Embryonic History of the Germ-Cells of the Loggerhead Turtle. 331 



(1908) as respects Bufo lentiginosus. Miss King finds no evidence in 

 support of a secondary source of germ-cells from the peritoneal epithe- 

 lium. Moreover, in Chrysemys, Allen (1906) traced the germ-cells to 

 maturity without finding any evidence of a transformation of peri- 

 toneal cells into germ-cells. The same is true also of Caretta at least 

 to the 32-day stage. 



Dustin (1910) has repeated the investigation of Allen on Chrysemys 

 marginata, and now confirms Allen's observations regarding the ento- 

 dermal origin of the extra-regional germ-cells in this form. Dustin 

 still claims, however, that in this form also there is a secondary peri- 

 toneal source of origin of germ-cells or ''gonocytes." But his illustra- 

 tions do not seem to support this conclusion. The so-called "secondary 

 gonocytes" as illustrated are smaller than certain other germ-cells des- 

 ignated ''primary gonocytes," but no unequivocal transitions appear 

 between the mesenchyme cells of the sexual gland or its peritoneal 

 cells and the secondary gonocytes. 



In a postscript (p. 33) Allen (1911) records preliminary results in the 

 case of Necturus and Amblystoma similar to those reported by Dustin 

 for Triton, namely, an actual mesodermal origin of sex-cells. Allen 

 disposes of the conflicting views regarding the origin of germ-cells in 

 amphibia by the claim that in the urodeles the usual source of origin 

 of the germ-cells is the mesoderm; that in the anurans the source of 

 origin is the entoderm; at the same time, he admits the possibility of 

 exceptions. 



A similar mesodermal origin of the sex-cell is described also for the 

 teleost Lophius (Dodds, 1910). Wheeler's results on Petromyzon 

 (1899) indicate that the germ-cells may become included in the meso- 

 derm at the time it separates from the entoderm. Jarvis (1908) 

 reports an entodermal origin of the primordial germ-cells also in the 

 horned toad, Phrynosoma cornutum. 



Gatenby (1916) has reexamined the evidence in the case of Rana 

 {temporaria) , Salamandra , Triton {rnolge), and Amhlydoma. The 

 observations on these forms accord in all the main points and "resemble 

 Bufo in the history of germ-cell production," which it is claimed pro- 

 ceeds by a differentiation of germ-cells ("secondary gonocytes") from 

 the germinal epithelium, in accord with Waldeyer's original theory. 

 Gatenby thus disagrees with the conclusions of King (1908) for Bufo 

 lentiginosus, Allen (1907) for Rana pipiens, and Kuschakewitsch for 

 Rana esculenta; but agrees with the conclusion of Dustin (1907) for 

 Trito7i, Rana, and Bufo, and with the earlier conclusion of Kuschake- 

 witsch (1907) for Rana pipiens. 



Gatenby, however, admits "that some germ-cells possibly migrate 

 from the entoderm of the yolk-sac," but "feels sure that during life 

 very large additional reinforcements of germ-cells arise in the epithe- 

 lium of the gonad of jimphibia" (p. 276). His criticism, then, of the 



