52 



HELEN DEAN KING. 



Table II. 



Table III. summarizes the results for Series II. 



Table III. 



The first, conclusion that can be drawn from the above tables is 

 that abundant nutrition alone is not a decisive factor in sex deter- 

 mination in Bufo, as in three cases (Series I., Lot A, Lot C ; 

 Series II., Lot C) more males than females were produced although 

 all of the tadpoles had been well supplied with food during the 

 entire course of the experiments. 



As the tables show, the results of the two series of experiments 

 in which the tadpoles were fed exclusively on meat are not in 

 agreement. In Lot A of Series I., only 48.4 per cent, of the in- 

 dividuals in which sex was ascertained were females ; while in the 

 corresponding lot in Series II. there were many more females than 

 males (20.44 P er cent.). This result does not support Yung's 

 contention that an excess of nitrogenous food leads to the devel- 

 opment of a greater proportion of females, and it seems to indicate 

 that food of this character has no influence in determing sex in 

 Bufo. Again more rapid growth, as shown in the case of the 

 tadpoles that were fed on the yolk of egg, cannot be considered 

 as favoring the development of one sex any more than the other ; 

 for although in both series there was an excess of females in Lot D, 

 this excess varies considerably in the two series (8.02 per cent.) 



