THE SENSES OF FISHES. 9 



water fishes may and do arrive, under the pursuance of 

 the angler, or general fisherman* 



The formation of the eye of the fish does not materi- 

 ally differ, one species from another, among the angler's 

 fishes. The cornea is somewhat flat in sectional outline, 

 and the shape, or, so to speak, the ground plan, is virtu- 

 ally similar in save the European grayling (S. tliymallus). 

 The pupil of the eye of this fish is oval instead of circu- 

 lar the oval of the plover's egg rather than that of the 

 hen, being sharper than a true oval at one end. The 

 apex of this sharp end is pointed toward the upper part 

 of the head, tail ward, giving the fish a somewhat sinister 

 appearance. What purpose this particular configuration 

 serves I do not know, but one thing is certain : The vis- 

 ual ability of the grayling is equal, if not superior, to that 

 of the trout, as is proved by its rising, often from a great 

 depth, to the fly. I notice, also, that the normal waiting 

 position of this fish is inclined toward the water's surface 

 instead of being horizontal, as is usually the case with 

 trout. This being so, the greater mass of the rays of 

 direct sunlight would fall on the forward part of the eye, 

 and I offer it as a conjecture, based on the law of devel- 

 opment, that this, continued through generations, has 

 evolved the peculiar shape. The grayling of this country, 

 though apparently similar in every other respect, does 

 not exhibit the peculiarity referred to. 



It is a general law, observable through the whole 

 range of animal life possessing vision, that the eye is pe- 

 culiarly adapted to the medium through which (and to the 

 manner in which) it receives the light. The more closely 

 we look into this truth, the more apparent and wonderful 



