ABRANCHIATE. 143 



FAMILY II. 



ABRANCHIATE ASETIGEIUE. 

 The second family consists of two great genera, both of which are 



aquatic. 



HIRLDO, Lin. 



Leec an oblong, sometimes depressed, transversely plicated 



body; the mouth is encircled by a lip, and the posterior extremity 

 furnished with a flattened disk, both of which are well adapted for 

 adhering to bodies by a sort of suction, and are the principal organs 

 of locomotion possessed by these animals; for after extending itself, 

 the Leech fixes its anterior extremity and approximates the other, 

 which in its turn adheres to allow the former to be carried forward. 

 In several we observe on the under part of the body two series of 

 pores, the orifices of as many small internal pouches, considered by 

 some naturalists as organs of respiration, although they are usually 

 filled with a mucous fluid. The intestinal canal is straight, inflated 

 from space to space, for two-thirds of its length, where there are two 

 caeca. The blood swallowed is preserved there, red and unchanged, 

 for several weeks. 



The ganglions of the nervous cord are much more separate than in 

 the Lumbrici. 



The Hirudines are hermaphrodites. A large penis projects from 

 under the anterior third of the body, and the valve is a little further 

 behind. 



Several of them form their eggs into a cocoon, and envelope them 

 with a fibrous excretion *. 



They have been subdivided from characters principally drawn 

 from the organs of their mouth. In the 



SANGUISUGA, Sav.] 



Or the Leech properly so called, the superior lip of the anterior 

 cup or sucker is divided into several segments ; the aperture is trans- 

 verse and contains three jaws, each edge of which is armed with two 

 rows of very fine teeth, which enables them to penetrate through the 

 skin without causing a dangerous wound. It is marked with ten 

 small points, considered as eyes. 



We all know the medicinal or common Leech Hirudo me- 

 dicinalit, L., that usefni instrument for the local abstraction of 



See Mtmoires pour servir a VHitt. Nat. dt$ Sangves, by P. Thomas ; a Memoir 

 of Spiz, Acad. Bav., 1813 ; and a third of M. Catena, Aead. Turin., t. XXV ; but 

 especially the Sysfcmc des AnnMidcs, Savigny, and the Monographic des Hirudines, 

 Moquin-Tandon, Montpellier, 1 836, 4to. See also Esssai d'unc Monographic de la 

 ftmflh de* Hirudines, extracted from the Diet, des Sc. Nat. by M. de Blainv., 

 Paris, 1827, 8vo., and the article SANGSUE of the same work, by Andouin. 



f M. de Blainville changes this name into JATROBELLA. For the various medi- 

 cinal Leeches, see the fig. of Messrs. Carena, Acad. Turin., t. XXV, pi. xi, and Mo- 

 quin-Tandon pl.y. 



