THE MOSAIC THEORY. 185 
The prevailing opinion of entomologists now is that 
each facet receives the impression of one pencil of rays ; 
so 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; 
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, 
ii is clear that they do see. 
From the observations of Sprengel there could of 
