1) WhenHydra viridis is subjected for a sufficient length of time to a low temperature which is then followed by a period of higher temperature and starvation it develops testes and eggs. 2) Hydras that are not first subjected to a low temperature will not develop reproductive organs when starved. 3) Hydra must be subjected to a low temperature for a longer period of time in order to produce eggs than to produce testes. 4) An abundance of food following the period of low temperature suppresses the formation of testes and eggs. 5) AHydra which produces testes and eggs can produce buds which also can develop testes and eggs. 6) Large individuals produce both testes and eggs but small individuals produce only testes. 7) Low temperature followed by a higher temperature causes rapid bud formation irrespective of the food conditions.