ICONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 36. N:0 8. 11 



the Skagerak or the sira-plankton. Still, there remained a small quantity of ihe tripos- 

 plankton found in jMarch north of Norway. Mr. Gkan believes that this arctic plankton 

 ha.d developed on the coast-bank from spores, buried in the bottom-raud, or, to use his 

 own words, »Es ist am naturlichsten diese Erscheinung so zu erklären, dass die Diatomeen 

 nur da auftreten können, wo Dauersporen auf dem Meeresboden in nicht zu grossem 

 Tiefe vorhanden sind». Nevertheless, - Mr. Gran has not proved the presence of such 

 spores in the bottora-mud and, besides, of the 27 diatoms enumei-ated 12 have never been 

 found producing resting spores and of the 15 others many have been only very rarely 

 seen with resting spores. The plankton examined by Mr. Gran is exactly of the same 

 kind as found near the coasts of the Arctic Sea. I found it once, at the end of June 

 1898, at the north-west corner of Spitsbergen, but I have not x'eceived any similar sample 

 from Spitsbergen since. In my opinion this plankton is of foreign origin and had drifted 

 to Norway from Arctic regions. My opinion is supported by the map on p. 32 in Hjort's 

 paper »Fiskeri og Hvalfångst i det Xordlige Xorge» 1902. The eastern limit 1891 for 

 water containing Clione limacina comes there very close to the spöt where Mr. Gran's 

 plankton was collected. 



May 1901. 



Samples were collected throughout the month both at Måseskär and at Väderöboda. 

 The predominating plankton was in the beginning of the month chcuto-plankton but at the 

 end of the month tripos-plarikton. 



The same statistic as used above gave the following result 



Remnants from ,, rr, , 



April. -^e«'- Total. 



Southern oceanic '9 5 ( , „ 



Southern neritic ........ 3 2 I 



Northern oceanic 13 4( oc 



Northern neritic 17 il 



Plankton was also collected by the Norwegian vessel »Heimdal» (Gran 1. c. p. 156) 

 from 61°N. 5°E. to 67°— 68° N. 10° W., and thence to 68°N. 12°E. The plankton at 

 61° N. 5° — 3° E. was chiefly tripos-planhton. Of 26 noted species 17 were identical with 

 those noted off the west coast of Sweden. The other 9 are of no iraportance, except 

 Halosphcera viridis and Coscinodiscus oculus iridis. The former disappeared from the 

 Skagerak in February, the latter in the beginning of April. The plankton collected on 

 the route 62° — 64° N. 1° E. — 5° W. was, according to Gkan's data, completely different from 

 that in the east. Only 14 forms were common to both and most of them occurred in 

 the eastern part of the area. The remaining 31 forras can be classified as follows: 



Southern oceanic 3 



Southern neritic 3 



Northern oceanic 12 



Northern neritic ..... 13 



