Gametogenesis in the Genus Hydra

This paper comments on the induction of gametogenesis, on microscopicaland electronmicroscopical aspects of spermatogenesis and oogenesisand on fertilization in the genus Hydra. Spermiogenesis doesnot present any peculiarities. The ripe sperm contains no detectableacrosoinc. Egg-formation involves phagocytosis of entire oogoniaby growing oocytes. Several oocytes merge to a single oocyte,in which one nucleus becomes the germinal vesicle. The egg shellis formed only when the egg is fertilized. Various factors suchas the synchronization of gametogenesis, the length of sexualperiods, continuous release of sperm and the long life spanof sperm are considered to guarantee the fertilization of theeggs.