In its general characters, the skeleton of _Anchitherium_ is very similar to that of the horse. In fact, Lartet and De Blainville called it _Palæotherium equinum_ or _hippoides;_ and De Christol, in 1847, said that it differed from _Hipparion_ in little more than the characters of its teeth, and gave it the name of _Hipparitherium._ Each foot possesses three complete toes; while the lateral toes are much larger in proportion to the middle toe than in _Hipparion,_ and doubtless rested on the ground in ordinary locomotion. The ulna is complete and quite distinct from the radius, though firmly united with the latter. The fibula seems also to have been complete. Its lower end, though intimately united with that of the tibia, is clearly marked off from the latter bone. There are forty-four teeth. The incisors have no strong pit. The canines seem to have been well developed in both sexes. The first of the seven grinders, which, as I have said, is frequently absent, and, when it does exist, is small in the horse, is a good-sized and permanent tooth, while the grinder which follows it is but little larger than the hinder ones. The crowns of the grinders are short, and though the fundamental pattern of the horse-tooth is discernible, the front and back ridges are less curved, the accessory pillars are wanting, and the valleys, much shallower, are not filled up with cement. Seven years ago, when I happened to be looking critically into the bearing of palaentological facts upon the doctrine of evolution, it appeared to me that the _Anchitherium,_ the _Hipparion,_ and the modern horses, constitute a series in which the modifications of structure coincide with the order of chronological occurrence, in the manner in which they must coincide, if the modern horses really are the result of the gradual metamorphosis, in the course of the Tertiary epoch, of a less specialised ancestral form. And I found by correspondence with the late eminent French anatomist and palaeontologist, M. Lartet, that he had arrived at the same conclusion from the same data. That the _Anchitherium_ type had become metamorphosed into the _Hipparion_ type, and the latter into the _Equine_ type, in the course of that period of time which is represented by the latter half of the Tertiary deposits, seemed to me to be the only explanation of the facts for which there was even a shadow of probability. [3] And, hence, I have ever since held that these facts afford evidence of the occurrence of evolution, which, in the sense already defined, may be termed demonstrative.