in fact, have the radius and ulna, the tibia and fibula, distinct and
separate. They have five distinct and complete digits on each foot, and
no one of these digits is very much larger than the rest. Moreover, in
the least modified mammals, the total number of the teeth is very
generally forty-four, while in horses, the usual number is forty, and in
the absence of the canines, it may be reduced to thirty-six; the incisor
teeth are devoid of the fold seen in those of the horse: the grinders
regularly diminish in size from the middle of the series to its front
end; while their crowns are short, early attain their full length, and
exhibit simple ridges or tubercles, in place of the complex foldings of
the horse's grinders.

Hence the general principles of the hypothesis of evolution lead to the
conclusion that the horse must have been derived from some quadruped
which possessed five complete digits on each foot; which had the bones
of the fore-arm and of the leg complete and separate; and which
possessed forty-four teeth, among which the crowns of the incisors and
grinders had a simple structure; while the latter gradually increased in
size from before backwards, at any rate in the anterior part of the
series, and had short crowns.

And if the horse has been thus evolved, and the remains of the different
stages of its evolution have been preserved, they ought to present us
with a series of forms in which the number of the digits becomes
reduced; the bones of the fore-arm and leg gradually take on the equine
condition; and the form and arrangement of the teeth successively
approximate to those which obtain in existing horses.

Let us turn to the facts, and see how far they fulfil these requirements
of the doctrine of evolution.