. Elementary zoology. Zoology. 254 ELEMENTARY ZOOLOGY to the stems or leaves of plants placed in the water. They are so transparent as to be easily overlooked.': Young snails may be reared from these eggs. There are other snails common in ponds, also called, like the pulmonate forms, pond-snails, which have gills and no lung-sac. These pond-snails belong to a different order of molluscs, and live on the bottom of the pond, crawling about in the soft mud and feeding on animal instead of vegetable food. The shells of the various kinds of snails vary much. In many of the land-snails the spiral is
. Elementary zoology. Zoology. 254 ELEMENTARY ZOOLOGY to the stems or leaves of plants placed in the water. They are so transparent as to be easily overlooked.': Young snails may be reared from these eggs. There are other snails common in ponds, also called, like the pulmonate forms, pond-snails, which have gills and no lung-sac. These pond-snails belong to a different order of molluscs, and live on the bottom of the pond, crawling about in the soft mud and feeding on animal instead of vegetable food. The shells of the various kinds of snails vary much. In many of the land-snails the spiral spire-shaped or conical, but is flat. In some the whorls of the spiral run from left to right (dextral) when the shell is looked at with apex held toward one, while in others the whorls run from right to left (sinistral). Of the hosts of marine Gastropods we can notice only a few kinds. The nudibranchs (fig. 109) are a group Gf. Fig. 109.—Three Pacific Coast nudibranchs; Doris tuberculata (in lower left-hand corner), Echinodoris sp. (upper one), and Triopha modesta (at right). (From living specimens in a tide-pool on the Bay of Mon- terey, California.) beautiful forms in which the shell is wholly wanting and the mantle is usually absent. The gills are thus exposed and are usually in the shape of delicate freely projecting. 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 Kellogg, Vernon L. (Vernon Lyman), 1867-1937. New York : H. Holt and company
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1902
