KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 57. N:0 7. 49 



Approaching the Norwegian coast, wefind the scanty diatomaceous plankton much 

 alike to that of the preceding station, only L&ptocylindrus is far more sparse, at least 

 from 20 m downwards. The water is equal to that, lying above the 20 m-level at S. Skag. 8. 

 Still at a depth of 200 m, temperature and salinity stay behind those of the 'JO m-level 

 a1 the latter station. 



A feature, not of ten niet with hitherto, is the fairly high degree of accumulation, 

 that diatoms and peridinians (cfr the following table) have undergone in a depth of 300 

 m, tlius near the bottom. Two species above all have heaped up here, viz. Thalassio- 

 thrix longissima and Biddulphia sinensis, bnt no spores of any kind were found. Such a 

 sedimentation as this may be of importance as a preparation for coming periods of flower- 

 ing, if it can only be shown that the sunken cells are really lifted up again alive and 

 capable of division. From my present knowledge I am, however, little bent to believe in 

 that possibilityforthe majority of cases, so much the more as such an hypothesis of deep- 

 circulation seems quite unnecessary for explaining the yearly regenerations of plankton- 

 crops. One or a few spread and erring cells, seldom totally lacking in middle and 

 upper layers even during long periods of rest, is all what is needed in order to secure a 

 coming development under favourable conditions. 



On the other hand, vertical convection currents will never reach depths surpassing 

 some50(— 100?) metres; compare the tables from November 1912. Also, there would really 

 be hardly any chances at all for such a whirling up on place, since the bottom-layers, 

 for all \ve know about the mighty deep-water dislocations even in comparatively isolated 

 fjords, cannot be expected to keep stationary from one flowering-season to another. 

 Only for half-benthonic species as Paralia sulcata or Biddulphia sinensis, horizontal 

 drifting in the depth may be considered a chief way of sprcading, whereas most other 

 species do not propagate, unless the v reach zones well provided with light. 



As to the fatc of those innumerable cells of plankton-algae, incessantly gaining the 

 depths by sinking during and after maxima of vegetation, one seems justified in suppos- 

 ing the main part of them to die away and get destroyed. This would account for the 

 remarkable seantiness of plankton, mostly characterising deeper zones in spite of an of ten 

 intensc pröduction near the surface. Bnt if we are brought to conclude a relatively rapid 

 råte of dissolution of the plankton-vegetation, after its leaving the centre of propagation, 

 what with sinking down slowly, what with following the currents, we may also expect to 

 find those organisms occasionally heaped up at the bottom, as soon as the råte of disso- 

 lution does not equal that of sinking or drifting away, to disappear låter on by dissolution. 



There is of course another alternative to be considered, namely that a rapid clearing 

 of the waters from large crops of phvtoplankton, consisting chiefly of diatoms, might be 

 the effect of consumption by animals. Though Mr Ostenfeld pleads for a large consump- 

 tion of the phytoplankton, I still feel inclined to expect the greater part of it reentering 

 into circulation by means of microorganisms, the marine formations probably not getting 

 directly eaten to any much larger extent than vegetations, meadows etc. on land. Such 

 an opinion would be in accordance with the interesting hypothesis of Putter, dealing 

 with the presence of organic compounds in sea-water to a rather imposing råte. Mr Gran 

 means to have got evidences for the accuracy of Putter' s hypothesis by some interesting 



K. Sv. Vet,. A.kad. Handl. Band 57. N:o 7. 7 



