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 of 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 determined 
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 1co. In the Almanach of Gotha there are recorded 
105 males to 100 females; but amongst Russian peasants there 
