Moreover, the results of experimental research clearly indicate that
we shall never possess the means by which a mother may control the
sex of her child. In the main laboratory investigations have sought
to answer two questions. First, at what time is the sex of the
offspring determined? and, second, what accounts for the origin of a
male in one instance and of a female in another? The study of these
problems has been carried on chiefly in connection with insects,
worms, and fowl; but as yet insurmountable difficulties have
prevented similar investigations in higher animals. For this reason,
it is not without the greatest caution that results thus far obtained
may be assumed to apply to man.

Sufficient facts, however, have been collected to admit no doubt
regarding the answer to the first question. In most animals it is
definitely known that the sex of the offspring has been fixed when
the male cell enters the female cell, in other words, at the instant
the ovum is fertilized. Excellent reasons exist for believing that
human beings conform to this rule, and that the sex of the child is
unalterably determined at the moment conception occurs. Consequently,
any attempt to influence it after that event must prove futile.

For the present, the second question cannot be answered with equal
assurance. More than five hundred theories have been offered to
explain the relation of sex; nearly all of them have no reasonable
foundation and are only of historical interest. The view that girls
are derived from the right ovary, boys from the left, has long since
been disproven, and deserves mention merely because the laity still
believe it. Happily, during the last few years, observations and
experiments have been made which greatly advance our knowledge of the
subject and give promise of an early solution of the problem. The