Page:Popular Science Monthly Volume 64.djvu/110

106 as that of the egg itself. It will be observed that there is a certain catholicity in these conclusions at which Cuénot arrives, and in the present uncertain state of our knowledge on many important points it is probably wiser not to take too narrow a point of view in regard to what factors determine the sex of the individual.

Strasburger has recently arrived at a somewhat similar conclusion in regard to sex, basing his evidence mainly on certain observations and experiments in higher plants. He, too, concludes that the sex of the individual is determined in the egg, but he does not attempt to push the question further than this general statement.

Lenhossek has also discussed in a more popular form the question of the determination of sex, and he likewise urges that the sex of the individual is determined in the egg. His discussion of the relative number of males and females born in the human race is particularly instructive, but it would carry us too far here to discuss the conclusions at which he arrives.

Born has carried out a series of experiments with mice, and finds that the amount of food given to the parents produces no effect on the relative numbers of males and females born. He also finds that the age of the parents has no effect, nor has close interbreeding. He arrives at the conclusion that the sex of the higher animals and plants is determined in the egg.

In striking contrast to the general conclusions of Cuénot, Strasburger, Lenhossék, and of Born there are two more recent theories in which an attempt has been made to describe in detail how the sex of the individual may be determined in the egg. Beard's paper, published in 1902, may be said, in a sense, to take up the problem where it was left by Cuénot. He attempts to bring the problem of the differentiation of the sexes into connection with the recent work relating to the origin of the reproductive cells or gametes. Beard tries to show that there are not only two kinds of eggs, but also two kinds of spermatozoa that correspond to the two kinds of eggs. It is supposed by him, however, that the determination of sex rests entirely with the egg, and that the spermatozoa do not have any influence on sex-determination. It is assumed, moreover, that one of the two