Cobalt Staining Of Actinia Equina Nematocysts

Nematocysts of Actinia equina are stained black by incubation in 2% CoCl₂ followed by an aqueous wash and H₂S treatment. They are also stained positively by morin. Nematocysts isolated from the acrorhage were found to have a high concentration of calcium of which only 30% was “free.' It is suggested that the high concentration of calcium in the nematocysts accounts for their staining by cobalt and morin. Cobalt staining offers a simple and effective technique for investigation of nematocysts.