SEX (OF, scxe, from Lat. sexus, secus, sex, from secure, to cut ; connected with OHG. saga, sega, Ger. Sage, AS saga, Eng. sac) (in ani mals). The capacity, in all but the lowest organ isms, of each individual producing either eggs or sperm cells (or both), i.e. germ cells which are either female or male. In the lowest or uni cellular animals, reproduction (q.v.) is by self division or by germs, which so far as we know are devoid of sexuality: such forms are said to be 'asexual.' The next' step, one suggesting sex ual reproduction, is the phenomenon of conjuga tion. In all animals from sponges to man re production is by male and female cells.
The ovary and testis are sexual glands (go nads), and may he regarded as the primary sexual organs. In nearly all animals, from the flatworms to man, there is a passage or outlet for the expulsion of the sexual products, and accessory organs for the dilution and expulsion of the seminal fluid, or for secreting the egg shell; also external appendages of less or greater complexity in those forms which pair; and egg laying organs, as the ovipositors of insects, brood-pouches, and different forms of uteri. Judg ing by the lowest forms, animals were probably at first hermaphroditic, growing out of a uni sexual. condition. Hermaphroditism is a condi tion in which both male and female organs are developed in the same individual. There are two kinds of hermaphroditism, the true and the spu rious; in the former the germ glands contain both male and female germ cells; in the latter the accessory organs are of an ambiguous char acter. Hermaphroditism is normal in some spe
cies and abnormal in others. Spurious her maphroditism is met with in all dicecious groups. In insects it has been repeatedly noticed. Thus one wing may have the male coloration and the one on the opposite side female coloration; or the anterior and posterior parts of thq animal may have opposite secondary sexual characters; or the sexual characters may be intermingled, or, more rarely, blended.
Among vertebrates abnormal hermaphroditism is rare. Fishes have, however, been described with an ovary on one side and a testis on the other, and birds have been repeatedly described with ambiguous secondary characters. These phenomena usually appear late in life, but they may occur in young birds, which are then usually sterile. A similar tendency to gain characters of opposite sex is seen in old persons, in whom the germ glands are no longer functional. Con cerning the interpretation of abnormal her maphroditism it may be said that at an early stage of development all animals are sexless, but their germ glands seem to possess the poten tiality of both sexes; typically, in dicecious or ganisms only one of these potentialities is real ized, but exceptionally both of them may be to a greater or less complete degree.