1. The normal rhythm of sexual activity of both Xenopus and Rana is controlled by secretions of the anterior lobe pituitary. Progesterone and testosterone, as well as extracts of A.L.P., evoke ovulation in normal and hypophysectomized Xenopus. Injection of pregnancy urine into hypophysectomized Xenopus evokes enlargement of the reduced ovary and ovulation.
2. Serial injections of pituitary extracts and oestrin were without effect on the amount of egg jelly secreted.
3. Ovulation in Xenopus is immediately followed by oviposition. The eggs are carried by continuous ciliary tracts from the body cavity via the oviduct to the exterior. In Rana ovulation is not immediately followed by oviposition. The eggs accumulate in the lower third of the oviduct and are expelled en masse.
4. Experiments on extirpation of endocrines and the injection of appropriate extracts, together with the responses to pithing and electrical stimulation, lead to the conclusion that oviposition in Rana is probably under nervous not humoral control. The muscular and skeletal mechanism involved in the retention and extrusion of eggs in Rana is described.