. Animal biology; Human biology. Parts II & III of First course in biology. Biology. The largest species of sea urchins are almost as big as a child's head, but such size is unusual. The spines are mounted on knobs, and the joint resembles a ball-and-socket joint, and allows a wide range of movement. Some sea urchins live on sandy shores, other species live upon the rocks. The sand dollars are lighter colored. (Why?) They are usu- ally flatter and have lighter, thinner walls than the other species. The five- holed sand cake or sand dollar has its weight still further diminished by the hole
. Animal biology; Human biology. Parts II & III of First course in biology. Biology. The largest species of sea urchins are almost as big as a child's head, but such size is unusual. The spines are mounted on knobs, and the joint resembles a ball-and-socket joint, and allows a wide range of movement. Some sea urchins live on sandy shores, other species live upon the rocks. The sand dollars are lighter colored. (Why?) They are usu- ally flatter and have lighter, thinner walls than the other species. The five- holed sand cake or sand dollar has its weight still further diminished by the holes, which also allow it to rise more easily through the water. Both starfish and sea urchin rest on the flattened lower surface of the body, while the tube feet are stretching for- ward for another step. OTHER ECHINODERMS The sea cucumbers, or holothurians, re- semble the sea urchin in many respects, ^^^A^^-~:-—1:"^ FIG. SEA OT- TER, an urchin with mouth (<?) and vent (A) on same side of SP^' '. 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 Bailey, L. H. (Liberty Hyde), 1858-1954. New York, The Macmillan Co.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1910
