i86 SOME RECENT DEVELOPMENTS 



no fusion of the pronuclei, but merely a re-arrange- 

 ment of the chromatin threads. Zacharias and 

 Hertwig have suggested that fusion really does 

 occur but may have been overlooked, but for the 

 present the point cannot be considered settled. It 

 is possible indeed that the details are not the 

 same in all cases. 



The equal division of male and female elements 

 in the first segmentation, a point in which Nuss- 

 baum and van Beneden agree and which has been 

 confirmed by others, is of the highest possible 

 interest and importance. If it should prove to 

 occur in the later as well as in the earliest stages 

 of development, then, as pointed out above, it will 

 follow that the nucleus of each cell in the body of 

 the adult animal will contain male and female 

 elements derived from the male and female pro- 

 nuclei *'.*., from the father and mother in precisely 

 equal amounts. In other words, each cell of the 

 adult body may be spoken of as hermaphrodite. If 

 this is true, then the egg, which is merely an epi- 

 thelial cell indistinguishable in its early stages from 

 the surrounding cells, must itself be hermaphrodite. 

 The further suggestion at once presents itself: Is 

 not the extrusion of the polar bodies a casting out 

 of the male elements of the egg ? 



This is a view which in one form or another 

 has commended itself to many embryologists. 

 Balfour first suggested that the extrusion of the 

 polar bodies was a device for ridding the egg of 

 its male elements, and so ensuring that cross ferti- 

 lisation must occur, the advantage of which as 



