134 ANIMAL LIFE AND SOCIAL GROWTH 



limited area, and that they have reaction systems 

 that allow them to aggregate or to remain together 

 if passively collected. To develop social groups 

 of higher order other qualities are needed, partic- 

 ularly the ability to establish close group inte- 

 gration. The facts show that not all animals 

 whose groups show survival values are necessarily 

 on the way toward becoming more closely social, 

 but that animals, whatever their endowments, 

 could not have developed the social habit had the 

 incipient social stages lacked the type of survival 

 values which has been repeatedly demonstrated 

 for different animal groups and even for sperma- 

 tozoa and bacteria. 



