86 PLANARIA ARETHUSA. 



ills, or by their numerous dispersion singly 

 around the margin of the Nigra, Pannicu- 

 lata, or Felina. Two specks, as if in orbits, 

 occupying the middle of the neck, or four 

 distributed in a regular quadrangle in the 

 vicinity of the head, seem to denote a spe- 

 cial purpose relative to external objects. 

 In nothing is there greater diversity than 

 in the disposal, power, and faculties of the 

 organs of vision among the inhabitants of 

 the air, the earth, or the waters. They 

 are adapted either to aid the discovery and 

 capture of prey, to shun the enemies of the 

 race, or to that peculiar medium in which 

 their natural dwelling has been assigned. 



In the years 1802 and 1803, a planaria 

 occurred to me of this description, which was 

 then the subject of diversified experiments. 

 But when desirous of repeating them more 

 recently, I found that it had altogether dis- 

 appeared from its wonted abode ; and being 

 unable to discover it elsewhere, a section, 

 once designed for its history as the planaria 

 rufa, shall now be suppressed, especially as 



