CHANGES IN THE OVARY 113 



and von Winiwarter, 1 have followed Waldeyer in supposing that the 

 follicular epithelial cells (which form the innermost layer of the wall 

 of the Graafian follicle) are derived like the ova from the germinal 

 epithelium. Schafer described appearances indicating the possibility 

 of the innermost layer of follicular epithelium being derived from 

 the ovum itself ; but, as he himself pointed out, this view does not 



. -a .- ' L **t.- a t t*V \S*fl '' ^ i 



^ =>'*'' 



FIG. 27. Cortex of pig embryo, showing germinal epithelium, Pfliiger's 

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

 Obstetrics, Appleton & Co.) 



involve any morphological absurdity if the ova and follicle-cells have 

 a common origin. Balfour described protoplasmic masses of em- 

 bryonic ova in which the cells appeared to be united together in 

 such a way as to suggest that one ovum might undergo development 

 at the expense of the others. Somewhat similar appearances have 

 been observed in the bat's ovary by van Beneden, 2 who regarded 



1 Von Winiwarter, "Becherches sur 1'Ovogenese, etc.," Arch, de Biol., 

 vol. xvii., 1901. 



2 Van Beneden and Julin, "Observations sur la Maturation, etc.," Arch, de 

 Biol., vol. i., 1880. 



