The electrical activity of the radial nerve in Diadema antillarum Philippi and certain other echinoids.

Electrophysiological studies in echinoderms are rare. In echinoids investigations have been made by Takahashi and Sandeman. The former used Diadema setosum, the latter Strongylocentrotus, Tripneustes and Toxopneustes. Takahashi gives a brief account of the electrical concomitant of the photic responses already described in detail by Millott and co-workers. Behavioural studies showed that the radial nerves had certain properties of a central nervous system, in particular that they functioned as centres for interaction between excitation and inhibition. The aim of this account is to show some of the electrical manifestations of such activity.