An annelid proprioceptor

Abstract

THE structure of the worm Harmothoe is in most respects typical of errant polychaites; it has well developed parapodia armed with bristles and provided with dorsal and ventral cirri, but on the dorsal side of the worm are scales (elytrai) which most polychaites do not have. Methylene blue preparations reveal the following types of sense organs: (a) numerous small bipolar cells of ventral cirri and of the elytrai; (b) a group of bipolar cell bodies with branched endings in the region where the bristles emerge from the parapodial cuticle; (c) numerous and scattered bipolar cells beneath the cuticle particularly on the ventral side of the body; (d) bipolar cells of the elytrai; (e) concentrated groups of bipolar cells standing at right-angles to the surface in the thickness of the epithelium; (j) several bipolar cells each with a long dendrite stretched diagonally across the ventral side of every parapodium. Types (a), (c) and (e) are described by Smith1