FOOD AS A FACTOR IN THE DETERMINATION OF SEX. 



53 



and is not sufficiently great in either case to warrant the conclu- 

 sion that sex has been influenced by the rapid development due 

 to the character of the food. The tables show also that a strictly 

 vegetable diet has seemingly no influence on sex determination 

 in Bufo. The slight excess of females in Lot B of each series is 

 but little more than that which, according to my investigations, 

 is the normal excess for the species, and it is therefore well within 

 the limits of possible normal variation. In both series the devel- 

 opment of the tadpoles that were nourished on a mixed diet (Lot 

 C) was, for some unknown reason, considerably retarded and the 

 individuals that completed metamorphosis were, as a rule, smaller 

 than those of any of the other lots. Both series gave an excess 

 of males in Lot C. This excess, however, is not great enough to 

 justify the assumption that a slow development tends to produce 

 a greater proportion of males, any more than the excess of females 

 among the tadpoles fed on the yolk of egg warrants the conclu- 

 sion that rapidity of growth favors the development of a greater 

 proportion of females. 



The results of these experiments, therefore, seem to show that 

 the character of the food received by the tadpoles is not in itself 

 a decisive factor in determining sex in Bufo, although it has much 

 to do with the rate of development and with the size of the 

 individuals. 



The results of the experiments as given in Tables I. and II. 

 are summarized in Table IV. 



Table IV. 



Of the total of 1,536 individuals in which sex was ascertained, 

 823 or 53.58 per cent, were females. The excess of females, 

 therefore, is but 1.7 per cent, more than the normal excess as 

 ascertained by the examination of the sex of 500 young toads 



