210 HELEN DEAN KING. 



from eggs that were fertilized in the stronger solutions; but the 

 deviations of these percentages from that of the control are much 

 too small to be considered as significant, particularly as the lowest 

 proportion of females occurs in the lot in which the eggs has 

 been fertilized in I per cent, alcohol and not in the lot where 

 fertilization of the eggs took place in 2 per cent, alcohol. The 

 relatively high percentage of females (54.23) that is found where 

 the eggs had been fertilized in .5 per cent, alcohol is quite within 

 the limits of normal variations in the sex ratio of Bufo. For 

 previous studies in which the sex of nearly 10,000 young toads 

 was ascertained (King, '07, '09, '10) show that in any large lot 

 of individuals there is a slight excess of females, as a rule, the 

 proportion of females varying from 51 to 56 per cent. It is 

 evident from the sex ratios obtained in this series of experiments 

 that alcohol, in the strengths used and for the time it acted, has 

 no influence on the determination of sex in Bufo. 



The growth of the tadpoles that developed from the eggs that 

 were fertilized in 2 per cent, alcohol was greatly retarded. This 

 was not apparent during the first month after the experiment 

 was made, but became very noticeable later. At the time of 

 metamorphosis the majority of these tadpoles had a body length 

 of only 7-8 mm., although the body length of tadpoles of Bufo 

 at this period is normally 1 1-14 mm. During early development 

 the mortality among these individuals was comparatively slight, 

 being not more than 10 per cent. At the approach of meta- 

 morphosis the tadpoles, especially the smaller ones, began dying 

 in great numbers; and during the last week of June over fifty 

 of them died from no apparent cause. In no other series ot 

 experiments was the mortality among mature tadpoles anywhere 

 near as great as in this case. Alcohol, therefore, although acting 

 for only a short time at the fertilization period in but a 2 per cent, 

 solution, must have so affected many of the tadpoles that they 

 were rendered incapable of undergoing metamorphosis. All of 

 the tadpoles in this lot were normal as far as could be determined 

 without a microscopic examination of the various organs. None 

 of them showed defects in the central nervous system comparable 

 to those that Stockard ('09, ! io) has found can be induced in 

 embryos of fundulus by subjecting the fertilized egg to the action 



