. Elements of zoology, to accompany the field and laboratory study of animals. Zoology. HYDRA 275 The coral polyp does not differ essentially from Metridium. But it has the habit of secreting lime at its base, so that, in com-se of time, a high cup is built up. The top of the cup bears radial septa,' which are laid down in the interspaces between the fleshy partitions such as are found in j\Ictridiian. Since most corals, like hydroids, bud freely, and since every bud secretes coral at its base, an extensive and complicated limy mass may be produced. This is the way in which the brain corals an
. Elements of zoology, to accompany the field and laboratory study of animals. Zoology. HYDRA 275 The coral polyp does not differ essentially from Metridium. But it has the habit of secreting lime at its base, so that, in com-se of time, a high cup is built up. The top of the cup bears radial septa,' which are laid down in the interspaces between the fleshy partitions such as are found in j\Ictridiian. Since most corals, like hydroids, bud freely, and since every bud secretes coral at its base, an extensive and complicated limy mass may be produced. This is the way in which the brain corals and branching corals are Fig. 265. — Coral r-up of Manicina. Nat. size. Photo, by W. H. C. P. The only coral of the northeastern United States is Astrangia dance, which occurs north to Cape Cod. It is a beautifully trans- parent species, and forms thin encrustations of limy matter (Fig. 266). The Sea Walnuts or Ctenophora are a small group of exclu- sively marine organisms that are usually placed in the group Cnidaria, but differ very widely either from the Hydra or the Scyphozoa. The mouth lies centrallj^ at the lower ]3ole of the barrel-shaped animal, and is usually guarded by one or two tentacles. The food-cavity runs through the axis of the body, enlarging near the upper pole. From this enlargement a 'Fig. 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 Davenport, Charles Benedict, 1866-1944; Davenport, Gertrude Anna Crotty, 1866- joint author. New York, Macmillan
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1911
