in DOMESTICABLE MAMMALIA 153 



the machinery of ordinary generation, 

 but under a definite guidance along 

 certain lines to an extraordinary but 

 determinate result, is all the more strik- 

 ing because it does not stand alone. All 

 the great domesticable Mammalia which 

 serve such important purposes in the life 

 of Man, and without which that life 

 would have been far less favourably con- 

 ditioned than it is, were all the contem- 

 poraneous product of that very recent, 

 but most pregnant, Pliocene age in which 

 the Horse was, at some appointed time, 

 evolved out of ancestral forms, which 

 would have been as useless to Man as 

 the survivors of them now are, such as 

 the Rhinoceros or the Tapir. 



Among the conceptions to which the 

 Darwinian theory of development has 

 most frequently resorted, has been the 

 conception that the development of all 

 individual things from germs is an 



