WHAT THE FISHES SEE 



or the colour of bright objects, even by a very slight 

 degree of luminosity. As regards the perception of 

 movements, that causes no difficulty, because of the 

 displacements of the image, confused though it may 

 be, projected upon the retina, and the succession of 

 perceptions which results. The vision may be weak 

 in comparison with ours, but it has a certain definite 

 capacity. 



We may now try to represent to ourselves the visual 

 world of fishes, at least that of the fishes which have 

 one, since they usually live in zones traversed by 

 luminous rays which the retina can perceive. Doubt- 

 less it is not very different from the world we see when 

 we are plunged into darkness or enveloped in a dark 

 uniform fog. Objects appear like stains, varying in 

 appearance according to their brightness or hue, 

 varying in size according to their mass, and of un- 

 decided shape. We can see their movements when 

 they go from one place to another, or when we move 

 ourselves; sometimes they fade out and disappear, 

 sometimes they become progressively stronger. We 

 see them better when they are straight in front of us; 

 we turn to them to distinguish them the better, to 

 draw near them or to avoid them. Suddenly, when 

 we are quite close, we see them more clearly; we 

 discern colours, contours, shapes, which vanish again 

 as soon as we draw away from them. In short, in fact 

 and in appearance, this visual world has neither 

 distances nor contrasts. The light weakens in it, 

 becomes uniform, confusing instead of distinguishing. 

 From moment to moment, in one place and in another, 

 there rise up bright spots which take form as they 

 approach and fade into nothingness as they go away. 

 Nothing stands sharply out as in the air. Every- 

 thing comes within a field of gradation from grey to 

 black. 



The story of the visual organs and of vision itself 

 is very interesting, if we follow it out throughout the 

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