i2 4 DISCOVERY REPORTS 



species except Eucalanus were present. Euphousia vallentini indeed was better re- 

 presented than during the 1927-8 survey. 



The conclusion to be derived from these facts is that, if the stations taken in March 

 1 930-1 are excepted, the order of the groups of stations according to the months in 

 which they were taken is also the order of "coldness " of the plankton population. Thus 

 the November survey had much the "coldest" plankton. Next comes the December- 

 January survey with still a distinct cold-water element, then the January-February 

 survey with a warm-water plankton, and then the February-March survey with a 

 similar plankton but with the sub-Antarctic E. vallentini and no Vanadis. There is no 

 doubt about the order of " coldness " of these four surveys, and although we are dealing 

 with four successive years it is highly probable that as the summer advances the South 

 Georgia plankton becomes "warmer and warmer". The April stations and the Sep- 

 tember survey reveal perhaps the "warmest" plankton of all. The cold-water species 

 taken in March 1 930-1 can be explained by the fact that that season was an exceptionally 

 cold one in which the pack-ice remained for a long time far north of its usual limits. 

 Whether the November plankton around South Georgia normally has quite such a 

 strong element of cold-water species as it did in 1930-1 is doubtful, but at all events 

 the evidence leaves no reasonable doubt: (i) that in the South Georgia plankton the 

 cold-water species are most strongly represented in the spring, and that as the summer 

 advances they are reduced and the warm-water species gain ground, and that the warm- 

 water plankton continues right through the winter ; (ii) that an abnormally cold summer 

 results in a "colder" plankton which however still becomes "warmer" as the summer 

 passes. 



There is evidence to show that changes of the same kind take place in other parts of 

 the Antarctic water, and it will be convenient first to take the eastern part of the area 

 covered by stations taken in 1927-31. 



THE SOUTH SANDWICH AND WEDDELL SEA REGION 



Table V shows, for various groups of stations in this region, the average number per 

 haul of the warm- and cold-water species. The species grouped under (d), (e), and (/) in 

 Table III, p. 107, and the neritic species Antarctomysis and Eiiphansia crystallorophias, 

 are omitted. 



In the 1927-8 season no cruise was made to the east or south-east of South Georgia, 

 but in September and October 1928-9 the ' William Scoresby ' took a number of stations 

 along the edge of the pack-ice which lay about 100 miles to the east of the island (see 

 Fig. 11). Two of the stations (WS 287 and 288) were taken late in September before 

 the winter survey of the South Georgia area had been finished. The ship then returned 

 to South Georgia, completed the survey and then carried out the other ice-edge stations 

 early in October (WS 298-310). We have seen that during this winter survey the 

 plankton was of a clearly warm-water type (see Table IV, September 1928-9, p. 122). 

 The short journey to the ice, however, brought the ship into an entirely different 

 plankton. Column 1 in Table V shows that there was here a typically cold-water 



