CHAPTER I. 

 The Ripe Ovarian Ovum. 



The ripe ovum is nearly spherical, and, after the removal 

 of its capsule, is found to be unprovided with any form of 

 protecting membrane. 



My investigations on the histology of the ripe ovarian ovum 

 have been made with the ova of the Gray Skate (Raja hatis) 

 only, and owing to a deficiency of material are somewhat 

 imperfect. 



The bulk of the ovum is composed of yolk spherules, 

 imbedded in a protoplasmic matrix. Dr Alexander Schult^S 

 who has studied with great care the constitution of the yolk, 

 finds, near the centre of the ovum, a kernel of small yolk sphe- 

 rules, which is succeeded by a zone of spherules which gradually 

 increase in size as they approach the surface. But, near the 

 surface, he finds a layer in which they again diminish in size 

 and exhibit numerous transitional forms on the way to molecular 

 yolk-granules. These Dr Schultz regards as in a retrogressive 

 condition. 



Another interesting feature about the yolk is the presence 

 in it of a protoplasmic network. Dr Schultz has completely 

 confirmed, and on some points enlarged, my previous observa- 

 tions on this subjects Dr Schultz's confirmation is the more 

 important, since he appears to be unacquainted with my pre- 

 vious investigations. In my paper (loc. cit), after giving a 

 description of the network I make the following statement as 

 to its distribution. 



" A specimen of this kind is represented in Plate xiii. Fig. 2, n. 

 2/, where the meshes of the network are seen to be finer immediately 

 around the nuclei, and coarser in the intervals. The specimen 

 further shews, in the clearest manner, that this network is not 

 divided into areas, each representing a cell and each containing a 

 nucleus. I do not know to what extent this network extends into 



1 ArcJiiv fiir Micro. Anat. Vol. xi. 1875. 



2 Quart. Journ. Micro. Science, Oct. 1874. 



B. 



