2 THE HABITS AND HAUNTS OF FISH. 



and respiratory animals generally to the atmosphere. 

 But, on the other hand, experience tends to prove 

 that the more suited the eye of the fish may be 

 to his particular element, the more indistinct is his 

 vision beyond it. We have an instance of this in 

 the grayling, which, although more cautious and timid, 

 and possessed of keener visual organs than the trout, 

 will rise much nearer the angler, and is not so easily 

 disturbed and affrighted. The inferiority of a fish's 

 perception of objects in the air, as compared with 

 what is in or upon the surface of the water, partly 

 arises from the fact that the eye adapts itself to the 

 medium through which the rays of light are trans- 

 mitted. We have frequently observed the pupil of 

 a fish's eye contract considerably in the course of 

 a second or two after it has been taken from the 

 water, from the same principle which causes the pupil 

 of the eye of the domestic cat to expand or contract 

 as the light diminishes or increases. Observation 

 shows that it is the moving object that frightens the 

 fish. We have seen trout suddenly cease feeding and 

 return to their accustomed retreat upon our merely 

 raising an arm ; and when their " holt " has proved to 

 be near the opposite bank, and we have been in full 

 view, in clear relief upon a high bank, on keeping 

 perfectly stationary for fifty to seventy minutes, they 

 have again ventured into the open to take our fly. 

 From a constant repetition of convincing experiments 

 we have been led to infer that the crystalline and 

 various other humours of a fish's eye are capable of 

 reflecting but a vague and distorted image of any 



