216 



THE WORMS 



The Sandworm. Other segmented worms are familiar to some of us. 



The sandworm, used for bait along our eastern coast, is a segmented worm 

 which lives 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 

 gill. 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 little 

 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 sandworm 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. 

 (Laboratory Manual, Prob. JCJCVIII.) 



Some Worms which harm Man. Some 

 mented; such are the flatworms and 

 round worms. A common leaflike 

 form of flatworm may be found cling- 

 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 benefits in return. Parasit- 

 ism is one-sided, the host giving 



worms are unseg- 



A flatworm ( Yungia Aurantiaca), 

 much magnified. From model 

 in the American Museum of 

 Natural History. 



everything, the parasite receiving everything. Consequently, the 

 parasite frequently becomes fastened to its host during adult life 



