. Seaside studies in natural history. Marine animals. EMBEYOLOGY OP ECaaiNODERMS. 131 ^owth. In these early stages the young, or the so-called larvae of Echinoderms, have received the name of Pluteus on account of their ever-changing forms. Let us look for a moment at the plutean stages of the Searurchin, as they differ in some poinl^ from those of the Star-fish. In the Pluteus of our common Searurchins (see Fig. 176), the arms are supported by a frame- work of solid limestone rods, which do not exist in that of the Star-fish, and which give to the larva of the Sea-urchin a re- markable rigidi
. Seaside studies in natural history. Marine animals. EMBEYOLOGY OP ECaaiNODERMS. 131 ^owth. In these early stages the young, or the so-called larvae of Echinoderms, have received the name of Pluteus on account of their ever-changing forms. Let us look for a moment at the plutean stages of the Searurchin, as they differ in some poinl^ from those of the Star-fish. In the Pluteus of our common Searurchins (see Fig. 176), the arms are supported by a frame- work of solid limestone rods, which do not exist in that of the Star-fish, and which give to the larva of the Sea-urchin a re- markable rigidity. They are formed very early, as inay be seen Kg. in Kg. 173, representing the little Sea-urchin before any arms are discernible, though the limestone rods are quite distinct. Mgs, 173,174, 176, may be compared with Figs. 160,162,165, of the young Star-fish, where it will be seen that the general out- line is very similar, though, on account of the limestone rods, the Pluteus of the Sea^-urchin seems somewhat more complicated. In. 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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