ORIGIN OF DEFINITIVE SEX-CELLS 445 



buds — the first sexual cords as described by von Mihalcowics 

 ('85) — a number of primordial ova were involved. Others, 

 however, remained in the germinal epithelium to which he now 

 gave the name layer of primitive ova. At this time the germinal 

 epithelium, or layer of primitive ova, according to Hoffmann, 

 is composed of two kinds of cells, the ordinary prismatic peri- 

 toneal epithelial cells and the large spherical primordial ova. 

 Following the appearance of the first sexual cords the primordial 

 germ-cells in the germinal epithelium were observed to be divid- 

 ing actively, which accounted in part for the increasing thickness 

 of the layer of primordial ova. 



At this point lobulations began to appear on the deeper sur- 

 face of the germinal epithelium. These were the beginnings of the 

 second series of sexual cords, and in them the primordial ova 

 began to transform themselves into ovarian ova. In addition, 

 and this is most important, the young ovarian ova now began 

 to invest themselves with a layer of cells, which Hoffmann called 

 'membrane granuleuse.' These cells resembled in every way 

 the second type of cell found in the germinal epithelium, which 

 were of undoubted coelomic epithelium descent. 



The following quotation from Hoffmann will be of interest: 



Les observations de Waldeyer auront tou jours une grande valeur, 

 puisque c'est lui, qui le premier a montre que de Toeuf primitif se 

 developpe I'oeuf ovarien. D'apres lui la membrane granuleuse et 

 Tovule primordial derivent d'une meme couche germinative. Je I'ai 

 cru aussi autrefois, mais a present je ne partage plus cette maniere de 

 voir parce que je suis arrive a la conclusion, que les ovules primordiaux 

 ne se forment pas de Tepithelium peritoneal, mais qu'ils viennent 

 s'ebaucher dejadans les periodes de developpement, quand des cellules 

 peritoneales n'existent encore, comme cela a ete explique plus tot. 



Bouin COO), Allen ('04), von Winiwarter and Sainmont ('08), 

 using Rana temporaria, the pig and rabbit, and the cat, respec- 

 tively, drew the conclusion from their researches that the de- 

 finitive ova are derived from the germinal epithelium. 



Rubaschkin ('12), working with the guinea-pig, stated that the 

 definitive sex-cells in both testis and ovary are descendants of 

 the primordial germ-cells. Rubaschkin used as his criterion for 

 distinguishing the primordial germ-cells the granular type of 



