ii6 MODERN IDEAS OF EVOLUTION 



changes ? We do not know any equine animal before 

 the Eocene. Is it not possible that they may have 

 originated in some way different from that slow 

 change by which they are supposed to have been 

 transmuted into horses, and that in their first origin 

 they were more plastic than after many changes had 

 happened to them ? May it not be that the origin of 

 forms or types is after all something different from 

 derivative changes, and that new forms are at first plas 

 tic, afterwards comparatively fixed at first fertile in 

 derivative species, and afterward comparatively barren? 

 Certainly, unless something of this kind is the case, we 

 fail to find in the modern world a sufficient number 

 of representatives of the Palczotheria, Anoplotheria, 

 LopJiiodons, Coryplwdon, elephants, and mastodons 

 of the Tertiary. On the other hand, it is scarcely 

 possible to find a sufficient starting point in the 

 Eocene for the multitude of cetaceans, carnivores, 

 ruminants, and quadrumana of the modern time. 



The conclusion of this special discussion of the 

 case of the horse must, I think, be the same as that 

 arising from our general summary of palaeontological 

 facts, namely, that on the one hand we may not 

 be justified in affirming that every race of fossil 

 animals or plants which we may name as a species is 

 really a distinct product of creation, and that on the 

 other hand the introduction and extinction of species, 

 and even of races and varieties, depends on the inter 

 action of causes too numerous and complicated to be 



