Is the maintenance of the human species similarly provided for? A detailed investigation of the male and female human reproductive organs shows that these contain parts of diverse origin. The apparatus contains portions of extremely ancient origin, and portions that have been acquired recently. The internal organs display traces of a remote hermaphroditism. In the male, there occur traces of the female apparatus, rudiments of the uterus and fallopian tubes. In the female, on the other hand, rudiments of the male structure persist. These traces date very far back in the history of the race, for they occur also in most other vertebrates. The facts seem to indicate that, at a very remote period, the ancestral vertebrates were hermaphrodite, and that they became divided into males and females only gradually, still retaining in each sex traces of the other sex. Such traces occur frequently, even in adult man, in the form of rudimentary organs (known as the organs of Weber, of Rosenmüller, and so forth). The rudiments not only are functionless but sometimes, as frequently happens with atrophied structures, form the starting-point of monstrous growths, or of tumours that interfere with health. Thus the hypertrophy of a part of the male prostate gland (the organ of Weber) brings about the formation of a _uterus masculinus_, and so produces a sort of abnormal hermaphroditism. The rudimentary organs in the male reproductive apparatus frequently are the starting-points of hydatid cysts. In the female, cysts such as those of the _parovaria_ are produced by the proliferation of rudimentary structures. These, although usually benign, not infrequently become malignant. Lawson Tait,[85] a celebrated English surgeon, has published a case of this kind. He removed from a young woman a parovarian cyst that was apparently benign, but in six weeks symptoms of cancer arose, and the patient died of cancer in three months. A comparison of the rudimentary organs in the human reproductive apparatus with those in the similar structures of lower animals, shows that many relics have degenerated further in man than in other animals. Thus the duct of the embryonic kidney (known as the Wolffian body) is of rare occurrence in adult man, although it is retained throughout life in the case of some herbivorous animals, in which it is known as Gaertner’s duct. There are, however, many rudimentary organs in the human reproductive apparatus, organs that are always useless and not infrequently more or less harmful to health and life. Alongside organs which have been useless from time immemorial, the reproductive system of man possesses structures of recent acquisition. These deserve special attention, as it might have been supposed that in them would have been found special instances of adaptation to the reproductive function.