. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). TYPE MOLLUSC A. 279 of the blood with those of the water contained in the mantle- cavity being thus readily effected, a renewal of the water con- stantly taking place in consequence of the action of the ecto- dermal cilia. The thin-walled mantle-fold is, however, a very efficient adjunct to the branchiae in respiration, the spaces within the fold being portions of the lacunar coelom and con- sequently containing blood ; indeed in some cases the mantle assumes completely
. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). TYPE MOLLUSC A. 279 of the blood with those of the water contained in the mantle- cavity being thus readily effected, a renewal of the water con- stantly taking place in consequence of the action of the ecto- dermal cilia. The thin-walled mantle-fold is, however, a very efficient adjunct to the branchiae in respiration, the spaces within the fold being portions of the lacunar coelom and con- sequently containing blood ; indeed in some cases the mantle assumes completely the respiratory function, the ctenidia becoming rudimentary. The digestive tract is a usually more or less coiled or con- voluted tube in which various regions may be distinguished. In a few forms, characterized either by the slight develop^ ment of the mantle or its development as two lateral folds the anus is terminal in position, but when an extensive cir- cular mantle-fold is developed the intestine bends upon itself and opens upon the side of the body, more or less anteriorly into the mantle-cavity. Immediately behind the mouth chi' tiuous teeth (Fig. 123, hj) are usually developed in the wall of. Fig. Mass and Radula of Helix (after Howes). ce = cerebral ganglion. re = nidular cartilage. hj — horny jaw. tm = intrinsic muscles. pgl = pedal gland. rd = radula. I'd' = radular sac. St = opening of salivary gland. the pharynx, and behind these a large muscular thickening generally occurs, the buccal mass, in connection with which is developed a characteristic Molluscan structure, the lingual ribbon or radula (rd). The sides and floor of the pharynx in tins region are largely thickened by the development in them of muscular tissue (wi). The thickening of the floor is usually so extensive as to project into the pharyngeal cavity, forming. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability -
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishernewyo, bookyear1896
