30 DARWINISM VERIFIED. [i. 



Marsh have set before us a much more perfect series. 

 Going back in time, as we reach the upper Pliocene, 

 the horse disappears, and we find the pliohippus, very 

 much like him. In the lower Pliocene this creature 

 is replaced by the protohippus, with three toes like 

 the hipparion. In the upper Miocene we have the 

 miohippus, with three well-developed toes like the 

 anchitherium, and with the rudiment of a fore-toe on 

 the fore-foot. In the mesohippus of the lower Mio- 

 cene this rudiment is a splint-bone, like those which 

 represent the later-disappearing toes in the modern 

 horse. By this time we find the ulna and fibula well 

 developed and distinct from the radius and tibia. 

 Still further back, in the upper Eocene, comes the 

 orohippus, with four complete toes on the fore-foot. 

 And finally, in the lower Eocene, we get the eohippus, 

 which shows the rudiment of a fifth toe on the front 

 and a fourth toe on the hind foot. In the structure 

 of the teeth the other chief point in which the 

 modern horse is notably specialised we find a 

 similar gradation back to the ordinary mammalian 

 type. 



The agreement of observed facts with the require- 

 ments of theory is here complete, minute, and 

 specific ; and Professor Huxley may well say that 

 the history of the descent of the horse from a five- 



