and others of the beginning of the series. The deposit of cemen- 
tum takes place later, till the valleys are entirely filled up. Thus 
the relations of this part of the tooth-structure in the series are 
also those of the successional growth of those of Elephas, the ex- 
treme of the series. 

It would be only necessary to show that two distinct condi- 
tions, in any of these respects, occurred among the different indi- 


yiduals of the same species of any of tliese genera, to render a 
hypothesis of evolution a demonstrated fact.* 

It must be here observed that great size indicates little or 
nothing as to zoological rank. The greatest species are often not 
far removed in affinity from the least ; thus there can be but little 
doubt that elephants are not far removed from the rodents, and 
the rhinoceros is near the cony. Indeed, in the same genus the 
most extraordinary diversity prevails, for we have a very small 
elephant of Malta, and in the Miocene of Maryland a fin-back 
whale not so large as the new-born young of the fin-backs now 
living. Hence the . objection to the developmental hypothesis, 
based on the great size of the primal Selachians and Ganoids, has 
but little weight. 

7. Eathke has shown that the arteria ophthalmica of the 
higher Ophidians is originally a branch of the arteria cerebralis 
anterior, and that it later forms a connection with the arteria 
facialis. This connection increases in strength, while the other 
diminishes, until finally its supply of blood is derived from the 
facialis instead of the cerebralis. 

Eathke has also shown that the cerebral origin of this artery 
is continued through life in the three lowest suborders of the ser- 
pents, the Scolecophidia, Catodonta, and Tortricina ; also in the 
next succeeding group, the Peropoda. 

8. In most serpents the left lung is never developed ; in such 
the pulmonary artery, instead of being totally wanting, remains 
as a posterior aorta bow, connected with the aorta by a ductus bo- 
talli ; serpents without left lung being therefore identical in this 
respect with the embryonic type of those in which that lung 

9. Dr. Lespes states that the optic region of the brain of blind 
cave Coleoptera, examined by him is similar in structure to that 
in the blind larvae of Coleoptera, whose images possess visual 

10. t Those Saurians (Uromastix, etc.), in which the pre- 
maxillary region is produced into a uniform cutting edge, are 
furnished during early stages with a series of premaxillary teeth, 
which become gradually fused and confluent with the alveolar 
margin. Hence other Acrodonts are equivalent, in this respect, 

* This variability has since been shown to exist in species of the M. angmlidens 
type (1886). 

f See under section on Acceleration and Retardation. 


to the young of Uromastix, etc. The same thing occurs among 
the Scaroid and Labroid fishes. In this most natural family we 
find the majority of generic forms provided with a normal com- 
plete dentition ; in others (Chaerops, Xiphochilus, Pseudodax, 
etc.) the lateral teeth are gradually and normally replaced by a 
more or less cutting edge of the mandible ; and finally, in the 
Scarina and Odacina, the entire mass of teeth and jaws are coa- 
lesced, forming a beak with sharp cutting edges, the single teeth 
being still visible in the true Scarus, while they have entii'ely dis- 
appeared in adult Pseudoscarus and Odax.* Thus, in dentition, 
the adult Scarus is identical with not fully developed Odax ; 
Chaerops, with the teeth less confluent, equals a still younger stage 
of Odax, while those with distinct teeth are the same in this point 
as the embryos of the highest — Odax, etc. I venture to predict 
that here will be found a long series of exact parallelism, in which 
the different genera, resting exclusively on these dental characters, 
will be found to be identical generically with the various stages 
of the successively most advanced. 

11. Prof. Agassiz states that the absence of ventral fins is char- 
acteristic of an embryonic condition of the Cyprinodont fishes. 
The genus Orestias does not progress beyond this stage in this one 
point. Probably the genus will be found which will only differ 
from Orestias in the presence of ventral fins. If so, Orestias will 
be identical with an imperfect stage of that genus, if, as will ]5rob- 
ably be the case, the fins appear in the latter, after other struct- 
ures are fully completed. 

yy. Parallelism in Higher Groups. 

It is not to be anticipated that the series of genera exhibiting 
exact parallelism can embrace many such terms, since compara- 
tively few stages in the develoj^mental condition of the same part, 
in the highest, would bring us back to a larval condition, which, 
as far as we yet know, has no exact pa7'allel among existing genera. 
But it is to be believed that the lowest terms of a number of the 
most nearly allied of such series do of themselves form another 
series of exact parallelisms. 

Thus exact parallelism between existing genera of mammals 
ceases, with all characters which are larval or foetal, only prior to 

* Giinther on Ilatteria, "Philosophical Transactions," 1867, ii. I had already 
noticed the peculiar development in Uromastix, but not published it. 


the assumption of the adult dentition, since among the higher 
Mammalia at least we know of no genus which, however similar to 
undeveloped stages of the higher, never loses the milk dentition. 
It is nevertheless an important fact that among smooth-brained 
mammals, or many of them, but one tooth of the second series 
appears ; and inasmuch as smooth-brained forms of the higher 
orders have become extinct, it is not too much to anticipate that 
a type of permanent milk dentition will be found among the ex- 
tinct forms of the same high orders. 

As an example of exact parallelisms in series of series, I select 
the following : 

1. In the batrachian family Cystignathidae there are six groups 
or sets of genera. In the highest of these we have an ossified cra- 
nium and xiphisternum — i. e., in the Cystignathi ; in the Pleuro- 
demee the cranium is not ossified, thus representing the Cystigna- 
thi while incomplete ; in the Criniae the xiphisternum is cartilagi- 
nous, as well as the fronto-parietal region, being an equivalent of 
a still lower stage of the Cystignathi. From this simplest type we 
can find a rising series by a different combination of characters ; 
thus the Ceratophydes add an osseous cranium to the incomplete 
xiphisternum, while two succeeding groups diverge from each 
other at the start, the Pseudes loosening the outer metatarsus in 
their development to maturity, while the Hylodes add by degrees 
a cross-limb to the last phalange. The Ceratophrydes and Criniae 
are stages in the develoj^ment of these ; but neither one of them 
is a step in the development of the other. They are measured by 
adaptive characters purely. 

2. The whole suborder of the Anurous Batrachia, to which 
the above family belongs, the Arcifera, differs from the suborder 
Eaniformia by a character which distinguishes a primary stage of 
growth of the latter from its fully developed form. That is, the 
Eaniformia present, at one period of their development, a pair of 
parallel or over-lapping curved cartilages, connecting the procora- 
coid and coracoid bones, which subsequently unite and become 
a single, slender median, scarcely visible rod, while the bones 
named expand and meet. The first condition is the permanent 
and sole systematic character of the Arcifera.* 

Objection. — It may be objected, by those who have observed 

* This may be rcarlily understood by comparing my monograph of the Arcifera, 
"Jour. Ac. Nat. Sci.," Pliil., 1866, with Dugcs's work, or Gegcnbaur and Tarker's 
memoir on the Shoulder-Girdle. 


some of these developmental relations, that they are exhibited 
by certain single structures only, and not by whole organisms. 
These objectors must not forget that the distinctions of those 
groups, which alone we have in one geological period in a relation 
of near affinity, exists in single characters only ; and that it is 
therefore infinitely probable that the higher groups, when we 
come to know their representatives with the same completeness, 
will prove to be separated by single characters of difference also. 

3. The following table (pages 63 to 73) is introduced to illus- 
trate the relations of groups higher than the preceding. This is 
largely measured by the circulatory system, not only as to the 
class relations, but also as regards orders. In its less central por- 
tions it is, however, definitive of families at times.* (See also 
Plate I.) 

If the reader will compare the history of the development of 
vertebrates of any class or order, as those of Teleosts and the 
lizard by Lereboullet, of the snake and tortoise by Eathke and 
Agassiz, and of the bird and mammal by von Baer, he will find 
the most complete examples of the inexact parallelism of the 
lower types with the embryonic stages of the higher. A few 
points are selected as examples, from the histories included in a 
few of the columns of the table, and given at its end. 

Similar parallels may be found to exist in the most beavitiful 
manner between the adult anatomy and structure of the urogeni- 
tal apparatus within each class of the series taken separately, as 
indicating ordinal relationship. This dci^artment is, however, 
omitted for the present. 

As an example of the homologies derivable from the circula- 
tory system, and of the use of the following table, I give the fol- 
lowing relations between the types of the origins of the aorta, f 

The single ventricle of Teleostei is no doubt homologous with 
that of Lepidosteus, and that of Lepidosiren. The arteria vesicce 

* This sketch is not nearly complete, but is published in hopes of its being use- 
ful to students. It is compiled from the works of Meckel, Rathke, Barkow, Miiller, 
Ilyrtl, Briicke, Stannius, and others, in connection with numerous dissections. 

f Prof. Agassiz (" Contrib. Nat. Hist. U. S.," i, p. 285) states that the ven- 
tricle of the Testudinata " is not any more identical with the one ventricle of 
fishes than with the two ventricles of warm-blooded vertebrata ; for in fishes we 
find only one vessel, the aorta, arising from it, while in turtles both the aorta and 
arteria pulmonalis start together from it." We think this statement, which, if true, 
is destructive to the asserted homologies of the circulatory system, can not be sub- 
stantiated, for the reasons above given. 



Central Cikculatory System. 

Figs. 1, 2, fish. Figs. 3, 4, batrachian. Fig. 5, reptile. Fio. G, bird. 
Figs. 7, 8, human foetus. 


Figures and Diagrams of the circulatory centers of Vertebrata. Copied from 
Gegenbaur and His, mostly enlarged. 

Fig. 1. Diagram of the arterial arches of a Fish (species not given). 

Fig. 2. Head of an embryonic Teleostean, with the rudiments of the vascular 
system (diagrammatic). 

Fig. 3. Heart and arterial trunks of a larva of a Salamander. 

Fig. 4. Arterial system of the Frog. 

Fig. 5 Heart and arteries of an Ophidian (Boa). 

Fig. 6. Diagram of the arterial system of the adult Fowl. 

Fig. 7. Central circulatory system of Man ; foetus of the second month ; front 

Fig. 8. Same as Fig. 1, left side. 

V, ventricle of heart. 

a, auricle of heart. 

s V, sinus venosus of heart. 

h a, bulbus arteriosus of heart. 

a b, aorta branchlalis. 

1, 2, 3, 4, 5, arterise branchiales. 

V 1, 2, 3, venae branchiales. 

ao, aorta. 

ad, aorta dextra (right). 

a s, aorta sinistra (left). 

p, arteria pulmonalis. 

(lb, ductus botalli. 

ca, arteria carotis. 

cca, common carotid. 

Use, Isc, right and left subclavian arteries. 
7?m,/m, right and left innoraiuatearteries. 
cut, arteria cuticularis. 
occ, arteria occipitalis. 

V c, vena cardinalis. 

V d, right vena cava. 

V s, left vena cava. 

vi, inferior (posterior) vena cava. 

as, oesophageal artery. 

m, mesenteric artery. 

s, spiracular or branchial fissure. 

??, nostril. 

dc, ductus cuvieri. 

I, lingual artery. 


natatoricB, which is the homologue of the A. pulmonalis of air- 
breathers, issues in Lepidosteus from the last vena brancliialis, 
thus receiving aerated blood from the gills. In Lepidosiren it 
issues from the point of junction of two gill-less and two gill-bear- 
ing venm brancMales, thus receiving mixed blue and red blood, or 
blue blood altogether, when the branchise are not in functional 
activitv. In Proteus it issues from the last vena branchialis, 
where it receives the ductus botalU of the preceding vein, which, 
when the gill is inactive, becomes a gill-less aorta-bow, which brings 
it only carbonized blood, which it readily aerates in the swim- 
bladder, now become a lung. The ventricle is homologous with 
the preceding. In salamanders, where the substitution of the 
accessory gill arches by the ductus lotalli, converts the artericB 
and vencB IrancliiaUs into ''aorta-bows," the A. pulmonalis is 
given off from the posterior bow, and receives henceforth mixed 
blood. In the Anura the origin is the same, but nearer the heart. 
In Cseciliidge it approaches the heart so far as to issue from the 
extremity of the bulbus arteriosus, which is now divided by an 
incomplete septum, one half conveying blood to the aorta-roots, 
and the other to the A, pulmonalis. This septum was already 
preceded by a longitudinal valve with free margin in the Anura ! 
As if to meet the coming event, a trace of ventricular septum ap- 
pears at the apex within. There can now be no question of the 
homology of the ventricles of the gar, and of the Cecilia. But 
we have next the true Reptilia. The bulbus arteriosus is split 
externally, as it already was internally, but it is first represented 
in most tortoises by an adherent portion, one half being the now, 
to this point, independent arteria pulmonalis and the other the 
nearly split aorta-roots. There can, I think, be little question of 
the exactitude of the homology throughout. 

It is no less certain that the salamander * fulfills in its devel- 
opment the different stages to its permanent one, and is identical 
in each stage, in respect to this point, with the orders it represents 
at the time. This is true even of the long period during which 
it bears the long branchial appendages and contained arteries and 
veins which are not found in fishes ; it is then like the Protop- 
terus, which has hyoid venous arches and appendages of those 
arches at the same time. The tortoise f and Tropidonotus J are 
also identical in their successive stages with the tv^pcs already 

* Amblystoma. f Agassiz. t R:»thkc. 


enumerated, the external or appendicular branchial vessels being 
omitted, as belonging to the special seinal development of the line 
of air-breathing Anallantoidans. The division of the hulbus arte- 
riosus into three instead of two may indicate a case of inexact 
parallelism ; but, on the other hand, it may be that the pulmonary 
partition is completed a little before the aorta-root partition, thus 
passing through the batrachian permanent type. For explana- 
tions of inexactitude see under Part II. No doubt the batrachian 
type of hulbus arteriosus is passed by many serpents less extreme 
and specialized than the Tropidonotus. 

The aortic and pulmonary divisions of the bulbus in the Cae- 
cilia are not laterally placed, but one is dorsal and the other ven- 
tral, the one passing a little spirally to the right of the other. So 
the pulmonary division of the bulbus turns over to the right in 
the Anura. When the septum of the true reptiles appear, it rises 
on the anterior wall of the ventricle till it is seen, in Eunectes, to 
meet the partition between the arteria pulmonalis and aorta-roots, 
and we have at once the right and left ventricles of the bird and 
mammal structurally and functionally. Thus are the two ven- 
tricles of man the same as the one ventricle of the fish, merely 
divided by a septum.* 

In the fissure of the aortic bulbus, in the reptiles, a spiral turn 
is again given, and in Testudo the one aorta-root issues behind 
the other. In the crocodile the turn is still greater, and the 
right aorta-root issues to the left of the left root, and vice versa. 
In the birds we have lost the left root, and parallelism ceases with 
this change. In the Mammalia the right root turns to the left, 
so that in the comparison of these classes the rule of von Baer 
above quoted is true ; no mammal at present known is identical 
in a foetal stage with any fully grown bird, but with a foetus of 
the same, up to a certain point. But for both classes the paral- 
lelism of those below them holds true. 

But it is with the exact parallelism or identity of genera that 
we have to do in the present essay. That being established, the 
inexact parallelism between the modern representatives of higher 
groups follows by a process of reduction. 

* Agassiz, /. c, denies the homology of the ventricles of the turtle and mammal ■, 
but it appears to me erroneously. He says : " The fact that the great blood-vessels 
(aorta and art. pulmonalis) start together from the cavum venosum seems to prove 
that the two cavities in the heart of turtles, which are by no means very marked, 
do not correspond to the two ventricles in Mammalia and birds." 



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6. The Extent of Parallelism. 

Prof, de Serres and others have stated it as their belief that 
the lower '* branches" of the animal kingdom are identical with 
the undeveloped forms of the higher ; i. e., that the mollusk and 
articulate are not merely parallel with, but the same as the lower 
conditions of, the vertebrate. The works of various embryologists, 
as von Baer and Lereboullet, have shown this statement to be 
erroneous, "and founded on false and deceptive appearances." 
The embryos of the four great branches of the animal kingdom 
appear to be distinct in essential characters from their first 
appearance. But Lereboullet, who, in his prize essay, has 
compared with care the development of the trout, pike, and 
perch of the Teleosts, with that of a Lacerta among reptiles, has 
failed to point out characters by which the embryos of the two 
vertebrate classes essentially differ, for a considerable period. It 
is true that, as each and all of the species belong to widely differ- 
ent generic series, parallelism is of the kind to be called iiiexact 
or remote. But enough is known of embryology and paleontol- 
ogy to render it extremely probable that the historic predecessors, 
of the types whose embryology Lereboullet studied, formed a se- 
ries of parallels of the kind termed in this essay exact. 

Lereboullet states that a certain difference exists between the 
eggs of the fishes and those of the Lacerta. This is for us merely 
stating that the parents of the embryos differ, a fact which no one 
will contest. The same may be said of the elevated or depressed 
character of the surface of the vitellus on which the embryo re- 

Secondly, after the appearance of the embryo the Lacerta is 
furnished with the amnios and allantois ; the Teleost not. This 
is certainly neither a generic, ordinal, nor class character of the 
adult, for it is but temporary ; therefore, in generic, ordinal, and 
class characters the embryos of the Teleost and Eeptile are still 
identical. It is a physiological character, and not morphological, 
and therefore far the less likely to be a permanent one, even in 
embryos, under changed circumstances. The female of one of 
the species of Trachycei^halus inverts the skin of the back at one 
season of the year to receive her eggs, because she can not lay 
them in the water ; the other species of the genus do not. The 
next genus in direct morphological line possesses a single species 
whose female does the same for the same reason ; but the rela- 


tions of these species and genera are zoologically the same as 
though this modification did not occur. Many such instances will 
occur to many naturalists. It is not pretended that they are as 
important as the presence of the allantois ; but they constitute a 
character, no doubt, similar in kind, and entirely at the service of 
the needs of the gi'eat system of morphological succession. The 
same may be said of the vascular area of the Reptile. 

Lereboullet concludes his summary of the differences between 
the Teleost and Eeptile, up to the period of completion of the 
heart, by saying, " It is easy to perceive that all these differences, 
however important they may appear, are constituted by the acces- 
sory organs of the embryo, and do not modify the development of 
the latter, which progresses in reality exactly as in the fishes." 
He says the same previously, as to the relation of the same to the 
bird and mammal. 

We have, then, in the embryos of the lower vertebrates at a 
certain time in the history of each, an " exact parallelism " or 
identity with the embryonic condition of the type which pro- 
gresses to the next degree beyond it, and of all the other types 
which progress successively to more distant extremes. 

"We have, however, so far, every reason to suppose that the 
embryos of the other branches of animals never present an exact 
parallelism with those of the Vertebrata.* 

The embryo of the fish and that of the reptile and mammal 
may be said to be generically, if not specifically, identical up 
to the point where preparation for the aerial respiration of the 
latter appears. They each take different lines at this point. 
The fish diverges from the course of the rejotile, and proceeds 
to a different goal ; the shark does the same, but proceeds a 
shorter" distance ; while the Dermopter scarcely leaves the point 
of departure. No doubt, there have been types which never 
left this point and wJiose plan of circulatory system is identical 
with that of the embryo reptile and mammal. Such a type was 
only generically- different from the reptile or mammal which had 
only taken the succeeding step, provided other structures were 
not superadded. 

By comparing the development of types of different classes in 

* At about the time this was written the important papers of Ilacckel on his 
admirable Gastra?a theory were published, but had not reached the author. Haeckel 
shows the .approximate identity of all the types of embryonic development. (Xote, 


certain features which are only ordinal or generic in meaning, very 
erroneous conclusions may be reached by the inexact student as 
to the want of parallelism of classes to each other. Thus Eathke 
says of the development of the eye of the snake Tropidonotus, at 
a certain period, that it is far in advance of that of the mammal 
at the same stage. Here, says the objector, is a case where their 
parallelisms do not coincide ; the mammal is really similar to a 
younger stage of the reptile. 

But, in fact, the size of the eye is but a generic or family char- 
acter ; if the development of the lemur had been compared with 
the snake, the mammal would have been found to be in advance ; 
of the mole, much farther behind. If the snake selected were the 
purblind Atractaspis, almost any mammal would have been in 
advance ; if, on the other hand, the great-eyed Dijjsas, but few 
Mammalia would have been parallel to it. 

In a word, to find exact parallelism it is necessary to examine 
the closest allies. 

It is also of first importance to distinguish between the exist- 
ence of generic or higher characters, and theif condition under 
various circumstances of individual life. If a foetal or larval 
character be conserved through the adult life of a type, it will be 
of course adapted to the functions of mature age. Thus the un- 
developed character of the horns of the genus of deer, Kusa, are 
not accompanied with the marks of individual youth of the cor- 
responding stage of Cervus ; its individuals are fully grown and 
functionally perfect. The species of Hyla are not small and in- 
capable of self-preservation and reproduction, as is the corre- 
sponding stage of Trachycephalus ; they are functionally devel- 
oped. The student need not be surprised, then, if, when identity 
or exact parallelism is asserted, he finds some differences depend- 
ent on age and adaptation, for if he be an anatomist he need not 
be informed that a morphological relation constitutes types what 
they are, not a physiological. 


First. Of adult metamorphosis : 

The question has necessarily arisen, Have these remarkable 
relations between genera resulted from an arrangement of distinct 
generations according to a permanent scale of harmony, or have 
the same genetic series of individuals been made to assume the 


different positions at the same or different periods of the earth's 

Prof. Marcel de Serres proposed the theory of repressions of 
development to account for the existence of the lower groups of 
animals as now existing, an error easily exposed, as has been done 
by Lereboullet in his various important embryological writings. 
But little observation is sufficient to prove that a mammal is not 
a shark where it has five gill-arches or aorta-bows, nor a batrachian 
where it has three, or a reptile where it has the two aorta-roots. 
This has been already sufficiently pointed out by von Baer, who 
says there is " keine Kede " of such a theory as was afterward 
proposed by de Serres. Thus are true the rules propounded by 
this author. f 3. "Each embryo of a given animal type, instead 
of passing through the other given animal found, diverges still 
more from it." 4. " In the basis, therefore, the embryo of a 
higher animal type is never identical with an inferior tjpe, but 
with the embryo only of the latter." 

I think that I have already made some progress in proving 
that the near or true generic relationship is one of absolute devel- 
opmental repression or advance. Paleontology shows that fami- 
lies and orders, as now existing, were preceded in time by groups 
which are synthetic or comprehensive, combining the common 
characters of modern generic series. This process of synthesis 
must, it is obvious, if continued, result in the near approximation 
of the single representatives of the now numerous and diverse 
groups. There is every reason to believe that a backward view 
through time will show this to have prevailed throughout the 

* Some naturalists seem to imagine that the demonstration of the existence of 
intermediate types is only necessary to establish a developmental hypothesis. Thus 
Dr. Dohrn (" Ann. Magaz. N. Hist.," 1868), writing of his discovery of that most 
interesting genus, Eugereon, which combines characters of Neuroptera with those of 
Hemiptera, does not hesitate to say that it proves the truth of Darwin's theory. 
Now, it appears to me that a demonstration of the existence of a regularly graduated 
succession of types, from the monad to man, would be only the minor of a .syllogism 
without its major, in evidence for development, so long as the proof of transition 
of one step into another is wanting ; and the idea that such a discovery could estab- 
lish a developmental theory is entirely unfounded. Indeed, the reasoning in which 
some indulge— if we dare so call the spurious article— based on this premise alone, 
is unworthy of science. The successional relation of types, though a most important 
element in our argument, has been long known to many who give no sanction to 
the idea of development. 

f " Entwickelungsgcschichte," p. 224. 


Vertebrata and other branches, as we already can in part prove. 
And I have no doubt that the synthetic types, which represent 
modern orders, have existed in a generic relationship subordinate 
to the plan of the synthetic class, and that the latter have existed 
as genera only, of the type of the great branch. This is not ideal. 
We only have to look to our extinct ganoids, Archegosaurs, Laby- 
rinthodonts, Compsognathus, Archseopteryx, Ornithorhynchus, 
etc., to realize these facts. 

The first genera then formed a scale of which the members 
were identical with the undeveloped stages of the highest, and 
each to each according to their position. 

Such a series of antitypic groups having been thus established, 
our present knowledge will only j)ermit us to suppose that the 
resulting and now existing kingdoms and classes of animals and 
plants were conceived by the Creator according to a plan of his own, 
according to his pleasure. That directions or lines of development 
toward these ends were ordained, and certain laws applied for their 
realization. That these laws are the before-mentioned law of ke- 


The first consists in a continual crowding backward of the 
successive steps of individual development, so that the period of 
reproduction, while occurring periodically with the change of the 
year, falls later and later in the life history of the species, confer- 
ring upon its offspring features in advance of those possessed by 
its predecessors, in the line already laid down partly by a prior 
suppression on a higher platform, and partly, as above supposed, 
by the special creative plan. This progressive crowding back of 
stages is not, however, supposed to have progressed regularly. On 
the contrary, in the development of all animals there are well- 
known periods when the most important transitions are accom- 
plished in an incredibly short space of time (as the passage of 
man through the stages of the aorta-bows, and the production of 
limbs in Batrachia anura) ; while other transitions occupy long 
periods, and apparently little progress is made. 

The rapid change is called metamorphosis ; the intervening 
stages may be called larval or pupal. The most familiar examples 
are those which come latest in life, and hence are most easily ob- 
served, as in the insects and frogs. When, during the substationary 
period, the species reproduces, a constancy of type is the result ; 
when the metamorphosis only appears at the period of reproduc- 
tion, a protean type is the result ; when the metamorphosis is crowd- 


ed back to an earlier period of life, then we have another persistent 
type, but a new genus of a higher grade than its predecessor. 

In reviewing many examples everywhere coming under the eye 
of the naturalist, it is easy to perceive what would constitute a 
plastic and what a conserved condition of generic, or even of spe- 
cific form. 

As one or more periods in the life of every species is character- 
ized by a greater rapidity of development (or metamorphosis) than 
the remainder, so in proportion to the approximation of such a 
period to the epoch of maturity or reproduction, is the offspring 
liable to variation. During the periods corresponding to those be- 
tween the rapid metamorphoses the characters of the genus would 
be preserved unaltered, though the period of change would be 
ever approaching. 

Hence the transformation of genera may have been rapid and 
abrupt, and the intervening periods of persistency very long ; for 
it is ever true that the macrocosm is a parallel or repetition of the 
microcosm in matter and mind. As the development of the in- 
dividual, so the development of the genus. We may add : so the 
development of the whole of organized beings. 

These metamorphoses may be fitly compared to those in the 
molecular constitution of matter. The force of cohesion between 
the atoms of a vapor steadily increases with descending tempera- 
ture, and in a regular ratio, till a given point is reached, when a 
sudden metamorphosis to a denser or liquid condition takes place. 
Nor have we reason to believe, with regard to many substances, 
that there is any parallel relation between the temperature and the 
molecular constitution before or after the metamorphosis takes 
place. So, the temperature continuing to descend, the molecular 
character of the liquid remains unchanged until, the vis conserva- 
trix suddenly giving way at the ordained point, a soild is the re- 
sult. Thus, while the change is really progressing, the external 
features remain unchanged at other than those points, which may 
be called expression-points. 

Now, the expression-point of a new generic type is reached 
when its appearance in the adult falls so far prior to the period of 
reproduction as to transmit it to the offspring and to their de- 
scendants, until another expressioi-poinf of progress be reached. 

Thus a developmental succession does not so obliterate the lines 
drawn around Nature's types as to render our system ineffectual 
as an expression of them. 



The successional acceleration or retardation in metamorphosis 
may be best illustrated in certain tailless batrachians, by the fol- 
lowing tables. These are taken, it will be remembered, from the 
Bufonidae and HylidaB as examples of " exact parallelism " ; three 
are now added from the Eanidge and Discoglossida3. The case of 
" inexact parallelism " is that of the Scaphiopodidte. 

Whether they are cases of acceleration or retardation can only 
be determined by reference to the paleontology of the respective 
groups, or a careful comparison of times of metamorphosis. In 
the case of the Discoglossidse I suspect it to be retardation, as the 
highest genus is extinct. The others I shall arrange with them 
for temporary conyenieuce. AVere I dealing with a group of Ga- 
noids, I should imagine the process to be retardation, as this 
group is going out of existence. On the other hand, were they 
higher Osciue birds, we might imagine the case to be reversed. 

140th gen. 
120th gen. 
100th gen. 

80th gen. 

60th gen. 

40th gen. 

20th gen. 
1st gen. 

Series No. 1. 
Bombinator. . 
Alytes * 

No. 2. 

No. 3. 


e : 

e Pf : P 



. Osteocephalus. . . 

e Pf 

F : 

..Bufo sp. 

e. Pf F 

Ex : 

. Bufo sp. 

Pf : F 

Ex t 




?F : Ex 


..Peltaphryne . 

? : : 

P ■-* t3 2 t3 •-* '^ 

j; 2. 2. 05 o 3 3 

2 t-ij3 p o OD 


™ <* ~, 

3 iL. 





to a 






Pig. 3. 



T F 

T F Ex 

T F Ex 









No vom. teeth. 
< Sometimes " 
Always " 

Points not attained. 
Fig. 4. 

* A parotoid gland of small siize is added here, but is not generic as compared with Bom- 
binator, as the latter has collections of crypts on the same region and over the body. 












Tail lost (re- 

Temp, roof 

Ossif. front 



; I ! 

! i i 

i •! i 

;=§ i 
\ I 1 

: i I 

1 1 ; 

1 ! 

: 1 

i < 

; t 


1 i 



















! '■ 

1 M M A 


Mi A 


3 : I-. 

1 is 


MM -A- 


ana Or. 
Or. III. 









3 i - 




















Reproduce. "2 
Prefrontals unit. "S 

Ethmoid oss. ^ 

TaU lost S 

Frontals ossif. g 






In the preceding diagrams each horizontal column represents 
the life history of the individuals of each genus. The line of 
dots, stars, etc., represents the same developmental stage of each, 
as it appears earlier or later in the life of the individuals. The 
point of crossing the breeding period is that at which the charac- 
ter is rendered permanent. When the change falls on this period 
the character is not generic, as in Ixalus, Fig. 4. The period of 
losing the tail, like that of breeding, is represented as occurring at 
nearly the same time in the history of every genus, as it is gener- 


ally seasonal. Yet this is not always so, and, like tlie other char- 
acters, has most likely had its period of shifting. Compare differ- 
ence of time of development, for instance, of the frontal and pre- 
frontal bones in Figs. 3 and 6. The comparison of the adult 
stages of the less developed genera, at the tops of the columns, 
with the larval conditions of those more fully developed, may be 
traced in the absence of characters which appear in the latter. I 
have convinced myself of the accuracy of the above relations by 
the examination of many skeletons and wet preparations of adults 
and larvae. 

Tlie diagrams* are representations of nature, and not ideal 
sketches. It is to be noted as remarkable that the advance 
throughout so many diverse groups is in the same direction, viz., 
to complete or excessive ossification of the cranium ; and this 
identity of progress might be readily shown by adding other char- 
acters, were it not that the tables would become too complex for 

Has any such transition from genus to genus ever been seen to 
occur 9 

It must of course take place during the life of the individuals 
of a species, and probably at different times during the lives of 
different individuals, dependent on their relative vigor. In our 
view, ordinary metamorphosis is such a change, and we have 
stated its bearing in this form, that " every character distinguish- 
ing suborders, families, and genera is to be found among the indi- 
viduals of some species, living or extinct, to mark new varieties 
or stages of growth." 

a. The Developmental Relation of Qeneric to Specific Characters. 

For the relation of the law of retardation and acceleration to 
specific characters we will look to development again. While the 

* Notes on the diagrams : Fig. 4. Polypedates is here restricted to P. maculatus 
and P. quadrilineatus. The other species are referred to Rhacophorus, which has 
not hitherto rested on any proper basis ; the asserted character — the palmation of 
the hands — being one quite graduated from species to species among Hylte. 
Chiromantis, Peters, is referred to the same, as its character is not strongly 
marked and is visible in other species. For similar reasons Lcpfomantis is referred 
to Ixalus. 

Fig. 6. In each of series ii and iii, two series are mingled for the sake of com- 
paring the structures of the prcfontal bones. Thus Heteroglossa, Staurois, Ilylo- 
rana and Trypheropsis are one series, and Hyperolius and Hylambates members of 


young of Trachycephaliis are successively different genera, they 
preserve most of their speciGc characters so as not to be mistaken. 
Agassiz says of the development of the North American turtles,* 
" I do not know a turtle which does not exhibit marked specific 
peculiarities long before its generic characters are fully devel- 
oped." The same thing can be said of the characters of our sala- 
manders, whose specific marks appear before their generic or even 
family characters. I suspect that this will be found to be a uni- 
versal law. 

It also follows, if a developmental process, as proj^osed, has 
existed, that at times the change of generic type has talcen place 
more rapidly than that of specific,^ and that one and the same 
species {if origin he the definition) has, in the natural succession, 
existed in more than one genus. 

Apart from any question of origin, so soon as a species should 
assume a new generic character it ceases, of course, to be specific- 
ally the same as other individuals which have not assumed it. If 
supposed distinctness of origin be, however, a test of specific 
difference, we shall then have to contend with the paradox of the 
same species belonging to two different genera at one and the 
same time. 

It follows, therefore, in our interpretation of nature, that 
groups defined by coloration alone are not to be regarded as genera, 
as is done by some ornithologists and entomologists. They are 
simply groups of species in which distinctive generic characters 
had not appeared up to the period of reproduction. Inasmuch 
as in development certain specific characters appear first, among 
them part or all of the coloration pattern, it is obvious that the 
latter do not belong to the generic category. The employment of 
such characters, then, in this sense, is only to commence reversing 
the terms generic and specific, and to inaugurate the process of 
regarding each species as type of a separate genus. 

yS. Of Probable Cases of Transition. 

Thus the transition between the toothed and edentulous con- 
ditions in Cetacea takes place in the ordinary growth of the indi- 
viduals of the genus Globiocophalus, and the transition between 

* Contrib. " N. ITlst. United States," i, p. 391. Xote. 

f See "Proceedings Academy," Philadelphia, 1867, p. 86, where I observe that 
generic characters are probably less inherent than specific. 


the ossified anJ non-ossified types of Chelonia occurs during tlie 
life of the individuals of tlie genus Dermatemys. 

But, in attempting to demonstrate this proposition, we must 
bring forward facts of another kind. The anti-developmentalists 
are accustomed to jjut such changes aside, as part of the necessary 
history of established types ; hence we will not appeal to such. 

1. The frog Ranula affinis, of South America, was described 
by Peters as probably a climatal variety of European Rana tempo- 
raria. In this he is supported by the fact that the specific char- 
acters do not differ more than would characterize it as a local 
variety, were it an inhabitant of Europe. But I have found that 
it differs generically in tlie non-ossification of tlie ethmoid bone, 
as has been confirmed by Steindachner, and rej)resents an embry- 
onic condition of the same bone in Eana. It is in fact an unde- 
veloped Rana. That this is a true genus is confirmed by many 
specimens, by additional species, and by the fact that the allied 
genus Trypheropsis, embracing three sjiecies in the same region, 
differs in the same way from the otherwise identical genus of the 
Old World, Hylorana. 

2. The South African Saurians, Gliammmura anguina and 
Mancus macrolepis, are very closely allied in specific characters in 
all respects, though distinct. They have one imj^ortant ground 
of generic distinction : the latter has one pair of limbs less than 
the former. They are rudimental in Chamsesaura, and the disap- 
pearance in Mancus is but another step in the same direction. 
The difference in specific characters is of much less degree. 

3. In the genus Celestus there are numerous species, which 
range from a slender snake-like form with weak limbs, to stouter, 
strong-limbed forms with a more saurian build. Among these 
the Haytian G. plioxinus is well distinguished by form and color- 
ation. An allied genus from the same region is Panolopus, which 
in specific characters approaches the C. pJioxinus very closely, 
much more so than any Celestus (one species possibly excepted). 
But in generic characters it is distinguished by the loss of all its 
toes and the non-separation of nine plates on the end of the muz- 
zle. The genus Diploglossus, on the other hand, occupying a 
superior place on account of the division of the fronto-nasal into 
three, is, in specific characters (of D, monotropis) much closer to 
the stout Celesti than the species of the latter genus are among 

4. The Gronias nigrilalris is a Silurid, which in specific char- 


acters more nearly resembles the Amiiwus lynx, than the latter 
does the A. alhidus and many other species of the genus. The 
A. hjnx is found in the same streams. The important generic 
cliaracter, the absence of eyes, is, however, its constant feature 
(in three specimens known to naturalists, others to fishermen). 

5. The Cinclidium maximum, a large tree-toad of Brazil, re- 
sembles in all its characters the Centrotehna geograpliicum. The 
sjiecific differences between them amount to almost nothing, but 
both sexes of the former grow larger and are furnished with a 
generic peculiarity in tlie addition of some phalanges to the 

6. The Oporornis agilis, Baird, a North American bird of the 
Tanager family, resembles very closely, in form, color, and habits, 
the adjacent species of the adjacent genus Geothlypis. While its 
specific characters are thus very close to Geothlypis teplirocotis, 
it differs in the generic feature of a longer wing. By this it is 
associated, and properly so, with another species 0. formosiis, 
which has the general color and habits of species of Myiodioctes 
( Jf. canadensis), the next related genus. 

7. The following fact I give on the authority of Prof. Leidy, 
who will publish it in his forthcoming work on the extinct Mam- 
malia of Nebraska, etc. 

Three species of Oreodon occur in the Miocene strata ; tliey 
are a larger, a medium, and a small sized species. In the Plio- 
cene beds above them they are represented by three species of 
Merychyus, which are in all respects known, identical specific- 
ally with the three preceding. Each one may thus be said to be 
more nearly allied to the species of the other genus than to its 
fellow of the same genus, in specific characters. But each, on the 
other hand, differs from each in generic characters. The teeth of 
Merychyus are more prismatic, have longer crowns and shorter 
roots, approaching the sheep, as Oreodon does the deer.* 

* This phenomenon suggests an explanation on the score of adaptation, which the 
other cases do not. The existence during the later period of a tougher material of 
diet would increase the rapidity of wearing of the crown of the tooth, and require 
a longer crown and greater rapidity of protrusion. This necessitates a dimi- 
nution of the basal shoulder and shortening of the roots, producing the prismatic 
form aforesaid. The deer browse on forest foliage, which is more tender, while 
the Cavicornia graze the grasses, which contain, as is known, a greater amount of 
silex ; hence the more rapid attrition of the tooth. 

This may have been the case with the two extinct genera ; the different periods 


8. The Coreopsis discoidea T. and G., var. anomala, Gray, is, 
according to Mr. Aubrey Smith, much more nearly allied to Bid- 
ens frondosa than to other species of its own genus, and the latter 
is nearer to it than to other species of Bidens. It differs chieily, 
if not altogether, in the generic character : the barbs of the ache- 
nia are directed upward ; those of the Bidens downward. 

From these and many other such instances it may be derived : 
That the nearest species of adjacent genera are more nearly allied 
in specific characters than the most diverse species of the same 

9. While Taxodium distichum and Glyptostrohus europwus, 
conifers of North America and of Eastern Asia, respectively, are 
readily distinguished by generic peculiarities of their cones, in 
specific characters they appear to be identical.* 

Confirmatory of this proposition is the statement of Parker : f 
*'In tracing out the almost infinite varieties of the modifications 
of any one specific type of shelled Ehizoj^od, my friend Prof. 
Eupert Jones and I found that lihe varieties of distinct species are 
much nearer in shape and appearance than unlihe varieties of the 
same essential species." (It is not unlikely that species should 
here be read genus and variety species, though the latter may not 
fulfill the requirements in regard to distinctiveness observed 
among higher animals. In types like the Ehizopod, forms of this 
grade may not be really differentiated. Their enormous geo- 
graphical range would suggest this, if nothing else. ) 

Objection. — A class of objectors to the preceding explanation 
of the relations in question will ascribe them to hybridization. 
They have already done so to considerable extent among the 
Teleosts (see the writings of von Siebold, Steindachner, and 
Giinther). That hybrids exist in nature will be denied by none, 
but that they are usual or abundant is not a probable condition of 
a creation regulated by such order as ours is. The tendency to 
modify in given lines of generic series, if admitted, will account 
for many of the cases regarded as hybrids by the above authors, 
for it is to be remarked in many cases how the generic characters 

during which they lived may have seen a change from forest to prairie. (It is not 
intended to sugi^est that the species of the two genera arc necessarily of the same 
or any given number.) 

* See Meehan, " Proc. Amer. Ass. Adv. Sci.," 18G8. Newberry, " Ann. Lye," 
N. Y., 1868. 

\ " Transac. Zool. Soc," London, 1864, p. 151. 


are strikingly affected, and are chiefly used in guessing at the 
parentage. This is among Cyprinidse so much the case that there 
is scarcely an example of a hybrid between two species of the same 
genus brought forward, but often between species of different 

y. Ascertained Cases of Transition. 

This naturally suggests that, in accordance with the theory of 
acceleration and retardation, a transition can take place in the 
life history of species. Haye we any means of proving this sus- 
picion ? 

1. The genus Ameiva (Saurians of South America) has been 
composed of species of moderate size furnished with acutely tri- 
cuspid teeth. Teius, on the other hand, embraces very large spe- 
cies with the molars obtusely rounded and of the grinding type. 
These genera are generally held to be well founded at present. I 
find, however, that in Ameiva pleii, which is the largest species of 
the genus, in adults the greater part of the maxillary and mandib- 
ular teeth lose their cusps, become rounded, then obtuse, and 
finally like those of Teius. While young, they are true Ameivae. 
Strangely enough the A. pleii, from Porto Rico, acquires but 
three such obtuse teeth when of the size of the other (St. Croix) 
forms. In youth the teeth of all are as in other Ameivae. Here is 
a case of ti'ansition from one genus to another in the same species. 

2. In the important characters of the possession of branchiae, 
of maxillary bones, and of ossified vertebrae, the tailed Batrachia 
presents a series of a rising scale, measured by their successively 
earlier assumption. Thus Salamandra atra* produces living 
young, -which have already lost the branchias ; ;S'. maculosa living 
young with branchiae; Plethodonf produces young from eggs 
which bear branchiae but a short time, and do not use them func- 
tionally ; Desmogantlms nigra uses them during a very short 
aquatic life ; D. fusca and other Salamanders maintain them 
longer ; while Spelerpes preserves them till full length is nearly 
reached. Finally, species of Amblystoma reproduce while carry- 
ing branchiae, thus transmitting this feature to their young as an 
adult character. And it is a very significant fact that Spelerpes, 
which bears branchiae longest, next to Amblystoma, is associated 

* See Schreiber's " Isis," 1833, p. 527; Koelikcr, "Zoitsclir. f. wissensch. Zoolo- 
gie," ix, p. 464. 

f Baird, " Iconographic Encyclopaedia " ; Wyiuan, Cope. 


in the same zoological region with a genus (Necturns) which dif- 
fers from its four-toed form (Batrachoseps*) in nothing more 
than the possession of the osseous and branchial characters of its 
larva, in a permanent and rejDroducing condition. That this is a 
genus, to be one day converted into Batrachoseps by an accelera- 
tion of its metamorphosis, or that has been derived from it by the 
reverse process, I am much inclined to believe, f In supj^ort of 
this I quote the following examination into the time of change of 
the species of Amblystoma from my essay on that genus : J 

"The great difference between the different species, and be- 
tween individual species in this respect, may be illustrated by the 
following comparison between the size of the animals at the time 
of losing the branchise, so far as known, and that to which they 
ultimately attain. 


Size at loss of bkanchi^. 

Average full size, 





A. jeffersonianum, 




A. punctatum, 
A. conspersum, 
A. opacum, 
A. texense. 








A. niicrostomum, 




A. talpoideum, 
A. paroticum, 

A. tigrinum. 


[perhaps too large). 
V'S (not smallest). 
7 to 


8 to 10 



A. mavortinm, 


9-5 to 



A. mcxicanum, 

? branchiae persistent. 



The last species, though not uncommon in collections, is not 
known to pass through its metamorphoses in its native country, 
but reproduces as a larva, and is therefore type of the genus Sire- 
don of Wagler, Cuvier, Owen, and others. The larva of A. vna- 
vortium in like manner reproduces, but their offspring have in 
the Jardin des Plantes and at Yale College undergone an early 
metamorphosis. * 

* See Cope, "Jour. Ac. Nat. Sci.," Phila., 1866. 

f Necturus differs from all true Salamanders in the possession of the os interca- 
lare of the skull ; the parallelism is therefore inexact. (Note, 1886.) 
X " Proceed. Academy," Phila., 1867. 

* Through the kindness of Prof. Dum6ril I have received both larvte and 
adult of the species here noted, and observed by him. The larva is, as he states, 
Siredon Uclienoides of Baird, while the adult is his Ambli/stoma nia»ortiuni, not A. 
tigrinum ( = luridum), as also supposed by Dum^ril. (Note, 1886. I now believe 
these forms to belong to one species.) 



Here is a case where all the species but two change their 
generic characters ; one changes them or not, according to cir- 
cumstances, and one does not change them at all. What are the 
probabilities respecting the change in the first set of species ? 

As we know from the experiments of Hogg, Dum^ril, and 
others that metamorphosis is greatly hastened or delayed by the 
conditions of temperature and light, what would not be the effect 
on such a protean si^ecies of a change of topographical situation, 
such as the elevation or depression of the land ? And I have no 
hesitation in saying that if the peculiarities of series of individuals 
of A. tigrinum and A. mavortium, in the respects above enumer- 
ated, were permanent, they would characterize those series as spe- 
cies, as completely as any that zoologists are accustomed to recog- 
nize. For the evidences on this head, see the discussions of those 
species in my monograph. 

The exj)eriments of Hogg, above alluded to, are as follows, as 
given by him la the "Annals and Magazine of Natural History." 

He placed a number of impregnated ova of frogs in vessels 
arranged at regular distances from the light, in a cave. The les- 
sening degrees of light were of co^^rse accompanied by a corre- 
sponding but much less rapid decline in temperature. The result- 
ing effects on the metamorphosis may be tabulated as follows : 














Larva free, 






Larva free, 






Larva free, 

Larva free. 



Larva very large, 





Metam. complete, 

Larva large, 

Larva large, 

Larva small. 



Metam. complete, 




Metam. complt. 




Metam. comp. 

3. The reproduction of some species of insects before they 
complete their metamorphosis is a well-known fact, and it is par- 
ticularly to the point that, in many of them, some individuals do 
attain to their full development, while the many do not. "West- 
wood says,* "Two British species of this family (the Keduviidje), 
Prostemma gnttuJa and Coramis suhapterus, are interesting on 
account of their being generally found in an undeveloped state, 
the latter being either entirely apterous or with the fore-wings 
rudimental, although occasionally met with having the fore-wings 

* Uhler informs me that Amyot's asserted color characters are not reliable. 


completely developed." "I think," says Spinola, "that the pres- 
ence of wings and their development dej^ends on the climate" ; and, 
in speaking of Oncoceplialus griseus, he says, " The influence of 
the northern climate appears to have arrested the development of 
the organs of flight. It will be seen that I have referred else- 
where that I have noticed that it is especially in hot seasons that 
certain species acquire wings, while the circumstance noticed re- 
specting the ordinary occurrence of winged specimens of Micro- 
coelia in the West Indies is confirmatory of the same opinion." 

4. It is now known that certain Orthoptera do not get through 
their metamorphosis in time for the period of reproduction, and 
hence never, or in rare instances only, develop more than a short 
distance beyond the pupa state. 

5. My friend P. R. Uhler tells me of an example among 
Hemiptera of the genus Velia. The species F. rivvlorum, Fab., 
and F. curreus,* of Europe, are only distinguished by the devel- 
opmental feature of the presence of wings in one, and their ab- 
sence in the other. Another species of the tropical region of the 
West Indies, Halohates americanus, Uhler, is furnished with 
wings, while its individuals, which occur abundantly in North 
America, have been generally supposed to lack them. Individuals, 
however, no doubt occur whose development is so far accelerated 
as to permit them to acquire wings before the period of reproduc- 
tion, since one such has been found by Uhler. 

These wing characters are in many cases generic, it appears to 
the writer ; and the fact that they differ, without corresponding 
specific differences, is important evidence as to the origin of the 

6. The females of the Lepidopterous genus Thyridojiteryx 
never develop beyond the pupa state, according to the same au- 
thority, before reproduction ; they are reproducing pupae, so far 
as the external characters concerned in metamorphosis go. In 
other words, the latter have been retarded, while the reproductive 
system and others have progressed. Now, generic characters are 
seen in the fii'st, not in the last. The influence of the males is 
sufficient to prevent more than a part of the offspring from being 
retarded in the same manner. 

I have selected a few of this class of facts which have come 
before my mind during the present writing, as drawn mainly from 

* On " Insects," ii, p. 493. 


my own experience. How many more of the same purport could 
be found by search through the great literature of science, or in 
the field of nature, may be readily imagined. I have no doubt 
that the field of entomology especially will furnish a great number 
of evidences of the theory of acceleration and retardation, espe- 
cially among the insects with active pupae. 

Finally, having already stated the law according to which these 
processes naturally take place, I quote the following significant 
language of Hyatt in the above quoted essay on the Cephalopoda, 
as approaching nearer to the "law of acceleration and retarda- 
tion" than anything I have found written. He says : 

" In other words, there is an increasing concentration of the 
adult characteristics of lower species, in the young of higher spe- 
cies, and a consequent displacement of other embryonic features, 
which had themselves, also, previously belonged to the adult peri- 
ods of still lower forms." 

The preceding propositions have been formulated as follows, a 
few additions being now made : 

I. That genera form series indicated by successional differences 
of structural character, so that one extreme of such series is very 
different from the other, by the regular addition or subtraction 
of characters, step by step.* 

n. That one extreme of such series is a more generalized type, 
nearly approaching in characters the corresponding extreme of 
other series. 

III. That the other extreme of such series is excessively modi- 
fied and specialized, and so diverging from all other forms as to 
admit of no type of form beyond it. f 

IV. That the peculiarities presented by such extremes are 
either only in part or not at all of the nature of adaptations to the 
external life of the type. J 

V. That rudimental organs are undeveloped or degraded con- 
ditions of the respective characters developed or obliterated in the 
extreme of the series. 

VI. That the differences between genera of the same natural 
series are only in the single modifications of those characters wliich 
characterize the extreme of that series. 

* St. Ililaire, Owen, Agassiz, Dum6ril. 
f Dana on " Cephalization " ; Leconte. 

X Owen on " Cetacea," "Trans. Zool. Soc," London, 1SG6, p. 44. Leconte on 
" Carabidaj," " Trans. Amer. Philos. Soc.," 1853, p. 364. 



VII. That the relations of the genera of a primary series are 
those of the different steps in the development of the individuals 
of the extreme genus ah ovo {vo7i Baer, Agassiz) (with sometimes 
the addition of special adaptive features ?). 

VIII. That the presence, nidi mental condition, or absence of 
a given generic character can be accounted for on the hypothesis 
of a greater rapidity of development in the individuals of the spe- 
cies of the extreme type, such stimulus being more and more vig- 
orous in the individuals of the types as we advance toward the 
same, or by a reversed impulse of development, where the extreme 
is characterized by absence or "mutilation" of characters. 

IX. And that, as the character of the genus at the period of 
re^^roduction of its species is that which is perpetuated ; 

X. So the character of the genus has been first inferior, then 
protean, and then advanced, as the metamorphosis has been by a 
retrograde movement in time, posterior to, at, or anterior to the 
period of rejoroduction. 

XI. That it therefore results that there is one primary struct- 
ural type involved in such a series of species, which is made to 
present, at any given period in its geologic history, that appearance 
of succession of genera ordained by Creative Power. 

d. 071 the Origin of Inexact Parallelism . 

The hypothesis can only be demonstrated in case of exact par- 
allelism. If proved in these, it readily accounts for the cases of 
inexact parallelism, which are of course in any single period vastly 
in the inajority. First take the case of simple inexact parallel- 
ism. A series of individuals of the genus Didocus undergo the 
metamorphosis of the cranial structure earlier and earlier in life, 
commencing by completing the ossification of the membrane of 
the fronto-parietal region in full age, until at last it becomes com- 
pleted as early as the period of reproduction. Heretofore the 
adult offspring have appeared during a long period, invariably 
characterized by the larval cranium ; but like now producing like, 
this development springs into new power, and the offspring ossify 
the cranial bones far earlier than their immediate predecessors ; 
in a word, the genus Pelobates has been created ! At this state of 
progress Didocus is an undeveloped Pelobates. 

Let us, however, suppose the "acceleration " of development 
of the cranial bones still to progress. The character appears now 
soon after the ordinary metamorphosis has been passed, and now 


a little before. The identity of Didocus with the undeveloped 
Pelobates is thereupon lost ! 

So may have been the relations between Pelobates and Cul- 
tripes. Pelobates was probably once identical with the undevel- 
oped Cultripes ; but the same acceleration has concentrated the 
characters more rapidly than the other larval stages, leaving Pelo- 
bates behind. 

This I conceive to be the explanation of this relation : when 
the i^arallelism is inexact by two steps, as in Spea to Didocus, by 
the obliterated ear and ossified xiphisternum. The continued 
concentration of characters has been carried to earlier stages till 
the identity exists in the adult state of neither one, but at a pe- 
riod of larval life of both, shortly preceding the adult period of 
the lower. The relations between the Amblystomidie and Pletho- 
dontido?, which I have elsewhere * jDointed out, have probably 
had their origin in this way. 

If we attempt to prove the identity of the modern Mammalian 
foetal circulation with that of the modern adult fish, we may find 
nearly an exact parallel in this respect, as it is the basis of class 
distinction ; but in other respects the identity will not exist, ren- 
dering the parallel inexact or remote. The structure of the ori- 
gins of the aorta is at one time identical with that of the shark, 
with one exception : in the former but four aorta-bows appear to- 
gether ; in the latter five. In the former the first disappears as 
the fifth comes into being. This is simply a continuation of ac- 
celeration. The first generalized representative of the Mammalia 
lost the first aorta-bow toward the latter part of its growth, and 
became the next genus in advance of the selachian. The fact 
that these bows do not appear exactly simultaneously, but rather 
successively, renders it necessary that in a regularly shortening 
period of possession of transitory characters, one such, as the ex- 
istence of the first aorta-root, should vanish before the appearance 
of a permanent, the fifth, in the more specialized types, where 
acceleration reaches its maximum. Tliis is indicated by the fact 
that in the Batrachia, where the acceleration has not attained so 
high a degree, the first and fifth aorta-bows co-exist for some time, 
though the first and second disappear before maturity. 

So also with the splitting of the bulbus arteriosus. As in the 
Batrachia, the pulmonary ductus communis only is to be sepa- 

* "Jour. Ac. Nat. Sci.," Phil., 1866, p. 100. 


rated ; the remaining bulbus is divided by a long valve or incom- 
plete septum, tracing the division of the aorta- roots. In the ser- 
pent (Rathke) this division is so accelerated as to appear at nearly 
the same time as the septum of the pulmonary duct. In the 
mammal, on the other hand, while the division of the aorta-root 
takes place as soon as in the last, the pulmonary septum is accel- 
erated so as to appear long before the first named. Hence, in the 
septa in the serpent, the singular anomaly seems to present of 
the mammal passing through the Batrachian stage, while the ser- 
pent, a nearer relative, does not.* If, however, we take the less 
typical serpent, we will find the aortic septum to appear a little 
later, thus giving the Batrachian type, and if we reverse the order 
of time, so that the succession becomes one of retardations, we 
will find the same known ratio will bring us to an identity under 
all circumstances. 

This, then, is the explanation of the divergence and want of 
"exact parallelism," which is observed in comparing the develoj?- 
mental histories of all tjrpes not most closely allied. It has not, 
according to our theory, ahvays been a divergence, but was at a 
prior epoch in each case a relation of "exact parallelism," the 
lower type a repressed higher ; the former identical with one of 
the stages of the latter. But the process which has produced this 
relation, continued, has of necessity destroyed it, so that the ex- 
act parallelism has always been a temporary relation, and one 
shifting over the face of the system. 


First. Comparison of the contemporary. 

Having now admitted a developmental succession of genera, 
and, second, that this has progressed more rapidly at certain times 
in the earth's history than any modification of specific forms, the 
hypothesis already broached naturally comes up : Has such trans- 
formation of types, generic or higher, tahen place in any degree 
siinuUaneously, throughout a great number of species f An af- 
firmative answer to such a proposition is absolutely necessary to 
its acceptance as expressing the phenomena exhibited by geolog- 
ical succession of types. Let us try to answer the question put in 
a closer form. Have the same species been transferred from one 

* This is the way indeed in wWch it is stated by Rathke, " Entwickelungsge- 
schichte der Natter," p 164. 


geologic epoch to another by a change of generic form ; and has 
not the genus been transferred from one epoch to another under 
change of ordinal type, and as a consequence the same species ? 

As a reply I propose to render the affirmative of the first of 
these questions highly probable. 

Paleontology only will be able to answer this question conclu- 
sively, though, as we have abundant evidence that the relations of 
species to genera and other higher groups were the same then as 
now, we may look to the present status as furnishing important 
evidence on the subject. ^Ye are turned at once to the probable 
history of development in the separate zoological areas of the 
earth's surface. The question may be asked. Are the present zo- 
ological regions on an equal plane as to the geologic relations of 
their faunae, or are they related as the different subdivisions of a 
geologic period in time ? 

I have on a former occasion asserted that the latter of these 
propositions was true.* 

a. Of Homologous Groups. 

Naturally following the admission of a developmental succes- 
sion of organic beings is the question of its relation to the differ- 
ent surfaces of land and water on the earth. The following con- 
siderations bear on this subject. 

Among the higher groups of animals can be detected series 
''homologous" on the same principle as the alcohols (? com- 
pound radicals) and their derivatives ; and the component types 
of each can be, and have been in many instances, shown to be 
"heterologous," as are the ethers, mercaptans, aldehydes, acids, 
etc. Among Mammalia two partly homologous series have been 
pointed out, Implacentialia and Placentialia ; possibly such are 
the types Altrices and Prsecoces among Aves ; of a lesser grade 
in this class are the parallel series of Pullastrae and Gallinae, of 
Clamatores and Oscines. Among tortoises I have alluded to the 
Pleurodira as compared with the remainder of the order, already 
parallelized by Wagler ; and, of lesser grades, the series among 
Lacertilia of Acrodonta and Ignania, parallelized by Dumeril and 
Bibron, and of Teidai and Lacertidae, compared by Wiegmann. I 
have discovered a full parallelism between the Eaniform and Arcif- 
erous Anura. It is carried out between the Characini and a group of 
remaining Physostomous Fishes, perhaps not yet well defined ; it 

*0a "Arciferous Anura," " Journ. Ac. Nat. Sci.," 1866, p. 108. 


is exhibited between the orders Diptera and Ilymenoptera among 
insects. None of these comparisons can be allowed, of course, 
without the most searching anatomical and embryological analysis. 

This heterology is what Swaiuson and others called "analogy" 
as distinguished from affinity. It gene7'ally relates genera of dif- 
ferent zoological regions. Mimetic analogy, on the contrary, re- 
lates genera of the same region ; it is a superficial imitation which 
has occurred to critical biologists, and is of much interest, though 
as yet but little investigated. It has as yet been observed in ex- 
ternal characters only, but occurs in internal also ; it has been 
accounted for in the first case by the supposed immunity from 
enemies arising from resemblance to well-defended types. No 
such explanation will, however, answer in the latter case. I be- 
lieve such coincidences express merely the developmental type 
common to many heterologous series of a given zoological "re- 
gion " ; this will be alluded to a few pages later. 

We naturally inquire. Is there anything in the food, the vege- 
tation, or the temperature to account for this apparent diversity 
in the different regions ? Are there not carnivora, herbivora, 
seed-eaters, insectivores, and tree-climbers, where game and grass, 
seeds and insects and forests grow the world over ? We answer 
undoubtedly there are, and these adaptations to food and climate 
are indeed as nothing in the general plan of creation, for every 
type of every age has performed these functions successively. 

3. Of Heterology.'^ 

This relation will be exhibited by a few examples from groups 

known to the writer, commencing with the Batrachia anura. 

Raniformes. Arcifeki. 

External metatarsal free. 

Aquatic. Rana. Pseudis. 

Metatars. shovel. Hoplobatrachus. Mixophyes. 

External metatarsal attached. 

Feet webbed. 
Metatars. shovel. Pyxiccphalus. Tomopterna. 

* Some of the cases below cited as heterology I believe to be truly of this char- 
acter ; but some others are probably not such, but are merely series of genera pre- 
senting similar structural peculiarities as consequences of the operation of identical 
laws. I would place under this head, and withdraw from the homologous class, the 
families of Lacertilia Leptoglossa, Diploglossa, and Typhlophthcdmi, those of the Old 
and New World Quadntmana and those of Cephalopoda. These distinct modes of 
origin of corresponding forms have been recently termed, by Lancaster, homogeny 
in the case of homologous groups, and homoplassy when the imitative types are on 
distinct lines. (Ed. 1886.) 


,■-".- ^-c. 

■ :-^<^-^r.t:r>y 





Figures of Lizards of the family Iguanidte to be compared with a homologous 
series of Agamidfe represented in Plate lla. The species are : 

Fig. 1. Basiliscus p/umifrons Cope, Costa Rica. From Cope. 

Fig. 2. Iguana tubercidafa Linn., South America. From the " Standard Natural 

Fig. 3. Crotaphylus wislizeni B. G., Sonoran Region of North America. From 

Fig. 4. Phymaturus palluma Grav., Chili. From Bell. 

Fig. 5. Phrynosoma cornulum Harl., Texas. From " Standard Natural History." 



Figures of Lizards of the family Agamidas which form a homologous series with 
the Iguanidae represented on Plate II. 

Fig. 1. Lophura amboinensis Schloss., Amboina. From Wagler. 

Fig. 2. Physignathus mentagcr Giinther, Siam. From Giinther. 

Fig. 3. Liolepis bcUii Gray, China. From Dumeril and Bibron. 

Fig. 4. Uromastix spinipes Cuv., Arabia. From Guerin. 

Fig. 5. Moloch horridiis Gray, Australia. From " Standard Natural History." 



Arboreal; vom. teeth. 

" no « " 


" spurred, 


Feet not webbed. 




Comparing the genera in a general physiological sense, we may 
parallelize further. 

Aqviatic, with digital dilatations. 


Arboreal : cranium hy- ) t> , , , 

' 4. ^ [ Polypedates. 

perostosed. ) •' ' 

" cranium free. Ehacophorus. 



j Hyla. 

I Agalychnis. 

The same kind of parallels exists between the primary groups 
of the Testudinata, as follows : 

Crtptodira. Pleurodira. 

Five complete pairs of bones across the plastron. 

Pleurosternidae. Stemothaeridae. 

Four pairs of bones across plastron ; not more than two phalanges on all toes. 

Testudinidae. Pelomedusidae. 

Three phalanges on most digits ; 
Zygomatic arch ; no parieto-mastoid. 

Emydidae. PodocnemididaB. 

Temporal fossa over-roofed by parietal. 

Macrochelys. Podocnemis. 

No zygoma ; a parieto-mastoid arch. 

* * * Hydraspididae. 

If we compare the peculiarities of generic structure merely 
with reference to their adaptation to the animals' habits, we will 
see the following : 

Feet reduced for terrestrial progress. 

Feet normal. 

Anterior lobe of sternum movable. 

Anterior lobe fixed. 
Neck very elongate. 

Neck shorter ; aquatic. 
Temporal fossa open. 



Emvdidae in gen. 

Temporal fossa over-roofed. 



The parallels between the genera of the American Iguanidae 
and the Old World Agamidoe are similarly quite close. They are 
shown on Plates II and II a. 



Abdominal ribs. 



* * 

No abdominal ribs. 

Ribs creatly prolon!?ed into a lateral wing. 

* *. Draco. 

Ribs not prolonged. 

Arboreal types, generally compressed. 

A dorsal and caudal fin supported by bony rays. 

Basiliscus (no fern, pores). Lophura (pores). 
No vertebral fin. 

No femora! pores. 
Form slender, scales in Calotes. [ 

equal series. Bronchocela. J 

Form elongate ; eyebrows 

elevated, tail compressed. Gonyocephalus. 
Form stouter, scales less 

regular. Hypsibates. 

Femoral pores. 
Low crested; small hyoid 

disk. Brachylophus. 

High crested ; large hyoid 

disk. Iguana. 

Tail with spinous whorls. Cyclura. 

Terrestrial types of flattened form. 

Femoral pores. 
Tail with whorls of spiny 

scales. Hoplocercus. 

. Tail long, simple ; scales 

small. Crotaphytus. 

Tail simple, scales large. Sceloporus. 

No femoral pores ; preanal pores. 

Tail with whorls of spines. * * Stellio. 

Tail simple, not elongate, 

ear open. Proctotretus. Agama. 

Neither femoral nor anal pores. 

Much flattened, tail short, scales irregular. 

Phrynosoma. Moloch. 

I Phrynocephalus. 
( Megalochilus. 




* * 


* * 

Ear exposed. 
Ear concealed. 

(Doliosaurus, s. g.) 

A similar parallel may be drawn between the American Teidse, 
and the Old World Lacertidae, and in fact between all the families 
of the Lacertilia Leptoglossa. I have added to these for compari- 
son two families of the Typhlophthalmi. Each family embraces 
one or more series, and these exhibit a remarkable similarity in 
the relative development of the limbs and digits ; among the 
higher gronps the parallelisms lie in the arrangement — as greater 
or less separation — of the head shields. The Scincidse are cosmopo- 
lite ; the Gymnophthalmidae, which have the eyelids of their foe- 
tus, are Australian ; the Sepsidae, either larval or senile in head 
shields, are mostly Ethiopian. 



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The first comparison of these groups was made by Wiegmann 
(Herpetologia Mexicana), who employed, however, only the Scin- 
cidae and Lacertidae, and could not include the mauy types made 
known since his day. 

From the class Aves I have selected only the homologous series 
of the Clanatorial and Oscine Passeres. Naturalists more fully 
acquainted with the genera could probably increase the examples 
of heterology largely. Each group furnislies us with carnivo- 
rous, insectivorous, and frugivorous forms ; each with walkers, 
climbers, and sedentary genera ; each with butcher-birds, thrushes, 
warblers (not in song !), wrens, and fly-catchers. Each and all of 
these types are teleologically necessary to any country complete in 
the wealth of nature, and to each geological period. 

Clamatores. Oscines. 

I. Tree-climbers, with long hind toe and tail feathers stiflfened and acute. 

Dendrocolaptidw. Certhiidoe. 

II. Terrestrial in part, with the tertials as long as the primary quills. 

Geohatidce. Motacillidcp.. 

III. Tree-perchers with hooked bill, graduating from powerful to medium and 

Formicariidce Turdidce. 

Thamnophilus. Bill strongest, hooked. Lonius. 

Formicarius. " moderate. Turdus. 

Formicivora. " weak. Bylvia. 

Rhamphoccemus. " slender (wrens). troglodytes. 

IV. Fly-catchers with flat bill and weak legs ; wait for their prey and take it on 
the wing. 

TyrannidcB. Muscicapa et aif . 

V. Flat-billed berry and fruit eaters. 

Cotingidce. BombycillidoB. 

From the Mammalia the well-known series of the Marsupialia and Placentialia 
may be chosen. 

Placentialia. Marsupialia. 

I. Toes unguiculate, in normal number ; sectorial teeth ; i. e., one or more molars 
with one or no internal tubercles ; canines strong : 

Carnivora. JSarcophaga, 

I. Digitigrade. 
Toes 5 — 4. 

Ti'ue molars f (upper incisors more numerous in some). 
Amphicyon. Thylacinus. 

II. Plantigrade ; molars tubercular. 
a. Posterior molars ^. 

* * Dasyuridae. 

aa. Posterior molars |. 
TJrsidse. * * 

II. Toes unguiculate ; molars with more than one row of pointed tubercles ; canines 
weak or none ; incisors large. 



Inscdivora. Entomophaga. 

a. Tubercular molars |, toes 4 — 5. 
Tail naked. 
Gymnura. Didelphys. 

Tail hairy. 
Cladobates. Myoictis 

IV. Molars with transverse crests, no canines ; tusk-like incisors ; pairs of limbs of 
similar proportions. 

Probosddia. Diprotodontidce. 

Two inferior incisors ; molars with two cross-crests ; size huge. 
a. Two rudimental lateral incisors above. 

* * Diprotodon. 

aa. ? One pair of incisors only above ; a trunk. 

V. No canines ; two pairs of cutting incisors. 

a. Three true molars. 
Rodentia. * * 

aa. Four true molars. 

* * Rhizophaga. 

The parallels are in this case very imperfect in details, and but 
few worthy of the name can be made. They are, however, illus- 
trative of a remote heterology, sufficiently remarkable to have 
claimed the notice of naturalists for many years.* I also have 
little doubt but that future paleontological discoveries will in- 
crease the number of parallels, f and bring to light truly heterolo- 
gous generic terms of the Marsupial series. Predictions of this 
kind have been on many occasions fulfilled (e. g., some of D'Or- 
bigny's among the Cephalopoda), and I look with confidence to 
the ultimate demonstration of that heterology here which has 
been already seen in the Batrachia and Reptilia. 

The homologous groups of the Catarrhine and Platyrrhine 
Quadrumana are measured as follows : 








Tail short. 
Long tail. 



Thumb developed. 
Thumb rudimental. 



Thumb none. 





* We owe very many observations on the Marsupials to Owen. 

f The extinct carnivorous family of the Nimravidae which forms a homologous 
series with the cats (Felidae) was discovered by the writer some years after this was 
written. (Ed. 1886.) 


I append two homologous series, represented by the Nautilea 
and the Ammonites of the Tetrabranchiate Cephalopoda, which 
are distinguished, the first by the simple septa and the siphon 
central or marginal ventral ; and the second by the complex and 
folded septa and siphon central or marginal dorsal. The parallel- 
isms have been noted by Barrande, Bronn, and many concholo- 
gists, who can furnish a much more full table than the following, 
from the most recent sources : 

Nautili. Ammonites. 

A. The shell straight, unwound. 

Orthoceras. Baculites. 

B. The shell more or less curved or wound. 
a. Simply curved. 

Cyrtoceras, } Toxoceras. 

Fhragmoceras, ) 

aa. A more or less straight portion, folded on the remainder. 
/3. Folded portion in close contact with remainder. 
Ascoceras. Ptychoceras. 

Pli. Folded portions not in contact. 
? ? Hamites. 

aaa. One extremity spirally wound, the volutions not in contact. 
/3. Extremity of the shell prolonged beyond the wound portion. 
Lituites. Ancyloceras. 

/3/3. Extremity not prolonged in a line. 
y The spiral flat. 
Gyroceras. Crioceras. 

yy. The spiral elevated (heliciform). 
Trochoeerus. Turrilites. 

aaaa. Spiral turns of the shell in contact. 
p. Extremity prolonged in line beyond the spiral. 
* * Scaphites. 

/?/?. Extremity not prolonged beyond spiral. 
Nautilus. Ammonites. 

We may now consider the question of the origin of these higher 
groups. In the first place, we must lay down the proposition that 
the characters which constitute groups ^' higher ^^ in the compari- 
son of rank (we do not of course mean higher in the same line, as 
we say higher genus in a family, or higher order in a class) are 
such solely from their being more comprehensive, or present 
throughout a greater range of species. 

What is true, therefore, in respect to characters of genera, is 
likely to be true in respect to characters of higher groups, such 
as we have been considering in the preceding pages. Believing, 
then, that a new genus has been established by the transition of a 
number of species of a preceding genus in order, without neces- 
sary loss of specific characters, I think the same process may have 
established the suborders and orders in question. That is, that a 
large number of genera have near the same time, in past or p res- 


ejit geological history, passed info another suborder or order ly 
the assiwiption or loss of the character or characters of that to 
or from lohich they loere transferred, and that without necessary 
loss of their generic characters. 

I will cite a probable case of this kind, the facts of which I 
have already adduced. 

It has been shown above that the genera of six of the fami- 
lies of the Batrachia anura form series characterized by the suc- 
cessive stages of ossification of the skull, terminating in a der- 
moossified condition, with over-roofed temjjoral fossse. That in 
nearly all the other families similar relations between genera exist, 
but are nowhere carried so far. The character attained by all 
the first series is now only generic ; but should all the genera of 
each of the six families assume this character in time, as is neces- 
sary in accordance with a development hypothesis, it would at 
once possess a new and higher importance, and would become or- 
dinal or otherwise superior. It would define a series homologous 
with all those types which had not attained it. This character 
of the over-roofing of the temporal fossae has actually attained a 
family significance among the Testudinata^ — e. g., as defining the 
marine turtles ; and similar characters are found by Owen to 
characterize the Labp-inthodontian order of Batrachia.* 

Agassiz has pointed out a similar and more extended case, in 
the Heterocercal and Homocercal ganoids. Had we not so many 
of the closest approximations between members of these groups, 
they would stand in the systems as two great homologous series, 
with their contained heterologous genera. As it is, these heter- 
ologous terms or genera are evidently so nearly allied that Agassiz, 
in the " Poissons Fossiles," has thought it best to arrange the latter 
together, thus instituting a system transverse, as it were, to the 
other. This may be necessary, since Kolliker points out transi- 
tional forms, and perhaps certain types may have begun to aban- 
don the heterocercal form near the period of reproduction, pro- 
ducing offspring somewhat protean in character, preparatory to 
an earlier appearance and consequent permanence of the homocer- 
cal type. This is to be derived from the history of the metamor- 
phosis of Amblystoma. 

In the same manner the development of the convolutions of the 
brain does not define groups of the highest rank, since it pro- 

* The roof here alluded to by Owen includes some two distinct bones not known 
in the arch of the Anura, and therefore different. 


gresses chiefly during the later periods of embryonic life, and is 
therefore a "developmental character." Owen has endeavored to 
distinguish the j)rimary divisions of Mammalia by the character 
of these convolutions, whereas they really define only the sub- 
groups of the orders. For we have Lissencephalous (smooth- 
brained) monkeys — certain lemurs — and smooth-brained Eumi- 
nants — i. e., the extinct Brachyodon and Anoplotherium, accord- 
ing to Lartet and Gratiolet. The lowest types of the existing 
smooth-brained Mammalia, including especially those with no 
or rudimental corpus callosum, the Marsupials, are also distin- 
guished by the non-development of the deciduous teeth * (except- 
ing one jiremolar). If now, through some toj)ographical change, 
the whole series of Mammalia between the smooth-brained and 
convolute-brained were lost to us, as by the elevation of a region, 
and the absence of favorable localities or bodies of water for the 
preservation of their remains, we would have to study two homol- 
ogous groups, with the heterologous terms of each corresponding 
with each other, as do now the genera of the Clamatores and Os- 
cines of the Arcifera and Eaniforraia, etc. 

In the same way the characters defining Implacental Mam- 
malia will be found transitional in some type, and this great se- 
ries, homologous with the Placentals, will have to be placed in 
closer connection, in its genera, with the series of the latter, with 
genera of the same, perhaps, now extinct. 

y. Of Mimetic Analogy. 

It has been often remarked that the animals of the Equatorial 
Ethiopian region were very generally of smoky and black colors. 
This is remarkably the case, and the peculiarity of the genus Homo 
in this respect is shared by birds, reptiles, and fishes in a consider- 
able degree. This can not be traced to the effect of torrid climate, 
for the same latitudes in India and the Malaysian Archipelago, 
and in South America, do not produce such colors. 

The similarity in color of desert types has also been remarked. 
The gray sand-hue so well adapted for concealment is universal, 
with few variations, in the reptiles of the Tartar and Arabian 

* This I have alluded to as the non-development of the permanent series ; the 
homology of the dental system of Marsupials appears, however, to be with the latter 
and not with the milk series. See "Flower," " Trans. Roy. Soc.," 1867. (Wortman 
now denies the correctness of Flower's view, and demonstrates that the milk series 
is primitive. See "Encyclopaedia of Dentistry," 1886. Ed. 1886.) 

Plate Hi. 




T Sinc-liii- r- So-n.Pfula 



Plate Ul: 


'1' .Sinclair. & Sonrri 




Fig. 1. Elaps dumerill Jan ; New Gra- Fig. 1 

Fig. 2. Maps Icmniscaius L. ; Brazil. 

Fig. 2. 

Fig. 3. Elaps semipartilus D. and B ; 

New Granada. 
Fig. 4. Ehips psyeJic Baud. ; Brazil. 

Fig. 5. Elaps coralUnus Linn. ; Brazil, 
Central America. 

Fig. 6. Opldbolus doliatus Linn. ; South- 
ern United States to Central 

PLATE Ilia. 

Pliocerms clapoidcs Cope ; Mex- 

Oxyrrhopus trigeminus Y). and 

B.; Brazil. 
! Fig. 3. PUocemis eun/zonus Cope ; New 


Fig. 4. Efi/throlatnprus csculapil L. ; 

Fig. 5. Ccmophora co-^cinea Blum. ; 

Southern United States. 
Fig. 6. Eryihrolamprus venustissimus 

Neuw. ; Brazil, Centr'l America. 


The species placed opposite to each other present similar patterns of coloration. 
Figs. 3 and 4, Plate III, coiTespond with Fig. 3, Plate Illn!, and Fig. 6, Plate III, 
with Figs. 5 and 6, Plate Illrt. The species inhabit the same regions, more or less 
exactly, excepting the two Figs. 1. The Elaps dumcrili would liave been better re- 
placed by a variety of the Elaps fulviiis of Mexico, which has the red spaces black 
bordered ; but a good colored plate was not accc^^sible at the time the drawing was 
made. All the figures are copied from Jan's " Iconographie Generale des Ophi- 
diens " ; and the colors of such as I have not at hand for reference ( Elajjs dumerili, 
Elaps semipartilus, and Elaps psyche) are derived from the " Erpetologie Generale," 
and from Jan's "Prodrome." The species of Elaps are poisonous; the others are 



deserts, the great Sahara and the sands of Arizona and California. 
There is also a tendency to produce spiny forms in snch places ; 
witness the Stellios and XJromastix and Cerastes of the Sahara, 
the Phrynosomas and horned rattlesnake of Southwestern Amer- 
ica. The vegetation of every order, we are also informed, is in 
these situations extremely liable to produce spines and thorns. 

The serpents of the Neotropical region furnish remarkable 
illustrations of mimetic analogy. All the species of the genera 
Elaps, Pliocercus, Erythrolamprus, and many of those of Oxyr- 
rhopus, Ophibolus and Rhabdosoma are ornamented with black 
and yellow rings on a crimson ground. The species of all these 
genera are harmless, except in the case of Elaps, which is venom- 
ous. We may give for this genus, as the most varied, the follow- 
ing range of variation in coloration : 

Pairs of black rings ; 

Single black rings, far apart. 

Single black rings, very close. 

Elaps corrallinus. b 

Elaps mipartitus. d 

nigrocinctus. c 

Pliocercus equalis. c 

Pliocercus euryzonus. d 

Opheomorphus mimus. d 

Oxyrrhopus ? 

Oxyrrhopus petolarius. d 

Erythrolamprus venustissi- 

Erythrolamprus albostola- 

Scolecophis zonatus. a 

mus. a 

tUS. b 

Ophibolus polyzonus. » 

Leptognathus anthracops. a 

Xenodon bicinctus. b 

Single black rings with faint 

Black rings in threes. 

Single black rings about 


equal to intervals. 

Elaps fulvius. 

Elaps lemniscatus. b 


elegans. a 

Pliocercus dimidiatus. » 

Pliocercus elapoides. a 

Catostoma semidoliatum. a 

Procinura aemula. » 

Oxyrrhopus trigeminus, b 

Oxyrrhopus sebae. d 

Pliocercus elapoides var. a 

Ophibolus pyrrhomelas. h 
Chionactis occipitale. h 
Sonora semiannulata. h 
Contia isozona. h 
Chilomeniscus ephippicus. h 

Species a, from Mexico and Central America. 
" b, " Brazil, Venezuela. 
" c, " Central America. 
" d, " western side of Andes. 
" h, " Arizona and Sonora. 

(Two species are now added, 1886.) 

Many of the species in the same column are exceedingly simi- 
lar, and some have little (perhaps nothing) to distinguish them but 
generic characters. The most similar are almost always from the 
same sub-region.* These facts are illustrated in Plates III and III a. 

* Similar parallels exist between the Mexican species of Rhadinaca, Conophis, 
and Erythrolamprus ( = Coniophanes). (Note, 188C.) 


Similar analogies have been pointed out by Bates among the 
Lepidoptera of Brazil, and by Wallace among those of Borneo 
and Celebes, etc. I call attention to these authors here without 
cojDying them, as they will rej^ay perusal in the originals. 

A case of analogy which may belong to this class is that of the 
three genera Chelys among tortoises^ Pipa among frogs, and As- 
predo among Siluroid fishes, species of which inhabit at the same 
time the rivers of Guiana. The crania of these genera are simi- 
larly excessively flattened and furnished with dermal appendages, 
and their eyes are very minute. The singular similarity need only 
be mentioned to those familiar with these genera, to be recognized. 

The bearing of the mimetic analogy, on the question of transi- 
tion of types in the developmental hypothesis, is its demonstra- 
tion of the independence of generic and specific characters of each 
other, which may suggest the possibility of the former being 
modified without affecting the latter. 

These facts might have been introduced under Section II a, but 
•they illustrate the general laws of the present section. 


a. As affecting Class and Ordinal Characters. 

The second law which may be supposed to have governed a 
descent with modification, in the production of existing genera, 
is the force which the environment exercises in permitting or for- 
bidding the existence or persistence of new forms. The forms 
which survive are supposed to have done so by virtue of their su- 
perior adaptation to their environment. This is the " natural 
selection " of Darwin. 

That this law is subordinate to the one first propounded must, 
I think, be evident to any one who studies the assumed results of 
the workings of both, as seen in the characters of genera. It is 
sufficiently well known that the essential features of a majority of 
genera are not adaptive in their natures, and that those of many 
others are so slightly so, as to offer little ground for the suj)posi- 
tion that this necessity has preserved them. 

Both laws must be subordinate to that unknown force which 
determines the direction of the great series. If a series of sup- 
pressions of the nervous and circulatory systems of beings of com- 
mon birth produced the " synthetic " predecessors of the classes 
of Vertebrata, the direction toward which the highest advanced, 


or its ultimate type, can be only ascribed as yet to the divine fiat. 
So far as we can see, there is no reason or law to produce a prefer- 
ence for this direction above any other direction. 

If from these fixed bases descendants have attained to succes- 
sive stations on the same line of progress, in subordinate features 
of the nervous and circulatory systems, constituting the "syn- 
thetic " predecessors of the orders in each class, the type finally 
reached seems to rest on no other basis than the pleasiire of the 

(3. As affecting Family Characters. 

If from the single species generalizing a modern order we at- 
tempt to deduce synthetic predecessors of existing families, we 
find some difficulty, if we attempt to see in these stages a uniform 
succession of progress. A suppression of some features, and ad- 
vance in others, in one and the same individual up to the period 
of reproduction, would produce ofl'spring divergent from the start, 
and represent the relationship of families as we find them. 

y. As affecting Generic Characters. 

If the extremes of our series of genera were characterized by 
structures particularly adapting them above all others to some 
contemporary necessity of existence, this second law, or Darwin's, 
might be regarded as primary. But the writer's experience of 
comparative anatomy has led him to believe that this is not the 
case, as expressed in Proposition IV, page 91. 

This view had not been overlooked by Darwin, who, however, 
treats of it very briefly, and apj)ears to attach it to the theory 
of adaptations, or modifications for a physiological purpose. He 
says, "Origin of Species," page 388 (Amer. edit, 1860): "We 
may extend this view to whole families, or even classes. The 
fore-limbs, which served as legs in the parent siaecies, may become, 
by a long course of modification, adapted in one descendant to 
act as hands, in another as paddles, in another as wings ; and on 
the above two principles — namely, of each successive modification 
supervening at a rather later age, and being inherited at a corre- 
Fpondingly late age — the fore-limbs in the embryos of the several 
descendants of the parent species will still resemble each other 
closely, for they will not have been modified. But in each indi- 
vidual new species the embryonic fore-limbs will differ greatly 
from the fore-limbs in the mature animal ; the limbs in the latter 
have undergone much modification at a rather late period of life. 


and having thus been converted into hands, paddles, or wings." 
He then inclines to assign this change to the necessity of external 
circumstance. But such modification must be the same in kind 
as others, which the same hypothesis must explain, and of which 
the same author remarks (page 383) : " We can not, for instance, 
suppose that in the embryos of the Vertebrata the peculiar loop- 
like course of the arteries near the branchial slits are related 
to similar conditions in the young mammal, which is nourished 
in the womb of its mother, in the egg of the bird which 
is hatched in a nest, and in the spawn of a frog under water. We 
have no more reason to believe in such a relation than we have to 
believe that the same bones in the hand of a man, wing of a bat, 
and fin of a porpoise, are related to similar conditions of life. 
No one will suppose that the stripes on the whelp of the lion, or 
the spots on the young blackbird, are of any use to these animals, 
or related to the conditions to which they are exposed." 

The law of natural selection, however, has no doubt been a 
very important agency in the production of organic types in dif- 
ferent periods of the world's history ; but the part it has played in 
the determination of generic features would appear to have been 
very small. 

In its first effect — that of producing a structure adapted for 
a particular purpose — it would seem to have acted differently to 
produce the same results, and hence not to have produced any of 
the more extended groups, as families, where hundreds of species 
are identical in a single feature. Witness the differences in di- 
verse types of the tree-frogs, each type adapting its possessor to 
an aboreal life : 

I. Claw-like, with globular base Hylid^. 

II. Simple, obtuse-depressed at tip Ranid^. I an and III a. 

III. With a terminal transverse limb Ranid^, Hylarana et aff. 




IV. Bifurcate Balrachyla. 




The short foot of the Testudinidse, where one row of pha- 
langes is omitted, has been already alluded to. The gradual re- 
duction of this set of bones, accompanying general modification 
of form in the increased convexity of dorsal region, as we leave the 
more aquatic and progress toward the terrestrial tortoises, would 


seem to be intimately connected with difference of habit. The 
increased convexity of carapace is an increased defense from fall- 
ing objects — a danger to which land tortoises are far more subject 
than the aquatic. Another protection, not needed by water tor- 
toises so much as by terrestrial, is the faculty of closing one or 
both free lobes of the plastron, as seen in the Cistudo, Sternothae- 
rus, etc., or of portions of the carapace, as in Pixys, Cinixys, etc. 
This might really have been produced by excessive tension on the 
sternal and pelvic muscles while young, and while the sutures 
were not fully interlocked. This, continued for a long time, 
might have produced the result. Yet it is not easy to see what 
protection the aquatic Kinosterna need in this respect, above the 
Emydes of the same countries. The backs of these genera are 
also as convex as are many of the terrestrial genera or Testu- 

I can not better express my views than by quoting the follow- 
ing from the pen of the late Dr. Falconer. It is extracted from 
one of his essays on the Elephantidre : * 

*' Each instance, however different from another, can be shown 
to be a term of some series of continued fractions. When this is 
coupled with the geometrical law governing the evolution of form, 
so manifest in shells of the Mollusca, it is difficult to believe that 
there is not in nature a deeper-seated and innate principle, to the 
operation of which natural selection is merely an adjunct. 

"The whole range of the Mammalia, fossil and recent, can 
not furnish a species which has had a wider geographical distri- 
bution, and at the same time passed through a longer term of 
time, and through more extreme changes of climatal conditions 
than the mammoth. 

"If species are so unstable and so susceptible of mutation 
through such influences, why does that extinct form stand out so 
signally a monument of stability ? By his admirable researches 
and earnest writings, Darwin has, beyond all his contemporaries, 
given an impulse to the philosophical investigation of the most 
backward and obscure braneli of the biological sciences of the 
day ; he has laid the foundation of a great edifice ; but he need 
not be surprised if, in the progress of erection, the superstructure 
is altered by his successors, like the Duomo of Milan, from the 
Roman to a different style of architecture. 

* See writings of Hugh Falconer, vol. ii (cd. by Murcbison). 


" The inferences which I draw from these facts are not op- 
posed to one of the leading propositions of Darwin's theory. 

''With him I have no faith in the opinion that the mammoth 
and other extinct elephants made their appearance suddenly, after 
the type in which their fossil remains are presented to us. The 
most rational view seems to be, that they are in some shape 
the modified descendants of earlier progenitors. But if the as- 
serted facts be correct, they seem clearly to indicate that the older 
elephants of Europe, such as E. meridionalis and E. aniiquus, 
were not the stocks from which the later species, E. primigenius 
and E. africanus sprung, and that we must look elsewhere for 
their origin. The nearest affinity, and that a very close one, of 
the European E. meridionalis, is with the Miocene E. (Loxod.) 
planifrons of India, and of E. primigenius with the existing In- 
dian species. 

"Another reflection is equally strong in my mind, that the 
[theories of the origin of] species by ' natural selection,' or a pro- 
cess of variation from external influences, are inadequate to ac- 
count for the phenomena. The law of Phyllotaxis, which gov- 
erns the evolution of leaves around the axis of a plant, is nearly 
as constant in its manifestation as any of the physical laws con- 
nected with the material world." 

6. As affecting Specific Characters. 

As I have hitherto attempted to prove that the higher grade 
of groups, or, in other words, the higher grade of characters, 
could not have had their origin through natural selection alone, 
though admitting it as a conserving or restricting princijile, I 
now come to ground where natural selection must be allowed full 
sway. The " origin of species " is not the object of this essay, as 
a greater has gone before me, and has done a great deal toward 
showing that a selective power, dependent on adaptation and tele- 
ological relation, has favored or repressed, or even called into ex- 
istence, the varied peculiarities that characterize species and races. 
I will therefore only refer to his well-known works on the " Origin 
of Species " and the ''Modifications of Animals under Domestica- 

I may add that it is within the range of jjossibility that that 
grade or kind of characters found to define the family group may 
be more or less the result of natural selection. 

Acceleration and retardation are also far from excluded from 


the probable causes of specific characters. The species of many 
genera do exhibit a proportion of characters which are the succes- 
sive stages of that one which j^rogresses farthest, as the species of 
Amblystoma in the jjosition of their teeth, nostrils, form of tail, 
and coloration ; of Hyla in form of vomerine teeth, etc. But the 
majority of specific characters are of divergent origin — are Amor- 
phic " as distinguished from developmental. 

e. O71 Metaphysical Species. 

One of the arguments employed against the developmental 
hypothesis, in any form, is that that inherent "potentiality," 
which causes that like shall always produce like, is a metaphysi- 
cal being, which can not be transformed, and which holds the 
structure which it vivifies as a material expression or stamp of it- 
self, and which therefore can not be changed. 

One expression of this inherent metaphysical specific individu- 
ality, if the term may be allowed, has been said to be the peculiar 
traits of the intelligence of species, their motions, voices, and in- 
stincts. But intelligence of all animals is susceptible of impres- 
sions, the lower the intelligence the less susceptible, and the more 
automatic. But, as we rise in the scale of animal being, this im- 
pressibility and capacity for education is undeniably exhibited by 
the dog, horse, and all the well-known domesticated companions 
of man. There can, in view of the capacities of Aves and Mam- 
malia in these respects, be little doubt that all animals are edu- 
cated by the " logic of events," that their intelligence, impressed 
by changed circumstances, can accommodate itself more or less to 
them, and that there is nothing in this part of their being opposed 
to the principle of "descent with modification." 

There is another difficulty in. the way of accepting metaphys- 
ical peculiarity or progenitiveness as isolating species. It is 
marked often strongly in races or varieties, which no one pre- 
tends to have had distinct origin. Here like produces like con- 
tinually, though not persistently, but sufficiently to show that it 
resides in varieties of common origin. The isolation of allied 
species in fact depends, I believe, solely on the supremacy of the 
automatic over the intelligent spirit. "When the intelligent rises 
above the bounds of nature, or the automatic, the mixture or 
separation of allied species depends merely on circumstances of 
necessity, determined by that intelligence. 

But the metaphysical " potentiality " loses all basis, if the law 


of acceleration and retardation be true, for in accordance with it, 
at certain times, Mice does not produce Uhe. 



If it can be shown that groups having the developmental rela- 
tion above insisted on are contemporaries, and if it can be shown 
that this relation is identical in kind with that which we regard 
as measuring the successions of geologic time, we will be led to 
doubt the existence of any very great interruptions in the course 
pf this succession throughout geologic time. And if we can show 
that faunae so related are more or less characteristic of distinct por- 
tions of the earth's surface, at the present time, we will be led to 
anticipate that contemporaneous faunse in different regions, during 
geologic j)eriods also, bore such a relation. If this proposition be 
true, we are led to the further conclusion, which is at variance 
with received canons, that identity of faunse proves successional 
relation in time, instead of synchronism.* That this will ulti- 
mately be demonstrated appears highly probable to the writer, 
though, as yet, the evidence is but fragmentary. 

If the relations expressed under the terms homology and het- 
erology, taken together with the observations on metamorphosis, 
render it probable that a number of genera have reached their ex- 
pression-points, or periods of metamorphosis, at near the same 
time in geologic history, an important point has been gained. 
If we can render it probable that a change in any organic charac- 
ter has been nearly simultaneous throughout a large extent of 
specific forms, the change becomes, on the latter account alone, 
of higher than generic value, but characteristic of such groups as 
Marsupialia, Clamatores, Acrodonta, Arcifera, Heterocerca, and 
the like. 

We have here, also, an important element in the estimation of 
the value of apparent interruptions in the geological liistory of 
the life of the globe. These interruptions, it is true, are greater 
than any such theory as the present can bridge over ; yet such a 
theory, if true, lessens their importance. They are in any case 
well accounted for on the theory of the existence of periods of 
elevation, during which the life of a given region is necessarily 
almost entirely lost to us, through lack of means of preservation 
of their remains. 

* This view has been insisted on by Huxley. 


We may also comi^ai-e such extended metamorphoses with 
those of cosmical matter, such as when, in the course of ages, a 
primeval vapor has in a short time collapsed to the liquid form, or 
as when the vast of liquid in turn has shrunk to its solid con- 
dition ; both alike for ages approaching their change, yet sta- 
tionary in external relations till the moment of transition has 

The following are the zoological relations of the groups al- 
ready referred to : 

The most generalized group of fishes of the Eegio Neotropica 
is that of Characins. Its type, in respect to fin-structure, which 
is common to all the Malacopterygians, is that of an undeveloped 
stage of the Acantliopterygians, the adipose fin being an undevel- 
oped cartilaginous fin, and the cartilaginous fin an undeveloped 
spinous fin.* It may be said to be the highest among Malacop- 
terygians, if we look to the complete oviducts, opercula, jaws, etc.,t 
but it is the lowest as removed farthest from the extreme of 
Malacopterygian peculiarities, as being most generalized or em- 
bracing representatives of all the rest, and approaching nearest 
the types of the past — the Ganoids. For example, Butyrinus and 
Vastres may be compared with Amia. The family is distributed 
chiefly in the Southern Hemisphere. 

The genus Orestias, which Agassiz says is characterized by a 
feature which exists in the immature state of all other Cyprino- 
donts — the absence of ventral fins — is only found in the Neotrop- 
ical region. 

Of the venomous serpents, the inferior group, the Proterogly- 
pha, belong to the Southern Hemisphere, and the Australian and 
Neotropical regions almost exclusively embrace by far the greater 
proportion. Australia contains none other. 

The Iguanian lizards are lower than the Acrodont, exhibiting 
a larval type of detention, and one characteristic of all lower Sau- 
ria and Batrachia. The only acrodont type of Ophiosaura (Trog- 
onophis) is Old World. 

The New World Teidae have not the extent of ossified tem- 
poral roof that their representatives, the Old World Lacertidae, 
have. So the chiefly Neotropical Anguidae have the tongue part- 

* Kner, " Ueber den Bau der Flosscn." 

f This is the correct view, for this family and the Siluroids arc the most special- 
ized of the Malacoi)terygian fishes. (1886.) 


ly of papillose type of tlieir Old World representatives, the Zonu- 
ridae, and partly the smooth or scaly type of the cosmojiolite Sein- 
cidae, which are inferior to them. 

The snake-like forms of the families of the Lacertilia Lepto- 
glossa greatly predominate in the Southern Hemisphere ; also 
those with undeveloped palpebrae. 

The Neotropical type of Testudinata is quite coincident with 
the family Characinidse in relations. It is, like it, largely dis- 
tributed over the Southern Hemisphere, and like it may be re- 
garded, in respect to its pelvic jjeculiarities, as higher than the 
remaining types, but in its generalized character and relationship 
to the past periods may be called lower. 

The Neotropical type of Batrachia anura, that is, the Arcifera, 
is lower in developmental characters than the opposed series, the 
Raniformia ; such of the latter as are found in its limits partake 
in some way of larval incompleteness. The Arcifera are chiefly 
distributed elsewhere in Australia, where no Raniformia exist.* 
Those genera of Old World Raniformia of the lowest or toothless 
group, which display the least development of the cranial bones, 
as Brachymerus and Breviceps, are of the Southern Hemisphere — 
South African. 

The Pullastrine birds are a generalized group, inferior to the 
group opposQd to them — the Gallinfe. Their typical forms, like 
the last, are distributed to the Neotropical and Australian regions : 
the outliers (pigeons) are not so numerously distributed in the 
other regions. 

The Struthious birds, the most synthetic of the class, belong 
exclusively to the Southern Hemisphere ; as is well known, they 
chiefly abound in Australia and its adjacent islands, with an abun- 
dant outlying type — the Tinamus — in South America. 

The penguins, which only of all birds display the metatarsus 
nearly divided, inhabit the Antarctic regions and Cape Horn. 

* The Eucnemis bicolor, Gray, would appear to be an exception, were its generic 
and subordinate affinities truly represented by its name. I have examined the type 
specimen through the kindness of Dr. Giinther, and can state that it is not an Ixa- 
lus {= Eucnemis), and does not even belong to the Raniformia, but is an Arcifer of 
the family Hylidie. If it be not a young Calamita or Hyla, it will be a Hylella near 
the H. carnea type. (Boulcnger, in 1882, determined it to be a Hylella. Ed. 

Giinther states that Hijlorana eri/ihraea has been found at the extreme northern 
point — Cape York — of Australia. If so, the case is parallel to the occurrences of 
the Raniform Ranula in northern South America. 


The Clamatorial type of the Passeres exhibit larval characters 
in the non-development of the singing apparatus, and the scaled 
or nearly naked tarso-metatarsus. These are chiefly South Amer- 

Of Mammalia, the placentals without enamel on their teeth, 
which, in this respect, never reach the full development of the 
class, whose dentition is also monophyodont, i. e., the Edentata, 
inhabit only the Southern Hemisphere, and almost altogether the 
Neotropical region. The implacental Mammalia, also (except in 
one tooth) monophyodont, which approach birds and reptiles in 
so many respects, are confined to the Southern Hemisphere, and 
chiefly, as all know, to Australia. 

Of the Quadrumana, the Platyrrhine group is known to be in- 
ferior to the Catarrhines : the former presents an entirely embry- 
onic condition of the os tympanimtm, which is passed by the latter 
in early age ; * it contains also the only clawed genus of the true 
monkeys. It is confined to the Neotropical realm. To Madagascar, 
also of the Southern Hemisphere, and nearest in many ways to 
the Neotropical, pertain the lowest families of the Quadrumana, 
the Lemuridse and Chiromyidffi ; the former presenting brains 
without convolutions, and approaching in many ways the Insec- 
tivora ; the last imitating, at least, a Eodent. 

There are also other reasons for the inferiority of South Amer- 
ica. Its deer, which are few, include those which never produce 
more than the " dague," or the first horn of the northern Cervus, 
and also those which never get beyond the fourth step in the de- 
velopment of the lower group of R. Neardica. 

The Loricariidffi, of South America, I am informed by Prof. 
Agassiz, possess the foetal pupil of the vertebrate type. 

If we glance at ColeoiDtera we find the great predominance of 
the groups with undeveloped tarsus, the three- and four-jointed 
Trimera and Tetramera, and of the lower group with undeveloped 
sternum, f the Rynchophora, in the Neotropical region. 

Among Lepidoptera it is known that the most gigantic of the 
species of the Neotropical region are Noctuidge (Erebus, etc.), .and 
that in that region this low type of the order reaches its greatest 
development. The largest forms of the Rcgio Nearctica, as well 
as Palfearctica, are representatives of the higher tyjie of the Satur- 

* See Dr. H. Allen, "Proceed. A. N. S.," Phila., 1867. 
\ Leconte, American Association, 1867. 


niidae (Atticus, Telea, etc.), while the largest and most powerful 
of this order in the Palgeotropical (Indian) region are the Papilio- 
nid forms of Ornithoptera, etc., the generally admitted crown and 
head of all. Of course other types, both higher and lower, are 
largely developed in each and all of these regions, and the signifi- 
cance of the above facts is perhaps only to be seen when taken in 
connection with a large number of others pointing in the same 

Two or three comparisons of different fauna? may bo brought 
forward finally. First, returning to the birds, a survey of some 
of the differences between the birds of Panama, Pennsylvania, and 
Palestine may be made.* 

Tristram noticed three hundred and twenty-two species of 
birds within the range of the ancient territory of Palestine. Of 
these two hundred and thirty were land and ninety-two water 
birds, i. e., Natatores and the wading Cursores. Of the two hun- 
dred and thirty, seventy-nine are common to the British Islands, 
and thirty-six of them are found in China, but a small proportion 
extending their range to both these extremes. Of the water birds, 
which are always more widely distributed, fifty-five of the ninety- 
two are British and fifty-seven Chinese. Twenty-seven appear to 
be confined to Palestine, and to the immediately adjacent country ; 
the largest of these is a crow. 

Taking the two hundred and thirty land birds at a glance, 
we find the utter absence of so many of the well-known forms 
that enliven our grounds and forests. The absence of Tanagridse 
(including Sylvicolidse) and Icteridae, changes the aspect of the 
bird-fauna at once. What have we here, then, of nine-quilled 
Oscines to enliven the meadows like our swarms of blackbirds, or 
fill the tree-tops and thickets with flutter like our wood-warblers ? 
Nothing ; for the twenty-four sjDecies of finches, Fringillidae, will 
but balance our own, though the genera are all different but four, 
and tliey the most weakly represented by species. We must look 
to the higher series, the ten-quilled song-birds, for the missing 
rank and file. While a much larger extent of the Eastern United 
States possesses fifty species of these types, the little Palestine has 
already furnished a list of one hundred and twenty-eight. 

First, of the crows, which verge nearest Icteridae by the star- 
lings, we have thirteen species against five in our district of the 

* From the " American Naturalist," 1868, by the author. 


United States, and not less than seven of the typo genus Corvus, 
to our one common and two rare. Of these two are of the larger 
species, the ravens. If we turn to the cheerful larks, we find the 
proj)ortion again the same ; fifteen species for Palestine and one 
for the whole United States. One congener of our species occurs 
there ; the other genera call to mind the African deserts and Eus- 
sian steppes. Motacillidae, again, ten to one against our fauna. We 
have two Tanagrid^e to imitate them, besides the one true relative. 
In swallows we are about equal, and in the forest-haunting Paridae 
— titmice and wrens — we exceed a little ; but the comparison of 
Sylviidse and Turdidse is most striking. These highest of the bird 
series, especially made to gladden man's haunts with song, exceed 
in number all the other ten-quilled Oscines together inhabiting 
Palestine, amounting to seventy-five species. In our correspond- 
ing region of the United States nineteen species is the quantum. 
It is true no mocking-bird or wood-robin is known away from our 
shores, but Palestine has the nightingale, the black-cap, and the 
true warblers or sylvias, which, while they glean from shrub and 
tree their smallest insect enemies, as do our equally numerous 
small Tanagridae, have much louder and sweeter voices. 

Our solitary bluebird represents the long-winged Turdidse ; in 
the Holy Land there are twenty species corresponding, though 
none are of our genus. There are, indeed, but three genera of 
these two families common to both countries. One of these, La- 
nius, the butcher-bird, occurs here in one species, in Palestine 
in six. 

Turning now to a lower series, we look in vain for Clamatorial 
perchers ; that series which gives us the fierce king-bird and queru- 
lous pewee, and which peoples South America with thrush and 
warbler, and shrike and tree-creeper. 

In taking a hasty glance over the lower groups, where the carot- 
id arteries begin to be double, as the Syndactyli, we find Palestine 
too far from the tropics to present us with much array ; but in 
the related zygodactyles our forest-crowned continent must claim 
great pre-eminence. It has but a solitary Picus, while we have 
eight in the immediate neighborhood of lat. 40°, in our Eastern 

I will close with the birds of prey. Four swamp-hawks, eleven 
species of falcons, four kites, and eight native eagles, form a list 
unequaled in the annals of nobility by any land. Tliere are to- 
gether thirty-one species of Falconida}, and of Vultures four. The 


eagles appear l3 be all common, among them the most magnificent 
birds of prey, the imperial and golden species of these creatures. 

To the ornithologist, acquainted with the fauna of North 
America, it will thus be readily perceived that, in comparison, the 
ornis just examined, possesses more numerous representatives of 
the higher groups of the birds, and among lower groups possesses 
chiefly those of superior grade, or lacks them altogether. Let us, 
however, compare it with that of Central America, where varied 
surface and temperature offer even greater opportunity for variety, 
within quite as restricted an area. 

The bird fauna has been found by Messrs. Sclater and Salvia 
to embrace about three hundred and eighty-five species, which is 
sixty-three more than were mentioned to occur in Palestine, which 
is open on three sides to the great continent. Eighty of three 
hundred and forty-eight land birds are characteristic of Central 
America ; and those which find their kin limited to the Isthmus 
and adjoining regions of New Grenada and Equador amount to 
about seventy-five more. Twenty-seven is the number not known 
to extend beyond the boundaries of Palestine ; as to the Middle 
vStates of our Union, not one species has been shown to be restricted 
within such narrow limits. 

A single species occurs in Europe ; this is the fish-hawk, an 
animal which combines the cosmopolite habit of the sea-bird with 
the powerful flight of the bird of prey. This is also the only spe- 
cies common to the Panama and Palestine catalogues. 

The birds of prey are numerous — twenty-nine species. Among 
these there is no true eagle or falcon, and of the nineteen genera 
but four belong to the fauna of the Holy Land. There is but one 
species to represent the great grouse family, but, instead, three 
families of their South American imitators, the Pullastr^, instead 
of the one — that of the Pigeons — slimly represented in Palestine, 
and in North America as well. 

Coming to the closer test of superiority, the Passeres — those 
delicate creatures, apparently so dependent on those laws which 
govern increase and provision, and so affected by the changes tliat 
man works in the face of Nature — what do we find ? We count 
one hundred and six distinct species. There are none in Pales- 
tine. Of songsters, the Oscines, ninety-six species, await man's 
conquest of the wilderness, to increase in numbers and to display 
their gifts, while Palestine rejoices in a whole army of them. But 
the contrast is more remarkable if we analyze these forms. Of the 


Isthmian Oscines, seventeen only hold the first rank, by virtue of 
their additional, the tenth primary quill, while this feature marks 
one hundred and twenty-eight species of Palestine. As we rapidly 
follow the line to the point where its extreme is manifested, in the 
family of the Thrushes or Turdidse, Panama is left but two soli- 
tary pioneers of these songsters of the North, while seventy-five 
species represent the family in Palestine. 

The comparison between different faunse exhibits an apparent 
gradation in some other groups equally curious. Thus, the true 
Cyi^rinidffi in the Palaearctic region reach a great development, 
and produce the highest number of teeth on their pharyngeal jaws 
known, as well as attains the greatest bulk and importance. The 
number of these teeth is usually seven to five in the inner row ; 
only two or three genera exhibit only four on both. In the Ne- 
arctic region the number of teeth is almost always 4 — 4, more 
rarely 4 — 5, and very seldom as high as 5 — 5. The species of the 
family are excessively numerous, but are, with scarcely any excep- 
tion, of small size and weak organism. These statements apply to 
those of the eastern district of the region between the Eocky 
Mountains and the Atlantic. Similar tyi^es occur in the northern 
region of the Neotropical — Mexico, but in no great numbers. 
Farther south the family disappears, its place being supplied by 
the generalized family of Characinidae. 

I have already alluded to the great variety of the highest or 
pentamerous carnivorous beetles in the Palaearctic region. They 
are extremely abundant in the Nearctic, while the intermediate 
territory, the Sonoran and Mexican sub-districts, are the head- 
quarters of the next lower form, the Tenebrionidae, which have 
the tarsal Joints 4 — 5. These give place in the Neotropical to the 
multitudes of the still lower series — those with the joints 4 — 4 and 
3 — 3 — Tetramera and Trimera. 

The preceding comparisons indicate that an inherent difference 
between the types of a continent exists at the present time, though 
the difference is subordinated to a universal distribution of the 
higher groups throughout the earth. Has this state of things ex- 
isted for any long period, or is it a result of different progress in 
the same group since the human period ? This brings us neces- 
sarily to a consideration of the truths of paleontology, especially 
of the last periods, which have been already urged by Darwin. 
Thus the present fauna of Australia was j^receded in the Post-Pli- 
ocene and Pliocene by forms possessing similar peculiarities, and 


belonging to the same classes. That is by herbivorous and car- 
nivorous marsupials and monotremes, and by Varanid Sauria, all 
of greater size than their predecessors. 

The same fact is well known of the Neotropical region, its 
present peculiar Edentata having been preceded by giants of the 
same type in the Post-Pliocene and Pliocene. 

In the Nearctic region peculiar existing genera, as Procyon, 
Alces, Castor, Bos, Sciurus, Arctomys, Lepus, Ovibos, Sorex, Me- 
phitis, Felis, Ursus, Menopoma, Aspidonectes, Crotalus, are rep- 
resented by Post-Pliocene fossils. 

The same occurs in the later Palaearctic formations, where Cer- 
vus. Bos, Canis, Mustelidae, Insectivora, Vipera, Alytes, Triton, 
etc., are allied predecessors of existing types. In the Palaeotrop- 
ical area a wonderful development of Elephas and Gavialis preceded 
the same types of the present. 

Prior to these faunae another state of things has, however, ex- 
isted. North America has witnessed a withdrawal of a Neotrop- 
ical fauna, and the Palaearctic the retreat of an Ethiopian type. 
During the Post- Pliocene in North America, Neotropical genera 
were to Nearctic as 12 to 29, as the record now stands. In the 
Pliocene beds of Pikermi (Greece) antelopes, giraffes, rhinoceros, 
hippopotamus, huge manis,* monkeys, monitors, and other genera 
and species of African relationship are the prevailing forms. 

Still earlier, a strong mingling of Nearctic, and more of Neo- 
tropical types, abounded in the Palasarctic. The genera Chelydra, 
Andrias, Podocnemis,t Platemys, Caviiform, Psammoryctid and 
Hesperomys-like Rodentia, Opossums, and Raccoon-like Carnivora. 

We have, then, three important terms from which to derive a 
theory of the creation : 1, the existing six faunae bear in many of 
their parts developmental relations to one another ; 2, they were 
preceded immediately by faunae similar to them in each case, but 
more remotely by faunae like that now next lower. 

On the whole, there can be no doubt of the truth of the gen- 
eralization : Tliat the Southern Hemisphere is a geologic stage 
behind the Northern Hemisphere in progress, on account (1) of 
its perfection in types extinct in the Northern, and (2) inferiority 
in modern types prevalent in the Northern. 

In order, however, to demonstrate this j)oint more fully, let us 

* Ancylotherium, Macrotherium. 

f P. bowcrbankii {Platemys, Owen). P. Icevis {Emys, Owen). 


examine to what extent the higher types exist in the Southern, 
and lower or ancient in the Northern. 

The Percoid fishes and their allies have Australian and South 
American representatives in their fresh waters, but they are as 
mere outliers of the great mass in the Northern Hemisphere. The 
higher tyj^e of venomous serpents (Solenoglypha) occur in both 
the Ethiopian and Neotropical regions, but they preponderate in 
the Northern Hemisphere. The higher group of the Saurians 
(the Acrodonta) abounds in the Ethiopian and Australian regions ; 
they are as abundant in the Indian and Palsearctic regions of the 
Northern Hemisphere. In the Southern, also, by Uromastix and 
the Eynchocephalia, they approach nearest the ancient types of the 
Dicynodontia and the Crocodilia. Lacertidse, and not Teida3, 
occur in the Ethiopian ; but they are but a proportion of the 
whole, which chiefly exists in the Nearctic. 

Raniform, and not Arciferous Anura, populate South Africa ; 
they, however, form but a small proportion compared with the 
great series of the Nearctic, Palaarctic, and Palaeotropical regions. 
It is, however, superior in Anura to the Nearctic, taken by itself. 

Easorial birds, and not Pullastrae, are the food sjiecies of South 
Africa ; but they do not compare in abundance or size with those 
of the three regions just mentioned. 

Moreover, but few Clamatores exist in either Australia or 
Ethiopia. The Oscine types are abundant ; nevertheless, they can 
not be compared in relative abundance with those of the northern 
regions. It must also be remembered that the migratory capa- 
bilities of birds render them less expressive of the true nature of 
any fauna. 

The higher family of the Qnadrumana, the Simiidae, replaces 
in Africa the Cebidae of the Neotropical ; they are, however, most 
abundant in the Palaeotropical region, in the other hemisphere. 

There are two ancient or inferior types of the Northern Hemi- 
sphere : First, its fishes, the Sturgeons of the Nearctic and Paloe- 
arctic, and the Gars of the Nearctic* The latter only have rep- 
resentatives in the Southern Hemisphere, Polypterus and Cala- 
moichthys in Africa, and so may be said to be equally distributed ; 
but the former are confined to the north. We do not know, how- 
ever, whether they are of a modern or an ancient type, nor do we 

* Subsequent investigations have proved that Polypterus and Calamoichthys are 
of much more ancient type than gars and sturgeons. (Ed. 18SG.) 


know of extinct sturgeons in the Southern Hemisphere. Indeed, 
the Ganoid series is not well defined or known as yet. If, as 
Agassiz states, the Siluroids pertain to it, it is cosmojjolitan, 
though least represented in the Palgearctic. 

Second, the Tailed or Urodele Batrachia. This order, entirely 
characteristic of the Northern Hemisj^here, is a group which com- 
bines characters of Anura with those of the ancieut forms, and 
possesses in its Nearctic types many of low development. The 
Gymnophidia of the Southern Hemisphere can not be considered 
inferior to them. In the possession of this group the Northern 
Hemisphere presents its first element of inferiority. 

The preceding comparisons indicate also the relations of tlie 
regions proper to each other. It is obvious enough that the Ethi- 
opian is much superior to the two others of the Southern Hemi- 
sphere. As to the Australian and Neotropical, the former must 
still be regarded as probably the most ancient, though possessing 
at the same time a much stronger admixture of northern forms. 
I have already presented the relations, with the inferior forms of 
each, thus : * 

E, Australis. — Inferior in possessing Monotrematous and Marsu- 
pial Mammalia, Pullastriform and Struthious Birds, Serpent- 
iform Pleurodont Lacertilia, Arciferous Batrachia, Pleuro- 
dire Tortoises, its Elapid venomous snakes, and the whole 
Flora, according to linger. 

R. Neotropica. — Marsupial and Edentate Mammalia, Inferior 
Eodentia and Quadrumana, Pleurodire Tortoises, Pleurodont 
Lacertilia, Arciferous Batrachia, Clamatorial and Pullas- 
triform Birds, Characin and Erythrinid Malacopterigii. 


The following may be looked upon as conclusions which have 
been indicated in the preceding pages : 

I. Species have developed from pre-existent species by an in- 
herent tendency to variation, and have been preserved in given 
directions and repressed in others by the operation of the law of 
natural selection (Darwin). 

II. Genera have been produced by a system of retardation or 
acceleration in the development of individuals ; the former on 
pre-established, the latter on preconceived lines of direction. Or, 

* "Jour. Acad. Nat. Sci.," Philada., 1866, p. 109. 


in other words, that while nature's series have been iDrojected in 
accordance with the law of acceleration and retardation, they have 
been limited, modified, and terminated by the law of natural se- 
lection, which may itself have oj)erated in part by the same law. 

III. The processes of development of specific and generic char- 
acters have not proceeded pari passu, transitions of the one kind 
not being synchronous witli transitions of the other ; and that, 
therefore, species may be transferred from one genus to another 
without losing their specific characters, and genera from order to 
order without losing their generic characters. 

IV. And as the heterologous terms of the peculiar homologous 
groups present an ''inexact parallelism" with each other; and 
as types related by inexact parallelism are each among themselves 
exact parallels in sej)arate series, whose earliest members present 
" exact parallelisms " with each other, it follows — 

V. That the heterologous terms or genera in the later series 
are modified descendants of those of the earlier series ; in other 
words, that certain groups higher than genera are produced from 
others of similar high value by ''descent with modification." 

YI. That the result of such successional metamorphoses will 
be expressed in geologic history by more or less abrupt transitions 
or expression-points, rather than by uniformly gradual succes- 

Of course, under the conclusion stated in Proposition II, the 
genus Homo has been developed by the modification of some pre- 
existent genus. All his traits which are merely functional have, 
as a consequence, been produced during the process. Those traits 
which are not functional, but spiritual, are of course amenable to 
a different class of laws, which belong to the province of religion. 



At a meeting of the Philadelphia Academy of Natural Sci- 
ences, held February 23, 1876, Prof. Cope gave a history of the 
progress of the doctrine of evolution of animal and vegetable 
types. While Darwin has been its prominent advocate within 
the last few years, it was first presented to the scientific world, in 
a rational form, by Lamarck, of Paris, at the commencement of 
the present century. Owing to the adverse influence of Cuvier, 
the doctrine remained dormant for half a century, and Darwin 
resuscitated it, making important additions at the same time. 
Thus Lamarck found the variations of species to be the primary 
evidence of evolution by descent. Darwin enunciated the law of 
"natural selection" as a result of the struggle for existence, in 
accordance with which "the fittest" only survive. This law, 
now generally accepted, is Darwin's principal contribution to the 
doctrine. It, however, has a secondary joosition in relation to 
the origin of variation, which Lamarck saw, but did not account 
for, and which Darwin has to assume in order to have materials 
from which a " natural selection " can be made. 

The relations exhibited by fully grown animals and plants 
with transitional or embryonic stages of other animals and plants, 
had attracted the attention of anatomists at the time of Lamarck. 
Some naturalists deduced from this now universally observed 
phenomenon that the lower types of animals were merely re- 
pressed conditions of the higher, or, in other words, were embry- 
onic stages become permanent. But the resemblances do not 
usually extend to the entire organism, and the parallels are so 
incomplete that this view of the matter was clearly defective, 
and did not constitute an explanation. Some embryologists, as 
Lereboullet and Agassiz, asserted that no argument for a doctrine 
of descent could be drawn from such facts. 

The speaker, not adopting either view, made a full investiga- 


tion into the later embryonic stages, chiefly of the skeleton of the 
Batrachia, in 1865, and Prof. Hyatt, of Salem, Mass., at the 
same time made similar studies in the develoj)ment of the Ammo- 
nites and Nautili. The results as bearing on the doctrine of evo- 
lution were published in 1869 (in ''The Origin of Genera"). It 
was there pointed out that the most nearly related forms of ani- 
mals do present a relation of repression and advance, or of perma- 
nent embryonic and adult type, leaving no doubt that the one is 
descended from the other. This relation was termed exact paral- 
lelism. It was also shown that, if the embryonic form were the 
parent, the advanced descendant was produced by an increased 
rate of growth, which phenomenon was called acceleration ; but 
that if the embryonic type were the offspring, then its failure to 
attain to the condition of the parent is due to the supervention of 
a slower rate of growth ; to this phenomenon the term retarda- 
tion was applied. It was then shown that the inexact parallelism 
was the result of unequal acceleration or retardation ; that is, ac- 
celeration affecting one organ o^ part more than another, thus 
disturbing the combination of characters which is necessary for 
the state of exact parallelism between the perfect stage of one 
animal and the transitional state of another. Moreover, accelera- 
tion implies constant addition to the parts of an animal, while re- 
tardation implies continual subtraction from its characters, or 
atrophy. He had also shown ("Method of Creation," 1871) that 
the additions either appeared as exact repetitions of pre-existent 
parts, or as modified repetitions, the former resulting in simple, 
the latter in more complex organisms. 

Prof. Haeckel, of Jena, has added the keystone to the doc- 
trine of evolution in his gastraea theory. Prior to this generaliza- 
tion it had been impossible to determine the true relation existing 
between the four types of embryonic growth, or, to speak other- 
wise, than that they are inherently distinct from each other. 
But Haeckel has happily determined the existence of identical 
stages of growth in all of the types of eggs, the last of which is 
the (jastrula ; and beyond which the identity ceases. Not that 
the four types of gastrula are without difference, but this differ- 
ence may be accounted for, on plain principles. In 1874, Haeckel, 
in his " Anthropogenie," recognizes the importance of the irregu- 
larity of time of appearance of the different characters of animals, 
during the period of growth, as affecting their permanent struct- 
ure. While maintaining the view that the low forms represent 


the transitional stages of the higher, he proceeds to account for 
the want of exact correspondence exhibited by them at the present 
time, by reference to this principle. He believes that the rela- 
tion of j)arent and descendant has been concealed and changed 
by subsequent modifications of the order of appearance of charac- 
ters in growth. To the original, simple descent he applies the 
term palingenesis ; to the modified and later growth, cmnogenesis. 
The causes of the change from palingenesis to coenogenesis he re- 
gards as three, viz., acceleration, retardation, and heterotopy. 

It is clear that the two types of growth distinguished by Prof. 
Haeckel are those which had been pointed out by Prof. Cope in 
"The Origin of Genera," as producing the relations of "exact" 
and "inexact parallelism"; and that his explanation of the 
origin of the latter relation by acceleration or retardation is the 
same as that of the latter essay. The importance which he at- 
taches to the subject was a source of gratification to the speaker, 
as it was a similar impression that led to the publication of " The 
Origin of Genera " in 1869. 

It remains to observe that the phenomena of exact parallelism 
or palingenesis are quite as necessarily accounted for on the prin- 
ciple of acceleration or retardation as are those of inexact paral- 
lelism or ccBnogenesis. Were all parts of the organism acceler- 
ated or retarded at a like rate, the relation of exact parallelism 
would never be disturbed ; while the inexactitude of the parallel- 
ism will depend on the number of variations in the rate of growth 
of different organs of the individual, with additions introduced 
from time to time. Hence it may be laid down that synchronous 
acceleration or retardation produces exact parallelism, and lietero- 
chronous acceleration or retardation produces inexact j^arallel- 

In conclusion, it may be added that acceleration of the seg- 
mentation of the protoplasma or animal portion of the primordial 
egg, or retardation of segmentation of the deutoplasma or vegeta- 
tive half of the egg, or both, or the same relation between the 
growth of the circumference and center of the egg, has given rise 
to the four types which the segmentation now presents. 

An analysis of the laws of evolution may be tabulated as fol- 
lows : 



■*^ I— ( 


»* § in- S 

s-^S o a 

"5 "^ r* ■^^ 

g ^ "■ ~ 
g ^"o Sri 

, ^. ( Exact repetition ^ 

acederahon, ) Modified repetition : 

which proceeds by | g^^^,.^t^py| -^ 

retardation, \ Exact atrophy ^ 

which proceeds by ( Inexact atrophy (or senilityr * 


* So called by Prof. Hyatt. 



" Man shall not live by bread alone, but by every word that proceedeth out of the 

mouth of God shall man live." 

Theee is apparently considerable repugnance in the minds of 
many excellent people to the acceptance, or even consideration, of 
the hypothesis of development, or that of the gradual creation by 
descent, with modifications from the simplest beginnings, of the 
different forms of the organic world. This objection probably 
results from two considerations : first, that the human species is 
certainly involved, and man's descent from an ape asserted ; atid, 
secondly, that the scheme in general seems to conflict with that 
presented by the Mosaic account of the Creation, which is regarded 
as communicated to its author by an infallible inspiration. 

As the truth of the hypothesis is held to be infinitely probable 
by a majority of the exponents of the natural sciences at the pres- 
ent day, and is held as absolutely demonstrated by another por- 
tion, it behooves those interested to restrain their condemnation, 
and on the other hand to examine its evidences, and look any con- 
sequent necessary modification of our metaphysical or theological 
views squarely in the face. 

The following pages state a few of the former ; if they suggest 
some of the latter, it is hoped that they may be such as any logical 
mind would deduce from the premises. That they will coincide 
with the spirit of the most advanced Christianity, I have no 
doubt ; and that they will add an appeal through the reason to 
that direct influence of the Divine Spii'it which should control the 
motives of human action, seems an unavoidable conclusion. 


It is well known that a species is usually represented by a great 
number of individuals, distinguished from all other similar associ- 


ations by more or less numerous points of structure, color, size, 
etc., and by habits and instincts also, to a certain extent ; that 
the individuals of such associations reproduce their like, and can 
not be produced by individuals of associations or species which 
present differences of structure, color, etc., as defined by natural- 
ists ; that the individuals of any such series or species are incapa- 
ble of reproducing with those of any other species, with some 
exceptions ; and that in the latter cases the offspring are usually 
entirely infertile. 

The hypothesis of Cuvier assumes that each species was created 
by divine power as we now find it at some definite point of geo- 
logic time. The paleontologist holding this view sees, in accord- 
ance therewith, a succession of creations and destructions marking 
the history of life on our planet from its commencement. 

The development hypothesis states that all existing species 
have been derived from species of pre-existent geological periods, 
as offspring or by direct descent ; that there have been no total 
destructions of life in past time, but only a transfer of it from 
place to place, owing to changes of circumstance ; that the types 
of structure become simpler and more similar to each other as we 
trace them from later to earlier periods ; and that finally we reach 
the simjalest forms consistent with one or several original parent 
types of the great divisions into which living beings naturally fall. 

It is evident, therefore, that the hypothesis does not include 
change of species by hybridization, nor allow the descent of living 
species from any other living species : both these propositions are 
errors of misapprehension or misrepresentation. 

In order to understand the history of creation of a complex 
being, it is necessary to analyze it and ascertain of what it con- 
sists. In analyzing the construction of an animal or plant we 
readily arrange its characters into those which it possesses in com- 
mon with other animals or plants, and those in which it resem- 
bles none other : the latter are its individual characters, consti- 
tuting its individuality. Next, we find a large body of characters, 
generally of a very obvious kind, which it possesses in common 
with a generally large number of individuals, which, taken col- 
lectively, all men are accustomed to call a species ; these charac- 
ters we consequently name specific. Thirdly, we find characters, 
generally in parts of the body which are of importance in the ac- 
tivities of the animal, or which lie in near relation to its mechan- 
ical construction in details, which are shared by a still larger 


number of individuals than those which were similar in specific 
characters. In other words, it is common to a large number of 
species. This kind of character we call generic, and the grouping 
it indicates is a genus. 

Farther analysis brings to light characters of organism which 
are common to a still greater number of individuals ; this we call 
a family character. Those which are common to still inore nu- 
merous individuals are the ordinal: they are usually found in 
parts of the structure which have the closest connection with the 
whole life-history of the being. Finally, the individuals compos- 
ing many orders will be found identical in some important char- 
acter of the systems by which ordinary life io maintained, as in 
the nervous and circulatory : the divisions thus outlined are called 

By this process of analysis we reach in our animal or plant 
those peculiarities which are common to the whole animal or vege- 
table kingdom, and then we have exhausted the structure so com- 
pletely that we have nothing remaining to take into account beyond 
the cell-structure or homogeneous protoplasm by which we know 
that it is organic, and not a mineral. 

The history of the origin of a type, as species, genus, order, 
etc., is simply the history of the origin of the structure or struct- 
ures which define those groups respectively. It is nothing more 
nor less than this, whether a man or an insect be the object of 


a. Of Specific Characters. 

The evidences of derivation of species from species, within the 
limits of the genus, are abundant and conclusive. In the first 
place, the rule which naturalists observe in defining species is a 
clear consequence of such a state of things. It is not amount and 
degree of difference that determine the definition of species from 
species, but it is the permanency of the characters in all cases and 
under all circumstances. Many species of the systems include va- 
rieties and extremes of form, etc., which, were they at all times 
distinct, and not connected by intermediate forms, would be esti- 
mated as species by the same and other writers, as can be easily 
seen by reference to their works. 

Thus, species are either "restricted " or "protean," the latter 


embracing many, the former few variations ; and the varieties in- 
cluded by the protean species are often as different from each other 
in their typical forms as are the "restricted" species. As an ex- 
ample, the species Homo sapiens (man) will suffice. His primary 
varieties are as distinct as the species of many well-known genera, 
but can not be defined, owing to the existence of innumerable in- 
termediate forms between them. 

As to the common origin of such "varieties^' of the protean 
species, naturalists never had any doubt ; yet when it comes to the 
restricted " species," the anti-developmentalist denies it in tofo. 
Thus the varieties of most of the domesticated animals are some 
of them known — others held with great probability to have had a 
common origin. Varieties of plumage in fowls and canaries are 
of every-day occurrence, and are produced under our eyes. The 
cart-horse and racer, the Shetland pony and the Norman, are 
without doubt derived from the same parentage. The varieties of 
pigeons and ducks are of the same kind, but not every one is 
aware of the extent and amount of such variations. The varieties 
in many characters seen in hogs and cattle, especially when exam- 
ples from distant countries are compared, are very striking, and 
are confessedly equal in degree to those found to define species in 
a state of nature : here, however, they are not definitive. 

It is easy to see that all that is necessary to produce in the 
mind of the anti-developmentalist the illusion of distinct origin 
by creation of many of these forms would be to destroy a number 
of the intermediate conditions of specific form and structure, and 
thus to leave remaining definable groups of individuals, and there- 
fore "species." 

That such destructions and extinctions have been going no 
ever since the existence of life on the globe is well known. That 
it should affect intermediate forms, such as bind together the 
types of a protean species as well as restricted species, is equally 
certain. That its result has been to produce definable species can 
not be denied, especially in consideration of the following facts : 
Protean species nearly always have a wide geographical distribu- 
tion. Thev exist under more varied circumstances than do indi- 
viduals of a more restricted species. The subordinate variations 
of the protean species are generally, like the restricted species, 
confined to distinct subdivisions of the geographical area which 
the whole occupies. As in geological time changes of level have 
separated areas once continuous by bodies of water or high mount- 


ain-ranges, so have vast numbers of individuals occupying such 
areas bee;i destroyed. Important alterations of temperature, or 
great changes in abundance or character of vegetable life over 
given areas, would produce the same result. 

This part of the subject might be prolonged, were it necessary, 
but it has been ably discussed by Darwin. The rationale of the 
"origin of species," as stated by him, may be examined a few 
pages farther on. 

p. Of the Characters of Higher Groups. 

a. Relations of Structures. — The evidences of derivative origin 
of the structures defining the groups called genera, and all those 
of higher grade, are of a very different character from those dis- 
cussed in relation to specific characters ; they are more difficult of 
observation and explanation. 

Pirst : It would appear to be supposed by many that the crea- 
tion of organic types was an irregular and capricious process, 
variously pursued by its Author as regards time and place, and 
without definite final aim ; and this notwithstanding the wonder- 
ful evidences we possess, in the facts of astronomy, chemistry, 
sound, etc., of his adhesion to harmonious and symmetrical 
sequences in his modes and plans. 

Such regularity of plan is found to exist in the relations of the 
great divisions of the animal and vegetable kingdoms as at present 
existing on the earth. Thus, with animals we have a great class 
of species which consists of nothing more than masses or cells of 
protoplasmic matter, without distinct organs ; or the Protozoa. 
We have then the Coelenterata (example, corals), where the organ- 
ism is composed of many cells arranged in distinct parts, but 
where a single very simple system of organs, forming the only in- 
ternal cavity of the body, does the work of the many systems of 
the more complex animals. Next, the Echinodermata (such as 
star-fish) present us with a body containing distinct systems of 
organs inclosed in a visceral cavity, including a rudimental nerv- 
ous system in the form of a ring. In the Molluscs to this con- 
dition is added further complication, including extensions of 
the nervous system from the ring as a starting-point, and a 
special organ for a heart. In the Articulates (crabs, insects) we 
have like complications, and a long distinct nervous axis on the 
lower surface of the body. The last branch or division of ani- 
mals is considered to be higher, because all the systems of life 


organs are most complex or specialized. The nervous ring is 
almost obliterated by a great enlargement of its usual ganglia, 
thus become a brain, which is succeeded by a long axis on the 
upper side of the body. This and other points define the Ver- 

Plans of structure, independent of the simplicity or perfection 
of the special arrangement or structure of organs, also define 
these great groups. Thus the Protozoa present a spiral, the 
Coelenterata a radiate, the Echinodermata a bilateral radiate plan. 
The Articulates are a series of external rings, each in one or more 
respects repeating the others. The Molluscs are a sac, while a 
ring above a ring, joined together by a solid center-piece, repre- 
sents the plan of each of the many segments of the Vertebrates 
which give the members of that branch their form. 

These bulwarks of distinction of animal types are entered into 
here simply because they are the most inviolable and radical of 
those with which we have to deal, and to give the anti-develop- 
mentalist the best foothold for his position. I will only allude to 
the relations of their points of approach as these are affected by 
considerations afterward introduced. 

The Vertebrates approach the Molluscs closely at the lowest 
extreme of the former and higher of the latter. The lamprey 
eels of the one possess several characters in common with the 
cuttle-fish or squids of the latter. The amphioxus is called the 
lowest Vertebrate, and, though it is nothing else, the definition of 
the division must be altered to receive it ; it has no brain ! 

The lowest forms of the Molluscs and Articulates are scarcely 
distinguishable from each other, so far as adhesion to the "plan " 
is concerned, and some of the latter division are very near certain 
Echinodermata. As we approach the boundary-lines of the two 
lowest divisions, the approaches become equally close. 

More instructive is the evidence of the relation of the subordi- 
nate classes of any one of these divisions. The conditions of 
those organs or parts which define classes exhibit a regular rela- 
tion, commencing with simplicity and ending with complication ; 
first associated with weak exhibitions of the highest functions of 
the nervous system — at the last displaying the most exalted traits 
found in the series. 

For example : In the classes of Vertebrates we find the lowest 
nervous system presents great simplicity — the brain can not be 
recognized ; next (in lampreys), the end of the nervous axis is 


subdivided, but scarcely according to the complex type that fol- 
lows. In fishes the cerebellum and cerebral hemispheres are 
minute, and the intermediate or optic lobes very large : in the 
reptiles the cerebral hemispheres exceed the optic lobes, while the 
cerebellum is smaller. In birds the cerebellum becomes complex 
and the cerebrum greatly increases. In mammals the cerebellum 
increases in complexity or number of parts, the optic lobes 
diminish, while the cerebral hemispheres become wonderfully 
complex and enlarged, bringing us to the highest development, 
in man. 

The history of the circulatory system in the Vertebrates is the 
same. First, a heart with one chamber, then one with two divis- 
ions : three divisions belong to a large series, and the highest 
possess four. The origins of the great artery of the body, the 
aorta, are first five on each side : they lose one in the succeeding 
class in the ascending scale, and one in each succeeding class or 
order, till the Mammalia, including man, present us, with but one 
on one side. 

From an infinitude of such considerations as the above, we 
derive the certainty that the general arrangement of the various 
groups of the organic world is in scales, the subordinate within 
the more comprehensive divisions. The identification of all the 
parts in such a complexity of organism as the highest animals 
present is a matter requiring much care and attention, and con- 
'stitutes the study of homologies. Its pursuit has resulted in the 
demonstration that every individual of every species of a given 
branch of the animal kingdom is composed of elements common 
to all, and that the differences which are so radical in the higher 
groups are but the modifications of the same elemental parts, 
representing completeness or incompleteness, obliteration or sub- 
division. Of the former character are rudimental organs, of 
which almost every species possesses an example in some part of 
^its structure. 

But we have other and still more satisfactory evidence of the 
meaning of these relations. By the study of embryology we can 
prove most indubitably that the simple and less complex are in- 
ferior to the more complex. Selecting the Vertebrates again as 
an example, the highest form of mammal — e. g., man — presents 
in his earliest stages of embryonic growth a skeleton of cartilage, 
like that of the lamprey ; he also possesses five origins of the 
aorta and five slits on the neck : both which characters belong to 


the lamprey and the shark. If the whole number of these parts 
does not co-exist in the embryonic man, we find in embryos of 
lower forms, more nearly related to the lamprey, that they do. 
Later in the life of the mammal but four aortic origins are found, 
which arrangement, with the heart now divided into two cham- 
bers, from a beginning as a simple tube, is characteristic of the 
class of Vertebrates next in order — the bony fishes. The optic 
lobes of the human brain have also at this time a great predomi- 
nance in size — a character above stated to be that of the same 
class. With advancing development the infant mammal follows 
the scale already pointed out. Three chambers of the heart and 
three aortic origins follow, presenting the condition permanent 
in the Batrachia ; and two origins, with enlarged cerebral hemi- 
spheres of the brain, resemble the reptilian condition. Four 
heart-chambers, and one aortic-root on each side, with slight 
development of the cerebellum, follow, all characters defining the 
crocodiles, and immediately precede the special conditions defin- 
ing the mammals. These are, tlie single aorta-root from .one 
side, and the full development of the cerebellum ; later comes 
that of the cerebrum also in its higher mammalian and human 

Thus we see the order already pointed out to be true, and to 
be an ascending one. This is the more evident as each type or 
class passes through the conditions of those below it, as did the 
mammal ; each scale being shorter as its highest terminus is 
lower. Thus the crocodile passes through the stage of the lam- 
prey, the fish, the batrachian, and the reptile proper. 

h. In Time. — "We have thus a scale of relations of existing 
forms of animals and plants of a remarkable kind, and such as 
to stimulate greatly our inquiries as to its significance. When 
we turn to the remains of the past creation, preserved to us in 
the deposits continued throughout geologic time, we are not 
disappointed, for great light is at once thrown upon the sub- 

We find, in brief, that the lowest division of the animal king- 
dom appeared first, and long before any type of a higher charac- 
ter was created. The Protozoon, Eozoon, is the earliest of 
animals in geologic time, and represents the lowest type of 
animal life now existing. We learn also that the highest branch 
appeared last. No remains of Vertebrates have been found below 
the lower Devonion period, or not until the Echinoderms and 


Molluscs had reached a great pre-eminence. It is diflficiilt to be 
sure whether the Protozoa had a greater numerical extent in the 
earliest periods than now, but there can be no doubt that the 
Coelenterata (corals) and Echinoderms (crinoids) greatly exceeded 
their present bounds in Paleozoic time, so that those at present 
existing are but a feeble remnant. If we examine the sub- 
divisions known as classes, evidence of the nature of the succes- 
sion of creation is still more conclusive. The most polyp-like of 
the Molluscs (Brachiopoda) constituted the great mass of its repre- 
sentatives during Paleozoic time. Among Vertebrates the fishes 
appear first, and had their greatest development in size and num- 
bers during the earliest periods of the existence of the division. 
Batrachia were much the largest and most important of land ani- 
mals during the Carboniferous period, while the higher Verte- 
brates were unknown. The later Mesozoic periods saw the reign 
of reptiles, whose position in structural development has been 
already stated. Finally, the most perfect, the mammal, came 
upon the scene, and in his humblest representatives. In Tertiary 
times Mammalia supplanted the reptiles entirely. 

Thus the structural relations, the embryonic characters, and 
the successive appearance in time of animals coincide. The same 
is very probably true of plants. 

That tlie existing state of the geological record of organic 
types should be regarded as anything but a fragment is, from 
our standpoint, quite preposterous. And, more, it may be as- 
sumed with safety that when completed it will furnish us with 
a series of regular successions, with but slight and regular in- 
terruptions, if any, from the species which represented the sim- 
plest beginnings of life at the dawn of creation, to tliose which 
have displayed complication and power in later or in the present 

For the labors of the paleontologist are daily bringing to light 
structures intermediate between those never before so connected, 
and thus creating lines of succession where before were only in- 
terruptions. Many such instances might be adduced : two might 
be selected as examples from American paleontology ; * i. e., the 

*J'rof. Huxley, in the last anniversary lecture before the Geological Society 
of London, recalls his opinion, enunciated in 1862, that "the positively-ascertained 
truths of Paleontology " negative " the doctrines of progressive modification, which 
suppose that modification to have taken place by a necessary progress from more to 
less embryonic forms, from more to less generalized types, within the limits of the 


near approach to birds made by the reptiles Lselaps and Megadac- 
tylus, and the combination of characters of the old genera Ich- 
thyosaurus and Plesiosaurus in the Polycotylus of Kansas. 

We had no more reason to look for intermediate or connectins: 
forms between such types as these than between any others of 
similar degree of remove from each other with which we are ac- 

period represented by the fossiliferous rocks ; that it shows no evidence of such 
modification ; and, as to the nature of that modification, it yields no evidence what- 
soever tliat tlie earlier members of any long-continued group were more generalized 
in structure than the later ones." 

Respecting this position, he says : " Thus far I have endeavored to expand and 
enforce by fresh arguments, but not to modify in any important respect, the ideas 
submitted to you on a former occasion. But when I come to the propositions re- 
specting progressive modification, it appears to me, with the help of the new light 
which has broken from various quarters, that there is much ground for softening 
the somewhat Brutus-like severity with which I have dealt with a doctrine for the 
truth of which I should have been glad enough to be able to find a good foundation 
in 1862. So far indeed as the Invertebrata and the lower Vertebrata are concerned, 
the facts and the conclusions which are to be drawn from them appear to me to re- 
main what they were. For anything that as yet appears to the contrary, the earliest 
known Marsupials may have been as highly organized as their living congeners ; the 
Permian lizards show no signs of inferiority to those of the present day ; the laby- 
rinthodonts can not be placed below the living salamander and triton ; the Devo- 
nian ganoids are closely related to polypterus and lepidosiren." 

To this it may be replied: 1. The scale of progression of the Vertebrata is 
measured by the condition of the circulatory system, and in some measure by the 
nervous, and not by the osseous : tested by this scale, there has been successional 
complication of structure among Vertebrata in time. 2. The question with the 
evolutionist is, not what types have persisted to the present day, but the order in 
which types appeared in time. 3. The Marsupials, Permian saurians, labyrintho- 
donts, and Devonian ganoids are remarkably generalized groups, and predecessors of 
types widely separated in the present period. 4. Prof. Huxley adduces many such 
examples among the mammalian subdivisions in the remaining portion of his lect- 
ure. 5. Two alternatives are yet open in the explanation of the process of evolu- 
tion : since generalized types, which combine the characters of higher and lower 
groups of later periods, must thus be superior to the lower, the lower must (first) be 
descended from such a generalized form by degradation ; or (second) not descended 
from it at all, but from some lower contemporaneous type by advance ; the higher 
only of the two being derived from the first-mentioned. The last I suspect to be 
a true explanation, as it is in accordance with the homologous groups. This law 
will shorten the demands of paleontologists for time, since, instead of deriving all 
Reptiiia, Batrachia, etc., from common origins, it points to the derivation of higher 
Reptilia of a higher order from higher Reptiiia of a lower order, lower Reptiiia of 
the first from lower Reptiiia of the second ; finally, the several groups of the lowest 
or most generalized order of Reptiiia from a parallel scries of the class below, or 


quaiuted. And inasmuch as almost all groups, as genera, orders, 
etc., which are held to be distinct, but adjacent, present certain 
points of approximation to each other, the almost daily discovery 
of intermediate forms gives us confidence to believe that the 
pointings in other cases will also be realized. 

y. Of Ti^ansitions. 

The preceding statements were necessary to the comprehension 
of the supposed mode of metamorphosis or development of the 
various types of living beings, or, in other words, of the siugle 
structural features which define them. 

As it is evident that the groups of highest rank have had their 
origin in remote ages, cases of transition from one to the other by 
change of character can not be witnessed at the present day. We 
therefore look to the most nearly related divisions, or those of the 
lowest rank, for evidence of such change. 

It is necessary to premise that embryology teaches that all the 
species of a given branch of the animal kingdom (e. g., Verte- 
brate, Mollusc, etc. ) are quite identical in structural character at 
their first appearance on the germinal layer of the yolk of the 
parent eg,g. It shows that the character of the respective groups 
of high rank appear first, then those of less grade, and last of all 
those structures which distinguish them as genera. But among 
the earliest characters which appear are those of the species, and 
some of those of the individual. 

We find the characters of different genera to bear the same re- 
lation to each other that we have already seen in the case of those 
definitive of orders, etc. In a natural assemblage of related genera 
we discover that some are defined by characters found only in the 
embryonic stages of others, while a second will present a perma- 
nent condition of its definitive part, which marks a more ad- 
vanced stage of that highest. In this manner many stages of the 
highest genus appear to be represented by permanent genera in all 
natural groups. Generally, however, this resmblance does not 
involve an entire identity, there being some other immaturities 
found in the highest genus at the time it presents the character 
preserved in permanency by the lower, which the lower loses. 
Thus (to use a very gross illustration) a frog at one stage of growth 
has four legs and a tail ; the salamander always preserves four 
legs and a tail, thus resembling the young frog. The latter is, 
however, not a salamander at that time, because, among other 


things, the skeleton is represented by cartilage only, and the sala- 
mander's is ossified. This relation is therefore an imitation only, 
and is called inexact parallelism. 

As we compare nearer and nearer relations — i. e.^ the genera 
which present fewest points of difference — we find the differences 
between undeveloped stages of the higher and permanent con- 
ditions of the lower to grow fewer and fewer, until we find numer- 
ous instances where the lower genus is exactly the same as the 
undeveloped stage of the higher. This relation is called that of 
exact parallelism. 

It must now be remembered that the permanence of a charac- 
ter is what gives it its value in defining genus, order, etc., in the 
eyes of the systematist. So long as the condition is permanent no 
transition can be seen ; there is therefore no development. If the 
condition is transitional, it defines nothing, and nothing is devel- 
oped ; at least, so says the anti-developmentalist. It is the old 
story of the settler and the Indian : "Will you take owl and I 
take turkey, or I take turkey and you owl ? " 

If we find a relation of exact parallelism to exist between two 
sets of sj^ecies in the condition of a certain organ, and the differ- 
ence so expressed is the only one which distinguishes them as sets 
from each other — if that condition is always the same in each set 
— we call them two genera : if in any species the condition is va- 
riable at maturity, or sometimes the undeveloped condition of the 
part is persistent and sometimes transitory, the sets characterized 
by this difference must be united by the systematist, and the whole 
is called a single genus. 

We know numerous cases where different individuals of the 
same species present this relation of exact parallelism to each 
other ; and, as we ascribe common origin to the individuals of a 
species, we are assured that the condition of the inferior individual 
is, in this case, simply one of repressed growth, or a failure to ful- 
fill the course accomplished by the highest. Thus, certain species 
of the salamandrine genus Amblystoma undergo a metamorphosis 
involving several parts of the osseous and circulatory systems, etc., 
while half grown ; others delay it till fully grown ; one or two 
species remain indifferently unchanged or changed, and breed in 
either condition, while another species breeds unchanged, and has 
never been known to complete a metamorphosis. 

The nature of the relation of exact parallelism is thus explained 
to be that of checked or advanced growth of individuals having a 


common origin. The relation of inexact parallelism is readily ex- 
plained as follows : With a case of exact imrallelism in the mind, 
let the repression producing the character of form B parallelize 
the latter with a stage of form A in which a second part is not 
quite mature : we will have a slight want of correspondence be- 
tween the two. Form B will be immature in but one point, the 
incompleteness of A higher being seen in two points. If we 
suppose the immaturity to consist in a repression at a still earlier 
point in the history of the higher, the latter will be undeveloped 
in other points also : thus, the spike-horned deer of South Amer- 
ica have the horn of the second year of the North American genus. 
They would be generically identical with that stage of the latter, 
were it not that these still possess their milk dentition at two 
years of age. In the same way the nature of the parallelisms seen 
in higher groups, as orders, etc., may be accounted for. 

The theory of homologous groups furnishes important evidence 
in favor of derivation. Many orders of animals (probably all, 
when we come to know them) are divisible into two or more sec- 
tions, which I have called Jiomologous. These are series of genera 
or families, which differ from each other by some marked charac- 
ter, but whose contained genera or families differ from each other 
in the same points of detail, and in fact correspond exactly. So 
striking is this correspondence that were it not for the general and 
common character separating the homologous series, they would 
be regarded as the same, each to each. Now, it is remarkable that, 
where studied, the difference common to all the terms of two ho- 
mologous groups is found to be one of inexact parallelism, which 
has been shown above to be evidence of descent. Homologous 
groups always occupy different geographical areas on the earth's 
surface, and their relation is precisely that which holds between 
successive groups of life in the periods of geologic time.* 

In a Avord, we learn from this source that distinct geologic 
epochs co-exist at the same time on the earth. I have been forced 
to this conclusion f by a study of the structure of terrestrial life, 
and it has been remarkably confirmed by the results of recent 
deep-sea dredgings made by the United States Coast Survey in the 
Gulf Stream, and by the British naturalists in the North Atlantic. 
These have brought to light types of Tertiary life, and of even 

* The extinct family of the NimravidiB, which is homologous with the existing 
family of Felid<B, has been discovered since this was written. (Ed. 1886.) 
f " Origin of Genera," pp. TO, 11, 79. 


the still more ancient Cretaceous periods, living at the present 
day.* That this discovery invalidates in any wise the conclusions 
of geology respecting lapse of time is an unwarranted assumption 
that some are forward to make. If it changes the views of some 
respecting the parallelism or co-existence of faunae in different 
regions of the earth, it is only the anti-developmentalists whose 
position must be changed. 

For, if we find distinct geologic faunas, or epochs defined by 
faunae, co-existing during the present period, and fading or merg- 
ing into one another as they do at their geographical boundaries, 
it is proof positive that the geologic epochs and periods of past 
ages had in like manner no trenchant boundaries, but also passed 
the one into the other. The assiimption that the apparent inter- 
ruptions are the result of transfer of life rather than destruction, 
or of want of opportunities of preservation, is no doubt the true 


8. Rationale of Development. 

a. In Characters of Higher Groups. — It is evident in the case 
of the species in which there is an irregularity in the time of com- 
pletion of metamorphosis, that some individuals traverse a longer 
developmental line than those which remain more or less incom- 
plete. As both accomplish growth in the same length of time, it 
is obvious that it proceeds with greater rapidity in one sense in 
that which accomplishes most ; its growth is said to be accelerated. 
This phenomenon is especially common among insects, where the 
females of perfect males are sometimes larvae or nearly so, or pupae, 
or lack wings or some character of final development. Quite as 
frequently, some males assume characters in advance of others, 
sometimes in connection with a peculiar geographical range. 

In cases of exact parallelism we reasonably suppose the cause 
to be the same, since the conditions are identical, as has been 
shown ; that is, the higher conditions have been produced by a 
crowding back of the earlier characters and an acceleration of 
growth, so that a given succession in order of advance has extended 
over a longer range of growth than its predecessor in the same al- 
lotted time. That allotted time is the period before maturity and 
reproduction, and it is evident that as fast as modifications or 
characters should be assumed sufficiently in advance of that pe- 
riod, so certainly would they be conferred upon the offspring by 

* Most of the deep-sea forms are, however, degenerate forms of existing orders. 
(Ed. 1886.) 


reproduction. The acceleration in the assumption of a character, 
progressing more rapidly than the same in another character, must 
soon produce, in a type whose stages were once the exact parallel 
of a permanent lower form, the condition of inexact parallelism. 
As all the more comprehensive groups present this relation to each 
other, we are compelled to believe that acceleration has been the 
principle of their successive evolution during the long ages of ge- 
ologic time. 

Each type has, however, its day of supremacy and perfection 
of organism, and a retrogression in these respects has succeeded. 
This has no doubt followed a law the reverse of acceleration, which 
has been called retardation. By the increasing slowness of the 
growth of the individuals of a genus, and later and later assump- 
tion of the characters of the latter, they would be successively lost. 

To what power shall we ascribe this acceleration, by which the 
first beginnings of structure have accumulated to themselves 
through the long geologic ages complication and power, till from 
the germ that was scarcely born into a sand-lance, a human being 
climbed the complete scale, and stood easily the chief of the 
whole ? 

In the cases of species, where some individuals develop farther 
than others, we say the former possess more growth-force, or 
"■ vigor," than the latter. We may therefore say that higher types 
of structure possess more *' vigor" than the lower. This, how- 
ever, we do not know to be true, nor can we readily find means to 
demonstrate it. 

The food which is taken by an adult animal is either assimi- 
lated, to be consumed in immediate activity of some kind, or 
stored for future use, and the excess is re-jected from the body. 
We have no reason to suppose that the same kind of material 
could be made to subserve the production of force by any other 
means than that furnished by a living animal organism. The ma- 
terial from which this organism is constructed is derived first from 
the parent, and afterward from the food, etc., assimilated by the 
individual itself so long as growth continues. As it is the activity 
of assimilation directed to a special end during this latter period 
which we suppose to be increased in accelerated development, the 
acceleration is evidently not brought about by increased facilities 
for obtaining the means of life which the same individual possesses 
as an adult. That it is not in consequence of such increased fa- 
cilities possessed by its parents over those of the type preceding it 


seems equally improbable when we consider that the characters in 
which the parent's advance has appeared are rarely of a nature to 
increase those facilities. 

The nearest approach to an explanation that can be offered 
appears to be somewhat in the following direction : 

There is every reason to believe that the character of the 
atmosphere has gradually changed during geologic time, and that 
various constituents of the mixture have been successively re- 
moved from it, and been stored in the solid material of the 
earth's crust in a state of combination. Geological chemistry has 
shown that the cooling of the earth has been accompanied by the 
precij^itation of many substances only gaseous at high tempera- 
tures. Hydrochloric and sulphuric acids have been transferred 
to mineral deposits or aqueous solutions. The removal of carbonic- 
acid gas and the vapor of water has been a process of much slower 
progress, and after the expiration of all the ages a proportion of 
both yet remains. Evidence of the abundance of the former in 
the earliest periods is seen in the vast deposits of limestone rock ; 
later, in the prodigious quantities of shells which have been 
elaborated from the same in solution. Proof of its abundance 
in the atmosphere in later periods is seen in the extensive de- 
posits of coal of the Carboniferous, Triassic, and Jurassic periods. 
If the most luxuriant vegetation of the present day takes but fifty 
tons of carbon from the atmosphere in a century, per acre, thus 
producing a layer over that extent of less than a third of an inch 
in thickness, what amount of carbon must be abstracted in order 
to produce strata of thirty-five feet in depth ? No doubt it occu- 
pied a long period, but the atmosphere, thus deprived of a large 
proportion of carbonic acid, would in subsequent periods undoubt- 
edly possess an improved capacity for the support of animal life. 

The successively higher degree of oxidization of the blood in 
the organs designed for that function, whether performing it in 
water or air, would certainly accelerate the performances of all 
the vital functions, and among others that of growth. Thus it 
may be that acceleration can be accounted for, and the process of 
the development of the orders and sundry lesser groups of the 
Vertebrate kingdom indicated ; for, as already pointed out, the 
definitions of such are radically placed in the different structures 
of the organs which aerate the blood and distribute it to its 
various destinations. 

But the great question, What determined the direction of this 


acceleration ? remains unanswered. One can not understand why 
more liigbly oxidized blood should hasten the growth of partition 
of the ventricle of the heart in the serpent, the more perfectly to 
separate the aerated from the impure fluid ; nor can we see why a 
more perfectly constructed circulatory system, sending purer 
blood to the brain, should direct accelerated growth to the cere- 
bellum or cerebral hemispheres in the crocodile'. 

b. In Characters of the Specific Kind. — Some of the charac- 
ters usually placed in the specific category have been shown to be 
the same in kind as those of higher categories. The majority are, 
however, of a different kind, and have been discussed several 
pages back. 

The cause of the origin of these characters is shrouded in as 
much mystery as that of those which have occupied the pages im- 
mediately preceding. As in that case, we have to assume, as 
Darwin has done, a tendency in Nature to their production. 
This is what he terms "the principle of variation." Against an 
unlimited variation the great law of heredity or atavism has ever 
been opposed, as a conservator and multiplier of type. This 
principle is exemplified in the fact that like produces like — that 
children are like their parents, frequently even in minutiae. It 
may be compared to habit in metaphysical matters, or to that 
singular love of time or rhythm seen in man and lower animals, 
in both of which the tendency is to repeat in continual cycles a 
motion or state of the mind or sense. 

Further, only a proj^ortion of the lines of variation is supposed 
to have been perpetuated, and the extinction of intermediate 
forms, as already stated, has left isolated groups or species. 

The effective cause of these extinctions is stated by Darwin to 
have been a "natural selection" — a proposition which distin- 
guishes his theory from other development hypotheses, and which 
is stated in brief by the expression, "the survival of the fit- 
test." Its meaning is this: that those characters appearing as 
results of this spontaneous variation which are little adapted to 
the conflict for subsistence, with the nature of the supply, or 
with rivals in its pursuit, dwindle and are sooner or later ex- 
tirpated ; while those which are adapted to their surroundings, 
and favored in the struggle for means of life and increase, pre- 
dominate, and ultimately become the centers of new variation. 
"I am convinced," says Darwin, "that natural selection has 
been the main, but not exclusive, means of modification." 


That it has been to a large extent the means of preservation of 
those structures known as specific, must, I think, be admitted. 
They are related to their peculiar surroundings very closely, and 
are therefore more likely to exist under their influence. Thus, if 
a given genus extends its range over a continent, it is usually 
found to be represented by i^eculiar species — one in a maritime 
division, another in the desert, others in the forest, in the swamp 
or the elevated areas of the region. The wonderful interdepend- 
ence shown by Darwin to exist between insects and plants in the 
fertilization of the latter, or between animals and their food- 
plants, would almost induce one to believe that it were the true 
expression of the whole law of development. 

But the following are serious objections to its universal appli- 
cation : 

First : The characters of the higher groups, from genera up, 
are rarely of a character to fit their possessors especially for sur- 
rounding circumstances ; that is, the differences which separate 
genus from genus, order from order, etc., in the ascending scale 
of each, do not seem to present a superior adaptation to surround- 
ing circumstances in the higher genus to that seen in the lower 
genus, etc. Hence, superior adaptation could scarcely have 
caused their selection above other forms not existing. Or, in 
other words, the very differences in structure which indicate suc- 
cessional relation, or which measure the steps of progress, seem to 
be equally well fitted for their surroundings. 

Second : The higher groups, as orders, classes, etc., have been 
in each geologic period alike distributed over the whole earth, 
under all the varied circumstances offered by climate and food. 
Their characters do not seem to have been modified in reference 
to these. Species, and often genera, are, on the other hand, 
eminently restricted according to climate, and consequently vege- 
table and animal food. 

The law of development which we seek is indeed not that 
which preserves the higher forms and rejects the lower after their 
creation, but that which explains why higher forms were created 
at all. Why in the results of a creation we see any relation of 
higher and lower, and not rather a world of distinct types, each 
perfectly adapted to its situation, but none properly higher than 
another in an ascending scale, is the primary question. Given 
the principle of advance, then natural selection has no doubt 
modified the details ; but in the successive advances we can 


scarcely believe such a principle to be influential. "We look 
rather upon a progress as the result of the expenditure of some 
force fore-arranged for that end. 

It may become, then, a question whether in characters of high 
grade the habit or use is not rather the result of the acquisition of 
the structure than the structure the result of the encouragement 
oifered to its assumed beginnings by use, or by liberal nutrition 
derived from the increasingly superior advantages it offers. 

c. The Phyncal Origin of Man. 

If the hypothesis here maintained be true, man is the de- 
scendant of some pre-existent generic type, the which, if it were 
now living, we would probably call an ape. 

Man and the chimpanzee were in Linnaeus's system only two 
species of the same genus, but a truer anatomy places them in 
separate genera and distinct families. There is no doubt, how- 
ever, that Cuvier went much too far when he proposed to con- 
sider Homo as the representative of an order distinct from the 
Quadrumana, under the name of Bimana. The structural differ- 
ences will not bear any such inter}) relation, and have not the 
same value as those distinguishing the orders of Mammalia ; as, 
for instance, between Carnivora and bats, or the cloven-footed ani- 
mals and the rodents, or rodents and edentates. The differences 
between man and the chimpanzee are, as Huxley well puts it, 
much less than those between the chimpanzee and lower Quadru- 
mana, as lemurs, etc. In fact, man is the type of a family, 
Hominidae, of the order Quadrumana, as indicated by the charac- 
ters of the dentition, extremities, brain, etc. The reader who 
may have any doubts on this score may read the dissections of 
Geoffroy St. Hilaire, made in 1856, before the issue of Darwin's 
"Origin of Species." He informs us that the brain of man is 
nearer in structure to that of the orang than the orang's is to 
that of the South American howler, and that the orang and 
howler are more nearly related in this regard than are the howler 
and the marmoset. 

The modifications presented by man have, then, resulted from 
an acceleration in development in some respects, and retardation 
perhaps in others. But until the combination now characteristic 
of the genus Homo was attained, the being could not properly be 
called man. 

And here it must be observed that as an organic type is char- 


acterized by the co-existence of a number of peculiarities which 
iiave been developed independently of each other, its distinctive 
features and striking functions are not exhibited until that co- 
existence is attained which is necessary for these ends. 

Hence, the characters of the human genus were probably de- 
veloped successively ; but few of the indications of human superi- 
ority appeared until the combination was accomplished. Let the 
opposable thumb be first perfected, but of what use would it be 
in human affairs without a mind to direct ? And of what use a 
mind without speech to unlock it ? x\nd speech could not be 
possible though all the muscles of the larynx but one were devel- 
oped, or but a slight abnormal convexity in one pair of cartilages 

It would be an objection of little weight could it be truly 
urged that there have as yet no remains of ape-like men been dis- 
covered, for we have frequently been called upon in the course of 
paleontological discovery to bridge greater gaps than this, and 
greater remain, which we expect to fill. But we have ape-like 
characters exhibited by more than one race of men yet existing. 

But the remains of that being which is supposed to have been 
the progenitor of man may have been discovered a short time since 
in the cave of Naulette, Belgium, with the bones of the extinct 
rhinoceros and elephant. 

We all admit the existence of higher and lower races, the latter 
being those which we now find to present greater or less ajoproxi- 
mations to the apes. The peculiar structural characters that be- 
long to the negro in his most typical form are of that kind, how- 
ever great may be the distance of his remove therefrom. The 
flattening of the nose and prolongation of the Jaws constitute such 
a resemblance ; so are the deficiency of the calf of the leg, and the 
obliquity of the pelvis, which approaches more the horizontal po- 
sition than it does in the Caucasian. The investigations made at 
Washington during the war with reference to the physical charac- 
teristics of the soldiers show that the arms of the negro are from 
one to two inches longer than those of the whites : another ap- 
proximation to the ape. In fact, this race is a species of the 
genus Homo, as distinct in character from the Caucasian as those 
we are accustomed to recognize in other departments of the ani- 
mal kingdom ; but he is not distinct by isolation, since intermedi- 
ate forms between him and the other species can be abundantly 


And here let it be particularly observed that two of the most 
prominent characters of the negro are those of immature stages of 
the Indo-European race in its characteristic types. The deficient 
calf is the character of infants at a very early stage ; but, what is 
more important, the flattened bridge of the nose and shortened 
nasal cartilages are universally immature conditions of the same 
parts in the Indo-European. Any one may convince himself of 
that by examining the physiognomies of infants. In some races — 
e. g., the Slavic — this undeveloped character persists later than in 
some others. The Greek nose, with its elevated bridge, coincides 
not only with aesthetic beauty, but with developmental perfection. 

This is, however, only "inexact parallelism," as the charac- 
ters of the hair, etc., can not be explained on this principle among 
existing races. The embryonic characters mentioned are probably 
a remnant of those characteristic of the primordial race or species. 

But the man of Naulette, if he be not a monstrosity, is a still 
more distinct and ape-like species. The chin, that marked char- 
acter of other species of men, is totally wanting, and the dentition 
is quite approximate to the man-like apes, and different from that 
of modern men. The form is very massive, as in apes. That he 
was not abnormal is rendered probable by approximate characters 
seen in a jaw from the cave of Puy-sur-Aube, and less marked in 
the lowest races of Australia and New Caledonia. 

As to the single or multiple origin of man, science as yet fur- 
nishes no answer. It is very probable that, in many cases, the 
species of one genus have descended from corresponding species of 
another by change of generic characters only. It is a remarkable 
fact that the orang possesses the peculiarly developed malar bones 
and the coiDper color characteristic of the Mongolian inhabitants 
of the regions in which this animal is found, while the gorilla ex- 
hibits the prognathic jaws and black hue of the African races near 
whom he dwells. This kind of geographical imitation is very 
common in the animal kingdom. 


It is infinitely improbable that a being endowed with such ca- 
pacities for gradual progress, as man has exhibited, should have 
been full-fledged in accomplishments at the moment when he 
could first claim his high title, and abandon that of his simian 
ancestors. We are, therefore, required to admit the growth ot 
human intelligence from a primitive state of inactivity and abso- 


lute ignorance ; including the development of one important mode 
of its expression — speech ; as well as that of the moral qualities, 
and of man's social system — the form in which his ideas of moral- 
ity are first displayed. 

The expression "evolution of morality" need not offend, for 
the question in regard to the laws of this evolution is the really 
important part of the discussion, and it is to the opposing views 
on this point that the most serious interest attaches. 

a. Development of Intelligence. 

If the brain is the organ of mind, we may be surprised to find 
that the brain of the intelligent man scarcely differs in structure 
from that of the ape. Whence, then, the difference of power ? 
Though no one will now deny that many of the Mammalia are 
capable of reasoning upon observed facts, yet how greatly the re- 
sults of tliis capacity differ in number and importance from those 
achieved by human intelligence ! Like water at the temperatures 
of 50° and 53°, where we perceive no difference in essential char- 
acter, so between the brains of the lower and higher monkeys no 
difference of function or of intelligence is perceptible. But what 
a difference do the two degrees of temperature from 33° to 31° 
produce in water ! In like manner the difference between the 
brain of the higher ape and that of man is accompanied by a dif- 
ference in function and power, on which man's earthly destiny 
depends. In development, as with the water, so with the higher, 
ape ; some Eubicon has been crossed, some floodgate has been 
opened, which marks one of Nature's great transitions, such as 
have been called " expression-points " of progress. 

What point of progress in such a history would account for 
this accession of the powers of the human intelligence ? It has 
been answered, with considerable confidence — the power of speech. 
Let us picture man without speech. Each generation would learn 
nothing from its predecessors. Whatever originality or observa- 
tion might yield to a man would die with him. Each intellectual 
life would begin where every other life began, and would end at a 
point only differing with its original capacity. Concert of action, 
by which man's power over the material world is maintained, 
would not exceed, if it equaled, that which is seen among the 
bees ; and the material results of his labors would not extend be- 
yond securing the means of life and the employment of the sim- 
plest modes of defense and attack. 


The first men, therefore, are looked upon by the develop- 
mentalists as extremely embryonic in all that characterizes hu- 
manity, and they appeal to the facts of history in support of this 
yiew. If they do not derive much assistance from written his- 
tory, evidence is found in the more enduring relics of human 

The opposing view is, that the races which present or have 
presented this condition of inferiority or savagery have reached it 
by a process of degradation from a higher state — as some believe, 
through moral delinquency. This position may be true in certain 
cases, which represent perhaps a condition of senility, but in gen- 
eral we believe that savagery was the condition of the first man, 
which has in some races continued to the present day. 

^. Evidence from ArchcBology. 

As the object of the present essay is not to examine fully into 
the evidences for the theories of evolution here stated, but rather 
to give a sketch of such theories and their connection, a few facts 
only will be noticed. 

Improvement in the Use of Materials. — As is well known, the 
remains of human handiwork of the earliest periods consist of 
nothmg but rude implements of stone and bone, useful only in 
procuring food and preparing it for use. Even when enterprise 
extended beyond the ordinary routine, it was restrained by the 
want of proper instruments. Knives and other cutting imple- 
ments of flint still attest the skill of the early races of men from 
Java to the Cape of Good Hope, from Egypt to Ireland, and 
through North and South America. Hatchets, spear-heads and 
ornaments of serpentine, granite, silex, clay slates, and all other 
suitable rock materials, are found to have been used by the first 
men, to the exclusion of metals, in most of the regions of the 

Later, the probably accidental discovery of the superiority of 
some of the metals resulted in the substitution of them for stone 
as a material for cutting implements. Copper — the only metal 
which, while malleable, is hard enough to bear an imperfect edge 
— was used by succeeding races in the Old World and the New. 
Implements of this material are found scattered over extensive 
regions. So desirable, however, did the hardening of the material 
appear for the improvement of the cutting edge, that combinations 
with other metals were sought for and discovered. The alloy with 


tin, forming bronze and brass, was discovered and used in Europe, 
while that with silver appears to have been most readily produced 
in America, and was consequently used by the Peruvians and other 

The discovery of the modes of reducing iron ores placed in 
the hands of man the best material for bringing to a shape 
convenient for his needs the raw material of the world. All im- 
provements in this direction made since that time have been in 
the quality of iron itself, and not through the introduction of any 
new metal. 

The prevalent phenomena of any given period are those which 
give it its character, and by which we distinguish it. But this 
fact does not exclude the co-existence of other phenomena belong- 
ing to prior or subsequent stages. Thus during the many stages 
of human progress there have been men more or less in advance 
of the general body, and their characteristics have given a pecul- 
iar stamp to the later and higher condition of the whole. It 
furnishes no objection to this view that we find, as might have 
been anticipated, the stone, bronze, and iron periods overlapping 
one another, or men of an inferior culture supplanting in some 
cases a superior people. A case of this kind is seen in North 
America, where the existing "Indians," stone-men, have suc- 
ceeded the mound-builders, copper-men. The successional rela- 
tion of discoveries is all that it is necessary to prove, and this 
seems to be established. 

The period at which the use of metallic implements was intro- 
duced is unknown, but Whitney says that the language of the 
Aryans, the ancestors of all the modern Indo-Europeans, indicates 
an acquaintance with such implements, though it is not certain 
whether those of iron are to be included. The dispersion of the 
daughter races, the Hindoos, the Pelasgi, Teutons, Celts, etc., 
could not, it is thought, have taken place later than 3000 b. c. — 
a date seven hundred years prior to that assigned by the old chro- 
nology to the Deluge. Tliose races co-existed with the Egyptian 
and Chinese nations, already civilized, and as distinct from each 
other in feature as they are now. 

Improvement in Architecture.— "The earliest periods, then, were 
characterized by the utmost simplicity of invention and construc- 
tion. Later, the efforts for defense from enemies and for architect- 
ural display, which have always employed so much time and 
power, began to be made. The mcgalithic period has left traces 


over rmich of the earth. The great masses of stone piled on each 
other in the simplest form in Southern India, and the circles of 
stones planted on end in England at Stonehenge and Abury, and 
in Peru at Sillustani, are relics of that period. More complex 
are the great Himyaritic walls of Arabia, the works of the ances- 
tors of the Phoenicians in Asia Minor, and the titanic workmanship 
of the Pelasgi in Greece and Italy. In the iron age we find gra- 
nitic hills shaped or excavated into temples ; as, for example, 
everywhere in Southern India. Near Madura the circumference 
of an acropolis-like hill is cut into a series of statues in high re- 
lief, of sixty feet in elevation. Easter Island, composed of two 
volcanic cones, one thousand miles from the west coast of South 
America, in the bosom of the Pacific, possesses several colossi cut 
from the intrusive basalt, some in high relief on the face of the 
rock, others in detached blocks removed by human art from their 
original positions and brought nearer the sea-shore. 

Finally, at a more advanced stage, the more ornate and com- 
plex structures of Central America, of Cambodia, Nineveh and 
Egypt, represent the period of greatest disi)lay of architectural ex- 
penditure. The same amount of human force has perhaps never 
been expended in this direction since, though higher conceptions 
of beauty have been developed in architecture with increasing in- 

Man has passed through the block-and-brick building period 
of his boyhood, and should rise to higher conceptions of what is 
the true disposition of power for " him who builds for aye," and 
learn that " spectacle " is often the unwilling friend of progress. 

No traces of metallic implements have ever been found in the 
salt-mines of Armenia, the turquoise-quarries in Arabia, the cities 
of Central America, or the excavations for mica in North Carolina, 
while the direct evidence points to the conclusion that in those 
places flint was exclusively used. 

The simplest occupations, as requiring the least exercise of 
mind, are the pursuit of the chase and the tending of flocks and 
herds. Accordingly, we find our first parents engaged in these 
occupations. Cain, we are told, was, in addition, a tiller of the 
ground. Agriculture in its simplest forms requires but little 
more intelligence than the pursuits just mentioned, though no 
employment is capable of higher development. If we look at the 
savage nations at present occupying nearly half the land surface 
of the earth, we shall find many examples of the former indus- 


trial condition of our race preserved to the present day. Many 
of them had no knowledge of the use of metals until they ob- 
tained it from civilized men who visited them, while their pur- 
suits were and are those of the chase, tending domestic animals, 
and rudimental agriculture. 

y. Development of the Fine Arts. 

If we look at representation by drawing or sculpture, we find 
that the efforts of the earliest races of which we have any knowl- 
edge were quite similar to those which the untaught hand of in- 
fancy traces o\\ its slate or the savage depicts on the rocky faces 
of hills. The circle or triangle for the head and body, and 
straight lines for the limbs, have been preserved as the first at- 
tempts of the men of the stone period, as they are to this day the 
sole representations of the human form which the North American 
Indian places on his buffalo robe or mountain precipice. The 
stiff, barely outlined form of the deer, the turtle, etc., are liter- 
ally those of the infancy of civilized man. 

The first attempts at sculpture were marred by the influence 
of modism. Thus the idols of Coban and Palenque, with human 
faces of some merit, are overloaded with absurd ornament, and 
deformed into frightful asymmetry, in compliance with the de- 
mand of some imperious mode. In later days we have the stiff, 
conventionalized figures of the palaces of Nineveh and the temples 
of Eg}^t, where the representation of form has somewhat improved, 
but is too often distorted by false fashion or imitation of some 
unnatural standard, real or artistic. This is distinguished as the 
day of archaic sculpture, which disappeared with the Etruscan 
nation. So the drawings of the child, when he abandons the 
simple lines, are stiff and awkward, and but a stage nearer true 
representation ; and how often does he repeat some peculiarity or 
absurdity of his own ! 

The introduction of the action and pose of life into sculpture 
was not known before the early days of Greece, and it was there 
that the art was brought to perfection. When art rose from its 
mediaeval slumber, much the same succession of development may 
be discovered. First, the stiff figures, with straightened limbs 
and cylindric drapery, found in the old Northern churches — then 
the forms of life that now adorn the porticoes and palaces of the 
cities of Germanv. 


6. Rationale of the Development of Intelligence. 

The history of material development shows that the transition 
from stage to stage of development, experienced by the most per- 
fect forms of animals and plants in their growth from the primor- 
dial cell, is similar to the succession of created beings which the 
geological epochs produced. It also shows that the slow assump- 
tion of main characters in the line of succession in early geological 
periods produced the condition of inferiority, while an increased 
rapidity of growth in later days has resulted In an attainment of 
superiority. It is not to be supposed that in "acceleration" the 
period of growth is shortened ; on the contrary, it continues the 
same. Of two beings whose characters are assumed at the same 
rate of succession, that with the quickest or shortest growth is 
necessarily inferior. ''Acceleration" means a gradual increase of 
the rate of assumption of successive characters in the same period 
of time. A fixed rate of assumption of characters, with gradual 
increase in the length of the period of growth, would produce the 
same result — viz., a longer developmental scale and the attainment 
of an advanced position. The first is in part the relation of sexes 
of a species ; the last of genera, and of other types of creation. If 
from an observed relation of many facts we derive a law, we are 
permitted, when we see in another class of facts similar relations, 
to suspect that a similar law has operated, differing only in its ob- 
jects. We find a marked resemblance between the facts of struct- 
ural progress in matter and the phenomena of intellectual and 
spiritual progress. 

If the facts entering into the categories enumerated in the pre- 
ceding section bear us out, we conclude that in the beginning of 
human history the progress of the individual man was very slow, 
and that but little was attained to ; that, through the profitable 
direction of human energy, means were discovered from time to I 

time by which the process of individual development in all meta- 
physical qualities has been accelerated ; and that up to the pres- 
ent time the consequent advance of the whole race has been at an 
increasing rate of progress. This is in accordance with the gen- 
eral principle, that high development in intellectual things is 
accomplished by rapidity in traversing the preliminary stages of 
inferiority common to all, while low development signifies slug- 
gishness in that progress, and a corresponding retention of in- 


How much meaning may we not see, from this standpoint, 
in the history of the intelligence of our little ones ! First they 
crawl, they walk on all-fours ; when they first assume the erect 
position they are generally speechless, and utter only inarticulate 
sounds. When they run about, stones and dirt, the objects that 
first meet the eye, are the delight of their awakening powers ; but 
these are all cast aside when the boy obtains his first jackknife. 
Soon, however, reading and writing open a new world to him ; 
and, finally, as a mature man he seizes the forces of Nature, and 
steam and electricity do his bidding in the active pursuit of power 
for still better and higher ends. 

So with the history of the species : first, the quadrumane ; 
then the speaking man, whose humble industry was, however, 
confined to the objects that came first to hand, this being the 
"stone age "of pre-historic time. When the use of metals was 
discovered, the range of industries expanded wonderfully, and the 
"iron age" saw many striking efforts of human power. With the 
introduction of letters it became possible to record events and ex- 
periences, and the spread of knowledge was thereby greatly in- 
creased, and the delays and mistakes of ignorance correspondingly 
diminished in the fields of the world's activity. 

From the first we see in history a slow advance as knowledge 
gained by the accumulation of tradition and by improvements in 
habit based on experience ; but how slow was this advance while 
the use of the metals was still unknown ! The iron age brought 
with it not only new conveniences, but increased means of future 
progress ; and here we have an acceleration in the rate of advance. 
With the introduction of letters this rate was increased manifold, 
and in the application of steam we have a change equal in utility 
to any that has preceded it, and adding to the possibilities of fu- 
ture advance in many directions. By it power, knowledge, and 
means of happiness were to be distributed among the many. 

The uses to which human intelligence has successively applied 
the materials furnished by Nature have been — first, subsistence 
and defense ; second, the accumulation of power in the shape of a 
representative of that labor which the use of matter involves — in 
other Avords, the accumulation of wealth. The possession of this 
power involves new possibilities, for opportunity is offered for the 
special pursuits of knowledge and the assistance of the weak or 
undeveloped part of mankind in its struggles. 

Thus, while the first men possessed the power of speech, and 


could advance a little in knowledge through the accumulation of 
the experiences of their predecessors, they possessed no means of 
accumulating the power of labor, no control over the activity of 
numbers — in other words, no wealth. 

But the accumulation of knowledge finally brought this ad- 
vance about. The extraction and utilization of the metals, espe- 
cially iron, formed the most important step, since labor was thus 
facilitated and its productiveness increased in an incalculable de- 
gree. We have little evidence of the existence of a medium of ex- 
change during the first or stone period, and no doubt barter was 
the only form of trade. Before the use of metals, shells and other 
objects were used ; remains of money of baked clay have been 
found in Mexico. Finally, though in still ancient times, the pos- 
session of wealth in money gradually became possible and more 
common, and from that day to this avenues for reaching this stage 
in social progress have ever been opening. 

But wealth merely indicates a stage of progress, since it is but 
a comparative term. All men could not become rich, for in that 
case all would be equally poor. But labor has a still higher goal ; 
for, thirdly, as capital, it constructs and employs machinery, 
which does the work of many hands, and thus cheapens products, 
which is equivalent in effect to an accumulation of wealth to the 
consumer. And this increase of power may be used for the intel- 
lectual and spiritual advance of men, or, otherwise, at the will of 
the men thus favored. Machinery places man in the position of a 
creator, operating on Xature through an increased number of 
'"secondary causes." 

Development of intelligence is seen, then, in the following 
directions : First, in the knowledge of facts, including science ; 
second, in language ; and, as consequences of these, the accumula- 
tion of power by development — first, of means of subsistence ; and, 
second, of mechanical invention ; and, third, in the apprehension 
of beauty. 

Thus, we have two terms to start with in estimating the be- 
ginning of human development in knowledge and power : first, 
the primary capacities of the human mind itself ; second, a mate- 
rial world, whose infinitely varied components are so arranged as 
to yield results to the energies of that mind. For example, the 
transition-points of vaporization and liquefaction are so placed as 
to be within the reach of man's agents ; their weights are so fixed 
as to accord with the muscular or other forces which he is able to 


exert ; and other living organizations are subject to his conven- 
ience and rule, and not, as in previous geological periods, entirely 
beyond his control. These two terms being given, it is maintained 
that the present situation of the most civilized men has been at- 
tained through the operation of a law of mutual action and reac- 
tion — a law whose results, seen at the present time, liave depended 
on the acceleration or retardation of its rate of action ; which rate 
has been regulated, according to the degree in which a third great 
term, viz., the law of moral or (what is the same thing) true re- 
ligious development, has been combined in the plan. What it is 
necessary to establish in order to prove the above hypothesis is — 

I. That in each of the particulars above enumerated the devel- 
opment of the human species is similar to that of the individual 
from infancy to maturity. 

II. That from a condition of subserviency to the laws of mat- 
ter, man's intelligence enables him, by an accumulation of power, 
to become in a sense independent of those laws, and to pursue a 
course of intellectual and spiritual progress. 

III. That failure to accomplish a moral or spiritual develop- 
ment will again reduce him to a subserviency to the laws of 

This brings us to the subject of moral development. And here 
I may be allowed to suggest that the weight of the evidence is 
opposed to the philosophy, " falsely so called," of necessitarianism, 
which asserts that the first two terms alone were sufficient to work 
out man's salvation in this world and the next ; and, on the other 
hand, to that anti-philosophy which asserts that all things in hu- 
man progress, intellectual and moral, are regulated by immediate 
divine interposition instead of through instrumentalities. Hence, 
the subject divides itself at once into two great departments — viz., 
that of the development of mind or intelligence, and that of the 
development of morality. 

That these laws are distinct there can be no doubt, since in 
the individual man one of them may produce results without the 
aid of the other. Yet it can be sho^wn that each is the most in- 
valuable aid and stimulant to the other, and most favorable to 
the rapid advance of the mind in either direction. 


In examining this subject, we first inquire (Section a) whether 
there is any connection between physical and moral or religious 


development ; then (/S), what indications of moral development 
may be derived from history. Finally (y), a correlation of the 
results of these inquiries, with the nature of the religious develop- 
ment in the individual, is attempted. Of course in so stupendous 
an inquiry hut a few leading points can be presented here. 

If it be true that the period of human existence on the earth 
has seen a gradually increasing predominance of higher motives 
over lower ones among the mass of mankind, and if any parts of 
our metaphysical being have been derived by inheritance from 
pre-existent beings, we are incited to the inquiry whether any of 
the moral qualities are included among the latter ; and whether 
there be any resemblance between moral and intellectual develop- 

Thus, if there have been a physical derivation from a pre- 
existent genus, and an embryonic condition of those physical 
characters which distinguish Homo — if there has been also an 
embryonic or infantile stage in intellectual qualities — we are led 
to inquire whether the development of the individual in moral 
nature will furnish us with a standard of estimation of the suc- 
cessive conditions or present relations of the human species in 
this aspect also. 

a. Relations of Physical and Moral Nature. 

Although, cwteris paribus, men are much alike in the deeper 
qualities of their nature, there is a range of variation which is 
best understood by a consideration of the extremes of such varia- 
tion as seen in men of different latitudes, and women and chil- 

{a) In Children. — Youth is distinguished by a peculiarity, 
which no doubt depends upon an immature condition of the nerv- 
ous center concerned, which might be called nervous impressi- 
bility. It is exhibited in a greater tendency to tearfulness, in 
timidity, less mental endurance, a greater facility in acquiring 
knowledge, and more ready susceptibility to the influence of 
sights, sounds, and sensations. In both sexes the emotional 
nature predominates over the intelligence and judgment. In 
those years the character is said to be in embryo, and theologians, 
in using the phrase, " reaching years of religious understanding," 
mean that in early years the religious capacities undergo develop- 
ment coinciden tally with those of the body. 

{b) In Women. — If we examine the metaphysical characteris- 


tics of women, we observe two classes of traits — namely, those 
which are also found in men, and those which are absent or but 
weakly developed in men. Those of the first class are very 
similar in essential nature to those which men exhibit at an early 
stage of development. This may be in some way related to the 
fact that physical maturity occurs earlier in women. 

The gentler sex is characterized by a greater impressibility, 
often seen in the influence exercised by a stronger character, as 
well as by music, color, or spectacle generally ; warmth of emo- 
tion, submission to its influence rather than that of logic ; ti- 
midity and irregularity of action in the outer world. All these 
qualities belong to the male sex, as a general rule, at some period 
of life, though different individuals lose them at very various 
periods. Ruggedness and sternness may rarely be developed in 
infancy, yet at some still prior time they certainly do not exist in 

Probably most men can recollect some early period of their 
lives when the emotional nature predominated — a time when 
emotion at the sight of suffering was more easily stirred than in 
maturer years. I do not now allude to the benevolence inspired, 
kept alive, or developed by the influence of the Christian religion 
on the heart, but rather to that which belongs to the natural 
man. Perhaps all men can recall a period of youth when they 
were hero-worshipers — when they felt the need of a stronger arm, 
and loved to look up to the powerful friend who could sympathize 
with and aid them. This is the " woman stage" of character : in 
a large number of cases it is early passed ; in some it lasts longer ; 
while in a very few men it persists through life. Severe discipline 
and labor are unfavorable to its persistence. Luxury preserves its 
bad qualities without its good, while Christianity preserves its 
good elements without its bad. 

It is not designed to say that woman in her emotional nature 
does not differ from the undeveloped man. On tlie contrary, 
though she does not differ in kind, she differs greatly in degree, 
for her qualities grow with her growth, and exceed in potuer many 
fold those exhibited by her companion at the original point of 
departure. Hence, since it might be said that man is the unde- 
veloped woman, a word of explanation will be useful. Embryonic 
types abound in the fields of nature, but they are not therefore 
immature in the usual sense. Maintaining the lower essential 
quality, they yet exhibit the usual results of growth in individual 


characters ; that is, increase of strength, powers of support and 
protection, size and beauty. In order to maintain tliat the mas- 
culine character coincides with that of the undeveloped woman, 
it would be necessary to show that the latter during her infancy 
possesses the male characters predominating — tliat is, unimpressi- 
bility, judgment, physical courage, and the like. 

If we look at the second class of female characters — namely, 
those which are imperfectly developed or absent in men, and in 
respect to which man may be called undeveloped woman — we 
note three prominent points : facility in language, tact or finesse, 
and the love of children. The first two appear to me to be alto- 
gether developed results of "impressibility," already considered 
as an indication of immaturity. Imagination is also a quality of 
impressibility, and, associated with finesse, is aj^t to degenerate 
into duplicity and untruthfulness — a peculiarity more natural to 
women than men. 

The third quality is different. It generally appears at a very 
early period of life. Who does not know how soon the little girl 
selects the doll, and the boy the toy-horse or machine ? Here 
man truly never gets beyond undeveloped woman. Nevertheless, 
''impressibility" seems to have a great deal to do with this 
quality also. 

Thus the metaphysical relation of the sexes would appear to 
be one of inexact pai'allelism, as defined in Section I. That the 
physical relation is a remote one of the same kind, several charac- 
ters seem to point out. The case of the vocal organs will suffice. 
Their structure is identical in both sexes in early youth, and both 
produce nearly similar sounds. They remain in this condition in 
the woman, while they undergo a metamorphosis and change both 
in structure and vocal power in the man. In the same way, in 
many of the lower creation, the females possess a majority of em- 
bryonic features, though not invariably. A common example is 
to be found in the plumage of birds, where the females and young 
males are often undistinguishable.* But there are a few points in 

* Mcehan states that the upper limbs and strong; laterals in Coniferas and other 
trees produce female flowers and cones, and the lower and more interior branches 
the male flowers. He calls the former condition one of greater " vigor," and the 
latter one of " weakness," and argues that the vigorous condition of growth pro- 
duces females, and the weaker males. What he points out, however, is in harmony 
with the position here maintained — namely, that the female characters include more 
of those which are embryonic in the males than the male characters include of those 


the physical structure of man also in which the male condition is 
the immature one. In regard to structure, the point at which 
the relation between the sexes is that of exact parallelism, or 
where the mature condition of the one sex accords with the unde- 
veloped condition of the other, is when reproduction is no longer 
accomplished by budding or gemmation, but requires distinct 
organs. Metaphysically, this relation is to be found where dis- 
tinct individuality of the sexes first appears ; that is, where we 
pass from the hermaphrodite to the bisexual condition. 

But let us put the whole interpretation on this partial unde- 
velopment of woman. 

The types or conditions of organic life which have been the 
most prominent in the world's history — the Ganoids of the first, 
the Dinosaurs of the second, and the Mammoths of the third 
period — have generally died with their day. The line of succes- 
sion has not been from them. The law of anatomy and paleon- 
tology is, that we must seek the point of departure of the tyjDe 
which is to predominate in the future, at lower stages on the line, 
in less decided forms, or in what, in scientific parlance, are called 
generalized tyjjes. In the same way, though the adults of the 
tailless apes are in a physical sense more highly developed than 
their young, yet the latter far more closely resemble the human 
species in their large facial angle and shortened jaws. 

How much significance, then, is added to the law uttered by 
Christ ! — "Except ye become as little children, ye can not enter 
the kingdom of heaven." Submission of will, loving trust, con- 
fiding faith — these belong to the child : how strange they appear 
to the executing, commanding, reasoning man ! Are they so 
strange to the woman ? AVe all know the answer. Woman is 
nearer to tlie point of departure of that«development which out- 
lives time and peoples heaven ; and if man would find it, he must 
retrace his steps, regain something he lost in youth, and join to 

which are embryonic in the female : the female flowers are the product of the 
younger and more growing portions of the tree — that is, those last produced (the 
upper limbs and new branches) — while the male flowers are produced by the older 
or more mature portions — that is, lower limbs or more axial regions. Further, we 
are not accustomed to regard the condition of rapid growth as that of great vigor 
in animals, but rather ascribe that quality to maturity, after such growth has 

Meehan's observations coincide with those of Thury and others on the origin 
of sexes in animals and plants, which it appears to me admit of a similar explana- 



the powers and energies of his character the submission, love and 
faith which the new birth alone can give. 

Thus the summing up of the metaphysical qualities of woman 
would be thus expressed : In the emotional world, man's superior ; 
in the moral world, his equal ; in the laboring world, his inferior. 

There are, however, vast differences in women in respect to 
the number of masculine traits they may have assumed before be- 
ing determined into their own special development. Woman also, 
under the influence of necessity, in later years of life, may add 
more or less to those qualities in her which are fully developed in 
the man. 

The relation of these facts to the principles stated as the two 
opposing laws of development is, it appears to me, to be explained 
thus : First, that woman's most inherent peculiarities are not the 
result of the external circumstances with which she has been 
placed in contact, as the conflict theory would indicate. Such 
circumstances are said to be her involuntary subserviency to the 
physically more powerful man, and the effect of a compulsory 
mode of life in preventing her from attaining a position of equali- 
ty in the activities of the world. Second, that they are the result 
of the different distributions of qualities as already indicated by 
the harmonic theory of development ; that is, of the unequal posses- 
sion of features which belong to different periods in the develop- 
mental succession of the highest. There is then another beauti- 
ful harmony which will ever remain, let the development of each 
sex be extended as far as it may. 

(c) In Men. — If we look at the male sex, we shall find various 
exceptional approximations to the female in mental constitution. 
Further, there can be little doubt that in the Indo-European race 
maturity in some respects appears earlier in tropical than in 
northern regions ; and though subject to many exceptions, this is 
sufficiently general to be looked upon as a rule. Accordingly, we 
find in that race — at least in the warmer regions of Europe and 
America — a larger proportion of certain qualities which are more 
universal in women ; as greater activity of the emotional nature 
when compared with the Judgment ; an impressibility of the nerv- 
ous center, which, cceteris paribus, appreciates quickly the har- 
monies of sound, form, and color ; answers most quickly to the 
friendly greeting or the hostile menace ; is more careless of conse- 
quences in the material expression of generosity or hatred, and 
more indifferent to truth under the influence of personal relations. 


The movements of the body and expressions of the countenance 
answer to the temperament. More of grace and elegance in the 
bearing marks the Greek, the Italian, and the Creole, than the 
German, the Englishman, or the Green Mountain man. More of 
vivacity and fire, for better or for worse, is displayed in the coun- 

Perhaps the more northern type left all that behind in its 
youth. The rugged, angular character which appreciates force 
better than harmony, the strong intellect which delights in fore- 
thought and calculation, the less impressibility, reaching stolidity 
in the uneducated, are its well-known traits. If there be in such 
a character less generosity and but little chivalry, there is persist- 
ency and unwavering fidelity, not readily obscured by the light- 
ning of passion or the surmises of an active imagination. 

All these peculiarities appear to result, ^rs^, from different de- 
grees of quickness and depth in appreciating impressions from 
without ; and, second, from differing degrees of attention to the 
intelligent judgment in consequent action. (I leave conscience 
out, as not belonging to the category of inherited qualities.) 

The above observations have been confined to the Indo-Euro- 
pean race. It may be objected to the theory that savagery means 
immaturity in the senses above described, as dependent largely on 
''impressibility," while savages in general display the least "im- 
pressibility," as that word is generally understood. * This can not 
be asserted of the Africans, who, so far as we know them, possess 
this peculiarity in a high degree. Moreover, it must be remem- 
bered that the state of indifference which precedes that of impress- 
ibility in the individual may characterize many savages ; while 
their varied peculiarities may be largely accounted for by recol- 
lecting that many combinations of different species of emotion 
and kinds of intelligence go to make up the complete result in 
each case. 

{d) Conclusions. — Three types of religion may be selected 
from the developmental conditions of man : first, an absence of 
sensibility (early infancy) : second, an emotional stage more pro- 
ductive of faith than of works ; thirdly, an intellectual type, more 
favorable to works than faith. Though in regard to responsibility 
these states may be equal, there is absolutely no gain to laboring 
humanity from the first type, and a serious loss in actual results 
from the second, taken alone, as compared with the third. 

These, then, are the physical vehicles of religion — if the phrase 


may be allowed — which give character and tone to the deeper 
spiritual life, as the color of the transparent vessel is communi- 
cated to the light which radiates from within. 

But if evolution has taken place, there is evidently a provision 
for the progress from the lower to the higher states, either in the 
education of circumstances (''conflict ") or in the power of an in- 
terior spiritual influence (" harmony "), or both. 

p. Evidence derived from History. 

We trace the develojoment of Morality in — first, the family, or 
social order ; second, the civil order, or government. 

Whatever may have been the extent of moral ignorance before 
the Deluge, it does not appear that the earth was yet prepared for 
the permanent habitation of the human race. All nations preserve 
traditions of the drowning of the early peoples by floods, such as 
have occurred frequently during geologic time. At the close of 
each period of dry land, a period of submergence has set in, and 
the depression of the level of the earth, and consequent overflow 
by the sea, has caused the death and subsequent preservation of 
the remains of the favina and flora living upon it, while the eleva- 
tion of the same has produced that interruption in the process of 
deposit in the same region which marks the intervals between ge- 
ologic periods. Changes in these respects do not occur to any very 
material extent at the present time in the regions inhabited by the 
most highly developed portions of the human race ; and as the 
last which occurred seems to have been expressly designed for the 
preparation of the earth's surface for the occupation of organized 
human society, it may be doubted whether many such changes are 
to be looked for in the future. The last great flooding was that 
which stratified the drift materials of the north, and carried the 
finer portions far over the south, determining the minor topogra- 
phy of the surface and supplying it with soils. 

The existence of floods which drowned many races of men may 
be considered as established. The men destroyed by the one re- 
corded by Moses are described by him as exceedingly wicked, so 
that "the earth was filled with violence." In his eyes the Flood 
was designed for their extermination. 

That their condition was evil must be fully believed if they 
were condemned by the executive of the Jewish law. This law, it 
will be remembered, permitted polygamy, slavery, revenge, ag- 
gressive war. The Jews were expected to rob their neighbors, the 


Egyptians, of jewels, and tliey were allowed '' an eye for an eye 
and a tooth for a tooth." They were expected to butcher other 
nations, with their women and children, their flocks and their 
herds. If we look at the lives of men recorded in the Old Testa- 
ment as examples of distinguished excellence, we find that their 
standard, however superior to that of the peoj)le around them, 
would ill accord with the morality of the present day. They were 
all polygamists, slaveholders, and warriors. Abraham treated Ha- 
gar and Ishmael with inhumanity. Jacob, with his mother's aid, 
deceived Isaac, and received thereby a blessing which extended to 
the whole Jewish nation. David, a man whom Paul tells us the 
Lord found to be after his own heart, slew the messenger who 
brought tidings of the death of Saul, and committed other acts 
which would stain the reputation of a Christian beyond redemp- 
tion. It is scarcely necessary to turn to other nations if this be 
true of the chosen men of a chosen people. History, indeed, pre- 
sents us with no people prior to, or contemporary with, the Jews 
who were not morally their inferiors.* 

If we turn to more modern periods, an examination of the mo- 
rality of Greece and Eome reveals a curious intermixture of lower 
and higher moral conditions. While each of these nations joro- 
duced excellent moralists, the influence of their teachings was not 
sufficient to elevate the masses above what would now be regarded 
as a very low standard. The popularity of those scenes of cruelty, 
the gladiatorial shows and the combats with wild beasts, sufficiently 
attests this. The Roman virtue of patriotism, while productive 
of many noble deeds, is in itself far from being a disinterested 
one, but partakes rather of the nature of partisanship and selfish- 
ness. If the Greeks were superior to the Romans in humanity, 
they were apparently their inferiors in the social virtues, and were 
much below the standard of Christian nations in both respects. 

Ancient history points to a state of chronic war, in which the 
social relations were in confusion, and the development of the 
useful arts was almost impossible. Savage races, which continue 
to this day in a similar moral condition, are, we may easily be- 
lieve, most unhappy. They are generally divided into tribes, 
which are mutually hostile, or friendly only with the view of in- 
juring some other tribe. Might is their law, and robbery, rapine, 

* The evidence on this point being very imperfect, judgment may be properly 
suspended. (Ed. 1886.) 


and murder express their mutual relations. This is the history of 
the lowest grade of barbarism, and the history of primeval man so 
far as it has come down to us in sacred and profane records. Man 
as a species first appears in history as a sinful being. Then a race 
maintaining a contest with the prevailing corruption and exhibit- 
ing a higher moral idea is presented to us in Jewish history. Fi- 
nally, early Christian society exhibits a greatly superior condition 
of things. In it polygamy scarcely existed, and slavery and war 
were condemned. But progress did not end here, for our Lord 
said, "I have yet many things to say unto you, but ye can not 
bear them now. Howbeit, when he, the spirit of truth, is come, 
he will guide you into all truth." 

The progress revealed to us by history is truly great, and if a 
similar difference existed between the first of the human species 
and the first of whose condition we have information, we can con- 
ceive how low the origin must have been. History begins with a 
considerable progress in civilization, and from this we must infer 
a long preceding period of human existence, such as a gradual 
evolution would require. 

7. Rationale of Moral Development. 

I. Of the Species. — Let us now look at the moral condition of 
the infant man of the present time. We know his small account- 
ability, his trust, his innocence. We know that he is free from 
the law that when he "would do good, evil is present with him," 
for good and evil are alike unknown. We know that until growth 
has progressed to a certain degree he fully deserves the praise pro- 
nounced by our Saviour, that ''of such is the kingdom of heaven." 
Growth, however, generally sees a change. We know that the 
buddings of evil appear but too soon ; the lapse of a few months 
sees exhibitions of anger, disobedience, malice, falsehood, and 
their attendants — the fruit of a corruption within not manifested 

In early youth it may be said that moral susceptibility is often 
in inverse ratio to physical vigor. But with growth the more 
physically vigorous are often sooner taught the lessons of life, for 
their energy brings them into earlier conflict with the antagonisms 
and contradictions of the world. Here is a beautiful example of 
the benevolent principle of compensation. 

1. Innocence and the Fall. — If physical evolution be a reality, 
we have reason to believe that the infantile stage of human mor- 


als, as well as of human intellect, was much prolonged in the his- 
tory of our first parents. This constitutes the period of human 
purity, when we are told by Moses that the first pair dwelt in 
Eden. But the growth to maturity saw the development of all 
the qualities inherited from the irresponsible denizen of the forest. 
Man inherits from his predecessors in the creation the buddings of 
reason — he inherits passions, propensities, and appetites. His cor- 
ruption is that of his animal progenitors, and his sin is the low 
and bestial instinct of the brute creation. Thus only is the origin 
of sin made clear — a problem which the pride of man would have 
explained in any other way had it been possible. 

But how startling the exhibition of evil by this new being as 
compared with the scenes of the countless ages already past ! Then 
the right of the strongest was God's law, and rapine and destruc- 
tion were the history of life. But into man had been "breathed 
the breath of life," and he had " become a living soul." The law 
of right, the Divine Spirit, was planted within him, and the laws 
of the beast were in antagonism to that law. The natural devel- 
opment of his inherited qualities necessarily brought him into col- 
lision with that higher standard planted within him, and that war 
was commenced which shall never cease "till he hath put all 
things under his feet." The first act of mane's disobedience con- 
stituted the Fall, and with it would come the first intellectual 
"knowledge of good and of evil" — an apprehension up to that 
time derived exclusively from the divinity within, or conscience.* 

2. Free Agency. — Heretofore development had been that of 
physical types, but the Lord had rested on the seventh day, for 
man closed the line of the physical creation. Now a new develop- 
ment was to begin — the develoi^ment of mind, of morality, and of 

On the previous days of Creation all had progressed in accord- 
ance with inevitable law apart from its objects. Now, two lines 

* In our present translation of Genesis, the Fall is ascribed to the influence of 
Satan assuming the form of the serpent, and this animal was cursed in consequence, 
and compelled to assume a prone position. This rendering may well be revised, 
since serpents, prone like others, existed in both America and Europe during the 
Eocene epoch, five times as great a period before Adam as has elapsed since his day. 
Clark states, with great probability, that "serpent" should be translated monkey or 
ape — a conclusion, it will be observed, exactly comciding with our inductions on the 
basis of evolution. The instigation to evil by an ape merely states inheritance in 
another form, flis curse, then, refers to the retention of the horizontal position re- 
tained by all other quadrumana, as we find it at the present day. 


of development were at the disposal of this being, between which 
his free will was to choose, Did he choose the courses dictated 
by the spirit of the brute, he was to be subject to the old law of 
the brute creation — the right of the strongest and spiritual death. 
Did he choose the guidance of the Divine Guest in his heart, he 
became subject to the laws vi^hich are to guide — 1, the human spe- 
cies to an ultimate perfection, so far as consistent with this world ; 
and, 2, the individual man to a higher life, where a new existence 
awaits him as a spiritual being, freed from the laws of terrestrial 

The charge brought against the theory of development, that 
it implies a necessary progress of man to all perfection without his 
co-operation — or 7iecessitarianism, as it is called — is unfounded. 

The free will of man remains the source alike of his progress 
and his relapse. But the choice once made, the laws of spiritual 
development are apparently as inevitable as those of matter. Thus 
men whose religious capacities are increased by attention to the 
Divine Monitor within are in the advance of progress — progress 
coinciding with that which in material things is called the har- 
monic. On the other hand, those whose motives are of the lower 
origin fall under the working of the law of conflict. 

The lesson derivable from the preceding considerations would 
seem to be ''necessitarian " as respects the whole human race, con- 
sidered by itself; and I believe it is to be truly so interpreted. 
That is, the Creator of all things has set agencies at work which 
will slowly develop a perfect humanity out of his lower creation, 
and nothing can thwart the process or alter the result. " My word 
shall not return unto me void, but it shall accomplish that which 
I please, and it shall prosper in the thing whereto I sent it." This 
is our great encouragement, our noblest hope — second only to that 
which looks to a blessed inheritance in another world. It is this 
thought that should inspire the farmer, who, as he toils, wonders, 
" Why all this labor ? The Good Father could have made me like 
the lilies, who, though they toil not, neither spin, are yet clothed 
in glory ; and why should I, a nobler being, be subject to the dust 
and the sweat of labor ? " This thought should enlighten every 
artisan of the thousands that people the factories and guide their 
whirling machinery in our modern cities. Every revolution of a 
wheel is moving the car of progress, and the timed stroke of the 
crank and the rhythmic throw of the shuttle are but the music 
the spheres have sung since time began. A new significance then 


appears in the prayer of David : " Let the beauty of the Lord our 
God be upon us, and establish thou the work of our hands upon 
us : the work of our hands, Lord, establish thou it." But, be- 
ware of the catastrophe, for "He will sit as a refiner"; "The 
wheat shall be gathered into barns, but the chaff shall be burned 
with unquenchable fire." If this be true, let us look for — 

3. The Extinction of Evil. — How is necessitarianism to be 
reconciled with free will ? It appears to me, thus : "When a being 
whose safety depends on the perfection of a system of laws aban- 
dons the system by which he lives, he becomes subject to that 
lower grade of laws which govern lower intelligences. Man, falling 
from the laws of right, comes under the dominion of the laws of 
brute force ; as said our Saviour, " Salt is good, but if the salt 
have lost his savor, it is thenceforth good for nothing but to be 
cast forth and trodden under foot of men." 

In estimating the practical results to man of the actions 
prompted by the lower portion of our nature, it is only necessary 
to carry out to its full development each of those animal qualities 
which may in certain states of society be restrained by the social 
system. In human history those qualities have repeatedly had 
this development, and the battle of progress is fought to decide 
whether they shall overthrow the system that restrains them, or 
be overthrown by it. 

Entire obedience to the lower instincts of our nature insures 
destruction to the weaker, and generally to the stronger also. A 
most marked case of this kind is seen where the developed vices of 
civilization are introduced among a savage peoj)le — as, for exam- 
ple, the North American Indians. These seem in consequence to 
be hastening to extinction. 

But a system or a circuit of existence has been allotted to the 
civil associations of the animal species man, independently of his 
moral development. It may be briefly stated thus : Eaces begin 
as poor offshoots or emigrants from a parent stock. The law of 
labor develops their powers, and increases their wealth and num- 
bers. These will be diminished by their various vices ; but, on 
the whole, in proportion as the intellectual and economical ele- 
ments prevail, wealth will increase — that is, they accumulate 
power. When this has been accomplished, and before activity 
has slackened its speed, the nation has reached the culminating 
point, and then it enters upon the period of decline. The re- 
straints imposed by economy and active occupation being removed, 


the beastly traits find in accumulated power only increased means 
of gratification, and industry and prosperity sink together. Power 
is squandered, little is accumulated, and the nation goes down to 
its extinction amid scenes of internal strife and vice. Its cycle is 
soon fulfilled, and other nations, fresh from scenes of labor, as- 
sault it, absorb its fragments, and it dies. This has been the 
world's history, and it remains to be seen whether the virtues of 
the nations now existing will be sufficient to save them from a 
like fate. 

Thus the history of the animal man in nations is wonderfully 
like that of the type or families of the animal and vegetable king- 
doms during geologic ages. They rise, they increase, and reach a 
period of multiplication and power. The force allotted to them 
becoming exhausted, they diminish and sink and die. 

II. Of the Individual. — In discussing physical development, 
we are as yet compelled to restrict ourselves to the evidence of its 
existence and some laws observed in the operation of its causative 
force. What that force is, or what are its primary laws, we know 

So, in the progress of moral development, we endeavor to prove 
its existence and the mode of its operation, but why that mode 
should exist, rather than some other mode, we can not explain. 

The moral progress of the species depends, of course, on the 
moral progress of the individuals embraced in it. Eeligion is the 
sum of those influences which determine the motives of men's 
actions into harmony with the divine perfection and the divine 

Obedience to these influences constitutes the practice of religion, 
while the statement of the growth and operation of these influences 
constitutes the theory of religion, or doctrine. 

The Divine Spirit planted in man shows him that which is in 
harmony with the Divine Mind, and it remains for his free will to 
conform to it or reject it. This harmony is man's highest ideal of 
happiness, and in seeking it, as well as in desiring to flee from 
dissonance or pain, he but obeys the disposition common to all 
conscious beings. If, however, he attempts to conform to it, he 
will find the law of evil present, and frequently obtaining the 
mastery. If now he be in any degree observing, he will find that 
the laws of morality and right are the only ones by which human 
society exists in a condition superior to that of the lower animals, 
and in which the capacities of man for happiness can approach a 


state of satisfaction. He may be then said to be "awakened" tc 
the importance of religion. If he carry on the struggle to attain 
to the high goal presented to his spiritual vision, he will be deejily 
grieved and humbled at his failures ; then he is said to be "con- 
victed." Under these circumstances the necessity of a deliverance 
becomes clear, and is willingly accepted in the only way in which 
it has pleased the Author of all to present it, which has been epito- 
mized by Paul as " the washing of regeneration and renewal of the 
Holy Spirit through Jesus Christ." Thus a life of advanced and 
ever-advancing moral excellence becomes possible, and the man 
makes nearer approaches to the "image of God." 

Thus is opened a new era in spiritual development, which we 
are led to believe leads to an ultimate condition in which the na- 
ture inherited from our origin is entirely overcome, and an exist- 
ence of moral perfection entered on. Thus, in the book of Mark 
the simile occurs : "Eirst the blade, then the ear, after that the 
full corn in the ear" ; and Solomon says that the development of 
righteousness "shines more and more unto the jjerfect day." 

8. Summary. 

If it be true that general development in morality proceeds in 
spite of the original predominance of evil in the world, through 
the self-destructive nature of the latter, it is only necessary to ex- 
amine the reasons why the excellence of the good may have been 
subject also to progress, and how the remainder of the race may 
have been influenced thereby. 

The development of morality is then probably to be understood 
in the following sense : Since the Divine Spirit, as the prime force 
in human progress, can not in itself be supposed to have been in 
any way under the influence of natural laws, its capacities were no 
doubt as eternal and unerring in the first man as in the last. But 
the facts and probabilities discussed above point to development 
of religious sensibility, or capacity to appreciate moral good, or to 
receive impressions from the source of good. 

The evidence of this is supposed to be seen in— first, improve- 
ment in man's views of his duty to his neighbor ; and, second, tlie 
substitution of spiritual for symbolic religions : in other words, 
improvement in the capacity for receiving spiritual impressions. 

What the primary cause of this supposed development of re- 
ligious sensibility may have been, is a question we reverently leave 
untouched. That it is intimately connected in some way with, 


and in part dependent on, the evolution of tlie intelligence, appears 
very probable ; for this evolution is seen — Urst, in a better under- 
standing of the consequences of action, and of good and of evil in 
many things ; and, second, in the production of means for the 
spread of the special instrumentalities of good. The following 
may be enumerated as such instrumentalities : 

1. Furnishing literary means of record and distribution of the 
truths of religion, morality, and science. 

2. Creating and increasing modes of transportation of teachers 
and literary means of disseminating truth. 

3. Facilitating the migration and the spread of nations holding 
the highest position in the scale of morality. 

4. The increase of wealth, which multiplies the extent of the 
preceding means. 

And now, let no man attemjat to set bounds to this dcA^elop- 
ment. Let no man say even that morality accomplished is all that 
is required of mankind, since that is not necessarily the evidence 
of a spiritual development. If a man possess the capacity for prog- 
ress beyond the condition in which he finds himself, in refusing to 
enter upon it he declines to conform to the divine law. For 
'•from those to whom little is given, little is required, but from 
those to whom much is given, much shall be required." 



Chapter I — Ok the Law of Acoelebation and Eetaedation. — Nature 
of law of Natural Selection. Two kinds of evidence. Illustration. 
Examples from Cervidae, Helicidse, insects and men. 

Chapter II — The Law of Repetitive Addition. — Segment and cell- 
repetition. Illustration from limbs and vertebral column. A, On seg- 
ment addition ; definitions. On repetition in bilateral and antero-pos- 
terior symmetry ; in structure of compound teeth ; in segments of 
Articulata; limbs of Reptilia ; brain of lamprey. B, On cell-repetition ; 
simple segment a repetition of cells; simple diverticulum the same. 
The cell theory ; the nucleated cell. C, Synthesis of repetition. From 
unicellular to multicellular animals; simple repetition to compound 
repetition; Actinia, Lepidosiren, Ichthyosaurus, Plesiosaurns, Tcenia ; 
the heart; mammalian teeth. D, On growth-force; relation to other 
forces; definition. E, Direction of repetition, its location, centrifugal 
and longitudinal; movements longitudinal. Inheritance; its relation 
to growth-force. 

Chapter III — The Law of Use and Effort. — Points to be investigated. 
A, On the location of growth-force. Relation of effort to use. Rudi- 
mental characters. Examples of growth under influence of physical 
laws; Examples of colors under influence of light. Use and disuse of 
gills. Rattlesnake ; horned animals. Teeth of ruminants. B, Change 
in amount of growth-force. Local increase of growth-force. Convo- 
luted structures; -brain, teeth, cotyledons. Absolute loss of growth- 
force. Teeth and toes of Ruminants ; incisors of Rodents. 

Chapter IV — On Grade Influence. — A, On the nature of Grade In- 
fluence or Bathmism. Definitions. In plants; in animals. Increase 
in time of Bathmism and growth-force. Vital forces and vital in- 
fluences. Thought-force. Origin of Bathmism in time. B, Physio- 
logical origin of Bathmism. Function of nervous system in force- 
conversion. Automatic and habitual movements. Effect on nervous 

Chapter V — Intelligent Selection. — Development of intelligence. Stim- 
uli to use. Compulsion, Choice; Bees, Food, Rattlesnake; Change of 
color; Mimetic analogy ; Examples. Development of character. 

In the present state of biological science, essays like the pres- 
ent can only be tentative in so far as they treat of the laws of evo- 


lution. Nevertheless the present time is pre-eminently one of 
generalization in this field, and properly so. Facts have been ac- 
cumulating for a long period, and are now sufficiently numerous 
to yield important results, under proper classification and induc- 
tion. Darwin led the way in this work, and the development 
hypothesis is regarded as demonstrated by most biologists. The 
discussion of the laws of its progress involves a multitude of 
subordinate hypotheses. In the following essay, these are ar- 
ranged under five prominent heads, viz. : 1. The law of Accelera- 
tion and Eetardation; 2. The law of Kepetitive Addition; 3. The 
law of Use and Effort ; 4. The law of Grade Influence ; 5. The 
law of Intelligent Selection. Of these, the first and second are 
regarded by the author as demonstrated, the third and fourth as 
only reduced to a partial demonstration, while the fifth is a con- 
sequence of the third, and stands or falls with it. 

The discussion of this subject divides itself into two parts, 
viz. : a consideration of the proof that evolution of organic types 
or descent with modification has taken place ; and, secondly, the 
investigation of the laws in accordance with which this develop- 
ment has progressed. As the latter involves the use of the evi- 
dence included in the former, I will not devote a special chapter 
to the proof for evolution. 

The influences and forces which have operated to produce the 
type structures of the animal kingdom have been plainly of two 
kinds: 1. Originative; '^.Directive. The prime importance of 
the former is obvious ; that the latter is only secondary in the 
order of time or succession is evident from the fact that it con- 
trols the preservation or destruction of the results or creations of 
the first, and thus furnishes the bases of the (exhibitions of the 
originative forces in the production of the successive generations 
of living beings. 

Wallace and Darwin have propounded as the cause of modifi- 
cation in descent their law of natural selection. This law has 
been epitomized by Spencer as the ''survival of the fittest." 
This neat expression no doubt covers the case, but it leaves the 
origin of the fittest entirely untouched. Darwin assumes a 
"tendency to variation" in nature, and it is plainly necessary to 
do this, in order that materials for the exercise of a selection 
should exist. Darwin and Wallace's law is, then, only restrictive, 
directive, conservative, or destructive of something already created. 
I propose then to seek for the originative laws by which these sub- 


jects are furnished — in other words, for the causes of the origin of 
the fittest. 

It has seemed to the author so clear from the first as to re- 
quire no demonstration, that natural selection includes no ac- 
tively progressive principle whatever ; that it must first wait for 
the development of variation, and then, after securing the survival 
of the best, wait again for the best to project its own variations 
for selection. In the question as to whether the latter are any 
better or worse than the characters of the parent, natural selec- 
tion m no wise concerns itself. 


There are two modes of demonstration of evolution, both de- 
pending on direct observation. One of these has been success- 
fully presented by Darwin. He has observed the origin of 
varieties in animals and plants, either in the domesticated or 
wild states, and has shown, what had been known to many, the 
lack of distinction in the grades of difference which separate 
varieties and species. But he has also pointed out that species 
(such, so far, as distinctness goes) have been derived from other 
species among domesticated animals, and he infers by induction 
that other species, whose origin has not been observed, have also 
descended from common parents. So far I believe his induction 
to be justified ; but when from this basis evolution of divisions 
defined by important structural characters, as genera, orders, 
classes, etc., is inferred, I believe that we do not know enough of 
the uniformity of Nature's processes in the premises to enable us 
to regard this kind of proof as conclusive. 

I therefore appeal to another mode of proving it, and one 
which covers the case of all the more really structural features of 
animals and plants. 

It is well known that in both kingdoms, in a general way, 
the young stages of the more perfect types are represented or imi- 
tated with more or less exactitude by the adults of inferior ones. 
But a true identity of these adults with the various stages of the 
higher has, comparatively, rarely been observed. Let such a case 
be supposed. 

In A we have four species whose growth attains a given 
point, a certain number of stages having been passed prior to its 
termination or maturity. In B we have another series of four 
(the number a matter of no importance), Avhich, during the period 



Fig. 7. 

of growth, can not be distinguished by any common, i. e., generic 
character, from the individuals of group A, but whose growth 
has only attained to a point short of that reached by those of 
group A at maturity. Here we have a parallelism, but no true 
evidence of descent. But if we now find a set of individuals be- 
longing to one species, or, still better, the individuals of a single 
brood, and therefore held to have had a common origin or parent- 
age, which present differences among themselves of the character 

, in question, we have gained a point. 

' =:: A We know in this case that the individ- 
uals, a, have attained to the complete- 
ness of character presented by group A, 
h while others, b, of the same parentage 
T> have only attained to the structure of 
those of group B. It is perfectly obvious 
that the individuals of the first part of 
the family have grown further, and, therefore, in one sense faster, 
than those of group b. If the parents were like the individuals 
of the more completely grown, then the offspring which did not 
attain that completeness may be said to have been retarded in 
their development. If, on the other hand, the parents were like 
those less fully grown, then the offspring which have added some- 
thing have been accelerated in their development. 

I claim that a consideration of the uniformity of Nature's 
processes, or inductive reasoning, requires me (however it may 
affect the minds of others) to believe that the groups of species, 
whose individuals I have never found to vary, but which differ in 
the same point as those in which I have observed the above varia- 
tions, are also derived from common parents, and the more ad- 
vanced have been accelerated or the less advanced retarded, as the 
case may have been with regard to the parents. 

This is not an imaginary case, but a true representation of 
many which have come under observation. The developmental 
resemblances mentioned are universal in the animal, and probably 
in the vegetable kingdoms, approaching the exactitude above de- 
picted in proportion to the near structural similarity of the spe- 
cies considered. 

Example 1. — It is well known that the CervidcB of the Old 
World develop a basal snag of the antler (see Cuvier, " Ossemens 
Fossiles," and Gray, " Cat. British Museum ") at the third year ; a 
majority of those of the New World (genera Subulo, Cariacus) 


never develop it except in abnormal cases in the most vigorous 
maturity of the most northern Cariacus {O. virginianus), while 
the South American Subulo retains to adult age the simple horn 
or spike of the second year of all CervidcB. 

Among the higher Cervidm, Eusa and Axis never assume char- 
acters beyond an equivalent of the fourth year of Cervus. In 
Dama the characters are, on the other hand, assumed more rapidly 
than in Cervus, its third year corresponding to the fourth of the 
latter, and the development in after years of a broad plate of bone, 
with points being substituted for the addition of the correspond- 
ing snags, thus commencing another series which terminates in 
the great fossil elk, Megacerus. 

Eeturning to the American deer, we have Blastocerus, whose 
antlers are identical with the fourth year of Cariacus. Corre- 
sponding with the Dama-Megacerus type of the Old World, we 
have the moose (Alces) developing the same palmate horn on the 
basis of Cariacus (i. e., without eye-snag). 

Example 2. — I select the following series, embracing the ma- 
jority of the genera of the North American Helicidse.* 

1. Turns of spire very few ; wide umbilicus ; shell thin, with thin lips, .^iwne^a. 

2. Turns few, but more ; rest as above Vitrina, 

3. Turns still more numerous ; rest as above Hyalina. 

4. As No. 3, but lip thickened inside Hygromia. 

5. Coiled ; umbilictis closed ; lip thickened inside and out . . Taehea and Pomatia. 

6. Same, with a parietal tooth Mesodon. 

7. Same, with parietal and two interior lip teeth Isognomostoma. 

* * Recommencing at Xo. 4. All with open umbilicus. 

5. As No. 4, but lip thickened in and out Arionta. 

6. Same as No. 5, but with parietal tooth , Polymita. 

1. Same, with both parietal and lip teeth Triodopsis. 

The successional relation of these genera may be represented 
in such a diagram as this : 

Umbilicus open. Umbilicus closed. 

rj * * 

6 * * 

5 « * 

4 * 

3 * 

2 * 

1 * 

* See Tryon, " Terrestrial Mollusca of the United States." Probably other (e. g., 
dental) characters distinguish some of these genera, but the above furnishes the 
history of one set of characters. 


In tlie history of the growth of the genera Isognomostoma and 
Triodopsis, the extreme forms of the two series, it is well known 
that at first the coils of the shell are extremely few, as in Binneya ; 
and that, like it, it is very thin and with a delicately thin edge ; 
that the turns increase successively in number, as in Vitrina and 
Hyalina ; and that, finally, the lip thickens, as in Hygromia. Then 
the umbilicus may close, as in Tachea, or (in Triodopsis) remain 
open, as in Arionta. In either case a tooth is soon added on the 
body-whorl (Polymita, Mesodon), and, finally, the full maturity 
of the shell is seen in the added teeth of the inside of the lip-mar- 
gin. How many of the stages of the genera Triodopsis and Meso- 
don are identical with the genera of the series which represent 
them, I leave to more thorough conchologists, but that some now 
exhibit and all have once presented illustrations of the relation of 
exact parallelism, I can not doubt. 

Example 1, — An abundant race of the American deer, C'aria- 
cus virgitiianus, exists in the Adirondack region of New York, in 
which the development of the antlers never progresses beyond the 
spike stage of the second year. Therefore, some individuals of 
this species belong to Cariacus and some to Subulo.* 

Example 2. — A large part of the individuals of the common 
snail, Mesodon albolahris, never develop the tooth of the body- 
whorl, characteristic of the genus whose definition has to be modi- 
fied to retain them. 

Example 3. — Many individuals of Triodopsis tridentata from 
eastern North Carolina occur without the lip-teeth, characteristic 
of the genus Triodopsis. Hence these specimens, though of com- 
mon origin with others of the species, must be referred to another 

Example 4. — Structural characters are known in many, if not 
all, species which are said to be "inconstant," being present or 
absent indifferentl}^, thus being useless for definition. They may 
be rudimental when present or considerably developed. The pres- 
ence or absence of wings in some species of insects may be cited ; 
also the presence of generic characters in the male sex of many 
Coleoptera and their absence in the females. The characters of 

* Since the above was written the facts as stated have been denied. But the 
author has seen specimens of Cariacus virginiamis and C. macrotis in which the 
horns had assumed the characters of the genus Alces, throwing these individuals 
into that genus. See "American Naturalist," 1883-'84. (Ed. 1886.) 


males, females, workers and soldiers in bees and ants may be added. 
All these facts belong to the same category as those cited among 
deer and mollusks, and have a similar explanation. 

Example 5. — It does not seem to be the law in '* retardation " 
that parallelisms exhibited by the series in its rise to its highest 
point of development should retrace the steps by which it attained 
it, and that "exact parallelisms " should be exhibited in a reversed 
order. Parallelisms, it is true, are exhibited ; but so far as I have 
observed always " inexact," often in a high degree. A marked 
case of retardation occurs in the dental development of a number 
of persons who have come under my observation in the neighbor- 
hood of Philadelphia. It is not very uncommon to find persons 
in whom the third molars in both jaws are incomplete as to number, 
one, two, three, or all, being deficient. It is still more common 
for them to be incompletely covered by the enamel layer, and to 
become in consequence so worthless as to require early removal. I 
am acquainted with two families in which the absence of the ex- 
terior upper incisor on each side is common. In one of these the 
second and third generation have inherited it from the mother's 
side, and it now characterizes many of the children. The signifi- 
cance of this modification will be best understood by examining 
the dental structures of the Quadrumana in general. Commencing 
with the highest family and its abnormal dentition, we have : 

Incisors. Canines. Premolars. Molars. 

rr ■ .J { Abnormal. h \ i I — I 

( formal. fill 

Simiidce III? 

Cebidce I I ^ f 

Lemurid(e f j ^ — g ^ 

Mammalia, Normal f { 4 f 

In this table we see a decline in the number of teeth of the 
higher groups. Thus, the premolars are one less than the normal 
number in the whole order, and they lose one in each Jaw in the 
Old World apes, and man. The molars maintain the normal num- 
ber throughout, but the third in both jaws is in the Simiidce 
reduced by the loss of a fifth or odd tubercle, thus becoming four- 
lobed. In the upper jaw, this is first lost in the Semnopithecus ; 
in the lower, in the next highest genus Cercopithecus. In Homo 
its appearance is "retarded," the interval between that event and 
the protrusion of the second molar — six to ten years — being rela- 
tively greater than in any genus of Quadrumana. Its absence is 


then the result of continued retardation, not of a new and adaptive 
suppression, and is of direct systematic zoological value. 

In the incisors a reduction is also plainly visible, as we pass 
from the most completely furnished mammals to the genus Homo. 
One from the upper jaw is first lost, then, in the Cehidce, one from 
the lower also. The number remains the same through the SimiidcB 
and normal Hominidm, but, in the abnormal cases cited, the process 
of reduction is continued and another incisor from each side disap- 
pears. That this also is truly "retardation" is evident from the 
fact, that the exterior incisor is the last develo^jed, being delayed 
in ordinary growth a year later than those of the inner pair. The 
same retardation is seen in the quadrumane Glieiromys (the aye- 
aye), and the whole order Rodentia. In the latter, the rare i^res- 
ence of the reduced second incisors, as in Lepus, shows a less degree 
of this modification. This retardation is also of systematic impor- 
tance, and, should either of the characters described be constant in 
any of the species of the genus Homo, would at once entitle it to 
new generic rank. The very frequent absence of the posterior 
molars (wisdom teeth) has been recently found to characterize a 
race in India. Should this peculiarity prove constant, this race 
would with propriety be referred to as a new genus of HominidcB, 
as we have many cases of very similar species being referred to 
different genera. It is altogether probable that such will, at some 
future time, be the condition of some race or races of men.* 

I am now disposed to regard the above as the method of produc- 
tion, not only of generic but of all other, including specific char- 
acters. It would appear that, by excessive acceleration or retarda- 
tion, some of the characters of a series may be skipped; but observa- 
tions are not conclusive on this point, since very close examination 
is necessary for the appreciation of very transitory embryonic con- 


The origin of new structures, which distinguish one generation 
from those which have preceded it, I have stated to take place 
under the law of acceleration. As growth (creation) of parts usu- 
ally ceases with maturity, it is entirely plain that the process of 
acceleration is limited to the period of infancy and youth in all 
animals. It is also plain that the question of growth is one of 

* The preceding section is merely an abbreviation, with new illustrations, of the 
propositions brought forward in the writer's " Origin of Genera," 1868, where a con- 
siderable extension of the subject will be found. 


nutrition, or of the construction of organs and tissues out of pro- 

The construction of the animal types may be referred to two 
kinds of increase — the addition of identical segments and the addi- 
tion of identical cells. The first is probaoly to be referred to the 
last, but the laws which give rise to it can not now be explained. 
Certain it is that segmentation is not only produced by addition of 
identical parts, but also by subdivision of a homogeneous part. In 
reducing the vertebrate or most complex animal to its simplest 
expression, we find that all its specialized parts are but modifica- 
tions of the segment, either simply or as sub-segments of compound 
but identical segments. Gegenbaur has pointed out that the most 
complex limb with hand or foot is constructed, first, of a single 
longitudinal series of identical segments, from each of which a 
similar segment diverges, the whole forming parallel series, not only 
in the oblique transverse, but generally in the longitudinal sense. 
Thus, the limb of the Lepidosiren represents the simple type, that 
of the Ichthyosaurus a modification. In the latter, the first seg- 
ment only (femur or humerus) is specialized, the other pieces being 
undistinguishable. In the Plesiosaurian paddle the separate parts 
are distinguished, the ulna and radius well marked, the carpal 
pieces hexagonal, the phalanges defined, etc. 

As regards the whole skeleton, the same position may be safely 
assumed. Though Huxley may reject Owen's theory of the verte- 
brate character of the segments of the brain-case, because they are 
so very different from the segments in other parts of the column, 
the question rests entirely on the definition of a vertebra. If a 
vertebra be a segment of the skeleton, of course the brain-case is 
composed of vertebrae ; if not, then the cranium may be said to be 
formed of ''sclerotomes," or some other name may be used. Cer- 
tain it is, however, that the parts of the segments of the cranium 
may be now more or less completely parallelized or homologized 
with each other, and that, as we descend the scale of vertebrated 
animals, the resemblance of these segments to vertebrae increases, 
and the constituent segments of each become more similar. In the 
types, as Ampliioxus, etc., where the greatest resemblance is seen, 
segmentation of either is incomplete, for they retain the original 
non-osseous basis. Other animals which present cavities or parts 
of a solid support are still more easily reduced to a simple basis of 
segments, arranged either longitudinally (worm) or centrifugally 
(star-fish, etc.). 



a. The succession of construction of parts of a complex, was 
originally a succession of identical repetitions ; and grade influ- 
ence merely determined the number and location of such repeti- 

13. Acceleration signifies addition to the number of those repeti- 
tions during the period preceding maturity, as compared with the 
preceding generation, and retardation signifies a reduction of the 
numbers of such repetitions during the same time. 

y. The successive additions now characterizing the growth of the 
highest animals are not exact repetitions of segments at this time, 
because of influences brought to bear on cell-nutrition during long 
periods. The nature of these influences is made the subject of 
another section. 

In the endeavor to prove these positions, I will produce evi- 
dence, first, that some simpler animals grow according to the prin- 
ciple of modified repetitive addition, and that traces of it are to be 
observed in the most complex ; second, that every addition to 
structure which has resulted in the complexity of the higher ani- 
mals was originally a repetition of a pre-existent structure. 

Detailed explanations of the law of repetitive addition are at- 
tempted in the following pages, under two heads — segment-rei^eti- 
tion, and cell-repetition. 

A. On Segment- Repetition. 

This is everywhere seen in the construction of animals and 
plants. Double bilateral symmetry may serve as one example of 
repetition in growth. 

a. Bilateral symmetry. Anatomists have little difficulty in de- 
termining the bilateral symmetry in most animals — that is, the 
homologies of the parts on opposite sides of the median line. It 
might be almost asserted that it was a necessity of organization ; 
but, when we observe the growth of many plants, we are unde- 
ceived. And though bilateral symmetry in the Coelenterata and 
many Articulata is perfect, yet in higher animals it is more or less 
departed from. In the Vertebrata the Ampliioxus is almost com- 
pletely bilaterally symmetrical. In the fishes, the digestive system 
is the only one which does not conform to it ; while in the birds 
the reproductive system is atrophied on one side. In the ser- 
pents the respiratory and part of the circulatory are similarly 


modified ; and in the Mammalia the digestive and circulatory- 
systems have both become unsymmetrical ; and the cranium, even, 
in the Cetacea. 

If evolution be true, the unsymmetrical forms have descended 
from the symmetrical, and the asymmetry being thus not inherited, 
is the result of laws which have interfered with the original tend- 
ency to bilateral repetition. 

Many cases of bilaterally symmetrical diseases have been enu- 
merated by physiologists, and I will select as an example one which 
has come under my observation. They were those of two boys who 
had had that disease involving the muco-dermal system called vari- 
cella, while the crowns of the successional incisor teeth were still 
inclosed in the mucous capsules of the alveolar walls. The deposit 
of phosphate of lime forming their surfaces was interrupted by the 
disease of the tissue, and the result was a surface pitted, or sculpt- 
ured intaglio fashion. The sculpture of the two incisors of the 
right side was precisely imitated by those of the left in reversed 
order, even in minute details, which were numerous, thus produc- 
ing a result not displeasing to the eye. This has been observed on 
two distinct occasions some years apart. 

Another interesting example of bilaterally symmetrical disease 
is recorded in a paper on " A Case of Universal Hyperostosis, etc.," 
by Drs. Mears, Keen, Allen, and Pepper.* They describe the skele- 
ton of a boy of fourteen which displayed an extraordinarily exos- 
tosed condition, the bones themselves remaining in the condition 
known as osteoporosis. They describe the uniform repetition of 
the abnormal growths of one side on the other in the following 
language (p. 22) : 

" Comparing the two sides externally, not only is there no dif- 
ference in the extent and character of the disease, but there is the 
most remarkable symmetry of the corresponding diseased bones, 
which may be traced even into details. The disease begins and 
ends on both sides at corresponding points, it changes in character 
from simple porosity to the growth of osteophytes at corresponding 
points ; if, on one side, the posterior part of the bone is most dis- 
eased, the same is true of the other side ; if the osteophyte growth 
is continuous or interrupted on one bone (fibula, Fig. 18), it is so 
on the opposite one ; if one is unusually diseased at a tendinous or 
aponeurotic insertion, so is its mate ; if a groove or a variation in 

* Sec "Proceed. Amcr. Philos. Soc," 1870, p. 19. 


color exist on the one side, the same will be found on the other 
side ; even of single marked spicule of bone the same may be said, 
so that a description of one side will answer for both, minute dif- 
ferences being noted as they occur." 

b. Anteroposterior symmetry. 

That this is an absolute law of creation will be less readily ad- 
mitted than in the case of double bilateral symmetry, since the ex- 
ceptions apjoear to be so universal. Nevertheless, I believe it to be 
as much a part of the law of repetitive nutrition as the other. 
The anteroposterior homologies even of the human skeleton have 
been largely demonstrated, bnt, as usual, we must appeal to the 
lower forms for a clear view of it. In the rudimental skeletal axis 
we find such symmetry almost perfect in the Amphioxiis, but in no 
other vertebrate. In limbs we have it clearly indicated in the 
Keptilian order Iclithyopterygia, and in the Piscine order Dipnoi, 
where the anterior and posterior are scarcely or not at all distin- 
guishable. In the scapular and pelvic arches we find it also ap- 
proximated in the first-named orders. 

In the nervous system it also exists approximately in the Am- 
pliioxus. It is not seen in any vertebrate, and in but few other 
animals, in the digestive system, but it appears to exist in some 
lower Articulata in both the resj)iratory and circulatory systems. 

c. As illustrations of exact repetition involving large portions 
of the organism the higher Polyps may be cited, which differ from 
the lower chiefly by the addition of similar septa and similar ten- 
tacles. Examples of repetition of nearly the whole organism may 
be found in many Entozoa, as Tmnia, where the cephalic segment 
only differs from the others, the remainder or proglottides being 
alike. The most entire repetition of structure is seen in Vibrio, 
where the segments are all alike, there being none representing a 

d. As an example in special details of structure, the pelvic arch 
of Ichthyosaurus, when first created, was a repetition of the scapu- 
lar, and the hind limb, of the fore limb. The segments of the 
limbs of the Dipnoi are mere repetitions, the later created of the 
earlier. The special parts of the pes and mantis of Ichthyosaurus 
are simply repetitive efforts of growth-force joined with a dimin- 
ishing amount. The addition of a digit, often distinguishing one 
genus of Salamanders or Saurians from another, is evidence of a 
similar repetitive effort. The low mammal Ornithorhynchus pos- 
sesses but a single tooth in each jaw ; the simple teeth of armadil- 


los and cetaceans, increasing as they have done from a simpler 
commencement, present examples of repetitive acceleration of 

e. Complication of a single element of repetition is accomplished 
apparently by a double repetition. This is best understood by the 
consideration of the transition from simple to complex teeth. In 
the cetaceans this occurs in the Squalodonts ; the cylindric incisors 
are followed by flattened ones, then by others grooved on the fang, 
and then by two-rooted, but never double-crowned teeth. This is 
the result of anteroposterior repetitive acceleration of the simijle 
cylindric dental type of the ordinary toothed cetacean. 

Another mode of dental complication is by lateral repetition. 
Thus, the heel of the sectorial tooth of a Carnivore is supported 
by a fang alongside of the usual posterior support of a premolar, 
and is the result of a repetitive effort of growth-force in a transverse 
direction. More complex teeth, as the tubercular molars, merely 
exhibit an additional lateral repetition, and sometimes additional 
longitudinal ones. As is w^ell known, the four tubercles of the 
human molar commence as similar separate knobs on the dental 

The above are cited as examples to explain the meaning of the 
proposition. When fuller demonstration is desired, a greater num- 
ber might be given. 

B. On Cell- Repetition. 

That each additional act of creation in growth was originally 
iden-tical with one which preceded it, and therefore an exact repe- 
tition in its character and results, is proved by the following con- 

It has been already determined by the study of homologies that 
all organs and iiarts of an organism can be referred to an original 
simple archetype. 

The question then remains as to whether the first element, or 
lowest term, of a given organized part is essentially a new struct- 
ure, or whether it be a repetition of some previously existing one. 
It may be asserted that the simplest expressions which shall cover 
all organs are the solid segment, and the hollow sack, and tube. 
For example, we have already noted that the ultimate element of 
the limb is the first segment of the single ray of Lepidosiren. Is 
this short cartilaginous cylinder (which probably represents the 
fore limb of some undiscovered member of the Dipnoi) a result of 


the repetition of a pre-existent structural element ? This is no 
doubt the case, for, as will be shown beyond, cartilage, though the 
least cellular of all the tissues, is formed originally by cell repetition 
or division. Again, the ultimate lobules of the most complex gland 
are but repetitions of the diverticula of the simply branched, and 
each of the latter repetitions of the simple cul-de-sac, which has 
its origin in a convexity of an originally plane surface. This con- 
vexity is again the result of repetition of cells or cell-division, 
whereby their number is increased and the surface rendered 

We are thus, in both the solid segment and hollow sack, brought 
down to cell-repetition. Thus it is with organs, as with entire 
animals, in which, following the line of simplification, we reach at 
last forms composed of cells only {Actlnojjhri/s, e. g.) and then 
the unicellular {AmoBba). 

If this be the origin of organs, the question whether repetitive 
growth has constructed tissues remains for consideration. 

In growth, each segment — and this term includes the parts of 
a complex whole or parts always undivided (as the jaw of a whale 
or the sac-body of a mollusk) — is constructed, as is well known, by 
cell-division. In the growing foetus the first cell divides its nucleus 
and then its whole outline, and this process, repeated millions of 
times, produces, according to the cell theory, all the tissues of the 
animal organism or their bases, from first to last. That the ulti- 
mate or histological elements of all organs are produced originally 
by repetitive growth of simj)le nucleated cells, with various modifi- 
cations of exactitude of repetition in the more complex, is taught 
by the cell theory. The formation of some of the tissues is as fol- 
lows : 

First Change. — Formation of simple nucleated cells from ho- 
mogeneous protoplasm or the cytoblastema. 

Second. — Formation of new cells by division of nucleus and body 
of the old. 

Tliird. — Formation of tissues by multiplication of cells with or 
without addition of intercellular cytoblastema. 

A. In connective tissue, by slight alteration of cells and addi- 
tion of cytoblastema. 

B. In blood, by addition of fluid cytoblastema (fibrin) to free 
cells (lymph-corpuscles), Avhich in higher animals (vertebrates) de- 
velop into blood-corpuscles by loss of membrane, and by cell-devel- 
opment of nucleus. 


C In muscles, by simple confluence of cells end to end, and 
mingling of contents (Kolliker). 

D. Of cartilage, by formation of cells in cytoblast which break 
up, their contents being added to cytoblast ; this occurring several 
times, the result being an extensive cytoblast with few and small 
cells (Vogt). The process is here an attempt at development with 
only partial success, the result being a tissue of small vitality. 

Even in repair-nutrition, recourse is had to the nucleated cell. 
For Cohnhcim iirst showed that if the cornea of a frog's eye be 
scarified, repair is immediately set on foot by the transportation 
thither of white or lymph or nucleated corpuscles from the neigh- 
boring lymph-heart. This he ascertained by introducing aniline 
dye into the latter. Eepeated exi^eriments have shown that this 
is the history in great part of the construction of new tissues in 
the adult man. 

Now, it is well known that the circulating fluid of the foetus 
contains for a period only these nucleated cells as corpuscles, and 
that the lower vertebrates have a greater proportion of these corpus- 
cles than the higher, whence probably the greater facility for repair 
or reconstruction of lost limbs or parts enjoyed by them. The in- 
vertebrates possess only nucleated blood-corpuscles. 

C. Synthesis of Repetition. 

That growth-force is capable of exhibiting great complexity of 
movement with increase in amount, will now be shown. That this 
quality of complication is one of its distinguishing features will 
appear plain. 

The simplest forms of life, as stated by Haeckel, are simply ho- 
mogeneous drops of protoplasm {Protammba). These only grow 
by ordinary accretion, and display a form of self division or repro- 
duction which is the simplest possible — i. e., the bisection of the 
mass by contraction at opposite points. 

The next grade of animal type is represented by the nucleated 
cell. This is simple in Amceba, complex in Actinoph7'ys, etc. 
With such forms as the latter, cell-growth begins, and its develop- 
ment is accomplished, by cell-division. This is simple repetition 
of ultimate parts. In the growth of all higher types we have 
nothing more than this, but following a law of complex repetition. 
Thus in the growth of the parts of an archetypal vertebral column 
or an archetypal limb, we have the repetition of cell-growth till 
the first segment is formed, when it ceases at that point, and re- 


peats the process again, forming another segment like the first; 
repetition within repetition. So with the construction of muscu- 
lar tissue ; first, the nucleated cell repeated in a series, whose 
adjacent walls disappear, and whose cell-contents flow together, 
thus forming a fibrilla ; then a repetition of the same process, 
forming a second fibrilla ; and so on to the completion of thou- 
sands of them in fasciculi. 

Let us then trace the series of repetitions and duplicated and 
still more complex repetitions, seen in following up animal forms 
from their archetypes. 

In the simplest repetition of cell-growth in a longitudinal 
direction we have Vibrio ; in the centrifugal, Actinoplirys. The 
former may be represented by a line of simple dots, thus : Eig. 1. 


3, /■4:'*'*'='5y-?''-"-^''/'4"'^i5\''Xi'i^^^ 

V V 

6 /^^H^;%^^^vt^i5>v^=??•,^0=fth/^^^'^^^^ 

7 duo tiOoQtsba JS. o o Q a Q C3 CD cS c^ O O 
7 O oQOt)C3 ^X3 o oodOocnfcn cci> o ^^O. 

In a complex repetition we rarely have the same degree of com- 
plication in each repeated part. We have it centrifugally almost 
perfect in a Coelenterate (Actinia), and linearly in some of the 
lower vermes. An archetype of the latter kind might be repre- 
sented thus : Fig. 2. In a more complex form, as of the pro- 
glottides of Tmnia, thus : Fig. 3. The same might represent an 
archetypal vertebrate. 

If now we attempt to express the complication of an organ by 
modified repetition of once identical parts, the history of extremi- 
ties will serve us. Thus the limb of Lepidosiren, which is com- 
posed of identical segments, may be thus represented : Fig. 3. 
Each longitudinal segment of the limb of Ichthyosaurus may be 
similarly represented with a modification, in size only, of the 
proximal or humerus ; thus : Fig. 4. But in Flesiosaurus an 
important series of changes of shape (but not in complexity) ap- 
pears, which may be rejiresented thus : Fig. 5 ; the first being 


humerus, second ulna, third and fourth carpals (tarsals), the last 
phalanges, which are first specialized in this genus. 

By far the most usual modification is, however, complication by 
duplicated and triplicated and still more highly multiplied repeti- 
tion in some segments of the archetype, and its omission in other 
segments. Thus in the Tcenia, the cephalic segments are much 
modified, and the nature of the repetition might be thus ex- 
pressed : Fig. 6 ; the simpler segments representing the body 
segment, the two complex representing those of the head. In 
each, it will be observed, the complication is represented by loops 
of similar form, and each loop of dots which represent the cells in 
the first linear (Fig. 1) arrangement. 

A somewhat similar figure might represent the nature of the 
com23lication in the Myriapod. In the insect the additional com- 
plications of the thoracic segments would alter the diagram near 
the middle. 

In the vertebrate cranium a somewhat similar diagram might 
be used, except that the modification of the segments or vertebrae, 
as compared with the segments of the vertebral column, is not by 
rcj)etition with modification of the parts of each segment, but 
rather by modification of the forms of the parts of the segments. 
The basicranial segments thus compare with the dorsal vertebrse 
as the segments of the limb of Flesiosaurus do with those of Ich- 

The above considerations have reference to repetition of parts 
in a linear direction. Centrifugal repetition is seen in the addi- 
tion of chambers to the heart, by the subdivision in the earliest 
stages into auricle and ventricle in the linear direction, con- 
sidered in connection with the earlier division of each in the 
transverse direction by the growth of partitions. This mode of 
repetitive addition is not readily represented by diagram. 

A good example of rej^etitive addition, in both linear and 
transverse direction, may be found in the successive complication 
of tooth structure seen in Mammalia. In the dolphin, the dental 
series may bo represented thus : Fig. 7 ; in the squalodon thus : 
Fig. 8 ; in the cat : Fig. 9 ; in the dog : Fig. 10 ; in man : Fig. 
11 ; in some Insectivora : Fig. 12. 

The circles represented here are each a simple cusp. 

In conclusion, the directions of repetitive growth may be 
tabulated as follows : The types to the left represent the original ; 
to the right, the derivative : 



Longitudinal antero-pos- 
terior and bilateral. 

More bilaterally j ^ , bilateral 
symmetrical. ( "^'^ ''"'^teral. 

More antero-pos- ( Only antero- 
teriorly. \ posterior. 

i In plane. 
Centrifugal. •< 

( In globe. 

D. On Groivth- Force. 

From such examples as those that precede, but more especially 
from the last, it seems necessary to believe that there resides in 
organized matter, and in its most unmodified representative, the 
nucleated cell, an affection which displays itself in repetition. 
This phenomenon reduced to its lowest terms, may mean cell-divis- 
ion only, but the proof is only clear in cases of growth proper. 
This affection displays itself in very slow or more rapid repetitions 
— cell-division in growth occurring rapidly, while its recurrences 
at rutting seasons in the development of horns, feathers, etc., are 
separated by long intervals of time. In acceleration these repeti- 
tions occur with increased rapidity, i. e., in the adding of more 
structures during the same growth periods, while in low types its 
repetitions are few and therefore slow. 

What is the relation of cell-division to the forces of nature, and 
to which of them as a cause is it to be referred, if to any ? The 
animal organism transfers solar heat and the chemism of the food 
(protoplasm) to correlated amounts of heat, motion, electricity, 
light (phosphorescence), and nerve force. But cell-division is an 
affection of protoplasm distinct from any of these ; although addi- 
tion to homogeneous lumps or parts of protoplasm (as in that low- 
est animal, Protammha of Haeckel) should prove to be an exhibi- 
tion of mere molecular force, or attraction, cell-division is certainly 
something distinct. It looks like an exhibition of another force, 
which may be called groioth-force. It is correlated to the other 
forces, for its exhibitions cease unless the protoplasm exhibiting it 
be fed. 

Professor Henry pointed out many years ago that this must be 
the case, basing his belief on the observed phenomena of growth in 
the potato, and in the Qgg,. The starch of the potato weighs much 
more than the young shoot of cellulose, etc., into which it has been 
converted by growth-activity, so that a portion of the substance 
of the tuber has evidently escaped in some other direction. This 


is shown to be carbonic acid gas and water, derived from the slow 
combustion of the starch, which in thus running down from the 
complex organic state to the more simple inorganic comjiounds, 
evolves an amount of force precisely equal in amount to the chemi- 
cal force (or chemism) requisite to bind together the elements in 
the more complex substance.* 

Carpenter also states that in his opinion the growth of the Fungi 
is produced by a force liberated by the retrograde metamorphosis 
of their food, which is of an organic character (i, e., humus). 
This metamorphosis consists, as in the tuber, in the production of 
carbonic acid gas and water, and a force equivalent to the chemism 
which had bound them in the former complex union, f But in 
higher forms of vegetable life, and in growth that follows germina- 
tion, the plant must appropriate carbon from the carbonic acid of 
the atmosphere. The decomposition of the binary compound 
(which sets free its oxygen) liberates the chemical force which had 
previously maintained the compound (or an equivalent force), which 
Henry regards as furnishing the growth-force, which produces the 
plant. Carpenter derives but a portion of the force in this way, 
obtaining the greater part from the heat of the sun. To this source 
also he looks for the heat necessary to the construction of cold- 
blooded animals ; while in warm-blooded animals, the retrograde 
metamorphosis or running down of the material (protoplasm) of 
the food furnishes a requisite amount of heat. 

Growth-force we may then regard as potential in organized tis- 
sue, and as energetic during growth. J Our j^resent knowledge 

* "Agricultural Report of the Patent Office," 1857. 

\ " Correlation of Physical and Vital Forces," 1864 (" Quarterly Jour, of Science "). 

\ Bathiuism or growth-force must be static or potential in each unit or plastic! 
(cell) of a living organism, the type differing with each organic species. When it is 
in excess in a given locality it becomes energetic, and builds tissue in various forms. 
A portion of this energy is, in this process, developed as molar motion of nutritive 
material, and is accompanied in the completed structure by the ordinary cohesive 
energy, by which the newly-built material maintains its attachment as a whole and 
in its parts. If living tissue be constructed, a portion of the excess remains as the 
static energy of the plastids or cells of the new part, as it did of the old. The 
spermatozoid is highly endowed with static bathmism, and communicates it to the 
female ovum. The mingling of the two elements in the presence of nutritious ma- 
terial presents an excess, and form-building results. Its activity will regulate sub- 
sequent new growth, by giving the motion of nutritive material its proper direc- 
tion. When the tissue dies, this energy must leave behind a dynamic equivalent, 
but what this may be is as yet a mystery. (Ed. 1886.) 


only permits us to believe that other force is only converted into 
it under the influence of pre-existent life, but of the real cause of 
this conversion we are as ignorant as in the case of the physical 

In the animal organism, different tissues display different de- 
grees of " vitality." The most vital display cell-organization and 
its derivative forms, while the least so, approach nearer to homo- 
geneity. As organized tissue is the machine for converting vital 
forces, we may believe that less growth-force is potential as such in 
cartilage than in muscle, for it is formed by a retrograde process, 
by which cells once formed are mostly lost, and the contents form 
the intercellular, nearly structureless mass characteristic of this 
tissue. Growth-force must be here liberated in some other form, 
perhaps the mere cohesive force of the former or "dead" inter- 
cellular substance. 

The higher vitality we may believe to result from the greater 
perfection of the more complex macliine as a force converter, as 
compared with the inefficiency of the more simple. 

E. On the Direction of Repetition. 

It has been already pointed out that growth-force exhibits itself 
in cell or segment repetition. The forms in which it thus displays 
itself may be briefly considered. The approximate cause is treated 
of in the next chapter ; but enough may be shown here to indicate 
that duplication and complex duplication is the law of growth-force, 
and that therefore this process must always follow an increase in 
amount in any given locality. 

The size of a part is then dependent on the amount of cell-divis- 
ion or growth-force, which has given it origin, and the number 
and shape of segments is due to the same cause. The whole ques- 
tion, then, of the creation of animal and vegetable types is reduced 
to one of the amount and location of gr oivth force. 

Kepetition is of two kinds, centrifugal and longitudinal. As 
an example of the former, the genus Actinophrys has been cited, 
where the animal is composed of cells arranged equidistally around 
a common center. The arrangement in this type may be dis- 
coidal or globular, providing no definite axis be discoverable. As 
an example of longitudinal repetition, Vibrio, and numerous 
cellular plants may be cited, where the arrangement is in a single 

In by far the greater number of animals these kinds of repeti- 


tive structure co-exist. The longitudinal is, however, predomi- 
nant in the Vertebrata, Mollusca, and Articulata, while the ce7i- 
trifngal is greatly developed in the Cmlenterata and Radiata. In 
none but the simplest forms are either of these modes to be found 

The centrifugal repetition, or addition, more nearly resembles 
the mode of aggregation of atoms in inorganic or crystalline 
bodies, and hence may be regarded as the inferior manifestation. 
It implies that growth-force in this case conforms to a law of 
polarity in exhibiting itself at equal distances from a center — 
which is allied to ordinary molecular force, and independent of 
the localizing influences of which higher organisms seem capable. 
In centrifugal animals, then, the latter evidently plays an in- 
ferior part. In Coelenterates and Eadiates, however, the body 
possesses a short longitudinal axis, in some {Asterias) very short, 
in others {Holothuria) more elongate. The amount of com- 
plication of centrifugal growth greatly exceeds the complication 
in a longitudinal direction in all of these animals except the 

It is now important to observe that great numbers of centrifu- 
gal animals are sedentary or sessile ; while the longitudinal are 
vagrant, moving from place to place. Many of the centrifugal 
animals which wander, do not do so in the direction of their axis, 
but sideways {Medusm). It is also proper to notice that not only 
the movements of the muscles but also the direction taken by 
the food is in the long axis. It is therefore to be concluded that 
in longitudinal animals growth-force has assumed a more truly 
animal type, and that this tendency has predominated over the 
polar or molecular tendency. 

In most longitudinal animals, however, certain lateral portions, 
limbs, etc., extend on each side of the axis ; and were the space 
marked by their extremities, and the extremities of the axis, filled, 
we would have the outline of a centrifugal animal. 

Before discussing the influenees Avhich have increased and lo- 
cated growth-force, it will be necessary to point out the mode in 
which these influences must necessarily have effected growth. 
Acceleration is only possible during the period of growth in ani- 
mals, and during that time most of them are removed from the 
influence of physical or biological causes, either through their 
hidden lives or incapacity for the energetic performance of life 
functions. These influences must, then, have operated on the 



parents, and become energetic in the growing foetus of the next 
generation. However little we may understand this mysterious 
process, it is nevertheless a fact. Says Murphy, '' There is no act 
which may not become habitual, and there is no habit that may 
not be inherited." Materialized, this maybe rendered — there is 
no act which does not direct growth -force, and therefore there is 
no determination of growth-force which may not become habitual ; 
there is, then, no habitual determination of growth-force which 
may not be inherited ; and, of course, in a growing foetus becomes 
at once energetic in the production of new structure in the direc- 
tion inherited, which is acceleration. 

But if the forces converted into growth-force are derived from 
without the animal organism, whence and what the agency by 
which the acceleration or retardation of the latter is inherited 
from the parent ? A few suggestions only on this head can be 
made in the fourth section. 


Up to this point we have followed paths more or less distinctly 
traced in the field of nature. The positions taken appear to me 
either to have been demonstrated or to have a great balance of 
probability in their favor. In the closing part of this paper I 
shall indulge in more of hypothesis than heretofore. 

Since repetitive addition only produces identical results in 
archetypes, and each effort produces results more and more unlike 
its predecessor as structure becomes specialized, it becomes im- 
portant to examine into the influences which have originally 
modified the repetitive efforts successively, producing structures 
more or less different in detail in the second generation from 
those of the parents, in acceleration, or the reverse, in retarda- 

Going further back, the question arises, why a simple exhibi- 
tion of repetition (e. g., cell-division) should be converted into a 
complex or duplicated repetitiotf (e. g., jointed ray). This, it has 
already been stated, is one consequence of increased amount of 
the growth-force. 

We then seek explanation of the main question, as to what de- 
termines the location of this additional or new growth-force. 
(Div. A.) 

Lastly, why the total amount of this force should change in a 
given individual or part of an individual. (Div. B.) 


A. Oil the Location of Groivtli-Force. 

"What are the influences locating growth-force ? The only- 
efficient ones with which we are acquainted, are, first, physical 
and chemical causes ; second, use ; and I would add a third, viz. : 
effort. I leave the first, as not especially prominent in the econo- 
my of type-growth among animals, and confine myself to the two 
following. The effects of use are well known. We can not use 
a muscle without increasing its bulk ; we can not long use the 
teeth in mastication without inducing a renewed deposit of den- 
tine within the pulp-cavity to meet the encroachments of attri- 
tion. The hands of the laborer are always larger than those of 
men of other pursuits. Pathology furnishes us with a host of hy- 
pertrophies, exostoses, etc., produced by excessive use, or neces- 
sity for increased means of performing excessive work. The 
tendency, then, induced by use in the parent, is to add segments 
or cells to the organ used. Use thus determines the locality of 
new repetitions of parts already existing, and determines an in- 
crease of growth-force at the same time, by the increase of food 
always accompanying increase of work done, in every animal. 

But supposing there be no part or organ to use. Such must 
have been the condition of every animal prior to the appearance 
of an additional digit or limb or other useful element. It ap- 
pears to me that the cause of the determination of growth-force 
is not merely the irritation of the part or organ used by contact 
with the objects of its use. This would seem to be the remote 
cause of the deposit of dentine in the used tooth ; in the thicken- 
ing epidermis of the hand of the laborer ; in the wandering of 
the lymph-cells to the scarified cornea of the frog in Cohnheim's 
experiment. You can not rub the sclerotica of the eye without 
producing an expansion of the capillary arteries and correspond- 
ing increase in the amount of nutritive fluid. But the case may 
be different in the muscles and other organs (as the pigment cells 
of reptiles and fishes) which are under the control of the volition 
of the animal. Here, and in many other instances which might 
be cited, it can not be asserted that the nutrition of use is not 
under the direct control of the will through the mediation of 
nerve force. Therefore I am disposed to believe that growth- 
force may be, througli the motive force of the animal, as readily 
determined to a locality where an executive organ does not exist, 
as to the first segment or cell of such an organ already com- 


menced, and tliat therefore effort is, in the order of time, the 
first factor in acceleration. 

Addition and subtraction of growth-force, in accordance with 
the modes pointed out below, account for the existence of many 
characters which are not adaptive in their nature. 

Acceleration under the influence of effort accounts for the ex- 
istence of rudiments of organs in process of development, while 
rudiments of organs in process of extinction are results of retarda- 
tion, occasioned by absolute or complementary loss of growth-force. 
Many other characters will follow, at a distance, the modification 
resulting from the operation of these laws. 

Examples of the Influence of Physical Causes. — This is nowhere 
better seen than in the case of coloration, which requires the light 
of the sun for its production. The most striking examples of this 
are seen in the colorless surface of animals inhabiting the recesses 
of caves, as the blind craw-fish and the Amblyopsis, etc. If- evolu- 
tion be true, these have descended from more highly colored pro- 
genitors. The flat fishes, also {Pleuronectidce), as is known, swim 
on one side in adult age, but many of them are hatched symmetrical 
fishes, or nearly so, one eye rotating from one side to the other by 
a twisting of the cranial bones. It is thus probable that they have 
descended from symmetrical fishes, which were similarly colored 
on both sides. Now the lower side is colorless, the upper retain- 
ing often brilliant hues. The influence of sunlight is thus as dis- 
tinctly discoverable among animals as among plants, where it has 
been generally accepted as a principle of vegetable physiology.* 

Examples of the Effects of Effort and Use. — a. The Respiratory 
and Circulatory System of Vertebrates. — It is well known that the 
succession of classes of Vertebrates is measured first by their adapta- 
tion to aeration in water, and then by their successive departures 
from this type in connection with the faculty of breathing air. 
The same succession of structure is traversed by the embryos of 
the vertebrates, the number of stages passed being measured by 
the final status of the adult. This transition takes place in the 
Batrachia later in development than in any other class. Now, it 
is well known that the transition or metamorphosis may be delayed 

* In this and similar cases, care must be taken not to misunderstand the writer 

by supposing him to mean that in each generation separately the peculiar coloration 

is the result of changed exposure to light. The evolutionist will understand that the 

effect of such influence increases with succeeding generations by the addition to in- 

.herited character of the effect of immediate external cause. 


or encouraged by suppression of use of the branchial and encourage- 
ment of use of the pulmonary organs, or the reverse. 

The aquatic respiration of tadpoles may be indefinitely pro- 
longed by preventing their access to the surface, and it is known 
that in nature the size or age of the larva at time of metamorphosis 
may vary much in the same species. If perennibranchiates {Siren, 
e. g.) are deprived of their branchiae, they will aerate blood by 
the lungs exclusively, and there is no reason to doubt that by use 
of these, and disuse of the branchia3, aerial respiration might be- 
come the habit of the animal. It is also easy to perceive that geo- 
logic changes would bring about a necessity for precisely this change 
of habit. This occurred in the period of the coal measures, where 
large fresh-water areas were desiccated, and it was precisely at this 
period that many air-breathing Batrachians originated and had a 
great development. 

i3. The rattle of the Rattlesnake. — Nearly all the larger harm- 
less snakes which live on the ground have a habit of throwing the 
end of the tail into violent vibrations when alarmed or excited, 
with the view of alarming a supposed enemy. Among Coronelline 
snakes, Ophibolus triangulus possesses it ; among the water snakes, 
Tropidonotus sipeclon. In the typical Colubrine group the black 
snake, Bascanium constrictor, is an example ; Pityophis sayi also 
shakes the tail violently. The copperhead {Ancistrodon contor- 
trix) and the moccasin {A. piscivorus) (fide Giinther) have the 
habit in a marked degree. Among the rattlesnakes it is a means 
of both warning and defense, in connection with the rattle which 
they carry. 

In the structure of the end of the tail of harmless snakes, we 
see a trace of the first button of the rattle in a horny cap that covers 
the terminal vertebrae. In the venomous genera, it is conspicuous 
in Lachesis especially, reaching a considerable length and having 
a lateral groove. In the plate-headed rattlesnakes {Crotalus) this 
corneous cap is inflated into a button with lateral groove, and in 
some of them possesses only one or two buttons or joints. In the 
perfected rattlesnakes {Caudisona) not only are the segments nu- 
merous and inflated, but a number of the terminal caudal vertebra? 
are greatly enlarged vertically, and co-ossified into a mass.* This 
is important from the fact that the rattlesnakes are the most spe- 

* Soc good figures of this structure in " Zcitsehr. f. wissensch. Zoologic," viii, 
Tab. 12. 


cialized of all snakes, standing at the head of the order, and as 
such, on the principle of acceleration, present the greatest amount 
of grade-nutrition. 

Now it appears to me that the constant habit of violent vibra- 
tion in a part tends to determine an increased amount of nutritive 
fluid to it, in other words to localize growth-nutrition, and when 
this has attained complex repetition or grade-nutrition, to result 
in new grade-structure. (The segments of the rattle being nearly 
all alike, it is a case of simple repetition.) This view appears to 
be as reasonable as that generally entertained with regard to the 
cause of spavin in the horse's leg. Here, owing to excessive use, 
exostoses appear on the bones surrounding the tibio-tarsal articula- 
tion. As to the reason of the structure in question not appearing 
in forms lower in the scale than the rattlesnake, it is explained 
below, if the law of accumulation of grade-nutrition be true. (See 
Sec. B.) This is, that repetition (or acceleration) is only possible 
where the animal has an excess of growth-force at its disposal, or 
can abstract it from some portion which is unused or useless. 

y. On horns. — The possession of horns on the posterior part 
of the cranium, as defenses against enemies, is a character found 
in many distinct types of animals. (Herbivora have no (dental) 
weapons and need horns.) It is seen in the Batrachia Stego- 
cephala in the extinct genus Ceraterpeton ; sawoi^g Anura it is 
approached by Triprion and Hemipliractus. Among Eeptilia it 
is well marked in Phrynosoma, a Lacertilian genus. In Mamma- 
lia the Artiodactyla Ruminantia are the horned animals of the 
order. We have opportunities of observing the habits of these 
representatives of the Frogs, the Lizards, and the Mammals. 

In the first case, any one who has kept ordinary toads and 
tree-toads in confinement, is aAvare that when attacked and unable 
to escape, they defend themselves by presenting the top of the 
head forward and using it as a shield. Now I have already 
pointed out * that in both toads, tree-toads, and frogs there are 
natural series of genera, measured by the degree of ossification of 
the superior cranial walls, the longest being that of the HylidiB, 
which embraces six terms, viz. : Hylella, Hijla, Scytopis, Osteo- 
cephalus, Trachyceplialus, and Triprion. The two last have the 
head thoroughly shielded, and Hemipliractus has projecting an- 
gles which appear in some South American forms, described by M. 

* " Origin of Genera," 1868, p. 14. This work, article I. 


Espada, to be developed into short horns. That this excessive 
ossification is associated with the habit of protecting the whole 
body with the front seems likely. 

In the case of Phrynosoma we know that precisely the same 
habit is associated with the presence of the sharp horns ; and that 
some genera without horns possess it also. Phrynosoma is an ex- 
ceptionally sluggish genus in a family of most active forms, and 
must necessarily resort to this mode of defense more than they. 

In the case of Euminants, we also know that defense is accom- 
plished by throwing the head down with the horns thrown for- 
ward. But this is not confined to this group. That generalized 
suborder, the Artiodactyla Omnivora, represented by the hog, 
which were no doubt the genetic predecessors of the Euminants 
in time, also throw the head down in defense in the same way, 
having thus a manner totally distinct from that seen in the Car- 
nivor'a. The latter show their teeth and often crouch j^repara- 
tory to a leap. 

These cases present so constant an association between habit 
and use that, admitting evolution, we are compelled to believe 
that the structure has given rise to the habit or the habit to the 
structure. In the former case we have to suppose, with the au- 
thor of "Natural Selection," that among the many spontaneous 
variations rudimental horns occasionally appeared, and that their 
possessors, being thus favored in the struggle for existence, were 
preserved and multiplied ; while those not favored dwindled, and 
were ultimately nearly all extirpated or starved. The question 
of origin is here left to chance, and Alfred Bennett has made a 
mathematical estimate of the chances of any particular profitable 
variation occurring among the great number of possibilities of the 
case. This has shown the chance to be so excessively small as to 
amount in most cases to a great improbability. 

If we turn to the probabilities of such structure having arisen 
through the selection of that mode of defense by the animal, we 
find them greatly increased. The position occupied by the horns, 
in all the animals described, is that which is at once brought into 
contact with an enemy in conflict, and as sport among animals is 
a gentle imitation of conflict, the part would be constantly excited 
in sport as well. With an excess of growth-nutrition, our knowl- 
edge O'f the effects of friction on the epidermisj and of excessive 
ligamentous strain and inflammation on bone (e. g., spavin in 
horses), as well as of abnormal exostoses in general, would warrant 


us in the belief that the use of the angles of the parts in question 
in these animals would result in a normal exostosis, of a simple 
kind in the frogs, or as horn cores in the Rumiuantia.* As to the 
sheatiiing of the cores in tlie Bovidm, and nakedness in the Cer- 
vidcB, it is in curious relation to their habitat and to tlieir habits. 
The epidermis and derm would of course share in the effects of 
friction. In the Bovidae which dwell in treeless plains, or feed 
on the grasses in great part, the development of these coverings of 
the horn cores into a horny sheath would naturally meet with 
no interruption. In the case of the deer, which mostly live in 
forests or browse on trees, constant contact with the latter would 
prevent the healthy growth of the dermal covering, aud it would 
be liable to injury or constant excoriation by the animals them- 
selves on the branches of trees, etc. This we know to be the pres- 
ent habit of the deer as regards the dermal covering of the horns. f 
I ha,ve elsewhere pointed out the similar connection between the 
dental structure and habitat among the oxen and the deer. The 
former, eating the harder grasses, are provided against the conse- 
quent rapid attrition of the tooth by a prismatic form, which 
allows of more prolonged growth and more rapid protrusion. 
The deer, in accordance with their foliage-eating habits, do not 
wear the crown of the tooth with such rapidity. Long-continued 
protrusion is not so necessary, hence the teeth are more distinctly 
rooted and have a prominence or shoulder, distinguishing the 
body of the crown. 

B. Change in Amount of Growth- Force. 

1. Absolute increase of Growth- Force. — As every type has had 
its period of greatest development in numbers, size, and complica- 
tion of structure, the present law indicates as an exj)lanation, a 
culmination of the process of conversion of growth-force from its 
energetic to its potential state in tissue. The cause is primarily 
the increased exercise of effort and use, which, while effecting a 
conversion, increases the capacity of the organs by which further 
conversion is effected. 

* The now well-known fact that all cranial ossification was primitively dermal, 
is confirmatory of the idea that its appearance was due to moderate friction of the 
skin on resistant bodies. (Ed. 1886.) 

f Palaeontological studies jjo far to show that the origin of the shedding of the 
deer's horn was due to the loss of their dermal covering, and that this was caused by 
violent use. (1886.) 


2. Local increase of Growth-Force. — Examples of a local in- 
crease of this kind are probably to be seen in convoluted organs ; 
as the convolutions of the brain in higher Mammalia ; the convo- 
lutions of the tooth-dentine of the Labyi'inthodont Batrachia ; the 
same phenomenon in the cotyledons or plumule of some seeds. In 
these cases the superficial area of the parts is excessively developed, 
and the inclosing organs not being proportionately enlarged, a 
convolution necessary follows. In the first case, the skull ; in the 
second, the alveolus ; in the third case, the seed-envelope, restrain 
the expanse of the contained j)art, which would otherwise follow 
increase of growth-force. 

3. Absolute loss of Groiuth- Force. — This will follow defective 
nutrition, produced by inability of the animal to obtain heat and 
food requisite to that end. This is supposed to be due, according 
to the view hereafter proposed, primarily to deficiency of intelli- 
gence, in failing to adapt habits to changed physical circumstances, 
and secondarily to the unfavorable influence of such changed cir- 
cumstances. The extinction of highly specialized types, which 
has closed so many lines of animal types, will be accounted for by 
their less degree of plasticity and want of capacity for change un- 
der such changed circumstances. Such changes consist of modified 
topography and temperature, with irruptions of many new forms 
of life by migration. The less developed forms would be most 
likely to experience modification of structure under a new order 
of things, and paleontology teaches that the predecessors of the 
characteristic types of one period were of the less specialized forms 
of that period which went before. 

Thus is explained the fact that, in following out the line of 
succession of animal forms, we have constantly to retrace our steps 
from specialized extremes (as osseous fishes, tailless Batrachia, 
song birds, etc.) to more generalized or simple forms, in order to 
advance beyond. 

4. The complementary diminution of growth-nutrition follows 
the excess of the same in a new locality or organ, of necessity, if 
the whole amount of which an animal is capable be, as I believe, 
fixed. In this way are explained the cases of retardation of char- 
acter seen in most higher types. The discovery of truly comple- 
mentary parts is a matter of nice observation and experiment. 
Perhaps the following cases may be correctly explained. 

A complementary loss of growth-force may be seen in absence 
of superior incisor teeth and digits in ruminating Mammalia, where 


excessive force is evidently exiDended in the development of horns, 
and complication of stomach and digestive organs. The excess 
devoted to the latter region may account for the lack of teeth at 
its anterior orifice, the mouth ; otherwise, there appears to be no 
reason why the ruminating animals should not have the superior 
incisors as well developed as in the odd-toed (Perissodactyl) Un- 
gulates, many of which graze and browse. The loss to the osseous 
system in the subtraction of digits may be made up in the develop- 
ment of horns and horn-cores, the horn sheath being perhaps the 
complement of the lost hoofs. It is not proposed to assert that 
similar parts or organs are necessarily and in all groups comple- 
mentary to each other. The horse has the bones of the feet still 
further reduced than the ox, and is nevertheless without horns. 
The expenditure of the complementary growth-force may be sought 
elsewhere in this animal. The lateral digits of the Equidm are 
successively retarded in their growth, their reduction being marked 
in Hippotherium, the last of the three-toed horses ; it is accom- 
panied by an almost coincident acceleration in the growth-nutri- 
tion of the middle toe, which thus appears to be complementary 
to them. 

The superior incisors of the Artiodadyla disappear coincident- 
ally with the appearance of horns, which always exist in the tooth- 
less division of the order, except in some very small antelopes 
{Cephalopliu^, etc.) where the whole amount of growth-force is 
small. Possibly the superior incisors and horns are complementary 
here. The retardation in development of the teeth in the higher 
apes and men, as compared with the lower apes, is coincident with 
the increase of number of brain convolutions. That this is not 
necessarily coincident with reduction of teeth in other groups is 
plainly proved by the rodents and ChiromyH, where the loss of many 
teeth is complementary to the great size of the incisors of the mid- 
dle pair. But in man there is no complementary increase of 
other teeth, and the reduction is no doubt due to contraction of 
the Jaws, which is complementary to increase in other parts of the 
cranium, in both apes and men. 

I am confident that the origin and loss of many structures may 
be accounted for in this way, and the correlation of parts to each 
other be measured accurately. 

Ohjectio7i. — The first one which arises is that which the author 
of the ''Vestiges of Creation " made against Lamarck's theory of a 
similar kind, i. e., that by assuming that effort, use, and physical 


causes have originated modifications of structure, we give the 
adaptive principle too much to do. I have made the same objec- 
tion to the theory of natural selection. It is true that an applica- 
tion to a purpose is involved in the present theory of the "location 
of growth-force "' ; but in point of fact, a large number of non- 
adaptive characters are accounted for by it. These are the rudi- 
mental and transitional ones which mark the successive steps pre- 
liminary to the completion of an adaptive structure ; second, those 
produced by deficiency of growth-force in less favored regions of 
the body ; and third and fourth, phenomena consequent on general 
deficiency and excess of growth-force. 

And it may be said in conclusion that if the three principles, 
or if use especially, should be found to be inadequate to the service 
here demanded of them, it may be at least said that they, or the 
last named, constitute the only controllers of growth-force to any 
degree at all with which we are acquainted. 


The object of the present section is the attempt to discuss how 
the influence of effort and use on the parent is placed in a position 
to be inherited by the offspring. 

A. Of the nature of Grade-Influence. 

In the first place, it is necessary to note the definition and char- 
acter of grade-influence. 

a. Growth- force uninfluenced by grade-influence simply adds 
tissue either («) in enlarging size, or {b) in replacing waste. It 
does this by repeating the cell, by division, in localities which have 
already assumed their specific form. This form of growth-force 
may persist throughout life, but with diminished energy in age. 

/3. Grade-influence directs growth-force in building up the tis- 
sues into organs, and constructs the parts of the body successively 
to completion, the result expressing the type or grade of the ani- 
mal or plant. Its energy terminates with maturity, except in 
cases of periodical reproduction of sexual ornaments of the male 
(birds, deer), where it continues throughout life, appearing at 
regular intervals. 

But it has occurred in acceleration that instead of a siniiile repe- 
tition of tlie ultimate histological element of an organism, in add- 
ing to its amount, it adds a completely organized part of the struct- 


ure, as a tube, a phalange, a digit, a limb or an arch ; an ocellus 
or a tooth. For instance, in the genus Ambly stoma, one section 
possesses four phalanges on the longest digit ; another section 
exhibits but three. In the species A. tnavortium, some individuals 
have the small number of phalanges, but the majority possess the 
larger number. As all are of common parentage, a whole phalange 
has been lost or added. The explanation of this phenomenon is 
essential to the compreliension of the origin of type structures. 

* In plants, growth-nutrition continues throughout life, but in 
the higher plants it is more active during the earlier years in peren- 
nial species, addition to size becoming less and less marked with 
increasing age. Grade-nutrition also persists throughout life, but 
is chiefly active during a short period only of every year, or during 
flowering and fruiting. Not only in the production of the repro- 
ductive organs, but also in the yearly additions to other typical 
parts of the plant, grade-nutrition is active. 

** In animals, growth-nutrition is more active in the early 
stages of life, but is continued throughout in the lower divisions ; 
in the highest, it is also continued throughout life, but there is a 
greater contrast between its results during youth, when nearly the 
whole size is attained, and during age, where the additions are 
much less. 

Grade-nutrition is, on the other hand, entirely confined to in- 
fancy and youth, except in those low animals which produce their 
reproductive organs periodically (some Entozoa, etc. ), where it may 
be said to be in nearly the same condition as in plants. 

7. While the amount of simple growth-force, represented in 
adult living animals, has varied very irregularly throughout the 
animal kingdom, there being large and small in every division, it 
would seem to have accumulated, on the whole, Avith the rising 
scale of animal types. Thus the lower or Protozoa are the small- 
est ; Radiates are next in size ; Molluscs and Articulates reach 
nearly the same maximum, which exceeds that of the Radiates, 
and falls far below that of the Vertebrates. Among the last the 
Mammalia have attained as large if not larger size than any of the 
other orders (e. g., Cetaced). This is, however, not necessary to 
the history of evolution. 

That an increased amount of grade growth-force has been con- 
stantly rendered potential during the advance of time is clear, if 
the preceding inferences be true. It is also evident that some in- 
dividuals have accumulated it more rapidly than others, if all 



alike originated from the simplest forms known to ns. Multi- 
tudes have remained in the earliest stages {Protozoa) of the whole 
series, or of their own special series {Lingula), forming "persist- 
ent types " ; or taken directions which rendered them incai)able 
of expansion beyond a certain point without exhaustion or death ; 
for example, complicated types, as AmmonitidcB. The quadruma- 
nous animal, which was the progenitor of man, may thus be be- 
lieved to have acquired a higher capacity of this accumulation 
than his contemporaries. 

Assuming the nucleated cell to be the ultimate element of or- 
ganic tissue, there are two types of life in which grade-influence 
has not appeared, viz. : unicellular animals and plants, and living 
forms composed of homogeneous protoplasm. In the latter neither 
grade-influence nor animal growth-force is potential ; in the for- 
mer, simple growth-force only. It is therefore apparent that grade- 
influence has been developed in the organism itself ; perhaps this 
may have been in the plant, through the modified influence of ex- 
ternal physical causes ; in the animal, if our inductions as to use 
and effort be true, under the influence of the activities of the par- 
ent, which determined a structural change either in itself or in 
its offspring. The possibilities of this origin are considered in the 
next section. 

8. The Location of GroiutJi- Force proceeds under the direction 
of what Prof. Henry calls "Vital Influence." With this author I 
discard the use of the term "Vital Force," what was originally 
understood by that term being a complex of distinct ideas. The 
Vital forces are (nerve-force) Neurism, (growth-force) Bathmism, 
and (thought- force) Phrenism.^ All these are supposed to be 
correlated to the Physical Forces, but are under direction and 
control of the Vital priyiciple which locates their action, etc., just 
as molecular or atomic constittition determines the locality and 
character of the physical forces. The laws of the vital jirinciple 
and of atomic constitution also determine the nature of the con- 
version of one force into another. Now, since physical and vital 
forces are correlated and convertible, the close relationship of the 
two controlling principles becomes obvious and suggestive of their 

* The objection of President Barnard to thought being an exhibition of a force, 
i3 that " thought can not be measured." This objection does not take into consid- 
eration the two- fold nature of thought. The amount of thought can most assuredly 
be measured, the qnalily of the thought can not. 


Dr. Carpenter, in describing the correlation of physical and 
vital forces, defines the difference of organic species to be similar 
to that prevailing between different chemical bodies (the latter 
depending on different molecular and atomic constitution), which 
leads them " to behave differently " from each other under simi- 
lar circumstances. This may be more fully expressed by saying 
that different species possess different capacities for the location 
of the conversion of the physical forces into growth-force. A 
" descent with modifications " contemplated by a process of evolu- 
tion, signifies a progressive change in this capacity. Acceleration 
means an increase in this capacity ; retardation a diminution of 
it. Grade-influence means the influence which produces this 
change of capacity. 

B. The Origin of Grade-Influence. 

Living protoplasm can convert heat and nutriment into 
growth-force without the agency of the nervous system. This 
is proved by the nutrition of the Protozoa and Ccelenterata, and 
from experiments on the muscles of frogs, etc. In the latter case, 
as is well known, the nerve may be divided, and the muscle retain 
its size if a current of electricity be passed through it, thus sus- 
taining the nutrition. As the presence and structure of the nerv- 
ous system is in relation to the specialization of animal struct- 
ure in other respects, it is very probable that the nervous system is 
in higher animals the agent of the location of growth-force. In 
the lowest it is not affected by any such means. As the nervous 
system is the instrument of the metaphysical peculiarities of the 
animal (emotions, choice, etc.), we may conclude that, in the 
lower animals, location of groAvth-force is influenced by necessity 
without choice ; in the higlier by necessity with choice. 

The impulses derived from the nervous system, it is known, 
may be reflex or automatic in answer to stimuli from without. 
They may become so, also, after having been originated conscious- 
ly or by effort of will. In the case of habits, frequent exercise of 
choice has so impressed the nervous system as to result in its 
repetition of effort, often in opposition to changed choice. 

The influence of effort in muscular action, through the nervous 
system, appears to be, first, to enable it to convert heat to nerve- 
force, and, then, to conduct nerve-force to the involuntary mus- 
cles, or those controlling circulation, where it is converted into 
motion, which thus controls nutrition through circulation. The 


nervous system, like others, develops in caj^acity with use, hence 
probably nerve-tissue converts heat * into nerve-force as muscular 
tissue converts heat into motion. In other words, by repetition, 
the capacity of the nervous system for this conversion of heat is 
known to increase. As the amount of heat converted is in pro- 
portion to the amount of appropriate nerve-tissue (see above), it is 
evident that use and effort increase the amount of nerve-tissue. 

The phenomena of thought render the same modification of 
structure probable. Effort in the direction of thought is supposed 
to convert heat into thought-force. Inasmuch as the more intelli- 
gent animals possess the highest development of cerebral hemi- 
spheres, it is highly probable that brain substance converts heat 
into growth-force also, which produces tissue of its own kind pre- 
cisely as muscle does. 

As different parts of the nervous centers subserve different 
purposes, the development of these parts must proceed approxi- 
mately under the influence of special kinds of effort and use. 
Where, as in the adult, heat is converted into growth-force in the 
tissues to a very limited extent, if the above principles be true, 
the conversion of heat by the nervous system into nerve growth- 
force and tissue is, on the other hand, not terminated. 

Capacity for effecting conversion of force is regarded, as above 
pointed out, as dependent on molecular constitution. Hence we 
conclude that change in that capacity on the part of the nervous 
system involves a molecular change in its constitution. 

Now, we know physical and metaphysical peculiarities of 
parents to be inherited by offspring ; hence, no doubt, the nervous 
structure determinative of growth-force is inherited. This will 
then control the localities of special conversion of heat, etc. 
(from the mother), into growth-force, in accordance with the 
structure of the parent, and the more decidedly, as its own in- 
crease progresses. 

The result will be acceleration, or construction of tissues and 
organs in excess of those of the parent, if the effort or use de- 
voted to a nerve or organ be represented in the nerve-center of 
the parent by a greater amount of force-converting tissue than is 

* The supposition that this and other forms of vital enerjry are derived from 
metamorphosis of heat, was in aecordanee with views held at the time this essay 
was written (1871). The mueh more probable hypothesis is that such energy is 
derived from retrograde metamorphosis of nutritive material. (Ed. 1886.) 


necessary when inherited in the foetus for the construction (by 
conversion) of tissues and organs like those of the parent. 

That this is a partial explanation of inheritance, is rendered 
probable from the fact that the types of structure presented by 
the nervous centers express the grade of the animals possessing 
them far more nearly than those of any other organ or set of or- 
gans. If the brain, like other organs, develops by intelligent use, 
it can not be doubted that this relation of its development to 
grade is not accidental, but that grade-structure * is an expression 
of its capacities, physical and mental. 


As neither use nor effort can be ascribed to plants, and as we 
know that their life history is much more dependent on their sur- 
roundings than is that of animals, we naturally look to the physi- 
cal and chemical causes as having a prime influence in the origina- 
tion of their type-structures. Without greater familiarity with 
the subject, I will not attem2)t to say how far the various degrees 
of growth-force possessed by parent plants, located under the influ- 
ence of meteoric and other surroundings, and preserved, destroyed 
or restricted by natural selection, may account foi* the characters 
of their successors of the j)resent period. But other agencies simi- 
lar to use, that is, automatic movements, may be also introduced 
as an element in the argument. The movements of tendrils seek- 
ing for support may be here considered, and, as Dr. Asa Gray has 
pointed out, have consequences similar to those of use in animals. 
When the tendril seizes a support, growth-force is located at the 
point of contact, for the tendril increases considerably in thick- 

Among animals of the lowest grade, movement must be quite 
similar to those of plants, or automatic from the start, and not 
even at the beginning under the influence of will. Evidence of 
will is, however, soon seen in the determinate movements of many 
of the Protozoa in the seizing of food. With will necessarily ap- 
pears a poiver of choice, however limited in its lowest exhibitions, 
by the lack of suggestive metaphysical qualities, or the fewness of 
alternatives of action presented by surrounding circumstances, to 
animals of low and simple organism. We can, however, believe 

* Grade growth-force is not regarded here or elsewhei-e as a simple form of 
energy, but as a e'ass of energies, which are the rosidtants of the interference of 
mind (i. e., consciousness) with simple growth-force. (Ed. 1886.) 


that the presence of greater or less number of external facilities 
for action characterize different situations on the earth's surface, 
as well as that greater and less metaphysical capacity for perceiv- 
ing and taking advantage of them must exist in different indi- 
viduals of every species of animal, however low, which possesses 
consciousness and will. These qualities must, of course, influence 
effort and use to the advantage of the animal, or the reverse. 

Effort and use have very various immediate stimuli to their 

Use of a part by an animal is either compulsory or optional. 
In either case, the use may be followed by an increase of nutrition 
under the influence of reflex action or of direct volition. 

A compulsory use would naturally occur in new situations 
which take place apart from the control of the animal, where no 
alternatives are presented. Such a case would arise in a submerg- 
ence of land where land-animals might be imprisoned on an island 
or in swamps surrounded by water, and compelled to assume a 
more or less aquatic life. Another case, which has also probably 
often occurred, would be when the enemies of a species should so 
increase as to compel a large number of the latter to combat who 
had previously escaped it. 

In these cases, the structure produced would be necessarily 
adaptive. But the effect Avould sometimes be to destroy or injure 
the animals (retard them) thus brought into new situations and 
compelled to an additional struggle for existence, as has, no 
doubt, been the case in geologic history. 

Direct compulsion would also exist where alternatives should 
be presented by nature, but of which the animal would not be 
sufficiently intelligent to take advantage. 

Most situations in the struggle for existence afford alterna- 
tives, and the most intelligent individuals of a species will take 
advantage of those most beneficial. Nevertheless, it is scarcely 
conceivable that any change or increase of effort, or use, could 
take place apart from compulsion derived from the relation of 
external circumstances, as a more or less remote cause. 

Preservation, with modifications, would most probably ensue 
when change of stimulus should occur gradually, though change 
of structure might occur abruptly, under the law of expression 
points. * 

* See " Origin of Genera," p. 38. 



Choice is influence not only by intelligence, but by the imagi- 
nation and by the emotions. 

Intelligence is a conservative principle, and always will direct 
effort and use into lines which will be beneficial to its possessor. 
Here we have the source of the fittest — i. e., addition of parts by 
increase and location of growth-force, directed by the will — the 
will being under the influence of various kinds of compulsion in 
the lower, and intelligent option among higher animals. 

Thus, intelligent choice, taking advantage of the successive 
evolution of physical conditions, may be regarded as the originator 
of the fittest, while natural selection is the tribunal to which all 
the results of accelerated growth are submitted. This preserves 
or destroys them, and determines the new points of departure on 
which accelerated growth shall build. 

The influences locating growth -force may be tabulated as 
follows : 




Plants with me- 
c h a n i c a 1 move- 
ments ; animals 
with indeterminate 

Animals with de- ^ 
terminate move- I 
ments or will,* but j 
no intelligence. J 

Animals with \ 
will and less Intel- >■ 
ligence. ) 

Animals with \ 
more intelligence. \ 

Physical and ) 
chemical. \ 


V 9 

+- use 

-t- effort under 

-f- choice. 

-1- intelligent choice. 

As examples of intelligent selection, the modified organisms of 
the varieties of bees and ants must be regarded as striking cases. 
Had all in the hive or hill been modified alike, all soldiers, neu- 
ters, etc., the origin of the structures might have been thonght to 
be compulsory ; but varied and adapted as the different forms are 
to the wants of a community, the influence of intelligence is too 
obvious to be denied. 

The selection of food offers an opportunity for the exercise of 

* Will must be here regarded as the answer to stimulus, without any element of 
freedom. See Article XX, on the " Origin of the Will." (Ed. 1886.) 


intelligence, and the adoption of means for obtaining it still 
greater ones. It is here that intelligent selection proves its su- 
premacy as a guide of use, and consequently of structure, to all 
the other agencies here proposed. The preference for vegetable 
or for animal food determined by the choice of individual animals 
among the omnivores, which were, no doubt, according to the 
paleontological record, the predecessors of our herbivores, and per- 
haps of carnivores also, must have determined their course of life 
and thus all their parts, into these totally distinct directions. 
The choice of food under ground, on the ground, or in the trees , 
would necessarily direct the uses of organs in the appropriate 
directions respectively. 

In the selection of means of defense a minor range of choice is 
presented. The choice must be limited to the highest capabilities 
of the animal, since in defense, these will, as a general thing, be 
put forth. This will, however, not be necessarily the case, but 
will depend in some measure on the intelligence of the animal, as 
we readily observe in the case of domesticated species. 

In the case of the rattlesnake, already cited, the habit of rapid 
vibration of the tail appears to me to be the result of choice, and 
not of compulsion. For the cobra of India, for the same pur- 
pose, expands the anterior ribs, forming a hood, which is a very 
different habit.* Here are two alternatives, from which choice 
might be made, and violent hissing is a third, which the species 
of the colubrine genus PityopMs have adopted to some purpose. 
As to the benefit of the rattle, it no doubt protects the animal 
from all foes other than man ; but is rather a disadvantage as re- 
gards the latter, being by a beautiful turn of events a protection 
to the higher animal. 

On the principle of natural selection it might be supposed that 
the harmless snakes which imitate the Cro talus for the sake of 
defense were preserved ; but if the above explanation of the origin 
of the habit in the latter be true, the second explanation is not 
valid. (Since in time the harmless snakes preceded the rattle- 
snakes. Ed. 188G,) 

The power of metachrosis, or of changing the color at will, by 
the expansion imder nerve-influence of special pigment cells, exists 
in most Reptilia, Batrachia, and fishes. It is then easy to believe 
that free choice should, under certain circumstances, so habitually 

* The North American Heterodons possess a similar habit. (Ed. 1886.) 


avoid one or another color as to result finally in a loss of the power 
to produce it. 

Thus, it appears to be a fact that not only are species of fishes 
which dwell in the mud of darker hues than those that inhabit 
clear water, but that individuals of the same species differ in a simi- 
lar manner in relation to their habitats ; those that live in impure 
or muddy waters having darker tints than those of clear streams. 

Land animals present equally abundant and remarkable imita- 
tions of the objects or substances on which they live. This is 
well known in insects and sj)iders, which look like sticks or 
leaves, or the flowers on which they feed. It is seen in reptiles, 
which in very many cases can voluntarily assume the hue of leaf, 
stone, or bark, or have constantly the gray color of their native 
desert sands. 

These cases are largely selective or optional in their origin, for 
though metachrosis is also induced by some external stimulus, as 
an enemy or a food animal, yet other means of escajDing the one 
and procuring the other are generally open. 

These facts pave the way for a consideration of the j)henome- 
non of mimetic analogy, which, though well known to naturalists, 
may be illustrated by the following new facts : 

On the plains of Kansas there is a species of Mutilla whose 
abdomen and thorax are colored ochraceous, or brown-yellow, 
above. A spider of the genus SaUicus is equally abundant, and 
is almost precisely similar in the color of the upper surfaces, so 
much so as to deceive any but a most careful observer. The 
Mutilla being a well-armed insect, and a severe stinger, there can 
be no doubt that the SaUicus derives considerable immunity from 
enemies from its resemblance. 

On the same plains, the Crotalus conflucnUis, or prairie rattle- 
snake, abounds. It is an olive gray, with a series of transverse 
brown dorsal sjjots, and two rows of smaller lateral ones. The 
head exhibits a number of brown and white bands. The prairie 
Heterodon (H. nasicus) possesses not only the same tints but the 
same pattern of coloration, and at a short distance can not be dis- 
tinguished from it. 

In consequence, as one may justly say, this species is, with the 
rattlesnake, the most common serpent of the plains, as it shares, 
no doubt, in the protection which the armature of the Caudisona 
gives its possessor. This is in accordance with the views of Wal- 
lace and Bates. 


A curious case occurred to me in four species of fishes, which 
I took in a small tributary of the Yadkin River, in Eoane County, 
N, C. Among several others, there were varieties of the widely 
distributed species Gliaenobryttus viridis, Hypsilepis ajialostanus, 
and Ptycliostomus pidiensis (each representing a different family), 
which differ from the typical form of each in the same manner, 
viz. : in having the back and upper part of the sides with longi- 
tudinal black lines, produced by a line along the middle of each 
scale. This peculiarity I have not observed in these species from 
any other locality. Until I had examined them I thought them 
new species. 

The only other species presenting such marking in the Yadkin 
River is the large perch, the Roccus Uneatus. According to the 
theory of natural selection a resemblance to this well-armed species 
might be of advantage to the much weaker species in question ; 
yet the same species co-exist in other rivers without presenting 
the same mimicry. 

It is difficult not to urge the importance of the causes already 
regarded as efficient in the origination of structure in the present 
branch of the subject also. We are especially disposed to call in 
use and effort here, after noticing how much more distinctly 
change of color is under the control of the animal, than change of 
shape. It must, however, be borne in mind that similar resem- 
blances exist among plants ; though, as Professor Dyer shows, a 
large majority of these cases occur in species of different floral 
regions. Thus in this case, as in those of structure already cited, 
we appeal first to physical laws in the lowest beings, but with the 
increasing interference of use, effort, and intelligence, as we rise in 
the scale. Thus it is that, in the Vertebrates generally, the mi- 
metic resemblances are found in species of the same region, Avhere 
only an intelligent or emotional agency could be illustrated. If 
among animals as low as butterflies the influence of intelligence be 
denied, that of admiration for the beauty, or fear of the armature, 
of the predominant species imitated, would appear to be sufficient 
to account for the result. Admiration and fear are possessed by 
animals of very low organization, and, with the instincts of hunger 
and reproduction, constitute the most intense metaphysical con- 
ditions of which they are capable. But our knowledge of this 
branch of the subject is less than it ought to be, for animals pos- 
sess many mental attributes for which they get little credit. 

It appears to be impossible to account for the highest illustra- 


tioiis of mimetic analogy in any other way, the supposition of 
Wallace that such forms must be spontaneously produced, and 
then preserved by natural selection, being no explanation. It has 
been shown by Bennett that the chances of such modification aris- 
ing out of the many possibilities are exceedingly small. 

If the above positions be true, we have here also the theory of 
the development of intelligence and of other metaphysical traits. 
In accordance with it, each trait appropriates from the material 
world the means of perpetuating its exhibitions by constructing its 
instruments. These react by furnishing increased means of exer- 
cise of these qualities, which have thus grown to their full expres- 
sion in man. 

VI. - 


The doctrine of evolution of organic types is sometimes appro- 
priately culled the doctrine of derivation, and its supporters, deriv- 
atists. This is because it teaches the derivation of species, genera, 
and other divisions, from pre-existent ones, by a process of modi- 
fication in ordinary descent by reproduction. The opposite or 
creativist doctrine teaches that these forms were created as we see 
them to-day, or nearly so ; and that the natural divisions and spe- 
cies of organic beings have never been capable of change, the one 
into the other. 


The reasons which induce me to accept the derivatist doctrine, 
and to reject the creational, fall under the two heads of probabil- 
ities and conclusive evidence. The probabilities are cumulative in 
their pointings, and strengthen that part of the evidence which 
is, to my mind, conclusive. The reasons why derivation is prob- 
able are the successional relation of increment or decrement of 
structure, observed in : 

1. Systematic relation (taxonomy) ; 2. Embryonic growth 
(embryology) ; 3. In geologic time (paleontology) ; 4. And in the 
coincidence in the successions seen in Nos. 1, 2, and 3. 

The fact that it is necessary to arrange animals in an order cor- 
responding with the phases of their embryonic history is remark- 
able ; but the further fact, shown by paleontology, that the same 
succession marked the ages of past time, at once brings evolution 
within the limits of strong probability. Nevertheless, all this 
might have been a mere system, without transitions between its 

* Abstract of a lecture delivered before the California Academy of Sciences, Oct. 
27, 1879. 


members ; organic types might have been created unchangeable, 
but presenting the mutual relations in question. But if transi- 
tions among these members can be shown to take place, then 
indeed the phenomena mentioned received a sufficient explanation. 
They are seen to be the necessary relations of the parts of a shift- 
ing scene of progression and retrogression ; they express combina- 
tions of structure, which, though often long enduring, are, never- 
theless, not perpetual, but give way to other combinations to be 
in their turn dissolved. Now, if there is anything well known in 
nature, it is that there are divisions of various ranks in the vege- 
table and animal kingdoms, whose contents present variations of 
structure which are confessedly additions to or subtractions from 
the characters of ancestors, which have appeared during ordinary 
descent. The protean species, genera, etc., are well known to 
biologists, and every naturalist who admits varieties, sub-species, 
sub-genera, etc., admits derivation so far as they are concerned. 
The facts of variation, including "sporting," etc., are notorious, 
not only among domesticated, but also in wild animals and plants. 
The facts have led some persons to suggest that species have been 
produced by evolution from a single specific center, but that the 
genus and other comprehensive divisions are unchangeable. But 
I think I have shown, in a paper entitled " The Origin of Gen- 
era," * that the structural characters which define genera, and even 
higher divisions, are subjects of variation to as great an extent as 
are the less profound specific characters ; and, moreover, that the 
evidence of derivation which they present is singularly clear and 
conclusive. The changes of both genus and species character are 
always of the nature of additions to or subtractions from those of 
one generation displayed by their descendants. As such, they 
form the closing chapters of the embryonic or growth-history of 
the modified generation. 

In order to explain more fully the application of the above 
statements, I introduce a few examples selected from the subjects 
of my studies. Their number might be indefinitely extended. I 
first cite the genera of the tailless Batracliia Anura (frogs, toads, 
etc.), whose relations are very simple and clear, and show the 
parallelism between adult structure and embryonic succession. See 
above, 1 and 2. 

The greater number of Batracliia Anura fall into two divis- 

* Philadelphia, 1869. "Proceedings Academy Natural Sciences, 1868." 


Fig. 8. 

Fig. 9. 

ions, which differ only in the structure of the lower portion of 
their scapular arch, or shoulder-girdle. In the one the opposite 
halves are capable of movements which contract or expand the 
capacity of the thorax ; in the other the opposite halves abut 
against each other so as to be incapable of movement, thus pre- 
serving the size of the thoracic cavity. But during the early 
stages, the frogs of this division have the movable shoulder-girdle 
which characterizes those of the 
other division, the consolidation con- 
stituting a modification superadded 
in attaining maturity. Further- 
more, young Anura are toothless, 
and one section of the species with 
embryonic shoulder-girdle never ac- 
quire teeth. So here we have a 
group which is imperfect ia two 
points instead of one. This is the 
tribe Bufoniformia ; the tribe with 
teeth and embryonic shoulder-girdle 
is called the Arcifera, and that 
which is advanced in both these res- 
pects is the Raniformia. Now the 
frogs of each of these divisions pre- 
sent nearly similar scales of develop- 
ment of another part of the skeleton, 
viz., the bones of the top of the skull. 
"We find some in which one of these 
bones (ethmoid) is represented by 
cartilage only, and the frontoparietals 
and nasals are represented by only a 
narrow strip of bone each. In the 
next type the ethmoid is ossified ; in 
the next, we have the frontoparietal 
completely ossified, and the nasals 
range from narrow strips to complete 
roofs ; in the fourth station on the 
line, these bones are rough, with a hyperostosis of their surfaces ; 
and in the next set of species this ossification»fills the skin, which 
is thus no longer separable from the cranial bones ; in the sixth 
form the o.^sification is extended so as to roof in the temporal 
muscles and inclose the orbits behind, while in the rare seventh 

Fig. 10. 


Fig. 8, of the Arciferous type 
(Scaphiopus holhrooki). Fig. 9, 
Eana temporaria, tadpole with 
budding limbs. Fig. 10, do. adult. 
Figs. 9 and 10 from Parker. 


and last stage, the tympanum is also inclosed behind by bone. 
Now all of these types are not found in all of the families of the 
Anura, but the greater number of them are. Six principal fami- 
lies, four of which belong to the Arcifera, are named in the dia- 
gram below, and three or four others might have been added. I 
do not give the names of the genera which are defined as above 
described, referring to the explanation of the cuts for them, but 
indicate them by the numbers attached in the plate, which corres- 
pond to those of the definitions above given. A zero mark signi- 
fies the absence or non-discovery of a generic type. 

Sternum embryonic. 

Sternum complete. 




and Pelobatidse. 




































It is evident, from what has preceded, that a perfecting of the 
shoulder-girdle in any of the species of tlie Bufoniform and Ar- 
ciferous columns would place it in the series of Raniformia. An 
accession of teeth in a species of the division Bufoniformia would 
make it one of the Arcifera ; while a small amount of change in 
the ossification of the bones of the skull would transfer a species 
from one to another of the generic stations represented by the 
numbers of the columns from one to seven. 

There are few groups where this law of parallelism is so readily 
observed among contemporary types as the Batracliia, but it is 
none the less universal. The kind of parallelism usually observed 
is that in which there is only a partial resemblance between adults 
of certain animals and the young of others. This has been termed 
"inexact parallelism," and the relation is presented by forms not 
very nearly phylogenetically related. The more remote the phylo- 
genetic lines of two types, the more '"inexact " will their parallel- 
ism be. It was once a question whether any parallelism can be 
traced between the members of the five or six primary divisions of 
animals, and in my essay on the " Origin of Genera," I was com- 
pelled to state that there was then ''no evidence of the community 


of origin of these divisions." Since tliat time, Haeckel has pub- 
lished liis " Gastraa Theory." This is a grand generalization 
from the facts of embryology, which shows the community in 
type of the early stages of all animals, and the similarity of the 
phases which they present during a part of their larval life. The 
exceptions to this law which have been 
observed will probably be explained, as 
have been those which have been urged 
against the law of homologies in anatomy. 

The paleontology of the Batracliia 
anura is largely unknown, so we must 
look elsewhere for proof of the truth of 
the fourth proposition, viz., that the suc- 
cessional relation in embryology corre- 
sponds with that shown by paleontology 
to have existed in geologic time. 

For this purpose I select one of the 
most complete series 
known to paleontology; 
that of the camels or 
CameUdcB, whose re- 
mains are found abund- 
antly in various parts 
of our country. The 
succession of the known 
genera is seen in the 
structure of the bones 
of the feet, and of the 
superior incisor and 
premolar teeth. The 
metatarsal and meta- 
carpal bones are or are 
not co-ossified into a 
cannon bone ; the first 
and second superior in- 
cisor teeth are present, 
rudimental or wanting, 
and the premolars num- 
ber from four to one. 
The relations which 
these conditions bear 

Fig. 11. 

Fig. 12. 

Fio. 11. — Poehrotheritim vilsoni carpus and meta- 
carpus with end of radius, three filUis natural size. 
OriLrinal ; from White Eiver Miocene of Colorado. 

Fm. 12. — Carpus and metacarpus of Procamelus 
ocridentalis, about two fifths natural size. Oritrinal ; 
from report of G. M. Wheeler, U. S. Expl. Surv. W. ot 
100th Mer., vol. iv, pt. ii. From New Mexico. 


Fip. 1. 

Fig. 33. 

Fig. 2. 

Fig. 3, wanting. 

Fig. 5. 

Fig. 6. 

Fig. 6. 

Fig. 7. 

Fig. 7, wanting. 


Fig. 1. 

Fig. 2. 

Fig. 1. 

Fig. 2. 

Fig. 3. 

Fig. 3 i. 

Fig. 31. 

Fig. 33. 



Fig. 32. 

Fig. 4. 

Fig. 33. 

Fig. 6. 

Fig. 6. 

Fig. 5. 



The numbers in each column correspond with the types of ossification mentioned 
in the text, and are the same as those in the table of families given in the same con- 
nection. The power numbers attached to Fig. 3, represent the degree of ossification 
of the nasal bones, except the ~^, which signifies unossified ethmoid. Most of the 
cuts are original. 

BuFONiD-E. — Fig. 2, anterior part of skull of Chelydohairachus gouldi Gray, from 
Australia. Fig. 3, do. of Schismaderma careris Smith, S. Africa. Fig. 6, top 
of head of Pellaphryne peltacephala D. and B., Cuba. Fig. 7, top of head of 
Oiaspis empusa Cope, Cuba. 

SdAPHioPiDJE AND Pelobatid.?;. — Fig. 2, diagram of top of cranium of Didocus 
calcaratus Micahelles, Spain. Fig. 5, skull of Seaphiopus holbrooki Harl., 
United States. Fig. 6, skull of Cidtripes provincialis, from France, after 

IIyud^. — Fig. 1, Thoropa miliaris Spix., Brazil. Fig. 2, II>/psihoas doumerci D. 
and B., Surinam. Fig. 2', Hypsiboas pundatus Schn., Brazil. Fig. 3^, i^cytopis 
vennlosus Daudin, Brazil. Fig. 6, Trachycephalus geographicus D. and B., 
Brazil, after Steindachner. 

Cystignathid^. — Fig. 1, Eusoplms nebidoxus Gir., Chili. Fig. 2, Borboroccetcs fas- 
maniensis Gthr., Tasmania. Fig. 3, Elosia nasits Licht., Brazil. Fig. 3^, Jly- 
lodcs oxyrhynchus D. and B., W. Indies. Fig. 4, Grypiscus umbrinus Cope, 
Brazil. Fig. 6, Calyptocephalus gayi D. and B., Chili. 

Ranid^. — Fig. 3~^ — Ranula chrysoprasina Cope, Costa Rica. Fig. 3, Jiana oxy- 
rhyncha Sund., S. Africa. Fig. 3', Rana clamata Baud., N. America. Fig. 8^, 
Rana agilis Thomas. Fig. 3^, Rana hexadactyla Less., India. Fig. 4, Poly- 
pedates quadrilincaius D. and B., Ceylon. 

to geologic time are displayed in the following table, commencing 
with the lowest horizon : 

No cannon bono-. Cannon bone present. 

Incisor teeth present. Incisors one and two wanting. 

4 premolars. 3 prem'rs. 2 prem's. 1 prem'r. 


Lower Miocene. ■] Poebrotherium. 


Pliocene and Recent. \ ' a i ■ 

I Auchenia. 

This table shows that geological time has witnessed, in the his- 
tory of the CamelidcB, the consolidation of the bones of the feet 
and a great reduction in the numbers of the incisor and premolar 
teeth. The embryonic history of these parts is as follows : In the 


foetal state all the Ruminantia (to wliich the camels belong) have 
the cannon bones divided as in Poehrotheriiim ; they exhibit also 
incisor teeth, as in that genus and Protolahis. Very young recent 

Fig. 13. — Protolahis transmontanus Cope, skull, a, in profile ; J, from below, one 
third (linear) natural size. Original; from vol. iv, Report U. S. Geol. Surv., under 
F. V. Hayden. Ticholeptus bed of Oregon. 

camels have the additional premolar of PUmicJienia. They shed 
this tooth at an early period, but very rarely a camel is found 
in which the tooth persists. The anterior premolar of the normal 

Fig. 14. — Procamelns occidentalis Leidy, profile of skull, about two sevenths natu- 
ral size. Original ; from report of Capt. G. M. Wheeler, U. S. Geol. Geog. Surv. W. 
of 100th Mer. Vol. iv, pt. ii. From Loup Fork bed of New Mexico. 

Camelus is in like manner found in the young lama (AucJienia), 
but is shed long before the animal attains maturity. I may add 
that in some species of Procamelus caducous scales of enamel 


and dentine in shallow cayities represent the incisive dentition of 

It remains to show that characters of the kind above men- 
tioned are sometimes inconstant : that they may or may not ap- 
pear in individuals of a species. Under such circumstances it is 
evident that their origin does not imply any break in the line of 

First, as to a family character. It is well known that the deer 
differ from the giraffes in the presence of a burr or ring of osseous 
excrescences surrounding the base of the horn. Now, in the ex- 
tinct tertiary genus Cosoryx there are three species which possess 
or lack this burr indifferently. Why some individuals should, 
and others should not possess it, is not known.* 

Second, as to a generic character. The genus Cams (dog) is 
defined by the presence of two tubercular molars in the inferior 
series. The allied genus Thous possesses three such teeth, while 
Icticyon has but one. Now examples of Canis familiar is (domes- 
tic dog) with but one tubercular molar are not rare, while an in- 
dividual with three is occasionally found. 

To take another case. The normal dentition of Homo (man) 
is, on each side, incisors, 2 ; canine, 1 ; premolars, 2 ; molars, 3, 
It is very common to find in the higher races, individuals who 
have molars only two in one or both jaws ; and the absence of 
the external incisors of the upper jaw is almost as frequently met 
with. Here we have two new generic variations in one and the 
same species. 

In specific characters variations are most familiar. Thus, the 
young of deer are generally spotted, and the adults are nearly 
uniform in coloration. Some deer (as the Axis) retain the spotted 
coloration throughout life, while an occasional spotted individual 
of unicolor species is a violation of specific character by a failure 
to develop. The larvae of some salamanders are of uniform col- 
oration, and the adults spotted. The unicolor adults of the same 
species, not uncommonly met with, present examples of the same 
kind of variation. 

Any biologist can select hundreds of similar cases from his 
special department of study. 

* The explanation I have offered is that the horn was stripped of its integuments 
to the position of the burr by the animals in fighting. The condition of the speci- 
mens renders this hypothesis probable. Sec "Report U. S. Expl. Surv. W. 100th 
Mer.," Capt. G. M. Wheeler, vol. iv, pt. ii. 



Having reviewed the reasons why the doctrine of evolution 
should be received as truth, I desire to give attention to the laws 
which may be made out by reference to its phenomena. Progress 
in this direction is difficult, owing to the natural impediments in 
the way of studying the history of the growth of living beings. 
We will, however, commence by examining more fully the phe- 
nomena with which we have to deal. 

It is well understood that the world of animal life is a nicely 
adjusted equilibrium, maintained between each individual and its 
environment. This environment exerts forces both purely physi- 
cal, and those exercised by other animals. Animals antagonize 
each other in procuring food, whether that food consist of vegeta- 
tion or of other animals, but in the latter case the conflict is more 
severe. A similar competition exists among male animals in the 
matter of reproduction. These exhibitions of energy constitute 
the struggle for existence, which is the daily business of the living 
world. It is well understood that in this struggle the individuals 
best provided with means of self-preservation necessarily survive, 
while the weak in resources must disappear from the scene. 
Hence those which survive must display some especial fitness for 
existence under the circumstances of their environment, whatever 
they may be. So the ''survival of the fittest" is believed to be a 
law of evolution, and the process by which it is brought about has 
been termed "natural selection." The works of Darwin and 
others have satisfied biologists that this is a ve^^a causa. 

Before the excellence of a machine can be tested, it must exist, 
and before man or nature selects the best, there must be at least 
two to choose from as alternatives. Furthermore, it is exceedingly 
improbable that the nicely adapted machinery of animals should 
have come into existence without the operation of causes leading 
directly to that end. The doctrines of "selection" and "sur- 
vival" plainly do not rfeach the kernel of evolution, which is, as I 
have long since pointed out, the question of " the origin of the 
fittest." The omission of this problem from the discussion of 
evolution, is to leave Hamlet out of the play to which he has 
given the name. The law by which structures originate is one 
thing ; those by which they are restricted, directed, or destroyed, 
is another thing. 

There are two kinds of evolution, progressive and retrogres- 


siye ; or, to use expressions more free from objection, by addition 
of parts, and by subtraction of parts. It is further evident that 
that animal which adds something to its structure which its par- 
ents did not possess, has grown more than they ; while that 
which does not attain to all the characteristics of its ancestors has 
grown less than they. To express the change in the growth-his- 
tory which constitutes the beginning of evolution, I have employed 
the terms "acceleration and retardation." Generally these ex- 
pressions are literally exact, i. e., there is an increased rate of 
growth in evolution by addition, and a decreased rate in evolution 
by subtraction ; but this is not always the case, for some divisions 
of animals have increased the length of their growth-period with- 
out reference to evolution in structure. The terms express the 
phenomena figuratively, where not exact in the sense of time, and 
I believe they are sufficiently clear. The origin of the fittest is 
then a result of either acceleration or retardation. It is easy to 
perceive that a character which makes its appearance in a parent 
before or near to the breeding season is likely to be transmitted to 
its descendants ; so also a character which is lost near this time is 
likely to be wanting from the offspring. The causes of accelera- 
tion and retardation may next claim attention. 

It is well known that the decomposition of the nutritive fluids 
within living animals gives rise, in the appropriate tissues, to 
exhibitions of different kinds of forces. These are, motion in all 
classes ; heat in some only ; in a still smaller number, electricity 
and light ; in all, at certain times, growth-force or bathmism ; in 
many, phrenism or mental or thought-force. These are all derived 
from equivalent amounts of chemical force which are liberated by 
the dissolution of protoplasm. This organic substance, consisting 
of CHON, undergoes retrograde metamorphosis, being resolved 
into the simpler CO2, HO, etc., and necessarily liberates force. in 
the process. None of the functions of animal life can be main- 
tained without supplies of protoplasm. We have here to do with 
bathmism. It consists of the movement of material to, and its 
deposition in, certain definite portions of the growing egg, or 
foetus, as the case may be. It is different in its movements in 
every species, and its direction is probably the resultant of a num- 
ber of opposing strains. In the simplest animals its polar equili- 
brium is little disturbed, for these creatures consist of nearly 
globular masses of cells. As we ascend the scale a greater and 
more marked interference becomes apparent ; radiated animals 


display energy in a number of radiating lines rather than in the 
spaces between them ; and in longitudinal animals, a longitudinal 
axis exceeds all others in extent and importance. In the highest 
animals its results are much more evident at one extremity of the 
axis (head) than at the other, and the diverging lines are reduced 
to four (the limbs). In each species the movements of this force 
are uniform and habitual, and it is evident that the habit is so 
deeply seated that only a very strong dynamic interference can 
modify or divert it. The interfering forces are probably all those 
transmissible through living tissue, and especially molar force. 
Thus every species has its own specific kind of bathmic force. 

The characters of living beings are either adaptive or non- 
adaptive ; they are either machines especially fitted to meet the 
peculiarities of their environment, or they are not. Among the 
latter may be ranged rudimental structures and also many others 
of no sufficient use. They are all due either to excess or defect of 
growth-force ; they are either consequences of a removal of nutri- 
tive material to other portions of the body ; or they are due to an 
excess of such material which renders an organ or part useless 
through disproportionate size. Of the former class may be cited 
the absence of the tail in some monkeys and birds ; also of the 
teeth in some Cetaceans ; of the latter kind are the enormous 
tusks of the mammoth and the recurved superior canines of the 
babyrussa. The change of destination of this material has been 
probably due to the construction of adaptive machines whose per- 
fection from time to time has required the use of larger and larger 
proportions of force and material. 

In considering the origin of adaptive structures, two alterna- 
tive propositions are presented to us. Did the occasion for its use 
follow the appearance of the structure, or did the need for the 
structure precede its appearance ? Tbe following answer to the 
question has always been the most intelligible to me. Animals 
and plants are dependent for existence on their environment. It 
is an every-day experience that changes in environment occur 
without any preparation for them on the part of living things. If 
the changes are very great, death is the result. It is evident that 
the influence of environment is brought to bear on life as it is, or 
has been, and that special adaptations to it on their part must fol- 
low, not precede, changes of climate, topography, population, etc. 
We have another important consideration to add to this one, viz., 
the well-known influence of use, i. e., motion, on nutrition. Ex- 


ercise of an organ determines nutritive material to it, and tlie 
nervous or other influence which does this, equally determines 
nutritive material to localities in the body to which an effort to 
move is directed, whether an executive organ exist there or not. 
The habit of effort or use determining the nutritive habit must be 
inherited, and result in the growing young, in additional struct- 
ure. Change of structure, denied to the adult on account of its 
fixity, will be realized in the growing or plastic condition of foetal 
or infant life. The two considerations here brought forward lead 
me to think that the cause of acceleration, in many adaptive 
structures, is environment alone, or environment producing move- 
ments, which in turn modify structure. The character of the 
stimulus in the successive grades of life may be expressed by the 
following table, passing from the lowest to the highest : 

1. Passive or motionless beings : 

by climate and food only. 

2. Movable beings : 

by climate, food and motion. 
By motion either : 
a, unconscious, or * 
aa, conscious, which is, 
h, reflex, or 
lib, directed by desire without ratiocination, or 
libb, by desire directed by reason. 

The only general rules as to the direct influence of motion on 
structure which can be laid down at present are two, viz., That 
density of tissue is in direct ratio to pressure, up to a certain 
point ; f and that excess of growth-force, in a limited space, pro- 
duces complications of the surfaces stimulated. J These and other 
laws, yet unknown, have probably led the changes expressed by 
evolution, while many others have followed the disturbance of 
equilibrium which they have produced. 

I here allude incidentally to the question of transmission or 
inheritance. It has been maintained above that the bathmic force 
of each species is different from that of all other species. This 
force is characteristic of some unit of organization of living be- 

* Movements coming under this bead are often called reflex. 
f See "Penn. Monthly," 1872; this work Art. I. 
X " Method of Creation," Philadelphia, 1871. 


fngs ; and this probably consists of several molecules. This nnit 
has been termed, by Haeckel, the plastidule. The transmission 
of the bathmic force of one generation to another would be effected 
by the transmission of one or more living plastidules ; and this is 
probably precisely what is accomplished in reproduction. The 
Dynamic Theory of reproduction I proposed in 1871,* and it has 
been since adopted by Haeckel under the name of perigenesis. I 
compared the transmission of bathmic force to that of the phe- 
nomenon of combustion, which is a force conversion transmitted 
from substance to substance by contact. The recent observations 
of Hertwig, Biitschli and others, confirm this view. The theory 
of pangenesis, devised to explain the phenomenon of reproduction, 
is to my mind quite inadequate. 


I enter here upon a wide field, over which I can only skim on 
an occasion like the present. The subject has been already intro- 
duced by reference to consciousness as modifying movement ; of 
course, then, if movement modify structure, the latter is influenced 
by consciousness. The word consciousness was then, and is now, 
used in its simplest sense, viz. : as synonymous with physical 
sensibility. Its lowest and most usual exhibition is the sense 
of touch ; the special senses, taste, sight, etc., are higher forms, 
while thoughts and desires are organized products of the same raw 
material. Consciousness can not be denied to many of the inferior 
animals ; indeed, if we grant it to any, we must admit that it is 
displayed at times by even the lowest Protozoon. That these 
humble creatures should possess it, is apparently quite as proba- 
ble as that the very similar bioplasts of the brain of man should 
be its seat. 

Consciousness alone is not a sufficient basis for the develop- 
ment of mind. For this, one more element is necessary, and that 
is, memory. Impressions made by the environment are registered, 
and soon cease to be present in consciousness. Under the influ- 
ence of association the impressions return to consciousness. Asso- 
ciations are those of place, of the order of time, and of similarity 
or difference in various qualities, as size, color, or any other physi- 
cal features. Experiences of these qualities are to all conscious 
beings either painful, indifferent, or pleasurable. When associa- 

* " Method of Creation," 1871. 


tion requires, events, objects, or characteristics, are returned to 
consciousness in the order in which they cohere most firmly in 
the mind, which may or may not be that in which they entered it. 
The liking for or dislike to the object, are equivalent to an attrac- 
tion to or repulsion from it. Thus experience is begotten : as its 
material increases, new combinations are formed, new relations 
observed, and in the highest types of mind, laws are discovered. 
No one can deny memory to animals ; it is the medium of their 
education by man, and has been as well the means of their edu- 
cation by nature. Impressions cause a re-arrangement of cer- 
tain elements of structure which give the form to consciousness 
when it arises again. It is also probable that these arrangements 
are not the same as those which represent classifications and con- 
clusions, but that nevertheless the arrangement or organization 
of these is determined by the simpler arrangements caused by 
perceptive stimuli. Experience produces these combinations in 
the bioplastic aggregations of all animals, be they in the form of 
ganglia, brains, or less specialized forms. Nowhere in the human 
organism are the effects of effort and use so strikingly witnessed 
as in the increase of brain power ; and familiarity with the educa- 
tion of the lower animals shows that this is the case with them 
also, though in a lesser degree than in man. 

If, then, we grant the propositions, first, that effort and use 
modify structure ; and second, that effort and use are determined 
by mind in direct ratio to its development, we are led to the con- 
clusion that evolution is an outgrowth of mind, and that mind is- 
the parent of the forms of living nature. This is, however, to 
reverse a very usual evolutionary hypothesis, viz. : that mind is 
the product and highest development of the universe of matter 
and force. The contradiction is, however, not so absolute as at 
first appears. By mind, as the author of the organic world, I 
mean only the two elements, consciousness and memory. But it 
is the view of some thinkers that consciousness is a product ; that 
it is not only a correlative of force, but a kind of force. To the 
latter theory I can not subscribe ; when it becomes possible to 
metamorphose music into potatoes, mathematics into mountains, 
and natural history into brown paper, then we can identify 
consciousness with force. The nature of consciousness is such 
as to distinguish it from all other thinkable things, and it 
must be ranged with matter and force as the third element of the 


It is true that unconsciousness does not imply absence of life 
as generally understood. A majority of the processes of life are 
performed unconsciously by living creatures ; mind itself being 
no exception to this rule. There is another class of acts whose 
performance produces sensation, but consciousness is not con- 
cerned in them as an immediate cause. Therefore, it is a com- 
mon endeavor to associate reflex and unconscious acts Avith the 
molecular movements of inorganic and non-living substances. 
But the one great difficulty in making this identification has 
never been surmounted. This is the different nature of the 
movements in the two cases. In non-living matter they are sim- 
ply polar, nothing more. In living beings they display design. 
Perhaps I use the word "design " in a new sense, but the expres- 
sion is nevertheless appropriate. "What I mean is, that the move- 
ments of li\nng things have direct reference to consciousness, to 
the satisfaction of pleasures, and to the avoidance of pains. The 
molecular movements within animals of the simplest class are the 
digestion of food and the elaboration of the materials of repro- 
duction. The molar movements of the simplest animals are to 
enable them to escape the pains of hunger and celibacy. More- 
over there is reason why the movements of living beings display 
design. AYe all know the nature of habits ; how they are per- 
formed unconsciously, and as automatically as digestion itself. 
But did any one ever know of a habit in an animal, whose origin 
he could trace, which has been formed in unconsciousness ? Ac- 
cording to our knowledge, habits are always the result of stimuli 
which are consciously felt, and which cause by repetition or 
through reminiscence a repetition of the resulting movement. 
After a sufficient number of repetitions such an act becomes a 
habit, i. e., is performed automatically, or without the interven- 
tion of effort, and frequently without consciousness. It thus be- 
comes a part of the character of the individual or species. This 
common jiJienomenon is explained by the hy]3othesis that an or- 
ganization of the centers controlling action is caused by the efforts 
of the animal under the stimulus, and that finally a machine is 
constructed which determines the nature of the force expended, 
without further mental exertion of the individual. Such a pro- 
cess is education, and the result is an addition to the stock of 
faculties already on hand. Thus is explained the vast number of 
automatic and unconscious activities displayed by animals ; to the 
same source, I believe, the common reflex acts may be traced ; it 


even appears to me probable that the organic fnnctions in general 
have had the same origin.* While these latter have mostly long 
since passed beyond the control of the mind, portions of the uro- 
genital functions still linger within the confines of its jurisdiction. 
Thus have consciousness and mind endowed living nature with 
useful functions ; and this, which may be called the Theory of 
Endoiument, accounts for the element of design which is so j)uz- 
zling when seen in unconscious and reflex acts. 

As it has been maintained above, that structure is the effect of 
the control over matter exercised by mind, it is evident that the 
evolution of mind must be directly followed by corresponding de- 
velopment of organism. The science of paleontology substantiates 
this theory in a wonderful manner. But the animal mind being 
generally occupied with simple functions, its expressions in struct- 
ure are usually nothing more than the progressive creation of im- 
proved instruments for obtaining food, resisting climate, escaping 
enemies, and reproducing their kind. The struggles of animals 
have been seen on this platform, and mind has only been necessary 
to aid in accomplishing the ends above mentioned. "Wonderfully 
effective machines for grinding, cutting, seizing, and digging ; for 
running, swimming, and flying have been produced. The develop- 
ment of mind proper must appear in the size and structure of the 
brain ; and though the history of the latter in past ages must 
always remain, in large part, hidden from us, it is known that in 
the former respect there has been great progress made in various 
lines of animals. Now the line which has carried brain to its pres- 
ent development in man, the Quadrumana, has been deficient in 
special mechanical excellencies of the kind enumerated above. 
Perhaps primitive inferiority in these many respects has kept the 
Quadrumana under greater mental tension, and compelled them 
to exercise caution in their acts, and give that opportunity to 
thought which was less demanded in the case of other animals. 
Furthermore, if they are less specialized in their mechanism than 
most other Mammalia, they are less restricted by it to peculiar 
modes of life. They are more versatile, and more capable of the 
adoption of new habits as a consequence. And here we have a 
glimpse of a most important principle in evolution, which is the 
keynote to its method ; this is what I have called the The Doctrine 
of the Unspecialized. 

* " Consciousness in Evolution." " Penn Monthly," 1875. 


Paleontology shows that the succession of living types has not 
been in a single straight line. It has been in many divergent lines, 
and a large number of them have not continued to the present 
time. The history of life has been well compared to a tree with 
divergent branches, many of which do not reach the elevation of 
the summit. Furthermore, in the many cases in which we can 
trace the lower lines to the present period, it is evident that in 
their present condition they could not have given rise to the higher 
forms. Each line, in fact, has developed to an extreme of spe- 
cialization of structure, which it would seem is incapable of modifi- 
cation in any direction very divergent from that which it has al- 
ready taken. Much less have such specialized tyjies been able to 
survive the environment for which they were designed ; with im- 
portant changes in that respect they have perished. A few exam- 
ples will serve to illustrate my meaning. The direction of develop- 
ment has been from fishes, through Batrachia and reptiles, to birds 
and mammals. But we can not derive any living type from the 
osseous fishes of the present or past ages (Teleostomi) : to find the 
origin of Batrachia, we must pass below these to more generalized 
and older forms, the Dipnoi, a class whose position in the system 
was for years a controverted point. We can not obtain Maminalia 
from any of the existing types of reptiles, but we must go back to 
the Permian period, and trace their outlines in the Theromorplia 
of that day. In spite of the prophetic resemblance of these 
remarkable animals, they are inferior to later Reptilia in the 
structure of their vertebral column, and display resemblance to 
some of their immature stages, as well as to those of the Mammalia. 
Among mammals we can not derive monkeys from Carnivora or 
Ungulata, nor the latter from each other, but can only trace their 
close approximation in the Bunotherian types of the Lower Eocene. 
So with the great divisions of Ungulata ; Proboscidians, Hyrax, 
and the even- and odd-toed orders must all be traced to the un- 
specialized Amblypoda, with small brains and five-toed plantigrade 
feet, as their ancestors.* It is easy to perceive that the generali- 
zation and plasticity of all these forms has furnished the ground 
of their ancestral relation. 

We are now in a position to comprehend more clearly the 
general nature of evolution. The doctrine of the unspecialized 

* Sec the origin of types of Mammalia cducabilia, " Journal Academy," Philadel- 
phia, 1874. 


teaches that the perfection produced by each successive age has 
not been the source or parent of future perfection. The types 
which have displayed the most specialized mechanism have either 
l^assed away, or, undergoing no change, have witnessed the prog- 
ress and ultimate supremacy of those which were once their infe- 
riors. This is largely true of animals which have attained great 
bulk. Like those with perfected weapons, they have ever been 
superior to the attacks of other animals in their day, and doubt- 
less led, so long as food abounded, lives of luxurious indolence. 
With change or diminution of food, such huge beasts would be 
the first to succumb, and it is a fact that no type of land animals 
has maintained great size through many geologic changes. It is 
true that all of the lines of ancestry of the existing higher Mam- 
malia, as the subdivisions of the Carnivora, Ungulata, and Quad- 
rumana, which we know in detail, commenced with types of 
small size and correspondingly little muscular power. 

Some important conclusions may be derived from what has 
preceded. It seems that evolution has witnessed a continual run- 
ning down of types to their great specialization or extinction. 
That many types have arisen in weak and small beginnings, but 
that the conflict with more powerful forms has developed some 
qualities in which they sooner or later excelled, and which formed 
the basis of their future superiority and persistence. That while 
this has probably been the true cause of the origin of the many 
admirable mechanical adaptations displayed by animals, it is pre- 
eminently true of the development of mind. That the reason 
why progress has reached its limit in the lines of greatest speciali- 
zation, has probably been the removal of the occasion of its origi- 
nal cause, i. e., active exercise in the struggle for existence. This 
explanation is suggested by the remarkable degradation which is 
witnessed in animals whose mode of life relieves them from the 
necessity of working for a livelihood, e. g., the parasites and ses- 
sile animals whose young are free. Some of these creatures, on 
assuming their parasitic life, lose the semblance of even the order 
to which their young belong. The j^rimary stages of various 
plants move actively through the water like the lowest forms of 
animals, and their sessile adult condition must be looked upon as 
a degeneration. It is well known that the endeavor to relegate 
the lowest forms of life to the two kingdoms of animal and vege- 
table, has been generally abandoned. The great vegetable king- 
dom probably exhibits a life degraded from more animal-like be- 


ginnings. Animal irritability and mobility have been lost, and 
their own consciousness must be entirely eliminated from the 
question of the origin of the many later and specialized types of 
plants. But I venture here the hypothesis that the consciousness 
of plant-using animals, as insects, has played a most important 
part in modifying the structure of the organs of fructification in 
the vegetable kingdom.* Certain it is that insects have been 
effective agents in the jjreservation of certain forms of plants. I 
would suggest whether the mutilations and strains they have for 
long periods inflicted on the flowering organs, may not, as in some 
similar cases in the animal kingdom, have originaied peculiarities 
of structure. 

Evolution of living types is then a succession of elevations of 
platforms on which succeeding ones have built. The history of 
one horizon of life is, that its own completion but prepares the 
way of a higher one, furnishing the latter with conditions of a 
still further develojiment. Thus the vegetable kingdom died, so 
to speak, that the animal kingdom might live ; having descended 
from an animal stage to subserve the function of food for animals. 
The successive types of animals have first stimulated the develop- 
ment of the most susceptible to the conflict of the struggle for 
existence, and afterward furnished them with food. Doubtless, 
in the occupation of the world's fields, the easiest and nearest 
at hand have been first occupied, and successively those Avhich 
were more difficult. The digging animals are generally those 
which first abandoned the open field to more courageous or 
stronger rivals ; and they remain to this day generally of low tj'pe 
compared with others of their classes (e. g., Monotremata, Roden- 
tia, Insectivora). All occupations have been filled before that one 
which requires the greatest expenditure of energy, i. e. , mental 
activity. But all other modes of life have fallen short of this one 
in giving the supremacy over nature. 

Automatism then represents a condition of ''lapsed intelli- 
gence" and diminished life. The unconscious automatism of 
animals is a condition of still greater lapse. On the contrary, 
sensibility is the condition of development, and the susceptibility 
and impressibility which is the extreme reverse of automatism is 
the especial character of youth. Here the "doctrine of the un- 
s}>ecialized " finds Justification again. 

* This opinion has also been expressed by Ilcrniann Miillcr. 


What the future has in store for us in the history of inorganic 
force and its results we can not now foresee, but I call attention 
in this connection to the important part played by life in the dis- 
tribution of minerals. It has long been known that the carbon of 
the earth's crust was once in a living state, and it is admitted that 
the limestone once circulated in the fluids of animals. We have 
recently been compelled to believe that siliceous rocks are com- 
posed of the consolidated shells of minute plants, which they have 
elaborated from the water of the ocean. Silver and gold are seg- 
regated and deposited by seaweeds. The principal rock material, 
whose relation to life has not been ascertained, is alumina. How 
far the processes which now characterize dead matter were once 
related to life is a problem for the future. 


The doctrines of the struggle for existence and survival of the 
fit in human life have a two-fold application. The relative pro- 
portions in which these applications are made will depend on tlie 
moral development of him who makes them. Moral density and 
intellectual stupidity (often nearly allied) will see in these two 
laws only the struggle for material power, and the survival of tlie 
strongest. They will hardly urge in these days, as they would 
infallibly have done had they lived a few centuries ago, that the 
strongest means the hardest hitter, or the most successful assassin, 
but they will probably believe that this pre-eminent position be- 
longs to the most wealthy. From a purely dynamical standpoint 
this position is correct, yet it might be a useful question for such 
advocates to consider why it is that physical oj)pression and assas- 
sination should be less successful avenues to power than they once 

There are two reasons why man does not grant the first place 
in his esteem to physical force. The first principles of morals are 
acquired in the struggle for existence. The idea of meum and 
fuu7n was speedily developed so soon as men associated together ; 
and the habit of justice has doubtless been formed by the insist- 
ence of every man on his own rights, and by the power of combi- 
nations of men to control those who may from superior strength 
or other cause seek to violate the rights of property. Thus law 
originated, and from the earliest history of the race to the present 
day it has educated the barbarous and semi-barbarous to civiliza- 
tion. It is then easy to perceive that man gives the highest place 


iu his affections to the most just ; but there is yet another reason 
why this should be the case. 

The reproductive instinct in the lower animals has developed 
into social affections, and these form a part of the character of 
the higher animals and, in an especial degree, of man. The senti- 
ments of sympathy and benevolence are probably outgrowths of 
the same. AVhile the rational faculties are concerned in the 
knowledge of right, these sentiments are a source of the love of 
right. This disposition is trusted by men as leading to i\iQ prac- 
tice of right, in cases where the power to enforce it is not immedi- 
ately present. The struggle for existence then among men ranges 
all the way from a rivalry of physical force to a rivalry for the 
possession of human esteem and affection. The robber and assas- 
sin of the lowest human races are represented by the slanderer and 
defamer in the higher. The ultimate prosperity of the just, as- 
serted and foretold by prophets and poets, is but a forecast of the 
doctrine of the survival of the fittest. The unjust are sooner or 
later eliminated by men from their society, either by death, seclu- 
sion, or ostracism. 

But the organized moral qualities can not normally transcend 
in power, as motives of human action, those which secure man's 
physical preservation. Lines of men in whom the sympathetic and 
generous qualities predominate over the self-preservative, must 
inevitably become extinct. Evolution can produce no higher de- 
velopment of the race (whatever may sometimes appear in indi- 
viduals) than an equivalency in these two classes of forces. Be- 
yond this the organization of the social faculties of the brain must 
always be repressed in the race, so that we can only expect to 
attain an equilibrium between them and the more purely selfish 
ones, as the very highest result of unassisted evolution. In this 
position the judgment is suspended between the opposing classes 
of motives ; and it must ever remain doubtful in general as to 
whether resulting action will be just and right, or the reverse. I 
exclude from this question those generous acts which do not appear 
to the actor to conflict with self-interest. These may be termed 
sympathetic acts, and are quite distinct from the altruistic* The 
sympathetic actions are seen at times in most animals. The al- 
truistic acts, on the other hand, are those that express what is usu- 
ally called ''moral principles." Such acts may often coincide 

* "On the Origin of the Will." "Pcnn Monthly," 1877. 


with the interest of the actor, but so long as they do not appear 
to him to do so, they are altruistic. It is part of the doctrine of 
evolution that habits will ultimately disappear on the removal of 
their stimulating cause. The moral nature originated, and has 
been maintained, through the pressure of the fear of consequences. 
The removal of this pressure, through the acquisition of power, 
would then ultimately result in the diminution or loss of the moral 
nature, through disuse. The abuses of power are well known. 
This appears to be all that evolution can do for us in the produc- 
tion of the moral nature. So it would appear that no organized 
faculty of self-sufficient altruistic justice can be derived by the 
process of mental evolution. The result is rather a continued 
struggle between justice and injustice. It is, then, evident that 
any power which shall cause the permanent predominance of the 
just over the selfish faculties must be derived from without. 

After we omit from customary religion, cosmogony, which be- 
longs to science, and theogony, which belongs to the imagination, 
we have left an art which has for its object the development and 
sustentation of good works or morals among men. If the teachers 
and professors of this art produce the results in this direction at 
which they aim, their great utility must be conceded by all. Their 
method has the advantage over that of the law, in being of the 
character of inducements supplied before action, instead of pains 
and penalties inflicted after action. They strive to originate good 
conduct, rather than to punish bad conduct. They are working 
ou the side of the originative force in development, rather than 
the destructive ; the "origin of tlie fittest,'''' rather than the "sur- 
vival of the fittest." Whether man possesses the spontaneous power 
called *'free will" or not, the work of supplying inducements for 
good conduct is most useful to society. But religion, as generally 
understood, pre-supposes free will ; and the definition of the word 
responsibility implies its existence. The question as to the pres- 
ence of such a faculty is an interesting one, and will now be briefly 

The well-known doctrine of necessity leaves no place for free 
will. All acts are the consequences of motives, and are the out- 
come of a balancing of interests. The heaviest side of the account 
determines action. Our physical necessities supply the motives 
for most of our activities ; our pursuit of food and clothing is of 
necessity, and no condition is free from it. Evolution supports 
and explains this doctrine, as can readily be perceived. It de- 


rives our instincts from an ancestry whose daily occupation has 
been their gratification. But it has been shown above that this 
development does not supply the motives of an independent 

The direction of action under stimulus is determined by intel- 
ligence, which is, as has been above maintained, the product of 
experience. Intelligence is organized or classified knowledge, and 
directs the activities set on foot by the likes and dislikes, that is, 
the affections. When there is hiioivledge, tliere is no necessity for 
spontcmeous action or free will, since action is determined by the 
organization of the mind. Even if the mind is conscious of insuf- 
ficient knowledge, an inducement to seek knowledge is supplied, 
and according to the result of investigation will be the direction 
of knowledge. 

But we are here brought to face the case where knowledge can 
not be or is not obtained. This is the condition of the two ques- 
tions of the practice of morals, and the nature of the future life. 
The evolution of mind consists of a continual advance from the 
known into the unknown, and a transfer of the unknown to the 
known. So long as there is any inducement to progress of this 
kind, and nature responds to inquiry, development will go on. Al- 
though it is true that it is only among men, and but few men at 
that, that the pursuit of knowledge is an occupation, most men 
add to their stock incidentally as they pursue other avocations. 
The knowledge of right and the inducements to its practice are 
learned in their every-day intercourse, so far as it can be acquired. 
But knowledge in these directions soon attains its limit, and ac- 
cordingly, development dependent on knowledge must cease. If 
any further progress in practical morals is to be made, some new 
force must intervene at this point. 

Here is the opportunity for the appearance of will or sponta- 
neity ; here it is at least needed. I am willing to believe that it 
may appear at this point, and that so long as we have to face the 
unknown in moral progress, so long it will remain. As a force 
it must be equivalent of other forces, but as a form of conscious- 
ness it is a new element of mind. As represented in new molecu- 
lar organization, it may always continue, even after much of the 
unknown may have been conquered, and a stationary period may 
have ensued. Such an accession to character would be a fitting 

* " On the Origin of the Will." " Penn Monthly," \B,11. 


crown of eyolution, and a justification of this labor of the ages. 
If a true factor in human development, it might be compared, in 
the creation of character, to the apical bud of a growing tree. As 
the jDart pre-eminently living, it leads the growth of the trunk and 
branches. They all follow of necessity the path it has marked out. 
Under its lead they are successively formed, become fixed, and 
finally decay. 







It has been already stated* tliat the transition from simple to 
complex teeth is accomplished by repetition of the type of the 
former in different directions. "In the cetaceans this occurs in 
the Squalodonts ; the cylindric incisors are followed by flattened 
ones, then by others grooved in the fang, and then by two-rooted, 
but never by double-crowned teeth. This is the result of antero- 
posterior repetitive acceleration of the simple cylindric dental type 
of the ordinary toothed cetacean. Another mode of dental com- 
plication is by lateral repetition. Thus the internal heel of the 
superior sectorial tooth of a carnivore is supported by a fang 
alongside of the usual posterior support of a premolar, and is the 
result of a repetitive effort of growth-force in a transverse direc- 
tion. More complex teeth, as the tubercular molars, merely ex- 
hibit an additional lateral repetition, and sometimes additional 
longitudinal ones. As is well known, the four tubercles of the 
human molar commence as similar separated knobs on the [primi- 
tive] dental papilla." 

Accordingly, the simple tubercle may be regarded as the least 
specialized form of tooth. It may be low and obtuse, as in the 
Chiromt/s, or the walrus ; more elevated and conic, as in the dol- 

* "Method of Creation," p. 10. Philadelphia, 187L 


pliins ; or truncate, as in sloths and some rodents. The form is 
complicated in" two ways, viz., either by the folding of the sides, 
as in Glyptodon and many rodents, as Arvicola, Castor, Lepus, 
etc. ; or by the develoi)ment of tubercles on the crown, as in Mus, 
Dicotyles, Homb, etc. Upon this basis are constructed the more 
complex types of teeth exhibited by the various families of Ungu- 
lata and some Eodetitia. as has been pointed out in the following 
language : " The genus Uintatherium* has been shown to be a Pro- 
boscidian, which combines some important features of the Peris- 
sodadyla with those of its own order. . . . The number of such 
characters was shown to be somewhat increased in Batlimodon, 
which therefore stands still nearer to the common point of de- 
parture of the two orders. This point is to be found in types still 
nearer the clawed orders ( TJnguiculatd) in the number of their 
digits (4, 5), and in which the transverse and longitudinal crests 
of the molar teeth are broken up into tubercles more or less con- 
nected, either type of dentition [i. e.. Proboscidian or Perissodac- 
tyle] being derived according as such tubercles are expanded in 
the transverse or longitudinal directions." f 

As is well known, the crowns of the superior molar teeth of 
the higher Mammalia are supported on three roots, two of which 
are external, and the third internal. The corresponding inferior 
molars are supported on two roots, and are therefore, in so far, less 
complex. But these two roots usually support four tubercles, two 
to each, while the roots of the superior molars support directly 
but one each. Hence, as Prof. Harrison Allen remarks, the 
crown of the inferior molar is more complex than that of the su- 
perior. \ 

In tracing the degrees of complication of the crowns of the 
superior molars of Mammalia from the simple cone of the Ceta- 
cean, the first step is seen in the Squalodon and teeth of similar 
chai'acter. In these there are two roots, antero-posteriorly related. 
In the Squalodont Portheodon gervaisii {Squalodon Auct.) the 
third root is present. In Mammalia with but three tubercles in 
the crown, e. g., Carnivora, the inner root has much the form of 
one of the external ones. In many of those with four tubercles 
of the crown, e. g., Quadrumana, the form of the internal root is 

* Eobasileus in the original. (Ed. 1886.) 

f " On the Primitive Types of Mammalia Educabilia," published by E. D. Cope, 
May 6, 18*73. " Pi'Oceeding.g of the American Philosophical Society," 18Y3, p. 224. 
X "Dental Cosmos," December, 1874. 


not modified ; but in the Lophodont types it is materially altered. 
In Hyracodon, Rhinocerus, Anchiiherium, Oreodon, Cervus, and 
others, it is flattened, with the long diameter anteroposterior, and 
is grooved on the inner face, so as to assume the form, as it does 
the function, of two roots conjoined. In the temporary dentition 
of Sus, Merychyus, etc., the inner root is divided, so that the 
superior molar has four distinct roots. 

The proper homologizing of the various forms of dental struct- 
ure of the Ungulates with each other, and with the primitive 
types of tubercular teeth, is entirely essential to their intelligent 
classification, and therefore comprehension of their mode of origin. 
In order to lay a foundation for this work, I define the four types 
as follows, giving the subdivisions of the first two in brief, and 
discussing those of the third and fourth more fully afterward : 
Division I. Haplodont type ; the crown undivided or simple. 
a. Crown low, obtuse; Cetacea {Be- 
luga), Carnivora (Rosmarus). 
h. Crown elevated, acute ; Cetacea 
{Delpliinus) ; canine teeth in 
c. Crown truncate ; Edentata {Bra- 
dypus) ; Rodentia ( Geomys, 
Division II. Ptycliodont type ; the crown folded on the sides ; 
the folds frequently crossing the crown. 
a. Sides only folded ; Rodentia 
{Arvicola Castor) ; Edentata 
h. Summit of crown also folded ; 
Rodentia {Lepus, CMnchilla). 
Division III. Bunodont type ; crown supporting tubercles. 
a. Tubercles few, opposite ; Un- 
gulata, Achmnodon, Dicotyles, 
Elotherium ; Carnivora, Pro- 
cyon ; Rodentia, Heliscomys. 
J). Tubercles few, alternate ; Ihjop- 

7 Fio. 17. — LeptocTicerus. 

c. Tubercles numerous, irregular ; Mastodon, Phacochcerus. 
Division IV. Lophodont type ; the summit of the crowns 
thrown into folds of transverse or longitudinal direction. Higher 

Fig. 15. — Glolicephalus. 

Fig. 16. — Jaeulus hudsonicus. 


This division embraces the many types observed in the Ungu- 
lates, some Eodents, and possibly Carnivora. Inasmuch as the 
teeth of the maxillary and dentary (mandibular) bones do not al- 
ways conform to the same tyj^e (e. g., Symborodon, Equus), it 
will be necessary to consider them separately. Besides the differ- 
ence in type, they differ in their rela- 
tive development in width in the 
more specialized forms ; thus, in 
Homo, Mus, Mastodon, and such 
genera, the molars of both jaws are 
identical ; in PalcBotherium, Eohasi- 
leus, Tapirus, etc., and most Car- 
nivora, the superior are the wider, 
tlie inferior narrower, appropriately 
to the greater slenderness of the 
mandibular bone. The latter, or 
anisognathous type, may then be regarded as the more specialized. 
The Bunodonts, except some Carnivora, are all of the former or 
isognathous type ; among Lophodonts the few Eodents, the Dino- 
theriidcB, and Elephas are isognathous, while all of the other 
Prohoscidia, the Perissodactyla, and Ruminantia are anisogna- 
thous. Examples may be selected as follows : 

Isognathous ; Bunodonts : Homo, Dicotyles, Bus, Mastodon, 
Elotherium ; Lophodonts : Dinotheriidce, Eleplias ; Rodentia, 

Anisognatlious ; Bunodonts : Macacus, Lemur oidea, Procyon ; 
Lophodonts : Anoplotherium, Hyopotamus, Oreodon, Ruminantia, 
Perissodactyla, Batlimodon, Uijitatlieriuni. 

Fig. 18. — EMnocerus (temporary). 


1. The Maxillary Teeth* 

It is apparent that the type of superior molar tooth which pre- 
dominated during the Puerco epoch was triangular or tritubercu- 
lar ; that is, with two external and one internal tubercles, f Thus, 
of sixty-seven species of placental Mammalia of which the superior 
molars are known, all but four have three tubercles of the crown, 

* This division is inserted from the " Proceedings of the American Philosophical 
Society," for December, 1883, for the sake of supplying an omission in the original 
memoir. (Ed. 1886.) 

t See "American Naturalist," April, 1883, p. 407. 


and of the remaining sixty-five, all are triangular, excepting those 
of three species of Periptychus, and three of Conoryctes, which 
have a small supplementary lobe on each side of the median prin- 
cipal inner tubercle. 

This fact is important as indicating the mode of development 
of the various types of superior molar teeth, on which we have not 
heretofore had clear light. In the first place, this type of molar 
exists to-day only in the insectivorous and carnivorous Marsupi- 
alia ; in the Creodonta, and the tubercular molars of such Carnivo- 
ra as possess them (excepting the plantigrades). In the Ungu- 
lates its persistence is to be found in the molars of the Corypho- 
dontidse of the Wasatch, and Dinocerata of the Bridger Eocenes. 
In later epochs it is occasionally seen only in the last superior 

It is also evident that the quadritubercular molar is derived 
from the tritubercular by the addition of a lobe of the inner part 
of a cingulum of the jDosterior base of the crown. Transitional 
states are seen in some of the Periptychidae {Jnisonchus), and in 
the sectorials of the Procyonidas. 

2. The Mandibular Teeth. 

The tritubercular or triangular superior molar is associated 
with a corresponding form of the anterior part of the inferior 
molar. This kind of inferior molar I have called the tubercular 
sectorial, and is very variable as to the degree of development of 
the sectorial cutting edge. The anterior triangle is formed by the 
connection by angle or crest, of the median and anterior internal 
crests with the anterior external. Its primitive form is seen in • 
Didelphys, Pelycodus, Pantolambda and the Amblypoda gener- 
ally ; in Centetes and Talpa ; and in its sectorial form, in Stypo- 
lophus and Oxyaena, etc. 

The * tubercular molar of some Yiverridm, and among the ex- 
tinct forms especially the Didymictis protenus, Cope, present a 
similar structure to that just described. This furnishes a ready 
explanation of the tooth immediately in advance, which is the 
primitive form of sectorial tooth characteristic of primitive Car- 
nivora. The three anterior tubercles are largely developed, stand- 

* The remainder of this section (2) is taken from the writer's " Synopsis of the 
Vertebrata of the Eocene of New Mexico," p. 800. Publication of the U. S. G. G. 
Survey, W. 100th Meridian, 1875. (Ed. 1886.) 


iiig at opposite angles of a triangular space ; the outer and ante- 
rior cusps are the most elevated, and the ridge which connects 
them is now a cutting blade. The posterior portion of the tooth 
does not share in this elevation, and its two tubercles are in some 
genera obsolete, and in others replaced by an elevation of one mar- 
gin, which leans obliquely toward the middle of the crown. In 
Mesonyx this is represented by a median longitudinal crest. If 
the two tubercles of the posterior part of this tooth {which may be 
termed a tubercular sectorial) are elevated and acute, we have the 
molar of many recent and extinct Insectivora ; if the same por- 
tion (now called a heel) is much reduced, we have the type of 
Oxymna and Stypolophus. In the Canidcc the three anterior tu- 
bercles are much less elevated than in the genera above named ; the 
external is much the larger, and the anterior removed farther for- 
ward so as to give the blade a greater antero-posterior extent. 
The heel is large and without prominent tubercles. In the Muste- 
lidcB the inner of the two median cusps is often reduced to a rudi- 
ment, or is entirely wanting, and the heel is large. The lower 
sectorial of the Hycenidce has no inner tubercle, and the heel is 
much reduced. In some of the saber-toothed tigers the heel re- 
mains as a mere rudiment, while in the true cats it has entirely 
disajDpeared, and the carnassial tooth remains perfected by sub- 
traction of parts, as a blade connecting two subequal cusps. The 
Hycenodontidce, as is known, possess three carnassial teeth without 
inner tubercles. The history of tliis form is as yet uncertain, as 
it was evidently not derived from contemporary forms of the 
Eocene with tubercular sectorials. 

The development of the inferior carnassial dentition has thus 
been accomplished by the subtraction of the inner and posterior 
cusps, so that of the original four of the quinquetuberculate molar 
but a single one, i. e., the anterior external, remains. 


1. The Maxillary Teeth. 

In the essay already quoted * the following remarks (page 7) 
explain the relation between the Bunodont genera and several of 
the Lophodont types of superior molar teeth: ''In the superior 

*" Primitive Types of Mammalia Educabilia," May, 1873, and Hayden's "Re- 
port on Geological Survey of Montana, Wyoming, etc.," 1873, p. 646. 


molar series the flattening of the outer tubercles may proceed so 
far as to produce, on wearing, a confluence of the [resulting] cres- 
centoid surfaces. ... In both PalcBosyops and Hyrachyus these 
tubercles of the upper molars are confluent into two Vs (more or 
less open when unworn). In the former the inner tubercles retain 
their primitive conic tubercular form, but in Palceotherium, Rhi- 
nocerus, Lophiodon, Hyrachyus, and Tapirus they elongate trans- 
versely so as to meet the corresponding outer tubercles (now crests) 
forming the familiar cross-crests of those genera. If alternate, 
the oblique crests of Palceotherium; if opjDosite, the cross-crests 
of Tapirus. If, on the other hand, the inner tubercles flatten like 
the outer, we have, on wearing, the quadricrescentoid [Selenodont] 
type of the Euminatitia and Anoplotherium. In the Quadruma- 
nous families, including man, the primitive quadrituberculate type 
of molars is preserved." 

Four types of Lophodont dentition are included in the above 
discussion, and three others may be added. They belong to two 
series, viz., those in which the crests represent the modification 
of opposite tubercles, and those where the tubercular elements of 
the crown are alternate. These series may be called the Amoeho- 
dont (alternate), and Antiodont (opposite), and the component 
types are : 

Antiodonts. — Selenodont (Euminants) ; Tapirodont {Tapir, 
Rhinocerus) ; Tricliecliodont (Manati, Elephant). 

Amcebodonts. — PalcBotheriodont (Palaeotherium, etc.) ; 8ym- 
horodont (Palaeosyops Symborodon, etc.) ; Bathmodont (Bathmo- 
don, etc.) ; Loxolophodont (Uintatherium, etc.). 

These types are defined as follows : 

1. Antiodonts. 

Selenodonts. — The tubercles separate or united at their angles, 
much elevated, narrow crescentic in section, separated by deejj 

To this group belong the molars of the Euminants, the Tra- 
gulidm, the Oreodontidm, and MerycopotamidcB ; of Perissodac- 
tyles the Equidm. 

Tapirodonts. — The outer tubercles longitudinally compressed, 
subcrcscentic in section ; the inner transversely compressed, con- 
tinued as transverse ridges to the end or middle of the correspond- 
ing exterior crests. 

Rhinocerus, Tapirus, Hyrachyus, Lophiodon, and Hyrax rep- 


resent this type ; the last molar of Lopliiodon appears to he Amm- 

Trichecliodonts. — Tubercles confluent into two or more trans- 
verse crests. 

The Dinotlierium represents this form, so does Elephas, Tri- 
checus (the manati), and a number of the larger Marsupialia. 

2. Amcebodonts. 

PalcBotheriodonts. — External tubercles longitudinal, subcres- 
centic in section ; the inner united with them by transverse oblique 

Palmotherium and AncMtherium present this type, which only 
differs from the Tapirodont in the alternation of the opposing 

Symborodonts. — External tubercles longitudinally compressed 
and subcrescentic in section ; the inner indejoendeut and unal- 
tered, i. e., conic. 

To this group are to be referred the types of Palwosyops, Me- 
nodus, and Symhorodon. They, of all Lopliodonts, approach near- 
est to the Bunodonts. 

Batlimodonts. — The posterior pair of tubercles approximated 
and connected, together compressed and subcrescentoid in section ; 
the anterior outer connected Avith the anterior inner by an oblique 
crest forming a V with the preceding. 

Batlimodon and Metalopliodon. — The homologies of the crests 
are difficult to make out ; the subcrescentic crest of the second 
molar may include only the posterior outer tubercle, and thus be 
entirely homologous with the posterior crescent of Palseosyops. In 
support of this view we have the structure of the premolars, where 
it becomes the only external crescent, while the anterior transverse 
crest turns round on its inner side, supporting the inner anterior 
tubercle of the tooth. [Note to this edition : The latter view is 
the correct one, as the posterior inner tubercle is wanting.] 

Loxolopliodonts — Anterior inner tubercle connected with the 
two external by oblique crests ; the posterior inner tubercle rudi- 
mental or wanting. 

UintatJierium and probably Tillotherium represent this group, 
both being like those of the last, extinct genera from the Eocene 
of Wyoming. 


2. The Mandibular Teeth. 

The h'pes of structure are less numerous tban those of the 
maxillary teeth, since I am only acquainted with six. Still more 
distinctly than those of the upper jaw do they represent the types 
of opposite or alternating tubercles, or the antiodont and amoebo- 
dont. The essential principles of modification are the same as in 
the maxillaries, and they correspond with them as to genera, as 
follows : 







Tapirodont pt. 
j Tapirodont pt. 
] Trichecodont. 





J Palfeotheriodont. 
( Symborodont. 
Selenodont pt. 
j Bathmodont. 
( Loxolophodont. 
The characteristics of these groups are as follows : 

A. Antiodonts. 

Selenodonts. — Constructed, typically, like the upper molars. 

Hyracodonts. — External tubercles compressed longitudinally 
and crescentic in section, continuous by a cross-crest with the cor- 
responding tubercle of the inner side. 

The animals which possess this type of teeth are the Rhinoce- 
rus, ffyracodon, and the Hyrax ; it is nearly approached by some 
of the Hyrachyi. It corresponds in structure with the true tapiro- 
dont arrangement of the maxillary teeth ; but many of the Tapiro- 
donts have the Trichecodont type of mandibular teeth. 

Trichecodonts. — Definition the same as for the maxillary teeth. 

Tapirus, Lophiodon, Hyrachyus, Dmotherium, Elephas, Tri- 
checus (the manati), and the Kangaroos and their extinct allies 

belong here. 

B. Amcebodonts. 

Hippodonts. — In the horses the maxillary molars are con- 
structed on an oj)posite crested basis, while the mandibulars repre- 


sent an alternate crested type. This is not constituted as in the 
next form, by a union of alternating tubercles, but as in the Sele- 
nodonts by tbe special development of each crest into a ci'escent 
extended antero-posteriorly. As alternating, the inner crescents 
stand at the apices of the outer, and are connected with them. 
In Anchitherium the inner are so reduced as to constitute a condi- 
tion intermediate between the Hippodont and Symhorodont types. 

Symborodonts. — The alternating tubercles connecting by 
oblique ridges which form together two Vs. 

To this type is to be referred a great number of Perissodac- 
tyles, e. g., AncliWiejHum, Palceotherium, Palceosyops, ilenodus, 
Symhorodon, AncMppodus. 

Loxolopliodonts. — Alternate cusps connected by two cross 
ridges from the outside forward and one from the inside forward ; 
from which result an oblique posterior cross ridge, and a V open- 
ing inward. 

Here are Eobasileus and Bathmodon ; the last molar of the 
latter having the anterior ridge of the V quite low. 

S. Comparison of the Opposing Series. 

In review, the above types of molar dentition maybe classified 
as follows, with reference to the amount or complication of the 
modification of the tubercular type. The orders of Ungulata with 
which they correspond, are also given. 

a. Both inner and outer tubercles crescentoid. 

( Ruminantia. 
Selenodonts. j {Anoplothcrium, Oreodon, Hyopotamus). 

( Perissodactyla {Equidce). 

p. External tubercles only crescentoid ; the inner transverse 
or tubercular. 
Tapirodonts. j 

Palaeotheriodonts. V Perissodactyla in gen. 
Symborodonts. ) 

y. Neither kind of tubercles crescentoid, but united in pairs. 
Trichecodonts. Prohoscidia. 

It may be added that the groups arranged under y are the 
only ones in which the types of crests of the superior and inferior 
molars are fundamentally simple and alike. Thus in the group 
a, tubercles of both upper and lower series are modified independ- 
ently to produce tlie type ; in group /3, the tubercles of the upper 
series are modified independently of each other, while those of the 


inferior series unite, in order to produce the result ; in division 
y the tubercles of both jaws unite entirely across the crown, with- 
out any distinction between those of the outer and inner sides. 
Thus the molar type of dentition of the Prohoscidians is the most 
generalized among the Lophodonts, resembling in this respect the 
type of construction of the feet. 


The four types of molar dentition, the Haplodont, Ptycho- 
dont, Bunodont, and Lophodont, are by no means sharply de- 
fined, but pass into each other by insensible gradations at many 
points. The addition of cusps to the simple cone has been 
accomplished by the appearance of folds at the base of the 
crown, which have increased in size so as to resemble the primi- 
tive cusp to which they are attached. As already pointed out, 
the first additional cusp in the transverse direction appears on the 
inner side of the first, or anterior cusp. The last one was ap- 
parently the inner posterior. I first consider the carnassial mo- 

1. The Carnassial Bunodonts. 

In tracing the appearance of the different types of superior 
sectorial in time, the following facts are patent : In the Eo- 
cene genera, 3fesonyx, AmUydonus, Oxycena, Sty poIopJius,* etc., 
the inner tubercle is much more largely developed than in any ex- 
isting Carnivora, with the exception of some of the Viverridce. In 
all, the sectorial crowns are less efficient as shear-like cutters than 
in Canidm, Mustelidw, Hycenidce, and Felidce, on account of the 
shortness of the posterior blade and the slight compression of the 
anterior cone. On the other hand, in all of them the number of 
teeth presenting the carnassial or three-tubercled type is greater 
than in existing genera, the posterior upper molars in the latter 
being either narrowly tubercular or wanting. The genus Hyceno- 
don, while agreeing with the others in this respect, differs from 
them in the great reduction of the inner cusp, which is obsolete 
even in the representative of the true carnassial tooth, although 
the inner root remains in all. Hence this type of dentition might 
be regarded as the most specialized of those of the Carnivora, 

* In the original, the synonym Prototomus is used here. 


but for the fact of the imperfection of the shear blades in all ex- 
cept the last. This is seen in the large and prominent anterior 
cusp and very short posterior blade. 

In all recent and most Miocene Carnivora, the sectorials are 
reduced to one in each jaw, the exception in the latter period 
being the genus Hymnodoji, which did not continue later. The 
posterior carnassials of the Eocene forms disappear, and in the 
most specialized recent families Hycenidce, Mustelidm, and Fe- 
lidcB have scarcely any representatives. The shortening of the 
series appears in the premolars as well, until we have the formula 
of the Felidm, P. m. 2 ; M. 2. 

In the inferior dentition the same process may be observed in 
the successional modifications of the entire series. The Eocene 
forms of carnivora frequently display more numerous sectorial 
teeth (such as they are) than any of the existing families. The 
important change, which is clearly indicated, is the progressive 
extinction of the genera with numerous sectorial teeth, accom- 
panying the increasing specialization of the sectorial tooth in the 
genera which remain. In other words, the numerous types of 
digitigrade carnivora which have survived are those developing 
but one sectorial tooth (whose earliest representative is Didymic- 
tis). The increased perfection of the sectorial tooth has been as- 
sociated with a reduction in the number of other molars, first, 
posterior, then anterior to it, which reduction has been accom- 
panied by an increased relative size of the sectorial. By this pro- 
cess concentration of the carnassial function has been gained, and 
increased robustness of the Jaws, by progressive shortening. The 
slender form of the rami of the Eocene genera and Hycenodon are 
much less efficient in functional use than the stout jaws of exist- 
ing Mustelidm, Hycenidce, and Felidce. 

2. The Lopliodo7its. 

Transitions between the Bunodonts and Lophodonts are very 
obvious, so much so as to lead to the belief that the several sub- 
divisions of the Lophodonts represent modifications of correspond- 
ing types of Bunodonts, and that the two are partially "homolo- 
gous groups." Both present corresponding Ama?bodont and An- 
tiodont types ; as an example of the former kind of Bunodont, 
the mandibular molars of the genus Hyopsodus may be cited ; of 
the latter kind, the same of the genus Achcenodon, both the ear- 
liest, or Eocene genera. It remains to indicate the intermediate 


forms, if any there be, which give color to the supposition that 
the various divisions of Lophodonts have descended from Buno- 
dont predecessors. Here, then, I mention a fact of prime impor- 
tance, i. e., that in America, at least, no Selenodonts are known 
from formations of older age than Miocene ; while the greatest 
development of Bunodonts is in the beds of the next older epoch, 
the Eocene. 

The special forms of Loj^hodonts may be separately considered 
as follows : 

First, as to the opposite and alternate types, or the Antiodont 
and Amoebodont. They pass into each other by many intermedi- 
ate conditions among the Bunodonts, as in Nothardus, Lim- 
notherium, etc., of the Wyoming Eocene. There is reason, also, 
to believe that this has been the case with some of the Lophodonts 
after they had left the bunodont stage behind. Thus Equus is an 
antiodont as to its upjier molars, but has been probably derived 
from Palceotheriodont ancestors, which are amoebodont ; this is 
rendered especially probable by the fact that the mandibular teeth 
are of the amoebodont division (hippodont). It is also highly 
probable that the antiodont genus Tapirus, though so near to 
Palceotheriuni, was derived from an antiodont Bunodont. Hence, 
while the discrimination between opposite and alternate types is in 
some cases most radical, in others its importance is but slight. 

L Antiodonts: Bunodont type Achcenodon (Fig. 19). 

1. Selenoclo7it type approximated by the bunodont Hijjpojwta- 
mus, where the tubercles are compressed, thus : the intervening 

Fig. 19. — Achcenodon insolens. 

valleys are deepened, and tlie cusps wear readily into separate 
crescents. Another intermediate form is seen in the genus An- 
thracotherium, where the tubercles of the mandibular teeth are 
compressed, while they remain conic (Fig. 21) ; selenodont forms 
of Omnivora present us with near approaches to these Bunodont 
genera. Thus in Hijopotamus and Anoplotlierium, the crowns, 


when unworn, present four princijaal tubercles, which are openly 
V-shaped in section, and which are separated by open valleys. 

The latter are deeper than 
those of the truly Buno- 
clont genera, but much 
shallower than those of the 
typical Selenodonts. In 
Oreodon the valleys are 
somewhat deepened and 
the crescents elevated, while 
in the deer the same infold- 
ing is carried still further. 
In the Cavicornia the type 
reaches its fullest expres- 
sion in the loss of the shoul- 
der at the base of the crown, 
the great elongation of the 
latter, and corresponding- 
ly deep infolding of the 
terminal valleys. 

Professor Lartet* states 
that the most ancient deer 
have very short - crowned 
molars, and the depressions 
on the surface are so shallow that the bottom is always visible, 
while in the Cervidce of the more recent Tertiary periods, and 

especially the Plistocene and living species, 
these same cavities are so deep that what- 

FiG. 20. — Hippopotamus. 

Fig. 21. — Htjopotamus velaunus. 

Fig. 22. — Hyopotamus americanus. 

Fig. 23. — Procamelus robustus. 

ever be the state of attrition, the bottom can not be seen. This, 
he says, is a perfectly reliable rule for distinguishing tlie ancient 
from the more modern forms of deer, and can be ajiplied to other 
animals as well as the Cervidae. 

'Comptes Rendus," 1868, p. 1119. 


Fig. 24. — Meryehyus major. 

The writer nearly contemporaneously * recalled the observa- 
tions of Leidy that the teeth of the Oreodont " Mei^ychyus are 
more prismatic, have larger crowns and shorter roots, approaching 
the sheep, as Oreodon does the deer." Now Oreodon is Miocene, 
and Meryehyus Pliocene. It was then ob- 
served : "This phenomenon suggests an ex- 
planation on the score of adaptation which 
the other cases do not. The existence dur- 
ing the later period of a [hard]er material 
of diet would increase the rapidity of wear- 
ing of the crown of the tooth, and require a 
longer crown and greater rapidity of protru- 
sion. This necessitates a diminution of the 
basal shoulder and shortening of the roots, producing the prismatic 
form aforesaid." 

These observations render it highly probable that the seleno- 
dont molar is produced by a modification of the antiodont buno- 
dont molar. Also, that the manner of the change has been by 
constant acceleration of growth of the folds of the tooth upward 
and perhaps downward in its long axis ; and an acceleration in the 
lengthening of the crown. 

2. Tapirodonts. — This form is so nearly similar to the Palaeo- 
theriodont that any series annectant between the latter and the 
Bunodonts will render very probable such a connection for the 
Tapirodonts also. Indeed, it is clear that the same evidence will 

be sufficient in both cases, since the pre- 
molars and last molar of Lophiodon are 
amoebodont, like Pcdceotlierium. In point 
of fact, however, the tubercles of the molars 
of Achmnodon are partly united in transverse 
pairs, while there are intermediate tubercles 
connecting the opposite cones in some molars 

of Elotherium. These structures foreshadow this group as well 

as the Trichcchodont. 

3. Trichecodonts. — The Mastodons and Elephants form a most 
complete series between this form and the Bunodonts, as has been 
pointed out by Falconer. In this series, the transverse rows or 
pairs of tubercles, as well as the crests, may be few or many. Thus 

Fig. 25. — Tapirus, 

* " Proceedings of the Academy of Natural Sciences of Philadelphia," 1868, 
p. 274. " Origin of Genera," p. 44. 


in Elotherium, Halitherium, and Trichechus tliey are few ; in 
Trachytherium and Dinotlierium more numerous ; in Mastodon, 

Stegodon, and Elephas, most 
numerous. The tubercles are 
united into serrated cross- 
erests in HalWierium, the ex- 
tinct sea-cow ; in Trachythe- 
rium, another fossil ally of the 
Manati, the tubercles are not 
united. The succession from 
Mastodon to Elephas may be 
represented by the accompany- 
,, , ., inff fiffures : Fio^. 26 (from 

iiG. 26. — Mastodon angushdens. . . . , « ,V 

Cuvier) is a molar of M. an- 
gustidens, where, beside the principal tubercles, numerous lesser 
ones appear. Fig. 27 represents Mastodon ohioticus, in which 

Fig. 27. — Mastodon ohioticus. 

Fig. 28. — Dinotherium giganteum. 

the opposite tubercles are nearly united into transverse crests. 
In Di7iotherium (Fig. 28) and Elephas (Fig. 29) the union is 
complete. The relation of these 
genera has been described as 
one of " inexact parallelism " ; a 
condition supposed by the writer 
to depend on modification in 
descent under the law of acceler- 
ation. The language used is : * 
'* The young tooth of Elephas, 
moreover, is represented by a 
series of independent parallel 

Fig. 29. — Elephas indicus. 

lamina? at first, which, when they unite, form a series of crests 

* "Origin of Genera," p. 17. 


Fig. 30. — Microsyops elegans. 

similar to the type [i. e., pattern] of the genus Mastodon [Stego- 
don] and others of the beginning of the series. The deposit of 
cementum takes place later, till the valleys are entirely filled 
up. Thus the relations of this 
part of the tooth structure in 
the series are also those of the 
successional growth of Elephas 
or the extreme of the series." 
The transition from the 
bunodont type to the lophodont in the mandibular dentition is 
seen in the Eocene genera Microsyops and Limnotherium, where 
the opposite cones are connected by a low cross-crest. 

n. Amcebodonts; ^nnodiovit tj^Q Hyopsodus.* 

4. Symhorodonts. — In Hyopsodus the exterior cones are already 
somewhat excavated on the inner side, so that a section of each is 
somewhat triangular. It is obyious that but little more compres- 
sion and curvature are required to produce the type of Palmosyops, 

Fia. 31. — Hyopsodus. 

Fig. 33. — AncMppodus. 

Fig. 32. — Palaosyops Icevidens. 

Fig. 34. — Palceosyops. 

etc. (Fig. 32). The angles of the outer cones in Hyopsodus are 
also slightly produced as low ridges to the bases of the alternating 
tubercles of the opposite side : the elevation of these ridges is only 

* I orif^inally (" On the Primitive Types of Mammalia Educabilia," p. 9 ; " Ilay- 
den's Geoiog. Survey Terr.," 1872, 1873, p. 648) selected Pliolophus ( Oligotomus Cope) 
for this position, but as it has a considerable diastema, it is better exchanged for 
Hyopsodus, where the dental series is uninterrupted. 


¥m. 35. — Palceoiherium. 

Fig. 36. — Hippos^us. 

necessary to produce the two Vs of the mandibular dentition of 
FalcBotherium, PalcBOsijops (Fig. 34), Symiorodon, A?ichippodus 
(Fig. 33), and all their allies (Fig. 35, PalcBotherium). 

5. PalcBotheriodont type. — Immediately following the form of 
the Palwosyops molar we have that of Hipposyus, where inter- 

_ mediate tubercles stand be- 

tween the inner subconic and 
the exterior longitudinal cres- 
centoid tubercles. They are 
compressed so as to be trans- 
verse, and only need more 
comj)lete connection with the 
adjacent tubercles to give the 
oblique transverse ridges of 
A ncliithei'ium, Pcdwotherium, 
and Hyracodon, Rliinocerus, 
etc. Hipposyus was origin- 
ally compared with AncMtherium by Dr. Leidy, and the writer in 
ignorance of his language remarked :* "An interesting annectant 
form is seen in Lanibdotlierium\ procyoninum, where the two inter- 
mediate tubercles which separate the inner cones from the outer 
Vs in Limnoliyus are so developed as to constitute parts of an in- 
complete pair of transverse 
ridges which disappear in 
front of the bases of the 
outer Vs. They represent 
the oblique crests of PalcBO- 
tJierium and AncliitJierium, 
and thus the genus Lamb- 
dotherium furnishes a sta- 
tion on the line from Pal(B- 
osyops to the horses." Contemporaneously and quite independ- 
ently Prof. Marsh expressed similar views I as to its affinities. 

A greater longitudinal extent of these ridges or longitudinal 
expansion of the tubercles in the molars in both jaws, the oblique 
connections being still retained, gives the type of Equus (Fig. 39). 
The elevation of the tubercles and deepening of the valleys gives 

* Haydcn's "Geo!. Surv. Montana," etc., 187-3, p. 64V. 

f This species was in the original erroneously called OroJdpjjus procyoniniis, 
(Ed. 1886.) 

X "Amer. Joum. Sci. Aits," 1873, p. 407. 

Fig. 37. — Hipposyus. Fig. 38. — HypoMppus. 


Superior molar of 

US the Selenoclont type of superior molars again in this genus ; 
while the lower molars only diifer from that type in having the 
crescents alternate instead of opposite, forming the Hippodont 
pattern (Fig, 40). There can be little doubt that the line of the 
horses comes through Hipposyus* from, the Bunodonts, rather than 
through PalcBotherium, as has been sug- 
gested by some writers. 

6. BaiJimodont type. — I know of no ge- 
nus which by its iiitermediate structure 
connects this type of molar with the Amce- 
bodont form of Bunodonts.f Such will 
doubtless be discovered, for it is impossible 
that the upper molar of Bathmodon could 
have been produced by the modification of 
any known Palaeotheriodont, the type which 
it most nearly resembles. The structure of 
the feet of the animal forbids any such sup- 
position. Such intermediate types would 
have, firstly, the (oblique) crests more nearly 
equal in length and similar in direction. A 
depression of the crests and indication of 
diagonal ridges connecting the tubercles in 
the opposite direction would produce an 
approach to a W, and the form of Hyopso- 
dus. That this was probably the history 
of this curious type is rendered probable by 
the form of the mandibular teeth, which exhibit two of the in- 
termediate stages above anticipated. Thus the last inferior molar 
exhibits two obliquely transverse crests of subequal length, with 
rudimental oblique or diagonal ridges connecting them. In the 
median lower molars one of the latter is developed, giving a V, 
as in Palceotlierium, but the posterior one is undeveloped, leaving 
only the original oblique cross-crest. J 

7. The Loxolophodonts. — Like the preceding group I know 
of no type connecting this form with the Bunodont, but antici- 
pate the discovery of a type with a rudimental posterior V on the 

Fig. 40.- 

Inferior molar of 


* I have since shown tliat Hyracotherium and Pliolophus, which have very 
similar dentition, are the types which occupy this position. (Ed. 1886.) 

\ Such has since been discovered in the genus Pantolambda (Cope). (Ed. 1886). 

X Sec " Proceed. Amcr. Philosophical Society," Sept., 1872, " On the Dentition of 


upper molars,* which shall connect it with the W-shaped type 
proposed above as the probable predecessor of Bathmodon. Or, a 
pair of oblique parallel crests with rudimental diagonals like the 
posterior lower molars of Bathmodon may intervene between this 
form and the Bunodont. This is, however, not probable in view 

Fig. 41. — Bathmodon. 

of the diagonal crest of the upper molars (Fig. 43, TJintatlieriufn 
rohustum), and especially if the parallel with the type of the 
lower molars is kept up. These are like those of Bathmodon, ex- 

FiGS. 42 and 43. — Uintatheriwm rolustum. 

cept that the type of the middle molars of the latter is continued 
to the posterior end of the series in Uintatherium (Fig. 43) ; that 
is, the last molar of the latter consists of a V and an oblique cross- 



I hope that I have succeeded in showing that the Bunodont 
and Lophodont types of dentition form two homologous series, 

* This has since been discovered in Pantolambda (Cope). (Ed. 1886.) 


similar to those already indicated among Batracliia, Anura, Ceph- 
alopoda, etc.* That this relation indicates descent of the corre- 
sponding terms of the one series from those of the other has also 
been rendered highly probable. This conclusion has also been 
previously stated as a theorem, f as follows : " V* The heterologous 
terms or genera in the later series are modified descendants of those 
of the earlier series " ; in other words, that certain groups higher 
than genera are produced from others of a similar high value by 
"descent with modification." 

As already pointed out, the Bunodont primary genera belong to 
the older geologic epoch of the Eocene, while most of the deriva- 
tive ones belong to later periods. Some were contemporary with 
the primary forms, but doubtless have descended from pre-existent 
members of the same type as yet unknown to us. The genus 
Aclmnodon, Cope, is especially generalized in three respects : (1) 
the simplicity of the construction of its molars ; (2) the same 
simplicity of the premolars, which are without inner or posterior 
lobes ; (3) the absence of all diastemata and consequent continu- 
ity of the dental series. Hence it may be regarded as more primi- 
tive than Palmochmrus, Cheer omorus, Dicotyles, or Elotherium, 
in all which there are marked diastemata. The two series may then 
be arranged as follows : with the understanding that in some cases 
names of genera used represent rather family groups, in which 
the special generic lines have not yet been made out. J 

The following table has been already published in its essential 
features in the " Keport on Geological Survey of the Territories," 
1873, p. 648.* 

It remains now to ascertain whether the genealogical or taxo- 
nomic relations expressed by the teeth coincide with those derived 
from the other diagnostic regions of the body. First of these must 
be selected, as of chief importance, the limbs and feet. 

* See " Origin of Genera," p. 63. f Loc. cit. p. 79. 

X Since the following table was published it has become probable that Achasno- 
don is an ungiiiculate and a flesh-eater. It has also been discovered that the genus 
Phenacodus possesses the characters which give it the place as the ancestor of all 
the lines in the table. (Ed. 1886.) 

* It was previously published in a separate form in " On the Primitive Types of 
Mammalia Educabilia," May 6, 1873. An error occurs in this edition in the reversal 
by a lapsus calami of the positions of the types Omnivora and Anoplothei-ium. It 
is also important to note, that in the " Report G. S.," p. 845, where it is stated that 
" during the Eocene they (the orders) were in process of differentiation," etc., Mam- 
malia Educabilia and not LissencephaJa, arc referred to. 












I— ( 




« - 



- o - 



I Loxolophodont 


■ c> - 



s: S 

o — >< — ^ — ? 

a. -IS o 



Selenodont pt. 

_ p 


- ? . 



_ o 





- '^ 



i 8 ■» 

■| — § — ~ — J Selenodont 



- o 








We may look on the Artiodadyla — even-toed or cloven-footed 
mammals — as one of the most homogeneous groups in the class, 
not only in respect to the structure of the extremities, but also in 
that of the cranium, vertebrae, etc. But here we have both Buno- 
dont and Selenodont types of molars. The Perissodactyla, as de- 
fined by the feet, axis, palate, etc., present us with the Symhoro- 
dont, PalcBotheriodont, Tapirodont, and Selenodont types of denti- 
tion in the superior series, and the Hippodont, Hyracodont, Pa- 
IcBotheriodont, and Trichecliodont types in the mandibular teeth. 
The pentadactyle, plantigrade type, for which I have used the 
name Prohoscidia, presents us with the Tricliecliodont, Batlimo- 
dont, and Loxolophodont types of molar structure. Among Siren- 
ians, as defined by the marked peculiarities of the entire skeleton, 
we have the great differences in dentition presented by Halicore 
and Trichecus, the former being Haplodont, the other Trichecho- 
dont. Finally, the Marsupial group is unquestionably well defined, 
and here Phascolomys is PtycJiodont ; Didelphys, Bunodont ; Pe- 
taurus between Bunodont and Selenodont, and the Kangaroos and 
their gigantic extinct allies the DiprotodontidcB, Tricliecliodont. 

It is thus evident that the molar types are everywhere subor- 
dinated to those which we call ordinal ; therefore in the case of 
the placental mammals, and especially those with complex folding 
of the cerebral hemispheres, to the types of construction of the 
feet. As to the modifications presented by the canine and incisor 
teeth, these exist within a still more narrow range of variation ; 
for instance, in the allied genera Equus, Rliinaster, and Symboro- 
don ; Sus and Pliacoclicerus ; Batlimodon and Unitatlierium, and 

It is thus probable that modifications in the three points of 
structure considered were introduced in the following order : 

First, Of the feet. 

Second, Of molar type.* 

Third, of the relations of canines and incisors. 

"With regard to the significance of the tnree types of feet. Pro- 
boscidian, Perissodactyle, and Artiodactyle, it has been already 
remarked : " It is to be observed that the lines of Ungulata, 

* In the case of the Marsupialia the relation of the dental and extreniital types 
may be reversed. Thus we have pentadactyle plantigrade forms (Opossums) and 
(nearly) didactyle difritigrade forms (3/ac>-o/)Ms) in the same order. Aho Ilahnatu- 
rm and DiproUxhn, both Trichcchodonts, differ in the type of feet, as do the car- 
nivorous Didclphjs and 7'hi/lacimcs, both Bunodonls. 


Quadrumana, and Carnivora originate in plantigrade types, a 
state of things quite predominant among the lower series or Lis- 
sencephala (smooth brains). It is universal in Edentata and very- 
usual in Rodentia and Insectivora. The lower forms of Marsu- 
pialia and all of the Monotremes present it. In the Marsupials, 
Rodents, Ungulates, and Carnivores, we have series whose highest 
expression is in the most highly digitigrade genera. " * To this it 
may be added that the lower terrestrial vertebrates are plantigrade, 
with some exceptions. Thus in some Anurous Batrachia there is 
a partial digitigradism ; the only digitigrade Reptilia are some 
Dinosauria, especially such carnivorous forms as Lcelaps ; all 
birds are digitigrade. The digitigrade modification evidently has 
reference to speed in running, or projectile force in leaping. 

The connecting points between the different types of foot- 
structure among the Mammalia Educabilia are as obvious as in 
the case of the types of molar structure. Examples may be ad- 
duced as follows : 

Carnivora. — In all of the genera of the Eocene Carnivora which 
I have had the opportmiity of examining, excepting Mesonyx, 
namely, Amhlyctonus, Oxycena, Prototomus, Didymictis, the tibio- 
astragalar articulation is of a primitive character. The astragalus 
is flat, and the applied surfaces are nearly a plane, and without 
the pulley-shaped character seen in existing Carnivora ; as dogs, 
cats, and in a less degree in the bears and in other Mammalia with 
specialized extremities, as Perissodactyla, Artiodactyla, etc. The 
simplicity of structure resembles, on the other hand, that found 
in the opossum and various Insectivora, Rodentia, and Quadru- 
mana, and in the Prohoscidia, most of which have the generalized 
type of feet. The structure indicates that the carnivorous genera 
named were plantigrade — a conclusion which is in conformity 
with the belief already expressed that the Mammalia of the Eocene 
exhibit much less marked ordinal distinction than do those of the 
Miocene or the recent periods. It is, indeed, questionable whether 
some of the genera here included in the Carnivora are not gigantic 
Insectivora, since the tibio-tarsal articulation in many, the separa- 
tion of the scaphoid and lunar bones in Mesonyx, the form of the 
molars, and the absence of incisor teeth in some, are all character- 
istic of the latter rather than the former order. 

Artiodactyla. — Approximations to the Perissodactyla are to be 

*" Mammalia Educabilia," p. 8; Hayden's "Geological Survey," IS'ZS, p, 647, 


seen in Hippopotamus in the increase in development of the lat- 
eral or first and fourth digits, thus equaling the number in the 
fore-foot of Tapirus and Menodus, though preserving the equal- 
ity of the two median digits. But an inequality of these digits 
appears in the genera Anoplotherium and CcenotTierium, as has 
been stated* in the following language : "In Anoplotherium se- 
cundarium the digit ii is developed in each foot, though not 
nearly so long as Hi, which is nearly symmetrical in itself. There 
is an approach to the same structure in the manus of Ccenothe- 
rhc7n." The only ajDproximation to the Proboscidian type is to be 
seen in the shortening of the metapodial bones in Hippopotamus, 
a point of very inconsiderable value. 

Perissodaciyla. — Approximation to the preceding order is 
made in the anterior foot of Menodus, in which, according to 
Marsh, there are four toes of nearly equal size.f Approximation 
to the ProhoscidiaX is seen in Symhorodon, where the cuboid facet 
of the astragalus is rather larger than in Rhinoceros, and devel- 
oped much as in Bathmodon ; the small third trochanter of the 
femur is also much like that in Bathmodon. The osseous horn- 
cores may be compared with those on the front of Loxolophodon, 
The knee was probably free from the integument of the abdomen, 
as in Proboscidians. In all other respects there is no approxima- 
tion to this order. 

Prohoscidia. — The approximations to other orders in the 
structure of the feet are only to be seen in the Eocene genera 
Bathmodon and Eobasileus. The latter, or its ally Uintatherium, 
presents, according to Marsh, but four toes on the hind foot ; the 
anterior lias five. In the former point we have a resemblance to 
Hippopotamus, but one of little significance, in view of the radical 
differences between the two in the form of the astragalus, cal- 
caneum, and cuboid bones. The former is essentially Proboscidian 
in all respects, with the addition of a cuboid facet alongside of 
and behind the navicular, as in Symiorodon ; thus constituting a 
Perissodactyle character, but leaning to the forms of that order 
which betray probably the closest, though slight, approach to the 
omnivorous division of the Artiodactyla. Thus, while the TJinta- 
theriidm present the Proboscidian type of feet and molar dentition, 

* Huxley, "Anatomy of the Vertebrated Animals," p. 321. 
f "American Journal of Science and Arts," 1873, p. 486. 

J This should be Amblypoda, not separated from the Proboscidia at the time 
this was written. (Ed. 1886.) 


if they present any ordinal characters resembling those of the 
Artiodactyla, they are equally shared by certain extinct Perisso- 

From the hints above furnished, we may regard the succession 
of modifications of foot-structure to be nearly as follows : 

Ruminantia. Rhinocerus. Equus. Elephas. 

I I.I 

Omnivora. Palseotherium. Hyracotherium.* 

Symborodoa. Palseosyops. Uintatherium. 

\ / / 

* BathmodoD. 

\ / 


I trust that I have made it suflBciently obvious that the primi- 
tive genera of this division of mammals must have been Buno- 
donts with pentadactyle plantigrade feet. It therefore follows that 
Elephas was not the descendant of Eohasileus nor Bathmodon in 
a direct line, but from some common ancestor with tubercular 
teeth, through Ifasfodon. We may anticipate the discovery of 
such a genus, and believe that it will not be widely removed from 
the Eocene Hyopsodus, or perhaps Achcenodon. This will, then, 
be the primitive ungulate. 

But it will be more than this ; it can not be far removed from 
the primitive carnivore and the primitive quadrumane. The Car- 
nivora are all modified bunodonts, and the lower forms ( Ursus 
Procyon, e. g.) are pentadactyle and plantigrade. As to the 
Quadrumana, man himself is a pentadactyle plantigrade buno- 
dont. This view has been already expressed, as follows: "The 
type of Tomitherium, already described, evidently stands between 
lemurine monkeys and such small allies of Pdlceotlieriidm with 
conic tubercular teeth {Oligotomus, Orotlierium,\ etc.), and which 
abound in the Eocenes of Wyoming. . . . The dentition of the 
two types is, indeed, but little different in the Quadrumanous and 

* This was called Hipposyus in the original essay — a name which really applies 
to a different type. (Ed. 1886.) 

f Both these are names for Pliolophus, a close allay of Ilyracotherium. (Ed. 


Ungulate types respectively, being a continuous series of I. 1 or 
2 ; C. 1 ; F. m. 3 — 4 ; M. 3 ; the canines but moderately devel- 
oped."* Such a hypothetical type might be expressed by the 
name Bunotheriidce, with the expectation that it will present sub- 
ordinate variations in premolar, canine, and incisor teeth. The 
premolars might be expected to differ in the degree of development 
of the internal lobes, the canine in its proportions, and the incisors 
in their number. 

In respect to the limbs proper, neither the Quadrumana nor 
Carnivora attain to the specialization seen in the Artiodadyla 
and Perissodactyla, for the ulna and fibula are never atrophied 
nor co-ossified with the radius and tibia, but are always distinct 
and free ; the only modification of structure in these points being 
the slight one involved in developing the rotary capacity seen in 
the higher monkeys. 

Thus the human series preserves in its feet, limbs, and den- 
tition, more of the characteristics of the primitive Bunotherium 
than any other line of descent of the Mammalia Educahilia. It 
even exhibits a retrogression, in the transition from the anisog- 
nathous Tomitherium to the genus Homo, where the teeth in the 
two jaws are exactly alike, as well as in the resumption of the 
continuity of the dental series after the diastema had prevailed 
among the higher monkeys. In one respect it has steadily ad- 
vanced, viz., in the number of convolutions and extent of the 
cerebral hemispheres and relative size of the brain as a whole. 

Note (Ed. 1886). — As remarked in a previous note, the discovery of the general 
characters of the genus Phenacodus in 1881, more than six years after the publica- 
tion of this paper, demonstrated the truth of the hypothesis here proposed, viz. : 
that the ancestor of the Mammalia Educabilia was a pentadactyle plantigrade buno- 
dont. The numerous genera and species allied to Phenacodus liave been placed in 
a suborder Condylarthra. See " American Naturalist," 1884, 790, for an illustrated 
article on this group. 

* nayden's " Geological Survey of Montana," etc., 1872, p. 645. 




In" order to prove the affirmative of a doctrine of evolution by 
descent of the existing types of living beings, two propositions 

must be established. The first, 
that a relation of orderly succes- 
sion of structure exists, which 
corresponds with a succession in 
time. Second, that the terms 
(species, genus, etc.) of this suc- 
cession actually display transitions 
or connection by intermediate 
forms, whether observed to arise 
in descent, or to be of such vari- 

Fig. ^.-FeriptycU^^ rhahdodon part ^^^^ character aS to admit of UO 
of posterior loot, two thirds natural size ; .... 

6, astragalus from above, showing flat other explanation of their origin 

face ; e, metatarsals, the first lost, show- than that of descent, 
ing plantigrade foot. Original ; from j^ ^]-^g gg]^ ^f paleontology it 

Puerco Epoch of New Mexico. . . , -,-,!'-, 7 ; 

is quite possible to demonstrate 

the first of these propositions, while the proof of the second is 
necessarily restricted to the observation of variations and the dis- 
covery of connecting forms which destroy the supposed definitions 
of species, genera, etc. The conditions are more favorable for the 
investigation of animals of the higher types than of those of the 
lower. Their late origin insures to us the opportunity of discovery 
of their ancestry far more certainly than in the case of the lower, 
whose beginnings are lost in the remote past, and belong to periods 
whose deposits have undergone physical changes, or have been en- 
tirely removed and redeposited elsewhere, thus insuring the de- 
struction of the fossil remains once contained in them. The series 
of the tertiary Mammalia is becoming more complete through the 

* Read before the American Association for the Advancement of Science, at 
Detroit, 1875, under another title. 


recent explorations in the West, and the results are embraced in 
the forthcoming quarto 
reports of the Hayden and 
Wheeler U.S. Geological, 
etc., surveys of the Terri- 
tories. An abstract of 
some of these is given in 
the present essay. 

The primary forms of 
the Mammalia repose in 
great measure on the struc- 
ture of the feet. Those of 
the teeth are also very sig- 
nificant, but present a 
greater number of varia- 
tions among animals other- 
wise nearly related. The 
osteology of the feet of re- 
cent land mammals falls 

Fia. 45. — Cori/phodon elephantopus, anterior 
foot from above, one third natural size. From 
Lower Eocene of New Mexico. The cuneiform 
(C«) is injured. (Original.) 

into several categories. These may be 
called the plantigrade, 
many-toed type ; the car- 
nivorous type ; the horse 
type, and the ruminant 
(e. g., ox) type. The 
lower vertebrates, as sala- 
manders, lizards, etc., dis- 
play the simplest form of 
feet, having usually five 
toes, with numerous sepa- 
rate bones of the palm 
and the sole, which they 
apply to the ground in 
progression. The many- 
toed or multidigitate 
type of mammalian foot 
most nearly resembles 
this condition, but dif- 
fers in the points of dif- 
ference which are com- 
mon to all Mammalia. 
In the hind foot a succession of forms leads from this general- 

Fio. 46. — Posterior foot of Coryphodon elephan- 
topus. From Lower Eocene of New Mexico. (Orig- 



ized type to the extreme specializations observed in the horse and 
the ox. 

The modifications are as follows : The hind foot is composed 
of two rows of tarsal bones, of which the second is followed by 
the long metatarsal bones, from which the bones of the toes origi- 
nate. The second segment of the hind leg is composed of two 
bones, tibia and fibula, which in the salamander, etc., have a sub- 
equal union with the foot. In some multidigitates, as the genus 
Corypliodon, both these bones articulate with the 
two bones of the first row of the tarsus, and one 
(fibula) is the smaller of the two. In many higher 
forms they articulate with but one of these tar- 
sal bones, viz., the astragalus, with which they 
form a perfect hinge joint ; the other tarsal bone 
of the first row is the 
calcaneumi or heel-bone. 
In Corypliodon the as- 
tragalus and the applied 
leg-bone (tibia) are near- 
ly flat, offering an ex- 
tremely imperfect hinge 
for the foot, and the 
heel-bone (calcaneum) 
is exceedingly short. 
The animal plainly 
walked on the entire 
sole of the foot, and 
must have had an awk- 
ward gait, from the 

slight power of flexing ^oot oi Phenacodus primoi 

the ankle-joint. From ""'' ^ ^^*- '^^'- ^^"^"^ 
this point to the horse on one side, and to the ox on the other, we 
have a line of succession of intermediate forms. And before de- 
scribing them, I may state that the Corypliodon is one of the old- 
est known Mammalia, its remains having been found in the Lower 
Eocene Tertiary of New Mexico and Wyoming, while the ox and 
horse are extremely modern animals, their advent on the earth 
having preceded that of man by but one geological period. 

The most perfect ankle-joint is that of the ruminating animals. 
The astragalus presents a deeply grooved segment of a pulley ; an 
angulated pulley, face downward to the rest of the foot, and a 

Fm. 47. — Left anterior 

Fio. 48. — Left posterior 
foot oli Phenacod us primm- 
viis, }4 ii^t' size. (Orig.) 



smooth convexity to the hollow of the applied heel-bone behind. 
No such astragalus has ever been found in the Lower Eocene forma- 
tions of America ; animals bearing it in a less perfect stage appear 
in the next higher period, the Miocene ; but it is not until the 
Pliocene and modern times that they abound. In the Hippopota- 
mus foot, we have an example of the less perfect astragalus of this 
type of animals. The pulley surfaces 
are flatter and less deeply grooved. 

In the horse, the upper surface 
of the astragalus forms as perfect 


. for 


Fig. 49. — Anterior foot of Homo sapiens from 
above, one third natural size. From Allen's 

Fig. 50.— Posterior foot of do. 
from above, one third natural 
size. From Allen's Anatomy. 

a joint as in ruminants, but the lower and hinder faces present 
the flattened surfaces which belong to the many-toed Mammalia. 
The lower face especially is mainly occupied by one large facet, in- 
stead of the two-faced pulley of the ruminants. In the rhinoceros 
a later facet is more distinct, while in the Miocene Menodus the 
second facet is larger, resembling, except in the still convex tibial 
articulation, the structure of that of the primitive Corijphodon. 


In the heel-bone we have a succession from the short and flat 
form of Coryphodon to the long and slender one of the horse and 
ruminants ; the increase in length being associated with the elon- 
gation of the bones of the toes, and the assumption of the digiti- 
grade type from the planti- 
grade. The mammals of the 
Lower Eocene * • exhibit a 
greater percentage of types 
that walk on the entire sole 
of the foot, while the suc- 
ceeding periods exhibit an 
increasing number of those 
that walk on the toes, while 
the hoofed animals and Car-- 
nivora of recent times, nearly 
all have the heel high in the 
air, the principal exceptions 
being the elephant and the 
bear families. 

A most noticeable succes- 
sion is seen in the diminu- 
tion of the number of toes. 
In the series leading to the 
horse, the ox, and the hyaena 
and cat, this reduction pro- 
ceeds by the loss of a toe 
from the one side or the 
other, until in the ruminants 
but two are left, and in the 
horse but one. The series ex- 
tending from the primitive 
Eocene types with five digits, 
to the existing reduced forms, 

is most complete, although Fig. r>\.—Phenacodus primcEvns skull, one 

a few of the New Mexican third natural size, from below, sliowing qiradri- 
T71 ,1 1 tubercular true molars. From specimen figured 

Eocene genera themselves . ^^ ^te 

probably exhibit but four 

digits on one or both pairs of feet. The presence of the rudiments 

* All the Mammalia of the Puerco fauna (which was unknown at the time this 
lecture was delivered) are plantigrade. (Ed. 1886.) 



of the lost lateral digits is constantly observed, and when these 
disappear it is to be finally replaced by the rudiments of the ad- 
joining toes in process of similar reduction. The bones of the sec- 
ond row of the tarsus which are in connection with the toes are 
not reduced so rapidly as the toes themselves; hence, the bones of 
the toes, in order to maintain the fit of the parts, increase in 
width, and consequently in strength. As is well known, in the 
horse the single toe is as stout as several united toes of lower 
forms, and the two toes of the ruminants have their basal seg- 
ments (metatarsals) united into a stout solid mass, the cannon- 
bone. At the same time several of the small bones of the sec- 
ond tarsal row become coossified, so that we have, in the rumi- 
nants and horse, the greatest consolidation of structure, connected 
in the former with the most elegant mechanism. It is scarcely 
necessary to add that, in the various cases of coossification and 
consolidation described, the foetus displays the original elements 

In the fore limb the same successional reduction in the number 
of toes may be traced as I have described in the hind foot ; but, 
as the bones of the palm differ from those of the sole, the succes- 
sional modification of these is also characteristic. The bones of 
the second row of the carpus are four in number, but as the toes 
are reduced, in the lines of the hoofed animals, the inner (tra- 
pezium) is soon dropped, and the second (trapezoides) becomes 
united with the third (magnum). In the carnivorous order, the 
trapezoides is always separate, but the inner pair of bones of tlie 
first row (scaphoid and the lunar) become consolidated into a single 
mass, although their original distinctness is easily determined by 
examination of the foetus. 

The two bones of the leg which articulate with the foot and 
hand, exhibit a succession of changes of relation in progress to- 
ward the more specialized types. In the Corypliodon and Uinta- 
therium of the Eocene, eacli of these bones has considerable share 
in the articulation ; but as we rise in the series, the surface of at- 
tachment of the lesser bones, the fibula in the foot, and the ulna 
in the hand, becomes successively smaller, until in the ruminants 
the fibula is almost obliterated, its distal end remaining as a small 
tuberosity coossified to the side of the end of the tibia. In the 
same manner the articular end of the ulna in the fore leg is suc- 
cessively reduced, until this bone also becomes a thin strip coossi- 
fied to the lower side of the radius, with no distinct termination. 


h'lQ. 2. 

Fig. 4. 

kai' f i pi 

Fig. 6. 

j^ ai aV pi 


Fig. 7. 

Fig. 8. 

ae y 





Fig. 9. 

Fig. 10. 

Fifr. 1, Mioclnenus corrugatm, superior molars. Fijr. 2, Pantolamhda hntJimndon^ 
superior true molars. Fig. 3, Phenacodus prirrnxvus, superior molar. Fig. 4, do. interior 
molar. Fig. ."), Lamhdotherium popoa(ficitm, superior molar. Fig. 6, do. inferior molar. 
Fig. 7, Anchitherinm aurelianenne, superior molar. Fig. 8, Hippotheriitm gradle^ infe- 
rior molar. Fig. 9, superior molar young crown of a Hippotherium. Fig. 10, superior 
molar of Equus. Figs. 1, 2, 5, 6, n-om Cope ; 3, 4, from Wortman ; the others from 


in both the horse and the ox. In the foetus these bones are well 

The dentition tells as clearly as possible the same story. Here, 
again, as I have pointed out in a paper on the "Homologies and 
Origin of the Types of Dentition of the Mammalia Educahilia,'"' 
the most specialized forms of dental structure are presented by the 
horse, the ox, and the tiger. But they are all modifications of a 
single type of tooth, viz., an oval crown supporting four tubercles 
on the summit, in the lower jaw, and three or four in the upper 
Jaw. In the lower cutting molar of the cat but one of these tu- 
bercles remains, forming with another in front of it a double shear 
blade, whose development may be traced from its earliest begin- 
nings in the genera of the Eocene. In the odd-toed forms (tapir, 
rhinoceros, etc.) the tubercles become connected transversely, 
forming cross-crests, and the outer ones are generally flattened on 
the outer side. In the horse the tubercles have a very complex 
form, and the spaces between them filled by a peculiar substance, 
the cementum. In the ruminants the tubercles come to have a 
crescent-shaped section and are drawn out to an enormous length, 
forming a j)rismatic tooth : here, also, the intervening deep valleys 
are filled with cementum. In the third series, that of the ele- 
phant, the original tubercles (permanently separate in the masto- 
dons) are connected into cross-crests, which are drawn out to a 
great length, and as in the other series are supported by a deposit 
of hard cementum in the intervening valleys. The transitions be- 
tween these and the primitive four-tubercled molar are numerous 
and direct. 

There is not now opportunity to consider the question of tran- 
sition from type to type by descent, further than to indicate by a 
few examples the manner in which it has evidently occurred. 
This has been by unequal growth of parts during foetal life, ac- 
cording to the laws of acceleration and retardation. The union 
of the two basal bones of toes into a single one (the "cannon- 
bone ") in the ruminants, is accomplished by the more and more 
rapid completion of the process of ossification in the growth of 
those bones ; the confluence of the various carpal and tarsal bones 
in various orders has the same history. In many genera it has 
been observed that the milk dentition has resemblances to other 
and older dentitions, which entirely disappear in the permanent 
teeth. This is the case with CorypJiodon and Equus ; while it 
may be observed in the kitten, whose sectorial milk-tooth has the 



heel belonging to all the lower and primitive Carnivora which is 
wanting from the sectorial of the adult cat. Moreover, in complex 
teeth, the different stages of wear represent primitive conditions 
of the same animal, elsewhere preserved to us in extinct adult 
genera and species. 

Forms which violate the definitions of the orders above given 
are also well known. Thus Mesonyx, with the skull and denti- 
tion of a carnivore, has the separate scaphoid and lunar bones and 
flat claws or hoofs of an ungulate. Calamodon has the molars 
of an ungulate, the incisors of a rodent, and claws resembling 
somewhat those of a carnivore. Uintatherium has feet partly like 
an elephant, and teeth of a tapir. 

I have referred the Mammalia with five and four toes, the full 
number of distinct tarsal and carpal bones, which form interlock- 
ing series, and in which the tread is plantigrade, to a new order 
called the Amhlypoda. These represent the primitive type of the 
higher Mammalia with convoluted brains, etc., but present much 
variation in the constitution of the teeth. From the latter have 
come off not only the three hoofed-orders represented by the ele- 
phant, the horse, and the ox, but the origin of the Carnivora and 
Quadrumana is scarcely distinguishable from it, if at all ; while 
there is little doubt that the natatory jSire7iian order was derived 
from it by a process of degradation, chiefly of the extremities, in 
connection with the assumption of an aquatic life. The mana- 
tee, of which a fine example may now be seen in our zoological 
gardens, represents this division. 

The relation of man to this history is highly interesting. Thus 
in all general points his limbs are those of the primitive type so 
common in the Eocene. He is plantigrade, has five toes, separate 
carpals and tarsals ; short heel, rather flat astragalus, and neither 
hoofs nor claws, but something between the two. The bones of 
the forearm and leg are not so unequal as in the higher types, and 
remain entirely distinct from each other, and the ankle-joint is 
not so perfect as in many of them. In his teeth his character is 
thoroughly primitive. He possesses, in fact, the original quadri- 
tuberculate molar with but little modification. His structural 
superiority consists solely in the complexity and size of his brain. 
The forms of the quadrumanous order, while agreeing with each 
other in most respects, display the greatest range of brain struct- 
ure, and show that while they have made but little progress since 
the Eocene in perfection of organization of the skeleton, they 


Fig. 7. 

Fig. 1. 

Fig. 4. 

Fig. 5. 

Fig. 6. 


Comparison between the Dentition of toe LEinm Anaptomorphus and Man. 

Fig. 1, skull of Anaptomorphus homuncjtlus, natural size. Fig. 2, same, oblique 
view, displaying the large cerebral hemispheres ; compare Plate XIV for relatively small 
size in a contemporary (Fig. 3) or a successor in time (Fig. 2). Fig. 3, superior view of 
skull, natural size. Fig. 4, inferior view, Vj natural size. Figs. 5, 6, and 7, left branch of 
lower jaw of Anaptomorphus a'mulus, fwico natural size; 5, from left side ; 6, inner 
side ; 7, from above. Fig. 8, superior dentition of Homo sapiens (from Allen), natural 


accomplished a much greater work, the evolution of the human 
brain and its functions. 

A very important lesson is derived from these and kindred facts. 
The monkeys were anticipated in the greater fields of the world's 
activity by more powerful rivals ; the ancestors of the ungulates 
held the fields and the swamps, and the Carnivora, driven by hun- 
ger, learned the arts and cruelty of the chase. The weaker an- 
cestors of the Quadrumana possessed neither speed nor weapons 
of offense and defense, and nothing but an arboreal life was left 
them, where they developed the prehensile powers of the feet. 
Their digestive system unspecialized, their food various, their life 
the price of ceaseless vigilance, no wonder that that quality of in- 
quisitiveness and wakefulness was stimulated and developed which 
is the condition of progressive intelligence. So " the race has not 
been to the swift nor the battle to the strong" : the "survival of 
the fittest" has been the survival of the most intelligent, and 
natural selection proves to be, in its highest animal phase, intel- 
ligent selection. 




The ability to read character in the form of the human face 
and figure is a gift possessed by comparatively few persons, al- 
though most people interpret, more or less correctly, the salient 
points of human expression. The transient appearances of the 
face reveal temporary phases of feeling which are common to all 
men ; but the constant qualities of the mind should be exjDressed, 
if at all, in the permanent forms of the executive instrument of 
the mind, the body. To detect the peculiarities of the mind by 
external marks has been the aim of the physiognomist of all 
times ; but it is only in the light of modern evolutionary science 
that much progress in this direction can be made. The mind, as 
a function of part of the body, partakes of its perfections and its 
defects, and exhibits parallel types of development. Every pecu- 
liarity of the body has probably some corresponding significance in 
the mind, and the causes of the former are the remoter causes of 
the latter. Hence, before a true physiognomy can be attempted, 
the origin of the features of the face and general form must be 
known. Not that a perfect physiognomy will ever be possible. A 
mental constitution so complex as that of man can not be expected 
to exhibit more than its leading features in the body ; but these 
include, after all, most of what it is imjjortant for us to be able to 
read from a practical point of view. 

The present essay will consider the probable origin of the 
structural points which constitute the permanent expression. 
These may be divided into three heads, viz. : (1) Those of the 
general form or figure ; (2) those of the surface or integument of 
the body with its appendages ; and (3) those of the forms of the 

* Abstract of a lecture delivered before the Franklin Institute of Philadelphia, 
January 20, 1881, in exposition of principles laid down in "The Hypothesis of Evo- 
lution," New Haven, 1870, p. 31. 


head and face. The principal j^oints to be considered under eacJi 
of these heads are the following : 

/. The General Form. 

1. The size of the head. 

2. The squareness or slope of the shoulders. 

3. The length of the arms. 

4. The constriction of the waist. 

5. The width of the hips. 

6. The length of the leg, principally of the thigh. 

7. The sizes of the hands and feet. 

8. The relative sizes of the muscles. 

//. Tlie Surfaces. 

9. The structure of the hair (whether curled or not). 

10. The length and position of the hair. 

11. The size and shape of the nails. 

12. The smoothness of the skin. 

13. The color of the skin, hair, and irides. 

III. The Head and Face. 

14. The relative size of the cerebral to the facial regions. 

15. The prominence of the forehead. 

16. The prominence of the superciliary (eyebrow) ridges. 

17. The prominence of the alveolar borders (jaws). 

18. The prominence and width of the chin. 

19. The relation of length to width of skull. 

20. The prominence of the malar (cheek) bones. 

21. The form of the nose. 

22. The relative size of the orbits and eyes. 

23. The size of the mouth and lips. 

The significance of these, as of the more important structural 
characters of man and the lower animals, must be considered from 
two standpoints, the paleontological and the embryological. The 
immediate paleontological history of man is unknown, but may 
be easily inferred from the characteristics displayed by his nearest 
relatives of the order Quadrumana. If we compare these animals 
with man, we find the following general differences. The num- 
bers correspond to those of the list above given. 




/. As to General Form. — (3) In the apes the arras are longer ; 
(8) the extensor muscles of the leg are smaller. 

//. As to Surface. — (9) The body is covered with hair which 
is not crisp or woolly ; (10) the hair of the head is short ; (13) the 
color of the skin, etc., is dark. 

///. As to Head and Face. — (14) The facial region of the 
skull is large as compared with the cerebral ; (15) the forehead is 

Fig. 52. — Section of skull of adult oranff-outan<r (Simia satyrus). a, section of 
skull of youug oraug, showing relatively sliortei' jaws and more prominent cei'ebral 

not prominent, and is generally retreating ; (16) the superciliary 
ridges are more prominent ; (17) the edges of the jaws are more 
prominent ; (18) the chin is less prominent ; (20) the cheek-bones 
are more prominent ; (21) the nose is without bridge, and with 
short and flat cartilages ; (22) the orbits and eyes are smaller 
(except in Xyctipithecus) ; (24) the mouth is small and the lips 
are thin. 

It is evident that the possession of any one of the above char- 
acteristics by a man approximates him more to the monkeys, so 


far as it goes. He retains features which have been obliterated in 
other persons in the process of evolution. 

In considering the physiognomy of man from an embryologieal 
standpoint, we must consider the peculiarities of the infant at 
birth. The numbers of the following list correspond with those 
already used (Fig. 53). 

/. As to the General Form. — (1) The head of the infant is rel- 
atively much larger than in the adult ; (3) the arms are relatively 

longer 5 (4) there is no waist; 
(6) the legs, and especially 
the thighs, are much shorter, 
//. As to the Surfaces. — 
(10) The body is covered with 
fine hair, and that of the 
head is short. 

///. The Head atid Face. 
— (14) The cerebral part of 
the skull greatly predomi- 
nates over the facial ; (16) 
the superciliary ridges are 
not developed ; (17) the al- 
veolar borders are not prom- 
inent ; (20) the malar bones 
are not prominent ; (21) the 
nose is without bridge and 
the cartilages are flat and 
generally short ; (22) the 
eyes are larger. 

It is evident that per- 
sons who present any of the 
characters cited in the above 
list are more infantile or em- 
bryonic in those respects than 
are others ; and that those who lack them have left them behind 
in reaching maturity. 

We have now two sets of characters in which men may differ 
from each other. In the one set the characters are those of monk- 
eys, in the other they are those of infants. Let us see whether 
there be any identities in the two lists, i. e., whether there be any 
of the monkey-like characters which are also infantile. We find 
the following to be such : 

Fig. 53.- 
of face. 

-Figure of infant at birth ; a, front 

'«! I 



I. As to General Form. — (3) The arms are longer. 

//. Surface. — {10) The hair of the head is short, and the hair 
on the body is more distributed. 

///. As to Head and Face. — (21) The nose is without bridge, 
and the cartilages are short and flat. 

Three characters only out of twenty-three. On the other hand, 
the following characters of monkey-like significance are the oppo- 
sites of those included in the embryonic list : (14) The facial re- 
gion of the skull is large as compared with the cerebral ; (15) the 
forehead is not prominent ; (16) the superciliary ridges are more 

u: ji; 

J-. - 

¥io. 54. 


t'lo, 55. 

Fig. 54. — Portrait of a girl at five years of age. Fig. 55. — Portrait of the same at 
seventeen years, showing the elongation of the facial region, and less protuberance of 
the cerebral. 

prominent ; (17) the edges of the jaws are more prominent. Four 
characters, all of the face and head. It is thus evident that in at- 
taining maturity man resembles more and more the apes in some 
important parts of his facial expression. 

It must be noted here that the difference between the young 
and embryonic monkeys and the adults is quite the same as those 
just mentioned as distinguishing the young from the adult of man 
(Figs. 1-2). The change, however, in the case of the monkeys is 
greater than in the case of man. That is, in the monkeys the 
jaws and superciliary ridges become still more prominent than in 


1 1 Ml HP >IU Pip 

Esequibo Indian women, showing the following peculiarities : deficient bridge of 
nose, prognathism, no waist, and deliciency of stature through short femur. From 
photographs by Endlich. 



man. As these characters result from a fuller course of growth 
from the infant, it is evident that in these respects the aj^es are 
more fully developed than man. Man stops short in the develop- 
ment of the face, and is in so far more embryonic* The promi- 
nent forehead and reduced Jaws of man are characters of "retar- 
dation." The characters of the prominent nose, with its elevated 
bridge, is a result of "acceleration," since it is a superaddition to 
the quadrumanous type from both the standpoints of paleontology 
and embryology.f The development of the bridge of the nose is 
no doubt directly connected with the development of the front of 
the cerebral part of the skull and ethmoid bone, which sooner or 
later carries the nasal bones with it. 

If we now examine the leading characters of the physiognomy 
of three of the principal human sub-species, the Negro, the Mon- 

FiG. 56 

Fig. 56. — Profile of a Lueliatze negro woman, sLowinG: deficient bridge of nose and 
chin, and elongate facial region and prognathism. Fio. 57. — Face of another Luchatze, 
showing flat nose, less prognathism and larger cerebral region. From Serpa Pinto. 

golian, and the Indo-European, we can readily observe that it is 
in the two first named that there is a predominance of the quad- 
rumanous features which are retarded in man ; and that the em- 
bryonic characters which predominate, are those in which man is 

* This fact has been well stated by C. S. Slinot, in the "Naturalist" for 1882, 
p. 511. 

t See Cope, "The Hypothesis of Evolution," New ITaven, 18v0, p. 31. 



accelerated. In race description the prominence of the edges of 

the jaws is called prognathism, and its absence orthognathism. 

The significance of the two lower race characters, as compared 

with those of the Indo-European, is as follows : 

■ Negro. — Hair crisp (a special character), short (qnadrum. ac- 

cel.) ; prognathous (qnadrum. accel.) ; nose flat, without bridge 

(qnadrum. retard.) ;* malar bones prominent (qnadrum. accel.) ; 

beard short (qnadrum. retard.); arms longer (quadrum. accel.); 

extensor muscles of legs small (quadrum. retard.). 

Mongolian. — Hair straight, long (accel.) ; jaws prognathous 

(quadrum. accel.) ; nose flat or prominent, with or without bridge ; 

malar bones prominent 
(quadrum. accel.); beard 
none (embryonic) ; arms 
shorter (retard.) ; extensor 
muscles of leg ("calf") 
smaller (quad, retard.). 

Indo-European. — Hair 
long (accel.) ; jaws orthog- 
nathous (embryonic re- 
tard.) ; nose (generally) 
prominent with bridge 
(accel.) ; malar bones re- 
duced (retard.) ; beard 
long (accel. ) ; arms shorter 
(retard.); extensor mus- 
cles of the leg large (accel.). 
The Indo - European 
race is then the highest by 
virtue of the acceleration 
of growth in the develop- 
ment of the muscles by 
which the body is main- 
tained in the erect position 

Fig. 58.— Portrait of Satanta, a late chief of the (cxtenSOrs of the leg), and 

Kiowas (from the Red River of Texas'), from a jj^ those imnortant ele- 
photofrraph. The predominance of the fiicial re- 4- f i + 

gion, and especially of the malar bones, and the ^^^ntS Ot bCauty, a WCll- 

absence of beard, are noteworthy. developed UOSe and beard. 

* In the Boehimans, the flat nasal bones are coossified with the adjacent ele- 
ments as in the apes (Thulie). 


The Wrestler; orif,nnal in the Vaticivn. Tliia figure displays the characters of the 
male Indo-European, except the beard. 


It is also superior in those points in which it is more embryonic 
than the other races, viz., the want of prominence of the Jaws 
and cheek-bones, since these are associated with a greater predom- 
inance of the cerebral part of the skull, increased size of cerebral 
hemispheres, and greater intellectual power. 

A comparison between the two sexes of the Indo-Europeans 
expresses their physical and mental relations in a definite way. I 
select the sexes of the most civilized races, since it is in these, ac- 
cording to Broca and Topinard, that the sex characters are most 
pronounced. They may be contrasted as follows. The numbers 
are those of the list on page 282, already used. I first consider 
those which are used in the tables of embryonic, quadrumanous, 
and race characters : 


/. The General Form. 
2. Shoulders square. Shoulders sloped. 

4. Waist less constricted. Waist more constricted. 

5. Hips narrower. Hips wider. 

6. Legs longer. Legs shorter (very frequently). 
8. Muscles larger. Muscles smaller. 

//. The Integuments, etc. 

10. More hair on body, that of head Less hair on body, that of head longer ; 

shorter ; beard. no beard. 

12. Skin rougher (generally). t Skin smoother. 

III. TJie Head and Face. 

16. Superciliary ridges more prominent. Superciliary ridges low. 
22. Eyes often smaller. Eyes often larger. 

The characters in which the male is the most like the infant 
are two, viz., the narrow hips and short hair. Those in which the 
female is most embryonic are five, viz., the shorter legs, smaller 
muscles, absence of beard, low superciliary ridges, and frequently 
larger eyes. To these may be added two others not mentioned in 
the above lists ; these are (1) the high-pitched voice, which never 
falls an octave as does that of the male ; and (2) the structure o 
the generative organs, which in all Mammalia more nearly resem- 
ble the embryo and the lower Vertebrata, in the female than in the 
male. Nevertheless, as Bischoff has jDointed out, one of the most 
important distinctions between man and the apes is to be found 
in the external reproductive organs of the female. 

From the preceding summary sketch the reader will be able to 
explain the meaning of most of the iieculiarities of face and form 



which he will meet with. Many persons possess at least one quad- 
rumanous or embryonic character. The strongly convex upper lip 
frequently seen among the lower classes of the Irish is a modified 
quadrumanous character. Many people, especially those of the 
Sclavic races, have more or less embryonic noses. A retreating 
chin is a marked monkey character. Shortness of stature is mostly 

Fig. 59. — Australian native (from Brough Smyth), showing small development oi 
muscles of legs, and prognathism. 

due to shortness of the femur, or thigh ; the inequalities of people 
sitting are much less than those of people standing. A short femur 
is embryonic ; so is a very large head. The faces of some people 
are partially embryonic, in having a short face and light lower 
jaw. Such faces are still more embryonic when the forehead and 
eyes are protuberant. Ectardation of this kind is most frequently 



tfriT'f'rri^'-''"-'"-'*-*^''"'"^'"-''''"*'''^"'*''-— ^^^^ 

The Venus of the Capitol (Eome). The form and face present the cliaracteristic 
peculiarities of the female of the Indo-European race. 


seen in children, and more frequently in women than in men. The 
length of the arms would appear to haye grown less in compar- 
atively recent times. Thus the humerus in most of the Greek 
statues, including the Apollo Belyidere, is longer than those of 
modern Europeans, according to a writer in the "Bulletin de la 
Societe d'Anthropologie " of Paris, and resembles more nearly that 
of the modern Nubians than any other people. This is a quad- 
rumanous approximation. The miserably developed calves of ~^ 
many of the savages of Australia, Africa, and America, are well 
known. The fine swelling gastrocnemius and soleus muscles char- 
acterize the highest races, and are most remote from the slender ^ 
shanks of the monkeys. The gluteus muscles developed in the 
lower races as well as in the higher, distinguish them well from 
the monkeys with their flat posterior outline. 

It must be borne in mind that the quadrumanous indications 
are found in the lower classes of the most developed races. The 
status of a race or .amily is determined by the percentage of its 
individuals who do and do not present the features in question. 
Some embryonic characters may also appear in individuals of any 
race, as a consequence of special circumstances. Such are, how- 
ever, as important to the physiognomist as the more normal vari- 

Some of these features have a purely i')hysical significance, but 
the majority of them are, as already remarked, intimately con- 
nected with the development of the mind, as an effect or necessary 
coincidence. I will examine these relations in a future article. 



The subject to which I wish to call your attention this morn- 
ing requires neither preface nor apology, as it is one with the dis- 
cussion of which you are perfectly familiar. I bring it before the 
general session of the Association in view of the fact that you 
are all familiar with it in a general way, and that it probably in- 
terests the members of sections who do not pursue the special 
branch to which it refers, as well as those who do : also, since it 
has been brought before us in various public addresses for many 
years, during the meetings of this Association, I thought it might 
be well to introduce it at this meeting, in order that we might 
not omit to have all the sides of it presented. 

The interests which are involved in it are large : they are 
chiefly, however, of a mental and metaphysical character ; they 
do not refer so much to industrial and practical interests, nor do 
they involve questions of applied science. They involve, however, 
questions of opinion, questions of belief, questions which affect 
human hapj)iness, I venture to say, even more than questions of 
applied science ; certainly, which affect the happiness of the 
higher grades of men and women more than food or clothing, be- 
cause they relate to the states of our mind, explaining as they do 
the reasons of our relations to our fellow beings, and to all other 
things by which we are surrounded, and the general system of the 
forces by which we are controlled. So it has always aj)peared to 
me : hence I have selected the department of biology for study, 
and have taken a great interest in this aspect of it. 

The doctrine of evolution, as taught by the biologists of to- 
day, has several stages or parts of its presentation. First, the 
foundation princij)le is this : that the species of animals and of 

* An address delivered before the American Association for the Advancement of 
Science, 1883. 


plants, the species of organic beings, as well as the various natu- 
ral divisions into which these organic beings fall, have not always 
been as we see them to-day, but they have been produced by a 
process of change which has progressed from age to age through 
the influence of natural laws ; that, therefore, the species which 
now exist are the descendants of other species which have existed 
heretofore, by the ordinary processes of reproduction ; and that 
all the various structures of organic beings, which make them 
what they are, and which compel them to act as they now act, 
are the result of gradual or sudden modifications and changes 
during the periods of geologic time. That is the first phase or 
aspect which meets the naturalist or biologist. 

Another phase of the question relates to the origin of that life 
itself which is supposed to inhabit or possess organic beings. 
There is an hypothesis of evolution which derives this life from 
no-life, which derives vitality from non- vitality. This is another 
branch of the subject, tt) which I can not devote much attention 

There is still another department of the subject, which relates 
to the origin of mind, and which derives the mental organization 
of the higher animals, especially of man, from pre-existent tj^es 
of mental organization. This gives us a genealogy of mind, a his- 
tory of the production or creation of mind, as it is now presented 
in its more complex aspects as a function of the human brain. 
This aspect of the subject is, of course, interesting ; and upon 
it I can touch with more confidence than upon the question of 
the origin of life. 

Coming now to the question of the origin of structures, we 
have by this time accumulated a vast number of facts which have 
been collated by laborious and faithful workers, in many countries 
and during many years ; so that we can speak with a good deal of 
confidence on this subject also. As to the phenomena which 
meet the student of zoology and botany at every turn, I would 
merely repeat what every one knows — and I beg pardon of my bio- 
logical friends for telling them a few well-known truths, for there 
may be- those present who are not in the biological section — the 
phenomena which meet the student of biology come under two 
leading classes. The first is the remarkable fidelity of species in 
reproducing their like. ''Like produces like," is the old theo- 
rem, and is true in a great many cases ; just as coins are struck 
from the die, just as castings are turned out from a common 


mold. It is one of the most wonderful phenomena of nature, 
that such complex organisms, consisting of so many parts, should 
be repeated from age to age, and from generation to generation, 
with such surprising fidelity and precision. This fact is the first 
that strikes the student of these sciences. The first impression 
of the ordinary person would be, that these things must continue 
unchanged. When I began to study zoology and botany, I was 
surprised to find there was a science of which I had no concep- 
tion, and that was this remarkable reproduction of types one 
after another in continued succession. After a man has had 
this idea thoroughly assimilated by his honest and conscien- 
tious studies, he will be again struck with another class of 
facts. He will find, not unfrequently, that this doctrine does 
not apply. He will find a series of facts which show that many 
individuals fail to coincide with their fellows precisely, the most 
remarkable variations and the most remarkable half-way atti- 
tudes and double-sided aspects occurring ; and he will come to 
the conclusion, sooner or later, that like does not produce like in 
some animals with the same precision and fidelity with which it 
is accomplished in other animals. So that we have these two 
classes of facts — the one relating to, and expressing, the law of 
heredity ; the other which expresses the law of variation. I 
should not like to say which class of facts is the most numerously 
presented to the student. In the present fauna we find many 
groups of species and varieties ; but exactly how many species we 
have, how many genera and families we have, we can not defi- 
nitely state. The more precise and exact a person is in his defini- 
tion and in his analysis, the more definite his science becomes, 
and the more precise and scientific his work. Biology is a science 
of analvsis of forms. What the scales are to the chemist and the 
physicist, the rule and measure are to the biologist. It is a ques- 
tion of dimension, a question of length and breath and thickness, 
a question of curves, a question of crooked shapes or simple 
shapes — rarely simple shapes, mostly crooked, generally bilateral. 
It requires that one should have a mechanical eye, and should 
have also something of an artistic eye, to appreciate these forms, 
to measure them, and to be able to compare and weigh them. 

Now, when we come to arrange our shapes and our measure- 
ments, we find, as I said before, a certain number of identities, 
and a certain number of variations. This question of variation 
is so common and so remarkable, that it becomes perfectly evi- 


dent to the specialist in each department, that like does not at 
all times produce like. It is perfectly clear, and I will venture 
the assertion that nearly all the biologists in this room will bear 
me witness, that variability is practically unlimited in its range, 
and multiplied in the number of its examples. That is to say : 
species vary by adding or by failing to retain certain characteris- 
tics ; and generic and other characters are found to appear or 
disappear in accordance with some law to be discussed farther on/ 

I believe that this is the simplest mode of stating and explain- 
ing the law of variation : that some forms acquire something 
which their parents did not possess ; and that those which ac- 
quire something additional have to pass through more numerous 
stages than their ancestors ; and those which lose something pass 
through fewer stages than their ancestors ; and these processes are 
expressed by the terms "acceleration " and "retardation." 

Of course we are met with the opposite side of the case — the 
law of heredity. We are told that the facts there are not ac- 
counted for by any law of evolution ; that we can not pass from 
one class of facts to the other class of facts ; that the law of the 
one class is not that of the other. Here is a question of rational 
processes, of ordinary reason. If the rules of chemistry are true 
in America, I imagine they are true in Australia and Africa, al- 
though I have not been there to see. If the law of gravitation is 
effective here, I do not need to go to Australia or New Zealand 
to ascertain whether it be true there. So, if we find in a group 
of animals a law sufficient to account for their creation, it is not 
necessary to know that others of their relatives have gone through 
a similar process. I am willing to allow the ordinary practical 
law of induction, the practical law of inference, to carry me over 
these gaps, over these interruptions. And I state the case in this 
way, because it is just here that some people differ from me, and 
it is just here that I say the simple question of rationality comes 
in. I can not believe that Nature's laws are so dissimilar, so 
irregular, so inexact, that those which we can see and understand 
in one place are not true in another ; I also believe that the ques- 
tion of geological likelihood is similar to the question of geo- 
graphical likelihood. If a given process be true in one of the 
geological periods, it is true in another ; if it be true in one part 
of the world, it is true in another ; because I find interruptions 
in the series here, it does not follow that there need be interrup- 
tions clear through from age to age. The assumption is on the 


side of the man who asserts that transitions have not taken place 
between forms which are now distinct. 

We are told that we find no sort of evidence of that transition 
in past geological periods ; we are assured that such changes have 
not taken place ; we are even assured that no such sign of such 
transition from one species to another has ever been observed — a 
most astonishing assertion to make to a biologist, or by a biolo- 
gist ; and such persons have even the temerity to cite such a 
special case as that between the wolf and the dog. Many of our 
domestic dogs are nothing but wolves, which have been modified 
by the hand of man to a very slight extent indeed. Many dogs, 
in fact nearly all dogs, are descendants of wild species of various 
countries, and are variously modified. 

To take the question of the definition of species. Supposing 
we have several species well defined, say four or five. In the 
process of investigation we obtain a larger number of individuals, 
many of which betray characters which invalidate the definitions. 
It becomes necessary to unite the four or five species into one. 
And so, then, because our system requires that we shall have ac- 
curate definitions (the whole basis of the system is definitions ; 
you know the very comprehension of the subject requires defini- 
tions), we throw them all together, because we can not define all 
the various special forms as we did before, until we have but one 
species. And the critic of the view of evolution tells us, "1 told 
you so ! There is but one species, after all. There is no such 
thing as a connection between species : you never will find it." 
Now, how many discoveries of this kind will be necessary to con- 
vince the world that there are connections between species ? How 
long are we to go on finding connecting links, and putting them 
together, as we have to do for the sake of the definition, and then 
be told that we have, nevertheless, no intermediate forms between 
species ? The matter is too plain for further comment. We 
throw them together, simply because our definitions require it. 
If we knew all the known individuals which have lived, we should 
have no species, we should have no genera. That is all there is 
of it. It is simply a question of a universal accretion of material, 
and the collection of information. I do not believe that the well- 
defined groups will be found to run together, as we call it, in any 
one geological period, certainly in no one recent period. We 
recognize, however, in looking backward, that they converge to 
a wonderful extent : one group has diverged at one period, and 


another one has become diversified in a different period ; and so 
each one has its history, some beginning farther back than others, 
some reaching far back beyond the very beginning of the time 
when fossils could be preserved. I call attention to this view be- 
cause it is a very easy matter for us to use words for the purpose 
of confusing the mind ; for, next to the power of language to ex- 
press clear ideas, is its power of expressing no ideas at all. As we 
all know, we can say many tilings which we can not tliiiik. It is 
a very easy thing to say twice two are equal to six, but it is im- 
possible to think it. 

I would cite what I mean by variations of species in one of its 
phases : I mention a genus of snakes, Ophibolus, which is found 
in the United States. If we take the species of this snake-genus 
as found in the Northern States, we have a good many species well 
defined. If we go to the Gulf States, and examine our material, 
we see we have certain other species well defined, and they are 
very nicely distinguished. If, now, we go to the Pacific coast, to 
Arizona and New Mexico, we shall find another set of species 
well defined indeed. If we take all these different types of our 
specimens of different localities together, our species, as the Ger- 
mans say, all tumble together : definitions disa^jpear, and we have 
to recognize, out of the preliminary list of thirteen or fourteen, 
only four or five. That is simply a case of the kind of fact with 
which every biologist is perfectly familiar. 

When we come to the history of the extinct forms of life, it is 
perfectly true that we can not observe the process of descent in 
actual operation, because, forsooth, fossils are necessarily dead. 
We can not perceive any activities, because fossils have ceased to 
act. But, if this doctrine be true, we should get the series, if 
there be such a thing ; and we do, as a matter of fact, find longer 
or shorter series of structures, series of organisms proceeding from 
one form into another form, which are exactly as they ought to 
be if this process of development by descent had taken jjlace. 

I am careful to say this ; because it is literally true, as we all 
must admit, that species must fall into some kind of order or 
other. You could not collect bottles, you could not collect old 
shoes, but you could make some kind of a serial order of them. 
There are, no doubt, characters by which such and such shoes 
could be distinguished from other shoes, these bottles from other 
bottles. But if serial order does not prove evolution, as is too 
often assumed, we have in recent forms of life in zoology and 



botany, irrefragable proofs of the metamorphoses, and transfor- 
mations, and changes of the species, in accordance with the doc- 
trine with which we commenced. 

We now come to the second chapter of our subject. With the 
assumption, as I take it ah-eady satisfactorily proved, of species 
having changed into others, in considering this matter of geo- 
logical succession or biological succession, I bring you face to face 
with the nature and mode of the change ; and hence we may get 
a glance perhaps at its laws. 

I have on the board a sketch or table which represents the 
changes which took place in certain of the Mammalia. I give you 
a summary of the kind of thing which we find in one of the 
branches of paleontology. I have here two figures, one represent- 
ing a restoration, and the other an actual picture, of two extinct 
species that belong to the early Eocene periods. One represents 
the ancestor of the horse line, Hyracotherium, which has four toes 
on his anterior feet, and three behind ; and the other (Plate XIII) 
a type of animal, Phenacodus, which is antecedent to all the horse 
series, the elephant series, the hog, the rhinoceros, and all the other 
series of hoofed animals. It has five toes on all the feet. Each 
presents us with the primitive position in which their series first 
come to our knowledge in the history of geological time. 

I have also arranged here a series of some leading forms of the 
three principal epochs of the Mesozoic times, and six of the lead- 
ing ones of the Tertiary time. I have added some dates to show 
you the time when the faunae which are entombed in those beds 
were discovered, in the course of our studies ; and you will easily 
see how unsafe it is to say that any given type of life has never ex- 
isted, or even to assert that such and such a form is unknown ; 
and it is still more unsafe, I think, to assert that any given form 
of life properly defined, or that a specific intermediate form of life, 
will not be found. I think it is much safer to assert that such and 
such intermediate forms will be found. I have frequently had the 
pleasure of realizing anticipations of this kind. I have asserted 
that certain types would be found, and they have been found. 
You will see that I attend to the matter of time because there have 
been a great many things discovered in the last ten or fifteen years 
in this department. Witli these forms I give the date of the dis- 
covery of the fauna in which they are embraced. 

Here we have the White River fauna discovered in 1850 ; then 
we skip a considerable period of time, and the next one was in 18G9, 


when the Cretaceous series was found. Six or seven Cretaceous 
faunae have been discovered. Then we have the Bridger fauna in 
1870, the Wasatch fauna in 1874. Next we have, in 1877, the 
Equus beds and the fauna which they embrace, part of which was 
also found in 1878. The Permian fauna, which is one of the last, 
in 1879 ; and the latest, the Puerco, which gives the oldest and 
ancestral types of the modern forms of Mammalia, was only found 
in 1881. When I first commenced the study of this subject, about 
1860, there were perhaps two hundred and fifty species known. 
There are now somewhere above 1,000, and we are augmenting 
them all the time. I have found many myself : if they were dis- 
tributed through the days of the year, I think in some months I 
should have had several every day. You see then that the acces- 
sions to knowledge which are constantly being made make it un- 
safe to indulge in any prophecies ; as, for instance, that, because 
such and such things have not been found, therefore they can not 
be ; for we find such and such things really have been and really 
are discovered. 

The successive changes that we have in the Mammalia have 
taken place in the limbs, feet, teeth, and brain, and the vertebral 
column. The parts which present us with the greatest numbers 
of variations are those in which many parts are concerned, as in 
the limbs and feet. In the Lower Eocene (Puerco), the toes were 
5-5. In the Loup Fork fauna, some possess toes but 1-1. Prior 
to this period no such reduction was known, although in the Loup 
Fork fauna a very few species remained 5-5. Through this en- 
tire series we have transitions steady and constant, from 5-5, to 4- 
5, to 4-4, to 4-3, to 3-3, to 2-3, to 1-1. In the Puerco period there 
was not a single mammal of any kind which had a good ankle-joint ; 
which had an ankle-joint constructed as ankle-joints ought to be, 
with tongue and groove. The model ankle-joint is a tongue-and- 
groove arrangement. In this period they were nearly all perfectly 
flat. As time passes on we get them more and more grooved, un- 
til in the Loup Fork fauna and the White River fauna they are near- 
ly all grooved. The soles of the feet, in the Puerco fauna, are 
all flat ; but in the Loup Fork fauna the soles of the feet are in 
the air, and the toes only are applied to the ground, with the excep- 
tion of the line of monkeys, in which the feet have not become erect 
on the toes, and the elephant, in which the feet are nearly flat also, 
and the line of bears, where they are also flat. As regards the 
angulation between the small bones of the palm and of the sole, 






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there is not a single 
instance in which those 
bones are locked in the 
Lower Eocene, as they 
are in the later and 
latest Tertiary. So 
also with the articula- 
tion of the toes with 
the foot. 

When we come to 
the limbs, the species 
of the Puerco fauna 
have short legs. They 
have gradually length- 
ened out, and in the 
late periods they are 
nearly all relatively 

Coming to the ver- 
tebrae as a part of the 
osseous system, I men- 
tion the zygapophyses, 
or anteroposteriorly 
directed processes, of 
which the posterior 
looks down and the an- 
terior looks up. They 
move on each other, as 
the vertebral column 
bends from side to 
side. In the lower 
forms of vertebrates 
they are always flat, 
and in the hoofed 
mammals of the Puer- 
co period they are all 
flat. In the Wasatch 
period we get a single 
group in which the 
articulation, instead of 
being perfectly flat, be- 


comes rounded ; in the later periods we get them very much 
rounded ; and, finally, in the latest forms, we get the double 
curve and the locking process in the vertebral column, which, 
as in the limb, secures the greatest strength with the greatest 

In the first stages of the growth of the spinal column, it is a 
notochord, or a cylinder of cartilage or softer material. In later 
stages the bony deposit is made in its sheath until it is perfectly 
segmented. Now, all the Permian laud-animals, reptiles and 
batrachians, retain this notochord with the elements of osseous 
vertebrae, in a greater or less degree of completeness. Tliere are 
some in South Africa, I believe, in which the ossification has come 
clear through the notochord ; but they are few. In this charac- 
teristic the Permian appears almost, perhaps absolutely, peculiar as 

Fig. 61. — Sleeve of a coat showing folds produced by lateral flexure whicli leaves 
interspaces similar to the segments of a rhachitomous vertebra. Thus, i represents in- 
tercentrum ; p, pleuro-centrum ; and n, neurapophysis. 

regards land-aniraals. There is something to be said as to the con- 
dition of the column from a mechanical standpoint, and it is this : 
that the chorda exists, with its osseous elements disposed about it ; 
and in the Permian batrachians, equally related to salamanders 
and frogs, these osseous elements are arranged in the sheath or 
skin of the chorda ; and they are in the form of regular concave 
segments, very much like such segments as you can take from the 
skin of an orange — but parts of a cylinder, and having greater or 
less dimensions according to the group or species. Now, the point 
of divergence of these segments is on the side of the column. The 
contacts are placed on the side of the column where the segments 
separate — the upper segments rising and the lower segments com- 
ing downward. To the upper segments are attached the arches 
and tlieir articulations, and the lower segments are like thd seg- 
ments of a cylinder. If you take a flexible cylinder, and cover it 
with a more or less inflexible skin or sheath, and bend that cylinder 



sidewise, you of course will find that the wrinkles or fractures of 
that part of the surface will take place along the line of the 
shortest curve, which is on the side ; and, as a matter of fact, you 
have breaks of very much the character of the segments of the Per- 
mian Batrachia. It may not be so symmetrical as in the actual 
animal, for organic growth is symmetrical so far as not interfered 
with ; for, when we have two forces, the one of hereditary growth, 
and the other of change or alteration, and they contend, you will 
find in the organic being a quite symmetrical result. That is the 
universal rule. In the cylinder bending both ways, of course the 
shortest line of curve is right at the center of the side of that cyl- 
inder, and the longest curve is of course at the summit and base, 
and the shortest curve will be the point of fracture. And that is 
exactly what I presume has happened in the case of the construc- 
tion of the segments of the sheath of the vertebral column, by the 
lateral motion of the animal in swimming, and which has been the 
actual cause of the disposition of the osseous material in its form. 
I have gone beyond the state of the discussion in calling attention 
to one of the forces which have probably produced this kind of 
result. That is the state of the vertebral column of many of the 
Vertebrata of the Permian period.* 

I go back to the Mammalia and call attention to the teeth. 
The ordinary tooth of the higher type of the Mammalia, whether 
hoofed or not, with some exceptions, is complex with crests or 
cusps. By cutting the complex grinding surfaces, we find they 
have been derived by the infolding of extensions of four original 
cusps or tubercles. They have been flattened, have been rendered 
oblique, have run together, have folded up, have become acute, 
have descended deeply, or have lifted themselves, so that we have 
teeth of all sorts and kinds, sometimes very elegant, and often- 

* Note (Ed. 1886). — Some further elucidation of this point is necessary, since the 
fishes have not produced this kind of segmentation by the lateral motions of the 
vertebral column in swimming ; at least, such segmentation is not yet known among 
them, but rather simple discoidal segmentation. The rhachitomous segmentation 
above described would result from a greater flexure than that required for the 
propulsion of a fish through the water. This increased flexure was no doubt the 
concomitant of the acquisition of a terrestrial mode of life by the early batrachians. 
Progression on land by an animal with weak limbs requires much greater flexure of 
the column than the act of swimming by the use of the caudal part of the body as 
in fishes. One can easily convince himself of this by comparing the movements of 
a fish in the water with those of a salamander on land. The snakes, where limbs 
are wanting, show an even stronger flexure in progression. 


times Yery effective in mechanism. In many primary ungulates, 
the primitive condition of four conical tubercles is found. In 
passing to older periods we find the Mammalia of the Puerco 
period, which never have more than three principal tubercles, 
with the exception of three or four species. In the succeeding 
periods, however, they get the fourth tubercle on the posterior 
side. Finally, you get a complicated series of grinding or cutting 
apparatus, as the case may be. 

Last, but not least, we take the series of the brain. No doubt 
the generalization is true, that the primitive forms of Mammalia 
had small brains with smooth hemispheres ; later ones had larger 
brains with comj^lex hemispheres. In general the Carnivora have 
retained a more simple form of brain, while herbivorous animals 
have retained a more complicated type of brain. The lowest 
forms of Mammalia display the additional peculiarity of having the 
middle brain exposed ; and the hemispheres or large lobes of the 
brain, which are supposed to be the seat of the mental phenomena, 
are so reduced in size at the back end, that you see the middle 
brain distinctly, though it is smaller than in reptiles and fishes. 
(See Plate XIV.) 

It is beyond the possibility of controversy, that these series 
have existed, that they have originated in simplicity and have re- 
sulted in complication ; and the further induction must be drawn, 
that the j^rocess of succession has been toward greater effective- 
ness of mechanical work. There are also cases of degradation, as 
in the growing deficiency in dentition in man. There is no doubt 
that a large number of people are now losing their wisdom-teeth 
in both jaws. 

We are now brought to the question of the relations which 
mind bears to these principles. The question as to the nature of 
mind is not so complex as it might seem. There is a great deal 
of it, to be sure ; but on examination it resolves itself into a few 
ultimate forms. An analysis reduces it to a few principal types or 
departments — tlie departments of the intelligence and of the emo- 
tions (with their primary simj^ler forms, likes and dislikes), and 
the will, if such there be. These three groups, proposed by Kant, 
are well known, and arc adopted by many metaphysicians ; and 
they stand the scrutiny of modern science as applied to botii men 
and the lower animals. But the question of the material of the 
mind, the original raw stuff out of which mind was made, is one 
which is claiming attention now from biologists, as it always has 




Fig. 1. 

Fig. 2. 

Fig. 3. Fig. 4. 

FiGUBEs OF Casts of Beain-Cii ambers of Extinct Mammalia. 

Ficr. 1, PeriptychxLS rTiabdodon, cast of roof of brain case, showing middle-brain hemispheres and 
part of olfactory lobes, natural size. Original ; from Puerco bed of New Mexico. Fig. 2, Uinta- 
therium, mirabile, one third natural size, from Marsh. From Bridger bed of Wyoming. Fig. 3, 
Phenacodus primcevvs^, one half natural size. Original ; from Wasatch bed of Wyoming. Fig. 4, 
Procamelus occidentalism one half natural size. Original ; from Loup Fork bed of New Mexico. 
Figs, a, profile ; 6, above ; c, below. 


done from physiologists proper, and physicians. This is sensi- 
bility, mere simple sensibility, unmodified sensation, or con- 
sciousness. Sensibility, in connection with memory, is sufficient 
for the accomplishment of wonderful results. It is only necessary 
to impress the sensibility with the stimuli which this world affords, 
whether from the outside or the inside, to have the record made, 
and to have the record kept. Among wonderful things this is 
perhaps the most wonderful : that a given form of matter should 
be able to retain a record of events, a record which is made during 
a greater or less degree of sensibility ; which is retained in a state 
of insensibility ; and is finally returned to the sensibility by some 
curious process of adhesion, as the results of im^jresses which are 
found on the material tissue concerned. 

And these simple elements of mind are found in animals. No 
zoologist who has perception or honesty, nor any farmer or 
breeder, nor any person who has charge of animals in any way, 
can deny sensibility to all the lower animals at times. The great 
stumbling-block in the way of the thinker in all this field, is the 
great evanescence of this sensibility ; the great ease with which 
we dissipate it. The readiness with which we can deprive a fel- 
low-being of his sense is a stumbling-block in more ways than one. 
While it is a question of the greatest difficulty, nevertheless, like 
other departments of nature, doubtless it will ultimately be ex- 
plained by the researches of physiologists. I only need to call at- 
tention to consciousness as an important factor in evolution. 

We now approach the question of the origin of organic ma- 
chines with fresh resources. Did the consciousness of the animal 
find his structure made ready to hand, or did he, under the dire 
stimuli of necessity, produce through ages these modifications in 
his own structure ? We are told by some of our friends that law 
implies a lawgiver, that evolution implies an evolver : the next 
question is. Where is the lawgiver ? where is the evolver ? where 
are they located ? This question is best answered, as it appears 
to me, as follows. In the first place, I may say, it is distinctly 
proved in some directions, that the constant applications of force 
or motion in the form of strains, in the form of impacts and 
blows, upon any given part of the animal organism, do not fail to 
produce results in change of structure. I believe the changes in 
the ungulates, to which I have called your attention, are the re- 
sult of strains and impacts, precisely as I have shown you the 
manner of the fracture of the vertebral column of the primitive 


vertebrates of the Permian period. This would require long dis- 
cussion to render clear ; nevertheless, I venture to make the asser- 
tion that this series of structures is the result of definite and dis- 
tinct organic forces, directed to special ends. We have yet to get 
at the conflicting forces which have produced the results we see. 
Mechanical evolution will give us a good deal to do for some time 
to come. Of course, if motion has had any effect in modifying 
structure, it behooves us to investigate those conditions which 
give origin to motion in animals. First in order come the sensi- 
bilities of the animal, which we have traced to simple conscious- 
ness ; and stimuli, upon notice of which he immediately begins to 
move. The primary stimulus of all kinds of motion is necessarily 
touch. If a stone falls upon the tail of some animal which has 
a tail, he immediately gets out of that vicinity. If a jelly-fish 
with a stinging apparatus runs across an eel which has no scales, 
the eel promptly moves. External applications of unpleasant 
bodies will always cause an animal to change his location. Then 
he is constantly assaulted by the dire enemy of beasts, hunger, an 
instinct which is evidently universal, to judge from the actions of 
animals. This seems to have fashioned, in large part, all forms 
of life from the least to the greatest, from the most unorganized to 
the most complex. Each exercised itself for the purpose of fill- 
ing its stomach with protoplasm. Then come the stimuli which 
appeal to a sense allied to that of touch, changes of tempera- 
ture. No animals like to be too cold or too hot ; and when the 
temperature is disagreeable, the tendency is to go away from that 
locality. Among primary instincts must be included that of re- 
production. After that comes the sensation of resistance, or, 
carried to a high degree, of anger : when an animal's interests are 
interfered with, its movements restricted, the most energetic dis- 
plays are prompted. So, you see, it is a matter of necessity that 
mental phenomena lie at the back of evolution, provided always 
that the connecting link of the argument — that motion has ever 
affected structure — be true. That is a point which, of course, 
admits of much discussion. I have placed myself on the affirm- 
ative side of that question ; and, if I live long enough, I expect to 
see it absolutely demonstrated. 

Of course the development of mind becomes possible under 
such circumstances. It is not like a man lifting himself up by 
his boots, which it would be were there no such thing as memory. 
But with that memory which accumulates, which formulates, first 


habits and then structures, especially in the soft, delicate nervous 
tissue, the development of the function of the mind, as well as the 
machinery of the mind, becomes perfectly possible. We develop 
our intellect through the accumulation of exact facts ; through 
the collation of pure truth, no matter whether it be a humble 
kind of truth — as the knowledge of the changes of the seasons, 
which induces some animals to lay up the winter's store ; whether 
it be knowledge of the fact that the sting of the bee is very dis- 
agreeable ; or knowledge of the fact (of which the wild ox, no 
doubt, is thoroughly aware) that the teeth of the wolf are not 
pleasant to come in contact with ; or whether it be the complex 
knowledge of man. When the cerebral matter has become larger 
and more complex, it receives and retains a much greater number 
of impressions, and the animal becomes a more highly educated 

As regards the department of emotions or passions, they are 
also much stimulated by the environment. Animals which live in 
a state of constant strife, naturally have their antagonistic passions 
much developed ; while amiable, sympathetic sentiments are better 
and more largely produced by peace-loving animals. Thus it is 
that the various departments of the mind have the beautiful results 
which we now find in the human sjjecies. 

There are some departments of the mind which some of our 
friends decline to admit having had such an origin. The moral 
faculty, for instance, is excepted by many from this series. But 
the reasons why they object to its production in this way are, to 
my mind, not valid. The development of the moral faculty, which 
is essentially the sense of justice, appears to them not to fall with- 
in the scope of a theory of descent or of evolution. It consists of 
two parts. First is the sentiment of benevolence, or of symj^athy 
with mankind, which gives us the desire to treat them as they 
should be treated. It is not sufficient for justice that it is un- 
mixed mercy or benevolence, which is sometimes very injurious, 
and very often misplaced. It requires, in the second place, the 
criticism of the judgment, of the mature intellect, of the rational 
faculty, to enable the possessor to dispose of his sentiments in the 
proper manner. The combination of rational discrimination and 
judgment, with benevolence, constitutes the sense of justice, which 
has been derived, no doubt, as a summary of the development of 
those two departments of the mind — the emotions and the intel- 


It is said that a sense of justice could not be derived from 
no sense of justice ; that it could not have been derived from the 
state of things vs^hich we find in the animals, because no animal is 
known to exhibit real justice ; and that objection is valid as far 
as it goes. I suspect that no animal has been observed to show a 
true sense of justice. That they show sympathy and kindness, 
there is no question ; but when it comes to real justice, they do 
not display it. But do all men display justice ? Do all men 
understand justice ? I am very sure not. There are a good many 
men in civilized communities, and there are many tribes, who do 
not know what justice is. It does not exist as a part of every 
mental constitution. I never lived among the Bushmen, and do 
not know exactly what their mental constitution is ; but in a gen- 
eral way the justice of savages is restricted to the very smallest 
possible circle — that of their tribe or of their own family. There 
is a class of people who do not understand justice. I do not refer 
to people who know what right is, and do not do it ; but to the 
primitive state of moral character, in which, as in children, true 
justice is unknown. I call attention to the fact, because some 
of our friends have been very much afraid that the demonstration 
of the law of evolution, physical and metaphysical, would result 
in danger to society. I suspect not. The mode in which I under- 
stand this question appears to me to be beneficial to society, rather 
than injurious ; and I therefore take the liberty of appending this 
part of the subject to its more material aspect. 

I refer to another topic, that is to the nature of life, and the 
physical basis of life. The word '^ life " is so complex that it is 
necessary to define it, and so to define it away that really the word 
"life" does not retain its usual definition. Many phenomena of 
life are chemical, physical, mechanical. We have to remove all 
these from consideration, because they come within the ordinary 
laws of mechanical forces ; but we have a few things left which 
are of a different character. One is the law of growth, which is 
displayed in the processes of embryonic succession ; secondly, the 
wonderful phenomena of sensibility. Those two things we have 
not yet reduced to any identity with the ordinary laws of force, 
though we know of their dynamic equivalency. In the phenome- 
na of embryology the phenomena of evolution are repeated, only 
concentrated in the early stages through which animals have to 
pass. So whatever explains the general phenomena of evolution 
exjilains the phenomena of embryology. 


What is the nature of physical sensibility ? In this planet, it 
is found residing only in one form of matter, which has a slightly 
varied chemical constitution, namely, protoplasm, so called from 
a physical standpoint. Now, this world, as you all know, has 
passed through many changes of temperature. Its early periods, 
it is probable, were so very hot that protoplasm had a very poor 
chance. Again, can we assume for a moment that this little speck 
in the great universe is the only seat of life ? I suppose scarcely 
any scientific man will venture to do so. If, therefore, life exists 
in other planets, worlds, and systems, does it necessarily occupy 
bodies of protoplasm in those different, remote spheres ? It would 
be a great assumption. It is altogether improbable. The cer- 
tainty is, that in those planets which are in proximity to the sun's 
heat there could be no protoplasm. Protoplasm in the remote 
planets would be a hard mineral, and near the sun it would be dis- 
sipated into its component gases. So that, if life be found in other 
parts of this universe, it must reside in some different kind of 
material. It is extremely probable that the physical conditions 
that reside in protoplasm might be found in other kinds of matter. 
It is in its chemical inertness, and in its physical constitution, that 
its adaptation to life resides ; and the physical constitution neces- 
sary for the sustentation of life may be well supposed to exist in 
matter in other parts of the universe. I only say the door is open 
and not closed : any one who asserts that life can not exist in any 
other material basis than protoplasm is assuming more than the 
world of science will permit him to assume. And that it is con- 
fined to this single planet, among the great systems of the universe 
— that assumption will not for a moment be allowed. Therefore 
the subject is one which allows us a free field for future investiga- 
tion : it is by no means closed in the most important laws which 
it presents to the rational thinker. I hope, also, if the evi- 
dence in favor of this hypothesis of the creation of living forms 
be regarded as true, that no one will find in it any ground for any 
very serious modification of existing ideas on the great questions of 
right and wrong, which have been long since known by men as a 
result of experience, and without any other scientific demonstra- 
tion whatsoever. 




In attemiDting to ascertain the course of evolution of the 
Vertebrata, and to construct phylogenetic diagrams which shall 
express this history, among the difficulties arising from deficient 
information one is especially prominent. As is well known, 
there are many types in all the orders of the Vertebrata which 
present us with rudimentary organs, as rudimental digits, feet or 
limbs, rudimental fins, teeth, and wings. There is scarcely an 
organ or part which is not somewhere in a rudimental and more 
or less useless condition. The difficulty which these cases present 
is, simply, whether they be persistent primitive conditions, to be 
regarded as ancestral types which have survived to the present 
time, or whether, on the other hand, they be results of a process 
of degeneration, and therefore of comparatively modern origin. 
The question, in brief, is, whether these creatures presenting 
these features be primitive ancestors or degenerate descendants. 

In the first place, let us define the meaning of the word degen- 
erate. This must be done first from a structural or anatomical 
standpoint. Degeneracy may be defined as a loss of parts with- 
out corresponding development of other parts. All animals are 
degenerate in some respect or another, as, for instance, the Mam- 
malia in the small size of the pineal gland and of the coracoid 
bone ; so that degeneracy, as a whole, can only be affirmed where 
the sum of the subtractions is greater than the sum of the addi- 
tions. Function of the parts must, however, be consulted in this 
matter. We naturally regard sensibility as the highest of animal 
functions, and mind as the highest form of sensibility. There- 
fore development of organs of sensibility and sense and mind, con- 
stitutes a better claim of progress than development of stomach 
or of skin. Since motion is under the direction of sensibility, 


organs of movement have much to do with the question. When 
perfection in this respect conflicts with perfection of brain, in 
evidence of position, we naturally give the preference to the 
latter in deciding. Thus the ruminating mammals are much 
superior to man in the structure of their feet, teeth, and stomach, 
yet we properly assign tlie higher position to the Quadrumana and 
to man, on account of the superior complication of their brain- 

Paleontology has proved,* what had been already surmised, 
that the development of animal organisms has been on lines of 
increasing specialization of parts. That is, in lines of increas- 
ingly perfect adaptations of structures to ends, or functions. In 
certain series of animals we witness steadily increasing perfection 
of mechanisms of the limbs for running ; in others for digging ; 
in others for flying. In the teeth we find increasing perfection of 
machines for grinding, for cutting, or for seizing. In the brain 
the specialization has evidently been toward increased acuteness 
of perception, increased energy of action, and increased intelli- 
gence. Specialization does not, however, necessarily imply pro- 
gressive development. Adaptation may be to a parasitic or a ses- 
sile mode of life. Such adaptation is often disjilayed in a very 
special modification of parts, as in the anterior limbs of some of 
the parasitic Crustacea ; in the mouth parts of some Arachnida ; 
in the feet of the sloth, and in the jaws of the ant-eaters. 

Embryology has furnished, and will furnish, many important 
hints and demonstrations as to the true meaning of the rudiment- 
ary condition or absence of parts, and thus indicate the phylo- 
genetic connections of animals. Thus the origin of the Tunicata 
from primitive vertebrate-like forms would probably never have 
been suspected but for embryological studies ; and the origin of 
the very peculiar order of Rotifera has been explained in like 
manner. But embryology has its limitations, for the transitional 
characters presented by embryos are only partially of the nature 
of a record of the structures which belonged to their ancestors in 
successive geological ages, and are frequently special adaptations 
to the necessities of their embryonic life. Such are the stato- 
blasts which are present in fresh- water sponges and Folyzoa, and 
wanting in the marine forms ; and the allautois and placenta of 

* Cfr. "On the Evidence for Evolution in the History of the Extinct Mam- 
malia," "rioc. Amcr. Assoc. Adv. Sciences" for 1883. 


Vertebrata. In a number of groups tbe embryo seems to have 
been more susceptible to the influence of the environment than 
the adults.* It results that in many cases the phylogeny can 
only be determined by the discovery and investigation of the 
ancestors themselves, as they are preserved in the crust of the 
earth. In all cases this discovery confirms and establishes such 
definite conclusions as may be derived from embryology. It is 
also clear that on the discovery of phylogenetic series it becomes 
at once possible to determine the nature of defective types. It 
becomes possible to ascertain whether their rudimental parts 
represent the beginnings of organs, or whether they are the 
result of a process of degeneration of organs once well developed. 

A great deal of light has been happily thrown on this question, 
as regards the Vertebrata, by the recent work done in North 
American paleontology. The lines of descent of many of the 
minor groups liave been positively determined, and the phyloge- 
netic connections of most of the primary divisions or classes have 
been made out. The result of these investigations has been to 

* A remarkable instance of this state of things appears in the history of the 
evolution of the insects. It is quite impossible to understand this history without 
believing that the larval and pupal states of the highest insects are the results of a 
process of degeneracy which has affected the middle periods of growth but not the 
mature results. The earliest insects are the Orthoptera, which have active aggres- 
sive larvae and pupae, undergoing the least changes in their metamorphosis (Ameta- 
bola), and never getting beyond the primitive mandibulate condition at the end. 
The metamorphosis of the jawed Neuroptera is little more marked, and they are 
one of the oldest orders. 

The highest orders with jaws undergo a marked metamorphosis (Coleoptera, 
Hymenoptera), the Hymenoptcra even requiring artificial intervention in some in- 
stances to make it successful. Finally, the most specialized orders, the suctorial 
Diptera and Lepidoptera, especially the latter, present us with very unprotected 
more or less parasitic stages, both active and inactive. These animals have 
evidently degenerated, but not so as to prevent their completing a metamorphosis 
necessary for purposes of reproduction. As is well known, many imagines (Satur- 
niidae, Qlstridce) can perform no other function, and soon die, while in some Diptera 
the incomplete larvae themselves reproduce, so that the metamorphosis is never 

This history is parallel to that proposed by Dohrn to account for the origin of 
the Ammocoetes larval stage of the Marsipobranchii. He supposes this form to be 
more degenerate than its probable ancestral type in the ancestral line of the Verte- 
brata, as it is inferior to its own adult. An inactive life in mud is supposed by 
Dohrn to have been the effective cause. An inactive life on the leaves of plants, 
or in dead carcases, has probably been the cause of the same phenomenon in the 
Lepidoptera and Diptera. 


prove that the eyolution of the Vertebrata has proceeded not only 
on lines of acceleration, but, to a much greater extent than has 
been heretofore suspected, on lines of retardation.* That is, that 
evolution has been not only progressive, but at times retrogressive. 
This is entirely in accord with the views derived by Dohrn from 
embryology,! who, however, wrote only of the origin of the 
Vertebrata as a whole and not of its divisions, excepting only 
the Leptocardii and Marsipobranchii, that is, of the sand-lance 
and the lampreys and hags. The demonstration of such relations 
for the higher Vertebrata is now done nearly for the first time. J 

Omitting from consideration the two classes above mentioned, 
whose remains have not yet been certainly found in a fossil state, 
there remain the following : the Pisces, Batrachia, Reptilia, Aves, 
and Mammalia. 

The Mammalia have been traced to the theromorphous reptiles 
through the Monotremata. The birds, some of them at least, ap- 
pear to have been derived from the Dinosaurian reptiles. The rep- 
tiles, in their primary representative order, the Theromorpha, have 
been probably derived from the rhachitomous Batrachia.* The 
Batrachia have originated from the subclass of fishes, the Dipnoi, 
though not from any known form. I have shown that the true 
fishes or Teleostomi have descended from an order of sharks,! 
the Ichthyotomi, wliich ]oossess characters of the Dipnoi also. 
The origin of the sharks remains entirely obscure, as does also 
that of the Pisces as a whole. Dohrn believes the Marsiijo- 

* See "Origin of Genera,'' E. D. Cope, Plailadelphia, 1868, where these terms 
are introduced. 

f Sec "Der Ui-sprung der Wirbelthiere u. d. Princip des Functionwechsels," 
Leipsic, 1873. 

X " On the Phylogeny of the Vertebrata," Cope, " Amer. Naturalist," Dec., 1884. 
I here remark that my researches have now, as I believe, disclosed the ancestry of 
the mammals, the birds, the reptiles, and the true fishes, or Teleostomi, including 
the special phylogenies of the Batrachia and Keptilia, and some of the Mammalia. 
See the following references: "American Naturalist," 1884, p. 1136; "Proceedings 
Academy Philadelphia," 186Y, p. 234 ; " Proceedings American Philosoph. Society," 
1884, p. 585; "American Naturalist," 18S4, p. 27; "Proceedings American Asso- 
ciation for the Advancement of Science," xix, 1871, p. 233; "Proceedings Amer- 
ican Philosophical Society," 1882, p. 447; "American Naturalist," 1884, pp. 261 
and 1121 ; "Report U. S. Gcol. Survey W. of lOOth Mer.," G. M. Wheeler, 1877, 
iv, ii, p. 282. 

* Through the batrachian order Embolomeri. (Ed. 1 886.) 
[ "Proceedings Am. Phil. Soc," 1884, p. 585. 


branchii to have acquired its present characters by a process of 
degeneration. The origin of the Vertebrata is as yet entirely un- 
known, Kowalevsky deriving them from the Ascidians, and 
Semper from the Annelida. The above results I have embodied 
in the following phylogenetic diagram : 

Aves Mammalia 
\ / 

\ / 



C Teleostomi* Batrachia 

I I \ 

Pisces -l Selachii Ichthyotomi Dipnoi 



Accepting this j)hylogeny, it becomes possible to determine 
the course of development, first, of the whole series ; and, secondly, 
of the contents of each class taken by itself. I will first consider 
the direction of the evolution of the Vertebrata as a whole. 


The Vertebrata exhibit the most unmistakable gradation in 
the characters of the circulatory system, f It has long been the 
custom to define the classes by means of these characters, taken 
in connection with those of the skeleton. Commencing in the 
Leptocardii with the simple tube, we have two chambers in the 
Marsipobranchii and fishes ; three in the Batrachia and Reptilia ; 
and four in the Aves and Mammalia. The aorta-roots commence 
as numerous pairs of branchial arteries in the Leptocardii ; we 
see seven in the Marsipobranchi, five in the fishes (with number 
reduced in some) ; four and three in Batrachia, where they gener- 
ally cease to perform branchial functions ; two and one on each 
side in Reptilia ; the right-hand one in birds, and the left-hand 
one in Mammalia. This order is clearly an ascending one through- 
out. It consists of, first, a transition from adaptation to an aquatic, 
to an aerial respiration ; and, second, an increase in the power to 
aerate and distribute a circulating fluid of increased quantity, 

* In the original I used the name Hyopomata for tiiis division, but Owen's name 
Teleostomi is prior. (Ed. 1880.) 

\ See " Origin of Genera," 1868, p. 20, for a table of the characters of the circu- 
latory system. 


and of increased calorific capacity. In other words, the circula- 
tion passes from the cold to the hot blooded tyjDc coincidentally 
with the changes of structure above enumerated. The accession 
of a capacity to maintain a fixed temperature while that of the 
surrounding medium changes, is an important advance in animal 

The brain and nervous system also display a general progress- 
ive ascent. Leaving the brainless Leptocardii, the Marsipo- 
branchs and fishes present us with small hemispheres, larger 
optic lobes, and well-developed cerebellum. The hemispheres 
are really larger than they appear to be, as Rabl Eiickard has 
shown * that the supposed hemispheres are only corpora striata. 
But the superior walls are membranous, and support on their in- 
ternal side only a layer of epithelial cells, as in the embryos of 
other Vertebrata, instead of the gray substance. So that, al- 
though we find that the cerebellum is really smaller in the 
Batrachia and most Eeptilia than in the fishes, the better de- 
velopment of the hemispheres in the former gives them the pre- 
eminence. The Elasmobranchii show themselves superior to 
many of the fishes in the large size of their corpora restiformia 
and cerebellum. The Eeptilia constitute an advance on the Ba- 
trachia. In the latter the optic thalami are, with some excep- 
tions, of greater diameter than the hemispheres, while the reverse 
is generally true of the reptiles. The crocodiles display much 
superiority over the other reptiles in the larger cerebellum, with 
rudimental lateral lobes. The great development of the hemi- 
spheres in birds is well known, while the general superiority of 
the brain of the living Mammalia over all other vertebrates is 

The consideration of the successive relations of the skeleton in 
the classes of vertebrates embraces, of course, only the characters 
which distinguish those classes. These are not numerous. They 
embrace the structure of the axis of the skull ; of the ear-bones ; 
of the suspensors of the lower jaw ; of the scapular arch and 
anterior limb, and of the pelvic arch and posterior limb. Other 
characters are numerous, but do not enter into consideration at 
this time. 

The persistence of the primitive cartilage in any part of the 
skeleton is, embryologically speaking, a mark of inferiority. 

* " Biologischcs Centralblatt," 1884, p. 449. 


From a physiological or functional standpoint it has the same 
significance, since it is far less effective both for support and for 
movement than is the segmented osseous skeleton. That this is 
a prevalent condition of the lower Vertebrata is well known. 
The bony fishes and Batrachia have but little of the primitive 
cartilage remaining, and the quantity is still more reduced in the 
higher classes. Systematically, then, the vertebrate series is in 
this respect an ascending one. The Leptocardii are membra- 
nous ; the Marsipobranchii and most of the Elasmobranchii 
cartilaginous ; the other Pisces and the Batrachia have tlie 
basicranial axis cartilaginous, so that it is not until the Eeptilia 
are reached that we have osseous sphenoid and presjjhenoid bones, 
such as characterize the birds and mammals. The vertebral 
column follows more or less inexactly the history of the base of 
the skull, but its characters do not define the classes. 

As regards the suspensor of the lower jaw, the scale is in the 
main ascending. We witness a gradual change in the segmenta- 
tion of the mandibular visceral arch of the skull, which clearly 
has for its object such a concentration of the parts as will produce 
the greatest effectiveness of the biting function. This is accom- 
plished by reducing the number of the segments, so as to bring 
the resistance of the teeth nearer and nearer to the power, that is, 
the masseter and related muscles, and their base of attachment, 
the brain-case. This is seen in bony Vertebrates in the reduction 
of the segments between the lower jaw proper and the skull, from 
four to none. In the fishes we have the hyomandibular, the sym- 
plectic, the inferior quadrate, and the articular. In the Ba- 
trachia, reptiles and birds, we have the quadrate and articular 
only, while in the Mammalia these elements also are wanting. 

The examination of the pectoral and pelvic arches reveals a 
successive modification of the adaptation of the parts to the me- 
chanical needs of the limbs. In this regard the air-breathing 
types display wide diversity from the gill-bearing types or fishes. 
In the latter, the lateral elements unite below without the inter- 
vention of a median element or sternum, while in the former the 
sternum, or parts of it, is generally present. Either arrange- 
ment is susceptible of much mechanical strength, as witness the 
Siluroid fishes on the one hand, and the mole on the other. The 
numerous segments of the fishes' pectoral arch must, however, be 
an element of weakness, so that from a mechanical standpoint it 
must take the lowest place. The presence of sternal elements, 


with both clavicle, procoracoid, and coracoid bones on each side, 
gives the Eeptilia the highest place for mechanical strength. The 
loss of the coracoid seen in the tailed Batrachia, and loss of cora- 
coid and procoracoid in the Mammalia, constitute an element of 
weakness. The line is not then one of uniform ascent in this re- 

The absence of pelvis, or its extremely rudimental condition in 
fishes, places them at the foot of the line in this respect. The 
forward extension of the ilium in some Bati-achia and in the Mam- 
malia, is to be compared with its backward direction in Eeptilia, 
and its extension both ways in the birds. These conditions are 
all derived by descent from a strictly intermediate position in the 
Batrachia and Eeptilia of the Permian epoch. The anterior di- 
rection must be regarded as having the mechanical advantage 
over the posterior direction, since it shortens the vertebral column 
and brings the posterior nearer to the anterior feet. The prev- 
alence of the latter condition in the Mammalia enables them to 
stand clear of the ground, while the Eeptilia move with the abdo- 
men resting upon it. As regards the inferior arches of the pelvis, 
the Mammalia have the advantage again, in the strong bony me- 
dian symphysis connecting the ischium and pubis.* This char- 
acter, universal among the land Vertebrata of the Permian epoch, 
has been lost by the modern Eeptilia, and birds, and is retained 
only by the Mammalia. So the lines, excepting the mammalian, 
have degenerated in every direction in the characters of the pelvis. 

The limbs of the Pisces are as well adapted to their environ- 
ment as are those of the land Vertebrata ; but, from an embryolog- 
ical standpoint, their structure is inferior. The primitive rays 
are less modified in the fin than in the limb ; and limbs them- 
selves display a constantly increasing differentiation of parts, com- 
mencing with the Batrachia and ending with the Mammalia. 
The details of these modifications belong to the history of the 
contents of the classes, however, rather than to the succession of 
the Vertebrata as a whole. 

In review, it may be said that a comparison of the characters 
which define the classes of the Vertebrates shows that this branch 
of the animal kingdom has made with the ages successive steps 
of progress from lower to higher conditions. This progress has 
not been without exception, since, as regards the construction of 

* This is an advantage as a protection during gestation. 


the scapular arch, the Mammalia have retrograded from the rep- 
tilian standard as a whole. 

In subsequent pages I shall take up the lines of the classes 


Embryological evidence leads us to anticipate that the primi- 
tive Vertebrata possessed nothing representative of the vertebrate 
skeleton beyond a chorda dorsalis. Above this axis should lie the 
nervous chord, and below it the nutritive and reproductive sys- 
tems and their appendages. Such a type we have in its simplest 
form in the Branchiostoma, the representative of the division of 
the Acrania. In tlie animals of this division the mouth and anus 
have the usual vertebrate position, at opposite ends of the body- 
cavity. The Tunicata (formerly referred to the Mollusca) are now 
known to present a still more primitive type of Vertebrata, to 
which the name of Urochorda has been given. These curious, 
frequently sessile creatures, have a vertebrate structure during the 
larval stage, which they ultimately lose. They have the necessary 
chorda, and nervous axis with a brain, and a cerebral eye. They 
have at this time a tail, and are free-swimming ; a peculiarity 
which a few of them retain throughout life (Appendicularia).* 
They differ from the Acrania in the positions of the extremities 
of the alimentary canal. The mouth is on the top of the anterior 
end of the animal, and is supposed by some anatomists to repre- 
sent an open extremity of the pineal gland of other Vertebrata ; 
while the tract represented by this body, the third ventricle of the 
brain, and the pituitary body of the Craniata, are the remains of 
the primitive oesophagus of the Urochorda. The anus in the 
adult tunicates is either dorsal, or it opens into the body-cavity, as 
in the young larvae. In Appendicularia it is ventral (Gegenbaur). 

The history of the Tunicata can not be traced by paleontolo- 
gists as yet, owing to the absence of hard parts in their structure. 
The evidence of embryology has, however, convinced phylogenists 
that the ancestors of this class resembled their larvae, and that they 
have as a whole undergone a remarkable degeneracy. They have 
passed from an active, free life to a sessile one, and have lost the 
characters which pertain to the life of vertebrates generally. 

It was to have been anticipated, however, that all of these an- 

* See Lankester on "Degeneration," " Nature Series," 1880. 



cestral Tunicata did not undergo this degenerative metamorphosis, 
for it is to such types that we must look for the ancestors of the 
other Vertebrata, the Acrania and the Craniata. And here pale- 
ontology steps in and throws new light on the question. I have 
pointed out briefly, in the " American Naturalist," * that a second 
order must be added to the Urochorda, viz., the Antiarcha, in 
which the anus presents the same position as in the Acrania, at 
the posterior end of the body, while an orifice of the upper surface 
represents the mouth of the Tunicata. To this order is to be re- 
ferred the family of the Pterichthyidge, of which the typical genus, 

FiQ. 63. 

Fig. 62. Bothriolepis canadensis Whiteaves, from above, half size of a small speci- 
men. The valve of the dorsal mouth, or notostome, is broken. Fig. 63. Chelyosoma 
maclovianum Bred. & Sow., «/3 natural size, from Point Barrow, Alaska. 

Pterichthys, is a well-known form of the Devonian period. This 
genus retained its tail, which was the cause, in connection with 
the presence of lateral fin-like appendages, of its having been sup- 
posed to be a fish, by Agassiz, Hugh Miller, and others. It is pos- 
sible that the American Bothriolepis canadensis lost its tail, as in 
the majority of Urochorda. The tunicate which approaches near- 
est to the Antiarcha is the Arctic Chelyosoma. 

From the Antiarcha to the Acrania and Craniata, then, the 
line is an ascending one. 

* March, 1885, p, 289. 



The fishes form various series and subseries, and the tracing 
of all of them is not yet practicable, owing to the deficiency in 
our knowledge of the earliest or ancestral forms. Thus the ori- 
gins of the four subclasses, Holocephali, Dipnoi, Elasmobranchii, 
and Teleostomi, are lost in the obscurity of the early Palaeozoic 

A comparison of the four subclasses just named shows that 
they are related in pairs. The Holocephali and Dipnoi have no 
distinct suspensory segment for the lower jaw, while the. Elasmo- 
branchii and Hyopomata have such a separate element. The lat- 
ter, therefore, present one step in the direction of complication be- 
yond the former ; but whether the one type is descended from the 
other, or whether both came from a common ancestor or not, is 
unknown. If one type be derived from the other, it is not certain 
which is ancestor, and whether the process has been one of advance 
or retrogression. The fauna of the Permian eijoch throws some 
light on the relations of these subclasses in other respects. The 
order of the Ichthyotomi,* while belonging technically to the 
Elasmobranchi, presents characters of both the Dipnoi and the 
Teleostomi. It is so near to the Dipnoi in the characters of the 
skull that nothing save the presence of a free suspensor of the 
lower jaw prevents its entering that subclass. It indicates that 
the one of these divisions is descended from the other, or both 
from a common division which may well be the group Ichthyotomi 
itself. In case the Elasmobranchi have descended from the Ich- 
thyotomi, they have undergone degeneracy, as the Ichthyotomi 
have a higher degree of ossification and differentiation of the bones 
of the skull. If they descended from a purely cartilaginous type 
of Dipnoi, they have advanced, in the addition of the free hyo- 
mandibular. If the Dipnoi have descended from either division, 
they have retrograded, in the loss of the free hyomandibular. As 
regards the Teleostomi, we have a clear advance over the other 
subclasses in the presence of the maxillary arch and the opercular 

Too little is known of the history of the subclasses, excepting 
the Teleostomi, for us to be able to say much of the direction of 

* See " Palaeontological Bulletin," No. 38, E. D. Cope, 1884, p. 5*72, on the genus 


the descent of their contained orders. On the sharks some lijrht 
is shed by the discovery of tlie genus Chlamydoselachus Garruan,* 
which is apparently nearly related to the Cladodonts of the Devo- 
nian seas. This genus has more numerous branchial slits than all 
but two of the genera of existing sharks, and it differs from all but 
these two in having a more perfect articulation between the tooth- 
bearing bones and the cranium. Of the Teleostomi a much clearer 
history is accessible. It has three primary divisions or tribes which 
differ solely in the structure of the supports of the fins. In the 
first division, the Crossopterygia, the anterior limbs have numerous 
basilar bones which are supported on a peduncle of axial bones. 
The posterior limbs are similar. In the second division, or Chron- 
drostei (the sturgeons, etc.), the posterior limb remains the same, 
while the anterior limbs have undergone a great abbreviation in 
the loss of the axial bones and the reduction of the number and 
length of the basilar bones. In the third group, or Actiuopteri,f 
both limbs have undergone reduction, the basilar bones in the pos- 
terior fin being almost all atrophied, while those of the fore limb 
are much reduced in number. 

The phylogeny of these tribes is not easy to make out at pres- 
ent. The descent has been, no doubt, in the order named in time, 
but the starting-point is yet uncertain. Thus the Chondrostei 
appear later in time than either of the other tribes, a history 
which probably only represents our ignorance. The characters of 
the genus Crossopholis Cope, from the American Eocene, strongly 
sufTfjest that the existing forms have descended from scaled an- 
cestors. The Crossopterygian fore limb, with its arm-like axis, 
tells of the origin of the first limbed vertebrates, the Batrachia, 
whose skull-structure, however, only permits their derivation 
from the Dipnoi or Ilolocephali. As the former subclass has the 
Crossopterygian fin-structure, we can safely regard them as the 
ancestors of the Batrachia, while the Crossopterygia are a side- 
line from a similar type, probably the Ichthyotomi, because these 
have a free suspensor of the lower jaw. But of the structure of 
the fins of the Ichthyotomi unfortunately we know nothing. If 
this position be true, then the successive derivation of the Chon- 
drostei and the Teleostomi in one line is rendered probable. The 
modification of structure has consisted in the contraction of the 

* "Proceedings American Assoc. Adv. Sci.," 1884. 

f Partly agrees with the Teleostei of Miillcr, but includes many of his Ganoidea. 


supporting elements of the pectoral and ventral fins by the reduc- 
tion of their numbers and length. According to paleontological 
history, however, the tribe of Teleostomi with most contracted 
fins, Actinopteri, appeared in the Coal Measures (Paleoniscidae), 
or very soon after the Orossopterygia in the Devonian. 

The descent of the fishes in general has witnessed, then, a 
contraction of the limbs to a very small compass, and their sub- 
stitution by a system of accessory radii. This has been an ever- 
widening divergence from the type of the higher Vertebrata, and 
from this standpoint, and also a view of the "loss of parts with- 
out complementary addition of other parts," may be regarded as 
a process of degradation. 

Taking up the great division of the Actinopteri, which em- 
braces most of the species of living fishes, we can trace the direc- 
tion of descent largely by reference to their systematic relations 
"when we have no fossils to guide us. 

The three subtribes adopted by Jordan represent three series 
of the true fishes which indicate lines of descent. The Holostei 
include the remainder of the old ganoids after the subtraction of 
the Orossopterygia and the Chondrostei. They resemble these 
forms in the muscular bulbus arteriosus of the heart and in tlie 
chiasm of the optic nerves. Both of these characters are com- 
plexities which the two other divisions do not possess, and which, 
as descendants coming later in time, must be regarded as inferior, 
and therefore to that extent degenerate. Of these divisions the 
Physostomi approach nearest the Holostei, and are indeed not 
distinctly definable without exceptions. The third division, or 
Physoclysti, shows a marked advance beyond the others in : (1) 
the obliteration of the primitive trachea, or ductus pneumaticus, 
which connects the swim-bladder and oesophagus ; (2) the advance 
of the ventral fins from the abdomen forward to the throat ; (3) 
the separation of the parietal bones by the sujiraoccipital ; (4) 
the presence of numerous spinous rays in the fins ; and (5) the 
roughening of the edges of the scales, forming the ctenoid type. 
There are more or less numerous exceptions to all of these char- 
acters. The changes are all further divergencies from the other 
vertebrate classes, or away from the general line of ascent of the 
vertebrate series taken as a whole. The end gained is specializa- 
tion ; but whether the series can be called either distinctively pro- 
gressive or retrogressive, is not so clear. The development of 
osseous spines, rough scales, and other weapons of defense, together 


with the generally superior energy and tone which prevail among 
the Physoclysti, ciiaracterize them as superior to the Physostomi, 
but their departure from the ascending line of the Vertebrata has 
another appearance. 

The descent of the Physoclystous fishes has probably been 
from Holostean ancestors, both with and without the intervention 
of Physostomous forms. This is indicated by increase in the 
number of basilar bones in the fins of families which have pec- 
toral ventral fins, as in the extinct genus Dorypterus.* 

The Physostomi display three or four distinct lines of descent. 
The simplest type is represented by the order Isospondyli, and 
paleontology indicates clearly that this order is also the oldest, 
as it dates from the Trias at least. In one line the anterior dor- 
sal vertebrae have become complicated, and form an interlocking 
mass which is intimately connected with the sense of hearing. 
This series commences with the Characinid^e, passes through the 
Cyprinidce, and ends with the Siluridae. The arrangements for 
audition constitute a superadded complication, and to these are 
added in the Siluroids defensive spines and armor. Some of 
this order, however, are distinctly degenerate, as the soft pur- 
blind Ageniosus, and the parasitic Stegophilus and Vandellia, 
which are nearly blind, without weapons, and with greatly re- 
duced fins. 

The next line (the Haplomi, pike, etc.) loses the precoracoid 
arch and has the parietal bones separated, both characters of the 
Physoclysti. This group was apparently abundant during the 
Cretaceous period, and it may have given origin to many of the 

Another line also loses the precoracoid, but in other respects 
diverges totally from the Physoclysti and all other Physostomi. 
This is the line of the eels. They next lose the connection be- 
tween the scapular arch and the skull, which is followed by the 
loss of the pectoral fin. The ventral fin disappeared sooner. The 
palatine bones and teeth disappear, and the suspensor of the lower 
Jaw grows longer and loses its symplectic element. The opercu- 
lar bones grow smaller, and some of them disappear. Tlie ossi- 
fication of most of the hyoid elements disappears, and some of 
their cartilaginous bases even vanish. These forms are the marine 
eels or Colocephali, The most extraordinary example of speciali- 

* See " Proceeds. Amcr. A830C. Adv. Science," 1 878, p. 297. 


zation and degeneracy is seen in the abyssal eels of the family 
Eurypharyngidas. Here all the degenerate features above men- 
tioned are present in excess, and others are added, as tlie loss of 
ossification of a part of the skull, almost total obliteration of the 
hyoid and scapular arches, and the semi-notochordal condition of 
the vertebral column, etc. 

The Physoclysti nearest the Physostomi have abdominal ven- 
tral fins, and belong to several orders. It is such types as these 
that may be supposed to have been derived directly from Holos- 
tean ancestors. They appear in the Cretaceous period (Derceti- 
dae), along with the types that connect with the Physostomi 
(Haplomi). Intermediate forms between these and typical Phy- 
soclysti occur in the Eocene (Trichophanes, Erismatopterus), 
showing several lines of descent. The Dercetidas belong appar- 
ently to the order Hemibranchi, while the Eocene genera named 
belong apparently to the Aphododiridae, the immediate ancestor 
of the highest Physoclysti, the Percomorphi. The order Hemi- 
branchi is a series of much interest. Its members lose the mem- 
brane of their dorsal spinous fin (Gasterosteidae), and then the fin 
itself (Fistularia, Pegasus). The branchial apparatus has under- 
gone, as in the eels, successive deossification (by retardation), and 
this in direct relation to the degree with which the body comes 
to be protected by bony shields, reaching the greatest defect in 
the Amphisilidae. One more downward step is seen in the next 
succeeding order of the Lophobranchii. The branchial hyoid 
apparatus is reduced to a few cartilaginous pieces, and the bran- 
chial fringes are much reduced in size. In the Hippocampidae 
the caudal fin disappears and the tail becomes a prehensile organ 
by the aid of which the species lead a sedentary life. Tlie mouth 
is much contracted and becomes the anterior orifice of a suctorial 
tube. This is a second line of unmistakable degeneracy among 
true fishes. 

The Physoclysti with pectoral ventral fins present us with per- 
haps ten important ordinal or subordinal divisions. Until the 
paleontology of this series is better known, we shall have diffi- 
culty in constructing phylogenies. Some of the lines may, how- 
ever, be made out. The accompanying diagram will assist in un- 
derstanding them. 

The Anacanthini present a general weakening of the organiza- 
tion in the less firmness of the osseous tissue and the frequent 
reduction in the size and character of the fins. The caudal vor- 


tebrae are of the protocercal type. As this group does not appear 
early in geological time, and as it is largely represented now in 
the abyssal ocean fauna, there is every reason to regard it as a 
degenerate type.* The 
scyphobranch line presents 
a specialization of the su- 
perior pharyngeal bones, 
which is continued by the 
Haplodoci (Batrachids). 
This can not be called a 
degenerate line, although 
the fin-rays are soft. The 
Heterosomata (flounders) 
found it convenient to lie 
on one side, a habit which 
would appear to result 
from a want of motive en- 
erg}'. The fins are very 
inefficient organs of move- 
ment in them, and they 
are certainly no rivals for 
swift-swimming fishes in 
the struggle for existence, 
excepting as they conceal 
themselves. In order to 
see the better while un- 
seen, the inferior eve has ■§ a o ^ g § 
turned inward, i. e., up- | § J /fl J K 
ward, and finally has pen- *^ rh cu / i>-^ 
etrated to the superior 
surface, so that both eyes 
are on one side. This pe- 
culiarity would be incred- 
ible if we did not know 
of its existence, and is an 
illustration of the extraordinary powers of accommodation pos- 


* The general characters of the deep-sea fish-fauna are those of degeneracy. 
(Ed. 1886.) 

f This order was proposed by Gill for the Eurypharyngidae, and is now added. 
(Ed. 1886.) 


sessed by nature. The Heterosomata can only be considered a 
degenerate group. 

The double bony floor of the skull of the Distegous percomorph 
fishes is a complication which places them at the summit of the 
line of true fishes. At the summit of this division must be placed 
the Pharyngognathi, which fill an imjoortant role in the economy 
of the tropical seas, and the fresh waters of the Southern hemi- 
sphere. By means of their powerful grinding pharyngeal ajipara- 
tus they can reduce vegetable and animal food inaccessible to other 
fishes. The result is seen in their multifarious species and innu- 
merable individuals decked in gorgeous colors, and often reaching 
considerable size. This is the royal order of fishes, and there is no 
reason why they should not continue to increase in importance in 
the present fauna. 

Very different is the line of the Plectognathi. The probable 
ancestors of this division, the Epilasmia (Chaetodontidne, etc.), are 
also abundant in the tropical seas, and are among the most brill- 
iantly colored of fishes. One of their peculiarities is seen in a 
shortening of the brain-case and prolongation of the jaws down- 
ward and forward. The utility of this arrangement is probably to 
enable them to procure their food from the holes and cavities of 
the coral reefs among which they dwell. In some of the genera 
the muzzle has become tubular (Chelmo), and is actually used as 
a blow-gun by which insects are secured by shooting them with 
drops of water. This shortening of tlie basicranial axis has pro- 
duced a corresponding abbreviation of the hyoid apparatus. The 
superior pharyngeal bones are so crowded as to have become a 
series of vertical plates like the leaves of a book. These charac- 
ters are further developed in the Plectognathi. The brain-case is 
very small, the face is very elongate, and the mouth is much con- 
tracted. The bones surrounding it in each jaw are co-ossified. 
The axial elements (femora) of the posterior fins unite together, 
become very elongate, and lose the natatory portion. In one group 
(Orthagoriscidge) the jjosterior part of the vertebral column is lost 
and the caudal fin is a nearly useless rudiment. In the Ostracion- 
tidae (which may have had a different origin, as tlie pharyngeal 
bones are not contracted) the natatory powers are much reduced, 
and the body is inclosed in an osseous carapace so as to be capable 
of very little movement. The entire order is deficient in osseous 
tissue, the bones being thin and weak. It is a marked case of 


There are several evident instances of sporadic degeneracy in 
otlier orders. One of these is the case of the familv of the Icos- 
teidte, fishes from deep waters off the coast of California. Al- 
though members of the Percomori^hi, the skeleton in the two gen- 
era Icosteus and Icichthys is unossified, and is perfectly flexible. 
Approximations to this state of things are seen in the parasitic 
genus Cyclopterus, and in the ribbon-fishes, Trachypteridse. 

Thus nearly all the main lines of the Physoclysti are degener- 
ate ; the exceptions are those that terminate in the Scombridae 
(mackerel), Serranidae, and Scaridas (Pharyngognathi). 


"We know Batrachia first in the Coal Measures. They reach a 
great development in the Permian epoch, and are represented by 
large species in the Triassic period. From that time they dimin- 
ish in numbers, and at the present day form an insignificant part 
of the vertebrate fauna of the earth. The history of tlieir suc- 
cession is told by a table of classification such as I give below : 

I. Siipraoceipital, intercalary and supratemporal bones present. Propodial 

bones distinct. 

Vertebral centra, including atlas, segmented, one set of segments together support- 
ing one arch Rhachifomi. 

Vertebrae segmented, the superior and inferior segments each complete, forming two 
centra to each arch Embolomeri. 

Vertebral centra, including atlas, not segmented, one to each arch Stegocephali. 

II. Supraoccipital and supratempoi*al bones wanting. Frontal and propodial 

bones distinct. 

a. An OS intercalare. 

A palatine arch and separate caudal vertebrae Proteida. 

aa. No OS intercalare. 
A maxillary arch ; palatine arch imperfect ; nasals, premaxillaries and caudal verte- 
brae distinct l/rodela* 

No maxillary or palatine arches ; nasals and premaxillary, also caudal vertebrae, dis- 
tinct Trachysiomata. 

III. Supraoccipital, intercalare and supratemporal bones wanting. Frontals 
and parietals connate ; propodial bones and caudal vertebrae confluent. 

Premaxillaries distinct from nasals ; no palatine arch ; astragalus and calcaneum 
elongate, forming a distinct segment of the limb Anura. 

The probable phylogeny of these orders as imperfectly indi- 
cated by paleontology is as follows ; 

* Probably includes the Gymnophiona. 



Urodela Trachystouiata * 



Emboloraeri Rhachitomi t 

Ganocephala I 

An examination of the above tables shows that there has been 
in the history of the Batrachian class a reduction in the number 
of the elements composing the skull, both by loss and by fusion 
with each other. It also shows that the vertebrae have passed from 
a notochordal state with segmented centra, to biconcave centra, 
and finally to ball-and-socket centra, with a great reduction of the 
caudal * series. It is also the fact that the earlier forms (those of 
the Permian ei)0ch) show the most Mammalian characters of the 
tarsus and of the pelvis. The latter forms, the salamanders, 
show a more generalized form of carpus and tarsus and of pelvis 
also. In the latest forms, the Anura, the carpus and tarsus are 
reduced through loss of parts, except that the astragalus and cal- 
caneum are phenomenally elongate. We have then, in the Batra- 
chian series, a somewhat mixed kind of change ; but it principally 
consists of concentration and consolidation of parts. The ques- 
tion as to whether this process is one of progression or retrogres- 
sion may be answered as follows : If degeneracy consists in "the 
loss of parts without complementary addition of other parts," then 
the Batrachian line is a degenerate line. This is only partly true 
of the vertebral column, which presents the most primitive char- 
acters in the early, Permian, genera (Ehachitomi). If departure 
from the nearest approximation to the Mammalia is degeneracy, 
then the changes in this class come under that head. The carpus, 
tarsus, and scapular and pelvic arches of the Eachitomi are more 
Mammalian than are those of any of their successors. || 

* The Trachystomata probably came from the Urodela by a process of degener- 
acy. See "American Naturalist," Dec, 1885. (Ed. 1886.) 

f Includes the Eryopidae. 

:|: Includes Trimerorhachidae and Archegosauridae ; and is distinguished from the 
Rhachitomi only by the presence of a single and cotyloid articulation of the skull 
with the atlas. 

* This reduction extends to the dorsal series as well. (Ed. 1886.) 

II This should read, than their latest, or anurous successors. (Ed. 1886.) 


There are several groups which show special marks of degen- 
eracy. Such are the reduced maxillary bones and persistent gills 
of the Proteida ; the absence of the maxillary bones and the 
presence of gills in the Trachystomata ; the loss of a pair of legs 
and feebleness of the remaining pair in the sirens ; and the ex- 
treme reduction of the limbs in Amphiuma. Such I must also 
regard, with Lankester, the persistent branchise of the Siredons. 
I may add that in the brain of the Proteid Necturus the hemi- 
spheres are relatively larger than in the Anura, which are at the 
end of the line. 

It must be concluded, then, that in many respects the Ba- 
trachia have undergone degeneracy with the passage of time. 


As in the case of the Batrachia, the easiest way of obtaining a 
general view of the history of this class is by throwing their prin- 
cipal structural characters into a tabular form. As in the case of 
that class, I commence with the oldest forms and end with the 
latest in the order of time, which, as usual, corresponds with 
the order of structure. I except from this the first order, the 
Ichthyopterygia, which we do not know prior to the Triassic 
period : * 

A. Extremities not differentiated in form beyond proximal segment. 

I. Os quadratum immovably articulated to squamosal, etc. 

Tubercular and capitular rib-articulations present and distinct. . .1. Ichthyojjterygia. 
AA. Elements of extremities differentiated. 

II. Os quadratum immovably articulated ; capitular and tubercular rib-articula- 

tions distinct. Archosauria. 
Pubis and ischium united, and with little or no obturator foramen ; one posterior 

cranial arch ; limbs ambulatory ; a procoracoid 2. Theromorpha. 

Ischium and pubis distinct, the latter directed forward, backward, or downward ; 
two posterior cranial arches ; limbs ambulatory ; no procoracoid 

3. Dinosauria.\ 
Ischium and pubis united ; two postcranial arches ; anterior limbs volant 

4. Ornithosauria. 

III. Os quadratum closely united to cranial arches ; but one rib-articulation. 

* Generally similar to the system published by me in " Proceedings Amer. Ass. 
Adv. Science," xix, p. 233. 

f This definition includes the Crocodilia in the Dinosauria, as it is absolutely 
connected with the typical Dinosaurs by the Opisthoccela (Sauropoda Marsh). 


Distinct hyposternal and postabdominal bones ; ribs joining each two vertebras, and 
generally forming a carapace ; one posterior cranial arch 5. Testudinata. 

Hyposternal and postabdominal bones not distinct ; two posterior cranial arches ; 
ribs attached to one vertebra ; a sternum ; ? no procoracoid 

6. Rhynchocephalia. 

Hyposternal and postabdominal bones not distinct ; two posterior cranial arches ; 
ribs attached to one centrum ; no sternum ; * a procoracoid . . 7. Sauropterygia. 

IV. Os quadratum attached only at the proximal extremity, and more or less 
movable; ribs with one head. Streptostylica.f 
Brain-case membranous in front of prootic bone ; trabecula not persistent 

8. Lacertilia. 
Brain-case with osseous walls anterior to prootic ; a scapular arch and sternum 

9. Pythonomorpha. 

Brain-case with osseous walls anterior to prootic ; no scapular arch nor sternum ; 

trabecular grooves of sphenoid and presphenoid bones 10. Ophidia. 

An inspection of the characters of these ten orders, and their 
consideration in connection with their geological history, will give 
a definite idea as to the character of their evolution. The history 
of the class, and therefore the discussion of the question, is limited 
in time to the period which has elapsed since the Permian ei3och 
inclusive, for it is then that the Keptilia enter the field of our 
knowledge. During this period but one order of reptiles in- 
habited the earth, so far as now known, that of the Theromori3ha. 
The important character and role of this type may be inferred 
from the fact that they are structurally nearer to both the Ba- 
trachia and the Mammalia than any other, but present characters 
which render it probable that all the other reptiles, with possibly 
the exception of the Ichthyopterygia, derived their being from 
them. The phylogeny may be thus expressed : 

Dinosauria Testudinata Rhynchocephalia Lacertilia Ophidia 


Pythonomorpha J 

Ichtliyopterygia Theromorpha 

* Episternum present. 

f It is quite possible that the three divisions of this head form one natural 
order, the Streptostylica, or Squamata. 

X Some unknown type of this order will represent the ancestor of the Ophidia, 
while the Lacertilia may have come directly from the Theromorpha. (Ed. 1886.) 


In the first place, this line departs with lapse of time from the 
primitive and ancestral order, the Theromorpha, in two respects : 
First, in the loss of the capitular articulation of the ribs, and, sec- 
ond, in the gradual elongation and final freedom of the suspensory 
bone of the lower Jaw (the os quadratum). In so departing from 
the Theromorpha, it also departs from the mammalian type. The 
ribs assume the less perfect kind of attachment which the mam- 
mals only exhibit in some of the whales, and the articulation of 
the lower jaw loses in strength, while it gains in extensibility, as 
is seen in the development of the line of the eels among fishes. 
The end of this series, the snakes, must therefore be said to be 
the result of a process of creation by degeneration, and their lack 
of scapular arch and fore limb and usual lack of pelvic arch and 
hind limb, are confirmatory evidence of the truth of this view of 
the case. 

Secondly, as regards the ossification of the anterior part of the 
brain-case. This is deficient in some of the Theromorpha, the an- 
cestral order, which resemble in this, as in many other things, 
the contemporary Batrachia. Some of them, however (Diadecti- 
dae), have the brain completely inclosed in front. The late orders 
mostly have the anterior walls membranous, but, in the strepto- 
stylicate series at the end, the skull in the snakes becomes en- 
tirely closed in front. In this respect, then, the latter may be 
said to be the highest or most perfect order. 

As regards the scapular arch, including the sternum, no order 
possesses as many elements as thoroughly articulated for the use 
of the anterior leg as the Permian Theromorpha, though the cor- 
acoid is of reduced size. In all the orders there is loss of parts, 
excepting only in the Ornithosanria and the Lacertilia. In the 
former the adaptation is to flying. The latter retain nearly the 
Theromorph type, enlarging the coracoid. An especial side de- 
velopment is the modification of abdominal bones into two pecul- 
iar elements to be united with the scapular arch into a plastron, 
seen in the Testudinata. In this part of the skeleton the orders 
are generally degenerate, the last one, the Ophidia, especially so. 

The pelvic arch has a more simple history. Again, in the 
Theromorpha we have the nearest approach to the Mammalia. 
The only other order which displays similar characters is the 
Ornithosanria (Dimorphodon, according to Seeley). In the Dino- 
sauria we have a side modification which is an adaptation to the 
erect or bipedal mode of progression, the inferior bones being 


thrown backward so as to support the viscera in a more posterior 
position. This is an obvious necessity to a bipedal animal where 
the vertebral column is not perpendicular, as in birds. And it 
is from the Dinosauria that the birds are sujiposed to have arisen. 
(Plates XV and XVI.) The main line of the Eeptilia, however, 
departs from both the mammalian and the avian type and loses 
in strength as compared with the former. In the latest orders, 
the Phythonomorpha and Ojohidia, the pelvis is rudimental or 

As regards the limbs, the degeneracy is well marked. No 
reptilian order of later ages approaches so near to the Mammalia 
in these parts as do the Permian Theromorpha. This approxi- 
mation is seen in the internal epicondylar foramen and well-devel- 
oped condyles of the humerus, and in the well-differentiated 
seven bones of the tarsus. The epicondylar foramen is only re- 
tained in later reptiles in the Ehynchocephalian Ilatteria (Dollo) ; 
and the condyles of the Dinosauria and all of the other orders, 
excepting the Ornithosauria and some Lacertilia, are greatly 
wanting in the strong characterization seen in the TheromorjDJia. 
The posterior foot seems to have stamped out the greater part of 
the tarsus in the huge Dinosauria, and it is reduced, though to a 
less degree, in all the other orders. In the paddled Sauroptery- 
gia, dwellers in the sea, the tarsus and carpus have lost all char- 
acterization, probably by a process of degeneracy, as in the mam- 
malian whales. This is to be inferred from the comparatively 
late period of their appearance in time. The still more unspecial- 
ized feet and limbs of the Ichthyosaurus (Ichthyopterygia) can 
not yet be ascribed to degeneracy, for their history is too little 
known. At the end of the line, the snakes present us with another 
evidence of degeneracy. But few have a pelvic arch (Stenostomi- 
dse Peters), while very few (Peropoda) have any trace of a poste- 
rior limb. 

The vertebrae are not introduced into the definitions of the 
orders, since they are not so exclusively distinctive as many other 
parts of the skeleton. They nevertheless must not be overlooked. 
As in the Batrachia, the Permian orders show inferiority in the 
deficient ossification of the centrum. Many of the Theromorpha 
are notochordal, a character not found in any later order of 
reptiles excepting in a few Lacertilia (Gecconidse). They thus 
differ from the Mammalia, whose characters are approached more 
nearly by some of the terrestrial Dinosauria in this respect. 


Leaving this order, we soon reach the prevalent ball-and-socket 
type of the majority of Eeptilia. This strong kind of articula- 
tion is a need which accompanies the more elongated column 
which itself results at first from the posterior direction of the 
ilium. In the order with the longest column, the Ophidia, a sec- 
ond articulation, the zygosphen, is introduced. The mechanical 
value of the later reptilian vertebral structure is obvious, and in 
this respect the class may be said to present a higher or more 
perfect condition than the Mammalia. 

In review it may be said of the reptilian line, that it exhibits 
marked degeneracy in its skeletal structure since the Permian 
epoch ; the exception to this statement being in the nature of the 
articulations of the vertebrae. And this specialization is an adap- 
tation to one of the conditions of degeneracy, viz., the weakening 
and final loss of the limbs and the arches to which they are at- 

The history of the development of the brain in the Eeptilia 
presents some interesting facts. In the Diadectid family of the 
Permian Theromorpha it is smaller than in a Boa constrictor, 
but larger than in some of the Jurassic Dinosauria. Marsh has 
shown that some of the latter possess brains of relatively very 
narrow hemispheres, so that in this organ those gigantic reptiles 
were degenerate, while the existing streptostylicate orders have 
advanced beyond their Permian ancestors. 

There are many remarkable cases of what may now be safely 
called degradation seen in the contents of the orders of 
reptiles,* Among tortoises may be cited the loss of the rib- 
heads and of one or two series of phalanges in the especially 
terrestrial family of the Testudinidae. The cases among the 
Lacertilia are the most remarkable. The entire families of the 
Pygopodidae, the Aniellidae, the Anelytropidae, and the Dibamidae 
are degraded from superior forms. In the Anguidae, Teidae, and 
Scincidae, we have series of forms whose steps are measured by 
the loss of a pair of limbs, or of from one to all the digits, and 
even to all the limbs. In some series the surangular bone is lost. 
In others the eye diminishes in size, loses its lids, loses the folds 
of the epidermis which distinguishes the cornea, and finally is en- 
tirely obscured by the closure of the ophthalmic orifice in the 

* Such forms in the Lacertilia have been regarded as dcgradational by Lan- 
kestcr and IJoulunger. 

















i: 1 

■ \ 

L ' ' j ' 

p^ I 

X ■; 

Vt -(^;. _, 

•■-,, ^''^ 



HIR' ^^ 


Diclonius mirabilis Hkull, one scvcLth natural size, from below. 


true skin. Among the snakes a similar degradation of the organs 
of sight has taken place in the order of the Scolecophidia, which 
live underground, and often in ants' nests. The Tortricidse and 
UropeltidEe are burro wing-snakes which display some of the earlier 
stages of this process. One genus of the true snakes even (accord- 
ing to Giinther) has the eyes obscured as completely as those of 
the inferior types above named (genus Typhlogeophis). 


The paleontology of the birds not being well known, our con- 
clusions respecting the character of their evolution must be very 
incomplete. A few lines of succession are, however, quite ob- 
vious, and some of them are clearly lines of progress, and others 
are lines of retrogression. The first bird we know at all com- 
pletely, is the celebrated Archeopteryx of the Solenhofen slates 
of the Jurassic period. In its elongate series of caudal vertebrae 
and the persistent digits of the anterior limbs we have a clear in- 
dication of the process of change which has produced the true 
birds, and we can see that it involves a specialization of a very 
pronounced sort. The later forms described by Seeley and Marsh 
from the Cretaceous beds of England and North America, some 
of which have biconcave vertebrae, and all probably, the American 
forms certainly, possessed teeth. This latter character was evi- 
dently speedily lost, and others more characteristic of the subclass 
became the field of developmental change. The parts which sub- 
sequently attained especial development are the wings and their 
appendages ; the feet and their envelopes, and the vocal organs. 
Taking all things into consideration, the greatest sum of progress 
has been made by the perching birds, whose feet have become 
effective organs for grasping, whose vocal organs are most perfect, 
and whose flight is generally good, and often very good. In 
these birds also the circulatory system is most modified, in the 
loss of one of the carotid arteries. 

The power of flight, the especially avian character, has been 
developed most irregularly, as it appears in all the orders in 
especial cases. This is apparent so early as in the Cretaceous 
toothed birds already mentioned. According to Marsh the Hes- 
peornithidge have rudimental wings, while these organs are well 
developed in the Ichthyornithidge. They are well developed 
among natatorial forms in the albatrosses and frigate pelicans, 
and in the skuas, gulls, and terns ; among rasorial types the 


sand-grouse, and, among the adjacent forms, the pigeons. Then 
among the lower insessores, the humming-birds exceed all birds 
in their powers of flight, and the swifts and some of the Capri- 
mulgidse are highly developed in this respect. Among the higher 
or true song birds, the swallows form a notable example. With 
these high specializations occur some remarkable deficiencies. 
Such are the reduction of the feet in the Caprimulgidae, swifts, 
and swallows, and the foetal character of the bill in the same 
families. In the syndactyle families, represented by the king- 
fishers, the condition of the feet is evidently the result of a pro- 
cess of degeneration. 

A great many significant points may be observed in the 
developmental history of the epidermic structures, especially in 
the feathers. The scale of change in this resj)ect is in general a 
rising one, though various kinds of exceptions and variations 
occur. In the development of the rectrices (tail-feathers) there 
are genera of the wading and rasorial types, and even in the in- 
sessorial series, where those feathers are greatly reduced or abso- 
lutely wanting. These are cases of degeneracy. 

There is no doubt that the avian series is in general an as- 
cending one. 


Discoveries in paleontology have so far invalidated the ac- 
cepted definitions of the orders of this class that it is difficult to 
give a clearly cut analysis, especially from the skeleton alone. 
The following scheme, therefore, while it expresses the natural 
groupings and affinities, is defective in that some of the defini- 
tions are not without exceptions : 

I. A large coracoid bone articulating with the sternum. 
Marsupial bones ; fibula articulating with proximal end of astragalus 

1. Jlfotiotirmata. 

II. Coracoid a small process co-ossified with the scapula. 

o. Marsupial bones ; palate with perforations (vagina double ; placenta and 
corpus callosum rudimental or wanting; cerebral hemispheres small 
and generally smooth). 

But one deciduous molar tooth 2. Marsupialia. 

aa. No marsupial bones ; palate entire (one vagina ; placenta and corpus 
callosum well developed). 
/3. Anterior limb reduced to more or less inflexible paddles, posterior 
limbs wanting (Mutilata). 


No elbow-joint ; carpals discoid, and with the digits separated by cartilage ; lower 

jaw without ascending ramus 3. Cctaccn. 

An elbow-joint ; carpals and phalanges with normal articulations ; lower jaw with 

ascending ramus 4. Sirenia. 

fifi. Anterior limbs with flexible joints and distinct digits ; ungual pha- 
langes not compressed and acute at apex* (Ungulata f). 
y. Tarsal bones in linear series ; carpals generally in linear series. 

Limbs ambulatory ; teeth with enamel 5. Taxeopoda.X 

yy. Tarsal series alternating; carpal series linear. 
Cuboid bone partly supporting navicular, not in contact with astragalus . 6. Proboscidia. 

777. Both tarsal and carpal series more or less alternating. 
Os magnum not supporting scaphoides ; cuboid supporting astragalus ; superior 

molars tritubercular 7. Amhlypoda. 

Os magnum supporting scaphoides; superior molars quadritubercular * 

8. Diplarthra.\ 
/3;3i8- Anterior limbs with flexible joints. Ungual phalanges compressed 
and pointed-^ (Unguiculata). 
e. Teeth without enamel ; no incisors. 

Limbs not volant; hemispheres small, smooth 9. Edentata. 

6€. Teeth with enamel ; incisors present. 
No postglenoid process; mandibular condyle round ; limbs not volant ; hemispheres 

small, smooth 10. Rodentia. 

Limbs volant ; hemispheres small, smooth 11. Chiroptera. 

* Except the Hapalidae. f Lamarck, "Zoologie Philosophique," 1809. 

X This order has the following suborders, whose association is now made for the 
first time : 

Carpal series linear ; no intermedium ; fibula not interlocking with astragalus ; no 

anapophyses ; incisors rooted ; hallux not opposable Condylartha. 

Carpal series linear; an intermedium; fibula interlocking with astragalus; hallux 

not opposable Hyracoidea. 

An intermedium ; fibula not interlocking ; anapophyses ; hallux opposable ; incisors 

growing from persistent pulps Dauhentonoidea. 

An intermedium ; fibula not interlocking ; anapophyses ; hallux opposable ; incisors 

rooted ; carpus generally linear Qiiadrumana. 

No intermedium ; * nor anapophyses ; carpal rows alternating ; incisors rooted 

A nthropoidea.^ 
The only difference between the Taxeopoda and the Bunotheria is in the unguli- 
form terminal phalanges of the former as compared with the clawed or unguiculate 
form in the latter. The marmosets among the former division are, however, fur- 
nished with typical claws. 

Some may prefer to use the term Primates in place of Taxeopoda, and such may 
be the better course. 

* Except Pantolestes. 

II This order includes the suborders Pcrissodactyla and Artiodactyla. It is the 
Ungulata of some authors. 
^ Except Mesonyx. 

* Except in Simia and Hylobates. t Includes the Anthropoid apes and man. 



A postglcnoid process ; mandibular condyle transverse ; limbs not volant ; no 
scapholunar bone;* hemispheres small, smooth 12. Bunotheria.\ 

A postgleuoid process ; limbs not volant, with a scapholunar bone ; hemispheres 
larger, convoluted 13. Carnivora. 

Paleontology has cleared up the phylogeny of most of these 
orders, but some of them remain as yet unexplained. This is the 
case with the Cetacea, the Sirenia, and the Taxeopoda. The 
last-named order and the Marsupialia can be supposed with much 
probability to have come off from the Monotremata, but there is 
as yet no j)aleontological evidence to sustain the hypothesis. Xo 
progress has been made in unraveling the phylogeny of the Ceta- 
cea and Sirenia. The facts and hypotheses as to the phylogeny 
of the Mammalia may be represented in the following diagram : 

Diplarthra Hyracoidea Insectivora Rodentia Chiroptera 

Proboscidea \ Anthropoidea / Edentata 








Marsupialia pt.| 


Marsupialia pt. 

It will be readily seen from the above diagram that the dis- 
covery of the Condylarthra was an important event in the history 
of our knowledge of this subject. This suborder of the Lower 
Eocene epoch stands to the placental Mammalia in the same rela- 
tion as the Theromorphous order does to the reptilian orders. It 
generalizes the characteristics of them all, and is apparently the 
parent stock of all, excepting, perhaps, the Cetacea. The dis- 
covery of the extinct Bunotherian suborders united together in- 
separably the clawed orders, excepting the bats ; while the extinct 
order Amblypoda is the ancestor of the most specialized of the 
Ungulates, the odd- and even-toed Diplarthra. 

The characters of the skeleton of the order Monotremata show 
that it is nearest of kin to the Eeptilia, and many subordinate 

* Except Erinaceus. 

f With the suborders Insectivora, Creodonta, Taeniodonta, and Tillodonta. 

t This was inadvertently omitted in the original. (Ed. 1886.) 


characters point to the Theromorpha as its ancestral source.* In 
the general characters the Marsupialia naturally follow in a rising 
scale, as proved by the increasing perfection of the reproductive 
system. The Monodelphia follow with improvements in the re- 
productive system and the brain, as indicated in the table already 
given. The oldest Monodelphia were, in respect to the structure 
of the brain, much like the Marsupialia, and some of the existing 
orders resemble them in some parts of their brain-structure. 
Such are the Condylarthra and Amblypoda of extinct groups, 
and the Bunotheria, Edentata, Rodentia, and Chiroptera, recent 
and extinct. The characters of the brains of Amblyj^oda and some 
Creodonta are, in their superficial characters, even inferior to ex- 
isting marsupials. The divided uterus of the recent forms named, 
also gives them the position next to the Marsupialia. In the Gar- 
ni vora, Hyracoidea, and Proboscidia, a decided advance in both 
brain-structure and reproductive system is evident. The hemi- 
spheres increase in size, and they become convoluted. A uterus 
is formed, and the testes become external, etc. In the Quadru- 
mana the culmination in these parts of tlie structure is reached, 
excepting only that, in the lacic of separation of the genital and 
urinary efferent ducts, the males are inferior to those of many of 
the Artiodactyla. This history displays a rising scale for the 

Looking at the skeleton, we observe the following successional 
modifications : f 

First, as to the feet, and (A) the digits. The Condylarthra 
Iiave five digits on both feet, and they are plantigrade. This char- 
acter is retained in their descendants of the lines of Anthropoidea, 
Quadrumana, and Hyracoidea, also in the Bunotheria, Edentata, 
and most of the Rodentia. In the Amblypoda and Proboscidia 
the palm and heel are a little raised. In the Carnivora and Dip- 
larthra the heel is raised, often very high, above the ground, and 
the number of toes is diminished, as is well known, to two in the 
Artiodactyla and one in the Perissodactyla. (B) The tarsus and 
carpus. In the Condylarthra the bones of the two series in the 
carpus and tarsus are opposite each other, so as to form continuous 
and separate longitudinal series of bones. This continues to be 

* "Proceeding3 American Philosoph. Society," 1884, p. 43. 
f Sec the evidence for evolution in the history of the extinct Mammalia. " Pro- 
ceeds. Araer. Assoc. Adv. Science," 1883. 


the case in the Hyraeoidea and many of the Quadrnmana, but in 
the anthropoid apes and man the second row is displaced inwards 
so as to alternate with the first row, thus interrupting the series in 
the longitudinal direction, and forming a stronger structure than 
that of the Condylarthra. In the Bunotherian Rodent and Eden- 
tate series, the tarsus continues to be without alternation, as in 
the Condylarthra, and is generally identical in the Carnivora. In 
the hoofed series proper it undergoes change. In the Proboscidia 
the carpus continues linear, while the tarsus alternates. In the 
Amblypoda the tarsus alternates in another fashion, and the car- 
pal bones are on the inner side linear, and on the outer side alter- 
nating. The complete interlocking by universal alternation of the 
two carpal series is only found in the Diplarthra. (C) As to the 
ankle-joint. In most of the Condylarthra it is a flat joint or not 
tongued or grooved. In most of the Carnivora, in a few Rodentia, 
and in all Diplarthra, it is deeply tongued and grooved, forming a 
more perfect and stronger joint than in the other orders, where 
the surfaces of the tibia and astragalus are flat. (D) In the high- 
est forms of the Rodentia and Diplarthra the fibula and ulna be- 
come more or less co-ossified with the tibia and radius, and their 
middle portions become attenuated or disappear. 

Secondly, as regards the vertebrae. The mutual articulations 
(zygapophyses) in the Condylarthra have flat and nearly horizon- 
tal surfaces. In higher forms, especially of the ungulate series, 
they become curved, the posterior turning upward and outward, 
and the anterior embracing them on the external side. In the 
higher Diplartha this curvature is followed by another curvature 
of the postzygapophysis upward and outward, so that the vertical 
section of the face of this process is an S. Thus is formed a very 
close and secure joint, such as is nowhere seen in any other 

Thirdly, as regards the dentition. Of the two types of Mono- 
tremata, the Tachyglossidse and the PlatypodidoB, the known gen- 
era of the former possess no teeth, and the known genus of the 
latter possesses only a single corneous epidermic grinder in each 
jaw. As the Theromorphous reptiles from which these are de- 
scended have well-developed teeth, their condition is evidently one 
of degeneration, and we can look for well-toothed forms of Mono- 
treraata in the beds of the Triassic and Jurassic periods. Perhaps 
some such are already known from jaws and teeth. In the mar- 
supial order we have a great range of dental structure, which almost 


epitomizes that of the Mouodelph orders. The dentition of the 
carnivorous forms is creodont ; that of the kangaroos is perisso- 
dactyle, and that of the wombats is rodent. Other forms repeat 
the lusectivora. I therefore consider the placental series espe- 
cially. I have already shown that the greater number of the types 
of this series have derived the characters of their molar teeth from 
the stages of the following succession. First, a simple cone or 
reptilian crown, alternating with that of the other jaw. Second, 
a cone with lateral denticles. Third, the denticles to the inner 
side of the crown forming a three-sided prism, with tritubercular 
apex, which alternates with that of the opposite jaw. Fourth, 
development of a heel projecting from the posterior base of the 
lower jaw, which meets the crown of the superior, forming a 
tubercular-sectorial inferior molar. From this stage the carnivo- 
rous and sectorial dentition is derived, the tritubercular type being 
retained. Fifth, the development of a posterior inner cusp in the 
superior molar, and the elevation of the heel in the inferior molar, 
with the loss of the anterior inner cusp. Thus the molars become 
quadritubercular, and opposite. This is the type of many of the 
Taxeopoda, including the Quadrumana and Insectivora as well as 
the inferior Diplarthra. The higher Taxeopoda (Hyracoidea) and 
Diplarthra add various complexities. Thus the tubercles become 
flattened and then concave, so as to form Vs in the section pro- 
duced by wearing ; or they are joined by cross-folds, forming vari- 
ous patterns. In the Proboscidia the latter become multiplied so 
as to produce numerous cross-crests. 

The dentition of some of the Sirenia is like that of some of 
the Ungulata, especially of the suilline group, while in others the 
teeth consist of cylinders. In the Cetacea the molars of the old- 
est (Eocene and Miocene) types are but two-rooted and com- 
pressed, having much the form of the premolars of other Mam- 
malia. In existing forms a few have simple conical teeth, while 
in a considerable number teeth are entirely wanting. 

A review of the characters of the existing Mammalia as com- 
pared with those of their extinct ancestors displays a great deal 
of improvement in many ways, and but few instances of retro- 
gression. The succession in time of the Monotremata, tlie Mar- 
supialia, and the Monodelphia, is a succession of advance in all 
the characters of the soft parts and of the skeleton which define 
them (see table of classification). As to the monotremes them- 
selves, it is more than probable that the order has degenerated in 


some respects in producing the existing types. The history of the 
Marsupialia is not made out, but the earliest forms of which we 
know the skeleton, Polymastodon (Cope) of the Lower Eocene, is as 
specialized as the most specialized recent forms. The dentition of 
the Jurassic forms, Plagiaulax, etc., is quite specialized also, but 
not more so than that of the kangaroos. The premolars are more 
specialized, the true molars less specialized than in those animals. 

Coming to the Monodelphia, the increase in the size and com- 
plication of the brain, both of the cerebellum and the hemi- 
spheres, is a remarkable evidence of advance. But one retro- 
gressive line in this respect is known, viz., that of the order 
Amblypoda,* where the brain has become relatively smaller with 
the passage of time. The successive changes in the structure of 
the feet are all in one direction, viz., in the reduction of the 
number of the toes, the elevation of the heel, and the creation of 
tongue and groove joints where plain surfaces had previously ex- 
isted. The diminution in the number of toes might be regarded 
as a degeneracy, but the loss is accompanied by a proportional 
gain in the size of the toes that remain. In every respect the 
progressive change in the feet is an advance. In the carpus and 
tarsus we have a gradual rotation of the second row of bones on 
the first, to the inner side. In the highest and latest orders this 
process is most complete, and, as it results in a more perfect me- 
chanical arrangement, the change is clearly an advance. Tlie 
same progressive improvement is seen in the development of dis- 
tinct facets in the cubito-carpal articulation, and of a tongue and 
groove (" intertrochlear crest ") in the elbow-joint. In the ver- 
tebrae the development of the interlocking zygapophysial articula- 
tions is a clear advance. 

Progress is generally noticeable in the dental structures ; for, 
unlike the marsupial line, the earliest dentitions are the most 
simple, and the later the more complex. Some of the types re- 
tain the primitive tritubercular molars, as the Centetidfe, shrews 
and some lemurs, and many Carnivora, but the quadritubercular 
and its derivative forms are by far the most common type in the 
recent fauna. The forms that produced the complicated modifica- 
tions in the Proboscidia and Diplarthra appeared latest in time, 
and the most complex genera. Bos and Equus, the latest of all. 
The extreme sectorial modifications of the tritubercular type, as 

* See "Naturalist," Jan., 1885, p. 55. 


seen in the Ilygenidoe and the FelidEe, are the latest of their line 

Some cases of degeneracy are, however, apparent in the mono- 
delphous Mammalia. The loss of pelvis and posterior limbs in 
the two mutilate orders is clearly a degenerate character, since 
there can be no doubt that they have descended from forms 
with those parts of the skeleton present. The reduction of flexi- 
bility seen in the limbs of the Sirenia and the loss of this char- 
acter in the fore limbs of the Cetacea are features of degeneracy 
for the same reason. The teeth in both orders have undergone 
degenerate evolution ; in the later and existing forms of the Ceta- 
cea even to extinction. The Edentata appear to have undergone 
degeneration. This is chiefly apparent in the teeth, which are 
deprived of enamel, and which are wanting from the premaxillary 
bone. A suborder of the Bunotheria, the Taeniodonta of the 
Lower Eocene period, display a great reduction of enamel on the 
molar teeth, so that in much-worn examples it appears to be 
wanting. Its place is taken by an extensive coat of cementum, 
as is seen in Edentata, and the roots of the teeth are often un- 
divided as in that order. It is probable that the Edentata are the 
descendants of the Taeniodonta by a process of degeneracy. 

Local or sporadic cases of degenerate loss of parts are seen in 
various parts of the mammalian series, such as toothless Mamma- 
lia wherever they occur. Such are cases where the teeth become 
extremely simple, as in the honey-eating marsupial Tarsipes, the 
carnivore Proteles, the Pteropod bats, and the aye-aye. Also where 
teeth are lost from the series, as in the canine genus Dysodus, and 
in man. The loss of the hallux and pollex without corresponding 
gain in various genera, may be regarded in the same light. 

In conclusion, the progressive may be compared with the re- 
trogressive evolution of the Vertebrata, as follows : In the earlier 
periods and with the lower forms, retrogressive evolution pre- 
dominated. In the higher classes progressive evolution has pre- 
dominated. When we consider the history of the first class of 
vertebrates, the Tunicata, in this respect, and compare it with 
that of the last class, the Mammalia, the contrast is very great. 






To exj)lain the origin of variation in animal structure is, par 
excellence, the object of the doctrine of evolution. There can be 
little doubt that the law of natural selection includes the cause of 
the preservation of certain modifications of pre-existent structure, 
in preference to others, after they have been brought into exist- 
ence. In what manner or by what process the growing tissues of 
young animals have been so affected as to produce some organ or 
part of an organ which the parent did or does not possess, must 
be explained by a different set of laws. These have been termed 
originative, while those involved in natural selection are restrictive 


Of course we naturally look to something in the " surrounding 
circumstances " in which a plant or animal is placed, or its " en- 
vironment," as the most probable stimulant of change of its char- 
acter, because we know that such beings are totally dependent on 
cosmic and terrestrial forces for their sustenance and preservation. 
The difficulty has been to connect these forces with change of 
s,iv\xQi\\ve Vi?, originative ; to show their operation as multiplying, 
restricting or destroying organisms already in existence is compar- 
atively easy. This difficulty is partially due to the fact that such 
modifications must be realized during a limited portion of the life 
of an animal at least ; that is, during the period of growth, when 
it is not at all or but little subject to the influence of external en- 
vironment, but is usually protected or supported by the parent. 

That the environment and changes in it affect the movements 



of plants and animals is clear enough. The potency of such 
changes may be read in the physical history of the earth. A long 
series of modifications preceded the advent of life upon it, and 
change, both gradual and sudden, has been exhibited in the con- 
figuration and climate of all portions of the surface of the globe 
since that period. Animals have again and again been called 
upon to face new conditions, and myriads of species have fallen 
victims to the inflexibility of their organization which has pre- 
vented adaptation to new surroundings. But it is evident that if 
change of environment has had any influence in the progress of 
evolution, it has not been alone destructive. It has preceded life 
as well as death, and has furnished the stimulus to beings capable 
of change, while it has destroyed those which were incapable of 
it. It is a truism that change of physical Conditions has preceded 
all great faunal changes, and that the necessity for new mechanism 
on the part of animals has always preceded the appearance of new 
structure in geologic times. 

The embryology and paleontology of vertebrated animals show 
that the primary steps in the progress of this branch of the animal 
kingdom are marked by the successive changes in the structure of 
the circulatory system. First we have the various mechanical 
methods for the aeration of blood in a watery medium ; the result 
being a fluid whose metamorphosis in nutrition produces no heat. 
After the fishes followed Batracliia, the earliest air-breathers, 
whose long tarriance to-day in early aquatic stages is an epitome 
of the necessarily " amphibious" character of air-breathing verte- 
brate life, when land and fresh water, in constantly changing 
areas, were rising and separating from the universal ocean. The 
successive disappearances of the traces of the fish type of circula- 
tion in Batracliia and reptiles, are familiar facts ; and the exclu- 
sion of the unaerated blood from the systemic circulation in the 
birds and mammals marks the increase of general temperature 
which gives those classes one of their claims to su])eriority. 

The appearance of land of course furnished the opportunity 
for aquatic animals to assume a terrestrial life. Marine animals 
which had acquired the habit of gulping air from the surface, 
which some of them now possess, perhaps because its richness in 
oxygen produced an agreeable exaltation or intoxication, would 
not find visits to the land difficult. And this would naturally 
follow the necessity of escape from aquatic enemies, or the search 
for new supplies of food. 


In fine, it requires little argument to show that the enyiron- 
ment has had in the past, as in the present, a primary influence 
over the movements of animals. 


I will now endeavor to exhibit some reasons for believing that 
the movements of animals affect their structure directly. 

There are two alternative propositions expressive of the rela- 
tions of the structures of animals to their uses. Either the use 
or attempt to use preceded the adaptive structure, or else the 
structure preceded and gave origin to the use. The third alter- 
native, that use and structure came into being independently of 
each other, is too improbable for consideration in the present 
article. Many facts render the first of these proj^ositions much 
the more probable of the two. 

A general ground for suspecting that movement affects struct- 
ure is the fact well known to systematic zoologists, that adaptive 
characters are the least reliable in systematic classification, i. e., 
are the most variable. What we call adaptive characters are 
those whose teleological significance we can most easily jDcrceive ; 
• those whose uses are at the present time most obvious. System- 
atists habitually fall back on characters which are apparently the 
least related to the ordinary necessities of the life of the animal, 
and this not from any theoretical considerations, but because such 
characters are found to be the most constant. This is a very sig- 
nificant fact, showing as it does that it is the adaptive structures 
which are undergoing modification to-day. And this truth can 
doubtless be discerned in all past ages, for many of the structures 
which are not now more related to the needs of an animal than 
many others might be, were at one time most essential to its well- 
being, or necessarily related to its environment. Such are the 
structural characters of the heart and arteries already enumerated. 
There seems to be no reason why all Vertebrata might not exist 
with equal comfort and success at the present if possessed of a 
uniform organization in this respect. But the successive modi- 
fications which they present were, in past ages, most intimately 
connected with the progressive changes of the medium in which 
they lived, as to the volume of oxygen supplied for respiration, 
as compared with that of the vapor of water, carbonic acid gas, 
etc. But it must be here noted, in passing, that there are many 
structures in animals which have never been adaptive, but which 


are simply due to excess or defect of nutrition following a redis- 
tribution of force.* 

The most direct evidence in support of the view that motion 
aifects structure directly is to be found in the well-known phe- 
nomenon of the increase of the size and power of all organs by 
use. This increase is limited in the adult animal by the general 
fixity of all the organs, so that one of them cannot be developed 
beyond a certain point without injury to others, or without ex- 
hausting the source of supply of nutritive material or special force 
derived from other organs. The syncope of the gymnast is an 
illustration of the natural limitation to the development of the 
muscular system which proceeds at the expense of the digestive 
and circulatory. But effort and exertion may become a habit of 
mind, v/hich, even if limited in its executive means, is probably in- 
herited by offspring like all other mental traits. Such a quality 
possessed by an infant or child doubtless tells on the growth of 
its organs during their plastic stage, and produces structure by 
growth which is impossible to the mature body.f And no one 
knows as yet how far mental bias may affect the nutrition of the 
parts of the infant in utero. Certain it is, that if use modifies 
nutrition in the adult, it must have still greater influence in the 
young ; and it is in the young that the changes which constitute 
evolution necessarily appear. 

Change of structure during groAvth is accomplished either by 
addition of parts ("acceleration") or by subtraction of parts 

Acceleration is produced either by multiplication of parts (as 
cells or segments) already present ("homotopy "), or by the 
transfer of parts (cells) from one part of the organism to the 
other ("heterotopy "). Homotopy or repetition is the usual and 
normal mode of acceleration ; it may proceed by an " exact repeti- 
tion" of the parts already existing, as in the simjilest animals and 
plants ; or the new parts may differ from the old, as in higher 
animals, where the process is called "modified repetition." Where 
new forms traverse in their growth all the stages in which they 
previously existed, they necessarily present at each stage the char- 
acters of those forms which have remained stationary in them, and 
have not changed. This relation of " exact parallelism " is the 

* "Method of Creation," 18Y1, p. 23. 
f In raan these changes are chiefly produced in the brain. 


result of the simplest form of evolution or ''palingenesis." When 
the history of growth of an advanced form does not show an 
identity between its stages and the various undeveloped or lower 
adult types, the relation is termed "inexact parallelism/' and the 
type of development " coenogenesis. " 

Change of structure is seen to take place in accordance with 
the mechanical effect of three forms of motion, viz.: hj friction, 
presstire and strain. Under the first two, epidermal tissues be- 
come both dense and thick, as is seen on the palms and soles of 
the hands and feet, and in corns. There is no doubt that strength 
of the teeth is intimately connected with the hardness of the 
food. Density of osseous tissue and the coossification of parts of 
the skeleton, are directly associated with the force and duration 
of muscular contraction. Pathology abounds in illustrations of 
the determination of nutrition to new localities to meet the exi- 
gencies and demands arising from new stimuli. It is only neces- 
sary for a structure-producing supply of nutritive material to be 
habitually determined to a new locality by oft-recurring stimulus, 
for the movement to become automatic and reflex ; and such a 
tendency would sooner or later be inherited, and produce struct- 
ure in the growing organism of the young to a degree far exceed- 
ing anything that is possible in the adult. 

In view of the above considerations, we can ascribe an exten- 
sive class of osseous projections at points of muscular insertion, 
to the strength and duration of muscular contractions. To the 
same cause may be ascribed various anchyloses, such, for instance, 
as is seen in the foot of the sloth. Transverse strains or their ab- 
sence may be looked upon respectively as the cause of the hinge- 
like or immovable articulations of the segments of the limbs of 
vertebrate animals. It is well known that in land animals, where 
easy flexibility of the limbs is essential to speed, these articula- 
tions are highly developed, while in marine animals, where the 
limbs are only used as paddles, they are almost or quite in- 
flexible, and the extremities of the bones are truncate. In the 
most highly organized land Mammalia, the tibio-tarsal and hu- 
mero-cubital articulations display an interlocking or tongue- 
and-groove character. The same thing is seen in the ulno- 
radial fixed articulation in the same types. These arrangements 
are especially adapted to prevent dislocation by side strains, 
and if the preceding explanations be true, this structure is 
a corrugation due to the lateral pressure of a more or less 


convex surface, on a concave one which embraces it, and vice 

In the circulatory system, pressure has doubtless played an im- 
portant part. Increased oxygenation of blood, the necessary con- 
sequence of the purification of the atmosphere, would stimulate 
the action of all the organs, including that of the heart. Greater 
pressure on its walls and septa would increase their size and 
strength, and ultimately close such foramina as were not in the 
course of the blood current, as the foramen septi ventriculorum 
of reptiles, and the/, ovale. Increased force of the current would, 
on the other hand, soon cause the enlargement of one or other of 
the four or five pairs of primary aorta bows, and develop it at the 
expense of the others, until finally the pre-eminence of one chan- 
nel be secured and the aorta be the result. This part of the sub- 
ject might be prolonged to an unlimited extent, but the above 
illustrations must suffice to indicate the meaning of my jDroposi- 


That movements change the environment of a plant or an ani- 
mal, or parts of them, is obvious enough. If we consider only 
the reflex class, to which all the movements of plants and many 
of those of animals belong, we perceive that but for them the or- 
dinary functions of assimilation, circulation, etc., could not be 
performed ; there would be no change in the contents of their 
tubes and cells, and the environment of these would be unaltered. 
But when we view the movements of the higher animals, we per- 
ceive the immense importance of the powers and organs of move- 
ment as a factor in evolution. It may be safely assumed that, 
without powers of designed or adaptive movement, life would 
never have advanced beyond the stage presented by the vegetable 

The stimuli which are effective in animal consciousness are 
four, viz.: excessive temperature, hunger, danger from enemies, 
and the reproductive instinct. These prompt to the movements 
which we observe in animals in a wild state, and without which 
it is evident that the animals themselves would soon cease to 

It can not be denied that organisms which arc incapable of 
moving from place to place in search of food, or of migration to 
escape vicissitudes of temperature, are much more completely sub- 


ject to the influences of their environment than those that are ca- 
pable of such movement. Hence animals are much more inde- 
pendent of the supply of food and of temperature than are plants. 
Hence also, other things being equal, the greater the powers of 
motion, the greater the independence. 

Powers of movement then enable animals to avoid extremes 
of climate by migrations or by protective arts. They enable them 
to procure food by making journeys in search of it, and by all 
methods of capturing it. They furnish the agent of active defense 
against enemies, and of successfully reproducing their kind. 

When, through changes of level of the earth's surface, drought 
has overtaken a region, animals capable of the necessary migrations 
have escaped. When an irruption of destructive animal enemies 
has threatened an animal population with death, those members 
of it whose strength or speed insured them safety, were the sur- 
vivors. When land has been encroached upon by water to such a 
degree as to bring starvation on its animal inhabitants, those which 
could fly or swim have sought new localities. 

Since all food-supply, as well as the ability to obtain food, is 
dependent on temperature, those portions of the organism which 
furnish means of resistance to climatic vicissitudes have the 
deepest significance in the life-history of any division of ani- 

The organs of circulation and motion are generally recognized 
as primary in the classification of Vertehrata. All situations where 
animal life is permitted by climate, support vegetable life also ; so 
each of the primary divisions of animals presents types adapted to 
the use of all kinds of food ; herbivorous, omnivorous, and carniv- 
orous. Accordingly, it has been found that dental and other 
structures connected with digestion define divisions of secondary 
value and minor extent. Paleontology shows that the origin of 
such divisions is of later date than that of the great classes first 
mentioned ; and each of the latter has in its day been modified in 
the subordinate directions indicated by the teeth and beak. But 
here also organs of movement are of great importance ; so that the 
herbivorous and carnivorous types at least, have ever in land ani- 
mals (reptiles, birds and mammals) been characterized by the 
structure of their feet also. 



It has been maintained above, that environmeut governs the 
movements of animals, and that the movements of animals then 
alter their environment. It has also been maintained that the 
movements of animals have modified their structure so as to render 
them more or less independent of their environment. The history 
of animal life is in fact that of a succession of conquests over the 
restraints imposed by physical surroundings. Man has attained 
to a wonderful degree of emancipation from the iron bonds that 
confine the lower organisms. 

It becomes then all important to examine into the elements in- 
volved in animal movements. 

These are of the two classes, reflex and conscious. To the 
former belongs the accelerated activity of muscular action and 
circulation, inferred to have accompanied increase in the percent- 
age of oxygen in the atmosphere, during the periods of geological 
time. To the consciously performed acts belong all those due to 
states of pain or pleasure in animals ; such as are excited by the 
four classes of stimuli already mentioned. 

Doubtless physical changes in the surrounding medium have 
always produced new reflex movements in animals, and have been 
a first element in evolution. Such has been the immediate cause 
of change of structure m plants, and in animals so far as they are 
unconscious. But consciousness brings with it limitless possibili- 
ties, since it places an animal in contact with innumerable stimuli 
which leave unconscious beings unaffected. All the causes which 
provoke the movements of higher animals are ajapeals to conscious- 
ness, and the consequences due to movements of such beings have 
only been possible through consciousness. 

It is evident then that sensibility to impressions has been the 
prime essential to the acquisition of new movements, and hence 
of new structure, other things being equal. Another essential, not 
less important, has been memory ; because without this faculty, 
experience, and hence education and the acquisition of habits of 
movement, are not possible. 

The ascending development of the bodily structure in higher 
animals has thus been, in all probability, a concomitant of the evo- 
lution of mind, and the progress of the one has been dependent 
in an alternating way on the progress of the other. The develop- 
ment of mind has secured to animals the greatest degree of inde- 


pendence of their environment of which they are capable. The 
first important acquisition leading to this end was aerial respira- 
tion ; the second, rapid nutrition by hot blood. And as essential 
to the production and preservation of these, improvements in 
organs of movement have been superadded to every successive 
type of life. 

Consciousness remains as the unresolvable factor in the process ; 
as at once the measure of, and respondent to a large class of phe- 




It is now apparent that the type of superior molar tooth which 
predominated during the Puerco epoch was triangular or trituber- 
cular ; that is, with two external and one internal tubercles.* 
Thus, of sixty-seven species of placental Mammalia of which the 
superior molars are known, all but four have three tubercles of the 
crown, and of the remaining sixty-five, all are triangular, except- 
ing those of three species of Periptychus, and three allied forms, 
which have a small supplementary lobe on each side of the median 
principal inner tubercle, f 

This fact is important as indicating the mode of development 
of the various types of superior molar teeth, on which we have not 
heretofore had clear light. In the first place, this type of molar 
exists to-day only in the insectivorous and carnivorous Marsupialia ; 
in the Creodonta, and the tubercular molars of such Carnivora as 
possess them (excepting the plantigrades). In the Ungulates its 
persistence is to be found in the molars of the Coryphodontidae of 
the Wasatch, and Dinocerata of the Bridger Eocenes. In later 
epochs it is occasionally seen only in the last superior molar. 

It is also evident that the quadritubercular molar is derived 
from the tritubercular by the addition of a lobe of the inner part 
of a cingulum of the posterior base of the crown. Transitional 
states are seen in some of the Periptychidse {Anisonclius), and in 
the sectorials of the Procyonid®. 

The tritubercular or triangular superior molar is associated 
with a corresponding form of the anterior part of the inferior 
molar. This kind of inferior molar J I have called the tubercular 

* See " American Naturalist," April, 1883, p. 407. 

\ This type is therefore only an extension of the tritubercular. (Ed. 1886.) 
X See Report G. M. Wheeler, D. Chief of Engineers on Explor. Surv. W. 100th 
Men, vol. iv, pt. ii ; on the Creodonta. 



sectorial, and is very variable as to the degree of development of 
the sectorial cutting edge. The anterior triangle is formed by 
the connection, by angle or crest, of the median and anterior in- 
ternal crests with the anterior external. Its primitive form is 
seen in Didelphys, Pelycodus, Pantolambda, and the Amblypoda 
generally ; in Centetes and Talpa ; and in its sectorial form, in 
Stypolophus and Oxyaena, etc. 

Fig. 64. — StypolopTma whiticB Cope, skull two thirds natural size. A Creodont 
from the Wasatch Eocene, displaying well the tritubercular superior, and the tubercu- 
lar-sectorial inferior molars. 

The mechanical action of such teeth is as follows : Of course, 
it results from the form of the superior molars that the spaces be- 
tween them are wedge-shaped, the apex external, the base open- 


ing to the palate. The base of the triangular section of the an- 
terior part of the inferior molar is interior, and the apex exterior, 
and when the jaws are closed this triangular prism exactly fits 
the space between the superior molars. The lower heel of the in- 
ferior molar receives the impact of the crown of tlie superior 
molar. Thus the oblique edges of the inferior triangle shear on 
the edges of two adjacent superior molars. The anterior parts of 
the inferior molars, and the superior molars, form an alternate 
dental series as distinguished from the prevalent opposed denti- 
tion of most Mammalia. In so far it resembles the reptilian 

This primitive dentition has been modified in two directions, 
viz., to form the grinding and the sectorial dentitions. As 
already remarked, the superior molars gradually acquire a pos- 
terior internal lobe, which produces the quadrituberculate type. 
This lobe, by opposing the anterior internal lobe of tlie next pos- 
terior inferior molar, precludes the entrance of the anterior trian- 
gle of the latter between the two superior molars. Hence we find 
in the types which possess quadritubercular superior molars, that 
the anterior triangle of the inferior molar is not elevated, if jores- 
ent, as, for instance, in Ehinocerus. It is, however, more fre- 
quently atrophied, and disappears, contributing to form the in- 
ferior quadritubercular molar so well known. 

On the other hand, as I have pointed out,* the anterior 
internal cusp of the triangle of the inferior molar may be more 
developed antero-posteriorly, giving the antero-internal edge of 
the triangle much greater obliquity than the postero-internal. 
In correspondence with this modification, the sujierior triangular 
molar loses its equilateral character by the more anterior j)osition 
of its internal angle, thus elongating the posterior internal side of 
the crown. The latter thus fits the corresponding form of the 
triangle of the inferior molar, forming with it the shear of the 
sectorial tooth. 

In a former article, *'0n the Homologies of the Molar Teeth," 
etc., I traced the modifications of the superior and many of the 
inferior molars of the ungulate mammals to a parent quadrituber- 
culate type. In a subsequent essay f I traced the origin of the 

* On the origin of the sectorial tooth of the Carnivora, " American Naturalist," 

f "Journal Academy Natural Sciences," Philadelphia, March, 1874. 



inferior sectorial to a primitive five-tubereled, or ''tubercular 
sectorial" type. Farther than this I did not go, and made no 
attempt to derive the few cases of triangular superior molars then 
known, nor the type of the superior sectorial. The revelations of 
the Puerco fauna show that the superior molars of both ungulate 
and unguiculate Mammalia have been derived from a tritubercular 

Fig. 65. — Deltatheriiim fundaminia Cope, skull and ramus mandibuli, two thirds 
natural size, from the Puerco beds of New Mexico. Fiss. a, J, c, from one individual. 
Fig. d, from a second animal. Ficr. «, right side of cranium ; h, palate from below ; c, 
mandible part, from above ; d^ left ramus, outer side. From the Eeport U. S. Geol. 
Surv. Terrs., vol. iii. Original. 

type ; and that the inferior true molars of both have been derived 
from a " tubercular sectorial " type. Shall we look for the origin 
of the latter in a tritubercular tooth also, i. e., tubercular sec- 
torial without heel ; and will the crowns of the true molars of the 
primitive mammals alternate with, instead of oppose each other ? 
This is a probable result of future discovery. 




The specially developed teeth of the Carnivora are the canines 
and sectorials. The former are large in many orders of Mam- 
malia, and their origin is probably to be sought among the Thero- 
morphous reptilia,* as Clepsydrops and Deiiterosaurus, if not in 
still lower types. The successive modifications of form which 
have resulted in the existing specialized single lower sectorial 
tooth of the Felid(B have been already pointed out.f They were 
shown to consist in the gradual obliteration of the internal and 
posterior, tubercles, and the enlargement of the external anterior 
tubercle in connection with an additional anterior tubercle. The 
modification in the character of the dentition, taken as a whole, 
was shown to consist in the reduction in the number of teeth, un- 
til in Felis, etc., we have almost the entire function of the molar 
series confined to a single large sectorial in each jaw. 

Observation on the movements of the jaws of Carnivora shows 
that they produce a shearing motion of the inferior on the su- 
perior teeth. This is quite distinct from the sub-horizontal 
movement of Ruminants, or the vertical motion of hogs and 
monkeys. Examination of the crowns of the sectorials shows 
that the inner side of the superior, and the external side of the 
inferior, are worn in the process of mastication. The attempt to 
cut the tough and stringy substances found in animal bodies is 
best accomplished by the shearing of the outer edge of the lower 
molar on the inner edge of the external tubercles of the superior 
molar, in an animal with simple tubercular teeth. The width of 
the mandible is too great to allow the inferior teeth to shear on 
the inner edge of the inner tubercles of the superior series. The 

* " American Naturalist," 18Y8, p. 829. 

f Cope, "Proceedings Academy Philada.," 1875, p. 22. 


Eijctnodon horridus Leidy, skull one half natural size. From the White Elver formation 
of Nebraska. From Leidy's " Extinct Mammalia of Dakota and Nebraska." 


cusps of both superior and inferior teeth engaged in this process 
have developed in elevation, at the expense of those not engaged 
in it, viz. : the internal cusps of the same teeth. The atrophy of 
the latter can not have been due to friction, since the internal 
cusps of the inferior series, which have not been subjected to it, 
are reduced like those of the superior sectorial, which have. In- 
deed, it is possible that some of the Creoclonta, the carnivores of 

Fig. 66. — Oxyozna lupina Cope, jaws, one half natural size, from the Wasatch beds 
of New Mexico. Fig. a, maxillary bone with teeth, from below ; A, last superior molar, 
from behind. Original; from the Report U. S. G. G. Survey W. of 100th Mer., G. M. 

the Lower Eocene, may have been derived from ancestors without 
or with rudimental inner cusps. In any case the effect of use in 
lengthening the external cusps appears to have operated in the 
Carnivora, as it has done to a greater degree in the Ungulata ; and 
the lateral vertical wear would appear to have resulted in the 
blade-form., as transverse wear in the Ungulates has resulted in 
the plane grinding surface. 

The specialization of one tooth to the exclusion of others as a 
sectorial, appears to be due to the following causes. It is to be 
observed, in the first place, that when a carnivore devours a 
carcass, it cuts off masses with its sectorials, using them as 
shears. In so doing it brings the part to be divided to the angle 
or canthus of the soft walls of the mouth, which is at the front of 
the masseter muscle. At this point, the greatest amount of force 
is gained, since the weight is thus brought immediately to the 
power, which would not be the case were the sectorial situated 
much in front of the masseter. On the other hand the sectorial 
could not be situated farther back, since it would then be inac- 
cessible to a carcass or mass too large to be taken into the mouth. 

The position of the sectorial tooth being thus shown to be de- 



pendent on that of the masseter muscle, it remains to ascertain a 
probable cause for the relation of the latter to the dental series in 

modern Carnivora. Why, for 
instance, were not the last 
molars modified into sectorial 
teeth in these animals, as in 
the extinct Hyanodon, and 
various Creodo7ita? The an- 
swer obviously is to be found 
in the development of the pre- 
hensile character of the canine 
teeth. It is probable that the 
gape of the mouth in the Hyse- 
nodons was very wide, since the 
masseter was situated relative- 
ly far posteriorly. In such an 
animal the anterior parts of 
the jaws with the canines had 
little prehensile power, as their form and anterior direction also 
indicates. They doubtless snapped rather than lacerated their 
enemies. The same habit is seen in the existing dogs, whose long 

F G. G7. — Procelurus julieni Filh., two 
thirds natural size. From the Phosphorites 
of France. From Filhol. 

^J»5Sf^lSS« V.^l^-SSVWV. 

Fig. 68. — Dinietis cyclops, one half natural size. From John Day Miocene of 
Oregon. Mus. Cope. From vol. iii, U. S. Geol. Surv. Terrs. 

jaws do not permit the lacerating power of the canines of the 
FelidcB, though more effective in this respect than those of the 
HycBnodons. The usefulness of a lever of the third kind depends 
on the approximation of the power to the weight ; that is, in the 


present case, the more anterior the position of the masseter muscle, 
the more effectire the canine teeth. Hence it appears that the rela- 
tion of this muscle to the inferior dental series depended originally 
on the use of the canines as prehensile and lacerating organs, and 
that its insertion has advanced from behind forward in the history 
of carnivorous types. Thus it is that the only accessible molars, 
the fourth above and the fifth below, have become specialized as 
sectorials, while the fifth, sixth, and seventh have, firstly, remained 
tubercular as in the dogs, or, secondly, have been lost, as in hy- 
enas and cats. 




The following considerations have been suggested by a study 
of the primitive types of the odd- and even-toed ungulates. I 
first, in 1874, recorded the oi^inion that the Mammalia with a 
reduced number of digits were derived from pentadactyle planti- 
grade types.* The ungulate order which fulfills this requirement 
is the Amhlypoda, and from them, I doubt not, both the Perisso- 
dactyla and Ai'tiodactyla have arisen, although not from any of 
the genera now known. Both of these great orders display a 
regular diminution in the number of the digits ; in the former, 
by reduction and extinction on both sides of the third digit ; in 
the latter, by reduction and extinction on each side of the third 
and fourth digits. Mr. John A. Ryder f has pointed out that 
reduction in digits is probably directly related to strains and im- 
pacts. He reminds us that the anterior digits are reduced \\\ 
Mammalia of unusual scansorial or fossorial powers ; while in 
forms which display powers of running, the reduction is seen first 
in the posterior feet, which propel the body much more than the 
fore feet. This view is well illustrated in the Perissodactyle 
families, the majority of which have the digital formula 4 — 3. 

No reason has ever been suggested, so far as I am aware, in 
explanation of the fact that one series of ungulates has retained 
two digits, and the other only one ; that is, why there should 
have been two kinds of digital reduction instead of one kind. In 
seeking for an explanation, we will remember tliat the tarsus in 
the odd or single-toed line is bound together by fixed articula- 
tions, while in the cloven-footed line it is interrupted by the hinge 
between the first (astragalus) and second rows of bones. The 
hinge-joint, being more liable to luxation than the fixed articula- 

* "Journal Academy Philadelphia," March, 1874. 
\ "American Naturalist," October, 1877. 


tion, requires a, wider basis of support, such as would be furnished 
by two divergent digits, rather than b}^ a single central one. 

In the early types, where the median digits are slender, the 
mechanical advantage in favor of the bidigital over the undigital 
arrangement is much more obvious than in modern genera. Late 
in time, the horse developed the middle digit to such a width as 
to form almost as good a support as the bidigital structure. In 
the Eocene genera, the slender median digit could not have sus- 
tained the weight on a hinge, without great risk of dislocation. 

Fig. to. 

Fig. 71. 

Fig. 70.— Eight posterior foot of a species of Corypliodon from New Mexico, one 
half natural size. From Eeport Expl. W. of 100th Mer., G. M. Wheeler, iv, PI. lix. 

Fig. 71.— Right posterior foot of the rhinoceros, Aphelops megalodus Cope, from 
Colorado, one half natural size. From Keport U. S. Geol, Surv. Terrs. F. V. Hayden 
iv, PI. cx.\x. 

This explanation, it can be said, applies only to the posterior foot. 
The posterior foot has, however, led the way in the evolution of 
Ungulata, and the fore foot may have followed in accordance 
with the law of antero-posterior symmetry in growth. A curi- 
ously malformed deer from Mendocino County, Cal., throws some 
light on this subject. It has apparently a single functional digit 
on each foot. Examination shows that the posterior foot is bi- 
digital, but that the phalanges are fused ; while the anterior foot 



is perissodactyle, all the digits but the third being rudimental ! 
Similar evidence is furnished by the genus Anoplotherium* of the 
French Eocene. Its posterior foot is modified artiodactyle, while 
the anterior is modified perissodactyle. We may assume from 


Fig. 72. Fio. 73. 

Fig. 72. — Right posterior foot of Protohippus sejundus Cope, from Colorado, about 
one half natural size. From Report U. S. Geol. Surv. Terrs. F. V. Hayden, iv. 

Fig. 73. — Right posterior foot of Fo'ebrotherium labiatutn Cope, from Colorado, three 
fifths natural size. From Hayden's Report, iv, PI. cxv. 

these facts, that the posterior foot is more subject to the influ- 
ences which tend to produce the bidigital structure than is the 
anterior limb. 

* Eurytherium Gorv. in the original, a name shown by Schlosser to apply to 
Anoplotherium. (Ed. 1886.) 


I suspect that the production of a ginglymus in the middle of 
the tarsus has been due to the use of the posterior limb in soft 
swampy ground. In the absence of this condition, as in a life on 
harder ground than swamp, no ginglymus would be formed. 
The action of an ungulate in walking through deep mud is very 
suggestive. The posterior foot is bent on the leg, and the antero- 
posterior strain of the weight or propulsive force is transverse to 
its long axis. In progression on dry land, the impact is in the 
direction of the length or axis of the foot. The obvious effect of 
a cross strain is to produce by degrees greater and greater mobility 
of some articulation. The one which has yielded is that between 
the two tarsal rows. Another effect of walking in swampy ground 
is to spread the digits apart. As the first digit 
of both feet is always of reduced size, there are 
practically but four digits to be considered. 
The weight falling nearly medially on these, 
would tend to spread them equally, two on 
each side. Thus the same cause may have been 
effective in producing both the artiodactyle 
structures. The perissodactyle structure, so 
soon as the lateral digits are much reduced, 
ceases to be favorable for progression in soft 
ground, owing to the liability of the lateral 
digits to injury, in following the principal one 
into the yielding material, filled with sticks 
and other hard debris. 

The lowest existing forms of the Artiodac- 
tyla, the Omnivora, are universally swamp 
lovers and livers. So, we are told, are the lower 
existing Perissodactyla, the tapirs and rhinoce- 
roses. The higher types of both orders are ^"^^ ^'*^ ^^""^ "^ '■'^- 
dwellers on plains and in forests. We do not ^.f^^^. ^eidy, from 
know the habits of the Eocene Perissodactyla, Colorado, three fiftim 
but I doubt their having inhabited muddy natural size. From 
ground to the same extent as the hogs and hip- pj^^^-kT^ ^cror , iv, 
popotami, the lowest of the Artiodadyla, Now, 
in progression on dry land, any pre-existent inequality in the 
length of the digits would tend to become exaggerated. Such an 
inequality exists in the Amblypoda, the third digit being a little 
the longer. In rapid movement on hard ground the longest toe 
receives the greatest part of the impact, even if its excess of 

Fig. 74.— Left fore 


length is but little. The harder the ground, the larger the pro- 
portion of impact it will receive. 

Tlie fact that the Perissodactyla did not develop the solid un- 
gulate or equine foot until a late geological period, or, in other 
words, that the orders so long retained the digital formula 4 — 3, 
would indicate that it did not adopt a habitat which required 
great speed as a condition of safety, so early as the Artiodactyla. 



The principal specializations in the structure of the feet of the 
Mammalia may be summarized as follows : 

I. The reduction of the number of the toes to one in the Peris- 
sodadyla (horses, etc.), and two in the Artiodadyla (cloven feet). 

II. The second hinge-joint in the tarsus of the Artiodactyla. 

III. The trochlear ridges and keels at the various movable 
articulations of the limbs. These are as follows : 

1. Looking downward — 

a, Intei'trochlear crests of the humerus. 
p. On the carpal end of the radius. 
7. Metacarpals, distal ends. 

6. Tibia distally. 

e. Metatarsals distally. 

2. Looking upward — 

a. Kadius distally. 
p. Astragalus, edges. 

7. Astragalus distally {Artiodadyla). 
6. Phalanges (very weak). 

The following observations may be made respecting the struct- 
ures included under Division III : The trochlear keels which look 
downward are much the most prominent and important. Those 
enumerated as looking upward are weak and insignificant, or of a 
different character from the down-looking ones. The latter are 
all projections from the middles of the ends of the respective ele- 
ments. The up-looking are generally projections of the edges of 
bones. Such are the lateral crests of the astragalus, and the ad- 
jacent edges of the cuboid and navicular bones which cause the 
distal emargination of the astragalus in the Artiodactyla. The 

* Read before the National Academy of Sciences, April, 1881. Abstract. Some 
of the points of tliis paper have already been discussed in the preceding article, but 
the present abstract contains additional matter. 


proximal ridges of the phalanges are very weak, and the concavities 
in the extremity of the radius can not be called trochlear, as they 
are adaptations to the carpal hones. 

I. The reduction in the number of toes is supposed to be due 
to the elongation of those which slightly exceeded the others in 
length, in consequence of the greater number of strains and im- 
pacts received by them in rapid progression, and the complement- 
ary loss of material available for the growth of the smaller ones. 
This is rendered probable from the fact that the types with re- 
duced digits are dwellers on dry land in both orders, and those 
that have more numerous digits are inhabitants of swamps and 
mud. In geological history it is supposed that the Perissodactyles 
(Figs. 72, 73) originated from the AmUypoda, or primitive Ungu- 
lata (Figs. 69, 70), which first assumed terrestrial habits, while 
the Artiodadyla (Fig. 74), originating from the same order, long 
continued as mud dwellers ; as witness the hippopotami and hogs 
of to-day. The mechanical effect of walking in the mud is 
to spread the toes equally on opposite sides of the middle line. 
This would encourage the equal development of the digits on each 
side of the middle line, as in the cloven-footed types. In progres- 
sion on hard ground, the longest toe (the third) will receive the 
greatest amount of shock from contact with the earth. There is 
every reason to believe that shocks, if not excessive, encourage 
growth in the direction of the force ap]")lied. This is strongly 
suggested by the relations between the length of the legs and the 
rate of speed of animals ; and the lengths of the teeth and their 
long-continued use. Certain it is that the lengths of the bones of 
the feet of the Ungulate orders have a direct relation to the dry- 
ness of the ground they inhabit, and the possibility of speed which 
their habitat permits them, or necessarily imposes on them. 

II. The hinge between the first and second series of tarsal 
bones in the Artiodactyla may be accounted for by reference to 
the habits which are supposed to have caused the cloven-footed 
character. Observation on an animal of this order walking in 
mud, shows that there is a great strain antero-posteriorly trans- 
verse to the long axis of the foot, which would readily cause a 
gradual loosening of an articulation like that connecting the two 
series of tarsals in the extinct Ambhjpoda. Any one who has ex- 
amined this part of Corypliodon will see that a little additional 
mobility at this point would soon resemble the second tarsal joint 
of the hogs. In the case of animals which progress on hard 


ground, no sncli cross-strain would be experienced, and the effect 
would be to consolidate by flattening the fixed articulation. 

III. The trochlege. These prominences, which form the 
tongues of the tongue and groove articulations, exhibit various 
degrees of development in the different Mammalia. Those of 
different parts of the skeleton coincide in their 
condition in any one type of ambulatory 31am- 
malia, and so may be all considered together. 
This fact suggests strongly that they are all 
due to a common cause. 

They are all imperfect in the Rodcntia and 
Carnivora (Figs. 75-77) (except the Leporidce, 
which are especially characterized by their great 
speed). Among ungulates they are very imper- 
fect in the Prohoscidea. 
The orders mentioned 
all have elastic pads on 
the under sides of their 
feet or toes. The same 
is true of the lowest 
types of both the Ar- 
tiodadyla and Perisso- 
dactyla, the hippopo- 
tami and rhinoceroses. 
In the Rumina7itia the 
trochleas are well de- 
veloped (Fig. 80) with 
one exception, and that 
is the distal metacar- 
pal and metatarsal 
keels of the Camelidce 
(Figs. 79, 81). These 
animals confirm the 
probability of the keels 
being the effect of long- 
continued shocks, for 
they are the only Ruminants which have elastic pads on the in- 
ferior sides of their digits. 

That these processes may be displacements due to shocks long 
continued, is rendered probable by the structure of the bones 
themselves. (1) They project mostly in the direction of gravity. 

Fio. T5. Fig. 76. Fio. 78. Fig. 77. 

Ficf. 75, Distal extremity of tibia of Amblyctonus 
sinosvs Cope. Fig. 76, Distal extremity of tibia of 
Oxyczna morsitans Cope. Both flesh-eaters, and two 
thirds natural size. From Eeport Expl. and Surv. W. 
of 100th Mer., G. M. Wheeler, iv, Pt. ii. 

Fig. 77, End of tibia and astragalus of ArcTicRlurus 
dehilis. Fig. 78, Femur of JVimravusr/omphodus. Car- 
nivora ; one third natural size. Mus. Cope. 



Constant jarring on the lower extremity of a hollow cylinder with 
soft (medullary) contents and flexible end walls, would tend to a 
decurvature of both inferior and superior adjacent end walls. If 

the side walls are wide and resistant, the 
projection will be median, and will be 
prolonged in the direction of the flexure 
of the joint. The groove of the astraga- 
lus deepens coincidently with the increase 
of digitigradism, showing that, while it 

is primarily pro- 
duced by shocks, 
it is extended 
fore and aft by 
the repeated flex- 
ure of the ankle- 
joint. (2) They 

Fig. 7'J. 

Fig. 80. 

Fio. 81. 

Fig. 79, Part of anterior foot of Proeamelus occidentalis from New Mexico. Orig- 
inal from Eeport of Capt. G. M. Wheeler, vol. iv, Ft. ii. 

Fi<i. 80, Metacarpals of Cosoryx furcatus from Nebraska, two thirds natural size, 
a, anterior face ; J, posterior ; c, proximal end ; 6?, distal end. 

Fig. 81, Left fore foot with part of radius of Poehrotheriimi vilsoni Leidy, from 
Colorado, three fitlhs natural size. From Hay den's Eeport, iv. 

fit entering grooves of the proximal ends of corresponding bones. 
These will be the result of the same ajiplication of force and 


displacement as the protrusion of the inferior, commencing with 
a concavity {Elephas) ; becoming more concave (Fig. 77), and 
becoming finally a gi'oove. (3) When the dense edge of a bone, 
as in the case of the lateral walls of the astragalus, is j)resented 
upward, a groove is produced in the down-looking bone ; e. g., 
the lateral grooves of the distal end of the tibia. (4) When the 
inferior bones are the denser, the superior articular face yields ; 
e. g., the distal end of the radius to the first row of carpals 
(Fig. 81). 

(5) The metapodial keels commence in the lower types on the 
posterior side of the distal extremity of the bone. This is partly 
due to the presence there of a pair of sesamoid bones which, with 
the tendons in which they are developed, sustain and press on the 
lateral parts of the extremities, and leave the middle line without 
support (Figs. 79-81). 







The complicated constitution of the human mind is well im- 
pressed on the investigator as he seeks to understand the origin 
of any one of the many different types of character which come 
before him. The number of possible combinations of its numer- 
ous elements, each of which present developmental phases, is 
necessarily very great. The species of human minds, as one may 
properly term them, are probably as numerous as the species of 
animals, as defined by their physical structure. As in the case 
of anatomical species, however, analysis of the mind reduces its 
many details to a few leading departments. Although the classi- 
fication of the elements of the mind is a classification of func- 
tions, it is, if correct, a sure index of the classification of struct- 
ure also ; of the grosser and more minute structure of the brain, 
principally of the gray matter. 

The division of mental activities into three primary divisions 
is generally admitted. These are : the emotions, the intellect, and 
the will. The emotions include tlie likes and dislikes, or the 
tastes, and their strongest forms, the emotions and the passions. 
The intellect includes those powers which rearrange the experi- 
ences in an order different from that in which they enter the 
mind. This new order may have sole reference to questions of 
liking and disliking, and is then a product of the imagination ; 

* The present article is in continuation of the previous one on the Evolutionary 
Significance of Human Physiognomy, published in the "Naturalist" of Jimc, 18S3. 


or it may be a result of experience of the laws of pure necessity, 
without regard to questions of taste ; then it is a process of rea- 
son. The will, properly so called, is the spontaneous power of 
the mind by which the other processes are originated, directed 
or restrained. The range of the will, and even its existence, are 
questions of dispute. 

Below and behind these mental activities lies sensibility or 
consciousness, in its forms of general and special sensation ; that 
is, touch and hearing, taste, smell, sight, and the muscular sense, 
with many others, concomitants of both health and disease. It is 
well understood that these primitive mental qualities are more or 
less developed in animals in which the more purely mental func- 
tions are rudimental. The doctrine of evolution teaches that 
from this class the higher activities of the mind have been devel- 
oped, during long ages, through the agency of memory. The 
nature of the present essay only permits a casual reference to the 
astonishing character of memory, and the remark that its phe- 
nomena demonstrate most clearly, of all others, that mind is an 
attribute of some kind of matter. 

If we now consider these natural divisions of the mind as they 
present themselves in the combinations which we call human 
character, we shall observe a variety in the mode of their action 
which pervades all divisions alike. These variations fall under 
two heads, those of quantity and of quality. 

Thus as to quantity ; one human mind may present a greater 
amount of intellectual than emotional activity ; of imaginative 
than rational intellection ; of affectionate than irascible emotion ; 
of gastronomic than musical taste, etc., etc. The quantity here 
indicated is probably an index of the proportion of brain tissue 
devoted to the functions mentioned. The intensity or force of the 
action is a matter of quality. 

Of qualities the variety is much larger. They are often paral- 
lel to those of inorganic force, and suggest the same kind of modi- 
fications of the material bases as those which affect the latter. 
Two prominent qualities are fineness and coarseness. Fineness 
observes and uses detail in both rational and emotive acts, and is 
essential to the precision of finish. Coarseness neglects detail, 
but deals with the gross of things, and is sometimes accompanied 
by largeness of quantity. When it is not, the result is not good. 
Fineness is, on the other hand, often associated with smallness. It 
is a more feminine attribute, while coarseness is more masculine. 


Another pair of antithetic qualities are intensity of action and 
the reverse. This probably means that a given bulk of brain 
tissue produces (i. e. , converts) a greater amount of energy in a 
given time than an equal bulk of non-intense tissue. 

The speed or rate of action in time, and its opposite, slowness, 
are related to the last-named qualities, but are not identical with 
them. Thus growth of the mind always witnesses a diminution 
in the rate of action, but an increase in intensity. 

Tenacity of mental action is a very marked character, and of 
great importance. It signifies the persistence of mental action, 
or mental endurance, and may characterize the entire mind, or 
only a part of it. Its opjjosite, seen in changeability, desultori- 
ness or fickleness, may also characterize all or a part only of the 
mind. According as it characterizes the intellectual or emotional 
departments are its exhibitions most varied, though they probably 
have a common histological basis. 

Itripressibility and stolidity express antitheses of character 
which are seen every day. The term impressibility is used as 
identical with irritability, and is preferred, because the latter has 
special physiological and popular meanings, some of which are 
only among its phases. These qualities are apt to pervade the 
entire mental organism, although, like others, they may char- 
acterize a part only. Impressibility is obviously a condition of 
tissue, since it varies greatly with physiological conditions in the 
same person. Its exhibitions in the department of the emotions 
may be confounded with strong development of the emotions 
themselves. A moment's thought, however, shows that easy ex- 
citation of emotion is a different thing from energy of emotion, 
and is often found ajjart from it. Impressibility of intellect 
shares with tenacity a leading position as an attribute of a first- 
class mind, and the combination of the two forms a partnership 
of superior excellence. 

I may mention here a quality whose absence is pathological, 
and hence does not properly enter the field ; this is tonicity. In 
its normal condition, every organ should be supplied with suffi- 
cient nutriment or energy to insure the occupation of its entire 
mechanism. Anything short of this is followed by poor work. 
Debility of mental action in the emotional department is seen in 
abnormal irritability, such as peevishness or "spooning" ; and in 
the intelligence, in absence of mind and blundering; and in both, 
in general frivolity. 


Keturning to the primary elements of mind, we may examine 
their divisions with reference to the question of growth. To be- 
gin with the perceptions, there are great diversities in the acute- 
ness of the general and special senses, and greater and less sus- 
ceptibilities to physical pleasure and pain. In the important 
representative faculty, memory, the differences between people 
are great. As perception as well as thinking involves a certain 
amount of structural change, it is evident that susceptibility or 
impressibility of the senses, which is the first stage of memory, 
signifies ready metamorphosis of tissue. Unimpressibility, which 
impedes memory, is a consequence of resistance on the part of 
tissue to the usual stimuli. Hence the effect of " sights, sounds, 
and sensations " is greatest in childhood, and the memory is most 
impressible, for at that time the nervous tissue is undergoing con- 
stant change, and nutrition, being in excess of waste, constantly 
presents new material to be organized. And I may here refer to 
the general truth, that consciousness of all kinds is the especial 
and distinguishing attribute of life as distinguished from death 
or no life.* Whatever other phenomena we may be accustomed 
to regard as "vital," are only distinguishable from inorganic 
motion or force, because they primitively took their form under 
the guidance of consciousness, and are hence, so to speak, its 
children. With the perfect working of most of the mechanism of 
the body, consciousness no longer concerns itself, although it may 
speedily do so in pathological conditions. This prerogative is 
now restricted to the nervous system, and to certain parts of it ; 
the one which is, histologically speaking, the most generalized of 
the systems. And it is quite consistent with the *' doctrine of 
the unspecialized," that nervous tissue in. its unfinished state in 
childhood should be more impressible to stimuli than at later 
periods of life. But this statement requires this modification, 
that there is a stage of imperfection of mechanism which does not 
display high sensibility, as, for instance, in the earliest infancy. 
With age sensibility gradually diminishes. 

Next in order of appearance in growth are the emotions. It 
is true that some of these are not fully developed until long after 
the appearance of many or all of the intellectual faculties ; but it 
is also true that their full development precedes that of the intel- 
lect, in so far as they arc developed at all. The primitive condi- 

* "The Origin of the Will," "Penn Monthly," 1877, p. 440. 


tion of the emotions is that of appetites. The first of these in 
the necessary physiological order, and hence in time, is the appe- 
tite of hunger. Second in order in the history of life, but not in 
the growth of individuals, is the instinct of repi'oduction, such as 
it is in animals that only multiply by fission. Very early in evo- 
lution the emotion of fear must have arisen, and it is probably 
the immediate successor of hunger in the young of most animals. 
Anger appears as early as the mind can appreciate resistance to 
its first desires, and no doubt followed as third or fourth in the 
history of evolution. The rudiments of parental feeling would 
follow the origin of reproduction at a considerable interval of 
time. One of the latest of the instincts to appear would be the 
love of power ; while later still would be the emotions of rela- 
tivity (Bain), because they are dependent on a degree of mental 
appreciation of objects. Such are admiration, surprise, and won- 
der. These, as well as all other consequences of inherited intel- 
lect, appear earlier in infancy than they did in evolution, as may 
be readily understood. 

Of these instincts and emotions, it is to be supposed that hun- 
ger remains much as it has ever been. The reproductive instinct 
has, on the other hand, undergone the greatest modifications. 
Sex instinct could not have existed prior to the origin of the 
male sex, which must be regarded in evolution as a derivative 
from the female. Hence it is probable that the parental instinct 
preceded the sexual in time. These two instincts being the only 
ones which involve interest in individuals other than self, furnish 
the sources of sympathy in all its benevolent aspects. Hence it 
has developed in man into the powerful passion of love ; into 
afifection and charity in all their degrees and bearings. Fear be- 
ing, as Bain shows, largely dependent on weakness, has varied in 
development in all times, but must be most pronounced in ani- 
mals of high sensibility, other things being equal. Hence its 
power has, on the whole, increased until it probably reached its 
extreme in the monkeys or the lowest races of men. Increasing 
intelligence of the higher order diminishes the number of its 
occasions, so that it is the privilege of the highest types of men 
to possess but little of it. The earliest of the emotions of rela- 
tivity to appear in time has probably been the love of beauty ; 
how early it may have appeared it is difficult to imagine. Sur- 
prise and wonder, as distinct from fear, one can only conceive as 
following an advanced state of intelligence. 


Thus in psychology as in physiognomy,* the paleontological 
order of development is somewhat different from the embryologi- 
cal. I might compare the two orders as follows : 


Hunger. Hunger. 
Reproduclion. Fear. 
Fear. Anger. 
Anger. Beauty. 
Parental instinct. Wojider. 
Sex. Power. 
Power. Admiration. 
Beauty. Pity- 
Wonder. Sex. 

Parental instinct. 

The qualities enumerated in the first column follow each other 
directly in order from the simple to the complex. In the second 
column this order is disturbed by the earlier appearance of the 
derivative emotions, beauty, wonder, admiration, and pity, or be- 
nevolence, and the later appearance of the simple emotion of sex. 
Thus in psychological as in other evolution, some of the products 
of development appear earlier and earlier in life in accordance 
with the law of acceleration. 

The intelligence has alreadv been considered under the two 
heads of the imagination and the reason. The action of the im- 
agination, unmixed with the exercise of reason, is chiefly to be 
seen in the creative fine arts, as distinguished from the imitative, 
the mechanic, and other arts. The musician, the painter, the 
sculptor, the poet, the novelist and the playwright, so far as they 
are not imitators, present the best illustrations of the work of the 
imagination. It is a faculty Avhich must be very little developed 
in the animals below man. They occasionally make mistakes in 
the nature of objects, and suppose them to be other than what 
they are. Thus the Antilocapra supposes the Indian disguised 
with a skin and horns to be one of his own species, and suffers 
the penalty. But this is a most rudimental act of imagination, if 
it be not mere curiosity. 

The reason, properly so called, begins in its lowest grades with 
the simplest re-arrangement of the objects of sense and memory, 
in accordance with some principle of relation. As the principle 
or standard of relation varies, so does the intellectual process. If 

♦"Naturalist," 1883, p. 618. 


the process be discovery, or the enlargement of knowledge, many 
experiences (or hj^potheses) will be successively encountered and 
tested, and a^jpropriate generalizations reached (inductions). If 
the process be to accomplish the practical ends of life by use of 
well-known means, the intellect uses the customary rules of action 
as standards, be they moral or mechanical, financial or political, 
and attains its deductions and applications. These two types of 
intellect are strikingly distinct, and produce the most diverse con- 
sequences. The inductive type is the most generalized, and hence 
capable of the largest growth and adaptability, and the widest 
range of thought. The deductive is the more specialized, the 
more *' practical," but less capable of growth or general thought. 
Its most remarkable exhibitions are seen in the skill with which 
some men conduct the game of chess, and corresponding enter- 
prises in real life. Also the ingenuity of mechanical invention, 
and the wonderful rapidity of calculation which some minds dis- 
play. In intellectual as in many other vital phenomena, the facil- 
ity once developed, the active process is often unaccompanied by 
consciousness in many or even all of its stages. 

Eapid and exact control of the muscles in obeying the direc- 
tions of the mind is essential to the practice of many arts, espe- 
cially to that of the musician. This accomplishment is acquired 
through the medium of the conscious mind, and may be regarded 
simply as the reflex of impressions made on the senses directed by 
some simple rule which has been impressed on the memory. The 
often surprising results involve the exercise of a very simple phase 
of intellection. 

The appearance of the rational faculties in time, may be esti- 
mated by their relative development in the existing divisions of 
animals whose j^eriod of origin is known or inferred. The ani- 
mal mind is capable of simple forms of induction and deduction, 
and sometimes acquires considerable artistic skill. Bees, ants and 
spiders disj)lay these in varying degrees, and their antiquity is 
probably co-extensive with that of the known sedimentary rocks. 
The supposed Ascidian ancestors of the Vertebrata, and even the 
lowest vertebrate (Branchiostoma), display far less intelligence than 
the articulates mentioned, which are really lower in the scale of 
organic types. From such unpromising sources did the noble verte- 
brate line descend. It is probable that the inductive act preceded 
by a little the deductive in time, as it does in logical order. But 
the elaboration of these powers was doubtless long delayed ; for 


untold ages they involved nothing more than the discovery and 
aj)plication of general principles of the simplest kind ; such as the 
customary sequence of natural phenomena, and the anticipation 
of their operations, as, for instance, in the laying up of winter 
provisions. Occasionally deductive application of an old rule to a 
new case would arise, as in that of the Mygale spider which was 
observed by Dr. McCook to substitute cotton for her own silk for 
the lining of her nest. The development of the rational faculty 
has been rather in quantity and quality, than in the nature of its 
constituent parts. I may remark, however, that the embryological 
order is here again different from the paleontological. Inherited 
aptitudes, as for music, calculation, etc., precede, in children, any 
considerable powers of thought, while the order of development of 
the race has been the reverse. 

As regards the appearance of the qualities of mind already 
mentioned, which depend on character of tissue, it is difficult to 
present an order which shall be generally true. Our ignorance 
of the subject is profound ; nevertheless observation of animals 
and men leads to the following conclusions : First, the primitive 
mind is negative, unimpressible, and little sensitive. In evolution, 
sensibility has been developed under stimuli, and diminished by 
disuse and repose. The energy of high-strung sensibility has prob- 
ably ever won for its possessors success in the struggle for existence, 
and more or less immunity from the pains which stimulate to ac 
tion.* It is true that the non-aggressive and ever-harassed Her- 
bivora have developed the higher brain structure. The inferiority 
of brain type of the Carnivora is a well-known fact of present and 
past time. The early ruminants were smaller than the contempo- 
rary flesh-eaters, and therefore subject to the greatest risks. The 
best-developed brains, those of the Quadrumana, have been devel- 
oped in still more defenseless animals, who in their arboreal life 
have been confronted by still more complex conditions. f 

Impressibility or sensitiveness has evidently been the means of 
acquisition of some of the other qualities mentioned. Thus inten- 
sity may have resulted from active use accompanied by vigorous 
nutrition, and the consequent construction of compact force-con- 
verting tissue. Rapidity without intensity must also result from 

* " The Relation of Man to the Tertiary Mammalia," "Penn Monthly," 1875. 

f Mr. C. Morris very reasonably regards tlie social life of these animals as the 

source of their development of intelligence. See " American Naturalist," June, 

1886. (Ed. 1886.) 


exercise, with a less vigorous construction of tissue. Fineness and 
tenacity, on the other hand, can not be regarded as being so much 
produced by use as by very primitive conditions of tissue. Re- 
straint under pressure might produce fineness. Long-continued 
freedom from sudden changes, under pressure, might account for 
the origin of tenacious tissue. As to quantity, deficiency or diver- 
sion of nutritive energy or material must produce smallness, and 
the reverse condition, largeness. 

These qualities impress themselves on the external as well as 
the internal organization, and can be more or less successfully dis- 
cerned by the observer. I reserve the question of physiognomy to 
a later article, and here consider only the evolutionary bearings of 
character itself. As in physiognomy, we may arrange the facul- 
ties and their qualities under the two heads of ancestral and embry- 
onic, or that of the species and that of the individual. The order 
of succession is the same in both kinds of development. 


Indifference. Indifference. 

Emotions. Emotions. 

Intellect. Intellect. 

a. Imagination. a. Imagination, 

b. Reason. b. Reason. 

It is not practicable to go farther than this into the order of 
evolution of characteristics. There is probably little uniformity 
of sequence other than that I have already pointed out under the 
head of the emotions. 

As a complex outcome of the emotional and rational faculties 
must be now mentioned the moral sense, or the sense of justice. 
It consists of two elements, the emotion benevolence, and the ra- 
tional power of discrimination or judgment. The former fur- 
nishes the desire to do what is right to a fellow-being. Without 
the aid of reason, it is benevolence, not justice, and may often fail 
of its object. The rational element has acquired from experience 
a generalization, the law of right. It perceives what is most con- 
ducive to the best interest of the object of benevolence in his rela- 
tion to others or to society, or whether he be a proper object of 
benevolence at all. By itself, this quality is absolutely useless to 
mankind. When it guides the action of human sympathy, it dis- 
plays itself as the most noble of human attributes. Many animals 
display sympathy and benevolence, but justice has not yet been 
observed in anv of them. Hence it has been said that it can not 


be a derivative faculty, but is "intuitive" in man. The objec- 
tion to this view is its great variability and occasional entire ab- 
sence in man, individually and racially. It is the last to appear 
in individual growth, as it has doubtless been in the order of evo- 
lution, of mind. 

I now devote a little space to the discussion of the distribution 
of these qualities in races and. sexes. 

As regards the relative preponderance in action of the emotive 
and intellectual faculties, it is an axiom that in the great majority 
of mankind, apart from the necessities imposed by the simple 
physical instincts, it is a taste or an affection or an emotion that 
lies at the basis of their activities. Perhaps the most universal is 
the affection of sex. Given two types of rational beings who are 
objects of admiration and of pleasure to each other, each of whom 
desires to possess the other, and. who therefore employs many de- 
vices to please and attract the other, and we have an effective agent 
of general development. Then tlie parental, and especially the 
maternal, affections arouse and direct many labors. Fear of suf- 
fering and death is at the basis of many others. The love of power 
or of possession, including ambition, is a well-known stimulus. 
The love of beauty is a strong motive in many persons. The 
pleasure derived from the exercise of the intelligence is a sufficient 
motive for a life-work in a comparatively small number of persons. 
These are the artists and the scientists ; but it is far from being an 
unmixed motive in many of them. 

Intellectual motives, however, enter into association with the 
affectional in many instances, as, for example, in the profession of 
teaching. But it is as guide and agent in the accomplishment of 
the main ends of life that the intellect, especially the reason, has 
its great field, and displays itself in an endless variety of ways. 

If we now survey men as we find them, it is a general truth 
that it is in the male sex that the greatest proportion of rational 
method is to be found, and in the female the greatest proportion 
of the affectional and emotional. As we descend the scale of 
humanity, the energy and amount of the rational element grows 
less and less, while the affectional elements change their propor- 
tions. The benevolent and sex elements diminish in force more 
rapidly than the other sentiments, but it is probable that all the 
emotions are less active in savages, excepting those of power and 
of fear. In the lowest races there is a general deficiency of the 
emotional qualities, excepting fear, a condition which resembles 


one of the stages of childhood of the most perfect humanity. To 
this must be added revenge, where hatred may be re-enforced by 
several other sentiments, with a feeble perception of equivalent 
suffering or punishment, which may or may not be just. The 
pleasure of muscular exercise is greatly developed in people of out- 
door habits. 

The order of the appearance of the intelligence is nearly de- 
pendent on the development of the powers of observation. In 
most savages these are very acute, and vary according to the na- 
ture of the environment which impresses them. The character 
of most civilizations tends to diminish the power of the percep- 
tive, while the higher departments of imagination and reason are 
enlarged. The imagination reached a high development before 
reason had attained much strength. With the exception of a few 
families, the intelligence of mankind has, up to within two or 
three centuries, expressed itself in works of the imagination. 
When exact knowledge first began to be cultivated, it was in the 
department of astronomy, where the least precision was attain- 
able, and where the greatest scope for the imagination is to be 
found.* Next in time metaphysics was the throne of learning, a 
field in which much may be said with the least possible reference 
to the facts of observation. With the modern cultivation of the 
natural and physical sciences, the perceptive faculties will be 
restored, it is to be hoped, to their true place, and thus many 
avenues opened up for the higher though t-jjower of a developed 
race. Thus it is that in the order of human development there 
is to be a return to the primitive powers of observation, without 
loss of the later acquired and more noble capacities of the intellect. 

The relation of the qualities of impressibility, fineness, inten- 
sity, speed and tenacity, to our development in time, may have 
been as follows : Impressibility of mind is no doubt an embryonic 
character of " retardation," parallel to, and probably a consequence 
of, the retardation which is also expressed in the human skull and 
face. The prejionderance of the osseous and nutritive elements 
over the nervous is the usual accompaniment of non-impressi- 
bility, and vice versa. Hence this quality is of late origin in the 

* The governments of antiquity required the knowledge of the Chaldean astrono- 
mers as important to the success of their undertakings, and the governments of 
Europe and America were, for a long period, more liberal in their support of as- 
tronomy than any other science. At present, howcvei', geology shares in this aid, 
and to a less degree botany and zoology. 


history of the Vertebrata and of man, and is most developed in 
the young, and better developed in women than in men. 

Tenacity has an opposite significance, being an especial charac- 
teristic of maturity in the human mind. Hence it may have been 
more general in early ages than at present, but could have little 
value so long as the mind remained small in quantity. Curiously, 
it is a quality which may co-exist with a good deal of impressibility. 

Fineness can only be a quality of full development, and is 
totally independent of the other qualities. It is unknown among 
savages, and is developed apparently in a few animals. Of inten- 
sity it is difficult to say much definitely. The nervous operations 
of animals often display the highest degree of this quality, and it 
is not unlikely that its appearances differ as much in savages as 
in civilized people. Its importance in mental action depends of 
course on the kind and amount of mental function which exhibits 
it. The same may be said of speed. The faculties which exist 
are more or less affected by it. In the well-formed reason it is an 
important characteristic, and a special form of development. 

Having gone as far into the origin and developmental relation 
of mental functions and qualities as the nature of this sketch per- 
mits, I refer briefly to the stimulus to their growth ; always re- 
membering that the percentage of inherited qualities is much 
larger in a given character than that of acquired ones. On this 
head one word expresses a good deal, and that word is use. No 
truth is better known than this one, that mental faculties develop 
with use more rapidly than those of any other organ of the human 
body. Brain and nerve are apparently the most plastic of all tis- 
sues ; the one which retains the properties of the primitive pro- 
toplasm, multiplied and intensified a thousand fold. It has al- 
ways been the seat of creation, throwing off its " formed matter " 
in useful directions. It is still doing so ; and in the human 
brain, ever creating itself, is in addition the seat of a new creation, 
which it executes through its instruments, the other organs of 
the body. Hence the greatest sin against the brain is idleness, 
or disuse. The brain activity of to-day is an indication of health 
and happiness beyond what the world has seen hitherto. 

The greatest stimulus to exercise of the brain is human soci- 
ety. Hence the greatest developments of mind have always been 
in the centers of population. Whatever may be the passive vir- 
tues of country life, it is the cities that furnish both the stimulus 
and the field for the triumphs of mind. 




The evidence of what is termed "design " in the structure of 
beings exhibiting life, is often appealed to by one class of think- 
ers, as proving the intervention of a personal Deity in the crea- 
tion of such ; and the same feature exhibited in the movements 
of living creatures is regarded by metaphysicians of a similar class 
as an indication of their possession of a power of choice, or "free 
agency," at least in the case of man. The opposing school, of 
whom Professor Bain may be selected as an example, believes that 
designed acts are Avithout an element of freedom, but are simply 
performed in obedience to stimuli of various kinds, motion fol- 
lowing stimulus as inevitably as effect succeeds cause in the non- 
living world. The evolutionists attempt to explain design in 
structure through the operation of the Darwinian law of the 
"survival of the fittest," showing that only those beings whose 
organization displays that adaptation to use in relation to its sur- 
roundings, which is termed "design," could possibly continue to 
exist. It is justly urged against this reasoning that it attempts 
no explanation of the origin of such structures. Another school 
of evolutionists have therefore maintained that such structures are 
due to the effect of effort, i. e., stimulus or use, exerted by the 
living being on its own body, and that the design thus displayed 
is an expression of the intelligence at some time possessed by itself. 

So long as there is any probability of the last explanation 
proving valid, it will be important to examine into the questions 
of metaphysics which it necessarily involves. The investigation 
is indeed but the necessary projection of those which have re- 
sulted in satisfying the great majority of biologists of the reality 
of evolution, or of the fact of the descent of existing living beings, 

* A lecture delivered before the Franklin Institute, Pliiladelphia, February, 18V4. 



species by species, order by order, and class by class, from others 
which have preceded them in time. Clearly, then, we enter the 
question by considering the nature of movements of plants and 
animals in relation to the stimuli which are suj^posed to call 
them forth. 


A true study of metaphysics necessarily has for its objects 
plants, animals, idiots, and infants, as well as healthy men ; never- 
theless, necessity compels us, in discussing the question, to dwell 
on our own experiences as a sine qua noti. Now experience, in a 
general sense, includes not only the memory of our conscious acts, 
but a knowledge of our unconscious ones, and to the latter espe- 
cial attention must be directed, since they are most readily over- 
looked. The marvelous character of memory can not be too 
much considered. Of the millions of impressions which the mind 
has received and registered, in the course of a lifetime, but one 
can be clearly present in consciousness at one time. The remain- 
ing millions are not lost ; they are stored, each in its appropriate 
place, to be sprung into consciousness when the appropriate 
suggestion presents. How much more vast, from this point of 
view, is the unconscious mind than the conscious ! But the 
phenomenon is not confined to memory. Who that has ever at- 
tempted the digestion of a subject which includes a mass of de- 
tails, is not acquainted with the unconscious activity of the mind 
in classification ? How frequently a question involving many 
parts, is, on the first reception of the constituent facts, all con- 
fusion ; but in time displays its symmetry clearly to the con- 
sciousness, every part in its proper place, and that with little or 
no further attention having been dgvoted to it. It is indeed proba- 
ble that the every-day process of inductive reasoning is conducted 
in unconsciousness on the part of the subject. Induction con- 
sists in the generalization of some quality as common to a great 
number of objects of memory ; a greater or smaller number of 
other qualities being neglected in the process. When this act is 
performed voluntarily, one or many qualities are successively 
passed in review before the mind — each one being in its turn im- 
pressed on the perceptive centers — so long as it is the object of 
inquiry, the others being excluded from consciousness for the 
time being. It is simply a process of classification, and when per- 
formed in consciousness, constitutes "experiment." But when 


no generality is anticipated, and its existence is unlcnown, it often 
happens that such generalization becomes known or rises into con- 
sciousness, without the bestowal of effort in classification of the 
objects to which it refers. The impressions consciously received 
have been arranged out of consciousness, and when revived into 
consciousness display an order which was not previously known 
to exist. It is in the latter way that the "practical man " "finds 
out " the rules by which, as by an instinct, he regulates his inter- 
course with the world. He often can not explain the reasons of 
their truth, nor does he know how he came by them, being gen- 
erally content to call them the results of " experience." In some 
persons they are so feebly expressed in consciousness as to be called 
"feelings" ; and many experiences or repetitions are sometimes 
necessary to impress on us the importance of these mental prod- 
ucts before we are willing to follow them in action. " Strength 
of mind " is an expression applied to a high degree of this uncon- 
scious reasoning ; expressing the extent of ground the process 
covers continuously, as well as the exactitude of its results. The 
experimental investigator, on the other hand, performs this work 
deliberately, and is acquainted with the processes ; he is, there- 
fore, at first more confident of his results. And we observe here, 
in passing, that a rule once discovered is as readily retained in 
the cells of the unconscious as is the memory of a simple object 
or event. 

Another form of unconscious cerebration is seen in deductive 
reasoning, which employs rules already discovered in application 
to new cases. Calculating prodigies are a case in point. It is 
well known that those persons who have from time to time ap- 
peared possessed of the power of calculating with enormous num- 
bers with marvelous rapidity, have never been able to explain the 
process by which they reach their conclusion, nor are they con- 
scious of going through the steps involved in the calculation they 
perform ; and it has been said that great calculators have rarely 
been great mathematicians. 

The explanation of these phenomena is not far to seek. In 
simpler forms it is presented to us every day. Thus it is an easy 
matter to read with but little consciousness of the process, and no 
recollection of the subject-matter of what is read. Most manual 
operations can be performed while the consciousness is occupied 
with other objects. 

If these be facts of human experience, how much more likely 


are they to be true of animals ? If man be unconscious of the 
process during the performance of some of his most complex acts, 
how much more probable is it that animals are so while pursuing 
the narrower circle of their simpler ones ? Yet animals are not 
devoid of consciousness ; indeed, it is scarcely credible that any 
one should deny to them consciousness, after experience in their 

But let these automatic acts be ever so simple or complex, it is 
here claimed that they could not have originated out of conscious- 
ness. Whatever we call voluntary acts in ourselves undoubtedly 
have to be learned. The acquisition of the primary act of walking 
is accomplished by a slow and painful education ; while knitting 
and other manual exercises necessarily require preliminary train- 
ing, some of shorter, others of longer, duration. This is true of 
such voluntary acts as we perform most readily automatically, and 
such as might be supposed to be most probably acquired by heredi- 
tary transmission, as for instance speaking. The case is the same 
with animals. All those services which are useful to us, or tricks 
which amuse us, are acquired at the expense of training, which 
involves a system of stimuli, consisting of rewards and punish- 
ments, as in our own species. Is there any reason to suppose that 
those habits which we observe them to jjossess in a state of nature 
have had a different origin ? 

It is incontrovertible that a regular succession of muscular 
movements may be committed to memory as certainly as a color 
or a shape, and that a change of brain substance, such as causes 
the retention of the simple impression, is also involved in the 
retention of the complex. When this machinery is completed, 
through the repetition of conscious stimulus, it works thenceforth 
without necessary intervention of consciousness. The conscious- 
ness may then be engaged in fresh acquisitions, accomj)lishing new 
organizations, thus accumulating a store of j^owers. Once organ- 
ized, these powers are at the disposal of their possessor, yet the 
organized machine will at some time undergo change, if not more 
or less frequently used. Without use it may indeed finally disap- 
pear, showing that the capacity for organization is identical with 
a facility of disorganization. 


Is any habit originated in unconsciousness ? Those who affirm 
this proposition point to the movements of plants in the extension 


of their tendrils, and the closing of some sensitive leaves ; the 
timely expansion of the down of the Asclepias seed, and the in- 
sect-catching habits of Droscra and Dioncea. No one surely 
attributes consciousness to these. And there are many similar 
movements in animals which are as thoroughly unconsciously 
performed as are those of plants, from the first moment of the ani- 
mal's birth ; as, for instance, the involuntary activities of the cir- 
culatory and digestive systems, etc. Did these originate in con- 
sciousness or unconsciousness ? The answer to this question 
constitutes the key to the mysteries of evolution, and around it 
the battle of the evolutionists of the coming years will be fought. 

It may be asserted at the outset that those habits whose origin 
we have had the opportunity of observing in ourselves and in other 
animals were certainly acquired in consciousness, and that we do 
not believe that they could have originated out of it. The stimuli 
to action are divided into the two general classes of pleasures and 
pains, and each stimulus is potent in proportion to the intensity 
with which it is consciously apprehended. If many and complex 
acts may be performed automatically, through the organization of 
special machinery in the gray matter of the brain, it is altogether 
reasonable that similar powers should be found to be conferred on 
gray nervous tissues in parts of the body which are no longer seats 
of consciousness. It is well known that the spinal cord of the head- 
less frog responds to stimuli, in the vigorous muscular contractions 
of the limbs which follow the application of acid to the skin. So 
the ganglionic centers of organic life respond to their appropriate 
excitants ; the various glands of the digestive system discharging 
their contents into the ingesta at the proper moment, conscious- 
ness having no share in the proceeding. These phenomena are 
more readily explained on the theory of endowment than on that 
of physical movements ; since by means of the former the evident 
design in the movements is accounted for, while the latter gives us 
no clew to this characteristic feature of these and all other vital 

The lowest form of consciousness is common sensibility ; and, 
judging by the resemblance between our own experience and that 
of the higher animals, the lowest of animals also are not devoid 
of this quality. The structureless jelly of Ehizopods, such as 
Amcebas, Groraias, etc., evidently selects its food with regard to 
its nutritious qualities, in most instances preferring diatoms and 
desmids to sand and other innutritious substances. Its acquisi- 


tions in knowledge of articles of food can only be accounted for 
on the hypothesis of original, pleasurable or joainful, conscious- 
ness of the effects of external and internal contact with these sub- 
stances, and retention of the impression in unconsciousness. The 
impression reviving on the recurring of a similar contact, the sub- 
stance is accepted or rejected as the former sensations were pleas- 
urable or painful. And this is not incredible, if, as the researches 
indicate, the structure of the protoplasm of these creatures is of 
the same type as that of the bioplastic bodies of the gray tissue of 
the brain. 

In accordance with this view, the automatic "involuntary" 
movements of the heart, intestines, reproductive systems, etc., 
were organized in successive states of consciousness, which con- 
ferred rhythmic movements, whose results varied with the ma- 
chinery already existing and the material at hand for use. It is 
not inconceivable that circulation may have been established by 
the suffering produced by an overloaded stomach demanding dis- 
tribution of its contents. The structure of the Coelenterata offers 
the structural conditions of such a process. A want of propul- 
sion in a stomach or body sack occupied with its own functions 
would lead to a painful clogging of the flow of its products, and 
the "voluntary" contractility of the body or tube-wall being thus 
stimulated, would at some point originate the pulsation necessary 
to relieve the tension. Thus might have originated the " con- 
tractile vesicle" of some protozoa, or contractile tube of some 
higher animals ; its ultimate product being the mammalian heart. 
So with reproduction. Perhaps an excess of assimilation in well- 
fed individuals of the first animals led to the discovery that self- 
division constituted a relief from the oppression of too great bulk. 
With the increasing specialization of form, this process would be- 
come necessarily localized in the body, and growth would repeat 
such resulting structure in descent, as readily as any of tlie other 
structural peculiarities. No function bears the mark of conscious 
origin more than this one, as consciousness is still one of the con- 
ditions of its performance. While less completely "voluntary" 
than muscular action, it is more dependent on stimulus for its 
initial movements, and docs not in these disjilay the unconscious 
automatism characteristic of the muscular acts of many other 

Bearing in mind the property of protoplasm to organize ma- 
chinery which shall work automatically in the absence of con- 


sciousness, we can glance at the succession of vegetable forms. 
The active movements of the primary stages of the Algag are well 
known. After swimming actively through the Avater, they settle 
down, take root, and assume the role of plants. The Aetlialium, 
swimming with the movements of a Rhizopod, has been known to 
take food before establishing itself on the damp piles of the tan- 
bark, where it speedily becomes a low form of fungus. The ap- 
proximation of the lower forms of plants to animals is notorious. 
The fungi, it is said, are the only terrestrial jolants which live like 
animals on organic matter, appropriating the humus of their rich 
nidus in a state of solution. Now the paleontology of animals has 
absolutely established the fact that the predecessors of all charac- 
teristic or specialized types have been unspecialized or generalized 
types, " neither one thing nor another." It may then be regarded 
as almost certain that the ancestors of the present higher types 
of plants were more animal -like than they ; that the forms dis- 
playing automatic movements were more numerous, and the diffi- 
culty of deciding on the vegetable or animal nature of a living- 
organism greater than it is now. Hence it may be concluded that 
''animal" consciousness has from time to time organized its ma- 
chinery and tlien disappeared forever, leaving as result the per- 
manent form of life which we call vegetable. But it is not to be 
supposed that all changes of structure cease with the departure of 
consciousness. Given spontaneous movement (i. e., growth), and 
surrounding conditions, and the resultant product must be struct- 
ures adapted to their surroundings, just as the plastic clay is fitted 
to its mold. And this is essentially the distinguishing character 
of vegetable teleology as compared with animal. In the average 
plant we see adaptation to the conditions of unconscious nutrition ; 
in the animal, adaptation to conditions of conscious contact with 
the world under a great variety of conditions. 


The active processes of living beings are examples of conversion 
of physical forces, only differing from the conversions observed to 
take place in inorganic bodies, in the nature of the machinery 
which exhibits them. The construction of this machinery, as in 
its use when finished, involves a conversion of force, the resultant 
consisting of the attraction of nutritious material in definite new 
directions. This determinate attraction has been regarded as a 
distinct force, to which the name of bathmic or growth force has 


been applied. It differs from all the physical forces in this, that 
while they are only exerted inversely as the square of the distance, 
this one is in addition most excessive where pleasure has been ex- 
perienced, and weakest where pain has left its deepest traces. In 
other words, its movements express design, the essential condition 
of which is consciousness. It is thus evident that it differs utterly 
from all other forces, although a retrograde metamorphosis of mat- 
ter is as necessary for its production as for that of any of the other 
forces. Now, although the evidences that stimulated consciousness, 
or if you choose, mind, can modify structure, are, as matter of 
observation, not very satisfactory ; yet, since the essential pecul- 
iarity of growth-force is its instant attendance on the needs of 
consciousness, it is a permissible hypothesis that its activity is 
immediately due to consciousness. This activity is located in 
bioplasts which do not exhibit consciousness ; whether it co-exists 
with consciousness in brain bioplasts is unknown. The successive 
exhibitions of this force, from the lowest to the highest of living 
beings, have ever been additions to the executive machinery of a 
more and more specialized consciousness. Thus it is that its re- 
sults in structure have ever become more and more complex, that 
is, composed of an ever-increasing number of parts in some region 
of the organism. Hence another point of distinction from other 
forces exists, which has been pointed out in a previous paper. It 
is quite evident that the higher forms of life are the result of con- 
tinued superaddition of one result of growth-force on another, 
some examples of subtraction or simplification of parts being gen- 
erally accompanied by a great preponderance of additions. This 
is evidence of the accumulation of the property of pi'oducing this 
kind of force, since each successive addition imposes on the grow- 
ing animals a great number of successive stages before the process 
reaches its termination, maturity. This involves the belief that 
the property of exhibiting frequent "repetitions" of growth-ac- 
tivity exists in a higher degree in the reproductive bioplasm of the 
more complex animal than in that of the lower ones. This is in 
. accordance with the fact of the regular increase in relative com- 
plexity and bulk of the nervous system, which accompanies com- 
plexity of structure in other respects in tlie ascending scale of ani- 
mals. Thus this force ditfers from all others, as remarked by Prof. 
Ilartshorne, in that its expenditure ultimately increases the amount 
of its production, because it constructs machinery which feeds its 
especial organs more and more successfully. Althougli expended 


by becoming energetic, its energy produces the means of its own 
increase. Unlike the physical forces whose expenditure renders 
matter ever more inert, growth-force when expended adds mate- 
rial which, as a profitable addition, increases the power of the cen- 
tral machine from which the force emanates, by furnishing an in- 
creased supply of food.* 

Thus it is evident that growth-force is not concentric nor polar 
in its activity, as are the i)hysical forces, and that its determina- 
tions are antagonistic to these. Its existence in the earth has 
been a succession of conquests over polar force, and, if preceding 
assumptions be true, the gradual progress presented by animals in 
abandoning the symmetrical forms exhibited by the lower types 
has doubtless been due to the constantly increasing amount of 


It is, however, evident that the directing power of conscious- 
ness is limited by the nature of the matter with which it has to 
deal. There are certain fundamental necessities to which it must 
conform. No one supposes that any degree of power can make 
twice two equal to six, cause two solid substances to occupy the 
same space at the same time, or make an absolutely solid sub- 
stance out of incomjDressible atoms of different forms. These in- 
volve the absurdity that something can be made out of nothing, 
or nothing out of something. From the present conduct of the 
inorganic world, it would appear to possess projjerties which ren- 
der consciousness impossible to it. This is doubtless due to the 
relations existing between the atoms or molecules of which its 
various species consist. The movements it displays are polar. 
The colloid molecular state is, so far as this planet is concerned, 
the only one which we know to be capable of consciousness, and 
then only while in a state of active transformation. As we have 
seen, when protoplasm is once organized and working automati- 
cally, consciousness need not be present ; and when this is absent, 
the rate of transformation, that is, the amount of food consumed, 
is greatly lessened. The excess of expenditure during conscious 

* It is incorrect to say that growth-force is "potential" in highly organized 
types, as it is undoubtedly expended in the movement of nutritive pabulum to a 
given locality. The maintenance of it in that locality is due to ordinary molecular 
cohesion, which can only be set free by greater molecular consolidation. 


activity over that necessary to unconscious activity is well known. 
It is thus evident that organization renders consciousness unne- 
cessary, GO long as external conditions are unchanged, and most 
probably a degree of fixity may be attained which renders con- 
sciousness impossible. The history of the evolution of animal 
types is apparently an illustration of this truth. The relations 
of the divisions of the animal kingdom are those of the limbs, 
branches, and trunk of a tree. Although the termini of the 
branches are successively nearer the root or starting-point as we 
proceed from the apex downward or backward, yet the connec- 
tion is not from end to end of these. To find this we pass down 
the limb to its junction with the trunk, and trace the branches 
from the axis outward. Thus with the branches of the animal 
kingdom. Although the divisions Vertebrata, Mollusca, Echino- 
dermata, etc., stand in an undoubted relation of succession to 
each other, there is no connection between the highest representa- 
tive of one and the lowest of another. It is the lower or less 
specialized forms of each which exhibit the relationship. Thus, 
among the articulates, the low group of the worms gives us con- 
nection with the Mollusca above by BracMopoda, and the echino- 
derms connect themselves with the Vermes by the less specialized 
Holothurida. It seems highly probable also that the point of con- 
tact of the Vertebrata with these is by one of the lowest divisions, 
formerly regarded as molluscan, viz.: the Ascidia. The same 
principle holds good within the great divisions. The most spe- 
cialized orders of Mammalia are the Artiodadyla, higher Perisso- 
dactijla, the Carnivora, Quadrumana, and perhaps Cetacea ; but 
the higher of these have not been derived from the lower. Mod- 
ern investigations show that several of them have been derived 
from a common type of mammals of the Eocene period, which is 
intimately connected with their lower forms, while wanting in 
the features which give them their special characters. These two 
illustrations serve to explain the universal law of zoological affin- 
ity, and therefore of evolution. 

The conclusion derived from a survey of this field is, that 
structure, like habit, when once established, is closely adhered to, 
and that the movement of growth-force once determined or or- 
ganized becomes automatic, i. e., independent of consciousness. 
Therefore a type which reproduces itself automatically becomes 
after a time so established as to be incapable of radical ciiange, in 
consequence of a molecular fixity which precludes it. Ncverthe- 


less susceptibility to influences of conscious stimuli may remain in 
some portions of the organism, and thus subordinate modifica- 
tions of structure have their origin. When conditions of life 
change, as they often have done during geologic time, those 
changes of structure which are possible take place under the 
stimulus of roused consciousness. But if the changes be radical, 
affecting the foundation processes of vital economy, the specialized 
forms must undoubtedly perish, and the life of the succeeding 
time be derived from forms of less pronounced character. The 
adaptability of generalized types, as to habits, and the absence of 
mechanical peculiarities in their structure, explain fully the cause 
of their standing in ancestral relation to all the typical faunse of 
the earth. 

Nowhere is this truth more remarkably-illustrated than in the 
case of man, the predominant mammal of the present period. 
From the generalized mammalian fauna of the Eocene, the Car- 
nivora develoj^ed a highly organized apparatus for the destruction 
of life and appropriation of living beings as food. The cloven- 
footed and odd-toed hoofed orders * are the result of constantly 
increasing growth of the mechanical appliances for rapid motion 
over the ground ; the former superadding exceptional powers of 
assimilation of innutritions food. The proboscidians developed 
huge bulk and an extraordinary prehensile organ. The Qiiadru- 
mana produced none of these things. In respect to speed of limb 
and jjowers of digestion, both in function and structure, they re- 
main nearly in the generalized condition from which the other 
orders of mammals have risen. The limbs and teeth of man re- 
tain the characters of the primitive type. Yet but two species of 
proboscidians remain ; the Perissodactyle multitudes are repre- 
sented by but a few vanishing species. The day of the Car- 
nivora has passed forever, and the remaining Artiodactyle herds 
exist but by the permission of their master, man. But past geo- 
logic time reveals no such abundance of true Quadrumana as the 
present period displays. These animals were evidently unable to 
compete with those of other types in seizing on the opportuni- 
ties of living. They were excluded from the chase by the more 
sanguinary ancestors of the Carnivora, and from the field by the 
multiplying herds of the swifter or more resistant hoofed animals. 
They possessed neither bulk, nor speed, nor cruelty to serve them 

* Represented by the ox and the horse. 


in the struggle for existence. So they were doubtless compelled 
to assume an arboreal life, which required little or no modifica- 
tion of the limbs for its maintenance, although the ultimate pro- 
duction of the grasping thumb from their primitive squirrel-like 
feet may be traced to this mode of life. The acquisition of a 
hand must be regarded as the first step in that marvelous acces- 
sion of experiences which is the condition of mental development. 
And this latter growth has taken the place of all other means of 
conquering a position in the world of life, so that man has even 
retrograded in the efficiency of bodily powers. He has lost the 
prehensile quality of the hind feet, and the special usefulness of 
his canine teeth. But the competition among men continues to 
be such as to render it in the highest degree improbable that he- 
will, as a species, lose the position gained, or suffer anyj^rolonged 
diminution of the power of intelligence. 

Now it is obvious that the more restricted the conditions of the 
life of a given animal type, the more sensitive it will be to changes. 
Hence it is that the risks to the existence of Carnivora, Artiodac- 
tyla, Prolosciclia, etc., are much greater than to the omnivorous, 
all-adaptive order of Quadrumana. The same is true of mind. 
The greater the proportion of unconscious automatism of habits, 
the less the power of adaptation ; and this must be the condition 
of all animals whose structure is so specialized as to place them 
beyond reach of competition, or to cut them off from a wide range 
of experiences. The greater the degree of consciousness of stim- 
ulus, the greater will be the degree of adaptability to new rela- 
tions, and to such constant rousing the unspecialized mind is 
always open. If, without strong natural weaj^ons, vigilance is the 
price of existence ; if not confined by organization to a j^eculiar 
kind of food, ceaseless investigation is stimulated. And these are 
the mental peculiarities which distinguish the monkeys among all 
the Mammalia. 

The reverse of this picture may now be described, as has been 
done by Prof. Vogt. It is well known that the young of many 
parasitic animals are free and active, and discover during migra- 
tion the localities to which they afterward attach themselves for 
life. During the early stages they present the characteristic marks 
of their order and class, and in some instances the males, remain- 
ing free, continue to do so. Such are the Entoconcha miraMlis, 
the Sacculmce and the Trematoda ; the first a mollusk, the second 
a cirrhijied crustacean, the third a worm. On their becoming at- 


taclied to their host a successive obliteration of their distinctive 
characters takes place, so that they become so simplified as to be 
no longer referable to their proper class, but susceptible, as Prof. 
Vogt remarks, of being united in a single division. A similar 
process is observed in the structural degeneration of the Lernean 
parasites, which are at first free, but afterward become parasitic 
on fishes. There is in this instance a coincidence between degen- 
eracy of structure and loss of compulsory activity : not only is 
every function of their sluggish lives automatically performed, but 
consciousness itself must experience little stimulus. 

From what has preceded, it is evident that automatism is at 
once the product and the antagonist of evolution, and that it is 
represented in structure by specialization. It appears also that 
consciousness is the condition of the inauguration of new habits, 
and this is only possible to structures which are not already too 
far specialized. This is doubtless true, whether osseous and mus- 
cular tissue be concerned in evolution, or whether it be nervous 
and brain tissue. Hence in the highest form of development, 
that of brain mechanism, automatism is the enemy, and con- 
sciousness the condition of progress. As a product of develop- 
ment, automatism is the condition of stationary existence, and 
constitutes its effective machinery, but every additional step re- 
quires the presence of consciousness. This may be expressed in 
the every-day language of human affairs, by saying that routine 
and progress are the opposite poles of social economy. 


This question has not yet been touched upon, nor is it neces- 
sary to give it prolonged attention at present. Consciousness is 
in itself inscrutable to us, and the contrast which it presents to 
physical and vital forces is the great fact of life. It is obvious 
enough that certain molecular conditions are essential to its ap- 
pearance; drugs intensify or obscure it ; concussions and lesions 
destroy it. It will doubtless become possible to exhibit a parallel 
scale of relations between stimuli on the one hand, and the de- 
grees of consciousness on the other. Yet for all this it will be 
impossible to express self-knowledge in terms of force. The ques- 
tion as to whether the product of the force conversion involved is 
the consciousness itself, or only a condition of consciousness, may 
receive light from the following consideration. 

Nowhere does '*the doctrine of the unspecialized" receive 


greater warrant than in the constitution of protoplasm. Modern 
chemistry refers compound substances to four classes, each of which 
is characterized by a special formula of combination. These are 
called the hydrochloric-acid type, the water-gas type, the ammonia 
type, and the marsh-gas type. These series are defined by the 
volumetric relations of their component simple substances : thus, in 
the first, a single volume unites with an equal volume of hydrogen ; 
in the second, two volumes of hydrogen unite with a single volume of 
another element ; in the third, three, and in the fourth, four vol- 
umes of hydrogen unite with the single A^olume of other elements. 
Hence the composition of these compounds is expressed by the fol- 
lowing formulas — chlorine, oxygen, nitrogen, and carbon being 
selected as typical of their respective classes : HCl, HjO, HsN, and 
H4C. Now it is an interesting fact that protoplasm is composed 
of definite proportions of four simple substances, each one repre- 
senting one of the classes above named, or, in other words, the ca- 
pacity for proportional molecular combination which characterizes 
them. The formula C24N8OH17 expresses the constitution of this 
remarkable substance. Now, although the significance of these 
combining numbers is unknown, there is a conceivable connection 
between the characteristic peculiarities of protoplasm and the na- 
ture of the substances which compose it. It is probable that these, 
when in combination with each other, exert a mutually antago- 
nistic control over each other's especial and powerful tendencies to 
form stable, and hence dead, compounds. It is therefore reason- 
able that the terms " unspecialized " or ''undecided" should be 
applicable to the molecular condition of protoplasm, and in so far 
it is a suitable nidus for higher molecular organization, and a ca- 
pacity for higher forms of force-conversion than any other known 
substance. If also in inorganic types, as in the organic, the gen- 
eralized have preceded the specialized in the order of evolution, we 
are directed to a primitive condition of matter which presented 
the essentially unspecialized condition of protoplasm, without 
some of its physical features. We are not necessarily bound to 
the hypothesis that protoplasm is the only substance capable of 
supporting consciousness, but to the opposite view, that the proba- 
bilities are in favor of other and unspecialized, at present un- 
known, forms of matter possessing this capacity. 

Consciousness constitutes then the only apparently initial point 
of motion with which we are acquainted. If so, we are at liberty 
to search for the origin of the physical forces in consciousness, as 


well as the vital ; their present unconscious condition being possi- 
bly due, as in the case of the vital, to automatism : the automa- 
tism being the expression of the atomic type of the substance ex- 
hibiting it. And, doubtless, the simple quantitative relations of 
the lowest types of forces are related to correspondingly simple 
geometrical conditions of matter, both representing the simplest 
grade of automatic action and machinery. We may also suppose 
that all of these primary conditions were necessary to the produc- 
tion of protoplasm, the only form of matter known to us in which 
consciousness can persist. 

In conclusion, it is obvious that the metastatic condition of 
protoplasm necessary to the persistence of consciousness could not 
be supported without a constant source of supply by assimilation. 
Hence it would ai3pear that the preliminary creation of dead and 
unconscious substances and organisms were a necessary antecedent 
to the accomplishment of this end : at least under circumstances 
of temperature under which living beings or protoplasm exist on 
this planet. Without the unconscious inorganic and organic prod- 
ucts of nature, consciousness could not exist on the earth for a 
day. No animal can maintain consciousness without food ; and 
that food must be, in the main, protoplasm. Protoplasm is manu- 
factured from inorganic matter by the (suijposed) unconscious 
protoplasm of the plant. What form of matter originally gave 
origin to protoplasm is yet unknown, but it is obvious that the 
ordinary physical forces must have existed as conditions of its 
creation, since now they are absolutely necessary to its persistence. 
Hence we may view the succession of automatic activities some- 
what in the light of the fagots used by the elephant to lift itself 
from the well into which it had fallen. One placed upon another 
finally raised the footing to an elevation which enabled the animal 
to obtain its freedom. 

Consciousness is the essential condition of personality ; so that 
in this view of the case we are led to a primitive personality, al- 
though not to what we call life. And the reason why this person- 
ality is to us so obscure a conception is probably to be found in 
the fact that it, as well as ourselves, is conditioned in its rela- 
tions to matter by necessary laws of ''mathematical" truth. 



The claims of the theory of Lamarck, that use modifies struct- 
ure in the animal kingdom, are being more carefully considered 
than heretofore, and are being admitted in quarters where they 
have been hitherto neglected or ignored. Eleven years ago I re- 
stated the question as follows : * 

"■ The influences and forces which have operated to produce 
the type-structures of the animal kingdom have been plainly of 
two kinds : 1. Originative; 2. Directive. The jorime importance 
of the former is obvious ; that the latter is only secondary in the 
order of time or succession, is evident from the fact that it con- 
trols the preservation or destruction of the results or creations of 
the first. 

"Wallace and Darwin have propounded as the cause of modi- 
fication in descent their law of natural selection. This law has 
been epitomized by Spencer as the 'survival of the fittest.' Tiiis 
neat expression no doubt covers the case, but it leaves the origin 
of the fittest entirely untouched. Darwin assumes a 'tendency 
to variation ' in nature, and it is plainly necessary to do this^ in 
order that materials for the exercise of a selection should exist. 
Darwin and Wallace's law is, then, only restrictive, directive, con- 
servative, or destructive of something already created. I propose 
then to seek for the originative laws by which these subjects are 
furnished — in other words, for the causes of the origin of the 

*' It has seemed to the author so clear from the first as to re- 
quire no demonstration, that natural selection includes no actively 
progressive principle whatever ; that it must first wait for the de- 

* "The Method of Creation," 1871, pp. 2 and 18, Walker Prize Essay, Proceeds, 
Amor. Ph:ios. Soc, pp. 2^0-246. 


velopment of variation, and then, after securing the survival of 
the best, wait again for the best to project its own variations for 
selection. In the question as to whether the latter are any better 
or worse than the characters of the parent, natural selection in no 
wise concerns itself." 

In seeking for the causes of the origin of variation, the follow- 
ing hypotliesis was proposed : 

" What are the influences locating growth-force ? The only 
efficient ones with which we are acquainted are, first, physical 
and chemical causes ; second, use ; and I would add a third, viz. : 
effort. I leave the first as not especially prominent in the econ- 
omy of type-growth among animals, and confine myself to the 
two following. The effects of use are well known. We can not 
use a muscle without increasing its bulk ; we can not long use 
the teeth in mastication without inducing a renewed deposit of 
dentine within the pulp-cavity to meet the encroachments of at- 
trition. The hands of a race of laborers are always larger than 
those of men of other pursuits. Pathology furnishes us with a 
host of hypertrophies, exostoses, etc., produced by excessive use, 
or necessity for increased means of performing excessive work. 
The tendency, then, induced by use in the parent, is to add 
segments or cells to the organ used. Use thus determines th^ 
locality of new repetitions of parts already existing, and deter- 
mines an increase of growth-force at the same time, by the in- 
crease of food always accompanying increase of work done, ia 
every animal. 

' ' But supposing there be no part or organ to use. Such must 
have been the condition of every animal prior to the appearance 
of an additional digit or limb or other useful element. It appears 
to me that the cause of the determination of growth-force is not 
merely the irritation of the part or organ used by contact with 
the objects of its use. This would seem to be the remote ca^^se 
of the deposit of dentine in the used tootli ; in the thickening 
epidermis of the hand of the laborer ; in the wandering of the 
lymph-cells to the scarified cornea of the frog in Cohnheim's ex- 
periment. You can not rub the sclerotica of the eye without 
producing an expansion of the capillary arteries and correspond- 
ing increase in the amount of nutritive fluid. But the case may 
be different in the muscles and other organs (as the pigment cells 
of reptiles and fishes) which are under the control of the volition 
of the animal. Here, and in many other instances which might 


be cited, it can not be asserted that the nutrition of use is not 
under the direct control of the jvill through the mediation of 
nerve-force. Therefore I am disposed to believe that growth- 
force may be, through the motive force of the animal, as readily 
determined to a locality where an executive organ does not exist, 
as to the first segment or cell of such an organ already com- 
menced, and that therefore efior.t is;^_in_the order of time, the 
first factor in acceleration." 

A difficulty in the way of this hypothesis is the frequently 
unyielding character of the structures of adult animals, and the 
difficulty of bringing sufficient pressure to bear on them without 
destroying life. But in fact the modifications must, in most in- 
stances, take place during the period of growth. It is well 
known that the mental characteristics of the father are trans- 
mitted through the spermatozooid, and that therefore the molec- 
ular movements which produce the mechanism of such mental 
characters must exist in the spermatozooid. But the material of 
the spermatozooid is combined with that of the ovum, and the 
embryo is composed of the united contents of both bodies. In a 
wonderful way the embryo develops into a being which resembles 
one or both parents in minute details. This result is evidently 
determined by the molecular and dynamic character of the origi- 
nal reproductive cells, which necessarily communicate their prop- 
erties to the embryo, which is produced by their subdivision. 
Rud. Hering has identified this property of the original cells with 
the faculty of memory. This is a brilliant thought, and, under 
restriction, probably correct. The sensations of j^ersons who have 
suffered amputation shows that their sensorium retains a picture 
or map of the body so far as regards the location of all its sensitive 
regions. This simulacrum is invaded by consciousness whenever 
the proper stimulus is applied,, and the locality of the stimulus is 
fixed by it. This picture probably resides in many .of the cells, 
both sensory and motor, and it doubtless does so in the few cells 
of simple and low forms of life. The spermatozooid is such a 
cell, and, how or why we know not, also contains such an ar- 
rangement of its contents, and contains and communicates such 
a type of force. It is probable that in the brain-cell this is the 
condition of memory of locality. If now an intense and long- 
continued pressure of stimulus produces an unconscious picture 
of some organ of the body in the mind, tliere is reason to suppose 
that the energies communicated to the embryo by the spermato- 


zooid and ovum will partake of tlie character of the memory thus 
created. The only reason why the oft-repeated stories of birth- 
marks are so often untrue is because the effect of temporary im- 
pressions on the mother is not strong enough to counterbalance 
the molecular structure established by impressions oftener re- 
peated throughout much longer periods of time. 

The demonstration of the truth or falsity of this position, so as 
to constitute it the true doctrine of evolution, could only be veri- 
fied from the prosecution of the science of paleontology. It is 
only in this field that the consecutive series of structures can be 
obtained which show the directions in which modification has 
taken place, and thus furnish evidence as to the causes of change. 
The most complete result of these investigations, up to the present 
time, has been the obtaining of sufficiently full series of the Mam- 
malia of the Tertiary period to show their lines of descent. In 
this way the series of modifications of their teeth and feet has 
been discovered, and the homologies of their parts been ascer- 
tained.* Perhaps the most important result of these investiga- 
tions is the following : The variations from which natural selec- 
tion has derived the persistent types of life have not been general 
or even very extensive. They have been in a limited number of 
directions, f and the most of these have been toward the increase 
in perfection of some machine. They bear the impress of the 
presence of an adequate originating cause, directed to a special 
end. Some of the lines struck out have been apparently inade- 
quate to cope with their environment, and have been discon- 
tinued. Others have been more successful, and have remained, 
and attained further modification. 

The reader can estimate the chance of the production of an 
especially adaptive mechanism in the absence of any pressure of 
force directing growth to that end. It appears to me that the 
probability of such variation appearing under such circumstances 
is very slight indeed, and its continuance through many geologic 
ages directed to the perfecting of one and the same machine still 
smaller. For this reason, attempts have been made to demon- 
strate a mechanical cause for the modifications of structure ob- 

* " Homologies and Origin of the Molar Teeth of the Mammalia educabilia." 
Journal Academy Nat. Sciences, Philadelphia, March, 1874. Proceedings Academy 
Nat. Sci., 1865, p. 22. 

f See Hyatt on this point, " Tertiary Planorbis of Steinheim." Annir. Mem. 
Bost. Soc. Nat. Hist., 1880, p. 20. 


served. For these I refer to papers by Messrs. Alpheus Hyatt, 
J. A. Ryder and myself : by Prof. Hyatt . . . "Upon the Effects 
of Gravity on the Forms of Shells and Animals ; " * Mi-. Eyder 
"On the Mechanical Genesis of Tooth Forms ;" f and "On the 
Laws of Digital Reduction ;" J by myself " On the Origin of the 
Specialized Teeth of the Carnivora ; " * " On the Origin of the 
Foot Structures of the Ungulates ;" || " On the Effect of Impacts 
and Strains on the Feet of Mammalia." ^ Now demonstration of 
the mechanical effects of the application of force to matter can 
only be obtained by observation of the process, and this can not 
be seen, of course, by the observation of fossils. The relation of 
the observed facts to the hypothesis is, however, shown by the 
above papers to be so precise that it only needs observation on the 
production of similar changes by similar causes in living types to 
give us a demonstration by induction, which will satisfy most 
minds. That such facts have been observed among the lower ani- 
mals is well known. The change of form of animals without 
hard parts, in adaptation to their environment, is an every-day 

That these views are now shared by many naturalists is be- 
coming every day more evident. Prof. E. Dubois-Raymond ^ has 
recently delivered a lecture before the physicians of the German 
army, on exercise or use, in which he makes some important 
admissions. We give the following extract : " We should be, 
therefore, free to admit, with some appearance of reason, that the 
vigor of the muscles of wings and of digging feet ; the thick 
epidermis of the palm of the hand and of the sole of the foot ; 
the callosities of the tail and of the ischia of some monkeys ; the 
processes of bones for the insertion of muscles ; are the conse- 
quences of nutritive and formative excitation, transmitted by 
heredity." In this position Prof. Raymond is in strict accord 
with the Lamarckian school of evolutionists. But Prof. Raymond 
still clings to the obscurities of the Darwinians, though Darwin 
himself is not responsible for them, in the following sentences : 
" It is necessary to admit, along with development by use, develop- 

* "Proceeds. Amer. Assoc. Adv. Science," 1880, p. 527. 

f " Proceedings Academy Philadelphia," 1878, p. 45 ; 1879, 47. 
:): Zoc. cit., 1877, October. 

* "American Naturalist," March, 1879, p. 171. 

I Loc. cit., April, 1881, p. 269. ^ Loc. cit., July, 1881, p. 542. 

<> " Revue Scientifique," Paris, Jan. 28, 1882. 


ment by natural selection, and that for three reasons. First, 
there are innumerable adaptations — I cite only those known as 
mimetic coloration — which appear to be only explicable by nat- 
ural selection and not by use. Second, plants which are, in their 
way, as well adapted to their environment as animals, are of 
course incapable of activity. Thirdly, we need the doctrine of 
natural selection to explain the origin of the capacity for exercise 
itself. Unless we admit that which it is impossible to do from a 
scientific stand-point, that designed structures have a mechanical 
origin, it is necessary to conclude that in the struggle for exist- 
ence the victory has been secured by those living beings who in 
exercising their natural functions have increased by chance {'par 
Jiasard ') their capacity for these functions more than others, and 
that the beings thus favored have transmitted their fortunate gifts 
to be still further developed by their descendants." 

To take up first the second and third of these propositions, 
Prof. Raymond does not for the moment remember that move- 
ment (or use) is an attribute of all life in its simplest forms, and 
that the sessile types of life, both vegetable and animal, must, in 
view of the facts, be regarded as a condition of degeneration. It 
is scarcely to be doubted that the primordial types of vegetation 
were all free swimmers, and that their habit of building cellulose 
and starch is responsible for their early-assumed stationary condi- 
tion. Their protoplasm is still in motion in the limited confines 
of their walls of cellulose. The movements of primitive plants 
have doubtless modified their structure to the extent of their dura- 
tion and scope, and probably laid slightly varied foundations, on 
which automatic nutrition has built widely diverse results. We 
may attribute the origin of the forms of the vegetable kingdom 
to three kinds of motion which have acted in conjunction with 
the physical environment ; first, their primordial free movements ; 
second, the intracellular movements of protoplasm ; third, the 
movements of insects, which have doubtless modified the structure 
of the floral organs. Of the forms thus produced, the fit have sur- 
vived and the unfit have been lost, and that is what natural selec- 
tion has had to do with it. 

The origin of mimetic coloration, like many other things, is yet 
unknown. An orthodox Darwinian attributes it to ''natural selec- 
tion," which turns out, on analysis, to be '' hasard." The survival 
of useful coloration is no doubt the result of natural selection. 
But this can not be confounded with the question of origin. On 


this point the Darwinian is on the same footing as the old-time 
Creationist. The latter says God made the variations, and the 
Darwinian says that they came by chance. Between these posi- 
tions science can perceive nothing to choose. 

I have attempted to explain the relation which non-adaptive 
structures bear to the theory of use and effort, in the following 
language : * 

" The complementary diminution of growth-nutrition follows 
the excess of the same in a new locality or organ, of necessity, if 
the whole amount of which an animal is capable be, as I believe 
[for the time being], fixed. In this way are explained the cases 
of retardation of character seen in most higher types. The dis- 
covery of truly complementary parts is a matter of nice observation 
and experiment. Perhaps the following cases may be correctly ex- 

" A complementary loss of growth-force may be seen in the ab- 
sence of superior incisor teeth and digits in ruminating Mammalia, 
where excessive force is evidently expended in the development of 
horns, and complication of stomach and digestive organs. The 
excess devoted to the latter region may account for the lack of 
teeth at its anterior orifice, the mouth ; otherwise, there appears 
to be no reason why the ruminating animals should not have the 
superior incisors as well developed as in the odd-toed (Perisso- 
dactyl) Ungulates, many of which graze and browse. The loss to 
the osseous system in the subtraction of digits may be made up in 
the development of horns and horn-cores, the horn sheath being 
perhaps the complement of the lost hoofs. It is not proposed to 
assert that similar parts or organs are necessarily and in all groups 
complementary to each other. The horse has the bones of the 
feet still further reduced than the ox, and is nevertheless without 
horns. The expenditure of the complementary growth-force may 
be sought elsewhere in this animal. The lateral digits of the 
EquidcB are successively retarded in their growth, their reduction 
being marked in Hippotlieriuin, the last of the three-toed horses ; 
it is accompanied by an almost coincident acceleration in the 
growth-nutrition of the middle toe, which thus appears to be com- 
plementary to them." 

* "Method of Creation," p. 23, 1871. 

^ Co- , Mew )/crz.(y^ 



If the law of modification of structure by use and effort be 
true, it is evident that consciousness or sensibihty must play an 
important part in evolution. This is because movements of ani- 
mals are plainly in part controlled by their conscious states. The 
question as to how many of the actions of animals are due to con- 
scious states at once arises. It is well known that most of the 
more strictly vital functions are unconsciously performed. Not 
only these, but many acts which have to be learned come to be 
performed in unconsciousness. Further, movements appropriate 
to needs which arise at the moment, and which are ordinarily 
termed voluntary, because they require the introduction of more 
or less of the rational faculty, are readily performed by verte- 
brated animals deprived of a brain, through the agency of the 
spinal cord alone.* The history of the origin of these movements 
must then be traced. 

The movements of living beings generally possess the pecul- 
iarity of design, in which they differ from the movements of non- 
living bodies. That is, their actions have some definite reference 
to their well-being or pleasure, or their preservation from injury 
or pain, and are varied with circumstances as they arise. This is 
not the case with non-living bodies, which move regardless of 
their integrity or of that of objects near them. This characteris- 
tic at once suggests that some element enters into them which is 
wanting to the movements of non-living masses. It has been 
suggested that the attraction of animals for their food and their 
repulsion from pain are derivatives from the attractions and repul- 
sions of inorganic bodies, supposed to be the exhibitions of the 
force called chemism. But this supposition does not explain the 
wide difference between the two classes of acts. The adaptation 
to the environment seen in organic acts is unknown to the inor- 
ganic world, while the invariable character of the motions of in- 
organic force is greatly modified in beings possessed of life. 
Whether consciously performed or not, the acts of organic beings 
resemble those of conscious beings actuated by instincts of hunger, 
reproduction, and defense. 

An explanation of these facts seems to be offered by a well- 

* Such expressions as " unconscious sensibility " and " unconscious will " are not 
used here, as being self -contradictory in terms and without meaning. 


known phenomenon. We know that it is true of ourselves and 
of many other animals, that while all new movements have to be 
learned by repeated attempts, with each succeeding movement 
the act becomes easier, and that finally it can be performed with- 
out requiring any attention whatever. If continued, the move- 
ment becomes automatic, so that it may be or is performed in a 
state of unconsciousness. In the words of Spencer, nervous cur- 
rents move most readily along accustomed channels. Thus the 
" habits " of animals may be looked on as movements acquired 
in consciousness, and become automatic through frequent repeti- 
tion. Not only this, but the organization thus produced in the 
parent is transmitted to the succeeding generation, so that the 
movements of the latter are automatically and often unconsciously 
performed. This view may be even extended to the purely vital 
functions, with every probability of its being the true explanation 
of their origin and development. On a former occasion * I wrote : 
*'In accordance with this view, the automatic * involuntary ' 
movements of the heart, intestines, reproductive systems, etc., 
were organized in successive states of consciousness, which con- 
ferred rhythmic movements whose results varied with the ma- 
chinery already existing and the material at hand for use. It is 
not inconceivable that circulation may have been established by 
the suffering produced by an overloaded stomach demanding dis- 
tribution of its contents. The structure of the Coelenterata offers 
the structural conditions of such a process. A want of propulsive 
power in a stomach or body sac occupied with its own functions, 
would lead to a painful clogging of the flow of its products, and 
the 'voluntary' contractility of the body or tube wall being thus 
stimulated, would at some point originate the pulsation necessary 
to relieve the tension, Thus might have originated the ' con- 
tractile vesicle ' of some protozoa, or contractile tube of some 
higher animals ; its ultimate product being the mammalian heart. 
So with reproduction. Perhaps an excess of assimilation in well- 
fed individuals of the first animals led to the discovery that self- 
division constituted a relief from the oppression of too great 
bulk. With the increasing specialization of form, this process 
would become necessarily localized in the body, and growth would 
repeat such resulting structure in descent as readily as any of 
the other structural peculiarities. No function bears the mark 

* " Consciousness in Evolution." " Penn Monthly," August, 1875, p. 565. 


of conscious origin more than this one, as consciousness is still 
one of the conditions of its performance. While less completely 
'voluntary ' than muscular action, it is more dependent on stim- 
ulus for its initial movements, and does not in these display the 
unconscious automatism characteristic of the muscular acts of 
many other functions." 

It was not proposed in the preceding paragraph that the con- 
tractility of living protoplasm should be regarded as due to con- 
sciousness, but that the location in a particular place of a contrac- 
tility already existing might be due to that cause. 

The preceding hypotheses bring us to a general theory of the 
evolution of organic structures or species. It is that they are the 
result of movements long continued and inherited, and that the 
character of these movements was originally determined by con- 
sciousness or sensibility. It remains then to consider the nature 
of consciousness. 

It may be mentioned that it is here left open whether there be 
any form of force which may be especially designated as "vital." 
Many of the animal functions are known to be physical and 
chemical, and if there be any one which appears to be less expli- 
cable by reference to these forces than the others, it is that of 
nutrition. Probably in this instance force has been so metamor- 
phosed, through the influence of the originative or conscious force 
in evolution, that it is a distinct species in the category of forces. 
Assuming it to be such, I have given it the name of Bathmism 
("Method of Creation," 1871, p. 26). Perhaps the contractility 
generally regarded as an attribute of living protoplasm may be a 
mechanical phenomenon dependent of course on nutrition ; or it 
may be the exhibition of a force peculiar to living beings ; and 
hence one of the ' vital ' group. 


The doctrine of evolution derives the organs of special sense 
from those of simple sensibihty or touch. In other words, their 
history has been that of other organs ; the complex have been 
derived from the general and simple. There are then generalized 
consciousness and specialized consciousness. A number of forms 
of consciousness multiplies its vividness, the one kind reenforcing 
the other by a slightly different appreciation of the same thing. 
In the case of persons deprived of the sense of touch, the sense 
of sight is not sufficient to convince them of their own existence. 


as a matter of intellectual reflection. When there is no nervous 
system we m^ust suppose sensibility to be generally distributed 
throughout the protoplasmic substance of the animal. The locali- 
zation of consciousness must depend on a localization of the kind 
and condition of protoplasm which sustains it ; while in other 
parts of the body the protoplasm is modified in other directions 
and for other purposes. If this be true, the nervous tissue of the 
higher animals should retain the characters of the lowest simple 
organisms. In point of fact this is the case, the nucleated cell 
being the essentially active element in the functions of brain and 
nerve, and being more numerous in that tissue than in any other. 

The remarkable evanescence of consciousness is one of its most 
marked characteristics. It is this peculiarity which has led 
many thinkers to deny its existence in the lower animals, and to 
induce others to believe that it can have had but little place among 
the causes of evolution. Partly for the same reason many biolo- 
gists attempt to derive it by metamorphosis from some form of 

But the nature of consciousness is such that it can not be de- 
rived from unconsciousness, any more than matter can be derived 
from no matter, or force from no force. The " unthinkable dogma 
of creation " (Haeckel) can not be applied to consciousness more 
than to matter or force. It is a thing by itself, and with matter 
and force forms a trio of primitive things which have to be 
accepted as ultimate facts. This is perfectly consistent with the 
position that consciousness is an attribute of matter, and neither 
more nor less difficult to comprehend than the fact that force is 
an attribute of matter. This view is maintained in a fashion of 
his own by G. H. Lewes. Prof. Eaymond* says in support of 
the same position : 

'^ More temperate heads betrayed the weakness of their dia- 
lectics in that they could not grasp the difference between the 
view which I opposed, that consciousness can be explained upon a 
mechanical basis, and the view which I did not question, but sup- 
ported with new arguments, that consciousness is bound to mate- 
rial ar>tccedcnts." This position has been maintained by various 
writers, among them Prof. Allman f and the writer. But Prof. 

* Address on the celebration of the Birthday of Leibnitz. " Pop. Science Month- 
ly," Feb., 18S2. 

f Address delivered before the British Association for the Advancement of 


Eaymond lias not found it to be acceptable to his nearest contem- 
poraries. He says : " The opposition which has been offered to 
my assertion of the incomprehensibility of consciousness on a me- 
chanical theory, shows how mistaken is the idea of the later phi- 
losophy, that that incomprehensibility is self-evident. It ap- 
pears, rather, that all philosophizing upon the mind must begin 
with the statement of this point." In stating this point some 
years ago we used the following language :* "It will doubtless 
become possible to exhibit a parallel scale of relations between 
stimuli on the one hand and the degrees of consciousness on the 
other. Yet for all this it will be impossible to express self-knowl- 
edge in terms of force." And again : f "An unprejudiced scru- 
tiny of the nature of consciousness, no matter how limited that 
scrutiny necessarily is, shows that it is qualitatively comparable 
to nothing else. . . . From this stand-point it is looked upon as 
a state of matter which is coeternal with it, but not coextensive." 

It is probable then that consciousness is a condition of matter 
in some peculiar state, and that wherever that condition of mat- 
ter exists consciousness will be found, and that the absence of that 
state implies the absence of consciousness. What is that state ? 

It would be a monstrous assumption to suppose that conscious- 
ness and life are confined to the planet on which we dwell. I 
presume that no one would be willing to maintain such an hypoth- 
esis. Yet it is obvious that if there be beings possessed of these 
attributes in the planets Mercury and Saturn, they can not be 
■ comjjosed of protoplasm, nor of any identical substance in the 
two. In the one planet protoplasm would be utterly disorganized 
and represented by its component gases ; in the other it would be 
a solid, suitable for the manufacture of sharp-edged tools. J But 
as it is probable that protoplasm is adapted for the phenomena of 
consciousness by a certain peculiarity of its constitution, it seems 
evident that other substances having a similar peculiarity may 
also be able to sustain it. I have elsewhere attempted to discover 
what this is, in the following language : ^ 

"Nowhere does 'the doctrine of the unspecialized ' receive 
greater warrant than in the constitution of protoplasm. Modern 
chemistry refers compound substances to four classes, each of 

* "Consciousness in Evolution." "Penn Monthly," July, 1875. 
f " The Origin of the Will." " Penn Monthly," 1811, p, 439, 
X Frazer in "American Naturalist," 1879, p. 420. 

* "Consciousness in Evolution," 1S75, p. 573. 


which is characterized by a special formula of combination. 
These are called the hydrochloric-acid type, the water-gas type, 
the ammonia type, and the marsh-gas type. These series are de- 
fined by the volumetric relations of their component simple sub- 
stances : thus in the first, a single volume unites with an equal 
volume of hydrogen ; in the second, two volumes of hydrogen 
unite with a single volume of another element ; in the third, three, 
and in the fourth, four volumes of hydrogen unite with the single 
volume of other elements. Hence the composition of these com- 
pounds is expressed by the following formulas — chlorine, oxygen, 
nitrogen, and carbon being selected as typical of their respective 
classes : HCl, HjO, H3N", and H4C. Now it is an interesting fact 
that protoplasm is composed of definite proportions of four simple 
substances, each one representing one of the classes above named, 
or, in other words, the capacity for proportional molecular com- 
bination which characterizes them. The formula C24N80H,t ex- 
j>resses the constitution of this remarkable substance. Now, al- 
though the significance of these combining numbers is unknown, 
there is a conceivable connection between the characteristic pecul- 
iarities of protoplasm and the nature of the substances which 
compose it. It is probable that these, when in combination with 
each other, exert a mutually antagonistic control over each other's 
especial and powerful tendencies to form stable, and hence dead, 
compounds. It is therefore reasonable that the terms ' unspecial- 
ized ' or ' undecided ' should be applicable to the molecular con- 
dition of protoplasm, and in so far it is a suitable nidus for higher 
molecular organization, and a capacity for higher forms of force- 
conversion than any other known substance. If also in inorganic 
types, as in the organic, the generalized have preceded the spe- 
cialized in the order of evolution, we are directed to a primitive 
condition of matter which presented the essentially unspecialized 
condition of protoplasm, without some of its physical features. 
We are not necessarily bound to the hypothesis that protoplasm is 
the only substance capable of supporting consciousness, but to the 
opposite view, that the probabilities are in favor of other and un- 
specialized, but unknown, forms of matter possessing this ca- 

The condition of living protoplasm was also referred to in the 
following language in a later publication : * 

* " The Origin of the Will." " Peim Monthly," June, 1877, p. 439. 


"The cause of V-ie difference between conscious and uncon- 
scious force must be secondarily due to different conditions of 
matter as to its atomic constitution ; consciousness being only 
possible, so far as we can ascertain, to matter which has not fallen 
into fixed and automatic relations of its atoms." 

Protoplasm in the form of food is not conscious ; and tissue 
formed of protoplasm is not conscious, excepting certain cells 
where the forming process is in action. Nor is consciousness 
present in all cells where nutrition is active. From the increased 
consumption of energy, and the increased exjoenditure of energy 
(heat, Lombard) which takes place during conscious processes, we 
may well believe that the decomposition of protojDlasm is more 
considerable in such processes than in other forms of nervous ac- 
tivity. We can imagine simple nutrition to be a condition of the 
elements of this substance in which the chemical force is simul- 
taneously combining and dissolving its combination, and that dur- 
ing the process there is a condition in which the chemism is for 
the time being unsatisfied, though present. The direction which 
this nutrition or metastasis takes, is due to the arrangement of the 
molecules already existing in the tissue, the new molecules taking 
the form of the old ones in replacement, so long as no extraneous 
force interferes. That they are rearranged under the influence of 
consciousness is apparent in the origin of variations of structure 
in accordance with the views of evolution already entertained. It 
is the arrangement of the molecules which constitutes the auto- 
matic machinery of nutrition as well as of other activities, so that 
consciousness necessarily only appears in that stage of nutrition 
while the matter is in a transition state, and unformed. Whether 
chemism must be regarded as suspended, or only unsatisfied, at 
this stage, can only be imagined. As non-satisfaction is probably 
the temj)orary condition in all nutrition, it is not unlikely that sus- 
pension may be the condition of consciousness. 

Perhaps the character of the components of protoplasm is such 
that the movements of their atoms, i. e., their chemism, mutually 
interfere and destroy each other, as in the cases of the interference 
of the waves of light and sound. 

The colloid form of protoplasm is especially favorable to inter- 
nal movements which shall not destroy the integrity of the mass, 
perhaps more so than a gaseous state in a compound of similar con- 
stitution. It is, moreover, more favorable to the preservation of 
molarity than a gas could be, on account of the ease with which 


it adheres to solid substances, and transports and locates them as 
part of its external and internal supports. But it is not incon- 
ceivable that under other conditions of temperature, etc., the 
gaseous condition of matter might answer the same purpose. It 
must be borne in mind, however, that this is a subordinate ques- 
tion, and that the real characteristic of the "phj^sical basis of life " 
is to be found rather in its generalized dynamic condition. 

We must then believe that wherever this generalized condition 
' exists, consciousness will be present. As soon as mechanical or 
chemical force appears in the molecules of the sustaining sub- 
stance, consciousness disappears. The organism has taken the first 
step toward death, but is not dead, but is ancBsthetized. Constant 
nutrition is essential to the performance of all life functions, in- 
cluding consciousness, and it is evident that this is necessary to 
the maintenance of the unspecialized condition in which the latter 

Is the appearance of sensibility on the development of its sus- 
taining condition, evidence that the latter stands to the former in 
the relation of cause and effect ? If the view of the pre-existence 
of consciousness be true, there is no more relation of cause and 
effect than in the case of the opening of a door which admits a 
wind. The force expended in opening the door is not converted 
into the energy exerted by the wind as it enters the room. It 
simply releases it, or admits it to a new field. It is, however, true, 
that consciousness having once entered, a larger conversion of force 
is necessary to its persistence than is expended during its absence. 
Like combustion, which is only communicable under suitable con- 
ditions, consciousness having once been transmitted to a new cestlie- 
topliore* lives on it, and requires constant supplies of material for 
its sustenance. 

The hypothesis of the primitive and creative function of con- 
sciousness may be called ArclicBsthetism. 


It has been the custom of men from the dawn of thought to 
attempt to construct for themselves cosmogonies and theologies. 
Science is yet far from supplying the facts necessary to the con- 
struction of a true system of the universe, and philosophy can only 
stretch out a little further into the unknown by the use of neces- 

* ^sthetophore, a substance which sustains consciousness. 


sary inference. In spite, however, of the insufficiency of the data, 
men still suggest new views or cling to old ones, and an occasional 
flight into this region of thought at least brings the thinker into 
sympathy with the thoughts of his fellow-men. 

The admission of the possibility of the existence of conscious- 
ness in other forms of matter than protoplasm, and in other regions 
than the Earth, lends countenance to a rational belief in the so- 
called '^supernatural" (better called the supersensuous) so preva- 
lent among men in irrational forms. The question naturally 
arises. Is there any generalized form of matter distributed through 
the universe which could sustain consciousness ? The presump- 
tion is that such a form of matter may well exist. Evolution or 
specialization has only worked up part of its raw material in the or- 
ganic world. Wherever primitive conditions remain, there primi- 
tive organisms abound. Protozoa are yet numerous on land, and 
the Protohathyhius inhabits the depths of the sea. Highly spe- 
cialized forms of life are in fact numerically a minority of living 
beings. May not this be true also of inorganic beiugs ? It is 
thought that various celestial bodies represent unfinished worlds. 
Is it not probable that the grand sources of matter not yet spe- 
cialized into the sixty odd substances known to us, may still sus- 
tain the primitive force not yet modified into its species, and that 
this combination of states may be the condition of persistent con- 
sciousness from which all lesser lights derive their brilliancy ? 
There is much to warrant such a view in the observed facts of life, 
taken in connection with the general course of evolution. More- 
over, that some form of matter connects the interstellar spaces, is 
thought to be proved by the transmission of light in some cases, 
and light and heat in others. That such a form of matter per- 
vades all spaces whatever, is the theory of some physicists. If it 
be so generalized as to be capable of sustaining consciousness, it 
becomes the source from which other substances derive it, so soon 
as they, through the energy of nutrition, which resists death, 
maintain the same primitive and unformed constitution capable 
of exhibiting it. 

Of course there is no evidence in our own memory of the ex- 
istence of our personality prior to our human experience. No 
one on awaking from unconsciousness remembers having been 
anywhere in particular during the interval. These facts may be 
harmonized with the theory here presented, on the supposition 
that memory is lost on a transfer of consciousness from one physi- 


cal basis to another. The arguments in favor of a transfer of 
consciousness do not sustain the idea of a transfer of memory. 
Memory requires an arrangement of molecules or atoms which 
when finished no longer exhibits consciousness. With proper 
stimulus, when the proper kind of force conversion is set up in 
them, consciousness extends into them, and, taking their form, 
produces reminiscence or conscious memory. The molecular 
arrangement would be probably lost on a transfer of conscious- 
ness to a new material basis. It might then be supposed that with 
every such transfer a new personality is established. Though 
the correct definition of personality includes memory as well as 
consciousness, when viewed as an objective concept, it may be 
questioned whether memory is necessary to the subjective belief 
in one's own personality. Those insane persons who believe that 
they have lost their personality, and think that they are some one 
else, nevertheless recognize the fact that what they now are has 
a continuity of existence with what they once were. The mate- 
rial limitations of consciousness are the authors of the kind of 
personality it presents. A limitation or an expansion of its range 
w^ould not destroy the idea of personality, but would simply re- 
strict or extend it. The possible confluence of many personalities 
would not destroy them, but each one would regard the others 
as additions to himself, and himself, therefore, as so much the 
greater being. 

As a summary of the preceding conclusions, the following 
analysis of metaphysical systems may be given. It defines the 
place of the doctrine of archsesthetism, above proposed, as dis- 
tinguished from the opposing view of mctassthetism, which is 
held by many monists : 

I. Consciousness (" spirit ") is independent of matter Dualism. 

II. Consciousness is an attribute of matter Monism. 

a. Consciousness is primitive and a cause of evolution ^ ArchcEsthetism. 

/3. Consciousness is a product of the evolution of matter and force. 





The general proposition that life has preceded organization in 
the order of time, may be regarded as establislied. It follows ne- 
cessarily from the fact which has been derived from paleontological 
investigation, that the simple forms have, with few sporadic ex- 
ceptions, preceded the complex in the order of appearance on the 
earth. The history of the lowest and simplest animals will never 
be known, on account of their perishability ; but it is a safe infer- 
ence from what is known, that the earliest forms of life were the 
rhizopods, whose organization is not even cellular, and includes 
no organs whatever. Yet these creatures are alive, and authors 
familiar with them agree that they display, among their vital 
qualities, evidences of some degree of sensibility. 

The following ^propositions were laid down by Lamarck, as 
established by facts known to him, in 1809 : f 

I. "In every animal which has not passed the term of its de- 
velopment, the frequent and sustained employment of an organ, 
gradually strengthening it, develops and enlarges it, and gives- it 
power proportional to the duration of its use ; whilst the constant 
disuse of a like organ insensibly weakens it, deteriorates it, pro- 
gressively reduces its functions, and finally causes it to disappear. 

II. " All that nature acquires or loses in individuals, through 
the influence of circumstances to which the race has been exposed 
for a long time, either by the predominant use of an organ or by 
the disuse of such part, she preserves by generation among new 

* An address delivered before the Biological Section of the American Associa- 
tion for the Advancement of Science, at Philadelphia, September 4, 1884, by E. D. 
Cope, vice-president. 

t "Philosophie Zoologique," Pt. I, p. 235 (Edit. 1830). 


individuals which spring from it, provided the acquired changes 
be common to both sexes or to those which produce new indi- 
yiduals. " 

The same projoosition was previously enunciated by Lamarck 
in the following condensed form ("^Recherches sur les Corps 
Vivans," p. 50) : 

" It is not the organ, that is, the nature and form of the parts 
of the body, which have given origin to its habits and peculiar 
functions, but it is, on the contrary, its habits, its manner of life, 
and the circumstances in which individuals from which it came 
found themselves, which have, after a time, constituted the form 
of the body, the number and character of its organs, and the func- 
tions which it possesses." 

Several years ago, not having read Lamarck, I characterized 
the above hypothesis as the " law ot use and effort," * and I have 
subsequently formulated the modus operandi of this law into two 
propositions. The first of these is, that animal structures have 
been produced, directly or indirectly, by animal movements, or 
the doctrine of hinetoge^iesis ; the second is, that as animal move- 
ments are primitively determined by sensibility, or consciousness, 
consciousness has been and is one of the primary factors in the 
evolution of animal forms. This is the doctrine of arcluBsflipi- 
ism. The doctrine of kinetogenesis is implied in the speculations 
of Lamarck in the following language ('' Philosophic Zoologique," 
ed. 1830, p. 239): ''With regard to the circumstances which 
[Nature] uses every day to vary that Avhich she produces, one can 
say that they are inexhaustible. The principal arise from the 
influence of climates ; from diverse temperature of the atmos- 
phere and of the environment generally ; from diversity of loca- 
tion ;