LENSES OF EYE. 27 



and to aid in the discrimination of food when the pipe 

 is unrolled and thrust down deep into the nectary of a 

 flower. 



The compound eye of a butterfly, wonderful as its 

 structure is, does not greatly differ from that of many 

 other insects, being like them composed of an immense 

 number of little lenses set together to form a hemisphere 

 large in comparison with the insect's head. A portion 

 of one of these eyes forms a pretty and interesting 

 object for the microscope, presenting a honey-comb ap- 

 pearance, the hexagonal lines that mark the division of 

 the lenses being most beautifully geometrical, and regu- 

 lar in their arrangement. More than seventeen hundre_d 

 of these lenses have been counted in a single eye, and 

 each of these is considered to possess the qualities of 

 a complete and independent eye. If this be true, the 

 butterfly may be said to be endowed with at least 

 thirty-four thousand eyes ! 



There exist also, as in other insects, two simple eyes, 

 placed on the top of the head, but so buried in down 

 and scales as to be neither visible, nor useful for vision, 

 as far as we can perceive ; probably the creature finds 

 that his allowance of thirty-four thousand windows to 

 his soul lets in as much light as he requires. 



Every one looking at a butterfly must have remarked 

 its long horns, called antennce, 1 which project from 

 above the eyes, like jointed threads, thickening in some 



1 Antenna in the singular number. 



