86 EAETHWORMS, LEECHES, AND SEAWORMS 



employed, because they produced scarcely any pain, 

 while sucking the blood. These worms are occasionally 

 used for this purpose yet and are found for sale in some 

 drug stores. Leeches are raised in France on a commer- 

 cial scale. Swamps are stocked with them, and they 

 are then fed on worn-out horses, cattle, etc. 



Certaui leeches, in India, that live on the land are great 

 pests to the natives and domestic animals. Others are 

 parasites, clinging to the bodies of fish, and one, the horse- 

 leech, is sometimes parasitic in the throats of horses and 

 cattle. Some are carnivorous, hving on the bodies of 

 snails and other mollusks. The eggs of leeches are usually 

 inclosed in cocoons. 



Seaworms. — There are many worms living in the sea. 

 Some are free-swinuning ; some crawl along the bottom ; 

 some Uve in burrows, and some in tubes. Perhaps the 

 majority of marine worms are found in shallow water along 

 the shores of the sea, although some have been dredged 

 from depths of over three thousand fathoms. 



The tube-btiilding seaworms are interesting creatures. 

 Most of them lead a sedentary or fixed hfe. The tubes of 

 some are formed from hardened mucus secreted by special 

 glands of the body. Others make their tubes from grains 

 of sand or mud or even from fragments of shells stuck to- 

 gether with mucus. A few are free and actually carry 

 their tubes about with them. 



Progression. — The earthworm and leech are probably 

 the highest animals we have met so far. In the first place 

 the bodies of both are truly segmented. That is, the cavity 

 between the aUmentary canal and the bodj'^ walls, known as 

 the coelome, is divided into compartments by cross-parti- 

 tions. Bear in mind that they are the first animals we have 



