54 Ants. 



arranged in a triangle on the forehead. We do not 

 yet know how these eyes sec, or whether the eyes 

 and ocelli act in the same way. 



But it seems clear that the image produced by 

 the ocelli must be altogether different from the 

 picture given by the compound eyes ; and we may 

 therefore reasonably conclude that the two organs 

 have distinct functions. 



8. The ocelli, or simple eyes, probably see in the 

 same manner as ours do. That is to say, the lens 

 throws an image on the back of the eye, which we 

 call the retina. In that case they would see every- 

 thing reversed, as we ourselves really do; though 

 long practice has given us the right impression. 

 The simple eye of insects thus resembles ours in 

 this respect 



As regards the mode of vision of the compound 

 eyes, there are two distinct theories. According to 

 one, each facet takes in only a small portion of the 

 field ; while, according to the other, each facet acts 

 as a separate eye. 



9. This latter view has been maintained by many 

 high authorities, but it is difficult to understand 

 how so many images could be combined into one 

 picture. Some insects have more than 20,000 facets 

 on each side of their head. No ants, indeed, have 

 so many, but in some there are not less than 1,000. 



In fact, these, so far fortunate, insects realise the 

 epigram of Plato 



