First lesson in zoology : adapted for use in schools . FiG. 38. — Planaria torva (en-larged); and e, egg-capsule. Fig. i^.—Macrnbdella, or pond-leech.(Natural size.) (Natural size.) ment. The earth-worm is able to climb perpendicularlyup boards or the sides of buildings by minute; short, curvedbristles, which are deeply inserted in the muscular walls ofthe body, and arranged in two double rows along each side ttiE WORMS. 41 of the body. In burrowing it thrusts the pharynx into theend of the head, causing it to swell out, and thus push theearth away on all sides, while it also swallows the dirt
First lesson in zoology : adapted for use in schools . FiG. 38. — Planaria torva (en-larged); and e, egg-capsule. Fig. i^.—Macrnbdella, or pond-leech.(Natural size.) (Natural size.) ment. The earth-worm is able to climb perpendicularlyup boards or the sides of buildings by minute; short, curvedbristles, which are deeply inserted in the muscular walls ofthe body, and arranged in two double rows along each side ttiE WORMS. 41 of the body. In burrowing it thrusts the pharynx into theend of the head, causing it to swell out, and thus push theearth away on all sides, while it also swallows the dirt,?y^hich passes through the digestive canal. In this way itmay descend from three to eight feet in the soil. While earth-worms are in the main beneficial, from theirhabit of boring in the soil of gardens and ploughed lands,bringing the subsoil to the surface and allowing the air toget to the roots of plants, th»y occasionally injure youngseedling cabbages, lettuce, beets, etc., drawing them duringthe night into their holes, or uprooting them,*. Fig. 40 Transverse section through the body of a Nereis, d, dorsal vessel or heart; c. circular blood-vessel; b, ventral vessel; n, nervous cord or ganglia;/, artery to swimming appendage s; z, intestine; s, setae or bristles. The leeches (Pig. 54) are allied to the earthworm, butare adapted to a life in fresh-water ponds. Our commonest sea-worm, sometimes called the clam-worm, is Nereis virens. It lives between tide-marks inholes in the mud, and can be readily obtained. The body,after the head, eyes, tentacles, and bristle-bearing feet havebeen carefully studied, can be opened along the back by apair of fine scissors, and the dorsal and ventral red blood-vessels with their connecting branches observed, as well asthe alimentary canal and the nervous system. This worm is very voracious, thrusting out its pharynxand seizing its prey with its two large pharyngeal teeth * Darwin. Formation of vegetable mould tlirough the action of worms
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1894
