13 



results wiiich liavc at. least iiiformed me of certaiii conditions of tlie j)Iank- 

 ton wliich I have not kuown or iraagiued tlius, I shall give these results 

 already now. 



The first time I tried to use the uew apparatus was the 5. May 1897, 

 011 22 fathoms of water, uorth of Nordre Rønner near Læsø. (See table II, 

 column 7.) Measurements of the salinity showed here that we had from the 

 surface to a depth of 5 fathoms a salinity of 2,51 — 2,5, p. et., while the water 

 on 10 — 20 fathoms was about 8,4 p. et.; it was also somewhat colder down 

 here, and while the curreut above ran northwards, it ran southwards below. 

 Two quite different masses of water stood thus above one another here, a 

 pheuomenon which is rather common in the Cattegat; uay, it is almost the 

 rule at most piaces here. I must suppose that these two masses of water had 

 a very different plankton, and made a haul, therefore, with the closing-bag, 

 from 20 fathoms perpendicularly upwards to 10 fathoms, where it was closed. 

 A perpeudicular column of 10 fathoms of the salt water was thus tished 

 through, and proved to have rather a rich, brown diatom-plankton, which in 

 spirit immediately turned grass-greeu. The bag was well rinsed, and then we 

 made another haul from 5 fathoms to the surface. Also here was a rich dia- 

 tom -plankton, but it was white and had an appearance not unlike cotton. 

 Immediately, while on board, I felt convinced that these two masses of water 

 had thus quite a different plankton, and this, in a M^ay, is also correct; but a 

 later investigation showed (See table II) that, after all, on the whole it is the 

 same species of plankton we find in the plankton above and below, and that 

 this particularly holds good with respect to the commonest species there: 

 Chæloceros horeale and Thalassiothrix Frauenfeldii ; a number of rare forms are, 

 on the other hånd, found in the deeper, salt water only. This result was a 

 great surprise to me; first to find the plankton of the two masses of water 

 quite different in colour, and then to see under the microscope that both sorts of 

 plankton nevertheless, on the whole, consisted of the same species. Not till 

 it dawned upon me that all, or at any rate nearly all, the diatomaceæ in the 

 plankton of the upper water were colourless and filled with water, as also 

 generally without any trace of cell-substance, dead consequenUi/, while the same 

 species in the deeper water were strongly coloured and living, I got the full 

 uuderstauding of the matter. As I have not had much to do with diatomaceæ, 

 I have laid the question before Mr. H. Gran, and he has embraced my views 

 of the matter.*) 



*) After the above had been written, I saw in the >15. Annual Report of the Fishery 

 Board for Scotland, 1S96«, printed 1807, p. 215, that G. Mwray had made a eimilar discov- 



