Animal life in the sea and on the land . Star-fishes.—Let us imagine astar-fish supported in this way upon the end of a longstalk, and we shall have a pretty good idea of a comparing the two we must invert the star-fish, how-ever, as the mouth of a crinoid is on the upper surface,whereas in the other echinoderms the mouth is underneath. CRINOIDS, OR STONE-LTLIES. 71 The tube-feet, like-wise, are on the up-per surface of thearms, but they arenot used for travel-ling about as thetube - feet of otherechinoderms grooves contain-ing them are coveredwith cilia which cre-ate curren
Animal life in the sea and on the land . Star-fishes.—Let us imagine astar-fish supported in this way upon the end of a longstalk, and we shall have a pretty good idea of a comparing the two we must invert the star-fish, how-ever, as the mouth of a crinoid is on the upper surface,whereas in the other echinoderms the mouth is underneath. CRINOIDS, OR STONE-LTLIES. 71 The tube-feet, like-wise, are on the up-per surface of thearms, but they arenot used for travel-ling about as thetube - feet of otherechinoderms grooves contain-ing them are coveredwith cilia which cre-ate currents of watertowards the mouth,and carry to it theminute plants andanimals upon whichthe crinoid feeds. 4. Skeleton of Cir-cular Plates. — Likestar - fishes and sea-urchins, these cousinsof theirs secrete limeto form a solid frame-work for their bod-ies. The lime is de-posited in circularplates, which are sur-rounded and held to-gether by living flesh,so that they bend ea-sily. You can detectthese circular platesin any part of the ac-. Fig. 43.—A Living Crinoid. West Indies. 72 ANIMAL LIFE IN THE SEA AND ON THE LAND. conipanying picture. Indeed, crinoids may be known bythe little rings of which they are composed. 5. Free Swimming Crinoids. — In some crinoids, as theComatida, or feather-star, the animal is fastened to theground only when young. Later in life it drops from thestalk, and is free after this to travel about. It can swimthrough the water; still, it prefers to remain quietly set-tled on some stone or sea-weed, waving its feathery,bright-red arms while it feeds upon the little animalsfloating around. It now resembles a star-fish more thanever, though it moves only by means of its flexible arms. 6. An Ancient Family.—The family of crinoids is veryancient, and was perhaps at one time the most numerousfamily which inhabited the sea. Like some other oldfamilies, it has almost died out. There are but few spe-cies now living, and two or three of these have been onlyr
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1887
