Freud, S. (1905). Three essays on the theory of sexualitry. Standard Edition, 7, pp. 136-243. (cf. Gay, 1989, pp. 239-293)
This was Freud's first systematic published treatement of personality development in terms of "psychosexual" stages: oral, anal, phallic, latency, and genital.
In Chapter 2, Freud describes and distinguishes the child's groing repetoire of sexual/erotic "aims," "objects," and "zones."
As we all know, it is not until puberty that the sharp distinction is estblished between the masculinine and feminine characters. From that time on, this contrast has a more decisive influence than any other upon the shaping of human life. It is true that the masculine and feminine dispositions are already easily recognizable in childhood. The development of the inhibitions (shame, disgust, pity, etc.) takes place in little girls earlier than in boys; the tendency to sexual repression seems in general to be greater; and, where the component instincts of sexuality appear, they prefer the passive form (Gay, 1989, p. 287).