Ovulation and Oviposition in Anura

THE results of hypophysectomy and of injection of extracts show that the gonads of Amphibia are under the control of the anterior lobe of the pituitary (Wolfe, 1929; Hogben, 1930). Xenopus laevis does not exhibit any sexual activity in the laboratory. When appropriate nutritive and other conditions are fulfilled (Landgrebe, 1939), the ovaries are close to the threshold of ovulation at all seasons. Injection of gonadotropic extract then leads to ovulation and oviposition. If males in the same container receive the same treatment, clasping occurs and fertilized eggs result (Shapiro, 1936). In nature Xenopus does not shed simultaneously all the eggs which ripen in a season. Its habits of ovulation and oviposition are essentially similar to those of Urodeles. Rana, on the other hand, sheds simultaneously at the breeding season all the eggs which have ripened during the preceding year, and there is a rapid growth of oocytes which have not previously attained visible dimension^ about the time when ovulation begins. Injection of gonadotropic extracts causes hypertrophy of the ovaries and ovulation but rarely oviposition (Bellerby, 1933).