88 FLY FISHING AND SPINNING 



variations as regards colour in the individual members of 

 each hatch of water insects, but also that trout do not 

 always appear to exercise the power of discriminating which 

 they undoubtedly possess, but will rise freely to the poorest 

 imitations of the flies which are on the water. 



I do not consider that trout can appreciate sound as we 

 know it ; rather are they gifted with a fine sense of all 

 vibratory motion. Sound is communicated by the vibration 

 of the air or other elements, but other vibrations of these 

 elements can be produced without sound, and the trout 

 may, therefore, depend on the tactile nerves rather than on 

 the auditory ones. If trout were dependent on the faculty 

 of hearing for their safety, and relied to any extent on this 

 faculty to give them warning of a danger which might not 

 be within their range of vision, I do not think that wading 

 would be so productive of good results as it undoubtedly is. 

 The noise of one's brogues on the pebbles can be distin- 

 guished when the ear is submerged for considerably over 

 half a mile in perfectly quiet and unbroken water in rivers, 

 and for miles in lakes. 



THE VISION OF A TROUT 



Although it is supposed that trout cannot see an object 

 which is behind them that is, in the direction of their 

 tails, I am of the opinion that under certain conditions 

 they can indirectly perceive the approach of any object 

 above the surface of the water, even when such objects are 

 directly behind them, i.e., in what I call the normal zone 

 of invisibility. (See Diagram 1, C.E.D.). 



I have noticed that however carefully I have approached 

 from the 4ower end of a shallow, pebbly pool, unless my 

 approach is masked by a heavy background of trees, the 

 trout in the shallow and lower end take fright and run up 

 into the upper or deeper portion. For many years the 



