38 Tr outing- Flies. 



tive structure of the eye in the fish, and by others 

 to be inconsistent with its limited knowledge of 

 entomology. But this is mere theorising. The 

 eye of a fish is certainly peculiar in its structure, 

 and, as the editor of ' Cuvier's Fishes ' says, is 

 " only an indifferent representative of the beautiful 

 and animated eye of man." The crystalline lens is 

 extremely dense and almost spherical ; the iris can 

 neither be dilated nor contracted, and therefore the 

 pupil cannot be regulated to the degree of light. 

 While all this is true, we must remember that we 

 are not likely to ascertain what fishes can see with 

 their eyes, by simply comparing them with our 

 own ; that they must be in this, as in other parts 

 of their structure, perfectly adapted to the medium 

 which surrounds them; and that what may be a 

 defective eye for an animal on earth, may be the 

 best possible for a fish in water. My belief in 

 the economy of Nature's power leads me to sup- 

 pose that they have no more than they need ; my 

 faith in her goodness assures me that they have 

 no less. 



Mr Erasmus Wilson, in "Ephemera's" 'Handbook/ 

 sums up a minute consideration of this subject in 

 the following words : " Whether, therefore, we re- 

 gard the mechanical or the vital apparatus of the 

 organ of vision, or whether we pursue the inquiry, 

 by anatomical investigation, or by observation of 



