ORGANIC E VOL UTION. 7 1 



facts of biology, and proving so successful in 

 that region, Mr. Darwin proceeded to test it in 

 the region of psychology. The result has been 

 to show that large classes of phenomena in 

 this region which were previously unaccountable 

 become fully intelligible. This is especially the 

 case with the phenomena of instinct, and in a 

 lesser degree with those of reason and con- 

 science. For the theory shows that if structures 

 admit of being moulded to their special uses 

 by natural selection, the same must be true of 

 instincts; and it is found an easy matter to 

 understand how, by seizing upon and fixing, 

 through hereditary beneficial variations of habit 

 (whether instinctive or intelligent), natural selec- 

 tion is as competent to fashion the mental 

 structure of an animal as it is to shape its 

 bodily structure into agreement with the ex- 

 ternal conditions of life. Thus the whole philo- 

 sophy of animal intelligence is greatly elucidated, 



