466 ANNELIDES. 



FAMILY 11. 



ABRANCHIATiE ASETIGER^E. 



The second family consists of two great genera, both of 

 which are aquatic. 



HiRUDO, Lin. 



Leeches have an oblong, sometimes depressed, transversely plicated 

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

 furnished with a llatlened 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 animalsj 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 l)ody, and the valve is a little further 

 behind. 



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

 them with a fibrous excretion(l). 



They have been subdivided from characters principally drawn 

 from the organs of their mouth. In the 



(1) See 3I^moires pour servir a I'Hist. Nat. des Sangues, hy P. Thomas; a Me- 

 moir of Spix, Acad. Bav., 1813; and a third of M. Carena, Acad. Turin., t. XXV; 

 but especially the Systeme des Annelides, Savigny, and the MoJiographie des Hiru- 

 dines, Moquin-Tandon, Montpellier, 1826, 4to. See alsoEssai d'une Monographic 

 de hfamille des Hirudintes, extracted from the Diet, des Sc. Nat. by M. de IJlainv., 

 Paris, 1827, 8vo, and the article Sangsue of the same work, by Audouin. 



