Page:Popular Science Monthly Volume 26.djvu/339

Rh to a scarcity of males, and in such a case more male larvæ than usual are produced; while early fertilization, which is a sign of the abundance of males, results, according to Huber, in an excess of female births.

Any influence which is equivalent to a lack of individuals of one sex acts, according to Düring, to produce an excess of births of that sex, although there may be an actual deficiency.

Thus, when the queen-bee is restrained by confinement, or by the lack of wings, from the nuptial flight, or when the seminal receptacle has been removed by accident or by an operation, or when the contained semen has been killed by frost or exhausted, only males are produced.

Something of the same kind has been observed in man, and the fact that a war, which carries most of the men away from their homes, is followed by an unusually great number of male births, has been re corded by many observers.

The second part of the paper, which will be found by far the most interesting to the scientific student, treats of those influences which act in the same way upon both parents, and the author's conclusion may be summarized as follows:

The power to regulate fertility according to the means of subsistence would be of use to the organism, and since the female has gradually acquired, through division of labor, the function of providing the material for the growth of the young, an excess of females is a condition of rapid multiplication. We might therefore expect, what we actually find to be the case, that organisms have gradually acquired, through natural selection, the power to produce an excess of females in time of plenty, and in a season of scarcity of food an excess of males.

I think, however, that careful examination of the evidence which Düring has brought together will show that he has stated his generalization in too narrow terms, and I think his facts will prove the following: A favorable environment causes an excess of female births, and an unfavorable environment an excess of male births.

It is true that abundance or scarcity of food is one of the most important elements of that whole which makes up the environment of an organism, and in most of the cases which Düring quotes it is the controlling factor; but he gives many cases, some of which will be noted further on, where a variation in other conditions of life has produced the same effect, causing an excess of male births when unfavorable, and an excess of female births when favorable.

In the case of man, the conditions of life are so much under control that it is difficult to state just what constitutes a favorable environment, but I think we may conclude that, as a general rule, an environment which produces a high birth-rate is favorable, and vice versa. Now, During gives many tables to show that, among mankind, the