96 DISCOVERY REPORTS 



at this time. Apart from the species named above, the only particular feature of this haul 

 apart from its bulk, was the occurrence of the spineless chain form of Corethmn valdiviae 

 in comparatively small numbers. It will be remembered that this was the form found 

 so abundantly in this area at the same time during the previous abnormally warm season, 

 and farther north close up to the Antarctic convergence and in sub-Antarctic water on 

 other occasions. From this and other observations farther south, it would seem that 

 there is a tendency towards the production of this vegetative form especially after mid- 

 season, but this tendency does not reach large dimensions unless favoured by com- 

 paratively high temperatures. 



Table i6 



St. WS 561 was worked slightly to the west of the very rich station described above 

 on the return trip eighteen days later. The very rich phytoplankton had evidently 

 drifted farther to the north during this time and only a moderately rich haul was ob- 

 tained. The nature of the phytoplankton was also rather different, but still very 

 characteristic of old eastern type Weddell Sea surface water. Chaetoceros criophilum 

 was strongly dominant, and Rhizosolenia styliformis the only other form of much 

 importance. 



As will be seen from the chart, the next station to be dealt with, St. WS 536, was 

 worked on the fringe of the transient belt of pack-ice between Zavodovski and Visokoi 

 Islands. The phytoplankton haul from this station was nothing like so rich in indi- 

 viduals as those obtained at the two stations previously described. Here the normal 

 spiny form of Corethron valdiviae was dominant, which would appear to indicate an 

 affinity with two stations worked farther to the south-east, Sts. WS 538 and WS 559, 

 to be described shortly, and also with St. 626 worked in this neighbourhood by the 

 'Discovery II' some three weeks later. At St. WS 536, though the haul was fairly rich 

 in species, the only forms besides Corethron that attained much importance were 

 Chaetoceros criophilum and Ch. neglectus. 



As we have seen, St. WS 537 was worked to the north-east when a way was being 

 sought round the pack-ice. Here the nature of the moderately rich phytoplankton was 



