SOCIAL TRANSITIONS 249 



ing twenty-three species, (24) ) schools of fishes, and 

 the swarms of animals spoken of in the second chap- 

 ter, all of these instances test and stretch in varied 

 ways the idea that only those continuing aggrega- 

 tions of animals which grow out of sexual and 

 familial interrelations are truly social. 



Inherited behavior patterns, the forerunners of 

 instincts, and sexual differences extend down to the 

 protozoa; so do continuing family groups, especially 

 in the form of structurally connected colonial or- 

 ganisms. Group survival values are present in groups 

 of organisms in which sex has not yet evolved, as 

 well as among those in which sex is elaborately de- 

 veloped. In the light of such considerations it be- 

 comes exceedingly difficult to establish any one line 

 above which life is to be regarded as truly social 

 and below which we have only differing degrees of 

 sub-social relations. Here, as happens so frequently 

 in biology, we are confronted with a gradual devel- 

 opment of real differences without being able to 

 put a finger with surety on any one clearly defined 

 break in the continuity. The slow accumulation of 

 more and more social tendencies leads finally by 

 small steps to something that is apparently different. 

 If we disregard the intermediate stages the differ- 

 ence may appear pronounced, but if we focus on 

 these intermediates it will be only for the sake of 



