316 THE AQUARIAN NATURALIST. 



arrangement as may be fitted to collect the rays of 

 light, it is difficult to form any conception of the 

 nature of sight in these animals, if this endowment 

 really is conferred upon them. Still it is not essential 

 to the practical purposes of the lowest forms of life that 

 the objects of the external world should be seen, that 

 pictures of them should be painted upon the retina ; 

 it were enough that the mere presence or absence 

 of an objective body should become evident to the 

 sensations of the animal by the positiveness or nega- 

 tiveness of the impressions received. A refinedly 

 exalted sense of touch would suffice to accomplish this 

 object. It is not easy for those who have never en- 

 joyed the spectacle of the " feat of touch/' performed 

 by the tentaculated worms, adequately to estimate the 

 extreme acuteness of the sensibility that resides at the 

 extremities of the living threads with which the head 

 and sides of the body are garnished. They select, 

 reject, move towards, and recede from, minute ob- 

 jects with all the precision of animals gifted with the 

 surest eagle sight, and steer themselves harmlessly, 

 readily, and unerringly through the thickly tangled 

 labyrinth of mud, and stone, and gravel, and weed, 

 amid the twilight of which the habitat of many of 

 them may have been cast. 



The same author observes, that it is a remarkable 

 fact in the history of the free Annelidans, that scarcely 

 any species, however organized, whether furnished or 

 riot with external locomotive organs, in its numerous 

 and varied muscular evolutions ever moves directly 

 backwards. Their movements consist always of ser- 

 pentiform pranks, or those of elaborate coiling. It 



