CHAPTEE VI 



NATURAL SELECTION AND ENVIRONMENT 



I HATE attempted to show that animal development 

 has not been an aimless drifting. Functions devel- 

 'oped and organs arose and were perfected in a certain 

 order. First the purely vegetative organs appeared, 

 and the animal lived for digestion and reproduction ; 

 then came muscle and it brought with it nerve. But 

 these were not enough ; the brain had all the time been 

 gradually improving, and now it becomes the domi- 

 nant function to which all others are subordinated. The 

 experiment was fairly tried. Mere digestion and re- 

 production are carried to about the highest perfection 

 which can be expected of them in worms and moUusks. 

 The bird tried what could be done with digestion min- 

 istering to locomotion guided by the very keenest sense- 

 organs and controlled by no mean brain. Even this 

 experiment was not a success. But one organ re- 

 mained, the braia, and on its mental possibilities de- 

 pend the future of the animal kingdom. Vegetative or- 

 gans and muscle have been tried and foimd wanting.' 



We have followed hastily the development of mind. 

 The mind began its career as the servant of digestion, 

 recognizing and aiding to attain food. Action is at 

 first mainly reflex. But conscious perception plays an 

 ever more important part. The animal is at first 

 guided by natural selection through the survival of 



' See chart, p. 310. 



