SUMMARY 301 



with companions and found food plentiful ; and 

 when the impulse to live in society again asserts 

 itself, it not only repeats its former experience 

 but hands on the habit thus acquired to those of 

 the next generation that happen to accompany 

 it. Granting, however, that by successive 

 increments in the distance traversed, traditional 

 guidance may in time accomplish much, it 

 cannot account for all the known facts, it 

 cannot at any rate explain the fact that in some 

 cases the inexperienced offspring finds its way 

 to the food area without guidance. Something, 

 therefore, is inherited. And my suggestion is 

 this : That the gregarious instinct, the ancient 

 origin of which we can infer from its manifesta- 

 tion in so many and diverse forms of life, 

 supplies the material upon which evolution 

 works ; that variations of the initial impulse, at 

 first shght and not in themselves of selection 

 value, in so far as they coincide in direction with 

 modifications of procedure due to experience or 

 tradition, are preserved ; and that, in the process 

 of time, they are so accumulated as to form 

 a specific congenital endowment determining 

 a definite mode of behaviour. 



