LEECH, GORDIUS. CLASS OF ENTOZOA. 313 



be extremely imperfect. The greater number of the Leech tribe 

 are inhabitants of fresh water ; some, however, are only found 

 in the sea ; others live in moist situations near stagnant water, 

 pursuing Earth- Worms, &c. ; and there is one small species, 

 entirely terrestrial, which inhabits the woods of -Ceylon, and 

 attacks men and horses that are passing through them, in such 

 a manner as to become, from its great voracity, one of the most 

 troublesome pests of that fine island. 



849. As connecting this order with the next, we may here 



place the genus Gor- 

 dius, a long thread- 

 like Worm, scarcely 

 exhibiting any marks 

 of articulation on its 

 FIG. 533.-GORDIUS AQUATICUS. body, and having no 



distinct respiratory or- 

 gans. Its various species inhabit fresh and stagnant waters, 

 mud, and marshy grounds ; and are commonly found with their 

 long bodies coiled up into complex knots, whence the name of 

 the genus. The mouth is a simple pore at the anterior extremity 

 of the body, which is conical ; the tail, on the other hand, which 

 has been mistaken for the mouth, is bifid (Fig. 533, ). 



CLASS OF ENTOZOA. 



850. This class derives its name from the peculiar mode of 

 existence of the animals composing it; most of them being 

 inhabitants, during their whole lives, of the bodies of other 

 animals, generally of higher organisation, from the juices of 

 which they derive their nourishment. Many of these possess a 

 distinct worm-like form (Fig. 534) ; the body being much pro- 

 longed and exhibiting a division into segments, and the mouth 

 being situated at one extremity. These, therefore, evidently 

 belong to the Articulated series. There are others, however, 

 which, in their general form, the simplicity of their organisation, 

 and the circular arrangment of the organs about the mouth, seem 

 to approximate more to the Radiata (Fig. 536). 



