76 PETER OKKELBERG 



that one merges more or less into the other. In many cases 

 oocytes occur even in the center of the testes, and Cerruti ('07) 

 also found folUcles which contained spermatozoa in Bidder's 

 organ. With age, however, the boundary between Bidder's organ 

 and the testis becomes more and more definite. 



Pfliiger ('82), one of the early workers on the sex problem in 

 frogs, came to the conclusion that in recently metamorphosed 

 frogs there are three kinds of individuals, namely, males, females, 

 and hermaphrodites. During development the hermaphrodites 

 become definitive males and females, so that in the adult condi- 

 tion the number of males and females is about equal. Pfliiger 

 also found that in certain races of frogs there is a greater tendency 

 toward juvenile hermaphroditism than in others. An examina- 

 tion of recently metamorphosed frogs collected in nature from 

 three different geographical regions gave the following results: 



Collections of adult frogs from the three regions showed that 

 the number of males and females was approximately equal. The 

 conclusion was reached that the young are often hermaphroditic 

 and do not reveal the final sex condition of the animal. 



R. Hertwig ('05, '06, '07) also found that young frogs showed a 

 tendency toward juvenile hermaphroditism. In two laboratory 

 cultures, in which all the larvae were brought beyond metamor- 

 phosis, he found forty-three females and eighteen males in one 

 and forty-seven females and eight males in the other. He be- 

 lieved that the females were pure and that only the males were 

 hermaphroditic, and this form of hermaphroditism he termed 

 rudimentary protogynic. Schmitt-Marcel ('08) made micro- 

 scopic examinations of the sex glands of a large number of Rana 

 temporaria in different stages after metamorphosis and con- 

 cluded that all the intermediates or hei'maphrodites became 

 males. Kuschakewitsch ('10) worked on Rana esculenta and 



