MARINE BIOLOGICAL STATION AT PORT ERIN. 71 



which can probably be ascertained, and thus lead to the 

 possibility of correlation with prediction within limits. 



Observations made by Nansen and Helland-Hansen, in 

 1909, showed that variations in the Atlantic currents have an 

 important influence upon the physical conditions not only of 

 the Norwegian sea, but also of the atmosphere and the climate 

 on land, and so upon the development of both marine and 

 terrestrial life. It was shown that variations in the temperature 

 of the Atlantic water were followed by corresponding variations 

 in the winter climate of Norway, in the fisheries of the North 

 Sea and at Lofoten. There was, moreover, a remarkable 

 correspondence between the annual variations in the Atlantic 

 surface temperatures in May and the variations in the harvests 

 and even in the growth of the pine forests in Norway. As the 

 Prince of Monaco puts it : — " Le plankton est, en effet, un 

 veritable ' temoin ' des phenomenes physiques qui s'accomplis- 

 sent dans Focean." And M. Cligny, of the Station Aquicole 

 at Boulogne, has shown that the enormous banks of herrings 

 which have been trawled from the bottom at several localities 

 round the British Islands of late years, cannot be correlated 

 with any peculiarity of bottom nor depth, nor even with 

 temperature and salinity, but are on the borders where the 

 Atlantic and the coastal waters meet, and where the oceanic 

 water has brought in an unusual supply of plankton — such as 

 the Pteropod Limacina retroversa. The Swedish and Danish 

 hydrographers have similarly established that there is a direct 

 connection between the Bohuslan herring fishery and the 

 invasion of the Skaggerrak by Salter water from the North Sea 

 meeting and pushing back the less salt Baltic water. 



That different currents or bodies 01 water in the sea differ 

 very notably in their plankton is well known to biologists who 

 have tested the matter. For example, in crossing the Atlanl ic 

 to Canada one can tell to a nicety, even by means of a small silk 

 net attached to a bath tap on a passenger steamer, when the 



