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while others, as the bee, have both. They are 

 for the most part extremely large ; varying, how- 

 ever, between about one-sixtieth and one-fourth 

 part of the weight of the whole body. Their 

 structure is eminently beautiful ; consisting, as 

 they do, not of coats and humours, but princi- 

 pally of a series of pyramids of nervous substance 

 connected together, the apices being on the bul- 

 bous extremity of the optic nerve, and the bases, 

 invested each by a thick transparent membrane 

 of a hexagonal shape, at the circumference of the 

 eye. This membrane, presenting thus nume- 

 rous facets, which look in every direction, is 

 called the cornea, and seems to be in insects 

 the only instrument of refraction, the images of 

 objects being most probably impressed, by this 

 means, directly on the base of each pyramid, 

 which is thus a kind of distinct eye. They have 

 no lens and no pupil, or rather the whole sur- 

 face of the cornea is one large pupil, there being 

 no opake coats to render a proper pupil neces- 

 sary ; and they are destitute both of eye-lids, and 

 of muscles to move the eye, the numerous direc- 

 tions of the facets of the cornea rendering the 

 latter superfluous. How strikingly different is 

 this description of eye which characterises in- 

 sects which fly, and require therefore an ample 

 field of vision, from the simple eye found in the 

 grovelling kinds, which either do not see, strictly 

 speaking, at all, or certainly only quite contiguous 

 objects ! Further, in insects which fly by night, 

 like the moth, there is, in place of the black pig- 



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