PREFACE. 



I beg to acknowledge m y indebtedness to Professor H. H. Gran, of Christiania, 

 for his having kindly placed at my disposai the Finnish plankton material collected in 

 1912: I beg also to express my sincère gratitude to Dr. K. M. Levander, professor of 

 zoology at the Helsingfors University, for the way in which he has promoted my re- 

 search by recommending this paper for insertion in the „Acta" of the Finnish Society 

 of Sciences, as well as to the Society for the hospitality it has extended to my treatise. 



Christiania, September 27, 1919. 



CAROLINE LEEGAARD. 



