. The sea-beach at ebb-tide : a guide to the study of the seaweeds and the lower animal life found between tidemarks . de, is aneye. Just below and between the tentacles is a small horizontalslit,—the mouth,—the lips being slightly thickened. The visceralportion of the animal is above the foot, or dorsal to it, and ex-tends the whole length of the animal from the mouth to theexcretory opening, the latter being situated posteriorly. Thevisceral cavity is inclosed above by a thin skin ; indeed, it is butthe great thickening of this skin below that constitutes the foot. The digestive tract, begin
. The sea-beach at ebb-tide : a guide to the study of the seaweeds and the lower animal life found between tidemarks . de, is aneye. Just below and between the tentacles is a small horizontalslit,—the mouth,—the lips being slightly thickened. The visceralportion of the animal is above the foot, or dorsal to it, and ex-tends the whole length of the animal from the mouth to theexcretory opening, the latter being situated posteriorly. Thevisceral cavity is inclosed above by a thin skin ; indeed, it is butthe great thickening of this skin below that constitutes the foot. The digestive tract, beginning at the mouth, opens immediatelyinfo a muscular throat, which is called the Ittn-cnl nut**. Withinthe buccal mass there is a long, fleshy ribbon tliat bears upon itsupper surface numerous rows of sharp teeth ; tliese rows of teethrun crossways on the ribbon, each row containing more or lessprominent median teeth, with several laterals upon each side, andwith marginal teeth on each side of the laterals. This is calledthe railnla, and is used for tearing or rasping the food. When 318 MARINE INVERTEBRATES eo (/ O Ideal or schematic mollusk. 1, dorsal view: h, head; t, cephalic tentacle; sh., shell covering visceral mass; , outline ofbody-mass; r. m. e., edge of mantle; c. t., ctenidia, or-gills; q. «., generative apertures ; r. e., renalopenings ; e. o., excretory opening; /, posterior portion of foot; o. e. m., edge of shell. 2, ventral view: ft, head; t, tentacle; m, mouth; 6, outline of body; , edge of mantle; ,lower surface of foot; c. t., ctenidia, or gills ; /, posterior portion of foot. 3, horizontal section, showing heart, nephridia, and gonads : m, mouth ; o, esophagus; g, gonad;p, pericardium; n, nephridium. or renal organ; v, ventricle; a, auricles; g, gonad aperture; n,renal opening; e, excretory opening; /, posterior portion of foot. 4, vertical median section: m, mouth; , buccal mass; I, liver; A. a., digestive tract; q,gonad; /, foo
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmarinea, bookyear1901
