This reciprocation on the part of the child of the heterosexual preferences of the parents undoubtedly plays a very large part in the development of normal heterosexuality: just how large is this part compared with that played by the instinctive heterosexual reactions of the child, it is difficult or impossible to say in the present state of our knowledge, since in any given case the two factors are apt to be very closely interrelated. The question is of interest because the relative influence of the two factors must, it would appear, largely determine the extent to which the direction of a child's sexual desires is dependent upon innate and upon environmental causes respectively. Should the direction of a child's object love toward persons of one sex rather than toward those of the other be largely determined by the manifestations of affection that the child receives, it would seem that the sexual inclinations of the parents must exert a great influence in the formation of the sexual character of their children, _e. g._ that marked heterosexuality in the parents would tend--through its effects on parental preferences and quite apart from any hereditary influences--to produce equally developed heterosexual inclinations in the children, whereas homosexually disposed parents would tend in a similar way to bring up homosexual children. If on the other hand, the direction of a child's object love depends chiefly upon innate instinctive factors, the sexual dispositions of the parents will play a much less important rôle in the mental history of the child and will be influential only in so far as they are directly inherited. The progress of psychological research, statistical and psycho-analytic--will, we may hope, cast much light upon this problem in the near future. [Sidenote: Homosexual and heterosexual development in girls]