22 PLANARIA FLEXILIS. 



was probably hastened by their artificial si- 

 tuation. 



The Planaria Flexilis is one of those be- 

 ings so eminently privileged, as to preserve 

 animation when divided into sections : If 

 cut asunder, each half acquires the de- 

 fective organs. At first the posterior 

 portion is quiescent ; and a considerable in- 

 terval elapses before its motion and activity 

 are resumed : the anterior division suffers 

 little ; it traverses its element as if scarce 

 affected by the mutilation ; a thin triangu- 

 lar vegetation proceeds froln the wound, 

 which is gradually enlarged, and at last ac- 

 quires the exact figure and proportions of 

 the severed parts. 



The longest period during which I have 

 at once preserved these marine Planaria^, 

 has exceeded eight months. As accident 

 then deprived me of them, we are not to 

 conclude on the brevity of their existence. 

 Indeed, the life of most aquatic animals is 

 by no means short ; and perhaps the ter- 

 restrial molluscae, and some apterous in- 



