THE FUNCTION OF CONSCIOUSNESS. 517 



have reacted mutually. Without the cooperation of 

 all these factors, anagenesis seems impossible. 



From this point of view the study of the evolution 

 of mind and its relation to the organic world assumes 

 a new importance. Circumstances have forbidden my 

 entering on this subject in the present volume, but I 

 hope to be able to devote especial attention to it at a 

 future time. One fundamental postulate of mental 

 evolution may, however, be mentioned here. That is, 

 as Spencer has pointed out, the instinct of hunger is 

 at the basis of the activity which has developed the 

 intelligence, while that of sex is at the basis of the de- 

 velopment of the altruistic or social instincts and affec- 

 tions. With this proposition I leave this interesting 

 part of the doctrine of evolution. 



