We have to admit, however, that, in the opinion of the latest physiologists of sex, such as Castle, Heape, and Marshall, each sex contains the latent characters of the other or recessive sex. Each sex is latent in the other, and each, as it contains the characters of both sexes (and can transmit those of the recessive sex) is latently hermaphrodite. A homosexual tendency may thus be regarded as simply the psychical manifestation of special characters of the recessive sex, susceptible of being evolved under changed circumstances, such as may occur near puberty, and associated with changed metabolism.[128] William James (_Principles of Psychology_, vol. ii, p. 439) considered inversion "a kind of sexual appetite of which very likely most men possess the germinal possibility." Conolly Norman (Article "Sexual Perversion," Tuke's _Dictionary of Psychological Medicine_) also stated that "the sexual passion, at its first appearance, is always indefinite, and is very easily turned in a wrong direction," and he apparently accounted for inversion by this fact, and by the precocity of neurotics. Obici and Marchesini (_Le 'Amicizie' di collegio_, p. 126) refer to the indeterminate character of the sexual feelings when they first begin to develop. A correspondent believes that sexual feelings are undifferentiated in the early years about puberty, but at the same time considers that school life is to some extent responsible; "the holidays," he adds, "are sufficiently long to counteract it, however, provided the boy has sisters and they have friends; the change from school fare and work to home naturally results in a greater surplus of nerve-force, and I think most boys 'fool about' with servants or their sisters' friends." Moll (_Konträre Sexualempfindung_, 1889, pp. 6 and 356) does not think it proved that a stage of undifferentiated sexual feeling always occurs, although we have to recognize that it is of frequent occurrence. In his later work (1909, _Das Sexualleben des Kindes_, English translation, _The Sexual Life of the Child_, ch. iv), Moll remains of the same opinion that a homosexual tendency is very frequent in normal children, whose later development is quite normal; it begins between the ages of 7 and 10 (or even at 5) and may last to 20.