MUTUAL AID AND COMMUNAL LIFE AMONG ANIMALS 395 



which are wingless, wingless workers of both sexes not capable 

 of reproduction, and wingless soldiers of both sexes also in- 

 capable of reproduction. The production of new individuals 

 is the sole business of the fertile males and females ; the workers 

 build the nest and collect food, and the soldiers protect the 

 community from the attacks of marauding insects. The egg- 

 laying queen grows to monstrous size in some species, being some- 

 times four or five inches long, while the other individuals of the 

 community are not 

 more than half or 

 three-quarters of an 

 inch long. The great 

 size of the queen is 

 due to the enormous 

 number of eggs in 

 her body. 



We have pointed 

 out elsew r here that 

 the complexity of 

 the bodies of the 

 higher animals de- 

 pends on a speciali- 

 zation or differentia- 

 tion of parts, due 

 to the assumption of 

 different functions or 

 duties bv different 



IS 



parts of the body; that the degree of structural differentiation 

 depends on the degree or extent of division of labor shown in 

 the economy of the animal. It is obvious that the same prin- 

 ciple of division of labor with accompanying modification of 

 structure is the basis of colonial and communal life. It is 

 simply a manifestation of the principle among individuals in- 

 stead of among organs. The division of the necessary labors 

 of life among the different zooids of the colonial jellyfish is 

 plainly the reason for the profound and striking, but always 

 reasonable and explicable, modifications of the typical polyp 

 or medusa body, which is shown by the swimming zooids, the 

 feeding zooids, the sense zooids, and the others of the colony. 

 And similarly in the case of the termite community, the sol- 

 dier individuals are different structurally from the worker in- 



FIG. 247. Termites: 



a, Queen ; 6, male ; c, worker ; 

 d, soldier. 



