Regenerating specimens of Chlorohydra viridissima (80 animals) were treated with dopamine or with his antagonist reserpine. Dopamine treatment resulted in accelerating regeneration and differentiation, in increasing the number of tentacles and cnidocytes, in inducing sexuality (22%), but above all in disturbing morphogenetic gradient (appearance of ectopic tentacles, cnidocytes and ovariotestes). Reserpine treatment resulted at least in dissociating tissues although some sign of regeneration is detected (f.i. tentacles and penducle pieces); never the hypostomal glands are regenerated.