PLANARIA ARETHUSA. 89 



and is further characterised by being pro-, 

 vided with two eyes. 



On the seventeenth of September 1809, 

 I took between twenty and thirty of these 

 animals, the larger four or live lines in 

 length, and of the usual colour ; but the 

 smaller of a lighter shade, and some even 

 whitish. The diversity of hue excited em- 

 barrassment concerning the identity of the 

 latter with the species : Nor was this re- 

 moved by taking a number of the same 

 planariae, in the course of the succeeding 

 year, among which were several almost 

 white, though exactly similar to the rest in 

 size and proportions, while they were too 

 large to be considered young. Further 

 observations have shewn, that there is lit- 

 tle restriction with respect to size, some 

 being seen thus distinguished, which, if 

 not equal to the largest, are scarce infe- 

 rior to them ; and it yet remains to be ex- 

 plained, whether the paleness be acciden- 

 tal, whether it characterises an additional 

 species, or only a variety. I am rather 



