38 Darwinism and Other Essays. 



ence. But this is, after all, a misconception of 

 the requirements of the argument ; for on the 

 one hand the Darwinian theory nowhere requires 

 an uninterrupted progress, but rather implies a 

 complicated backward and forward movement, of 

 which an irregular progress is the differential re- 

 sult. And as to the second point, it is just one 

 of the triumphs of Darwinism, as regards specu- 

 lative consistency with facts, that it does account 

 for the alteration in the series of effects which 

 occurs as we approach the origin of mankind. 

 For when intelligence has increased pari passu 

 with physical advantages up to a certain point, 

 the variations in intelligence begin to become 

 more valuable than any variations in physical 

 constitution, and consequently become predomi- 

 nantly subject to the operation of natural selec- 

 tion, to the comparative neglect of purely physi- 

 cal variations. A change of this sort, if prolonged 

 for a sufficient length of time, would go far to ac- 

 count for the greatness of the mental difference 

 between men and apes, as contrasted with the 

 smallness of the structural difference. 



That Mr. Mivart should fail to appreciate this 

 point, long since suggested by Mr. Wallace, is 

 perhaps not to be wondered at, since he reduces 

 the inquiry to a mere controversy in which he 



