STOCKHOLM, 1899. 113 



APPENDIX III. 

 About Plankton Investigations. 



I. For estimating the amount of plankton I propose that a method 

 be adopted founded on the following principles : — 



1. Separation of the organic matter in a certain quantity of water, 

 by means of centrifuge or by filtration. 



2, Determination of the amount of carbon and nitrogen by com- 

 bustion of the residuum in a vacuum tube by means of cupric oxide, 

 and determination of the nitrogen and the dioxide of carbon. 



P. T. Cleve. 



II. As it is desirable to know the amount of fat in the plankton, we 

 propose that a sample from each station be dried and extracted with 

 ether. A small quantity of the non-extracted material may be tested 

 on carbon or nitrogen, so that the total amount of fat in a certain 

 quantity of water can be calculated, the amount of organic carbon or 

 nitrogen (proposal I.) being known. 0. Pettersson. 



P. T. Cleve. 



III. It seems desirable that a systematic examination of the plankton 

 close above the bottom be carried out, especially on the fishing-banks. 



P. T. Cleve. 



IV. It seems desirable to examine the bottom-fauna (benthos) of the 

 fishing-banks of the North Sea at different seasons; for instance, by 

 counting the animals present in a certain volume of the mud, or on a 

 certain area of the bottom. P. T. Cleve. 



V. It seems to be of a certain importance to determine the amount 

 of carbon (organic), nitrogen, sulphur, and phosphorus in the bottom- 

 mud of the fishinsf-banks. P. T. Cleve. 



XEW SERIES. — VOL. VI. NO. 1. 



