EYES OF THE TRILOBITE. 61 



scope has disclosed to us the structure of an insect's 

 eye, which is one of the most striking miracles 

 of Divine skill which the bodies of living beings 

 exhibit. The human eye, and that of other 

 mammalia, consists of a single optical instrument 

 analogous in its structure to a telescope, or re- 

 sembling rather a photographic apparatus with its 

 lens, its dark chamber, and the paper on which to 

 receive the reduced image of the object to be 

 observed, answering to similar parts of the eye 

 itself. The eye of an insect, however, consists, not 

 of a single optical instrument thus constructed, 

 but of a series of such instruments, each furnished 

 with its separate lens, pupil, cornea and optic 

 nerve, but all combined together in the one eye. 

 In the common house-fly there are 8,000 such 

 distinct optical instruments in each eye, and 

 nearly 13,000 in the eye of a dragon-fly. Each of 

 these distinct tubes, with its accompanying appa- 

 ratus of vision, is indicated by one of the facets into 

 which the outward surface of the one compound 

 eye is cut, and the structure is rendered necessary 

 because the eye is motionless and cannot be directed 

 towards its object with the facility in which this 

 can be done by the mammalia. Than this no 

 portion of the structure of an insect exhibits a more 

 remarkable instance at once of creative skill and 

 foresight skill in the formation of the complicated 

 apparatus itself and its accurate adaptation to the 

 laws of light, and foresight in anticipating and 

 supplying the wants of the creature to whose 

 structure it occurs. 



