32 CLASS ANNELIDA. i 



The ganglia of the nervous cord are much more separated 

 than in the lumbrici. 



The leeches are hermaphrodites : a large penis projects 

 from under the anterior third of the body, and the vulva is a 

 little farther back. Many of them collect their eggs into 

 cocoons, enveloped in a fibrous excretion. 



They have been subdivided according to characters chiefly 

 derived from the parts of the mouth. 



SAiiGVii^VGA,Sav.,JATROBDELLA,Blainv. These are the 

 leeches properly so called ; the anterior sucker has its upper 

 lip divided into several segments ; its aperture is transverse, 

 and it contains three jaws, armed, each on its edge, with two 

 ranges of very fine teeth, which enables them to penetrate 

 through the skin without making any dangerous wound there. 

 Ten small points have been observed upon them, which are 

 taken for eyes. 



We are all acquainted with the common or medicinal leech, 

 Hirudo medicinalis^ L., so useful an instrument in local 

 bleedings. It is usually blackish, striped with yellowish 

 above ; yellowish, spotted with black underneath. It is found 

 in all dormant waters. 



H^MOPSis, Sav., differ from the last only because their jaws 

 have but a few and obtuse teeth. M. de Blaiuville calls them 

 HypohdeUa, the Horse-leech ; Hirudo sanguisuga, L. ; 

 H(B7nop. sanguisorba, Sav., Moq. Tand. pi. iv. f. 1. ; Car.pl. 

 xl, f. 7. ; much larger, and altogether of a greenish black. It 

 has been reported to be sometimes dangerous, from the wounds 

 which it inflicts. 



The difference of opinions as to the power of the horse- 

 leech to draw blood is very singular. Linnaeus says that 

 nine of them can kill a horse. MM. Huzard and Pelletier, 

 on the contrary, in a memoir lately presented to the Institute, 

 and inserted in the Journal de Pharmacie, March, 1825, as- 

 sure us that it never attacks a vertebrated animal. M. de 



