STUDIES ON SEX-DETERMINATION IN AMPHIBIANS. 



2 9 



of one ovary may show a very different sex ratio from that of the 

 individuals produced from the eggs of the other ovary ; or it may 

 be that the eggs of one ovary produce only females and those of 

 the other ovary only males. The following experiments were 

 made to determine this point for Bnfo. On April 26, 1907, a 

 female which had just begun to deposit her eggs was killed by 

 pithing. The eggs in the right uterus were separated from those 

 in the left uterus and each set was artifically fertilized, sperm 

 from the same male being used for both lots. Six hundred eggs 

 from each ovary were taken for the purposes of the experiment 

 and placed in tanks of equal size. During the course of. their 

 development all of the tadpoles were subjected to similar con- 

 ditions of temperature and they received similar food. The sex 

 of the first 300 individuals in each set to undergo metamorphosis 

 was ascertained with the result shown in the following table : 



TABLE I. 



As shown in the above summary both lots of individuals gave 

 approximately the same sex ratio ; 56.33 per cent, of the indi- 

 viduals from the right ovary and 57.33 per cent, of those from 

 the left ovary being females. This proportion of females is some- 

 what higher than that obtained in the majority of the experiments 

 and seems to indicate that there is considerable normal variation 

 in the sex ratio of lots of eggs laid by different females. 



The above experiment was repeated with the eggs of another 

 toad in the spring of 1908. Owing to an accident, however, all 

 of the tadpoles developing from the eggs of the left ovary were 

 . killed and in only 140 of the individuals that had developed from 

 the eggs of the right ovary was sex ascertained. Of this number 

 64 individuals were males and 76, or 54.2 percent., were females. 



From the results obtained in these two experiments it is evident 

 that the sex ratio of the individuals produced from the eggs of 

 the right ovary is not materially different from that of the indi- 



