COLOUR PERCEPTION IN FISH 17 



brilliantly coloured than the females, either 

 at the spawning season or always. This 

 is probably a process in evolution which 

 tends to make them more attractive to the 

 female. We also know that fish sometimes 

 assume a colour similar to their surround- 

 ings. This colour is, no doubt, evolved for 

 their protection from enemies, and surely 

 a very large proportion of these enemies 

 are other and larger fish. Many of the 

 larvse of water insects and other creatures 

 upon which fish feed are also coloured 

 according to their surroundings, in order 

 to facilitate their concealment. These 

 facts would naturally lead us to come 

 to a conclusion opposed to that of Sir 

 Herbert Maxwell, as the probabilities all 

 point towards the power of fish to discern 

 various colours. 



Another very important point is the 

 structure of the fish's eye in comparison 

 with that of man, who we know has the 

 power of discriminating between colours. 

 This power is, in the human eye, probably 

 situated in the layer of rods and cones 

 of the retina. Had the fish's retina not 

 contained this layer, as is stated by Sir 



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