. A manual of zoology. Zoology. IV. GASTEROPODA 331 supraintestinal), while the left passes under the intestine to the right side (subintestinal), the cerebrovisceral commissures being twisted like the figure 8. The strong development of the pharynx is accompanied by buccal ganglia. Gills, heart, and nephridia are best treated together. Certain genera {Haliolis,Fissurella, etc.) recall the Acephala in having the heart traversed by the intestine, the paired ctenidia, nephridia and nephridial ducts, and two auricles to the heart. As a rule the asymmetry induced by the torsion of the body has res
. A manual of zoology. Zoology. IV. GASTEROPODA 331 supraintestinal), while the left passes under the intestine to the right side (subintestinal), the cerebrovisceral commissures being twisted like the figure 8. The strong development of the pharynx is accompanied by buccal ganglia. Gills, heart, and nephridia are best treated together. Certain genera {Haliolis,Fissurella, etc.) recall the Acephala in having the heart traversed by the intestine, the paired ctenidia, nephridia and nephridial ducts, and two auricles to the heart. As a rule the asymmetry induced by the torsion of the body has resulted in the loss of the ctenidium, osphradium, and nephridium of the primitively left side, and with the loss of one gill there. Fig. 338.—Anatomy of Cyprara tigris (after Quoy et Gaimard). hr, ctenidium; c, heart; df, vas deferens, /;, liver; m, stomach; A^, cerebral ganglion; oc, eve; pe, penis; ph, pharynx, the radula drawn out; r, rectum; re, nephridium; t, testes. is usually a loss of the corresponding auricle. Prosobranchs and Opistho- branchs are recognized accordingly as the gills are on the anterior or posterior part of the body. In the Opisthobranchs (fig. 337) the ctenidia have been lost and are replaced by secondary gills on the back. Here the heart is in front of the gills; it receives blood from behind and forces it forward to the head by an aorta. In the Prosobranchs the heart has been twisted so that the auricle and the ctenidium are in front (fig. 338), while the aorta leads backwards. The nephridium, which communicates with the pericardium by a nephrostome, is usuaUy saccular, its duct empties beside the 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
