A Through-conducting System co-ordinating the Protective Retraction of Alcyonium (Coelenterata)

Abstract

ALTHOUGH Milne-Edwards¹ and Hickson² report the existence of co-ordination between the polyps of Alcyonium, there is very little to be found in the literature beyond this bare record. Kassianov³ comes to the conclusion that there is no colonial nervous system in Alcyonium. Kukenthal⁴ states that in Alcyonaria the existence of a colonial nervous system must be inferred from (presumably mechanical) stimulation experiments. On the other hand, Hyman⁵ concludes that “in most Alcyonarians a nervous plexus seems to be absent from the wall of the anthocodia and the general coenenchyme”, except that “the occurrence of such a plexus in the coenenchymal epidermis has been verified for Veretillum and may be expected in many Pen-natulacea”.