. A manual of zoology. Zoology. Fig. 304.—Sea urchin opened around the equator. A, ambulacral area; 7, inter- ambulacral area; L, lantern; d, intestine; ed, anal end of intestine; g, gonads; nd, siphon; of, oesophagus; p, p', ring canal and Polian vesicles; st, stone canal. calcareous teeth, which in the Regularia are supported by a complicated system of levers, fulcra, and muscles, the 'lantern of Aristotle' (fig. 305). The ring canal and the ring of the blood system lie on the lantern, the stone canal and septal organ ('heart') extending upwards from them (fig. 303). The blood-vascular ring
. A manual of zoology. Zoology. Fig. 304.—Sea urchin opened around the equator. A, ambulacral area; 7, inter- ambulacral area; L, lantern; d, intestine; ed, anal end of intestine; g, gonads; nd, siphon; of, oesophagus; p, p', ring canal and Polian vesicles; st, stone canal. calcareous teeth, which in the Regularia are supported by a complicated system of levers, fulcra, and muscles, the 'lantern of Aristotle' (fig. 305). The ring canal and the ring of the blood system lie on the lantern, the stone canal and septal organ ('heart') extending upwards from them (fig. 303). The blood-vascular ring gives off two blood-vessels which run along the alimentary canal, while from the ring canal arise five ambu- lacral or radial canals which run on the inner side of the test, accompanied by nerves which, enclosed in a tube of infolded ectoderm, radiate from a nerve ring. The gonads are five (rarely four or two) unpaired organs in the aboral half of the test, opening through the genital plates, that is, interra- dially as in the starfish. Order I. Palgechinoidea. Paleozoic forms with five ambulacral areas, the interambulacral areas con- taining more than two rows of plates. Melonitcs. Order II. Cidaridea (Regularia). Ambulacral areas band-like, body more or less spherical, mouth and anus polar. Common urchins; Toxopneus/es* Slrongylocentrolus/' Arbacia* Calo- pleurus* (fig. 301). 20 Fio. 305.—Aristo- tle's lantern of Slrmi- gylocentrotus lividus (after Schmarda). b, radulx; /:, alveoli; z, 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 Hertwig, Richard, 1850-1937; Kingsley, J. S. (John Sterling), 1854-1929, ed. and tr. New York, H. Holt
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
