FEMALE REPRODUCTIVE CELLS 



475 



as though it were a male element that had been added to the egg nucleus 

 instead of its own sister cell, the second polar body. This process is 

 shown in Figure 447, which is copied from Brauer. 



The other type of maturation, Brauer's first type, may be said to be 

 like the one that we have just described except that the second polar body 



FIG. 447. Artemia salina. Several stages in the maturation of the kind of parthenogenetic 

 egg that gives off two polar bodies. A, formation of first polar body (p.b. 2 ) ; 84 dyads in this 

 polar body and 84 others in remaining nucleus; B, second division of the egg chromatin, 

 which results in a second polar body with 84 single chromosomes and an egg nucleus with 84 

 chromosomes; B, return of the second polar body (p.b. 2 ) ; C, D, E, three stages in the union 

 of the second polar body and in the first cleavage division of the completed zygote. (From 

 WILSON after A. BRAUER.) 



is never formed, the chromosomes that formed it in the preceding exam- 

 ple merely remaining in place. In fact, it seems a useless proceeding 

 for this second maturation cleavage to take place in any event, when the 

 chromosomes are to immediately return and again join those from which 

 they had been separated but shortly before. The latter method, there- 

 fore, seems to be the ultimate specialization, while Brauer's second 

 method is a more primitive process. Figure 448, from the same source 

 as 447, shows some of the principal stages in this process. 



