484 HABITS OF HYDRA. 



succeeds in obtaining its supply ; for if, in their active course- 

 any of these animals should but touch one of the tentacula, its 

 doom is sealed ; it is immediately seized by it ; other arms are 

 soon coiled round it ; and the unfortunate victim is speedily 

 conveyed to the mouth. It has been noticed that, if held for a 

 little time in the arms without being swallowed, soft-bodied 

 animals (such as worms) always die, even when released alive ; 

 whence it has been inferred, with some plausibility, that the 

 spines are the means of conveying into the prey some poisonous 

 secretion, in the same manner as the poison-fang of the Serpent, 

 or the sting of the Bee. Upon minute Crustacea and other hard- 

 shelled animals, however, this secretion appears to have no power. 

 Such animals are often swallowed alive, and their movements 

 within the stomach may often be perceived for some little time ; 

 but, their life being at last destroyed, the process of digestion 

 goes on very rapidly. The transparency of the membrane 

 which composes the stomach, at first permits the outline of the 

 animal to be clearly seen. The film over it gradually becomes 

 turbid, however, and the outline of the animal indistinct ; until, 

 at last, its form is wholly lost. The soft parts are completely 

 dissolved; and the harder indigestible portions are rejected 

 through the mouth. This is, at least, the case with regard to 

 the larger masses; the more finely-divided parts seem to be 

 expelled through a small orifice at the opposite extremity of the 

 cavity, evidently corresponding with that which, in the com- 

 pound Hydraform Polype, opens into the tube that connects all 

 the individuals by a common circulation ( J 056). It would 

 seem that Animal matter is more readily dissolved than par- 

 ticles of Vegetable structure. 



1046. It not unfrequently happens that, in the process of 

 swallowing, the Hydra draws in its own arms, which are coiled 

 round its prey. The digestive process never seems to affect 

 them, however, in the slightest degree ; even though they remain 

 thus inclosed during the whole period of the solution of the 

 food. Trembley, the first discoverer of these Hydras, to whose 

 accurate description of their habits scarcely anything has been 

 added by subsequent observations, once witnessed a very curious 



