[CHAPTER II]
According to St. Hilaire, the male sex is more common in the case of scantily nourished (and therefore weakly) animals. Giron de Buzareingues says that the same is sometimes the case with domesticated mammalia. Martegoute has found that the sheep which bear female offspring are, on the average, of a heavier weight. Furriers have remarked that in fruitful regions more furs of female animals are always to be had than in unfruitful districts. It would follow from this that better nourishment assists the production of females.
This observation seems, however, to be concordant with the general practice of farmers, according to which it is usual to keep a greater number of the females of the domesticated animals, on account of their utility. The males are kept only in such numbers as may be absolutely necessary for breeding purposes, or for stronger beasts of burden. The surplus is, by means of trade, disposed of in other regions. In consequence, in poor unfruitful districts, the number of males is pretty nearly the same as in fruitful regions, the actual requisite number being in both cases about the same. The females, on the contrary, can be much better kept in fruitful districts, where there are rich and fertile meadows and better fodder, than in the poor regions. In the latter the females are consequently rarer.
Wilkens attempted to apply diet to the production of sex in the domesticated mammalia, and laid down the following principles: The food must be of influence upon the embryo in the mother’s womb, and the better nourishment favors the female, the worse the male sex.
We have already mentioned the views of Robin and Born respecting the influence of food.
Düsing turned his attention to the effect of diet upon horses, with a view to the development of sex.
The state of nutrition of the parents would have an influence upon the development of the embryo. In this case, also, the better condition produced females, the worse males.
According to Düsing, if the mother was well nourished, old semen operating upon a young ovum would produce a majority of female offspring. On the other hand, if the mother was insufficiently fed, young semen operating upon an old ovum would produce a majority of male individuals.
According to Wappaens, richer or poorer nourishment in years of different fruitfulness in Sweden has no effect upon the prevalence of one or the other sex.