70 THi: VITAL 1 UNCTIONS. 



Stomach of another hydra, was not in any degree 

 acted upon by the fluid secretions of that organ, 

 but came out uninjured. It often happens that a 

 hydra in its eagerness to transfer its victim into 

 its stomach, swallows several of its own tentacula, 

 which had encircled it ; but these tentacula always 

 ultimately come out of the stomach, sometimes after 

 having remained there twenty-four hours, without 

 the least detriment. 



The researches of Trembley have brought to 

 light the extraordinary fact that not only the in- 

 ternal surface of the stomach of the polypus is en- 

 dowed with the power of digesting food, but that 

 the same property belongs also to the external 

 surface, or what we might call the skin of the 

 animal. He found that, by a dexterous manipu- 

 lation, the hydra may be turned inside out, like the 

 finger of a glove ; and that the animal, after having 

 undergone this violent evertion, soon recovers the 

 power of performing its o^linary functions, just as 

 if nothing had happened. It accommodates itself, 

 in the course of a day or two, to the transformation, 

 and resumes all its natural habits, eagerly seizing 

 animalcules with its tentacula," and introducing 

 them into its newly formed stomach, which has for 

 its interior surface what before was the exterior 

 skin, and which digests them with perfect ease. 

 When the discovery of this curious phenomenon 

 was first made known to the world, it excited great 

 astonishment, and many naturalists were incre- 

 dulous as to the correctness of the observations. 

 But the researches of Bonnet and of Spallahzani, 

 who repeated the experiments of Trembley, have 

 borne an)ple testimony to their accuracy, which 



