3O HELEN DEAN KING. 



viduals which come from the eggs of the left ovary. Whatever 

 the factors may be which normally determine sex in Bufo they 

 appear to have a similar action on the eggs of both ovaries. 



II. THE INFLUENCE OF" STARVATION ON SEX-DE- 

 TERMINATION IN BUFO. 



During the course of my former experiments an attempt was 

 made to ascertain whether a scarcity of food tends to produce a 

 relatively greater number of males, as several investigators have 

 maintained. The mortality among the young tadpoles was so 

 great, however, that the experiment was abandoned for the time. 

 In the spring of 1907 this experiment was repeated on a much 

 larger scale. Eight hundred eggs which had been laid and 

 normally fertilized in the laboratory on the morning of March 30, 

 were placed in a large tank containing only water and clean sand. 

 No food of any kind was given the tadpoles at first and, as might 

 be expected, they began dying in great numbers about two weeks 

 after hatching. Until the beginning of May the only food that 

 the larvae obtained was the dead bodies of their companions which 

 were devoured before they could be removed. The tadpoles that 

 lived developed very slowly, and in order to prevent all of them 

 from dying they were given a small amount of meat on the second 

 of May and once a week thereafter. Of the 800 individuals with 

 which the experiment started only 59 lived until their sex could 

 be ascertained. Of this number 24 were males and 35, or 59.32 

 per cent., were females. This number of individuals is, of course, 

 too small to be of much value for statistical purposes, yet the re- 

 sults of the experiment, as far as they go, seem to indicate that 

 scarcity of food has no influence whatever on sex-determination 

 in Bufo. Since the only food that the tadpoles received was 

 animal food it might be inferred, from the rather large proportion 

 of females that \vere obtained, that nitrogenous food favors the pro- 

 duction of females, as Yung ('85) has maintained. The excess of 

 females does not seem to me sufficiently large, however, to war- 

 rant such a conclusion. Moreover my previous experiments 

 showed that in a total of 464 individuals that received an exclu- 

 sive meat diet only 246, or 53.01 per cent., were females, thus 

 making it highly improbable that nitrogenous food has any in- 

 fluence on the determination of sex in Bufo. 



