FORM-REGULATION IN CERIANTHUS, IV

Publisher Website
Google Scholar
Abstract
I. Except when the animal is contracted or collapsed the body-wall of Cerianthus is subjected to a certain degree of tension in consequence of the fact that the water in the enteron is under pressure. 2. The inward current along the siphonoglyphe is probably the means by which the internal pressure is established and maintained. 3. When the body is distended the œsophagus, with the exception of the siphonoglyphe and perhaps some grooves and crevices, must be closed. 4. When contraction occurs the water first issues from the aboral pore (in other actinians from, the cinclides, etc.); then when the pressure is sufficiently reduced to permit it, the œageal walls are separated by muscular action and the remaining water issues from the mouth, often accompanied by mesenterial filaments. Thus the œsophageal is widely open only during extreme contraction. 5. The cilia on the entodermal surface of the body-wall produce a current flowing orally in each mesenterial chamber. The water passes from each chamber along the aboral face of the marginal tentacle, back on its oral face beneath the disc toward the stoniodæum, probably into and out of the labial tentacles and aborally along the stomodæum. In all probability cilia along the sides or margins of the mesenteries force it further aborally. 6. The internal water-pressure plays a large part in form-regulation in Cerianthus. The general pressure affects the rapidity of growth wherever it may be taking place and it is possible that the local pressure exerted on the body-wall by the currents passing orally in each mesenterial chamber is the formative stimulus for the marginal tentacles. 7. Regeneration of tentacles is impossible unless mesenteries are present. The reason suggested for this is that in the absence of mesenteries there is no localization of the currents corresponding to the intermesenterial chambers, and, moreover, the water being unconfined between mesenteries, exerts less pressure on the inrolled oral end than if mesenteries were present. 8. Local retardation or inhibition of tentacle-regeneration can be brought about by preventing distension of a part or parts of the oral region.

This publication has 0 references indexed in Scilit: