52 



DISCOVERY REPORTS 



Thalassiosira antarctica also reached its greatest abundance in the western Weddell 

 Sea surface water round the southern end of the island (Fig. 20) and was comparatively 

 rare to the north and north-west. It was, however, ver^' widely distributed, being taken 

 at all but six stations on this survey. It occurred in the eastern Weddell Sea water in 

 considerable numbers. The minute form growing in gelatinous colonies which defied 



Fig. 19. The distribution of Chaetoceros socialis, South Georgia survey, November 1930. 



estimation was, however, confined to the densely populated region to the south-west 

 with the single exception of the anomalous St. 493 on the Larsen line. 



Chaetoceros negleclus (Fig. 21) was another widely distributed form, showing, how- 

 ever, a strong maximum to the south-west and south, where at some of the inshore 

 stations it occurred in such numbers as to render estimation impossible. This was due 

 chiefly to the presence of Ch. socialis at the same stations, as when this species was 

 absent it was found to be possible to count very large numbers of Ch. neglectiis. Here 

 again this species reached its maximum in water of western Weddell Sea origin ; to 

 the east and north-east, where stations were worked in water originating in the eastern 

 Weddell Sea, it was almost entirely absent. 



