CHAPTER XXXII 
SEX DETERMINATION 
VARIOUS THEORIES OF SEX DETERMINATION 
H. H. NEwMan 
In earlier chapters it has been necessary to introduce a few neces- 
sary facts about sex determination and sex-linked heredity. The 
mechanism of sex determination has been clearly described and illus- 
trated for Drosophila (pp. 411 ff.), and the close connection that exists 
between sex-linked heredity and sex determination has been shown in 
chapters xxxi and xxxii. A more detailed consideration of sex deter- 
mination and sex differentiation is now to come. 
The question as to what determines whether an animal shall be a 
male or a female is a very ancient one, and it is only during the present 
century that we have solved the puzzle. 
A great many theories of sex determination have been proposed, 
some of which are as follows: 
a) Hippocrates and some subsequent theorists believed that the 
sex of the offspring depended on the relative vigor of the parents, the 
more vigorous parent giving his or her sex to the offspring. 
b) Thury thought that the sex of the offspring depended on the 
degree of ripeness of the ovum at the time of fertilization. 
c) Various writers claim that statistics show that germ cells from 
the right ovary produce males and those from the left ovary females. 
d) The nutrition theory.—The egg is a much more highly nourished 
cell than the spermatozoén, and the idea seems natural that high 
degrees of nourishment of the mother produce female offspring and 
lower degrees of nourishment male offspring. Professor Schenk of 
Vienna gained a huge reputation by controlling the diet of certain 
royal prospective mothers and predicting the sex of the offspring 
accordingly. He was correct in his predictions several times, but his 
success was short-lived. His early predictions were merely lucky, 
just as one might be who could guess heads or tails correctly several 
times in succession. 
Some color is lent to the nutrition hypothesis by the fact, if it is a 
fact, that after war or famine, when the nutrition of mothers has been 
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