THE MOSAIC THEORY. 185 



The prevailing opinion of entomologists now is that 

 each facet receives the impression of one pencil of rays ; 

 BO that, in fact, the image formed in a compound eye 

 is a sort of mosaic. 



On the other hand, this theory itself presents 

 great difficulties. Those ants which have very few 

 facets must have an extremely imperfect vision. 

 Again, while the image produced on the retina of the 

 ocellus must of course be reversed as in our own eyes 5 

 in the compound eyes, on the contrary, the vision would, 

 on this theory, be direct. That the same animal should 

 see some things directly, and others reversed ; and yet 

 obtain definite conceptions of the outer world, would 

 certainly be very remarkable. 



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

 epigram of Plato — 



Thou lookest on the stars, my love, 



Ah, would that I could be 

 Yon starry skies, with thousand eyes 



That I might look on thee ! 



But if the male of F, pratensis sees 1,000 queens 

 at once, when only one is really present, this would 

 seem to be a bewildering privilege, and the prevailing 

 opinion among entomologists is, as already mentioned, 

 that each facet only takes in a portion of the object. 



But while it is difficult to understand how ants see, 

 li is clear that they do see 



From the observations of Sprengel there could of 

 14 



