214 SEGMENTED WORMS OR ANNELIDA. 



Give, Give," are species of Hcemopis, greedily suctorial 

 though their teeth are too small to be useful in blood- 

 letting ; but the popular name is also applied to species of 

 the common genus Aulastoma, whose members are car- 

 nivorous. Other common leeches are species of Nephelis, 

 predacious forms with indiscriminating appetites, and the 

 little Clepsine, also common in our ponds, notable for its 

 habit of carrying its young about on its belly. Numerous 

 marine forms prey upon fishes and other animals, e.g., the 

 " skate sucker " Pontobdella, with a leathery skin rough with 

 knobs, and Branchellion on the Torpedo, remarkable for 

 numerous leaf-like respiratory plates on the sides of its 

 body. Perhaps the strangest habitat is that of Lophobdella, 

 which lives on the lips and jaws of the crocodile. 



Type. The Medicinal Leech (Hirudo medirinalis). 



This is the commonest and most familiar of leeches, once 

 so constantly used in the practice of medicine that leech 

 became synonymous with medical practitioner. It lives in 

 ponds and sluggish streams, and though not common in 

 Britain, is very abundant in many regions of the Continent, 

 where leech farms, formerly of great importance, are still to 

 be seen. Leeches feed on the blood of fishes, frogs, and 

 the like, and are still caught in the old fashion on the bare 

 legs of the callous collector. As animals are naturally averse 

 to bloodletting and hard to catch, leeches make the most 

 of their opportunity, and feed very greedily. They gorge 

 themselves with blood and keep on slowly digesting it 

 for many months, it may be indeed for a year. Watched in 

 a glass jar, the leech will be seen to move by alternately 

 fixing and loosening its oral and posterior suckers, while 

 some slight provocation, such as some drops of chloroform 

 or alcohol, will induce the animal to swim about both 

 actively and gracefully. At times it may also be seen to 

 cast off from its skin thin transparent shreds of cuticle, a 

 process which, in natural conditions, usually occurs after a 

 heavy meal, when the animal as if in indigestion spasmodi- 

 cally contracts its body, or rubs itself on the stems of water 

 plants. Numerous eggs are laid together in cocoons in the 

 damp earth near the edge of the pool. Thence after a 



