. Chambers's encyclopaedia; a dictionary of universal knowledge. (//(/nmeid)which lies at the dorsal meeting-place of the twovalves, and acts likea piece of india-rubbersfjueezed into thehinge-line of a closeddoor ; the shell is shutby one or two greatmuscles (adductors)which run across fromvalve to valve. Thereare also muscles, moreor liss powerful accord-ing to habit, for work-ing the foot. Themarks made by the in-sertion of the muscleson the sliell are readilyseen inside the emptyvalves, ((j) The ticrr-Otis system consists ofthree chief pairs ofganglia, the anteriorcerebral pair beingu
. Chambers's encyclopaedia; a dictionary of universal knowledge. (//(/nmeid)which lies at the dorsal meeting-place of the twovalves, and acts likea piece of india-rubbersfjueezed into thehinge-line of a closeddoor ; the shell is shutby one or two greatmuscles (adductors)which run across fromvalve to valve. Thereare also muscles, moreor liss powerful accord-ing to habit, for work-ing the foot. Themarks made by the in-sertion of the muscleson the sliell are readilyseen inside the emptyvalves, ((j) The ticrr-Otis system consists ofthree chief pairs ofganglia, the anteriorcerebral pair beingunited liy connectivesto a pair in the foot(pedal), and to a pos-terior pair calledparieto-splanchtiic or viscercd. From these threecentres numerous nerves are given off to the 1>odygenerally. An auditorj* sac (otoryst) is found inclose association with the pedal ganglia, and a. Fig. 2. — Vertical Sectionthrough a Fresh-water^lussel: a. mantle; 6, filaments of gills;c, ventricle of heart; d, auricleof heart; e, gut grown roundby ventricle. 194 BIVALVES BIVOUAC patch of smelling or water-testing cells {osuhrad-tuin) occurs at the base of the gills. Thougheyes are never present on the reduced head, theysometimes occur in extraordinary abundance (tothe number of many hundreds) along the marginof the mantle ( Pecten, Area). (/<) The heartlies just l)elow the hinge, and consists of a con-tractile median ventricle driving the blood to thebody, and of two auricles symmetrically placedon each side, receiving puritiod blood from thegills. The %-entricle usually grows round the gut,which thus api^ears to run right througli the whole organ is inclosed in a special portionof the body-cavity known as the pericardium, andthis is in indirect communication with the exteriorl)y means of two (/) kidney-tubes (nephridia)which lie below the heart, and open ext
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Keywords: ., bookcentury1900, bookdecade1900, bookpublisherlondo, bookyear1901
