. The animans and man; an elementary textbook of zoology and human physiology. pearlcome from the tropical species Meleagrina pearl-oyster has an extensive distribution, beingfound in Madagascar, the Persian Gulf, Ceylon, Australia,Philippine Islands, South Sea Islands, Panama, WestIndies, etc. Mother-of-pearl is simply the inner liningof the shell, which is composed of numerous thin layers ofcarbonate of lime so arranged that the edges of the suc-cessive layers produce many fine striae very close beautiful iridescence of this inner shell-lining is causedby the
. The animans and man; an elementary textbook of zoology and human physiology. pearlcome from the tropical species Meleagrina pearl-oyster has an extensive distribution, beingfound in Madagascar, the Persian Gulf, Ceylon, Australia,Philippine Islands, South Sea Islands, Panama, WestIndies, etc. Mother-of-pearl is simply the inner liningof the shell, which is composed of numerous thin layers ofcarbonate of lime so arranged that the edges of the suc-cessive layers produce many fine striae very close beautiful iridescence of this inner shell-lining is causedby the complicated diffraction and reflection (interferenceeffects) of the light by the fine striae and the translucent ARTHROPODS AND MOLLUSCS 175 superposed thin plates of shell material. Pearls are simplyisolated deposits of shell material usually around someparticle of foreign substance which has found lodging inthe mantle-cavity. Sometimes small objects are pur-posely introduced into the shell in order to stimulate theformation of pearls. The pearl-fishers go out in boats and. FIG. 86. Martesia xylophaga, a Pholad, burrowing in Panama mahogany.(Photograph by C. H. Snow; permission of the American Societyof Civil Engineers.) dive to the bottom, filling baskets with pearl-oysters. Theseare piled up in a bin and left to die and decompose. Whenthe flesh is pretty thoroughly disintegrated, it is washed awaywith water, great care being taken that none of the pearlsloose in the flesh are lost. When the washing is concludedthe shells themselves are examined for pearls which maybe attached to the interior of the valves. The principalpearl-fishery is that on the coast of Ceylon; pearl-fishinghas been carried on here for over 2000 years. The ship-worm (Teredo) is an interesting member of thisclass of bivalve molluscs, because of its unusual habits, andstrangely modified body form. The teredo is long andworm-like in general appearance, with a small bivalve shellat one end and two elongated s
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Keywords: ., bookcentury1900, bookd, booksubjectphysiology, booksubjectzoology
