143 



CHAPTEE XII. 



INSTINCT AND HABIT. 



DARWIN deals with the development of in- 

 stinct on the same lines as the evolution of 

 life. He assumes the existence of instinct in 

 a simple form, and holds that complex in- 

 stincts are the results of the accumulation of 

 numerous successive slight modifications of 

 simpler instincts. He, however, admits that 

 certain instincts of bees and ants could not 

 have been acquired. These have come by 

 " spontaneous variation " : others are the 

 result of acquired habits inherited through 

 many generations ; these he calls " domestic 

 habits." But beyond general statements 

 Darwin gives no example of the appearance 

 of a new instinct, or of an acquired habit 

 becoming hereditary. 



There is no evidence of any variation in the 

 nature of an instinct, although, like other 

 characteristics, it varies in degree in different 

 members of the same race, and may to some 



