HORMONES IN DIFFERENTIATION OF SEX 



93 



TABLE 2.1 



The ejects of synthetic male and female sex hormones on the differentiation of 

 the gonads in various species of amphibians. 

 The cases listed are those in which a complete, or near complete, and histologically norma 

 transformation was achieved by the age of metamorphosis. In some species the reversal wa 

 permanent and functional. For details see text. 



ACTION OF MALE HORMONE ON FEMALES 



morphosis all tadpoles are females (Table 

 2.1). This result has been reported in R. 

 esculenta (Padoa, 1942), in R. sylvatica 

 (Witschi, 1951, 1952, 1953), and Puckett 

 (1939, 1940) obtained the same effect in R. 

 catesbiana when a gonadotrophin was given 

 simultaneously with the estrogen. However, 

 such transformations, although histologi- 

 cally complete, are not in all cases perma- 

 nent (Gallien, 1955) ; moreover, the effects 

 of high dosages of the same hormone may 

 be quite different, as wdll be shown. For 

 other species only partial transformations 

 have been found, as in R. clamitans (jMintz, 

 Foote and Witschi, 1945) and in R. pipiens 

 (Foote, 1938). A similar type of incomplete 

 transformation by the female hormone has 

 recently been reported in the tree frog, 

 Pseudacris (Witschi, Foote and Chang, 

 1958) , again suggesting that in their pattern 

 of response to sex hormones the Hylidae re- 

 semble the Ranidae. 



Various other anuran species have yielded 

 divergent results. In the primitive frog, 



Xenopus laevis, complete and functional 

 transformation of males is effected by an 

 aqueous solution of estradiol benzoate (Gal- 

 lien, 1953), and in the toad {Bufo ameri- 

 canus, Chang, 1955) low doses of estradiol 

 completely transform testes into ovaries 

 although high doses have little effect. Fi- 

 nally, in Discoglossus the effect of estradiol 

 is purely feminizing but the transformation 

 is incomplete, the males exhibiting all de- 

 grees of intersexuality without obvious re- 

 lation to dosage (Gallien, 1955). 



Paradoxical ejfects. Thus far emphasis 

 has been placed chiefly on cases in which 

 sex hormones have acted in a sex-specific 

 manner, each type of hormone directly or 

 indirectly promoting the development of 

 structures of the appropriate sex, while in- 

 hibiting or behaving in neutral fashion to- 

 ward those of the other. Reference has been 

 made more than once, however, to the fact 

 that in other cases the effects are just the 

 reverse of theoretical expectation and op- 

 posed to the concept of hormones as specific 



