. Outlines of zoology. Zoology. 238 ECHINODERMA. this is certainly the main function of ten which lie near the mouth. Alimentary Canal. The alimentary canal passes through Aristotle's lantern, and the intestinal portion lies in two and a half coils around the inside of the shell to which it is moored by mesenteries. It contains fine gravel, sand, and some organic debris. It ends near the centre of the apical disc, whence the pedi- cellariffi have been seen removing the fseces, Accompanying the first coil of the gut is a canal or " siphon," which opens into the gut at both ends. Accor
. Outlines of zoology. Zoology. 238 ECHINODERMA. this is certainly the main function of ten which lie near the mouth. Alimentary Canal. The alimentary canal passes through Aristotle's lantern, and the intestinal portion lies in two and a half coils around the inside of the shell to which it is moored by mesenteries. It contains fine gravel, sand, and some organic debris. It ends near the centre of the apical disc, whence the pedi- cellariffi have been seen removing the fseces, Accompanying the first coil of the gut is a canal or " siphon," which opens into the gut at both ends. Accord- ing to Cuenot, a current of water traverses this tube, which thus, by reason of its thin walls, carries oxygen to the cor-. Fio. 77.—Ventral half of Sea Urchin. (From Carus, after ) o\ Aristotle's lantern in centre; oc^ Oisophtigus ; /, intestine; 6", intestinal blood vessel ; R^ radial water vessel in an ambulacral area; A^ an inter-ambtilacral area ; 7//, muscles of the lantern. puscles of the body fluid. The spacious body cavity is lined by ciliated epithelium and contains a " perivisceral " fluid, whose corpuscles have a respiratory pigment (echino- chrome). When the fluid of a perfectly fresh sea urchin is emptied out, the contained corpuscles unite in plasmodia, forming composite ainceboid clots (cf Proteomyxa, &:c.). ll'a/er Vascular System. The madreporic plate communicates with a membranous stone canal, which runs downwards into a circular vessel. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Thomson, J. Arthur (John Arthur), 1861-1933; Newbigin, Marion I. (Marion Isabel), 1869-1934; Smith, Preserved, 1880-1941. fmo. New York, D. Appleton & Co.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
