CHANGES IN THE OVARY 



117 



Nagel,! and van Winiwarter,^ have followed Waldeyer in suppos- 

 ing that the follicular epithehal cells (which form the innermost 

 layer of the wall of the Graafian folhcle) are derived Uke the ova 

 from the germinal epithehum. Schafer described appearances 

 indicating the possibility of the innermost layer of foUicular 



Fig. 22. — Cortex of pig embryo, showing germinal epithelium, Pfluger's 

 tubes with ova in various stages of development. (From Williams' 

 Obstetrics, Appleton & Co.) 



epithehum being derived from the ovum itself ; but, as he himself 

 pointed out, this view does not involve any morphological ab- 

 surdity if the ova and folhcle-cells have a common origin. Balfour 

 described protoplasmic masses of embryonic ova in which the 

 cells appeared to be united together in such a way as to suggest 



^ Nagel, " Das menschliche Ei," Arch.f, Mih: Anat., vol. xxxi., 1888. 

 ^ Van Winiwarter, " Recherches sur I'Ovogenfese," &c., Arch, dc Biol,, 

 vol. xvii., 1901. 



