42 HELEN DEAN KING. 



lot of frogs that had been poorly nourished, there was a greater 

 proportion of females. Cuenot states that, as the results of all of 

 the feeding experiments that have been made on Rana are con- 

 tradictory, it is evident that nutrition is not an absolutely dominat- 

 ing factor in sex determination. He believes that there is a strong 

 probability that sex is already determined in the egg at the time of 

 deposition. 



As Cuenot used comparatively few individuals in his experi- 

 ments and as his results do not accord with those obtained by 

 Born and Yung, it is obvious that the question of the influence 

 of nutrition in determining the sex of amphibians is still an open 

 one. It is necessary, therefore, that many more experiments 

 should be carried out along the lines suggested by the work of 

 these investigators. 



At the anterior end of the genital organs in the tadpoles of the 

 common American toad, Bnfo lentiginosus, there is found a small 

 rounded structure, the so-called "Bidder's organ " (Fig. I, B), 

 which is composed apparently of undeveloped ova. The function 

 of this organ is unknown, and whether it is a rudimentary ovary, 

 as many investigators have maintained, has not as yet been satis- 

 factorily determined. This body is found in young tadpoles 

 some time before it is possible to distinguish sex ; and it is a 

 permanent organ in the male, disappearing in the female near the 

 end of the second year. If Bidder's organ proves to be a rudi- 

 mentary ovary, then the adult male toads are in a sense hermaph- 

 rodites, although the same cannot be said of the adult female 

 unless the male elements are present in some form that as yet 

 has not been discovered. Because, therefore, of a possible condi- 

 tion of hermaphroditism in the young tadpoles, which might 

 seem to indicate that sex is not already determined at this stage 

 of development, Bnfo lentiginosus was chosen as more favorable 

 material than any common species of Rana for an investigation 

 of the influence of external factors on sex determination. As the 

 tadpoles of Bnfo are somewhat smaller than those of Rana and 

 are easily reared under artificial conditions, they are well adapted 

 for experiments that must, of necessity, extend over a consider- 

 able period of time. 



The present paper records the results of the first of a series of 



