CLASS VI. ANNELIDA: ORDER 4. SUCTORIA. 



619 





THE LEECH. 



ORDER 4. SUCTORIA. 



The animals belonging to tliis order, of which the Common Leech is a familiar example, are 

 characterized by the total deficiency of any lateral appendages, their motions being effected by 

 undulations of the body while swimming, or by the alternate attachment of the sucking discs 

 with which the two extremities of their bodies are usually furnished. They all appear to live 

 by sucking the blood of other animals, and, for this purpose, the mouth of the leech is furnished 

 with an apparatus of horny teeth, by which they bite through the skin. There are several species, 

 nearly all of which are hermaphrodite. The deposition of the eggs is attended with some very 

 singular circumstances. At the period. of oviposition a peculiar gelatinous band is produced 

 round the anterior part of the body. The leech lays its eggs in this gelatinous matter, and 

 when all are deposited, it withdraws its body from the band, which then closes up, and forms 

 a complete capsule, within which the eggs are inclosed. It appears, however, that the leech 

 also sometimes produces a compound egg, formed of a transparent membrane, full of a liquid in 

 which little globules soon begin to appear ; these globules are, in fact, so many germs of leeches, 

 and during development take the form of little worms, which soon leave the egg by an opercular 

 hole at its extremity. 



The use of the Common Leech, Sanguisuga officinalis, for medical purposes is enormous ; 

 three millions are annually used in Paris, and one hundred millions in France; seven millions 

 two hundred thousand are annually imported by four dealers in London. The English leeches 

 are chiefly derived from Sweden, Poland, and Hungary; the French from the frontiers of 

 Turkey and Russia. 



The small leeches, about an inch and a half long, which infest damp places in Ceylon, often 

 creep upon the legs of travelers, who are first warned of their presence by the flow of blood 

 through their clothes. The soldiers of Napoleon in Egypt were tormented by leeches thronging 

 the pools, which fixed themselves in their mouths and nostrils as they stooped to drink. 



The species of the genus Piscicola live as parasites on fresh-water fishes. 



The animals of the genus Sijmnculus and their allies, form the order of Oephyrea of some 

 naturalists ; they are marine, their bodies are cylindrical, and their habits are similar to those 

 of the lob-worm. They are destitute of eyes and other organs of sense. 



