PLANARIA ARETHUSA. 101 



meet the head ; sometimes it curves over 

 the back ; and in those mutilated by spon- 

 taneous division, it may be seen issuing far 

 behind, in a direction diametrically opposite 

 to the ordinary site of the mouth of ani- 

 mals. On supplying a portion of flesh, the 

 trunk is immediately buried among its fi- 

 bres; or if the planaria can find a worm suf- 

 ficiently small, it is slowly and gradually ab- 

 sorbed, the proboscis ensheathing it by a cy- 

 linder half as long as the body. Should a 

 number fix on the same object, their trunks, 

 all in action, and greatly extended, are often 

 curiously intertwined; for each is stretched 

 out by the planaria on becoming sensible of 

 the presence df food, while it remains sta- 

 tionary itself at a considerable distance. It 

 is exceedingly interesting, also, to witness 

 the immediate dissemination of soft alimen- 

 tary substances absorbed by the proboscis, 

 bringing the delicate interanea into view, 

 and changing the hue of the animal ; nor 

 is it less singular to contrast the milky 

 whiteness of the organ with the body of 



