CHAPTER XIII 



THE FLOUNDER 



Peculiarities of Flat-fishes — Percoid characters of Psettodes — 

 distribution of Pleuronectids — the Flounder described — colora- 

 tion — difterences from the Plaice — reversed examples — ambi- 

 colorate specimens — albinos — distribution — habits — breeding — 

 growth and transformation — value as food 



WE have already mentioned that the Perches 

 represent the highest stage in the evolution 

 of the normal fish, but that from them various 

 groups have evolved m adaptation to special modes 

 of life. Such a group is that of the Flat-fishes 

 {Pleiironectidce), which form a well-marked order 

 which has received the name Heterosoniata. 



These fishes have a strongly compressed body 

 and differ from all other fishes in that they lie on 

 one side at the bottom of the sea ; consequently 

 only the exposed side is coloured in such a way 

 as to render the fish inconspicuous, whilst the 

 hidden under-side is white. Still more remarkable 

 is the shifting of the eye of the under-side from 

 its original position, where it is of no use, round into 

 the light, so that both eyes appear to be on the 

 same side of the head ; thus, in Flat-fishes we can 

 distinguish between an eyed or coloured side and 



a blind or white side. 



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