Natural history of animals; . Fig. 463. — Sea Urchin. in form and firmly bound together. Upon these platesare tubercles, and on these tubercles hard spines. In SEA URCHINS. 235 certain plates there are rows of holes through whichpass fleshy organs called suckers, or ambulacral feet,with the end slightly expanded. By means of thesesuckers, which can be extended much beyond thespines, these animals can cling firmly to other bodies,and thus move about over the rocks, even up anddown their smooth sides, as well as on level much can these suckers be extended that a SeaUrchin has been se
Natural history of animals; . Fig. 463. — Sea Urchin. in form and firmly bound together. Upon these platesare tubercles, and on these tubercles hard spines. In SEA URCHINS. 235 certain plates there are rows of holes through whichpass fleshy organs called suckers, or ambulacral feet,with the end slightly expanded. By means of thesesuckers, which can be extended much beyond thespines, these animals can cling firmly to other bodies,and thus move about over the rocks, even up anddown their smooth sides, as well as on level much can these suckers be extended that a SeaUrchin has been seen to put them forth from the top,and, bending them downwards, cling to the bottom ofthe basin in which the animal was lying. Figure 463shows a common kind of Sea Urchin as it appearswhen alive. When the animal dies, the skin, whichcovers the shell and holds the spines in their places,. Fig. 464. — Top view of Sea Urchin. Spines removed. dries up, and the spines fall off, and then the shell,with all its beautiful structure and markings, is plainlyseen. In the one represented in Figure 464 we findten double rows of plates which run along the curvedsurface from the bottom to the top of the shell. Infive of these double rows the plates are large, with-out holes, and are covered with large tubercles. Al-ternating with the double rows of large plates are fivedouble rows of smaller ones, bearing few and small 236 ECHINODERMS. tubercles, and each plate is perforated with the holesfor the suckers. The plates which bear the holes arecalled the ambidacralplates, — from a Latin word whichmeans a walk, or alley; and the large plates withoutholes are called the inter ambidacral plates. At thetermination of each of the five belts or zones of ambu-lacral plates there is a little triangular plate with aminute opening which marks the place of the with these ocular
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
