has not been possible. The various larval forms of hivalres. snails, annelida, 

 echinoderms, which appear in it, are scarcelj' of any greater importance for the 

 present investigation, iiowever, and of other animals that may be said to be 

 common in the plankton gathered in, there are nearly only copepoda; tliese into 

 the bargain are all common species. To separate the animals from the plauts in 

 the plankton, so that they might be woighed separately, is impossible. Cen 

 trifugalising has been tried, but with no success. If we want more than a 

 rough estimate, there is nothing left but eounting, as Hensen has iutroduced 

 it. I suppose that the number of animals, in general, is much less variable 

 than that of the piants (Diatomaceæ), a rule wich also Hensen emphatically 

 lays down. 



A glance at the table shows us that, ou all three excursious, in October 

 1896 as well as in April and July 1897, the quantity of plankton in the North 

 Sea (1), in spite of the great depth which was fished through (8 — 9 fathoms), 

 is only 0,5— 1,5 gram, while in the fjord, where the water is not nearly so 

 deep, it most frequently is much greater, up to 16 and 27*) gram on a depth 

 of respectively 3 and 5 fathoms. I am sorry that four glasses, containing the 

 richest plankton belonging to the second excursiou, have been broken ou their 

 way home from Nonvay. Besides the measurements here stated I have a 

 great many more from the Limfjord from the first excursiou, which I have 

 left out, however, to give a clearer view; they showed also that there was a 

 very rich plankton, particularly in the western part of the Limfjord, at the 

 stations 3—4 — 5 — 6 — 7, many times richer, or denser, than the plankton in 

 the North Sea. The smaller catches in the Limfjord, ou the other haud, hail 

 from piaces as 7 a in Hvalpsund, where the salinity is ver}^ low on account 

 of the rivulets which here fall into the fjord, or from the long narrow eastern 

 part from Løgstør to Hals (stations 9 — 11), where the salinity is also lower 

 that at the western stations 4 — 7. Not even the Cattegat (see No. 12 — 13) 

 could, in October, boast such a great quantity of jilankton per surface unit 

 as the western part of the Limfjord, and in the Baltic Sea there was scarcely 

 any diatom-plankton whatever at that time. 



Ou the basis of the measurements before us, it may then be said that 

 the western part of tlie Limfjord in its main course [stations 3 — 7), frotn spring 

 till aidmnn, at least at the three points of time tvhen tve sfudied it, had a planlc- 

 ton tvhose weight per D nieter snrface of the sea, even irrespective of the slight 



•) These two numbers are the results of measurements of fresh plankton, and they 

 are considerably greater than they would have been, if we had weifjlied i)lankton that 

 had been kept tor some time. 



