I 1 8 THE OCEAN WORLD. 



system, heart, muscular rings, lungs, nor liver ; the organs of the 

 senses — namely, those of sight, hearing, and of smell — have also 

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

 these senses. O 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 eye, and which he attempts in vain 

 to explain ! 



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

 system, can neither extend nor contract themselves, nor can they 

 progress. 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 freshwater snail is 

 his steed ; he creeps upon the shell of a Planorbis, or a Limneus, 

 and by means of this improvised mount he will make more 

 way in a few minutes than he would in a whole day by his own 

 unassisted efforts. 



Hydra viridis, although destitute of organs of sight, is neverthe- 

 less 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, 

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

 attack where they are pretty 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 reflec- 

 tion, deliberation, and premeditated 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 larva of dipterous insects are 

 its habitual prey. When a worm or water flea in passing its tentacles 

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

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



