Ill 



LECTURES ON EVOLUTION 123 



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 evolu- 

 tion. 



In Europe abundant remains of horses are 

 found in the Quaternary and later Tertiary strata 

 as far as the Pliocene formation. But these 

 horses, which are so common in the cave-deposits 

 and in the gravels of Europe, are in all essential 

 respects like existing horses. And that is true of 

 all the horses of the latter part of the Pliocene 

 epoch. But, in deposits which belong to the 

 earlier Pliocene and later Miocene epochs, and 

 which occur in Britain, in France, in Germany, in 

 Greece, in India, we find animals which are 

 extremely like horses which, in fact, are so 

 similar to horses, that you may follow descriptions 

 given in works upon the anatomy of the horse 

 upon the skeletons of these animals but which 

 differ in some important particulars. For example, 

 the structure of their fore and hind limbs is 

 somewhat different. The bones which, in the 

 horse, are represented by two splints, imperfect 

 below, are as long as the middle metacarpal and 

 metatarsal bones ; and, attached to the extremity 

 of each, is a digit with three joints of the same 

 general character as those of the middle digit, 

 only very much smaller. These small digits are 

 so disposed that they could have had but very 



