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1. The hemolytic activity of suberitine, a neurotoxic protein isolated from Suberites domuncula, has been examined. 2. The toxin has no phospholipase A activity. 3. The hemolytic activity of suberitine does not exhibit the induction period and is completely inhibited by sucrose. 4. A study of the effect of temperature on the rate of hemolysis shows that suberitine has two values of the critical thermal increment. The optimum pH for the hemolytic activity was 6.0. 5. There was a correlation between the hemolytic and toxic activity.

A new cytolysin has been isolated from the nematocysts of the jellyfish, Rhizostoma pulmo, and named rhizolysin. The hemolysin has a mol. wt of approximately 260,000, a sedimentation coefficient of 10.3 S and is rod-shaped with a calculated axial ratio of about 1:5. It appears to be composed of three subunits with a pI value near 7.8. Rhizolysin shows no phospholipase A activity, nor an induction period for its hemolytic activity and is completely inhibited by sucrose. The optimum pH was 6.75. The mu value calculated from the Arrhenius plot is 5940 cal/mole. Rhizolysin was inhibited by cholesterol and less by sphingomyelin.