Elementary text-book of zoology, tr Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote elementarytextbo01clau Year: 1892-1893 ALIMENTARY CAXAL. 55 vascular canals). In the larger Polyps (Anthozoa) a tube derived from an invagination of the oral disc projects into the central part of the digestive cavity. This is known as the stomach of the polyp, although it serves entirely for the introduction of food, and should be called rather the buccal or ccsophageal tube (fig. 43). Organs for the prehension of food are found even with this simple, dige
Elementary text-book of zoology, tr Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote elementarytextbo01clau Year: 1892-1893 ALIMENTARY CAXAL. 55 vascular canals). In the larger Polyps (Anthozoa) a tube derived from an invagination of the oral disc projects into the central part of the digestive cavity. This is known as the stomach of the polyp, although it serves entirely for the introduction of food, and should be called rather the buccal or ccsophageal tube (fig. 43). Organs for the prehension of food are found even with this simple, digestive system. For near the mouth are placed radially or bilate- rally arranged appendages or processes of the body, which set up FIG. 44.—Anrelia aurita seen from the oral surface. MA, the four oral tentacles with tho mouth in the centre ; Gk, genital folds; GH, opening of the genital pouches ; lik, mar- ginal bodies ; KG, radial canals ; T, tentacles at the margin of the disc. currents to convey small particles of food, or as tentacles seize foreign bodies and convey them to the mouth (Polyps, Medusae) (tig. 44). Such appendages serving for the capture of prey may also be placed further from the mouth (tentacles of Medusa;, Siphonophora, Ctenophora). When 1 he digestive cavity acquires a wall distinct from the body wall, and usually separated from the latter by the body cavity (ex- cepting the parenchymatous worms), it appears in the simplest cases as a blind tube, which may be either simple, bifurcated, or branched
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