WHAT THE FISHES SEE 



itself, with its receivers scattered at some distance from 

 one another, cannot fix these images and makes them 

 sensible in a lessened degree. The eye is weak. 

 Compared with our own, it seems to suffer from long- 

 sightedness aggravated by an extreme weakness of the 

 retina. In the best instances, it has a certain capacity 

 only within a restricted visual field, especially in eyes 

 capable of binocular vision, in which the sensorial 

 elements are grouped together in greater number, and 

 sufficiently closely. 



This brings me back to the eye of the basilisk 

 blenny, its retina, and my study of its conformation. 

 I find that the retina, in this species, has a fovea rich 

 in cone cells; consequently, its visual function can 

 achieve the degree of keenness described. In the other 

 parts I find rods and cones, the former being grouped 

 in bundles alternating with the latter, which are more 

 isolated. This complexity of structure denotes, as 

 we are led to expect by the creature's behaviour, a 

 considerable functional capacity. But there are many 

 factors working against such a superiority, preventing 

 the creature from obtaining all its advantages; the 

 lens is globular, too near the retina to project a clear 

 image upon it; the nerve-cells are too few to refine 

 the sensorial perception adequately. But this eye, 

 with a retina well equipped, is an exception. In most 

 other fish, the retina has no fovea, the rod-cells are 

 more numerous than the cones, and they are spaced out 

 instead of being grouped. All this is a disadvantage, 

 which, with the defects of the crystalline lens, causes 

 the vision to be of an inferior quality. 



There is no essential identity between the eye of 

 the fish and that of the fisherman who tries to catch it. 

 They do not both see the same thing. The two 

 organs may seem, taken as a whole, to bear a striking 

 resemblance but, in reality, they differ in many par- 

 ticulars. They are like two houses which are identical 

 as regards general outline, but of which one is fitted 

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