PREFACE 



history of every science affords examples of 

 J- the enormous stimulus to further research which 

 arises from the discovery of some new and sound 

 method of research ; and two such advances in 

 methods have transformed marine biology during 

 the last ten years. Late in the eighties of last 

 century some German physiologists began to estimate 

 the quantity of microscopic life contained in the sea 

 under each square metre of surface, and nets and 

 other apparatus were invented for this purpose. 

 About the beginning of the nineties some Scandi- 

 navian geographers and zoologists also began to 

 investigate the microscopic life of the sea with 

 respect to the physical conditions of the water. The 

 object of the Kiel quantitative plankton investigations 

 was to estimate the production of a sea area in much 

 the same way as a scientific agriculturalist attempts 

 to estimate the productivity of a cultivated land 

 area ; and that of the Scandinavian hydrographers 

 was to attempt to forecast seasonal changes in the 

 climatic conditions of their countries by studying the 

 currents of the sea. 



Now apart altogether from the primary objects 

 of these researches results were obtained which have 

 proved to be of great theoretical interest, so that the 

 original methods employed have been improved, and 



