THE SEA-FISHERIES 297 



in the flesh of the herring that gives this fish its special value 

 as a winter food, and no effort should be spared to increase 

 the home consumption of herrings. They are probably the 

 cheapest form of animal food, and have a very high nutri- 

 tional value. Many people will be surprised to learn that 

 out of 12,000,000 cwts. of herring landed, nearly 10,000,000 

 cwts. were exported annually (90 per cent, in 1913) before 

 the war. The total catch is far from being too much for 

 the needs of our own country. Taking three herrings to 

 the pound, the total catch in the United Kingdom before 

 the war would only allow two herrings a week to each adult 

 individual of the population. 



The flat-fish of our markets (with the exception of skates 

 and rays, which are a totally different kind of fish, and are 

 nearly related to dogfishes and sharks) belong to the family 

 Pleuronectidae, the members of which undergo a remarkable 

 transformation in their early life-history, whereby the 

 bi-laterally symmetrical larva, with the right and left sides 

 of the body similar, and an eye on each, undergoes in its 

 growth a torsion of the head and some other parts, a flatten- 

 ing of the body from side to side, and a great extension 

 dorso-ventrally so as to be converted into the famihar 

 " fluke " form, with the upper (usually the right) side of the 

 flat body pigmented and bearing both eyes, and the lower 

 blind and more or less non-pigmented or white. Our best- 

 known marketable Pleuronectids are : — 



Halibut — a northern fish, of large size. 



Sole — commoner in the south down to Morocco ; a shallow- 

 water fish common in the Irish Sea. 



Turhot — in deeper water ; a North Sea fish, but not very 

 abundant. 



Brill — more abundant than the turbot, especially in the 

 south. 



Plaice — a northern form, very abundant on the coasts of 

 Iceland and farther north; distributed all around 

 our coast, and important as a food of the people. 



