. Elementary text-book of zoology. Zoology. SCAP1IOPODA. 29 -Br (fig. 506). The body possesses a saccular mantle, like the shell open at both ends, and a trilobed foot; the foot is protruded through the larger of the openings of the shell- from the anterior opening of the mantle, the margin of which is thickened. A separated cephalic region is not present, .but there is an egg-shaped projection in the mantle cavity, at the apex of which is placed the mouth, surrounded by eight leaf-like labial appendages. The buccal armature con- sists of a lateral (right and left) rudimentary jaw, and a tongu
. Elementary text-book of zoology. Zoology. SCAP1IOPODA. 29 -Br (fig. 506). The body possesses a saccular mantle, like the shell open at both ends, and a trilobed foot; the foot is protruded through the larger of the openings of the shell- from the anterior opening of the mantle, the margin of which is thickened. A separated cephalic region is not present, .but there is an egg-shaped projection in the mantle cavity, at the apex of which is placed the mouth, surrounded by eight leaf-like labial appendages. The buccal armature con- sists of a lateral (right and left) rudimentary jaw, and a tongue beset with five rows of plates. The alimentary canal is divided into a buccal cavity, resophagus, stomach with large liver, and an intestine, which after several coils closely pressed together, opens behind the foot into the middle of the mantle cavity. The circulatory organs are reduced to two mantle vessels and a complicated system of wall-less spaces of the body cavity. Respiration is effected by the surface of the mantle and also by the filiform tentacles, which arise from two ridges (cervical collar) behind the head-like buccal prolongation. The kidney lies round the rectum, and opens by two openings placed on the right and left of the anus. The nervous system consists of three groups of ganglia, of which the pedal ganglion bears two otocysts. Eyes are absent. The numerous ciliated tentacles serve as tactile organs. The Sca/pkopoda are dioecious. The ovaries and testes are un- paired finger-shaped lobed glands, which are placed behind the liver and intestine, and open to the exterior with the right kidney. FIG. 50C.— Tarent in urn (after Lacaze- Duthiers). Animal without ' shell from right side. .; Mt, circular muscle of mantle; M, longi. tudinal muscle ; BI-, gills; N, kid- ney; L, liver; G, generative s 507.—Larva of Dentu- Hi'.m (after Lacaze-Du- thiers). a, young larva with first rudiment of shell (S). I, Older larva seen from the dorsal sur-
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
