The nature of cnidarian desmocytes.

The electron microscope reveals that the cnidarian desmocyte is an ectodermal cell which forms acidophil protein tonofibrillae intracellularly. One end of the cell is bound to mesogleal fibrils; the other becomes embedded in the thickening cuticle. The bundle of tonofibrillae later becomes rivet-shaped and the cell dies, but still the mesoglea remains bound to the cuticle by means of the rivet. The histochemistry and formation of the rivet as well as the comparative cytology of cnidarian desmocytes are discussed.