ASPECTS OF KINETIC EVOLUTION 345 



sexes. For the bees and ants three kinds of mechanisms were 

 provided, and for the termites four kinds, though in reality up- 

 wards of a dozen sorts would be needed to account for the 

 strange diversity of types found in some of the African species. 

 And the most curious thing about the ants and termites is that 

 the animals which exhibit the supposed results of these diverse 

 kinds of mechanisms do not transmit them at all, but are de- 

 scended independently in each generation from sexual insects. 

 Here again it is apparent that new methods of development 

 have been entered upon without requiring any change or dis- 

 placement of the old. With the bees, at least, the heredity is 

 not determined when the egg is laid, or even when it hatches. 

 It is still possible for two or three days to induce the young 

 larva to develop either into a queen or into a worker, by vary- 

 ing the nature and amount of food. The environment deter- 

 mines, evidently, which of the mechanisms shall continue in 

 play and which retire into desuetude. 



There is no need, of course, to continue the discussion in 

 this direction ; doubtless it is too long already. There are 

 those who think only in relations of numbers and spaces ; and 

 for these mechanical forms are a necessity. But for those who 

 approach from the biological side, who are curious to understand 

 nature, and yet not so impatient as to accept even scientific fic- 

 tion at the expense of ascertainable fact, these character-unit 

 mechanisms of heredity do not appear to help, but rather to 

 hinder, clear perception and exposition. 



ALTERNATIVE OR POLARIZED HEREDITY. 



From the standpoint of the kinetic theory it appears possible 

 to reconcile the proposed character-unit phenomena of Men- 

 delism with other facts of alternative descent, without invoking 

 the hypothesis of character-units and pure germ-cells. The 

 phenomena of heterism and symbasis, that is, normal diversity 

 and broad-breeding in specific groups, do not necessitate the 

 character-block assumption. They only require us to suppose 

 that diversity of descent affords a certain amount of molecular 

 tension or attraction, a polarity, as it were, between proto- 

 plasmic elements derived from the different lines of descent. 



