44 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



form the plankton carried along in particular currents 

 of water, characterised by the temperature, the salinity, 

 and the microscopic fauna. It is possible by these 

 characters to recognise the currents, to trace their 

 variations from year to year, and so to some extent to 

 determine and predict the movements of the shoals of 

 fish. We owe this view chiefly to Professor G. O. Sars, 

 of Christiania. It is, then, to the physical conditions and 

 the biological contents of the water that the movements 

 of the Herring are due, and these are matters within the 

 scope of man's investigation, but outside his power to 

 regulate by local bye-laws, imperial legislation, or even 

 international treaty. This should be recognised by the 

 fishermen and by Sea-Fishery authorities. 



It follows, then, that one of the most important things 

 the Biologist can do to add to our knowledge of life in the 

 sea is to make a survey of the microscopic floating and 

 drifting life of the sea, and its relation on the one hand to 

 the physical conditions at the time (especially the 

 temperature and salinity of the water), and on the other 

 to the food materials found in the stomachs of the fish. 



The "pump plankton" method, which I described fully 

 before this Society last session, might do much if 

 systematically worked, but it seems difficult to induce 

 anyone on a ship, except a naturalist, to undertake such 

 work, and, moreover, the organisms collected may, unless 

 great care be taken, suffer so much damage in the process, 

 as to be difficult of identification. How, then, are we to 

 sample the plankton of our oceans? The attempt has 

 been made lately to arrange for the stoppage of a steamer 

 at certain fixed points in the ocean long enough to permit 

 of surface and deep-sea gatherings being taken. This 

 method is difficult to arrange, liable to failure, and very 

 expensive considering the very small number of observa- 



