8 PLANARIA FLEXILIS. 



what is their pecuHar use, is uncertain ; nor 

 can we determine whether the impressions 

 received, or the functions performed, rest 

 on their united operation. Their remote- 

 ness from the mouth may be thought un- 

 favourable for aiding the animal to the cap- 

 ture of its prey ; and their position so far 

 from the portion first advanced, seems ill 

 calculated for enabling it to avoid danger. 

 Naturalists are prone to ascribe the same 

 faculties to those organs of the smaller 

 tribes, which bear a distant resemblance to 

 the place and appearance of eyes in the 

 larger animals. But the precise nature of 

 vision in all aquatic and terrestrial insects, 

 and likewise in the whole mollusca and 

 vermicular race, is exceedingly obscure ; 

 and, notwithstanding our readiness to be- 

 stow it on many of them in perfection, 

 there is certainly ground to dispute, whether 

 we are acquainted with any particular organ 

 appropriated for it. Perhaps this sense is 

 not indispensible to their security or pre- 

 servation ; many animals seldom approach 



