HERMAPHRODITISM, the occurrence of both kinds of sexual glands in one and the same animal. The differentiation of the sexes begins with the polyps, when for the first time in the animal kingdom we meet with individ uals which are male and female. The lower plants and in the animal kingdom the sponges and Hydra (q.v.) are moncecious, that is, sexual cells occur in the same individual In the more highly specialized animals, the sexual glands exist in different individuals, and the form is said to he bisexual, or dicecious, as op posed to hermaphroditic forms.
True or Natural Hermaphroditism.— This is found in many flowering plants, in sponges, most cmlenterates, many worms, including the earthworm, many mollusks and in most barna cles, and this appears to be in relation with their more or less fixed mode of life. As a rule testes and ovaries occur in the same animal, but situated in different regions of the body, while in land snails there is a hermaphroditic gland which produces spermatozoa and eggs in the same follicle. Certain animals, or frogs, which are bisexual as adults, pass through an embryonic hermaphroditism. Normal herma
phroditism is very rare in insects and verte brates; in the latter only two cases are known, that is, a sea-perch (Serranus scriba) and the hagfish (Myxine).
Abnormal Hermaphroditism.— What in man is called hermaphroditism is a misnomer, as it arises from malformation of the external reproductive organs. In insects occurs lateral hermaphroditism in which one-half of the moth or butterfly, for example, is male and the other female. In some of these cases dissection has shown that only male or female sexual glands alone occur in an undeveloped condition. This is called gynandromorphis-ns. Abnormal her maphroditism sometimes occurs in fishes and batrachians where an ovary is found on one side and a testis on the other. It is curious that in a threadworm (Angiostomun) and in certain isopod crustacea (Cymothoida') the reproductive glands are first male, the same gland afterward producing eggs.