12 



PLANKTON-TYPES. TRICHO-PLANKTON 



^ . . Mean 

 Limits 



Lat.N. 'Z 

 perature 



P. pallidum ;.... 79°— 51° 8.5 



V. pellucidum 81°— 40° 5.i 



Phgeocystis Pouchetii 81°— 40° 5.8 



Asleromphalus Hookeri 80° — 40° 5.o 



Chaetoceros atlanticus 81° — 37° 5.i 



C. borealis 80°— 39° 4.3 



var. Brightwellii 76°— 41° 8.6 



C. criophilus 80°-40°(23) 6.2 



C. decipiens 81°— 40°(32) 7.6 



C. teres 81°— 42° 5.8 



CoscinodiscLis oculus iridis... 80° — 40° (6) 6.7 



Leptocylindrus danicus 81°— 58° (44) 7.o 



Nitzschia seriata 81°— 40° 8.8 



Rhizosolenia hebetata 77° — 45° 7.8 



R. obtusa 80°-41° 6.2 



l{. semispina 80° — 33° 7.o 



Thalassiosira gravida 80° — 40° 2.? 



Thalassiothrix longissima 77° — 21° 9.6 



It appears from this list, that most of the species have been 

 found as far north as 80°, several also, by the Nansen F^xpedition, 

 at 85° in the Polar Basin. Some of these species are circumpolar, 

 i. e. have been found in the Bering Sea and in the N. Pacific. 

 It thus seems as if the Northern Atlantic occasionally receives some 

 currents from the Polar Basin and ultimately from the Northern 

 Pacific. The currents may vary in different years, at least the 

 following facts point to such a conclusion. Rhizosolenia Jiebetata 

 was found in the Northern Atlantic in 1898, but not in 1899. 

 This species occurs in the Bering Sea. A number of Radiolaria, 

 not noted in the warmer Atlantic but certainly from the Pacific, 

 were also found in 1898, but not in 1899, in the Northern Atlantic 

 and W. of Norway. The copepod Onccea cunifera, which occurs 

 in the Pacific, was collected by Nansen at the New Siberian Islands, 

 in hauls from 50 metre. The same animal occurred in many samples, 

 collected in 1899 by the Nathorst Expedition to Greenland, but 1 

 have seen it but once in the temperate Atlantic at the Azores, and 

 then very sparingly. It was on the other hand not found in any 



