GREA T BRIT A IN. 123 



may be taken at the inland extremity of the lake, the 

 pollack being actually in the snow-water stream. There is 

 no sign whatever of fresh-water fish. In short, the sea- 

 fish have complete possession of this lake, which is entirely 

 fresh. 



Marine fishes in the Baltic have become acclimatised to 

 a residence, where the character of the water has gradually 

 changed from saline to fresh, so that the herring and some 

 other sea forms, unable to obtain access to the Arctic 

 Ocean, deposit their eggs in potable water, and the four- 

 horned Coitus quadricornis even migrates to the rivers. 

 Both the foregoing instances show how marine Gadidae may 

 voluntarily enter and reside in fresh waters, while we have 

 no reason to suppose that, were their return to the sea 

 cut off, they could not live and continue their species in 

 this new locality. 



These fish, especially the cod, occasionally shift their 

 ground, some cause, probably absence or presence of some 

 peculiar food, inducing them to leave localities they had 

 previously frequented ; thus the London market used to be 

 supplied from the Orkneys and the Dogger Bank, but 

 during the present century these fish have extended their 

 range to off Lincolnshire and Norfolk in sufficient numbers 

 to render their capture remunerative. 



Fisheries for cod have existed in the north many 

 centuries, for we know that one in the German Ocean was 

 recognised before A.D. 1 368, because in that year the city 

 of Amsterdam obtained permission from the King of 

 Sweden to form an establishment in the island of Schonen 

 for the purpose of carrying it on. But prior to John 

 Cabot's re-discovery of Newfoundland in A.D. 1496 the 

 fisheries of the greatest importance in Europe were off our 

 western isles and the coast of Ireland. English fishermen 



