SPERMATOGENESIS IN NORMAL AND HYPOPHYSECTOMIZED FROGS (RANA TEMPORARIA), FOLLOWING GONADOTROPHIN ADMINISTRATION. III. INJECTION OF SUMMER PITUITARY EXTRACT INTO WINTER FROGS

Abstract

Hypophysectomized frogs were injd. in January with pituitary extract from frogs captured in the summer. The normal rate of spermatogenesis in summer is greater than that produced by summer-pituitary extract injd. into frogs in the winter. Pituitary extract from frogs captured in the winter had even less effect. The pituitary gonadotropin is less in winter than in summer; but frogs captured in the winter are also less sensitive to gonadotropin than in the summer. This seasonal variation in sensitivity of the testis tubules to pituitary gonadotropin is one of the factors responsible for seasonal fluctuations in spermatogenic activity.