STEBELM1NTHA. 



89 



placed a little anterior to the orifice which leads to the female 

 parts ; it is a short spiral filament, distinctly traversed by a canal, 

 and perforate at the extremity, so as indubitably to perform the 

 office of an instrument of intromission. 



(119.) The PLANARI.-E, although they do not inhabit the interior 

 of other animals, are so nearly allied in every part of their organi- 

 zation with, the Flukes, (Distoma,) that their history cannot be 

 more appropriately given than in this place. The Planarise are 

 common in ponds and other stagnant waters ; they are generally 

 found creeping upon the stems of plants, or amongst the healthy 

 confervse which abound in such situations, and wage perpetual 

 war with a variety of animals inhabiting the same localities. The 

 body of one of these minute creatures appears to be entirely 

 gelatinous, without any trace of muscular fibre ; * yet its motions 

 are exceedingly active, and it glides along the plane upon which 

 it moves with a rapid and equable pace, of which the observer 

 would scarcely expect so simple a being to be capable ; or, by 

 means of two terminal suckers, progresses in the manner of a 

 leech. No agglomeration of nervous fibre has hitherto been sa- 

 tisfactorily detected in the Planarise ; nevertheless, many species 

 possess two red specks 

 upon the anterior part 

 of the body, which, as 

 in other cases, have 

 been unhesitatingly 

 pronounced to be eyes, 

 although their claim 

 to such an appellation 

 is not only unsubstan- 

 tiated by any proofs 

 derivable from their 

 structure, but com- 

 pletely negatived by 

 experiments, which go 

 to prove that in the 

 pursuit of prey no 

 power of detecting 

 the proximity of their 

 food by the exercise of 

 sight is possessed by 

 any of them. 



* Duges, Annales des Sciences Nat. 



Fig. 39. 



