69 
this flora, but it is enormously great in the Limfjord. Nor have we any measure 
of the plankton production in the Limfjord; but to judge from my plankton 
investigations in 1898—01 (Vid. Selsk. Skrifter 6. R. XII. 3. 1903 pp. 18—19), 
the volumes do not seem in any way so great iu the Limfjord as at Lyø in the 
western Baltic. The shallow water of the Limfjord does not give so much room 
for planktion development as the much deeper western Baltic; for the latter we 
have from Hensen in his first great plankton work a preliminary endeavour 
to determine the annual production of the plankton per m.? in gm. of 
organic dry matter. He finds, that in addition to the quantity of plant plankton 
which is consumed by the plankton animals, there is produced here 14—16 gm. 
organic dry matter per m.? annually. This is obviously but a small quantity, even 
in this water, in comparison with the quantities of dry matter, which must be 
used by the bottom-fauna in the less plankton-rich waters of the Limfjord. 1 have 
already suggested (Report VII 1897 p. 23), that the quantity of the plankton in 
the Limfjord might perhaps have an appreciable influence on the food of the 
fish-stock from one year to another; I must now give up this idea; we must study 
the richer sources for the production of matter, to be able to find any such 
influence. 


XI. Conclusion. 
What we specially require to do in the future to round off these investi- 
gations, in addition to making more enumerations at different times of the year 
and studying the relation between producers and consumers as well as the weight 
of the animals, is to bring the plant belt under quantitative treatment, both 
in regard to the determination of the mass of the animals living there and the 
mass of the bottom-flora per m.? With the aid of a suitable motor-boat, I 
believe that this could be done. 
There remains also to obtain the best possible insight into the mass and 
food-consumption of the necton, especially of the fishes. It will only be when our 
knowledge both of the benthos and necton has advanced in the direction of 
quantitative determination, that we shall be able to estimate the importance of the 
plankton. By plankton I mean here living plankton organisms and what comes 
therefrom. The mass of their producers seems however, both from Lohmann's 
investigations and from Hensen's older work in the western Baltic, not to be of 
great importance for the benthos animals, as we must conclude, that they do not 
even satisfy, at any rate at certain times of the year, what the consumers of the 
plankton itself require for food; Lohmann refers therefore, to the dust-fine 
detritus in the sea as further source of food for the plankton animals; in the 
Limfjord this detritus is certainly in the main of benthos origin. 
We might perhaps sketch out the main lines of the conditions as follows; 
