THE HIGHER SOCIAL LEVELS 147 



of social evolution. The principle of division- 

 of-labor is a useful tool in describing certain 

 levels of society but below these levels, as gen- 

 erally recognized, we have found in the com- 

 munity organizations discussed early in the present 

 book, that there is a division of labor between 

 plants as photosynthetic machines and the ani- 

 mals as consumers. With the animal constit- 

 uents of the community, there are the key in- 

 dustry animals that feed upon raw plant food 

 and make it available, in the form of their own 

 flesh, for the consumption of others. With all 

 sexual animals everywhere, there is a definite 

 division-of-labor between the sexes, so that if this 

 criterion alone were strictly applied, all such 

 animals must be regarded as being definitely social. 

 Similarly, if we examine the frequent limitation 

 of societies to those groupings which consists of a 

 consociation of parents and offspring, we find that 

 these begin with the partial parental care of eggs 

 such as is given by certain male fishes that pick 

 out and stand guard over a definite location in a 

 brook; into this holding females may come and 

 go, each contributing a share of the eggs, while 

 the male stays by, guarding the eggs from enemies 

 until such time as his drive towards breeding 

 activities ceases, when he abandons the formerly 

 carefully guarded eggs to their fate. Recogniza- 



