PLANARIA GRAMINEA. 117 



of the smaller eyes, and naturalists ought 

 not hastily to conclude that those exposed 

 at the first glance, or even by a moderate 

 magnifier, are all which that singular ani- 

 mal possesses. The voluntary contraction 

 that every portion is highly susceptible of, 

 and the casual obscuration of parts by in- 

 tervening shades, tend to withdraw the mi- 

 nuter organs from observation. If the two 

 black specks of the planaria graminea be 

 designed for the purposes of vision, as their 

 position and appearance would indicate, 

 their operation is assuredly of a different 

 kind from that of the eyes of terrestrial ani- 

 mals. Sometimes these planariae rush 

 against obstacles which they are apparent- 

 ly desirous of avoiding ; nor when two are 

 close together, do they always seem sensi- 

 ble of their mutual presence, and on acci- 

 dental contact, they suddenly contract, and 

 reciprocally retreat in alarm. The whole bo- 

 dy, which is scarce two lines in length, and 

 half as thick, in the middle, where perfect- 

 ly round, is invested with a thin transpa- 



