STUDIES ON SEX-DETERMINATION IN AMPHIBIANS. 223 



used in making the solutions. Two strengths of each substance 

 were used; a .01 per cent, solution and a .0025 per cent, solution. 



In each case eggs and spermatozoa were placed together in 

 the solution and left for one half hour; the dish containing them 

 being kept in constant motion during this time. As the experi- 

 ment was carried out, therefore, the solutions might have acted 

 on the eggs alone, on the sperm alone, or on both eggs and sperm. 

 After remaining in the solution the given length of time, the 

 eggs were washed in several changes of fresh water and placed 

 in the dishes in which they were to continue their development. 

 The percentage of eggs that failed to develop was about the same 

 in the lots subjected to the action of the acid solutions as where 

 alkaline solutions had been employed; and was greater, as one 

 would expect, where the stronger solutions had been used. It is 

 not possible to say whether the failure of so many of the eggs 

 to segment is to be attributed to the injurious action of the solu- 

 tions on the eggs, or whether a large proportion of the spermato- 

 zoa were rendered incapable of fertilizing the eggs. 



For these investigations the eggs of two different females 

 (a and &) were used. Female a was the one from which the eggs 

 were taken that were used in the experiments summarized in 

 Table III., and the control for the former experiments also serves 

 as control for these. Eggs from female b were used for the study 

 of the influence of the spermatozoan on the determination of sex 

 in Bufo, and also for the experiments in which eggs wire subjected 

 to the action of salt and of sugar solutions before fertilization 

 (Table IV.). In the present case eggs from female b were fer- 

 tilized with spermatozoa from both testicles of the male desig- 

 nated as no. i in the former investigation (Table II.). The 

 percentage of females that serves as a control in this case was 

 obtained by taking the percentage of females in the total number 

 of individuals in the former experiments that developed from 

 the eggs that were fertilized with spermatozoa from male I. 

 Only the stronger solutions were used on the eggs taken from 

 female b. 



The sex ratios obtained in the various lots of individuals 

 derived from eggs that were fertilized in acid solutions are indi- 

 cated in Table VI. 



