. A textbook in general zoology. Zoology. X. STARFISH, SEA URCHIN, BRITTLE STARS Branch IX. — Echinodermata {echinos (spine), hedge- hog; derma, skin) Most of the members of this branch have the surface of the body beset with spines; hence the name, Echinoder- mata, meaning spiny skins. In all the echinoderms the parts of the body are arranged in a radial manner. In nearly all there is an exoskeleton composed of calcareous plates. Without exception they are found in the sea. An Example of the Branch — the Starfish The form and radial symmetry of the starfish. —The common starfish has a star-sh
. A textbook in general zoology. Zoology. X. STARFISH, SEA URCHIN, BRITTLE STARS Branch IX. — Echinodermata {echinos (spine), hedge- hog; derma, skin) Most of the members of this branch have the surface of the body beset with spines; hence the name, Echinoder- mata, meaning spiny skins. In all the echinoderms the parts of the body are arranged in a radial manner. In nearly all there is an exoskeleton composed of calcareous plates. Without exception they are found in the sea. An Example of the Branch — the Starfish The form and radial symmetry of the starfish. —The common starfish has a star-shaped body consisting of a central portion known as tiie central disk, and five tapering arms. The arms radiate from the central disk much as the spokes of a wheel radiate from the hulj. This radial arrangement is characteristic of all mem- bers of this loi'anch and is known as radial sijmmetry (Fig. 43). External features. —In its natural position, one side of the body is always uppermost. This side is called the. Fig. 43. -Ventral surface of a 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 Herrick, Glenn W. (Glenn Washington), 1870-1965. New York, Cincinnati [etc. ] American Book Company
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