OF THE VERTEBRATE OVARY. 573 



ooS mm. there appear between the original large cells of the 

 follicle (which he describes as granulosa cells and derives from 

 the germinal epithelium) a number of peculiar small cells. He 

 states that these are of the same nature as the general stroma 

 cells of the ovary, and believes that they originate in the stroma. 

 When the eggs have reached O'l O'i5 mm., he finds that the 

 small and large cells have a very regular alternating arrange- 

 ment. 



Semper records but few observations on the follicular epithe- 

 lium, but describes in Raja the presence of a certain number of 

 large cells amongst smaller cells. He believes that they may 

 develope into ova, and considers them identical with the larger 

 cells described by Schultz, whose interpretations he does not, 

 however, accept. 



My own results accord to a great extent with those of Dr 

 Schultz, as far as the structure of the follicular epithelium is 

 concerned, but I am at one with Semper in rejecting Schultz's 

 interpretations. 



In Scyllium, as has already been mentioned, the follicular 

 epithelium is at first flat and formed of a single layer of uniform 

 cells, each with a considerable amount of clear protoplasm and a 

 granular nucleus. It is bounded externally by a delicate mem- 

 brane the membrana propria folliculi of Waldeyer and in- 

 ternally by the vitelline membrane. In the ovaries of very 

 young animals the cells of the follicular epithelium are more 

 columnar on the side towards the stroma than on the opposite 

 side, but this irregularity soon ceases to exist. 



In many cases the nuclei of the cells of the follicular epithe- 

 lium exhibit a spindle modification, which shews that the growth 

 of the follicular epithelium takes place by the division of its cells. 

 No changes of importance are observable in the follicular epithe- 

 lium till the egg has reached a diameter of more than I mm. 



It should here be stated that I have some doubts respecting 

 the completeness of the history of the epithelium recorded in 

 the sequel. Difficulties have been met with in completely eluci- 

 dating the chronological order of the occurrences, and it is 

 possible that some points have escaped my observation. 



The first important change is the assumption of a palisade- 

 like character by the follicle cells, each cell becoming very narrow 



