. The coral Siderastrea radians and its postlarval development. Siderastrea radians Verrill. 26 SIDERASTREA RADIANS. in each sextant the third-cycle pair (in) is situated on the dorsal aspect of the second-cycle pair (11). In the right middle sextant, where two pairs of third-cycle mesenteries occur, a pair is present on both the dorsal and ventral aspects of the longer pair. It is shown later that the mesenteries of the first and second cycles are developed in a very definite sequence, and such would probably be the case for the members of the third cycle were the polyps isolated and free to
. The coral Siderastrea radians and its postlarval development. Siderastrea radians Verrill. 26 SIDERASTREA RADIANS. in each sextant the third-cycle pair (in) is situated on the dorsal aspect of the second-cycle pair (11). In the right middle sextant, where two pairs of third-cycle mesenteries occur, a pair is present on both the dorsal and ventral aspects of the longer pair. It is shown later that the mesenteries of the first and second cycles are developed in a very definite sequence, and such would probably be the case for the members of the third cycle were the polyps isolated and free to develop normally all around. The individual polyps in a colonial coral like Siderastrea, however, are so closely arranged ' ' ^efO^^^f^^ Ilia. I FIG. 3.—Diagram of mesenteries of fig. 34, plate 6 (c/. figs, i and a, pp. 12, 13), that their growth after the first two cycles becomes largely influenced by spatial necessities. Hence, in the particular polyp from which plate 6, fig. 34, is taken, one region, the right middle sextant, has progressed farther than the others. Throughout the studies little constancy has been found in the order of development of the members of the third cycle. The amount of variability in the number and disposition of the mesenterial pairs is repeated in the septa (p. 48). In no two polyps, among a dozen or so studied in transverse sections, was the mesenterial plan the same for the third cycle; also, in none was the full complement of twelve pairs present. The normal sequence of the mesenteries is more fully described in connection with the development of 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 Duerden, James Edwin, 1869-. Washington, The Carnegie Institution
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