of the Fishery Board for Scotland. 



303 



the following being the most remarkable : Thalassiosira Nordensldbldii, 

 T. gravida, Nitzschia seriata, Coscinodiscus excentricus var. Chostoceros 

 socialis, C. teres, C. scolopendra, C similis, C. diadema, &c. This 

 plankton belongs to the Arctic Sea, and arrives some years (as in 1895 and 

 1896, but not in 1894) at the coasts of Sweden in the end of January 

 or in February. It disappears in the spring almost completely. 



The plankton collected in the ' Research * expedition has no re- 

 semblance to 2, 3, and 4, but it has to 1, or tripos-plankton, and 

 may be considered as its Atlantic facies. A glance at the table 

 shows that the samples belong to two types, one characterised by the 

 scarcity of diatoms and abundance of cilioflagellates. The other shows 

 the contrary. Now, the samples rich in diatoms have been collected at 

 the loestern and the samples poor in diatoms at the eastern stations. 

 They belong evidently to two different kinds of water. There is thus 

 reason for distinguishing the two kinds of plankton as Styli (Sign S) 

 and TWpos-plankton (Sign Tp). The former comes no doubt from 

 the warmer Atlantic, and continues probably to Finmark and Beeren 

 Eiland, where it seems to arrive in September. The examination of 

 samples collected by the Swedish expedition to Spitsbergen, not yet 

 finished, has convinced me that there ruled at Beeren Eiland, in 

 the month of August, tricho-plankton, but in September styli- 

 plankton of nearly the same facies as at the coast of Sweden in 

 summer, that is, with Rhizosolenia graeiltima. Dr Fulton informs me 

 that the drift-bottles thrown out at the most westerly station, Knight 

 Errant 28, have not yet been returned. There ruled S plankton. On 

 the other hand, drift-bottles from the station Jackal II., where the plankton 

 was Tp, landed at Scotland. Bottles from Jackal XIII. (pi. Tp) did, 

 on the other hand, not land, but those from Jackal XVII. (pi. S) 

 drifted ashore in Scotland. This discrepancy might be explained by the 

 situation of the last-named stations at the boundaries between the two 

 kinds of water, but this explanation cannot be accepted without being 

 strengthened by the analysis of the water. That the drift-bottles from 

 the eastern stations landed on the coast of Scotland proves that the 

 water with Tp drifted to the south. The water with Tp had, the last 

 summer, a very wide extension in the north-eastern Atlantic as well as in 

 the North Sea. 



EXPLANATION OF PLATE. 



Fig. 1. Ceratium tripos, Ehb., typical (Sweden, summer-plankton), 

 150 t.m. 



Fig. 2. Ceratium tripos var. longipes, Bail (Sweden, winter-plankton), 

 150 t.m. 



Fig. 3. Ceratium tripos var. arctica, Ehb. (Baffins Bay), 150 t.m. 



Fig. 4. Ceratium tripos var. horrida, CI. (Shetland Islands), 

 150 t.m. 



Fig. 5. Ceratium tripos var. bucephalus, CI. (North Sea, Oct. 1896), 

 150 t.m. 



Fig. 6. Ceratium tripos var. macroeeros, Ehb. (the English Channel, 

 July 1896), 150 t.m. 



