SPECIAL CASES OF SEX-INHERITANCE . 229 



his general hypothesis of nucleo-plasm relation. He 

 holds, for instance, that sex may be determined by the 

 relation between the size of the nucleus and the proto- 

 plasm of the cell. As the value of the evidence has 

 been seriously called into question in general, and as 

 there is practically no evidence of any weight in its favor 

 in the present case, I shall not dwell further on the 

 question here. But the excessively high male ratio is 

 evident and positive. How to explain it is difficult 

 to say. It is just possible, I think, that delay may have 

 injured the egg to such an extent that the sperm may 

 start the development but fail to fuse with the egg 

 nucleus. Under these circumstances there is the possi- 

 bility that all the frogs would be males. 



Miss King has also carried out extensive sets of ex- 

 periments with the common toad. She has studied the 

 eggs and the sperm under many different conditions, such 

 as presence of salt solutions, acids, sugar solutions, cold, 

 and heat. Her results are important, but their inter- 

 pretation is uncertain. In sugar solutions and in dry 

 fertilization the males decreased, in the latter from 

 114.10 to 29.41 per 100 ??. The normal sex ratio for 

 the toad is 90 $ to 100 ? . Whether the solutions have in 

 any sense affected the determination of sex, or acted to 

 favor one class of sperm at the expense of the other re- 

 mains to be shown, as Miss King herself frankly admits. 



In the case of man there are extensive statistics 

 concerning the birth rate. The accompanying tables 

 give some of the results. There are in all parts of the 

 world more males born than females. The excessively 

 high ratios reported from the Balkans (not given here) 

 may be explained on psychological grounds, as failure 



