124 



DISCOVERY REPORTS 



line, and on the western line occurred in small numbers only at the two stations on 

 either side of Low Island. 



The small species Nitzschia seriata showed a much more scattered distribution on 

 this survey, as will be seen from Fig. 63. It was only abundant at one station, St. 

 WS 489, at the western end of the strait, and elsewhere was confined mainly to the north- 

 western stations. It occurred at three stations on the eastern line, two at the north in 

 the old Bellingshausen Sea water, and at the southernmost station in the eddy of 

 Weddell Sea water, but it was absent from St. WS 475 still farther to the north-east, 

 and at all the more easterly stations where it occurred it was present only in relatively 



Fig. 63. The distribution of Nitzschia seriata in Bransfield Strait, November 1929. 



I = one thousand. 



small numbers. From these facts it would seem that there is no extensive regeneration 

 of this species in the old Bellingshausen Sea water in the Bransfield Strait in early 

 spring, but that there is a certain amount of invasion from the west. A'^. seriata has been 

 found to be a most cosmopolitan species, present in abundance at some time or other 

 in almost every type of Antarctic surface water. Later in the year, when the influx of 

 Weddell Sea water into Bransfield Strait was at its strongest, it was found to have its 

 maximum there, but not approaching its abundance in the more oceanic areas studied. 

 The reason for the scarcity of this species in the Bransfield Strait at most seasons of the 

 year would appear to lie in the origin of the old Bellingshausen Sea surface water that 

 fills the greater part of the strait. This, as the dominance of Corethron valdiviae and the 

 invasion of Rhizosolenia gracillima clearly show, comes from the north-east of the 



