. Elementary text-book of zoology. Zoology. usually much coiled, and as a rule bend forwards to open in front on the right side in -the mantle cavity. The anus, however, is some- times on the dorsal surface behind. Many of the higher Gastropoda possess an invaginable proboscis, the invagination beginning at the base; others possess one which is retractile from the point. The mouth is bounded by lips, and leads into a buccal cavity armed with hard masticating structures, and receiving the ducts of two salivary glands. The buccal cavity leads into the oesophagus, which is followed by a dilated s
. Elementary text-book of zoology. Zoology. usually much coiled, and as a rule bend forwards to open in front on the right side in -the mantle cavity. The anus, however, is some- times on the dorsal surface behind. Many of the higher Gastropoda possess an invaginable proboscis, the invagination beginning at the base; others possess one which is retractile from the point. The mouth is bounded by lips, and leads into a buccal cavity armed with hard masticating structures, and receiving the ducts of two salivary glands. The buccal cavity leads into the oesophagus, which is followed by a dilated stomach, usually provided with a caecal appendage. The stomach opens into an intestine, which is usually long and much coiled, and surrounded by a very large, multi-lobed liver. The liver occupies nearly all the upper part (upper coils) of the visceral sac, and pours its secretion into the intestine and also into the so-called stomach (fig. 511). The arrangement of the digestive canal and of the liver presents in details many essential modifications; one of the most remarkable is that offered by the intestine with its hepatic ca?ca of the Phlebenterata (fig. 512). The terminal portion of the intestine is distinguished by its size, and may be called the rectum. Of, The armature of the buccal cavity consists partly of jaws placed on the upper wall, partly of the so-called lingual ribbon (radu- la). placed on a tongue-like pro- section through the jection of the ventral surface of buccal mass of JfeKa(). ' . , . O, mouth; M h, buccal cavity; M, muscles; tlie DUCCal Cavity. ^ j-a^ig,. Zn, lingual cartilage ; Oe, The jaws consist either of a single oesophagus; i'f, jaws; z, sheath of curved horny plate, placed close behind the edge of the lip, or of two lateral pieces of very different form, between which, in some Pulmonatee, there is an unpaired piece. There are no lower jaws; but on the floor of the buccal FIG. 512.—Alimentary canal of JEo7i
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
