nematocyst (nema to sist)

[ IMG:content-1291.png:[blocks in formation] Tentacle and Nematocysts of Athorybia . 1, tentacle, with A , peduncle; B , involucrum of C , the sacculus, with D , its filaments; d , ectoderm; e, endoderm 1,5, f, nematocysts; 2, two separate nematocysts, enlarged, the lower one a , with its filament c , projected from the sheath b . peculiar to cœlenterates, as jellyfishes, by means of which they sting. See cuts under cnida, Actinozoa, and Willsia.