PI.ANARIA FLEXILI3. IS 



numerous pinnate and delicate shaped ves- 

 sels performing the functions of nutrition. 



But the naturalist cannot be sufficiently 

 guarded against yielding to appearances : 

 none are better calculated to mislead his 

 judgment than those which are now exposed. 

 I have oftener than once taken planariae of se- 

 veral kinds, embellished by complicated rami- 

 fications below, and above exhibiting a tinge 

 different from what had been seen in any 

 other species. Neither did their size corre- 

 spond with the dimensions of those which 

 might be deemed most analogous; and I even 

 thought there was a sensible peculiarity in 

 their motion. These facts would have war- 

 ranted the addition of another species, or at 

 least a variety to the genus ; yet, having 

 preserved the individuals a day or two, an al- 

 teration both of figure and colour augment- 

 ed the difficulty of condescending on their 

 proper place, until the further lapse of time 

 brought them to my knowledge as animals 

 quite ordinary and familiar. Whence did 

 the discrepancies arise ? From the quality 



