POLYPI. GELATINOSI. 405 



cles or arms are usually extended in search of prey, 

 and as we have seen before in other cases, the instant 

 some little Water-flea, or Bloodworm, or Gnat-grub, 

 touches one of them, its doom is sealed, it is fixed as 

 if by magic to the almost invisible thread, in spite 

 of its struggles to escape ; the tentacle then gradually 

 contracts, and others coming in contact with the 

 victim, it is soon drawn to the mouth and forced into 

 the sac. From the transparency of the Hydra, the 

 swallowed prey may be distinctly seen in its sto- 

 mach ; if watched, it is seen to become gradually 

 indistinct in its outline, passing into the form of a 

 slight cloudy mass, until at length it totally disap- 

 pears, except any indigestible portion, such as the 

 shell of a Crustacean, which is disgorged from the 

 mouth. Although the process of digestion is ener- 

 getic and rapid, it does not act on any part of the 

 animal itself; the tentacles of the long-armed Polype, 

 are frequently passed into its own stomach coiled 

 around its victim, where they remain until it is 

 digested, without injury ; and what is more singular 

 still, a living Polype may be swallowed by another 

 with impunity. M. Trembley once saw an amusing 

 proof of this : two Hydra had seized the same prey, 

 and each had begun to swallow it at opposite ends : 

 after a little tugging, the larger of the two, opening his 

 mouth with an unusual effort, fairly swallowed his 

 opponent, worm and all. The observer reasonably 

 supposed that the engulphed Polype was (< but a 

 gone monster " now : but no ; after remaining 

 snugly lodged until the two had digested the worm 



