E. Jorgens 



By assistance of Mr. Noedgaaed I have been aware that such a 

 washingover by the arctic waters across the Gulf Stream has really 

 been observed by the Swedish hydrog-raphers (Petteeson, L. 119), and 

 that just in the year 1898 the East Icelandic Polar Current by a 

 broad zone went across the Gulf Stream towards the Norwegian 

 coast. The Swedish hydrographers also suppose the arctic water 

 to force its way beneath the surface all into the Skagerak and 

 Kattegat, and Cleve thus explains the appearance there of arctic 

 planktonforms. They appear here earlier in the year than at the 

 Norwegian coast. 



When the arctic water reaches the coast, we find at once 

 the masses of (hatoms, which have already been developed on the 

 boundaries. 



As the preceding remarks will show, the southern inflow of 

 diatoms, according to my opinion, is especially due to the East Ice- 

 landic Polar Current, which under favourable circumstances advances 

 in the direction of somewhere near the Sogne Fiord. (As previously 

 mentioned, Gean makes Stadt the limit for some of the arctic 

 diatoms, which in this connection are of special importance). It is 

 possible that a similar washingovei- occurs regularly (by a very 

 broad wave?) further north on the coast of Lofoten (to the south 

 or north). Here, at certain times, a tongue of arctic water also 

 seems to be pushing its way across the Gulf Stream. 



I think it very possible that the specific northern forms in the 

 •northern diatom inflow may, in this way, be brought in with water 

 from about the latitude of Jan Mayen. It is, however, also quite 

 likely that it is the pre^^ously mentioned tongue of arctic water, trans- 

 versing the Gulf Stream at its narrowest part, which alone gives rise 

 to both the northern and southern inflow. 



If such ■ be the case, one might expect that the southern one 

 would expand southwards, and the northern northwards. There 

 would still be nothing to prevent the slight differences in their 

 components, as the noi'thern part of the current could bring with 

 it the specific northern forms, if from land, then from Jan Mayen 

 or perhaps East Greenland. 



The abundant material for observation which Cleve has collected 

 in his splendid work on the distribution of plankton organisms in 

 the Atlantic, (L. 40). makes it possible for one to get a view of 

 the distribution of the species. The specific northern forms may, 

 in accordance with the information there given, be supposed to 

 come from East Greenland or Jan Mayen. 



If tiie northern diatom inflow be due to the rushing in of a 

 noitiiein tongue of arctic water at Lofoten or thereabout (probably 

 in a wide expanse) one might expect the inflow from here to 

 stretch southwards on the one side, and in a north easterly di- 

 rection on the othei-. There was indeed, in the plankton examined, 

 a I'cason for the suggestion that the diatom inflow extended in an 

 easterly direction in the most northern part of Norway. 



Following close upon the inflow of diatoms, there is, on the 

 south west coast of Norway in the neighbourhood of Bergen, a very 

 sudden transition to much fresher water, containing a rich and 

 peculiar plankton of pi;rulinæa, which quickly takes the place of 

 the masses of diatoms. (Cf. E. Jøegensen L. 91) 



This is due, as far as I know, to the Baltic current which 

 now rushes in and sweeps the masses of diatoms out from the coast 

 and northwards. Therefore, it is reasonable that the characteristic 

 northern species cannot penetrate so far as to the latitude of 

 -Bergen. 



[n the above mentioned southern section of the Gulf Stream, 



during the expedition of S/S Heimdal in 1901, there were also 

 masses of diatoms on the boundary towards the oceanic water in 

 May, just at the time when the Baltic current has swept away 

 the diatom masses from the coast near Bergen. 



There is a certain correspondence between the characteristic 

 northern forms in the northern diatom inflow and the species which from 

 Geunow's and Cleve's works are known from the Kara Sea and 

 the north coast of Siberia. This might mean some kind of connection 

 between these seas, and one might easily be tempted to conclude 

 that water from the north coast of Siberia finds its way to the 

 north coast of Norway. 



In Gean's last work, a plankton sample is mentioned as taken 

 during the expedition of S/S Heimdal in 1900 in the Barents Sea, 

 west of Waigatch, and which contained several of the peculiar forms 

 found in the northern diatom inflow. 



Gean has kindly placed this sample at my disposition, and 

 after a thorough examination of it, I can affirm, that it contains a 

 large number of our northern plankton diatoms. On the other hand, 

 there are also so many foreign elements that it is scarcely Likely 

 that water from this district flows to our coast during the period 

 of the diatom inflow. On the contrary, everything (also the date 

 ^Vo) suggests that the masses of diatoms from the coast of Norway 

 (or the same inflow which gives rise to the northern inflow with 

 us) extend further eastwards (perhaps to the Kara Sea). 



The species found in plankton, and their distribution (prin- 

 cipally in the nearest seas) and remarks on the new or 

 critical forms. 



I. Bao±lla.nria,les. 



(Didtornaceæ). 



The suggestions which have hitherto been made as to a natm'al 

 classification of diatomaceæ are all more or less unsatisfactory. In 

 the following pages, I have principally availed myself of the system 

 used in Van Heueck's „Traite des Diatomacées" (L. 89); but in the 

 larger groups I have made some changes which I have found to be 

 necessary. 



A more complete list of literatui'e will be found in my pre- 

 vious paper (E. Jøegensen: Protophyten und Protozoen aus der 

 norwegischen Westkuste) (L. 91). Here I have only more com- 

 pletely cited the literature for the forms which ai-e not referred 

 to there. 



a. feiitrifæ Schitt. 



Coscin odisceæ. 



Under the heading „ distribution'", 1 have used the ordinary 

 expressions «oceanic", and „nei-itic" forms (= sea and coast forms). 

 As long as one (for diatomaceæ) does not know anything definite 

 about any rest period at the bottom, these expressions are far pre- 

 ferable to „holo"- and „meroplanktonic". 



In accordance with my opinion as stated above respecting the 

 inflow of diatoms in the spring I consider a large part of our 

 plankton species to be brought in from outside. 



There ai'c others which occur all the year round on our coasts, 

 although these of course also follow with the vai-ious currents. 



