WHAT THE FISHES SEE 



with all the fancy details of luxury, whereas the other 

 has only a few clumsy pieces of rough furniture. Or, 

 since we are considering optical systems whose purpose 

 it is to form and project images of external objects, 

 one might be compared to a first-rate camera, fitted 

 with a perfect lens, with exact focusing and very rapid 

 plates, while the other is like an old-fashioned piece of 



*■ 



MM 



Fig. 49. — Greatly enlarged details of the structure of the retina in the 

 Basilisk Blenny. Left, construction of the fovea, composed of 

 cone cells only (in black). Right, the structure of the rest of the 

 retina, showing bundles of rod cells, alternating with individual 

 cone cells. Linear magnification, 600 times. 



apparatus, with a badly cut lens, focusing of doubtful 

 accuracy, and inferior plates. The former gives pre- 

 cise, clear, and faithful reproduction, while the second 

 produces a picture which is blurred. The image is 

 there, but it is confused, flat, faint, often unrecogniz- 

 able. The fish's vision is blurred too. The refringency 

 of the water in which the fish lives exaggerates this 

 fundamental defect, so that it sees as though in a fog, 

 and even the most fortunate can see only objects which 

 are close by. 



Must we therefore apply to the fishes the Biblical 

 262 



