The royal natural history . ~^m X- 1 m :/,. SEA-CUCUMBERS AND A BRITTLE-STAR. ?.g2 ECHINODERMS. rnps tube-feet; but sometimes they end in a point, and cannot assist in locomotion,though they may help respiration, when they are sometimes called a single foot be touched, it immediately shrinks up, and if the touch bevigorous, the adjacent tube-feet probably follow its example. Tube-feet torn fromthe animal sometimes continue their waving motion, showing that this is, partlyat least, due to muscular action. Their movements are also caused by the squeezingof a fluid into them; for eac
The royal natural history . ~^m X- 1 m :/,. SEA-CUCUMBERS AND A BRITTLE-STAR. ?.g2 ECHINODERMS. rnps tube-feet; but sometimes they end in a point, and cannot assist in locomotion,though they may help respiration, when they are sometimes called a single foot be touched, it immediately shrinks up, and if the touch bevigorous, the adjacent tube-feet probably follow its example. Tube-feet torn fromthe animal sometimes continue their waving motion, showing that this is, partlyat least, due to muscular action. Their movements are also caused by the squeezingof a fluid into them; for each foot is like an indiarubber tube closed at the end,and passing through the test (as the shell of the sea-urchin is termed) to join withone main tube, which runs along under the ambulacrum in a radial direction ; andbefore it joins this radial canal, each tube-foot gives off a small swelling likewisefilled with fluid, so that when this swelling is contracted all the fluid is squeezed up into the foot, and pushesit out like the finger of a
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Keywords: ., bookcentury1800, booksubjectnaturalhistory, booksubjectzoology
