384 Experimental Zoology 



whether female or male eggs develop, assuming both kinds 

 to be present. As yet this point is unsettled. If Maupas's con- 

 clusion is correct, that the male eggs and the winter eggs are 

 the same, fertilization or its absence determining their fate, 

 it would seem that the same external conditions that produce 

 a winter egg produce its potentially equivalent male egg. In 

 Simocephalus lack of food causes either the male or the winter 

 egg to develop. If Weismann's statement is correct, that the 

 parthenogenetic egg and the winter egg come from different 

 parts of the ovary, it may prove that the male egg and the winter 

 egg are here also the same. This question needs, however, fur- 

 ther examination. 



Supposed Influence oj Nourishment in Determining Sex in 

 Man and Other Mammals 



In the cases so far examined the eggs are laid immediately 

 after fertilization, so that if their sex were not already determined 

 by the parent, no further chance for such an influence exists. 

 In man and in other mammals the embryo develops in the uterus of 

 the parent, and the opportunity is afforded of influencing the sex, 

 if such were possible, by the condition of nutrition of the parent. 

 It has often been claimed that the sex of the child is deteraiined 

 in this way, and as often denied. The method employed in this 

 case is to examine the statistics giving the proportion of males 

 and females born of parents living under supposed favorable 

 and unfavorable conditions of nutrition. It has been claimed 

 that more boys are born in the poorer classes and more girls in 

 the richer classes ; but at best the differences on which these state- 

 ments rest are small, and other statistics seem to give a contra- 

 dictory result. 



In support of the view that the conditions of nourishment 

 affect the proportion of the sexes, the following data have been 

 appealed to. In France the proportion of male to female births 

 is for the upper classes as 104.5 to 100, and for the lower classes 

 as 115 to 100. In the Almanach of Gotha there are recorded 

 105 males to 100 females; but amongst Russian peasants there 



