140 ANIMAL LIFE UNDER WATER 



form of the fly can be appreciated; there is a 

 suggestion of colour about the wings, and a slight 

 iridescence round the hackle. Along the side 

 of the body there is frequently a streak of light, 

 particularly if paraffin has been used. 



The foregoing is a description of what is seen 

 by the human eye. A fish as compared .with 

 man is short-sighted, and its behaviour, as 

 observed from under the water, suggests that it 

 does not appreciate the fly until it is seen as 

 a whole within its "window." Here the fly 

 appears as a blurred object, and the fish goes 

 up to have a look at it. If on nearer inspection 

 the fly gives satisfaction, it is taken. 



This inspection opens up another considera- 

 tion, viz. though the angler may not be visible 

 to the fish! when the fly first comes into its 

 " window," he becomes so with the altered posi- 

 tion of the fish. 



Opposite are two illustrations representing 

 the surface of the water as seen from below. 

 Hold the plate in a horizontal position above the 

 level of the head, as before. In the lower photo- 

 graph the blurred image of the fly has just come 

 into the " window." Beyond, the stones on the 

 bottom of the stream are reflected from the sur- 



