290 NATURE'S TEACHINGS. 



constructed on much the same principle, except that the number 

 of facets is infinitely more. Taking, for example, the eyes of 

 the Tortoise-shell Butterfly, we find that there are about seventy 

 thousand lenses or facets. Now, it is possible, with care, to 

 remove the eye from the insect, cleanse it, and arrange it in 

 a microscope in such a way that objects can be seen through 

 it. When this is done, a separate image is seen in each facet, 

 just as is the case with the Multipy ing- glass, only, as the 

 facets are very much more numerous, the effect is proportion- 

 ately more striking. 



The reader may notice that the facets of the insect eye 

 appear to be hexagons as perfect as those of the honey - 



INSEOT EYE. TUMBLER. MULTIPLYING-QLASS. 



comb. This appearance is probably due to the fact that each 

 eye is covered with a convex plate of glassy brightness and 

 transparency, and that, when such objects are viewed from the 

 front, they appear to have hexagonal instead of rounded out- 

 lines. A familiar example of this fact may be found in the 

 glass tumblers which are ornamented with rounded projections 

 on their surface. If a photograph of one of these tumblers 

 be taken, the resemblance to the hexagonal markings of the 

 insect eye is so close that the tumbler might easily be taken for 

 the eye. 



