. Animal biology. Zoology; Biology. A/toui-h Fooi-. ce//s arrrar/ tre/Zs Fig. 132.—Trochophore of Patella, one of the limpets. A, viewed from the ventral side. B, median section of a slightly older trochophore. {From Korschelt and Heider, " Text-book of Embryology.'") 266. Economic Importance.—Mollusks are of economic importance from several points of view. Their greatest value is as human food. The reports of the U. S. Fish Commission showed, in 1930, a total value of canned oysters, clams, and other shellfish, and of by-products amount- ing to over $17,000,000. The total for 1931 w
. Animal biology. Zoology; Biology. A/toui-h Fooi-. ce//s arrrar/ tre/Zs Fig. 132.—Trochophore of Patella, one of the limpets. A, viewed from the ventral side. B, median section of a slightly older trochophore. {From Korschelt and Heider, " Text-book of Embryology.'") 266. Economic Importance.—Mollusks are of economic importance from several points of view. Their greatest value is as human food. The reports of the U. S. Fish Commission showed, in 1930, a total value of canned oysters, clams, and other shellfish, and of by-products amount- ing to over $17,000,000. The total for 1931 was nearly $14,000,000. Snails are much eaten in some countries of Europe and to a certain degree also in this country. Among the bivalve mollusks clams, oysters, scallops, and other forms are regular articles of diet. The value of the oyster industry alone along the Atlantic seaboard has been estimated at between $30,000,000 and $40,000,000 annually. The arms of squids are also cut off and used as food. The shells of many of the mollusks are for one reason or another articles of commerce. Many of them are sold as ornaments on account of their beauty. Others are used in the production of pearl buttons, and the pearl-button industry has attained great proportions in this country, especially in Ohio, Illinois, and Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Wolcott, Robert Henry, 1868-1934. New York ; London : McGraw-Hill Book Company, Inc.
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