88 



The Life Story of the Fish 



Diagram M 



its jurisdiction. By this system the images are allocated to 

 the two halves of our brain in the same way in which they 

 would be if our eyes were placed so that each saw only one 

 side, and if decussation were complete. The incomplete 

 decussation is a compensation for the fact that the two eyes 

 now see the same thing. 



Having concocted this theory, we are at liberty to shoot 

 holes in it. The first hole comes of the fact that, although 

 the fish's two eyes face in different directions, those direc- 

 tions, in many fish, are not diametrically opposite, and there 

 is a small section of the world which both of them see at the 

 same time. This statement is based on theoretical deduction, 

 for obviously no one knows just what a fish's eyes see. But 

 the placing of most fishes' eyes and the extent to which they 

 protrude permit us to argue as follows. 



As we look down on the fish (Diagram N), the field of 

 vision of the right eye, E', is bounded by its side and by its 

 nose. The limiting lines of sight are E'B and E'C, and the 

 whole field between those two lines, comprising a little more 

 than a half circle, is visible to the right eye. Similarly, the 



