510 A WONDERFUL ORGAN. 



with the office the shark is appointed to discharge in the 

 economy of the great deep. 



A very curious feature in the organization of the oceaii- 

 monster is its eye, though its structure is founded on simple 

 principles when compared with that of other animals. We 

 know that most fishes have round, prominent, and as it 

 were sleepless eyes ; eyes which never close, either in sleep 

 or at the approach of danger. But in the sharks, at least 

 in the majority, the exposed surface is rendered oval by 

 means of an arrangement of the skin above and below the 

 globe, which, when the fish is in any way imperilled, closes 

 over the eye, in much the same manner as the eyelids of 

 birds. The globe itself is supplied with muscles to regu- 

 late its actions, and its sphere of action is further ex- 

 tended by means of a contrivance which furnishes a 

 remarkable instance of the adaptation of an already 

 existing mechanism to a new use. On examining the 

 cavity in which the eye of the shark revolves, we find 

 that the globe, which is the immediate seat of the power 

 of vision, is lighted from the bottom, on which in other 

 animals besides those of this great family it rolls, and is 

 placed on a small platform or plane formed by the top of 

 a small pillar, whose base is fixed on the osseous circle of 

 the common ocular cavity; or, in more scientific language, 

 the pillar we speak of, which inclines slightly forward in 

 order that it may be accommodated to the direction in 

 which objects are usually viewed, is an extension or 

 modification, of the orbitary process of the "sphenoid 

 bone." 



We have alluded to the enormous dimensions of the 

 mouth of the shark. It is armed with from three to six 

 rows of compressed, sharp-edged, triangular, and serrated 



