A REVIEW OF THE BIOLOGY OF SEX- 
DETERMINATIONi 
SIDNEY I. KORNHAUSER 
1. PREVALENT IDEAS 
The mechanism of sex-determination has been a matter of 
speculation since time immemorial. Many erroneous and im- 
possible ideas remain even today in the mind of the layman. 
The speculations may be gathered in three groups according to 
whether belief is held (1) that the sex of the offspring is pre- 
determined in the egg, (2) that sex is determined at the time of 
fertilization, or (3) that sex is not determined until after the 
zygote has been formed. 
All of the older experiments on sex-determination were based 
on the third supposition. It was believed that by varying the 
nutrition of the developing embryo one sex or the opposite would 
result. This belief was even applied to human beings. In 
experiments upon tadpoles definite results were believed to have 
been attained, but we now know that the death rate in these 
experiments was so large that the results may be explained by a 
differential mortality. 
Others held that the age or vigor of the parent affected the 
sex ratio, the older or the more vigorous of the two parents 
tending to impress its sex upon the offspring. 
Another belief, and one still held by many, regards the fresh- 
ness or staleness of the egg as important. An egg shortly after 
ovulation tends to produce a female, while an egg which has 
remained in the oviduct some time would tend to produce a 
male. 
The idea that two types of eggs are formed is not altogether 
new. Thus, entirely without biological foundation, theories 
1 A lecture delivered before the Denison Scientific Association in October, 1921 . 
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