WHAT THE FISHES SEE 



animal kingdom. There, as elsewhere and perhaps 

 better than elsewhere, we realize the importance of 

 the work of life in its dual action, morphogenetic or 

 organic construction, biogenetic or utilization according 

 to possibilities. To sum it up in its main characteristics 

 would lead us through a long and suggestive series of 

 episodes. We find the most elementary stage of it 

 in that latent condition, not yet established, in which 

 the skin is sensitive to radiations of light; the future 

 faculty of sight is nothing more than an indistinct, 

 confused sensibility, without any definite organs de- 

 voted to its purposes. It displays itself more definitely 

 at the higher stage when the pigmentary patches 

 capable of absorbing light and increasing its influence 

 establish themselves in various parts of the body. 

 We then have a condition of sensitivity to light, but 

 not yet vision itself. 



This appears when the crystalline lenses and retinas 

 form; the former projecting images which are collected 

 and made sensible by the latter. We find the first 

 experiments of this sort exemplified by most groups 

 of aquatic animals in their different ways. Sometimes 

 the lenses are too large and badly situated, and can 

 only concentrate the rays without producing definite 

 images; sometimes the retinas are too small or in- 

 sufficiently innervated and can only give sensations of 

 luminosity, of variations in the lighting, of coloration, 

 and can do no more and no better. Many of these 

 eyes, with a structure imperfect as regards optical 

 equipment, sometimes in a bad position in the organism, 

 give only a slight result and play only an unimportant 

 part, despite the appearance of complexity they 

 present. As regards structure, they seem equal to 

 eyes with a true power of vision, but they are far from 

 equalling them as regards function. 



We must go back to the Cephalopod molluscs 

 like the squid, cuttle-fish and octopus, or the higher 

 crustaceans, crabs and lobsters, which are unique 

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