THE INSTINCT AND SENSES 01 FISH. 239 



He may have seen the missile iu air^ it is true ; but 

 we think he did not, as the object was cast from 

 directly behind him and he did not shift until the 

 circle of disturbance reached him. 



The power of sight in fish, if not more interesting, 

 is of the greatest importance to the angler, who, in 

 spite of all difficulties, must endeavour to appreciate it, 

 although he starts with the knowledge that the result 

 of his studies will be but mere guesswork, for the 

 simple season that the eye of man diflfers much from 

 that offish. 



With the purpose of viewing a submerged object, a 

 man may place himself in the same position as fish; 

 but then he merely sees as he sees, not as do the fish ; 

 and the same result attends attempts to gain information 

 with the aid of glass-sided or glass-bottomed tanks, 

 yet some knowledge may be gained by such methods as 

 to the comparative invisibility of different materials and 

 colours. 



By the action of the eye a picture is reproduced on 

 the retina, but beyond this there is little similarity 

 between the eye of man and fish ; for whereas the form 

 of the fishes is round, that of man^s, although convex 

 on back and front surfaces, is much more so on the 

 former than on the latter. 



This construction of the human eye afibrds the 

 means of almost instantaneous contraction and ex- 

 pansion of the lens, thus providing the ability to focus 



