RADIATA. 
511 
Two transverse sections brought into contact will quickly 
unite and form one animal, though each section belong 
to a different species. The head of one species may be 
engrafted on the body of another. When one Polype is 
introduced by the tail into another's body, the two heads 
unite and form one individual. Pursuing these strange 
operations, M. Trembley gave scope to his fancy by 
repeatedly splitting the head and part of the body ; he 
thus formed hydras more complicated than ever struck 
the imagination of the most romantic fabulists. 
Though so difficult to destroy by division, all the 
Polypes, even those which form the corals, may be easily 
killed by keeping them dry ; as when this is the case they 
soon shrivel up, and the tissue of their skins is completely 
destroyed. 
