Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0201clau Year: 1884 HEAD AND ITS APPENDAGES. 11 remarkable disturbance. The visceral sac may, however, have a flattened or cylindrical form and retain its symmetry. In this group (the Cepkalophora) the shell may be simply plate-shaped or spirally wound, or remain as a mere flat rudiment hidden under the dorsal integument. In one group of the Cephalophora, viz., the Cephalopoda, a circle of arms is attached to the head around the mouth opening. They serve both for swimming and creeping, and for the capture o
Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0201clau Year: 1884 HEAD AND ITS APPENDAGES. 11 remarkable disturbance. The visceral sac may, however, have a flattened or cylindrical form and retain its symmetry. In this group (the Cepkalophora) the shell may be simply plate-shaped or spirally wound, or remain as a mere flat rudiment hidden under the dorsal integument. In one group of the Cephalophora, viz., the Cephalopoda, a circle of arms is attached to the head around the mouth opening. They serve both for swimming and creeping, and for the capture of nourishment. By Loven and R. Leuckart they were looked upon as modifications of the buccal lobes; by others, perhaps with greater justice, as tentacles, and by others again as Bm FIG. 494.—Male of Carinaria medil'i-ranta (afterGegenbaur). P, F, salivary gland; X, liver; A, anus; CG, cerebral ganglion ; Tf, tentacle; Oc, eye ; Of, auditory vesicle ; £&, buccal ganglion ; PIJ, pedal ganglion; Mg, mantle ganglion; N, kidney; -Be, gill; At, auricle; T>, ventricle; A,; :K ii-ta; Z, hinder branch of the same; T, testis ; TV, vas defereus ; Wp, ciliated furrow ; Pe, penis; F, flagellum with gland. modifications of the foot. A perforated funnel-shaped cone, through which the excretory products and water which has passed over the gills is expelled from the large mantle cavity, and which thus serves at the same time as a swimming organ, probably corresponds to the fused folds of the epipodia. Amongst the Gastropoda the head is provided with tentacles and buccal lobes, and the ventrally placed foot possesses a large Hat plantar surface ; more rarely it has the form of a vertically placed fin (Heterojwda, fig. 494). In another group, the LaiiielUbranchiata (Acephala], there is 110 independent head, and the laterally compressed body bears two large lateral mantle
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