378 CHARLES H. SWIFT 



He believed that cells of the germinal epithelium migrated into 

 the subjacent mesenchyme and grouped themselves into cords 

 which later united with the overlying epithelium, while Janosik 

 described the sex cords arising as invaginations or processes 

 of the germinal epithelium. For a very complete* account of the 

 origin of rete cords and the two series of sex cords in the female 

 and the single series in the male, the reader is referred to Allen 

 ('04) and Firket ('14). 



Ntissbaum ('80) in Rana and in Teleosts, agreed with most of 

 investigators of the period prior to Mihalkowics, that the seg- 

 mental or medullary cords arose as outgrowths of the Malphigian 

 capsules. However, he disagreed with them as to the origin 

 of the large clear, primordial germ-cells which were present in 

 the cords and germinal epithelium. He did not believe them 

 to be differentiated coelmic cells because he found them away 

 from the site of the gonads, in the mesentery, because there 

 were no transition forms and because they contained a great 

 deal of vitellus, which was not present in the neighboring cells 

 of the germinal epithelium. He believed them to be primitive 

 cells and the direct ancestors of the adult sexual cells. 



In passing it should be said that Ntissbaum was the first to 

 hint at a distant site of origin and migration for the primordial 

 germ-cells. He also formulated the hypothesis that ''the sex- 

 ual cells do not come from any cells that have given up their 

 embryonic character or have gone into building any part of the 

 body, nor do sexual cells ever go into body formation." Here, 

 then, is a suggestion of the geim-plasm idea. 



Laulanie ('86), in the chick, thought that the primordial sex- 

 ual gland was bi-sexual; that the germinal epithelium produced 

 the female elements and that the male elements or cells were 

 present in the network of cords, which were developed from the 

 stroma in the midst of the gonad. The cortical ovules, in the 

 germinal epithelium were female and the medullary ovules were 

 male. According to his idea, the gonad was not indifferent but 

 hermaphroditic. Later on in development one of the sexual 

 elements degenerated and the gland became male or female as 



