The Co-ordination of the Responses of Cerianthus (Coelenterata)

Abstract

1. The responses of Cerianthus membranaceus to electrical and mechanical stimulation are described. 2. The longitudinal muscle of the column ectoderm responds with a symmetrical contraction to a single shock from a condenser discharge applied anywhere on the animal. The response is independent of the strength of the stimulus above threshold and is co-ordinated by a through-conducting system which propagates an impulse at about 1.3 m./sec. followed by an absolute refractory period of 70 msec. at 21-23° C. 3. The strength-duration curve of the excitatory process, the relative refractory period curve and the curve of facilitation of contraction are given and compared with corresponding results from actinians. 4. Slow responses of the tentacles and column muscle are described. 5. The physiological observations are discussed in relation to the histological background. The conclusion that the physiological pathway cannot yet be histologically identified is discussed as part of the general problem of the analysis of the coelenterate nerve net.