12 PLANKTON-TYPES. TRICHO-PLANKTON 



Moan _, DiBtribution 



L'«»'f tem- '',"'" outBide 



^''^■^- perature '^"""^ the Atlantic 



P. pallidum 79°— 51° 8,5 34.87 



P. pellucidum 81°— 40° 5.i 34 38 



Phseocystis Pouchetii 81°— 40° 5.8 34.84 



Asteromphalus Hookeri 80°— 40° 5.o 34.49 Antarctic. 



ChsetOCerOS atlantiCUS 81° 37° 5.1 34.69 Bering Sea, Antarc. 



C. borealis 80°— 39° 4.3 34.36 Antarctic. 



var. Brightwellii 76°— 41° 8.6 35.oo 



C. criophilus 80°— 40°(23) 6.2 34.28 Antarctic. 



C. decipiens 81°— 40°(32) 7.6 34.5o North P. 



C. teres 81°— 42° 5.8 34.48 



Coscinodiscus oculus iridis... 80°— 40°(6) 6.7 34.4o Bering Sea. 



Leptocylindrus danicus 81°— 58° (44) 7.o 34.62 M. 



Nitzschia seriata 81°— 40° 8.8 35.i4 M? 



Rhizosoleniahebetata...., 77°— 45° 7.8 34.88 Bering Sea. 



R. obtusa.. 80°-41° 6.2 34.95 



R. semispina 80°— 33° 7.o 34.77 



Thalassiosira gravida 80° — 40° 2.? 34.08 



Thalassiothrix longissima 77° — 21° 9.6 34.48 Bering Sea. 



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

 found as far north as 80°, several also, by the Nansen Expedition, 

 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. Rhisosolenia hebetata 

 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 conifera, 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 see» it but once in the temperate Atlantic at the Azores, and 

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



