STRUCTURE AND DEVELOPMENT OP VERTEBRATE OVARY. 131 



Mic.^ Sci./ p. 210): "The protoplnsm which surround? the vesi- 

 cular nuclei acts as a sort of cement substance, holding them 

 together in the form of a ca[)sular membrane round the young 

 ovum. This capsular membrane is the first appearance of the 

 membrana granulosa." 1 must admit that I find nothing similar 

 to this, nor have I met with any special peculiarities (as Eoulis 

 would seem to indicate) in the cells of the germinal epithelium or 

 other cells of the ovary. 



Figure 41 is a representation of an advanced follicle of a six 

 weeks rabbit, containing two ova, which is obviously in the act of 

 dividing into two. Follicles of this kind with more than one ovum 

 are not very uncommon. It appears to me probable that fol- 

 licles, such as that I have figured, were originally formed of a single 

 mass of protoplasm with two nuclei ; but that instead of one 

 of the nuclei atrophying, both of them eventually developed 

 and the protoplasm subsequently divided into two masses. In 

 other cases it is quite possible that follicles with two ova should 

 should rather be regarded as twofollicles notseparated by a septum 

 of stroma. 



On the later stages of development of the ovary I have no 

 complete series of observations. The yolk spherules I find to 

 be first developed in a peripheral layer of the vitellus. I have not 

 been able definitely to decide the relation of the zona radiata to 

 the first formed vitelline membrane. Externally to the zona radiata 

 there may generally be observed a somewhat granular structure, 

 against which the follicle cells abtit, and I cannot agree with 

 Waldeyer (loc. sit., p. 40) that this structure is continuous with 

 the cells of the discus, or with the zona radiata. Is it the re- 

 mains of the first formed vitelline membrane ? I have obtained 

 some evidence in favour of this view, but have not been successful 

 in making observations to satisfy me on the point, and must leave 

 open the question whether my vitelline membrane becomes the 

 Z(ma radiata or whether the zona is not a later and independent 

 formation, but am inclined myself to adopt the latter view. The 

 first formed membrane, whether or no it becomes the zona 

 radiata, is very similar to the vitelline membrane or Elasrao- 

 branchs and arises at a corresponding stage. 



Sn7nwary ofoh.'^en'atioris on the mamwalian ovary. — The general 

 results of my observations on the mammalian ovary are the fol- 

 lowing : — 



(1) The ovary in an eighteen days' embryo consists of a 

 cylindrical ridge attached along the inner side of the Wolffian 

 body, which is formed of two parts; (a) an external epithelium 

 — two or three cells deep (the germinal epithehum) ; (h) a hilus 

 or part forming in the adult the vascular zone, at this stage 



VOL. XVIII. NEW SER. F E 



