200 



THE AMERICAN NATURALIST [Vol. LVI 



forty-one. Among these forty-one cases, there are but 

 twenty-seven true hermaphrodites. Crew 's cases, twenty- 

 one to thirty-three, inclusive, are not hermaphrodites, 

 nor is case thirty-eight, as none of the animals possess 

 ovotestes and some are entirely without gonads. True 

 hermaphroditism in frogs is a permanent and pathologi- 

 cal condition, probably due to a mix-up in the genetic 

 constitution of the individual, and is not to be confused 

 with the present problem which has to do with a normal 

 but transitory embryological process. 



Much has been written about the marked sex poten- 

 cies " of various portions of the gonads in so-called sex- 

 ually intermediate frogs, i.e., females transforming into 

 males. It is claimed that the outer rind of the gonad 

 exerts a profound female sex influence, while the inner 

 portion exerts a purely male influence. Germ-cells re- 

 maining in the outer husk (the main portion of the larval 

 gonad by the way) of the gland are female, those migra- 

 ting into the central part among the sex cords become 

 male. All such speculations are based upon misinter- 

 pretations. The outer portion or husk of the larval male 

 gonad is simply the pro-testis, the cells of which are un- 

 dergoing a precocious maturation cycle just as they do 

 in the organ of Bidder in Biifo, the inner portion or sex 

 cord region is where the definitive gonad begins develop- 

 ment and as it spreads and grows the embryonic male 

 gonad degenerates and disappears. It is in the region of 

 most marked "female " tendencies that the writer finds 

 in the bullfrog entire cysts of unmistakahle spermato- 

 cytes, and occasional spermatids (Fig. 1, e). In other 

 words, the pro-testis — what Witschi regards as an ovary 

 — can in the bullfrog, where its development is greatly 

 prolonged, give rise to practically mature male sex prod- 

 ucts. Recently, the writer made an observation of con- 

 siderable interest. In the degenerating Bidder's organ 

 (pro-testis) of a two-year-old male larva in which forma- 

 tion of the definitive testis had been delayed until meta- 

 morphosis and in which the oviform type of degeneration 



