THE rat hypophysis, when isolated from the diencephalon by transplantation to the kidney, can nevertheless liberate luteotrophin during the following week in sufficient amount to maintain luteal function (Desclin, 1950). Desclin's rats having been implanted in advance with pellets of stilbestrol, the liberation of luteotrophin was interpreted to be a direct effect of estrogen. Subsequently, however, Everett (1954) reported that functional corpora lutea are readily and consistently obtained in rats bearing hypophyseal autografts, without any stimulus other than may be inherent in transplantation itself.