I40 DISCOVERY REPORTS 



Of the three stations worked to the south-westward in February, the most easterly, 

 St. WS 508, showed a fairly rich phytoplankton with Corethron valdiviae strongly 

 dominant; but at the two others, so far the most southerly stations worked during the 

 course of these investigations, the phytoplankton was scanty. At St. WS 506 it was also 

 of a most peculiar nature, but St. WS 505 showed a phytoplankton of quite a usual 

 type, with Corethron valdiviae dominant, and a large variety of other forms present in 

 very small numbers, Nitzschia seriata being the only one of much significance. In the 

 peculiar catch from St. WS 506, the principal species were Nitzschia seriata, Rhizosolenia 

 truncata, Biddulphia striata, Corethrofi valdiviae, Nitzschia closterium, and Chaetoceros 

 neglectiis. Despite the time of year it will be noted that the temperature of the surface 

 water was extremely low, and the partial resemblance to the association met with farther 

 to the north-east earlier in the year will be noted. The most important difference lies 

 in the absence of Rhizosolenia gracillitna at the more southerly station. As the sequel 

 will show, this form appears to have a well-marked centre of distribution in the 

 extreme north-east of the Bellingshausen Sea proper, off Adelaide Island. 



In Table XLIV are shown the analyses of Sts. WS 496 and WS 498-501. It will be 

 seen from Fig. 71 that these stations, worked on the return from the first voyage into 

 the Bellingshausen Sea that season, form a line running from off Adelaide Island north- 

 eastwards outside the Biscoe Islands to the mouth of Neumayr Channel. At all four of 

 the southernmost stations on this line a very similar phytoplankton was encountered in 

 moderate quantity, with Corethron valdiviae strongly dominant throughout, and a fair 

 variety of other forms present, mostly in small numbers. At one station only, St. WS 498, 

 Rhizosolenia gracillima was important, but was even then outnumbered by Corethron 

 by more than two to one. Conditions at this station strongly suggest, however, that we 

 have here the first beginnings of the development of the richer association with these 

 two species co-dominant, observed to the north and east of Adelaide Island later in the 

 year. At the most northerly station on this line (St. WS 501), worked almost in the 

 mouth of Neumayr Channel, a rich local phytoplankton of the type described from two 

 stations in de Gerlache Strait and Schollaert Channel was encountered. The develop- 

 ment of this rich local flora probably takes place within the channels of the Palmer 

 Archipelago, and bears little direct relation to conditions in the Bellingshausen Sea. 

 Despite the comparatively small volume, the catch at this station was by far the richest 

 in point of numbers from the whole of this area. The reason for this apparent anomaly 

 will be readily understood by the enumeration of the leading forms : Chaetoceros neglectus, 

 Ch. tortissimtis, Thalassiosira antarctica, Fragilaria antarctica, Biddulphia striata, 

 Nitzschia closterium, Rhizosolenia truncata and Nitzschia seriata, the majority of these 

 being minute species. 



Before passing on to a description of the line of close stations taken off Adelaide 

 Island, two isolated stations worked far to the south-west, some three weeks later in 

 the year than those worked in the same locality by the ' Discovery 1 1 ' during the following 

 season, may be considered. The analyses of the phytoplankton hauls from these two 

 stations are given in Table XLV. At St. WS 502, the more southerly of the two, it will 



