Sex as an Adaptation 



43 1 



Now, in certain cases of parthenogenesis, it has been found 

 that one of the polar bodies may not be given off, but, remain- 

 ing in the egg, its nucleus reunites with the egg nucleus, and 

 thus takes the place of the spermatozoon, which does exactly 

 the same thing when it fertilizes the egg, i.e. the nucleus of 



MOO 



Fig. 7. — Diagram showing the maturation of the spermatozoon. 



the spermatozoon unites with the nucleus of the egg. This 

 fact in regard to the action of the polar body in fertilization 

 is not as surprising as appears at first sight, for if each of the 

 polar bodies is equivalent to a spermatozoon, the fertilization 

 of the egg by one of its own polar bodies conforms to theory. 

 There is a considerable body of evidence showing that 

 in many eggs at one of the two maturation divisions the 



