212 



HELEN DEAN KING. 



termination, it is possible that more sperm of one kind are pro- 

 duced in some individuals than in others, and that distinct dif- 

 ferences in the sex ratios might be obtained if lots of eggs from 

 the same female are fertilized with sperm from different males. 

 There is the possibility, also, that the spermatozoa of one kind, 

 if two kinds exist, are produced only in one testicle, or perhaps in 

 considerably greater numbers in one testicle than in the other. 

 It seemed advisable, therefore, in investigating the possible 

 influence of the spermatozoan on the determination of sex in 

 Bufo to carry out the experiment in the following way: a batch 

 of eggs from the right uterus of a female was divided into four 

 lots of from 300-400 eggs each. Each lot of eggs was then fer- 

 tilized with sperm from the right or from the left testicle of one 

 of three different males. 



The sex ratios obtained in this series of experiments are indi- 

 cated in Table II. In this table the males from w r hich the sper- 

 matozoa were obtained are designated as I, 2, 3; while the letters 

 R.T. and L.T. refer to the right and to the left testicle respec- 

 tively. 



TABLE II. 

 EGGS FERTILIZED WITH SPERM FROM DIFFERENT MALES. 



Somewhat different percentages of females were obtained in 

 the various lots, as might be expected in any case. As the series 

 stands in the above table, the greatest difference between the 

 percentages of females in any two lots is but 8.03 per cent. If 

 the percentage of females in all of the individuals that developed 

 from eggs that w T ere fertilized with sperm from male i (50.28 

 per cent.) is substituted for the relatively low percentage (47.61) 

 found in the lot where sperm from only the left testicle had been 

 used for fertilization, the difference between the percentages of 

 females at the two extremes of the series falls to 5.36 per cent., 

 which is only 1.19 per cent, greater than that (4.17) found be- 



