59 



CLASS I ANNELLATA. 



LEECHES, EARTH-WORMS, ETC. 



Her divine skill taught me this, 



That from everything I saw 



I could some instruction draw, 



And raise pleasure to the height, 



Through the meanest object's sight." -G. WITHER. 



THE most obvious external character of the Leech or the 

 Earth-worm is the number of little rings of which the body is 

 composed; and hence the Latin word "annelhis," a little ring, 

 suggests an appropriate and descriptive term for animals of 

 this class. 



The medicinal Leech and the common Horse-leech of our 

 ponds are so well known, that the most incurious cannot fail, 



Fig.. 38 LEECH. 



at some period or other, to have noticed the singular disc 

 with which these creatures are furnished at each extremity of 

 the body, and which, at the will of the animal, can be used 

 as a sucker, and thus converted into a support or point of 

 attachment. Leeches are of many species; but these pre- 

 hensile discs may be regarded as "the badge of all the tribe." 

 They are destitute of external organs for locomotion, and move 

 by the expansion and contraction of the segments of the body. 

 In the 'water they can swim with ease and rapidity. Kespi- 

 ration is effected by a series of membranous sacs, which are 

 analogous to internal gills, and to which water is freely ad- 

 mitted by minute orifices on the lower surface of the body.* 



The medicinal Leech (Hirudo medidnalis) is not indigenous 

 to Ireland ; it is found in some parts of Britain, but is now 

 becoming very rare. It is still seen in the lakes of Cumbcr- 



* Jones's Nat. Hist, of Animals. 



