202 MAMMALIAN DESCENT. [Lect. VIII. 



Professor Huxlei/ on the Evolution of the Horse type. 



" Since the commencement of the Eocene 



epoch, the animals which constitute the family of the 

 Equidse have undergone processes of modification of 

 three kinds — 



"1. There has been an excess of development of some 

 parts in relation to others. 



" 2. Certain parts have undergone complete or partial 

 suppression. 



" 3. Certain parts, which were originally distinct, lia^'e 

 coalesced. 



" Employing the term ' law ' simply in the sense of a 

 general statement of facts ascertained by observation, I 

 shall speak of these three processes by which the 

 Eohi'ppus form has passed into Equiis as the expression of 

 a threefold law of evolution " — " On the Arrange- 

 ment of the Mammalia," Proc. Zool. Soc, 1880, p. G49. 



