. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SKELETON FORMATION OF SEA URCHIN LARVAE 179 i o Ca D O O. FIGURE 3. Spicules of H. pulcherrimus in Ca and 3 Mg. A, transferred at calcareous granule stage and sketched 25 hours later (13° C.) ; B, transferred at triradiate spicule stage and sketched 23 hours later at 13° C. (compare \vith Figure 1). (1) Ca and 2 Mg. The calcareous granules of the early gastrula acquire a triradiate form, although lengthening of the spicule is more or less retarded while its thickening is accelerated (Fig. 1). These triradiate spi
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SKELETON FORMATION OF SEA URCHIN LARVAE 179 i o Ca D O O. FIGURE 3. Spicules of H. pulcherrimus in Ca and 3 Mg. A, transferred at calcareous granule stage and sketched 25 hours later (13° C.) ; B, transferred at triradiate spicule stage and sketched 23 hours later at 13° C. (compare \vith Figure 1). (1) Ca and 2 Mg. The calcareous granules of the early gastrula acquire a triradiate form, although lengthening of the spicule is more or less retarded while its thickening is accelerated (Fig. 1). These triradiate spicules ultimately develop so that they have all the component rods of the pluteus skeleton (Fig. 2, B), which are seemingly normal but shorter and thicker than those of the sea water control. This is true even if the treatment is begun after the spicule has taken a triradiate form in sea water. On the whole, spicular growth in Ca is superior to that in 2 Mg. but the ratios, width/length of the spicule. are much the same in these two media. (2) Ca and Alg. In comparison with the spicules found in Ca, those in Mg are smaller in size but quite similar in shape. Since lengthening of the spicule is strikingly inhibited, while its thickening is not so much impeded, Ca. 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 Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983. Woods Hole, Mass. : Marine Biological Laboratory
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