CHAPTER XIII 



DISTRIBUTION BY SEX 



The function of sex in cell organization can hardly be 

 over-estimated. It is difficult to imagine the possibility of 

 a multicellular body without it. The function of mere con- 

 jugation is of simpler import — as must be more clearly 

 shown. 



After the evolution of the life of single cells, in which 

 a great development is visible, there appears to arise an 

 abrupt and stupendous departure, an evolution into radically 

 different possibilities. This great step upward in evolution 

 must necessarily be first made possible, by pre-existing de- 

 velopments in the one-celled species. Its essential new thing 

 is the association of many cells in mutual dependence instead 

 of in competitive rivalry. This is called the great step in 

 evolution because it is the beginning of division of labor and 

 of specialized abilities, and it is thus the physiological basis 

 of altruism. As soon as a living cell divides and there are 

 two side by side, there develops the question whether they 

 are allies or rivals. If rivals, they repel and oppose one 

 another, and must remain one-celled creatures. Even con- 

 jugation makes but a one-celled creature, and subsequent di- 

 vision two or more such creatures. And association in 

 colonies is only an alliance of similar efficiencies, with 

 specialization only of position, and not in the heredity. But 



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