ICHTHYOLOGY. 11 



ing that the vision of fish is very perfect, others the 

 contrary. The eye, as Paley has pointed out in his 

 Natural Theology, is in its structure well adapted to the 

 element in which the fish lives ; but it suggests that fish 

 as a class are near-sighted, and that their vision is con- 

 siderably impeded by its being covered by the common 

 skin of the head, in order to defend the eyeball, fish, as is 

 well known, having no eyelids. Stoddart, in his Scottish 

 Angler, goes so far as to say that a trout " is a remarkably 

 near-sighted fish, and cannot behold any object distinctly 

 however large, unless within the range of eight or ten 

 yards." From this remark, which, by the way, if true of 

 the trout, is true of most other fish, anglers might come 

 to the conclusion that it matters little whether they show 

 themselves or not, and that a great deal too much fuss is 

 made about the colour and size of flies ; while, per contra, 

 it might be argued that on account of this very defective- 

 ness of vision it is all the more necessary to imitate 

 nature as closely as possible with artificial flies, and that 

 a shadow cast upon the waters, or a form presented which 

 cannot be understood, has all the greater terror. Stewart, 

 however, in his Practical Angler, says that " of all senses 

 the trout possesses, that of sight is the most perfect, and 

 is the one which most affects the angler in pursuit of his 

 vocation." Eonald, in his Flyfisher' s Entomology, takes 

 much the same view, and if his theory of " optical refrac- 

 tion," whereby, as he shows in a diagram, the fisherman 

 is " projected " high up in the air above the fish, is 

 correct, the wonder is how we ever get near a trout at all. 

 We see here, then, how, on this one single question, 

 " doctors differ," and how wide a field is still open for 

 experiment and observation. I will only add that the 



