Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 CRINOIDEA. 287 attached by its dorsal apex. The segments of the stalk, which are mostly pentagonal, are connected by bands of tissue, and are pierced by a central canal, which serves for nutrition, and contains a central and five peripheral blood vessels; at certain distances they bear hollow and segmented cirri, which are arranged in whorls. The dorsal surface of the calyx is covered externally by regularly arranged calcareous plates, while the upper (ventral) surface, on which the mout
Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 CRINOIDEA. 287 attached by its dorsal apex. The segments of the stalk, which are mostly pentagonal, are connected by bands of tissue, and are pierced by a central canal, which serves for nutrition, and contains a central and five peripheral blood vessels; at certain distances they bear hollow and segmented cirri, which are arranged in whorls. The dorsal surface of the calyx is covered externally by regularly arranged calcareous plates, while the upper (ventral) surface, on which the mouth and anus are situate, is clothed with a leathery FIG. 232.—Comiitnl(i mnlifrrranea represented from the ventral side. O, mouth ; A, anus. The pinnulae are filled with the generative products. skin. At the margin of the cup there arise movable, simple or forked, and often branched arms, which are supported by a solid framework consisting of dorsally placed calcareous plates, which are movable upon one another by special muscles. In almost Arch, fur Xatxrgescli, 1S.'>1. \V. Thompson, 'On the Embryology of the Antedon rosaceus,' Phil. Trans. Bo;/. Sat-., Tom 155, lSi;r>. \V. 1!. Carpenter, 'Researches on the Structure. Physiology and Development of Antedon rosaceus,' Ibid., Tom 15(i. A. Gott'e, ' Vergl. Bntwickelungsgeschichte cler Comatula Mediterranea,' A whir, fiir nilrkriiali. Anntmnic. Tom XII. 11. Ludwig, ' Morphol. Studien an Echinodermen,' Leipzig, 1»77.
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