KONGL. SV. VET. AKADEMIENS HANULINGAK. BAND. 20. N:0 5. 



55 



northern Pacific, after these seas had received their present limits and physical nature ^). 

 It seems as if J. G. Agardh inclined to the opinion that these species common to both 

 the regions in question have had their origin in either of thein and have been brought 

 from this region into the other by a current continued through all the Arctic Seas. 

 Agardh says: »Thongh it appears to be true in general with regard to the algas, that 

 the distribution of a species is confined to the limits of the same sea-current, still the 

 fact of many larger algte occurring both in the Atlantic and the Pacific may possibly 

 indicate the existence of a current continued through the Arctic Seas, which might 

 carry algte from New-Foundland and Spitzbergen to Kamtshatka and the most northern 

 isles of Western America» ^). The hydrographical researches, carried on in the Arctic 

 Seas by the Polar expeditions of låter times, have not, however, demonstrated the exi- 

 stence of such a continued current, having rather proved, on the contrary, that there is 

 in the Arctic Sea a whole net-work of currents. Only by supposing a species to have 

 been removed from one current into another, its occurrence both in the Pacific and 

 the Atlantic could be explained from the influence of sea-currents, and such a combi- 

 nation would be so complicated with regard to several species as to be hardly admissible. 

 It might be supposed, indeed, that such a current existed during previous periods; but 

 I do not know af any reasons for such a supposition. Without entering into this 

 question in general, I will only remark, that in my opinion the occurrence of several 

 alga3 in the northern Atlantic at the same time as in the Pacific may probably be ex- 

 plained by the former distribution of water and land and the different physical con- 

 ditions of the seas in former times as compared with their present state. The study 

 of the present distribution of the alga3 of the Arctic Seas leads to such a conclusion. 

 According to pretty reliable statements, the foUowing arctic algse are to be found in 

 the northern Atlantic as well as in the northern Pacific. 



Corallina officinalis? 

 *Lithothamnion polymorphum, 

 *Odonthalia dentata, 

 *Rhodomela lycopodioides, 

 Polysiphonia parasitica? 

 ') urceolata? 



» fastigiata? 



» atrorubescens ? 



n nigrescens, 



Delesseria alata? 



* 



» si nu os a, 



*Hildbrandtia rosea, 



Peyssonnelia Dubyi, 

 *Rhodophyllis dichotoma, 

 *Euthora cristata, 



Plocamium coccineum, 

 *Rhodymenia palmata, 

 •"Halosaccion ramentaceum, 



Duraontia filiformis, 



Callophyllis laciniata? 

 *Ahnfeltia plicata, 



Gigartina mamillosa? 



Chondrus crispus? 

 *Ceraniium rubrum, 

 *Ptilota plumosa, 



* » pectinata, 

 Callithamnion polyspermum, 



» arbuscula, 



Antithamnion fioccosum? 



* i> araericanum, 



') Cp. Engler, Pflaiizenw. p. IX— X. 



-) J. G. Agardh. Spetsb. X]g. Bidr. p. 10. 



