184 
general plan, but with significant differences. The bear has 
two bones in the arm of each front leg, the radius and the ulna, 
and in each hind leg two distinct bones, the tibia and fibula ; 
whilst tbe horse has these two bones coalesced in both front 
and hind legs. But the principal difference lies in the number 
of their toes. The bear has five toes on each foot ; the horse 
has but one, with two small splint bones, which arc named 
rudimental toes. The beards middle toe answers to the 
horse^s one toe or hoof. On the theory of development by 
natural selection and survival of the fittest, the two mammals 
in question are held to have descended from a common ancestry. 
The horse, being the differentiated animal, has to be traced back 
to an ancestor with the two bones in each leg and the possessor 
of five toes. 
42. Professor Huxley has found, in an older stratum than the 
present, the hipparion with the two bones in each front leg, and 
with three toes (although only one reaches the ground) ; and 
in a still older stratum the anchitherium, with three toes, all 
of which reach the ground, all serviceable toes ; and, still 
lower down, orohippus, with four toes on the front feet, and 
three on the hind feet. Upon this evidence Professor Huxley 
said that he thought the chain of ascertained facts verified 
so far the doctrine of evolution, and justified him in saying ^ ho 
would not in future take the trouble to discuss that doctrine 
on d ^priori grounds."* 
43. In the judgment of Professor Huxley the evidence is 
demonstrative. He has said so, and entitles the third lecture 
of the American Addresses The Demonstrative Evidence 
of Evolution ” ; and to the audience in Chickering Hall, New 
York, he said that evolution was as thoroughly proved as the 
Copernican theory. 
44. If the doctrine of evolution is true, then the interesting 
facts brought under our notice by Professor Huxley are cer- 
tainly in harmony with that doctrine ; but it does not, there- 
fore, follow that these facts in themselves prove the truth of 
the doctrine. 
45. We are necessarily without a particle of collateral evidence 
that these divers-toed mammals descended from each other in 
the line indicated. This has to be assumed on the ground of 
their resembling construction and their following each other 
in order of strata, — Eocene, Miocene, Pliocene, Pleistocene. 
46. But with a certain resemblance in construction there were 
also very marked differences. They differed from each other, 
not in the number of their toes only ; hipparion differed from 
the present horse both in limbs and teeth; and anchitherium 
differed from hipparion as much as h ipparion differed from the 
