Precocious physical development occurs as a somewhat rare variation. W. Roger Williams ("Precocious Sexual Development with Abstracts of over One Hundred Cases," _British Gynæcological Journal_, May, 1902) has furnished an important contribution to the knowledge of this anomaly which is much commoner in girls than in boys. Roger Williams's cases include only twenty boys to eighty girls, and precocity is not only more frequent but more pronounced in girls, who have been known to conceive at eight, while thirteen is stated to be the earliest age at which boys have proved able to beget children. This, it may be remarked, is also the earliest age at which spermatozoa are found in the seminal fluid of boys; before that age the ejaculations contain no spermatozoa, and, as Fürbringer and Moll have found, they may even be absent at sixteen, or later. In female children precocious sexual development is less commonly associated with general increase of bodily development than in boys. (An individual case of early sexual development in a girl of five has been completely described and figured in the _Zeitschrift für Ethnologie_, 1896, Heft 4, p. 262.) Precocious sexual impulses are generally vague, occasional, and more or less innocent. A case of rare and pronounced character, in which a child, a boy, from the age of two had been sexually attracted to girls and women, and directed all his thoughts and actions to sexual attempts on them, has been described by Herbert Rich, of Detroit (_Alienist and Neurologist_, Nov., 1905). General evidence from the literature of the subject as to sexual precocity, its frequency and significance, has been brought together by L.M. Terman ("A Study in Precocity," _American Journal Psychology_, April, 1905).