. The animans and man; an elementary textbook of zoology and human physiology. central disk and long rays or radiating arms, and the sea-urchins looking like spiny flattened balls, they are reallyclosely related. In each the body, with its various organs,is built on a radiate plan of structure, the mouth being inthe center of the under side and all the body parts radiatingout from this center. THE INVERTEBRATES 141 If a starfish, either fresh or preserved in alcohol, can behad for examination, note that the body is covered by a —eye spot muscles of the pylonc caeca reproductive glands •< ur
. The animans and man; an elementary textbook of zoology and human physiology. central disk and long rays or radiating arms, and the sea-urchins looking like spiny flattened balls, they are reallyclosely related. In each the body, with its various organs,is built on a radiate plan of structure, the mouth being inthe center of the under side and all the body parts radiatingout from this center. THE INVERTEBRATES 141 If a starfish, either fresh or preserved in alcohol, can behad for examination, note that the body is covered by a —eye spot muscles of the pylonc caeca reproductive glands •< urdiac ste»ia< It* • -intestinal caecum. muscles, of the pyloric caeca eye spot - - FiG. 58. Dissection of a starfish (Asterias sp.). skeleton composed of little plates, on which are short stoutspines arranged in irregular j-ows. At the tip of each armor ray there is a small red speck, the very simple eye of the 142 THE ANIMALS AND MAN animal. The starfish cannot see with this eye; it canonly distinguish between light and darkness. On the underside the mouth is in the center, and from it along each rayruns a groove. In each groove may be seen two doublerows of soft, tubular processes with sucker-like tips calledthe tube-feet. These are the organs of locomotion. Iflive starfishes can be watched the slow locomotion by meansof the tube-feet may be seen, and perhaps also the peculiarmode of taking food. Starfishes are carnivorous, feedingon crabs, snails, and the like. If the live prey is too largeto be taken into the mouth it is surrounded by the stomach,which is pushed outward for this purpose. It secrets fluidswhich kill the
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