146 



DISCOVERY REPORTS 



organisms and among the individual species. Apart from Euphausia superba the most 

 variable species are Metridia gerlachei, Calanus aaitas and Salpa fusiformis. 



The other stations in this area are WS 202 (Fig. 10) which was remarkable for a heavy 

 catch of Metridia (over 3000) and an exceptional number of Parathemisto (350), WS 380 

 and 381 (Fig. 1 1) at which the plankton was scarce except for a rather large number of 

 Salps, and Sts. 613-15 (Fig. 14) at which Salps were again quite plentiful and other 

 species scarce. 



It appears, therefore, that the area between the South Orkneys and the South Shet- 

 lands is characterized, like the eastern part of the Bellingshausen Sea, by a plankton 

 which is generally scarce, but which may be found here and there in comparatively large 

 quantities, usually due to the concentration of one particular species. 



THE NORTHERN ZONE 

 The lines of stations so far considered are those in waters which are covered by the 

 pack-ice during a large part of the year. Those next to be considered are mostly in 

 waters which are never reached by the ice. Numerous stations have been taken in this 

 area and we may consider first the lines crossing Drake Passage. There are three of these 

 lines (Figs. 11,12,14) and they are shown in Table XV, which gives for each station the 

 numbers of the ten most abundant species in this region. 



Table XV. Drake Passage 



The most northerly station in each of these three lines lies close to the Antarctic 

 convergence. 



The first three stations of the 1928-9 line, the first station of the 1929-30 line and 

 the first two stations of the 1 930-1 line are in the region of thin plankton, and will be 

 regarded as belonging to the Orkney-Shetland region. The others are in the normal 

 plankton of the northern zone. 



An inspection of Table XV will show that at WS 403 and WS 404, at Sts. 382-5, 



