18 THOUGHTS ON ANIMALCULES. 



IV. 



THE DIVISIBILITY OF VITALITY. 



THE most extraordinary vital endowment possessed 

 by the Fresh-water Polype, is that of the reproduction 

 of lost parts to an almost unlimited extent, even to the 

 formation of several perfect individuals from the divided 

 parts of a single Hydra. If a polype is cut across trans- 

 versely, the upper part with the arms quickly produces 

 a new body and tail ; and the lower portion as rapidly 

 throws out another body and arms. If the body is slit 

 down longitudinally, and left united at the base, each 

 portion grows into an entire polype, the requisite num- 

 ber of arms shoot out, and two perfect animals attached 

 to one common base are produced ; and, if the division 

 be complete, two free hydrae are the result. One polype 

 was cut into ten pieces, and each piece grew into an entire 

 animal. If a polype is turned inside out, a transmuta- 

 tion not less wonderful, physiologically considered, than 

 the above process takes place : the original outer surface 

 performs the function of digestion, while the former 

 lining of the stomach becomes the external integument 



