INTRODUCTION. 



Since tlie centrifuge has been introduced by Lohmann araong the methods of studying 

 plankton, the quantitative in- 

 vestigations of the diminutive 

 organisms hâve been possible. 

 To préserve the water sam pies 

 for låter examination Gran 

 (1912) used Flemmings stron- 

 ger solution. At the meeting 

 of the International Council in 

 Copenhagen April 1912 it was 

 decided, that in May-June 

 samples should be collected 

 according to Gran's method. 

 Much of the material has al- 

 ready been investigated, and 

 the results are to be found 

 in „ïhe Plankton Production" 

 by H. H. Gran. The Fin- 

 nish material collected in the 

 month of May 1912 will be 

 dealt with in the following 

 treatise. 



The samples were taken 

 at six stations, the geographica! 

 positions of which are shown 

 in the map of the figure 1 

 and noted in the table below: Fig. i. Position of the stations. 



