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CHAPTER XXXV. 



EVOLUTION OF THE HORSE.* 



General Remarks — Hyracotherium — Protorohippus — Orohippus — Epihippus — 

 Mesohippus bairdii — Mesohippus intermedius — Miohippus — Protohippus — 

 Pliohippus — Pleistocene Equida; — Prehistoric horses — Causes of structural 

 changes — Horses of the future. 



General Remarks. — In considering the question of 

 the evohition of the horse, we must bear in mind that 

 evolution is adaptation to external conditions, in which 

 cHmate and soil (Chapter XXVI.) play a large part ; 

 and that we have no proof of the existence of latent 

 possibilities in an organism. 



Instead of beginning the history of the horse at the 

 earliest appearance of animal life on the earth, I shall 

 attempt to trace it only through the Ungulata (mammals 

 which have hoofs or blunt broad nails). Although we 

 cannot hope to determine the exact sequence of the foot- 

 steps of the ungulates which, in their march of evolution, 

 became gradually changed into horses ; we shall find on 

 their track, marks left by them or by near relatives who 

 accompanied them on their journey, which will guide 

 us in the right direction. As science progresses, the 

 intervals between these landmarks will become gradually 

 filled in ; although it seems impossible that the position 

 of every footprint can ever be accurately defined. 



We learn from the study of palaeontology, that living 



* Whatever merit this chapter may possess is entirely due to the valuable and generous 

 help I received from Professor Cossar Ewart, F. R.S. 



