594 SCIENCE PROGRESS 



doubt that the hydrographic changes in the condition of the 

 northern seas produce very important changes in the climate 

 of the countries the coasts of which they affect. This is a 

 very obvious thing when we consider that an enormous 

 amount of heat is annually brought to northern countries 

 by the vast body of warm water which washes their shores 

 after drifting up from the sub-tropical Atlantic. Not only so, 

 but it has clearly been proved that the barometric pressure 

 of the atmosphere is also closely affected by the changing 

 temperature of the sea, and obviously the boundaries of the 

 icefields without the coasts of the ice-locked countries are to 

 a very important extent also dependent on the temperature 

 of the sea. But how can the abundance of fishes in the sea 

 be affected by the temperature and salinity of the water? 

 This a problem which until a few years ago had hardly come 

 within the range of the methods of the naturalist. The 

 Scandinavian zoologists did indeed attempt to investigate it 

 with reference to the migrations of the herring off the coasts 

 of Sweden, and prima facie evidence was furnished for the 

 belief that this fish followed in its movements those of a 

 body of sea water of well-defined physical constitution. When 

 the international fishery investigations were initiated five years 

 ago on a really adequate scale, it became possible to seek for 

 the evidence that not only the herring but also a host of other 

 fishes were affected by variations in the temperature and 

 salinity of the water in which they lived. 



The establishment of such a connection meant of course 

 the investigation of the life histories of the fishes which form 

 the material of the commercial fisheries. This enormous task 

 had already been partially accomplished when the international 

 investigations were commenced in 1902. Since 1880 many 

 workers in Britain and on the Continent made out much of 

 the habits and life histories of marine fishes. In Scotland, 

 Macintosh and the St. Andrews school of zoologists, in 

 England the naturalists of the Marine Biological Association, 

 in Germany the zoologists of the Kiel Kommission, and in 

 Denmark the marine biologists of the fishery authority, all 

 had done much to trace the migrations, spawning habits, 

 development, and distribution of the commoner kinds of edible 

 marine animals. The result was that at the beginning of the 

 present century our knowledge of the life histories of fishes 



