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merit lately mentioned as found in the outtle, a 

 substance of a resplendent green or silvery co- 

 lour, serving not to absorb, but to reflect the 

 rays of light ; and thus enabling them to see by 

 a much more obscure light than would otherwise 

 have been necessary. 



Among vertebral animals, fishes have an eye 

 somewhat similar to that of the cuttle ; consist- 

 ing essentially of a spheroidal sclerotic coat, con- 

 taining the chief humour of the eye, a lens which, 

 as in the cuttle, is almost globular, and a retina, 

 which is often plaited, as it were, into numerous 

 folds, arranged like the meridian lines on a globe. 

 They have, however, in addition, a proper cornea 

 like insects, presenting, not indeed numerous fa- 

 cets, but one uniformly convex surface, although 

 the convexity is very slight ; and they have further, 

 what insects have not, a perfectly formed iris, or 

 circular curtain, placed before the lens, in which, 

 and not as in the cuttle in the sclerotic coat, the 

 pupil is situated. The rays of light accordingly 

 traverse, in these animals, first the transparent 

 cornea, and afterwards in order the anterior por- 

 tion of the humours of the eye, the pupil, the 

 lens, and the posterior portion of these humours ; 

 by all which, except the pupil, they are more or 

 less refracted, till they are at length brought to a 

 focus on the retina. The chief peculiarity in the 

 eyes of fishes, as contrasted with those of the su- 

 perior tribes of animals, is the comparative flat- 

 ness of their cornea, and convexity of their lens ; 

 it appearing to have been the object of nature to 



