244 COOK 



maintain underneath them immense systems of subterranean 

 fungus gardens and chambers for storing and curing the com- 

 minuted wood of which the gardens are built. This material is 

 brought in from long distances by means of tunnels bored 

 through the earth or covered passages built over rocks and 

 tree trunks. 



Politism is to be classed as a specialization of growth-stages, 

 because among the bees, at least, it has been found that the 

 differentiation of the sterile worker from the fertile queen is 

 determined by the amount and quantity of food given to the 

 growing larva. It is difficult to believe, however, that this is 

 true of the termites, for the young are not stationary grubs as 

 among the bees, but active creatures which circulate to all parts 

 of the nest, so that a consistent policy of feeding seems quite 

 impracticable. Moreover, the workers and other sterile castes 

 of the termites are not undeveloped females alone, as among the 

 bees, but consist of stunted forms of both sexes. 



DIVERSITY OF NORMAL DESCENT (HETERISM). 



The individuals of a specific group may appear closely alike 

 when compared with those of other species, but when compared 

 with each other their diversity becomes obvious. Many evolu- 

 tionary writers have believed in a principle of heredity which 

 would make all the members of a species " exactly alike," and 

 have then assumed that intraspecific diversity is due to varia- 

 tion of environmental experiences in one stage or another of the 

 life-history of the differing individuals. The kinetic theory 

 depends upon neither of these hypotheses, but recognizes the 

 diversity of individuals inside the species as a normal and 

 highly significant evolutionary phenomenon, for which the term 

 heterism has been proposed. Plants and animals propagated 

 under the same conditions may appear more similar than others 

 of the same stock grown under diverse conditions, but they do 

 not tend to any complete uniformity except as this is brought 

 about by the abnormal inbreeding to which domesticated vari- 

 eties are usually subjected. 



Heterism might be defined further as the morphological 

 aspect of symbasis. To support and hold together the organic 



