206 THE OCEAN WOELD. 



denied them. Nevertheless, they act as if they possessed all these 

 senses. Oh Nature ! how hidden are thy secrets, and how the pride 

 of man is humbled by the mysteries which surround thee by the 

 spectacles which strike his eyes, and which he attempts in yam to 

 explain ! 



Trembley states that the fresh-water polyps, having no muscular 

 ring, can neither extend nor contract themselves, nor can they walk. 

 If touched, or if the water in which they are immersed is suddenly 

 agitated, they are certainly observed to contract more or less forcibly, 

 and even to inflect themselves in all directions ; and by this power 

 of extension, of contraction and inflection, they contrive to move 

 from place to place; but these movements are singularly slow, the 

 utmost space they have been observed to traverse being about eight 

 inches in the twenty-four hours. 



Painfully conscious of his powers of progression, however, he has 

 found means of remedying it, and the aquatic snail is his steed; he 

 creeps upon the shell of a Planorbis, or Limnsea, and by means of this 

 improvised mount he will make more way in a few minutes than he 

 would in a day by his own unassisted efforts. 



The Hydra viridis, although destitute of organs of sight, are never- 

 theless sensible of light ; if the vase containing them is placed partly 

 in shade and partly in the sun, they direct themselves immediately 

 towards the light ; they appreciate sounds ; they attach themselves to 

 aquatic plants and other floating bodies. Without eyes, without 

 brain, and without nerves, these animals lie in wait for their prey, 

 recognize, seize, and devour it. They make no blunder, and only 

 attack where they are sure of success. They know how to flee from 

 danger ; they evade obstacles, and fight with or fly before their enemies. 

 There are, then, some powers of reflection, deliberation, and pre- 

 meditated action in these insignificant creatures ; their history, in 

 short, is calculated to fill the mind with astonishment. 



Trembley insists much upon the address which the Hydra employs 

 to secure its prey : by the aid of its long arms, small animals, which 

 serve to nourish it, are seized, for it is carnivorous, and even passably 

 voracious. Worms, small insects, and larvae of dipterous insects are 

 its habitual prey. When a worm or woodlouse in passing its portals 

 happens to touch them, the polyp, taking the hint, seizes upon the 

 wanderer, twining its flexible arms round it, and, directing it rapidly 



