1^0. 644] 



TRANSFORMATION OF SEX 



207 



dividuals into males is a prolonged process requiring two 

 years, and where the future male larv^se are subjected to 

 the so-called female influence during the entire period, 

 the Miillerian duct does not appear. At metamorphosis 

 when the definitive testes are fully formed and sperma- 

 tozoa are beginning to appear the cellular cords repre- 

 senting the vestigial Miillerian ducts of the male form 

 but do not develop. If Witschi's interpretation were 

 correct, one would certainly expect to find marked de- 

 velopment and hypertrophy of the Miillerian ducts in R. 

 catesheiana because of their being so long exposed to 

 female influence. As a matter of fact, these structures 

 in the male bullfrog are less developed than in other 

 forms. 



The same criticism applies to the so-called develop- 

 mental correlation of the Miillerian duct with the gonad 

 of the same side in cases of lateral hermaphroditism. 

 What Witschi terms lateral hermaphrodites are nothing 

 more than larvae or young frogs which show the defini- 

 tive testis developing out of the pro-testis (larval male 

 Bidder's organ) faster on one side than on the other. 

 (See Witschi, Am. Nat., page 533.) In the end such ani- 

 mals develop into definite males with testes symmetri- 

 cally formed. True lateral hermaphroditism in adult 

 frogs is an exceedingly rare phenomenon. In the wri- 

 ter's material it is rare to find both definitive testes de- 

 veloping out of the pro-testes at the same rate, one gland 

 may be the finished gonad, the other the pro-testis un- 

 dergoing degeneration. Such larvae are in no sense to 

 be regarded as lateral hermaphrodites. There is no de- 

 velopmental correlation of the Miillerian ducts with the 

 gonad of the same side in R. catesheiana and R. pipiens, 

 because there are no ducts formed until after the defini- 

 tive testes are formed. Regarding the other somatic sex 

 characters such as seminal vesicles and thumb cushions, 

 it should l>e pointed out that the thumb pad in R. cates- 

 heiana is not formed until after metamorphosis when 



