CHAPTER VII. 



The Ultimate Sex-Elements {General and Historical). 



In our analysis of sex-characters we have followed the general 

 course of biological history. We first passed from the form 

 and habit of a male or female organism to the structure and 

 functions of the sexual organs. In discussing hermaphroditism, 

 we had occasion to refer to a third step of biological analysis, 

 that which involves an investigation of the properties of the 



Mammalian ovum, showing nucleolus («), nucleus {F), ^-olk (c), 

 external porous zone or zona pellucida (<f ), and follicular 

 cells (e). — From Hertwig, after Waldeyer. 



tissues. Now it is necessary to penetrate deeper, namely, to the 

 sex-cells After these have been considered, not only in them- 

 selves, but finally and fundamentally in terms of the changes in 

 the p7'oioplasni that make them what they are, then we shall be 

 in a better position to re-ascend to some of the problems of 

 reproduction. 



F 



