SEEN WITH THE EYE OF A FISH 33 



of an animal, when seen as in nature, make the body 

 appear of a uniform shade, how the markings on this 

 uniformly shaded body appear to be part of the scenery 

 around, and how, in consequence, the animal fails to 

 arrest attention. 



Thayer generalised on fishes, and gave no illustra- 

 tions, but I think the photographs shown in the present 

 chapter fully confirm the correctness of Thayer's theories, 

 at any rate as regards fishes. But neither Thayer nor 

 any other writer attributes sufficient importance to 

 reflection as a factor in concealment, and for this reason 

 I have dealt with reflection at considerable length. 



It might be thought that though the bars effectively 

 conceal the perch when seen among reeds, they would 

 make him conspicuous in open water. From my observa- 

 tions of perch swimming in the pond, it is remarkable 

 how little such is the case. The body of a perch is 

 so perfect a reflector that, except where the bars are 

 present, it takes the exact shade of the water around. 

 It is almost impossible to detect the fish's outline, and 

 when looking at it from under the surface, through any 

 extent of water, you see merely a few dark shadows 

 moving along, such as might be caused by reeds or weeds. 



Next let us consider the lemon sole as a type of the 

 flattened fishes which pass most of their time lying on 

 the bottom. The under-surface being out of view needs 

 no protection, and so is colourless. On the back the pig- 

 ment cells are arranged so as to simulate exactly the 

 stone and sand markings. After the lemon sole had been 



D 



