Elementary text-book of zoology, general part and special part: protozoa to insecta . elementarytextbo00clau Year: 1892 AMBULACRAL APPENDAGES. ALIMENTARY CANAL, 275 all cases serve for locomotion. In addition to the ambiilacral feet, great tentacle-like tubes may be present as appendages of the water- vascular system; the circle of tentacles round tlie mouth of IIolo- thurians (fig. 209) is composed of such appendages. V/e also find leaf-like appendages arranged over four or five-leaved rosette- shaped areas, forming the ambulacral gills of the Spatanyklea and Clypcasiridea (figs. 207 and 208
Elementary text-book of zoology, general part and special part: protozoa to insecta . elementarytextbo00clau Year: 1892 AMBULACRAL APPENDAGES. ALIMENTARY CANAL, 275 all cases serve for locomotion. In addition to the ambiilacral feet, great tentacle-like tubes may be present as appendages of the water- vascular system; the circle of tentacles round tlie mouth of IIolo- thurians (fig. 209) is composed of such appendages. V/e also find leaf-like appendages arranged over four or five-leaved rosette- shaped areas, forming the ambulacral gills of the Spatanyklea and Clypcasiridea (figs. 207 and 208). The irregular Sea-urchius all possess in addition ambulacral feet upon the ventral surface. These are in the Cly- peastridea almost mi- croscopic in size; they are very numerous, and are arranged in branched rows or are irregularly distributed over the surface. The Echlnodermata possess an alimentary canal distinct from the body cavity; it can be divided into three parts—oesopha- gus, stomach, and rectum. The anus is placed usually at the centre of the apical pole, rarely in an inter- radius on the venti-al side. The intestine may, however, end blindly, as for example in all the Ojjhiwidce and Euryalidce, also in the genera Astero- pecten, Ctenodiscus, and Luidia, which have no anus. The mouth Fig. 219.—Holothur'a lululosa, opened longi inliually (after M. Edwards). O, Mouth in the midst of the tentacles (TJ ; X», digestive canal; Sc, stone canal; P, Polian vesicle ; Sg, circular vessel of the water-vascular sj'stem ; Ov, ovaries; Ag, ambulacral vessel; M, 'onja;itudinal muscles; Gf, vessel tr the intestine; CI, cloaca; Wl, respiratory trees.
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