. The sea-beach at ebb-tide : a guide to the study of the seaweeds and the lower animal life found between tidemarks . to u pieoe ofof genera the foot contains w: *• ft: *• txt-iuiTt-»t *ipi>». ti,,. branchial si,,i,,,,, being below it and not closed. a gland for the secretion of long silk-like or horn-like fibers, which are collectively calledThe use of a byssus is for attachment to any object to effect a temporary or per-manent lodgment. Theaccompanying cut showsMi/filns c<h<lin, a commoneast-coast pelecypod, at-tached by its bjrssus to apiece of wood. Most bi-valves having a strong
. The sea-beach at ebb-tide : a guide to the study of the seaweeds and the lower animal life found between tidemarks . to u pieoe ofof genera the foot contains w: *• ft: *• txt-iuiTt-»t *ipi>». ti,,. branchial si,,i,,,,, being below it and not closed. a gland for the secretion of long silk-like or horn-like fibers, which are collectively calledThe use of a byssus is for attachment to any object to effect a temporary or per-manent lodgment. Theaccompanying cut showsMi/filns c<h<lin, a commoneast-coast pelecypod, at-tached by its bjrssus to apiece of wood. Most bi-valves having a strong bys-SUS exhibit 8 feeble develop-ment of the foot: nearly all bivalves, however, show traces, some-times only in the embryo, of a byssal gland. The visceral mass contains the liver, the exceedingly large gen-erative glands, the kidneys, etc., and through all this soft whitish orreddish mass the alimentary canal wanders about in a tortuousfashion, finally passing through the pericardium and the ventricleof the heart, and terminating just over and back of the posterioradductor , <!//.,v»/,;,-/X showing the ocelli, or eyes, on thet\v fdi_ f llic mantle. 416 MARINE INVERTEBRATES The pelecypods have no head or tentacles, but the place of thelatter is taken by two pairs of triangular flaps upon either side ofthe mouth. These are called the labial palps, and they no doubtoperate by means of their ciliated surface to keep in motion thecurrent of water over the gills and to the mouth. As a rule, pelecypods have no eyes, but when eyes are presentthey are situated upon the edge of the mantle. The eyes are nothighly developed organs, but they nevertheless appear to be verysensitive to light, for the bivalves which are so endowed will, whenkept in aquaria, instantly close their shells when the shadow of afish passes over them. The heart lies in the pericardium and is situated dorsally, justin front of the posterior adductor muscle. It has a median ven-tricle and two late
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmarinea, bookyear1901
