620 SCIENCE PROGRESS 



cod-fisheries, but also to the fishery for haddock in the northern 

 part of the North Sea. The latter relation seems to be an 

 anomalous one, for it might be argued on a priori grounds that 

 a high sea-temperature would lead to increased metabolism 

 and more perfect nutrition. 



It seems to be established that a high sea-temperature off 

 the coast of Norway is to be associated with imperfect nutrition 

 of the cod-shoals visiting that part of the ocean ; and the cause 

 is perhaps to be sought in some food-supply factor. Several 

 such factors might be suggested, and that indicated by Helland- 

 Hansen and Nansen is as probable as any. The temperature of 

 the sea off the coast of Norway, and in the northern part of 

 the North Sea is a function, not only of the intensity of flow 

 of the Gulf Stream, but also of that of the southerly-flowing 

 East-Icelandic Polar Stream, which consists of cold water. 

 The ultimate food-stuff in the sea consists of the inorganic 

 compounds of nitrogen and carbon on which diatoms and other 

 protophyta feed. These constituents of the plankton are in 

 their turn the food of small animals, such as copepods and 

 other micro-crustacea, upon which the fishes feed, either directly 

 or indirectly. The abundance of these inorganic food-stuffs 

 is therefore the factor governing the production of organised 

 living substance in the sea ; and the grade of nutrition of the 

 cod, and other fishes, depends ultimately upon the abundance 

 of these compounds. 



Water rich in these substances flows into the Polar Sea 

 from the Siberian and other rivers. But a large part of the 

 surface of this sea is covered with ice, and, since sunlight is 

 unable to penetrate this covering in sufficient intensity to be 

 utilised by the vegetable plankton, it may well be the case that 

 the greater mass of this store of food-stuff is not utilised. 

 Probably the water beneath the ice in the Polar Sea is relatively 

 rich in the inorganic food-stuffs of the vegetable plankton ; and 

 it is this water that flows south as the East-Icelandic Polar 

 Stream, and mixes with the Gulf Stream water in the sea 

 between Iceland and the coast of Scotland. If the strength 

 of this stream is unusually great in one year, the temperature 

 of the Gulf Stream drift off the coasts of Norway, or in the 

 higher part of the North Sea, will be unusually low. The Gulf 

 Stream water itself appears to contain comparatively little 

 inorganic food-stuff, or plankton, and it is where the water 



