A great amount of work has been done on the sexual differentiation of amphibians, but the causal factors have not yet been conclusively demonstrated. It seemed of interest, therefore, to compare the results of previous work on the attempted control of sex differentiation with the effect obtained by the injection of pregneninolone. This is a synthetic sex hormone, which has been demonstrated to produce progestational, androgenic, and estrogenic effects in different animal groups (Inhoffen and Hohlweg, '38; Emmens and Parkes, '39 ; Courrier and Jost, '39 ; Eversole, '41 ; Eversole and D'Angelo, '43). It was thought that testing the effect of pregneninolone on urodeles ( A4mblystoma punctatum) might furnish data for comparison as well as a clue to the activity of this particular synthetic hormone.
Soderwall and Blandau ( '41) have shown that large doses of the crystalline form of pregneninolone were ineffective in inducing heat in rats, while the tablet form (pranone) was effective orally in guinea pigs. However, since others (Emmens and Parkes, '39; Courrier and Jost, '39; Salmon and Salmon, '40) had found that the crystalline form was effective in rats, it was thought wise to use both forms of the hormone 1 The authors wish to acknowledge their sincere appreciation for the help afforded by Dr. Erwin Schwenk of the Shering Corporation, who generously supplied the crystalline pregneninolone and the pranone for this work.
This repreaents, in part, material accepted for the Master of Science degree at New York University.