STUDIES ON SEX-DETERMINATION IN AMPHIBIANS. 



therefore, a difference of about 17 C. in the temperature of the 

 water in which these two sets of eggs were laid. The eggs of 

 each lot, several thousand in number, were put in a large cement 

 tank supplied with running water and containing plenty of food. 

 The individuals in Lot C developed somewhat more rapidly than 

 those in Lot D and they began their metamorphosis sooner. 

 The experiment had to be discontinued on July 7, although a 

 number of individuals in each set had not yet reached a stage of 

 development when it would be possible to ascertain their sex. 

 The results of the experiment, tabulated according to the weeks 

 when the individuals died or completed their metamorphosis, is 

 given in the following summary. 



TABLE V. 



As shown in the above table the sex was ascertained of 2,178 

 of the individuals that developed from the eggs laid in warm 

 water. Of this number 1,225, or 56.24 per cent., were females, 

 thus giving a sex ratio for Lot C that is little, if any, higher than 

 that which is apparently normal for the species. The results of 

 this part of the experiment, therefore, do not seem to favor the 

 suggestion that a high temperature acting on the eggs at the 

 time of their fertilization tends to produce a relatively greater 

 number of females. There is the possibility, however, that this 

 negative result may be due to the fact that in making the experi- 

 ment a higher temperature was used than that which is the 

 optimum for the production of the greatest number of females and 

 that many more females would have developed had the eggs been 

 fertilized in water with a temperature but slightly higher than 

 that used in the former experiment with Lot A. 



