. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. FIG. 210.—Calcareous bodies from the internment of Holothu- rians. a, calcareous wheels of Chirodota- b, anchor with supporting plate of St/napta • c, chair-like bodies ; d, plates of Hulothuria impatims; e, hooks of Chirodota. (fig. 209), the round form by a shortening of the same and the penta- gonal disc by the latter process combined with a simultaneous elonga- tion of the radii. If the radii are elongated till they are two or more times the length of the inter-radii, the form takes the
. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. FIG. 210.—Calcareous bodies from the internment of Holothu- rians. a, calcareous wheels of Chirodota- b, anchor with supporting plate of St/napta • c, chair-like bodies ; d, plates of Hulothuria impatims; e, hooks of Chirodota. (fig. 209), the round form by a shortening of the same and the penta- gonal disc by the latter process combined with a simultaneous elonga- tion of the radii. If the radii are elongated till they are two or more times the length of the inter-radii, the form takes the shape of a star (Asteroidea), which may be either flat or arched. The arms of the star may be simple processes of the disc, and en- close a part of the body cavity (Stel- leridea, Star-fish}, or they may be more independent moveable organs sharply marked off from the disc, and as a rule simple (Ophiuridat), but sometimes branched (Euryalidce), or they may even bear simple jointed side twigs, the pinnulce (Crinoidea). An important characteristic of the Echinodermata is the indura- tion by calca- reous deposits of the deeper layers of the integument (dermal con- nective tis- sue), so as to give rise to a solid more or less moveable or even im- moveable ar- mour. In the leathery IIolo- thuroidea (fig. 210) alone these skeletal structures are confined to isolated calcareous bodies, which are embedded in the integument, and have a definite form of latticed plates, wheels, or anchors. In these. FIG. 211.—Skeletal plates of Astropecten Hemprlchtii (after J. Miiller). DIt, dorsal marginal ossicles ; VR, ventral marginal ossicles; A/>, ambulacral ossicles ; Jp, intermediate interambulacral ossiclea ; Ad]>, anterior adambulacral ossicles projecting into the 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
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Keywords: ., book, bookcentury1800, bookcollectionbiodiversity, bookdecade1890
