2 RIPE OVARIAN OVUM. 



the yolk. I have never yet seen the limits of it, though it is very 

 common to see the coarsest yolk-gramiles lying in its meshes. Some 

 of these are shewn in Plate xiii. Fig. 2, y. ^." 



Dr Schultz, by employing special methods of hardening and 

 cutting sections of the whole ^gg, has been able to shew that 

 this network extends, in the form of fine radial lines, from the 

 centre to the circumference ; and he rightly states, that it 

 exhibits no cell-like structures. I have detected this network 

 extending throughout the whole yolk in young eggs, but 

 have failed to see it with the distinctness which Dr Schultz 

 attributes to it in the ripe ovum. Since it is my intention to 

 enter fully both into the structure and meaning of this net- 

 work in my account of a later stage, I say no more about it 

 here. 



At one pole of the ripe ovum a slight examination demon- 

 strates the presence of a small circular spot, sharply distin- 

 guished from the remainder of the yolk by its lighter colour. 

 Around this spot is an area which is also of a lighter colour 

 than the yolk, and the outer border of which gradually shades 

 into the normal tint of the yolk. If a section be made 

 through this part (vide PL I. fig. 1) the circular spot will be 

 found to be the germinal vesicle, and the area around it a 

 disc of yolk containing smaller spherules than the surround- 

 ing parts. The germinal vesicle possessed the same structure 

 in both the ripe eggs examined by me ; and, in both, it was 

 situated quite on the external surface of the yolk. 



lu one of my specimens it was flat above, but convex 

 below ; in the other and, on the whole, the better preserved of 

 the two, it had the somewhat quadrangular but rather irregular 

 section represented ia PL I. fig. 1. It consisted of a thick- 

 ish membrane and its primitive contents. The membrane 

 surrounded the upper part of the contents and exhibited 

 numerous folds and creases (vide fig. 1). As it extended down- 

 wards it became thinner, and completely disappeared at some 

 little distance from the lower end of the contents. These, 

 therefore, rested below on the yolk. At its circumference the 

 membrane of the disc was produced into a kind of fold, forming 

 a rim which rested on the surface of the yolk. 



In neither of my specimens is the cavity in the upper part 



