THE DIVISIBILITY OF VITALITY. 19 



or skin; the animal apparently suffering no incon- 

 venience from the operation. 



The discovery of this marvellous power of reproduction 

 in the Hydra, was made about a century since by a M. 

 Trembley, then residing at the Hague, who, in the 

 course of some researches for small aquatic insects, was 

 struck with the apparently spontaneous movements of 

 some delicate fibres which he supposed were the roots or 

 tendiils of plants growing in the water. Finding that 

 these fibres contracted when touched, and extended them- 

 selves again if left undisturbed, he at first surmised that 

 their motions were analogous to those of the sensitive 

 plant ; for the bodies in question were so unlike anything 

 at that period recognised as belonging to the animal king- 

 dom, that their true character was not suspected. Re- 

 peated observations, however, convinced M. Trembley 

 that these movements were much more active than any 

 apparent in vegetables, and he was greatly perplexed as 

 to their real nature ; he, therefore, resolved to submit the 

 supposed plants to an experiment, which he naturally 

 thought must be conclusive. Accordingly he selected 

 several specimens detached from the stem of a plant, and 

 cut them to pieces, leaving them, after the subdivision, 

 in a glass with water, and then patiently and cautiously 

 watched the result. To his utter astonishment, each 

 portion preserved its vitality, and grew up into a perfect 



c2 



