ADAPTATION OF ORGANISMS 331 



1. Communal Associations 



Perhaps the simplest organismal associations are repre- 

 sented by GREGARious~"animals, such as Wolves which hunt 

 in packs, and Buffaloes and Horses which herd for protection. 

 Here the association is more or less temporary and there is 

 no division of labor between the members, other than leader- 

 ship by one animal. 



COMMUNAL animals, however, exhibit highly complex asso- 

 ciations in which the members merge, as it were, their indi- 

 viduality in that of the community. This is well exhibited, 

 for example, among the Ants, in which all of the various spe- 

 cies, about 5000 in number, are communal, and in the Wasps 

 and Bees in which all gradations exist from solitary to hive- 

 dwelling species. And, as has been mentioned in the case of 

 the Bees, the division of labor has developed to the extent 

 that structural differentiations have given rise to classes of 

 individuals specially adapted for the performance of certain 

 functions in the economy of the hive. 



It is in Man, however, that we find the highest expression 

 of communal cooperation, because increased intelligence, in 

 particular, makes flexible the stereotyped life as exhibited in 

 the lower forms the human individual being adaptable to 

 the various community tasks. 



But associations are not confined to members of the same 

 species, nor are all an expression of cooperative adaptations. 

 All gradations occur from those which are mutually beneficial 

 to the parties in the pact, to those in which one member 

 secures all the advantage at the expense of the other. 



2. Symbiosis 



The most intimate associations in which the organisms 

 involved are mutually benefited, if not absolutely necessary 



