340 



laterally to the anlagen of the sex-glands. He was unable to study 

 them in earlier stages, or considered it not worth while to master 

 certain difficulties of technique in order to do so. His views are ad- 

 equately expressed in the following paragraph: "D'apres ce qui pre- 

 cede, on voit que nous n'avons pas assiste aux Stades primordiaux de 

 I'edification de I'ebauche genitale. Quels sont les 616ments qui la 

 constituent originellement? C'est ce que nos coupes ne nous permet- 

 tent pas d'affirmer d'une maniere positive. La pr6cocit6 de son ap- 

 parition, ses connexions morphologiques avec le sac vitellin, la simili- 

 tude remarquable qui existe entre les cellules qui la constituent et 

 Celles que renferme le sac vitellin permettent, jusqu'a un certain point, 

 de supposer que les cellules vitellines ont pu emigrer en assez grand 

 nombre par le pedicule vitellin et se localiser au devant de I'aorte, 

 entre les deux veines cardinales. II se pent egalement que les cellules 

 m^senchymateuses et les cellules peritoneales de la region consider6e 

 se soient charg6es de plaquettes vitellines d'une maniere tres precoce." 



Unfortunately he attached little importance to this hypothesis, as 

 shown in the following paragraph of his summary: 



"a) Pendant le d6veloppement de I'ebauche genitale primordiale, 

 les cellules peritoneales qui sont en rapport imm^diat avec la zone 

 genitale se transforment en cellules sexuelles primordiales par ab- 

 sorption de plaquettes vitellines. 



b) Les cellules mesenchyraateuses subissent un processus ana- 

 logue, surtout Celles qui se trouvent situ^es entre les deux veines 

 cardinales. 



c) II nous a ete impossible de saisir les tons premiers Stades 

 de I'histogenese des cellules sexuelles primordiales. Nous avons admis 

 comme possible leur origine aux depens des cellules du sac vitellin." 



From the above it will be seen that he considers it to be positively 

 established that sex-cells do arise from the mesenchyme and peri- 

 toneum. He based this conclusion upon the presence of cells which 

 he claimed to be transitional in character between the typical cells of 

 these tissues and the sex-cells. It is difficult to ascertain from a 

 study of Rana pipiens the accuracy of Bouin's observations upon this 

 point. It is only fair to say that we have thus far been unable to 

 establish the existance of such transition forms in the material at hand. 

 It can be said with certainty that such were not found in Chrysemys 

 after the most painstaking search for them. Cells which appeared to 

 represent stages in the transformation of peritoneal cells into sex- 

 cells, in the case of the pig and rabbit, were so interpreted and re- 

 corded in an earlier paper in which this subject was incidentally 



