208 
THE OCEAN WORLD. 
senses — namely, those of sight, hearing, and of smell — have also been 
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 vain to 
explain ! 
Trcmb'ey states that the fresh-water polypes, having no muscular 
ring, can neither extend or 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 ha s 
found means of remedying it, and the aquatic snail is his steed ; b® 
creeps upon the shell of this mollusc, and by means of this improvised- 
mount he Avill make more way in a few minutes than he would in 
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 thoir prey* 
recognise, seize, and devour it. They make no blunder, and only 
attack where they are sure of success. They know how to flee fro# 1 
danger ; they evade obstacles, and fight with or fly before their enemies- 
There are, then, some powers of reflection, deliberation, and p re ' 
meditated action in these insignificant creatures ; their history, 111 
short, is calculated to fill the mind with astonishment. 
Trembley insists much upon the address which the Hydra employ 3 
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 bisects, and larva; of dipterous insects 
its habitual prey. When a worm or woodlouse in passing its portak 
happens to touch them, the polype, taking the hint, seizes upon th £ 
