DETERMINATION OF SEX IN AMPHIBIANS. 



Table II. 



135 



With a difference of 30° C. in the temperature of the water in 

 which the two lots of eggs at the extremes of the series were 

 fertihzed there is a difference of only 4.95 per cent, in the pro- 

 portion of females that developed in these lots. This difference 

 is so small that it is evident that temperature, acting at the time 

 of the fertilization of the eggs, is not the dominant factor in the 

 determination of sex in Bufo. 



In this series of experiments, with one exception, the propor- 

 tion of females that was obtained in the different lots varied 

 directly as the temperature at which the eggs were fertilized ; 

 relatively fewer females developing as the temperature of the 

 water was lowered. The decrease in the percentage of females 

 was so slight in the various cases, however, that I do not think it 

 can have much significance, particularly as there were so few indi- 

 viduals in the lots at the extremes of the series. Had the number 

 of individuals that metamorphosed been the same in every lot, 

 practically the same sex-ratio would doubtless have been obtained 

 for the entire series. 



For the purpose of comparison, and to show more conclusively 

 than is shown by the results of the series of experiments sum- 

 marized in Table 11. that temperature, acting at the time of the 

 fertilization of the &^^, does not determine sex in Bufo, the 

 results obtained in former experiments in which different batches 

 of eggs were laid in water with a known temperature are brought 

 together in Table III. 



Table III. 



