SCIENCE. 
1 7 
ment of Amphioxus and of the Tunicata prove beyond a 
doubt that the differences which were supposed to consti- 
tute a barrier between the two are non-existent. There is 
no longer any difficulty in understanding how the verte- 
brate type may have arisen from the invertebrate, though 
the full proof of the manner in which the transition was ac- 
tually effected may still be lacking. 
Again, in 1859, there appeared to be a no less sharp 
separation between the two great groups of flowering and 
flowerless plants. It is only subsequently that the series 
of remarkable investigations inaugurated by Holmeister 
has brought to light the extraordinary and altogether unex- 
pected modifications of the reproductive apparatus in the 
Lycopodiacece, the Rhizocarpece, and the Gymnospermea , by 
which the ferns and the mosses are gradually connected 
with the Phanerogamic division of the vegetable world. 
So, again, it is only since 1859 that we have acquired 
that wealth of knowledge of the lowest forms of life which 
demonstrates the futility of any attempt to separate the 
lowest plants from the lowest animals, and shows that the 
two kingdoms of living nature have a common borderland 
which belongs to both or to neither. 
Thus it will be observed that the whole tendency of bio- 
logical investigation since 1859 has been in the direction of 
removing the difficulties which the apparent breaks 
in the series created at that time ; and the recognition 
of gradation is the first step towards the acceptance of 
evolution. 
As another great factor in bringing about the change of 
opinion which has taken place among naturalists, I count 
the astonishing progress which has been made in the study 
of embryology. Twenty years ago, not only were we de- 
void of any accurate knowledge of the mode of development 
of many groups of animals and plants, but the methods of 
investigation were rude and imperfect. At the present 
time there is no important group of organic beings the de- 
velopment of which has not been carefully studied, and the 
modern methods of hardening and section-making 
enable the embryologist to determine the nature of 
the process in each case, with a degree of minuteness 
and accuracy which is truly astonishing to those 
whose memories carry them back to the beginnings 
of modern histology. And the results of these embryo- 
logical investigations are in complete harmony with the 
requirements of the doctrine of evolution. The first begin- 
nings of all the higher forms of animal life are similar, and 
however diverse their adult conditions, they start from a 
common foundation. Moreover the process of develop- 
ment of the animal or the piant from its primary egg or 
germ is a true process of evolution — -a process from almost 
formless to more or less highly organized matter, in virtue 
of the properties inherent in that matter. 
To those who are familiar with the process of develop- 
ment all a priori objections to the doctrine of biological 
evolution appear childish. Any one who has watched the 
gradual formation of a complicated animal from the pro- 
toplasmic mass which constitutes the essential element of 
a frog’s or a hen’s egg has had under his eyes sufficient 
evidence that a similar evolution of the animal world from 
the like foundation is, at any rate, possible. 
Yet another product of investigation has largely con- 
tributed to the removal of the objections to the doctrine of 
Evolution current in 1859. If is the proof afforded by 
successive discoveries that Mr. Darwin did not overestimate 
the imperfection of the geological record. No more strik- 
ing illustration of this is needed than a comparison of our 
knowledge of the mammalian fauna of the Tertiary epoch 
in 1859 with its present condition. M. Gaudry’s researches 
on the fossils of Pikermi were published in 1868, those of 
Messrs. Leidy, Marsh, and Cope on the fossils of the 
Western Territories of America, have appeared almost 
tvholly since 1870 ; those of M. Filhol, on the phosphorites 
of Quercy, in 1878. The general effect of these investiga- 
tions has been to introduce us to a multitude of extinct 
animals, the existence of which was previously hardly 
suspected ; just as if zoologists were to become aquainted 
with a country, hitherto unknown, as rich in novel forms of 
life, as Brazil or South Africa once were to Europeans. 
Indeed the fossil fauna of the Western Territories of 
America bids fair to exceed in 'merest and importance 
all other known Tertiary deposits put together; and yet, 
with the exception of the case of the AmericanTertiaries, 
these investigations have extended over very limited areas, 
and at Pikermi were confined to an extremely small space. 
Such appear to me to be the chief events in the history 
of the progress of knowledge, during the last twenty years, 
which account for the changed feeling with which the 
doctrine of Evolution is at present regarded by those who 
have followed the advance of biological science in respect 
of those problems which bear indirectly upon that doctrine. 
But all this remains mere secondary evidence. It may 
remove dissent, but it does not compel assent. Primary 
and direct evidence in favor of Evolution can be furnished 
only by pal aeon tology. The geological record, so soon as 
it approaches completeness, must, when properly ques- 
tioned, yield either an affirmative or negative answer; 
if evolution has taken place, there will its mark be left; if 
it has not taken place, there will lie its refutation. 
What was the state of matters in 1859? Let us hear 
Mr. Darwin, who may be trusted always to state the case 
against himself as strongly as possible. 
“ On this doctrine of the extermination of an infinitude 
of connecting links between the living and extinct inhabi- 
tants of the world, and at each successive period between 
the extinct and still older species, why is not every geo- 
logical formation charged with such links? Why does 
not every collection of fossil remains afford plain evidence 
of the gradation and mutation of the forms of life? We 
meet with no such evidence, and this is the most obvious 
and plausible of the many objections which may be urged 
against my theory.” 1 
Nothing could have been more useful to the opposition 
than this characteristically candid avowal, twisted as it 
immediately was into an admission that the writer’s views 
were contradicted by the facts of palaeontogy. But, 
in fact, Mr. Darwin made no such admission. What he 
says in effect is, not that palaeontological evidence is against 
him, but that it is not distinctly in his favor ; and without 
attempting to attenuate the fact, he accounts for it by the 
scantiness and the imperfection of that evidence. 
What is the state of the case now, when, as we have 
seen, the amount of our knowledge respecting the mam- 
malia of the Tertiary epoch is increased fifty-fold, and in 
some directions even approaches completeness? 
Simply this, that if the doctrine of Evolution has not 
existed paleontologists must have invented it, so irresist- 
ibly is it forced upon the mind by the study of the remains 
of the Tertiary mammalia which have been brought to 
light since 1859. 
Among the fossils of Pikermi, Gaudry found the suc- 
cessive stages by which the ancient civets passed into the 
more modern hyaenas ; through the Tertiary deposits of 
Western America, Marsh tracked the successive forms by 
which the ancient stock of the horse has passed into its 
present form ; and innumerable less complete indications 
of the mode of evolution of other groups of the higher 
mammalia have been obtained. 
In the remarkable memoir on the Phosphorites of 
Quercy, to which I have referred, M. Filhol describes no 
lewer than seventeen varieties of the genus Cynodictis, 
which fill up all the interval between the viverine animals 
and the bear-like dog Amphicyon ; nor do I know any 
solid ground of objection to the supposition that in this 
Cynodictis-Amphicyon group we have the stock whence 
all the Viveridae, Felidm, Hyaenidse, Canidae, and perhaps 
the Procyonidae and Ursidae, of the present fauna have 
been evolved. On the contrary, there is a great deal to be 
said in its favor. 
In the course of summing up his results, M. Fiihol 
observes 8 : — 
“ During the epoch of the phosphorites, great changes 
took place in animal forms, and almost the same types as 
those which now exist became defined from one another. 
Under the influence of natural conditions of which we 
have no exact knowledge, though traces of them are 
discoverable, species have been modified in a thousand 
ways ; races have arisen which, becoming fixed, have 
( Concluded on page 20.) 
1 “Origin of Species, ed. 1. p. 463. 
3 This passage was omitted in the delivery of the lecture. 
