Chapt. vi. Range of vision limited. 81 



I think a fish's range of vision laterally in the water 

 is very limited, and that however quickly he may see any 

 thing reflected against the light or in the air, he does not 

 see nearly so far laterally under water. Though clear- 

 sighted, he is I think short-sighted under water. It is the 

 consequence, in my opinion, of the density of the element. 

 Try yourself, in a large swimming bath, and you will find 

 you cannot see very far about you at the bottom. It is 

 true that the short-sightedness of a man under water, is 

 not worth much as an argument, to prove short-sighted- 

 ness in the same position of an animal formed for exist- 

 ence in that element. Still I just throw it in, in conjunc- 

 tion with other facts tending to the conclusion, that, the 

 density of the element has the same effect on the visual 

 organs of the fish also. On no other theory could I under- 

 stand how it is, that large fish and small fish manage to 

 exist in such close proximity. You see any number of 

 small fish in one part of a pool, and in another part of 

 the selfsame pool any number of the very fish that prey 

 upon them; and those fish are on the feed too though not 

 noticing the little ones, for directly you spin one of those 

 same little ones near them as a bait, it is taken, whereas 

 if the big fish had seen the little ones, I cannot conceive 

 why they should let them alone, and immediately take 

 your bait. These little fish, it should be remembered, 

 have no thick coverts in which to hide like deer from the 

 tigers that prey upon them, nor have they greater fleetness 

 by which to escape In the open. The substitute for their 

 protection seems to be the density of the element in which 



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