1.1. Kinetic studies of the prolytic (induction) phase of hemolysis caused by nematocyst venom isolated from the sea anemone Aiptasia pallida show that two sequential events occur which are affected by venom and Ca2+ concentrations respectively.2.2. The first event, called t1, is affected by venom concentration and has two sub-phases: a rapid one and slow one. These suggest a differential rate of binding of the two known lytic factors of venom.3.3. The seond phase, t2, involves the interaction of Ca2+ with a complex formed by the venom proteins bound to the red cell membrane.