Abstract
1. Development of the ovaries of immature gold-fishes and red crucians, about 10 months of age, was accelerated by administration of gonadotropin (manufactured by Teikoku-zôkiyaku Kenkyusho) as well as frog or cattle anterior-pituitary suspensions. Some of the treated fishes spawned by mating with males after the administration.
2. The ovulation was accelerated by injection of several kinds of gonadotropic substances into female gold-fishes with full-grown ovaries. By mating, spawning occurred 1-3 days after injection of more than 4 frog or fowl pituitary glands, 100 mg. of dried cattle anterior pituitary glands or 150 RU of gonadotropin. When the injected females were not mated, the ovulation was weaker than that in the mated females, though their ovaries were affected and ovulated some completely or partly ripened eggs by injection of nearly the same amount of the gonadotropic substances.
3. The proportion of hatched larvae to artificially fertilized eggs was nearly the same between the ovulation under natural conditions and the artificial one which was accelerated with gonadotropic substances. It was about 80% in most cases.
4. While the breeding season of the gold-fish is April to July, one female reared at high temperature and under prolonged illumination laid eggs on March 3. Another female which had been injected with gonadotropic substances for a long time ovulated ripe eggs on September 13.
