The Excitation of Nematocysts

Abstract

ABSTRACT Though an enormous amount of work has been done on nematocysts, the problem of how they are discharged remains unsolved. There are really two separate problems. First, what is the natural stimulus which excites the cnidoblast; second, what is the physical mechanism by which the nematocyst itself discharges? There is more work on the mechanics of discharge than on any other aspect of the problem, but it still awaits a satisfactory solution. As Graham (1938) points out, most of the work is remarkable for the chemical violence of the reagents used. Reactions to strong acids and alkalis, or to gross changes in osmotic or mechanical pressure can only throw an indirect light on the physical nature of the nematocysts’ diècharge. But it is not intended to discuss here the mechanics of discharge. Existing work has been reviewed by Weill (1934). This essay concerns the primary question of what is the effective stimulus to the cnidoblast, a problem to which much less work had been devoted.