148 SPECIES NOT 



verted into the eye of the bird or the quadruped? 



Look again at the hexagonal corneules into 

 which the transparent covering of the compound 

 eyes is divided; in the ant we see fifty, in the 

 house-fly four thousand, in the butterfly seventeen 

 thousand, in the mordella beetle twenty-five thou- 

 sand! (Owen.) In each of these divisions there 

 is a separate lens, and to each there is sent a 

 twig of the optic nerve, "at once separating and 

 connecting together the component ocelli of the 

 compound eye." 



Now how is this beautiful organ produced by 

 ''natural selection?" It is only given to the per- 

 fect insect which lives a few hours, days, or 

 weeks. The caterpillar from which the insect was 

 developed, has but a single, simple eye, because 

 its life is for the most part stationary on a leaf 

 or branch, and it requires no more sight than 

 this single eye gives it. But the perfect insect 

 has to fly with rapidity, and it is necessary that 

 . it should see distant objects, and it is therefore 

 provided with a compound eye! Apterous, or 

 wingless insects, are positively blind, u as the 

 Claviger; and the blindness is often peculiar to 

 the female sex, as in the glow-worm and cochineal 

 insect!" (Owen.) 



Let us now look for a moment at the eye as 

 specially adapted to fishes. First there is no 

 lachrymal gland, because there is fluid to lubricate 

 the cornea. Mr. Darwin will say this has become 

 extinct from disuse. The cornea is flat, and is 

 thus less liable to injury in the rapid movements 



