Several investigators observed in the late 1920' s that in some species of birds and mammals a number of secondary sexual characteristics, including color, seemed to be dependent on hormonal factors and not at all on the genetic sex of the individual. This led to the enunciation of a theory of "equipotentiality" which assumed that male and female tissues were identical in their reactions, particularly to the sex hormones (Lillie, 1927). Allen and Doisy (1923) were the first to suspect that the ovarian follicular hormone was an estrogenic agent in mammals. Allen et al. later (1924) found that a similar substance could be extracted from the follicular liquor in the ovary of the domestic hen (Gallus domesticus). Much research, mostly with domestic animals, followed these discoveries. The domestic fowl served as a popular subject. Since the color and shape of feathers seemed more sensitive to hormonal changes during their growth than other secondary sexual characters, they were studied at great length. As a consequence of this it was found that castrated male chickens showed little or no changes in feather color or shape; yet ovariectomized females acquired male plumage. The injection of ovarian extracts, however, feminized both intact and castrate males as well as ovar' iectomized females. Much emphasis was placed on the theory of equipotentiality; but as experimental work expanded into other avian species, it was found that other relations obtained. The European House Sparrow, Passer domesticus (Keck, 1934) and the Brewer Blackbird, Ez&zgus cyanocephulus (Danforth and Price, 193 5) did not respond to the estrogen theelin. The Black-headed Gull, Larus ridibundus (van Oordt and Junge, 1933) Es ambisexual, responding to both male and female hormones and the African Weaver Finch (PyrowzeZunu frunciscunu) has its plumage regulated by an hypophyseal hormone (Witschi, 1935,1936). Obviously then, genetic as well as hormonal factors must interact to produce these different effects. Previous studies of specific effects of genes in relation to their expressivity under estrogenic influence in Red Junglefowl, Callus gullus (Morejohn, 1953,1955) prompted the authors to investigate the nature of the difference in plumage between the sexes of Ring-necked Pheasants (Phasianus cokhicus). Three "off-colored" birds were noticed among normal-appearing cocks and hens in an incoming group of pheasants used in other experiments. The three birds were caught, examined, and identified as sex anomalies of one type or another. Two of the birds were colored like hens, and one was cock-colored. A review of the literature revealed that several types of so-called "sex anomalies" had been reported in Ring-necks and other pheasants. Some ' were called. hermaphrodites, others intersexes, and still others sex-inverts. From published descriptions and photomicrographs of internal organs it was difficult to decide in which of these categories to place the birds we had examined. Hermaphrodites were cock-feathered birds with spurs, c 101 1 THE COKDOR Fig. ...
