According to Professor Anne Fausto-Sterling, a biologist and gender theorist, if people ought to be classified in sexes at least five sexes rather than two, are needed. For some time medical investigators have recognized the concept of the intersexual body. But the standard medical literature uses the term intersex as a catch-all for three major subgroups with some mixture of male and female characteristics: the so-called true hermaphrodites (herms), who possess one testis and one ovary (the sperm- and egg-producing vessels, or gonads); the male pseudohermaphrodites (merms), who have testes and some aspects of the female genitalia but no ovaries; and the female pseudohermaphrodites (ferms), who have ovaries and some aspects of the male genitalia but lack testes.(Fausto-Sterling, Anne. The Five Sexes: Why Male and Female Are Not Enough. The Sciences March/April 1993, p. 20-24.)