COMPENSATION. 187 



and by a mechanism which Ave should not suspect. The 

 eye is a multiplying-glass, with a lens looking in every 

 direction and catching every object. By which means, 

 although the orb of the eye be stationary, the field of vision 

 is as ample as that of other animals, and is commanded on 

 every side. When this lattice- work was first observed, the 

 multiplicity and minuteness of the surfaces must have add- 

 ed to the surprise of the discovery. Adams tells us that 

 fourteen hundred of these reticulations have been counted 

 in the two eyes of a drone-bee. 



In other cases, the compensation is efiected by the num- 

 ber and position of the eyes themselves. The spider has 

 eight eyes, mounted upon difierent parts of the head ; two 

 in front, two in the top of the head, two on each side. These 

 eyes are without motion, but by their situation suited to 

 comprehend every view which the wants or safety of the 

 animal rendered it necessary for it to take. 



VII. The iviemoirs for the Natural History of Animals, 

 published by the French Academy, a. d. 1687, furnish us 

 with some curious particulars in the eye of a chameleon. 

 Instead of two eyelids, it is covered by an eyelid with a hole 

 in it. This singular structure appears to be compensatory. 

 and to answer to some other singularities in the shape of the 

 animal. The neck of the chameleon is inflexible. To make 

 up for this, the eye is so prominent as that more than half 

 of the ball stands out of the head, by means of which extra- 

 ordinary projection the pupil of the eye can be carried by the 

 muscles in every direction, and is capable of being pointed 

 towards every object. But th<n so unusual an exposure of 

 the globe of the eye requires for its lubricity and defence a 

 more than ordinary protection of eyelid, as well as a more 

 than ordinary supply of moisture ; yet the motion of an eye- 

 lid, formed according to the common construction, would be 

 impeded, as it should seem, by the convexity of the organ. 

 The aperture in the Ud meets tliis difficulty. It enables the 

 animal to keep the principal part of the surface of the ey« 



