If an attempt be made (Richarz) to explain the different facts observed, in accordance with the theory in question, no insuperable contradictions will be met with. The general excess of male births, their corresponding increase during the loss of many men in war (a loss of distinctly stronger men), the high proportion of male births in the case of mothers who produce their first-born at a comparatively late age, the same high proportion where polygamy prevails, and, further, the diminution of male births in the case of unmarried mothers, which should not be overlooked,--all these phenomena are declared to be in accord with Richarz’s views. We will proceed here to give a brief sketch of Richarz’s opinion. Ribot powerfully supports it in every particular from his own experience and from historical data. The primary impulse upon which the whole process of generation depends lies in the organs of the mother. Here lies also the substratum in which is, as it were, the center of gravity of the special generative process. The function of the male sex is to evoke from the feminine substratum an organism, or, more strictly speaking, to occasion a change in the germ. If the mother’s generative capacity reaches the highest point the result is a boy, who in external appearance resembles his mother. If, however, it happens that the forces which act in the mother are inferior to those of the father, the infant will be a female. She will resemble her father, and will also inherit her father’s temperament. Sex is not a transmissible attribute inherited directly from the parents. Personal appearance and other characteristics will on the whole correspond rather more with one of the parents than with the other. Yet in every case the influence of the other parent will make itself felt, and will in many respects exercise a modifying influence over external appearance and other characteristics. These views have been attacked by Roth, who declares himself against Richarz’s hypotheses. His objections are contained in a work entitled ‘The Phenomena of Heredity’ (_Ueber die Thatsachen der Vererbung_). He directly attacks the theory of cross-heredity of sex, and according to his theory claims for each parent an equal share in the formation of the future individual, at least in the earliest stages. Fecundation, according to Roth, would at once be effective in determining the sex of the future individual. We shall have occasion hereafter to speak of the observations which Mayerhofer has made upon the origin of sex. Here we shall mention only a single fact. This is a result of his experiments with animals, and seems to have a relation to the theory of cross-heredity of sex. Ewes impregnated by a powerful ram bear more males than females, so long as the ram is in possession of his full forces. After a time the ram has to perform his functions repeatedly during a few days, as great numbers of the ewes are rutting. The fatigued or exhausted ram then begets only females.