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This work aims to clarify whether the pars distalis of the pituitary gland plays an indispensable role in heat-induced sex transformation from ovaries to testes. Intact and hypophysectomized tadpoles of the sex semidifferentiated race of Rana catesbeiana were reared in water at 20°C as controls and at 30°C as experimentals. The results showed that ovaries of the hypophysectomized tadpoles were sex transformed to testes completely or partially both at 20°C and 30°C, demonstrating independence of spontaneous and heatinduced sex transformation on the pars distalis. The findings were in agreement with our previous work that sex transformation of ovaries was independent of thyroid function, and also with reports from other laboratories that sex transformation induced with sex hormones likewise occurred in hypophysectomized as well as in intact tadpoles. Therefore, it is believed that the pars distalis is not essential for sex transformation and that heat delivers, without mediation through endocrine glands, a direct and destructive assault on the cortex of the gonad which elicits the antagonistic activity of the medulla, resulting in sex transformation.

Effect of Hypophysectomy on Sex Transformation in Frog Tadpoles