. Essentials of biology presented in problems. Biology. 216 THE WORMS The Sandwonn. — Other segmented worms are familiar to some of us. The sandworm, used for bait along our eastern coast, is a segmented worm which hves between tide marks in sandy localities. It is plainly segmented, each segment bearing a pair of loco- motor organs called parapodia (meaning side feet). A part of each parapodium is prolonged into a triangular giU. The animal has a distinct head, which is provided with tentacles, palps, and eye spots. The mouth has a pair of hard jaws which may be protruded. In this way the ani
. Essentials of biology presented in problems. Biology. 216 THE WORMS The Sandwonn. — Other segmented worms are familiar to some of us. The sandworm, used for bait along our eastern coast, is a segmented worm which hves between tide marks in sandy localities. It is plainly segmented, each segment bearing a pair of loco- motor organs called parapodia (meaning side feet). A part of each parapodium is prolonged into a triangular giU. The animal has a distinct head, which is provided with tentacles, palps, and eye spots. The mouth has a pair of hard jaws which may be protruded. In this way the animal seizes and draws prey into its mouth. The sandworm swims near the surface of the water, the body bending in graceful undulations as the parapodia, like Httle oars, force the worm forward. They spend much of the time in tubes in the sand, which are constructed in part of slime excreted from the body of the worm. The Leech. — The common leech or bloodsucker Is a flattened segmented worm, inhabiting fresh-water ponds and rivers. The adult is provided with two sucking disks, by means of which it fastens itself to objects. The mouth is on the lower surface close to the anterior disk. Loco- motion is accomplished by swimming; or by means of the suckers, somewhat after the manner of a measuring worm. They feed greedily and are often found gorged with blood, which they suck from the body of the victim. The sandwonn Discomfort, but no danger, attends the bite of the blood- (nereis). sucker, so dreaded by the small boy. Problem XXVIII, A study of some, animal associations. ULahoratory Manual, Proh. JC^YVIII.) Some Worms which harm Man. — Some mented; such are the flatworms and roundworms. A common leaflike form of flatworm may be found chng- ing to stones in our fresh-water ponds or brooks. Most flatworms are, how- ever, parasites on other animals; that is, they obtain food and shelter from some other living creature, but give them no beneflts in return. Parasit- one-sided, the
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