10 
president’s address. 
the greater depressions of the bed of the North Sea, while the 
intermediate depths are covered with a mixture of Arctic, 
Atlantic, and Coastal waters, in which apparently the cold 
Arctic influences may predominate in one year and those of 
the warm Atlantic in another. 
The possible bearings of such differences as these on the 
fluctuations observed in the abundance of the more migratory 
fishes are open to the imagination. It is still more important 
to observe that the investigations of the past few years have 
placed the reality of these influences beyond all doubt. The 
first results have naturally been attained in regions where the 
characters of the conflicting currents are sharply contrasted, 
as for example, in the neighbourhood of the Scandinavian 
coast, where the Baltic current of brackish water and the salt 
Atlantic flood come together, and in Icelandic waters where 
the Atlantic stream meets the cold Polar currents. 
To the English naturalist, accustomed as he is to the 
uniformity of the sea in the neighbourhood of the British Isles, 
these names convey but little meaning, and to claim that they 
represent realities whose influence upon animal life is radically 
different — even to the point of life and death — savours almost 
of the fictitious. Yet there is no exaggeration. If you see 
a net lowered, as I have done, in the Great Belt, or the Cattegat 
or Christiania fjord, you will see that the catch in the surface 
waters is profoundly different from that in the depths, and 
that, when the net is raised from the bottom layers, the 
Medusae and Ctenophores and other salt-water species have 
been killed or paralysed by their passage through the super- 
ficial layers of brackish water. 
Similarly the Norwegian investigators have found that in 
those years when prolonged westerly winds in the spring 
months have checked the outflow of the Baltic current from 
the Skager-Rak, and banked up the Atlantic water against 
the coast, the Herrings come close inshore, within the island 
belt, to spawn, and a great fishery results ; whereas in other 
years, when the Baltic current is deep and wide, its cold waters 
