2 HIEUDO. 



genus Hintdo, which cannot but be interesting to the physiologist, and 

 assuredly deserve to be farther known and suitably appreciated. 



I might have been deterred from offering farther observations on 

 this, a very interesting subject in Natural History, considering the 

 valuable treatises already published by such distinguished authors as Dr 

 James Rawlins Johnson, Professor Stefano Delle Chiaje of Naples, M. 

 Moquin Tandou of Montpellier, and many others, wherein a historical 

 and descriptive view of the whole is taken, especially by the last. But 

 certain species, both marine and fresh-water, have occurred to me, which 

 seem rarely distributed. Besides, my endeavours to preserve all animals 

 alive, afford opportunities of presenting several new facts in the history 

 of some, and accurate representations of the form of others. 



There is nothing in the whole circle of literature which has hitherto 

 experienced so total a failure as the last. I cannot specify a single 

 treatise containing even tolerable figures of the Leech ; and although 

 very familiar with various species named by different authors, it is very 

 rarely that I have derived any assistance from the figures offered in 

 illustration, or have been able to identify them with my own. This 

 defect, however, must be ascribed equally to the imperfection of the 

 creature, which is not selected while vigorous, and to the deficiencies of 

 the artist. 



Many doubts have been expressed regarding the just position of the 

 Leech in the *Sy sterna Nature?., and sometimes by those who apparently 

 question whether .there is any specific order or arrangement of things 

 manifested by the Creation. Yet the tribe of leeches is, if I may so ex- 

 press it, absolutely sui generis ; none other has been hitherto shewn in 

 close approximation. It seems to stand apart. At present it is brought 

 nearer to the simple Vermes than either its general formation or its 

 general habits sanction. But there being many reputable works, which 

 I have not been able to procure, on the subject, probably they contain 

 sufficient illustrations. 



The Leech is a soft bodied, elongated, annulose animal, of the most 

 variable form. Both extremities dilate, in each constituting a sucker, 

 affixing it firmly to any foreign substance. It cannot advance unless the 



