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igate their distribution within the individual divisions of the area, and the per- 

 iods of the year at which they occurred in the plankton. Then came the quest- 

 ion of the quantity in which these organisms were to be found in different 

 places and at different times of the year. Not until all these questions are sett- 

 led it is possible to attempt other investigations more closely connected with 

 the importance of the plankton to the other animal Hfe of the sea, and fish in 

 particular. 



2. Qualitative Investigations. 



For the first seven or eight years of the international co-operation, there- 

 fore, the plankton investigations, in so far as they stood in direct relation to 

 the international programme, consisted chiefly of collecting samples of plankton 

 during the hydrographical cruises. The lengthy work of examining the samples 

 collected, with their numerous organisms of different kinds, took up the greater 

 part of the time and scientific effort which the various countries were able to 

 devote to the study of plankton, and as a result, a great number of tables were 

 published giving the plankton organisms and their appearance in various parts 

 of the international area. The value of these tables, however, would first be- 

 come apparent when they were properly worked together, and the plankton 

 specialists have therefore, during the last few years, been working out a com- 

 pilation (Résumé), as accurate as circumstances permit, of this very extensive 

 and complicated material. This compilation, of which the first parts have been 

 published, is not yet complete; it is however already possible to say that even 

 though much of the matter in the tables has proved to be of little value or re- 

 liability, we are now in possession of knowledge which is in the main 

 sufficient, with regard to the distribution and occurrence of 

 most of the plankton organisms^) in the greatest and most im- 

 portant part of the area, viz. the Channel, the North Sea, the Skagerak, 

 Kattegat and the Baltic; our knowledge is less accurate as regards the plankton 

 of the Norwegian Sea, the Faroe-Shetland Channel, and the open ocean west 

 of Ireland and between Iceland and the Faroes, as well as in the most northerly 

 part of the area (the Murman Sea), it having proved impossible to undertake 

 investigations in these regions with the same regularity or frequency as in the 

 first mentioned waters. 



As an example of the information obtained by this treatment of the 

 plankton tables, a few words may be said about the distribution of species of 

 one of the most important groups of animals, the copepoda (small crustaceans), 

 which are of great importance as food for the so-called pelagic fishes (Clupeidse 

 and mackerel), as well as for the pelagic larval stages of other fishes. A com- 



') This statement does not refer to the Nannoplankton which consists of very minute 

 forms which pass through the finest silk net. 



