KONGL. SV. VET. AKADKMIENS HANDLINGAR. 



BAND. 



35. 



n:o 



Rhizosolenia semispina, 

 Thalassiosira gravida, 

 T. Nordenskiöldii, 



Thalassiothrix Frauenfeldi. 



C. lineatum, 

 C. macroceros, 

 Cerataulina Bergonii 

 Chcetoceros curvisetus, 

 C. densus, 

 C. Schiittii, 

 Ditylum Bri'jhtwellii, 

 Eucampia Zodiacus, 

 Guinardia jiaccida, 

 Lauderia annulata, 

 Rhizosolenia Stolterfothii, 

 B. styliformis. 



Theve can lie no doubt that the southern forras have been transported from the 

 Avest of Scotland and the boreal species from the region of Iceland or the Färöes. Among 

 the southern forms we meet, although usually sparingly, a number of forms, which form 

 the didymus-plankton of autumn. It seems thus that this kind of plankton, or the sum- 

 mer- and antumn-plankton of the Continental coasts, originated, at least in part, from the 

 development of specimens from the west of Scotland carried towards the Dogger and 

 Fisher Banks and drifted through the depression of the bottom S. and E. of the Dogger 

 Bank towards the continental coasts. This doe.s not disprove that the didymus-plankton 

 may originate, in part. in the English Channel, an opinion I lield previously and for 

 which a number of facts can be adduced. 



If we now carry out a similar investigation for the plankton-forms of the bank- 

 water, we get the folloAving result: 



Southern or temperate forms 



Centropaf/es typicus, 

 OitJiona similis, 

 Evadue Nordmani. 

 Sagitta hipimctata, 

 Ceratium frijws, 



Boreal and arctic forms 



Fr it il /aria boreal is, 

 Acartia longiremis. 

 Calanus finmarchicus, 

 Pseudocalanus elongatus, 

 Temora longicornis, 

 Fl inge ila arctica, 

 Ptychocylis acuta, 

 Tintinnus bottnicus, 

 Pterosp/icera Möbii, 

 Dinophysis rotun data, 

 D. Vanhöffeni, 

 Peridinium depressum, 

 P. ovatum, 



P. pellucidum, . 



Asterionella Japonica, 

 Jiiddulphia nurita, , , i; 



