. Seaside studies in natural history. Marine animals. EMBRYOLOGY OP ECHINODERMS. 135 Ophiwram. Pig. 183 represents an Ophiuran undergoing the same process of growth, at a period when the larva is most fully developed, and before it begins to fail. By the limestone rods which support the arms, the Pluteus of the Ophiuran, here represented, resembles that of the Sea-urchin more than that of the Star-fish, while by the character of the water-tubes and by its internal organization it is more closely allied to the latter. It differs from both, how- ever, in the immense length of two of the arms; th
. Seaside studies in natural history. Marine animals. EMBRYOLOGY OP ECHINODERMS. 135 Ophiwram. Pig. 183 represents an Ophiuran undergoing the same process of growth, at a period when the larva is most fully developed, and before it begins to fail. By the limestone rods which support the arms, the Pluteus of the Ophiuran, here represented, resembles that of the Sea-urchin more than that of the Star-fish, while by the character of the water-tubes and by its internal organization it is more closely allied to the latter. It differs from both, how- ever, in the immense length of two of the arms; these arms being the last signs of its plutean condition to disappear; when the young Ophiuran has absorbed almost the whole Pluteus, it still goes wandering about with these two immense appendages, which finally share the fate of aU the rest. Fig. 182 represents Fig. an Ophiuran at the moment when the process of resorption is nearly completed, though the arms of the Pluteus, greatly di- minished, are still to be seen protruding from the surface of the animal. This mode of development, though common to all Echino- Fig. 182. Ophiuran which has resorbcd the whole larva except the two long arms, y y' limestone (odB of young Ophiuran, r middle of back ; lettering !i3 in Fig. 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 Agassiz, Elizabeth Cabot Cary, 1822-1907; Agassiz, Alexander, 1835-1910, joint author. Boston, J. R. Osgood and Company
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