. Comparative zoology, structural and systematic : for use in schools and colleges. Zoology; Anatomy, Comparative; Physiology, Comparative. 262 COMPARATIVE passing from pole to pole, like the ribs of a melon, alter- nate with five other double rows. In one set, called the ambulacra, the plates are perfo- rated for the pro- trusion of tubular feet, or suckers, as in the Star - fish. So that altogether ^ there are twenty series of plates- ten ambulacral, andteninterambu- lacral. The shell is not cast, but grows by the en- largement of each individual plate, and the addition of new ones
. Comparative zoology, structural and systematic : for use in schools and colleges. Zoology; Anatomy, Comparative; Physiology, Comparative. 262 COMPARATIVE passing from pole to pole, like the ribs of a melon, alter- nate with five other double rows. In one set, called the ambulacra, the plates are perfo- rated for the pro- trusion of tubular feet, or suckers, as in the Star - fish. So that altogether ^ there are twenty series of plates- ten ambulacral, andteninterambu- lacral. The shell is not cast, but grows by the en- largement of each individual plate, and the addition of new ones around the mouth and the opposite pole. Every part of an Echinus, even sections of the spines, show the principle of radiation. If the up- per surface of a Star-fish should shrink so as to bring the points of the arms to meet above the mouth, we should have a close imitation of a Sea-urchin. Echini live near the shore, in rocky holes or under sea-weed. They are less active than Star-fishes; but, like them, feed on Mollusks and Crabs. They reproduce by minute red eggs. Regular Echini, as the common Cidaris, are nearly globular, and the oral and anal openings are opposite. Irregular Echini, as the Glypeaster, are flat, and the anal orifice is near the margin. Fig. 214. —Under-surface of a Sea-urchin {Echinus escu> lentus), showing rows of suckers among the spines, British seas. Class IV.—Holothuroidea. These worm-like " Sea-slugs," as they are called, have a soft, elongated body, with a tough, contractile skin contain-. 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 Orton, James, 1830-1877; Birge, E. A. (Edward Asahel), 1851-1950. New York : Harper & Bros.
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1883
