File:Birds and nature (1901) (14745332151).jpg

Identifier: birdsnature9101unse (find matches)
Title: Birds and nature
Year: 1900 (1900s)
Authors:
Subjects: Birds Natural history
Publisher: Chicago, Ill. : A.W. Mumford, Publisher
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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clam progresses by pushingforward its strong, muscular foot, gettinga firm hold of the mud and then drawingthe shell after it. Some peleeypods, asthe oyster, live attached to some objecton the bottom of the water, as a stone,piece of wood or piling of an old wharf,and are not able to travel from place toplace as are the true clams, examples ofthe latter being fresh water mussels andthe marine quahaug or round clam. Some bivalves also attach themselvesby a byssus composed of a number ofsilk-like threads, which anchor theirshells to stones, sticks, and other foreignobjects. In one group (genus Pinna)found in the Mediterranean Sea, thisbyssus is so fine and silky that the Ital-ians weave it with silk and make caps,gloves and other articles of wearing ap-parel. Another wonderful and interesting ar-rangement for the comfort of the animalis its breathing organs or branchiae.These are two or four in number, and aremade up of numerous small chambers,covered with little whip-like organs or 26
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cilia, which keep up a constant motion,creating currents of water, bring- thou-sands of minute organisms to the clam toserve as food. These little organisms,many of them microscopic, are caughtupon the surfaces of the gills, rolled intolittle masses, and passed into the animalsmouth. Besides being food-gatherers,the gills serve to keep up a circulation bywhich fresh water is constantly broughtin to purify and aerate the blood and alsoto expel the waste products. There is nohead in this class, and the mouth is anoval slit surrounded by four lips or palp.,and leads almost directly into the stom-ach. The currents of water spoken of aboveare controlled and directed in several dif-ferent ways. In attached forms, andthose living above the surface of the mud,like the oyster, mussel and scallop, thesoft mantle which lines the shell is divid-ed, forming- a slit nearly the whole diam-eter of the shell, and the water is allowedto circulate freely through the open edgesof the shells. But in those

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