STUDIES ON SEX-DETERMINATION IN AMPHIBIANS. 



39 



From a second lot of eggs laid in the laboratory on March 3 I, 

 1907, another 500 eggs (Lot B] were taken and divided into two 

 sets of 250 eggs each as in the previous experiment. These 

 eggs were placed under conditions similar to those of Lot A. 

 The tadpoles in this series behaved in all respects like those in 

 the first series as regards their rate of development and time of 

 metamorphosis. The following table summarizes the results 

 obtained with these two lots of eggs. 



TABLE IV. 



As shown in the above table the sex ratio of the individuals 

 used in these experiments differs considerably from the sex ratio 

 which is presumably normal for the species. The individuals of 

 Lot A, whether they had lived in warm water or in cold water, 

 produced an unusually large proportion of females ; in the one 

 case 69.84 per cent., in the other 61.58 per cent, of the individ- 

 uals in which sex was ascertained were females. The most 

 striking deviation from the apparent normal sex ratio is shown in 

 the individuals of Lot B. Here the number of females is only 

 23.07 per cent, in the case of the tadpoles that had been reared 

 in the warm water and 37.60 per cent, among the individuals 

 that were subjected to a temperature of 14-! 8 C. during the 

 course of their development. The results of these experiments 

 fail to support Hertwig's contention that a high temperature 

 acting during the course of the development of the tadpoles 

 favors the production of females, while a low temperature tends 

 to produce a relatively greater proportion of males. To be 

 sure one set of eggs (Lot A] developing at high tempera- 

 ture gave 69.84 per cent, of females which is a considerably 

 larger proportion of females than is found among young toads 

 under natural conditions ; but another set of eggs (Lot B] de- 

 veloping under exactly similar conditions produced but 23.07 per 



