ZOOPHYTES. 135 



secure foothold, numerous minute creatures which appear, 

 when viewed with the unassisted eye, like miniature flowers, 

 either of a brownish or, more commonly, of a green color, 

 the latter of which is called Hydra viridis. It is called 

 Hydra, on accouut of some fancied resemblance to the 

 many-headed creature of mythology bearing that name. 

 The fresh-water Hydra, however, has really but one head, 

 and the other members that appear like heads, are but the 

 arms or tentacles that I have spoken of before, arranged 

 in a circle around the mouth. This green species of Hydra. 

 has been called viridis, on account of its green color, and 

 was supposed to have the power of stinging other animals ; 

 but this is a mistake, as we shall see, when we come to 

 consider the sea Anemones. If we should take one of 

 these curious little Hydras, and cut it transversely through 

 its body, we shall find, that the part that bears the head 

 will form for itself a new body and foot ; while, from the 

 other portion which is but a body and foot, will grow a 

 new head and tentacles. We can also cut a Hydra longi- 

 tudinally in several pieces and each portion will supply 

 itself with the wanting parts, and become a perfect animal. 

 We can turn it inside out, and the part that was the lin- 

 ing of the stomach will become the exterior skin or cuticle; 

 and the cuticle will take upon itself the offices of the 

 stomach. And like experiments can be made on sea Anemo- 

 nes with similar results, but they are, as a general rule, 

 more tender than their fresh -water relations ; and, indeed, 

 there are many of the species that will certainly die under 

 the operation ; for we find that on separating them from 

 the rock to which they are attached (if we are not very 



