442 CHARLES H. SWIFT 



served in the germinal epithelium of the younger animals studied. 

 This conclusion of his was weakened to a certain extent by a 

 faulty premise, namely, that the ureier were developed from the 

 cells of the general epithelium by a process of differentiation. 

 As will be shown later in this article, in the same forms studied 

 b}^ Waldeyer, the ureier, or primordial germ-cells, arise long 

 before the appearance of the germinal epithelium. 



Balfour ('78) in a study of the development of the vertebrate 

 ovary agreed in the main with the findings of the previous investi- 

 gator in attributing to the germinal epithelium the origin both of 

 the definitive ova and follicular epithelium. Balfour's principal 

 investigations were made on Scyllium, an Elasmobranch, a form 

 in which the primitive ova appear in the germinal epithelium at 

 an early stage. Although he believed that the primitive ova — 

 primordial germ-cells — were derived from the germinal epithe- 

 lium, he, however, thought that the primitive ova in the female 

 were not the true ova but the parent sexual cells which gave rise 

 to the definitive ova. 



Schmiegelow ('82), to quote Bouin, saw in the germinal epi- 

 thelium of a 3"oung chick embryo the large primordial eggs de- 

 scribed twelve years before b}^ Waldeyer. He observed that the 

 germinal epithelium was sharply limited on its deep surface by 

 a basal membrane and that in older embryos anastomosing cords 

 of cells grew down into the subjacent ovarian tissue. These 

 cords contained some primordial eggs and there were others in 

 the stroma between the cords. The author believed that the 

 latter did not emigrate down from the germinal epithelium in the 

 cellular cords, but that they differentiated in situ from the 

 mesenchyme. He believed that both kinds of primordial eggs 

 could give rise to definitive eggs. 



Von Mihalcowics ('85) was the first investigator to observe 

 and appreciate the two proliferations which the germinal epithe- 

 lium undergoes in the female. In his work on the embryos of 

 Amniotes — reptiles, birds and mammals — he also observed the 

 germinal epithelium at the time of its formation from the coe- 

 lomic epithelium. Among the cells contained in it he found 

 primordial ovules or 'grandes cellules sexuelles.' Then this 



