Neuromuscular transmission of excitation in invertebrates has been studied extensively by many investigators (cf. Bullock & Horridge, 1963). Miniature inhibitory junction potentials (m.i.j.p.s) and miniature excitatory junction potentials (m.e.j.p.s) could be recorded from the longitudinal layer of the somatic muscle in the earthworm. Field stimulation to the peripheral nerves elicited inhibito...