HERMAPHRODITE is the term used to describe an indi vidual which elaborates both male and female germ-cells, syn chronously or at different times. Non-functional hermaphrodit ism (the condition in which, though both male and female germ cells are elaborated transiently or permanently, only one kind is functional), exists in three forms. In accessory hermaphroditism there is in addition to the testis a rudimentary ovary which, how ever, does not produce ova, e.g., Bidder's organ in the male toad, and the ovary in the male of the stone-fly Perla marginata. In accidental hermaphroditism ova occur sporadically in the testis and spermatic tissues in the ovary. The condition is not uncom mon among the Crustacea : it is of importance in that it shows that a primordial germ-cell can, under different circumstances, develop into a spermatozoon or into an ovum. In teratological hermaphroditism, commonly encountered in birds and mammals, the reproductive system consists of an intimate mixture of male and female structures. Its nature is as yet not understood.
Functional hermaphroditism, the condition in which both male and female gametes are produced by one and the same individual, both kinds being functional, also exists in three forms. In uni sexual monoecism a genetic female (or male) develops at certain times spermatozoa in the ovary (or ova in the testis), and the individual previously functioning as a female (male) now func tions as a male (female), e.g., Angiostomurn nigrovenosum and other nematodes and probably the hermaphrodite molluscs. In other words, one sex has become hermaphroditic. Gynomo noecism, in which the female temporarily produces sperm, is more common than andromonoecism. In consecutive monoecism every individual is first a male and then a female (or less com monly, first a female and then a male). Genetically the organisms are either males or neutrals. The condition is associated with parasitism and sedentary modes of life, e.g., Danalia, one of the Liriopsidae, which is parasitic on a parasitic Rhizocephalan Crus tacean. In spatial monoecism both male and female reproductive organs are present and the condition is a real functional hermaph roditism, e.g. certain Oligochaetes, Cestoda, Trematoda. The genetic basis of the condition is unknown. (See SEX; also