Alle disse planktonprover har jeg undersøgt paa 

 Ciliqflaf/eUafer og Diatomaceer; paa dette grundlag vikle 

 der derfor kunne gives en udvidet fortegnelse over plank- 

 tonfloraen i Nordhavet og ved Norges kyster. Men selv 

 en saadan fortegnelse maatte blive provisorisk; da under- 

 sogelserne fremdeles fortsættes, har jeg derfor ved denne 

 anledning ikke fundet det heldigt at give nogen samlet for- 

 tegnelse over alle hidtil fundne arter. Derimod har jeg 

 her indskrænket mig til dels at behandle Nordhavsexpedi- 

 tionens materiale, dels at give en kritisk oversigt over en- 

 kelte af de biologisk vigtigste slegter af pelagiske diatoma- 

 ceer. For disse slegters vedkommende har jeg da medtaget 

 alle de arter, som jeg har kunnet paavise ved vore kyster. 



Ved en anden anledning vil jeg saa meddele resulta- 

 tet af de øvrige undersøgelser og de slutninger, som jeg i 

 samarbeide med Dr. Johan Hjort og cand. real. Norågaarå 

 har kunnet drage om planktonalgernes biologiske forhold 

 og deres afhængighed af havstrømmene. 



Fra Nordhavs-expeditionen har jeg kun kunnet under- 

 søge planktonprover fra 13 forskjellige stationer; paa to af 

 disse prover var etiketten ulæselig, da blækket var falmet; 

 fem andre var indtørkede, saa at de før undersøgelsen 

 maatte koges med syre; derved blev de mulig tilstedevæ- 

 rende cilioflagellater ødelagte. 



Nedenstaaende tabel giver en ovei'sigt over provernes 

 indhold af D/atoniaceer, SiJicoJiagéllatey og CilioJhujeUater; 

 stationerne er opførte i kronologisk orden, de to usikre 

 tilslut under merkerne A og B. For hver station er an- 

 ført efter Molui (1887) og Tornøe (1880) bredde, længde 

 samt saavidt muligt temperatur og saltgehalt i overHaden 

 og i en dybde, som er angiven i meter under rul)rikken 

 „ dybde". 



I rubrikkerne for de forskjellige arter betegner c, at 

 vedkommende art forekommer almindelig, cc meget alminde- 

 Ug, r sparsomt, -|- temmelig hyppig. En saadan betegnel- 

 sesmaade er for vegetal)ilsk plankton forst benyttet af 

 Cleve (1894). 



Som tabellen viser, er indholdet af de forskjellige 

 prøver i det store og hele temmelig ensartet, og antallet 

 af arter er meget lidet i forhold til individantallet. Denne 

 ensformighed synes at være karakteristisk for oceanets plank- 

 ton, medens planktonet i de grundere kystbassiner til visse 

 aarstider ofte kan indeholde et meget større antal arter i 

 varieret blanding. Paa den anden side synes det ogsaa at 

 være en regel, at ensformigheden tiltager med voksende 

 bredde. 



De arter, som danner hovedmassen, er alle tidligere 

 kjendte som karakterformer i det nordlige Atlanterhav.*) 

 Fælles for alle stationer er TJialassiotlirix longissinnt] denne 

 alge tindes udbredt over hele det nordlige Atlanterhav og 

 kan undertiden folge det atlantiske vand ind til Norges 



*) ÅUe prøver tilhører Clcves type III, Trichojjkmkton {lSd6, 5) p. (i. 



In all these samples I have made investigations of 

 CRtoflagellaiu and Diatoiiiaceæ; and upon this basis an en- 

 larged list of the plankton tlora of the North Atlantic, 

 and the Norwegian coasts might therefore be given. Even 

 a list of this kind, however, could only be provisional ; and 

 as investigations are still being carried on, I have not, on 

 the present occasion, considered it advisable to give any 

 complete list of all tiie hitherto discovered species. I have, 

 on the contrary. confined myself partly to the treatment 

 of the N. Atlantic Expedition material, and partly to giving 

 a critical survey of a few of the biologically most impor- 

 tant genera of pelagic Diatomaceæ. As regards these 

 genera, I have included all the species that I could demon- 

 strate as belonging to our (the Norwegian) coasts. 



On some future occasion, I will impart tlie results 

 of the remaining investigations, and tlie conclusions to 

 which, in eollaboration with Dr. JoJicui Hjort and Mr. 

 Nordgaard, I have come concerning the biological condi- 

 tions of the plankton algæ, and tlieir dependenco on ocean 

 currents. 



I have been able to examine plankton samples from 

 only 13 different stations of the N. Atlantic Expedition. 

 Tlie laliel on two of these samples was illegible. the ink 

 having faded; 5 others had dried up, and had to be boiled 

 in acid liefore investigation. thereby causing the destruction 

 of any Cilioflagellata tliat might possibly have been present. 



The subjoiucd talilr gives a survey of the Diatoma- 

 ceæ, SiUcoJiagellata and Ciliofagellata contained in the 

 samples. The stations are placed in chronological order, 

 the two uncertain ones last, marked A and B. The lati- 

 tude, longitude and, as far as possible. the temperature 

 and saltness at the surface and at a depth given in metres 

 in the division „Depth", are given for every station accor- 

 ding to Mohn (1887) and Tornøe (1880). 



ln the divisions for the vai-ious species, c indicates 

 tliat the species referred to is of common occurrence, cc 

 very comnnni, /•, scarce, +, rather frequent. Tiiis mode 

 of describing vegetable plankton was first eniployt'd by 

 Cleve (1894). 



As the table shows, there is, on the wliole, ratiier a 

 sameness about the contents of the various samples; and 

 the number of species is very small in comparison witli the 

 number of specimens. This sameness appears to l)e clia- 

 racteristic of the ocean plankton, while that of the shallower 

 coast basins can often, at certain seasons, contain a mucli 

 larger number of species in a variety of combinations. On 

 the other iiand. it also nppears to be a rule tiiat unifor- 

 mity increases with the increase of latitude. 



The great bulk of the species are all already known 

 as characteristic forms of the North Atlantic Ocean. *) 

 Tlialassiothrix loiigisfiina is common to all stations; this 

 alga is found all over tiie N. Atlantic Ocean, and occa- 

 sionally accompanies the water of the Atlantic uii to tiie 



*) The samples all belong to Cleces type III, Trichoplaiikton (l>>',i() 

 5) p. 6. 



