DESCRIPTION OF THE SEXUAL PRODUCTS. 



13 



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Tig. 5. Egg from a Rabbit's follicle which was 2 mm. in diameter, after WALDEYER. It is 

 surrounded by the zona pellucida (z.p), on which there rest at one place follicular cells (/.z). 

 The yolk contains detitoplasmic granules (d). In the germinative vesicle (.6) the nuclear 

 network (k.n) is especially marked, and containe a large germinative dot (k.f), 



(z.p) appears radially striate, since it is traversed by numerous pore- 

 canals, into which, as long as the egg remains in the GRAAFIAN follicle, 

 very fine projections of the follicular cells (f.z) penetrate. These 

 fuse with the egg-plasm, and are probably concerned in the nutrition 

 <ind growth of the contents of the egg. (RETZIUS.) 



The human ovum is wonderfully like the egg of Mammals in size, 

 in the condition of its contents, and the nature of its membranes. 

 However, it always can be distinguished by means of special, though 

 trifling, characteristics, as the careful investigations of NAGEL have 

 shown. Whereas in the Rabbit lustrous, fat-like spherules render 

 the yolk cloudy, the human ovum retains its transparency during 

 all stages of development, so that one may recognise most ac- 

 .curately all its structural details, even on the living object. The 

 yolk is divided into two layers. The inner layer contains principally 

 deutoplasm, which produces in this case, contrary to most of the 

 Mammals, only a slight cloudiness ; it consists in part of feebly 

 lustrous, in part of highly refractive fragments, some coarser, some 

 finer ; but it is not possible to recognise the mutual boundaries of 



