10 P. T. CLEVE. PLANKTON, COLLECTED BY THE SWEDISH EXPEDITION TO GREENLAND. 



From the above list the following rarer forms have been excluded: 



Acartia Clausii GlESBR. 16 r. Acanthochiasma Kvohnii HKL. 16 r. 



Centropages typicus KRÖYEB, 17 r. Collozoum inerme J. Mull. 6 r. 

 Metridia hibernica BRADY & ROBTS. 16 r. Litolophus ligurinus HKL. 14 r. 



Microsetella atlantica BRADY & ROBTS. 8 r. Ccratium furca DUJ. 16 r. 



Temora longicornis O. F. MULL. 17 r. C. tripos NlTZSCH. 16 +, 17 r. 



Evadne Nordmanii LovÉx. 8 r. Coscinodiscus oculus iridis Ehb. 9 r. 



Acanthochiasma fusiforme HEL. 12 r. Rizosolenia styliformis Btw. 5 and 6 r. 



Near the east coast of Greenland water of a low salinity (31,5i) containing chiefly 

 Limacina helicina prevailed. S. of Jan Mayen the salinity increased to somewhat more 

 than 34 p. m., but the water was practically sterile. First at 68° 45' N. 10° W. Calanus 

 finmarchicus appeared in abundance and eontinued so across the whole northern Atlantic, 

 with the exception of the space 67° — 68° N. 4° — 6° W., where the water contained the 

 neritic Ceratium longipes, probably derived from Ieeland. 



If the plankton of the northern Atlantic in the spring be compared with that of the 

 autumn, it becoraes immediately apparent that great changes had occurred. Calanus fin- 

 marchicus was of little iraportance in the plankton that ruled during the spring on the 

 surface, but occurred abundantly in the deeper layers. When it occurred so abundantly 

 in September near the surface, it may be assumed that the deeper strata had during the 

 summer ascended to the surface. The great mäss of Ckcetoceros decipiens, that occurred 

 in the spring above the Norwegian Depth had in September disappeared completely. On 

 the other hand this species occurred in September more or less abundantly from the N. 

 of Spitzbergen to Beeren Island, so it may be assumed that the water containing c/iceto- 

 plankton migrated during the summer towards Spitzbergen. 



The Phwocystis Pouchetii, that prevailed during the spring both in the east above 

 the 200 metre plateau and in the west round Jan Mayen, had in September disappeared. 

 Its place had in the autumn been taken above the 200 metre plateau by tripos-plankton. 

 Round Jan Mayen the water was nearly sterile. 



The examination of the deep-sea hauls shews that the state at the station G, which 

 corresponds to the station E in June, had not been much changed, Calanus jinmarcliicus 

 being at both stations the most important species. But the more striking is the difference 

 of the plankton taken at the stations H, I, •/, which correspond to the stations D, C, B 

 in June. In fact, there exists not the slightest resemblance. In June there occurred the 

 same kind of triclio-plankton as at the station G, but in September the southern Rhizoso- 

 lenia gracillima constituted almost alone the bulk of the plankton. This species was 

 found abundantly both at Plymouth and in the Faröe Channel already in July and August. 

 To judge from observations in 1898 this species had advanced from the Bay of Biscay and 

 the region between the Azores and the European coast. The named species enters regu- 

 larly during the summer the plankton of the Baltic current of the Skagerak and in enor- 

 iiioiis quantities, but I never saw it abundantly in the North Sea, for which reason it 

 seems not improbable that it arrives in the Skagerak through the »Norske Rende». This 

 spc(;i(;s appears in the Skagerak usually in May, and in case the plankton at the stations 





