The apex of the cnidocyte with its cnidocil apparatus projects from the surface of the tentacle, while the basal pole, embedded in the ectoderm of the cnidosac, is inserted into the mesoglea by its basal stalk and basal pad of the fibrillar system (Cormier and Hessinger, 1980).
These changes were accompanied by the transformation of the knob surfaces (the number of cnidocils decreased and the number of discharged tubes increased, Fig.