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 
