92 



DISCOVERY REPORTS 



these stations, but general information obtained at the others has aided the interpreta- 

 tion of the resuhs. The detailed analyses of the phytoplankton will be found in Table 

 XXVII. From previous descriptions it will at once be realized that the phytoplankton 

 at the three easternmost stations belonged mainly to the eastern Weddell Sea type, the 

 unusually low salinity for this type of surface water being undoubtedly due to the 

 extensive melting of pack-ice which was known to have covered a large part of the area 

 concerned only a short time before these observations were made. In order to render 

 the main features of the phytoplankton clearer than in the detailed analyses the relative 

 proportions of the leading forms at each station are shown in Table 15, as it is important 

 that intermediate conditions should be easily recognized in this region of complicated 

 surface currents. 



Table 15 



It will be seen that at St. 529, which was worked some distance to the south-east of 

 South Georgia, the eastern Weddell Sea character of the surface water is strongly in- 

 dicated by the dominance of Chaetoceros criophilum, and the position occupied among 

 the other more numerous species by Rhizosolenia styliformis and Corethron valdiviae. 

 Among the small forms so characteristic of surface water of the western Weddell Sea 

 type, which was found within about 30 miles of this position during the South Georgia 

 survey the month before, only Chaetoceros neglectus was of sufficient importance to give 

 any indication of mixing of the two types of surface w^ater. It will be seen that among 

 the other smaller forms listed above Nitzschia seriata and Chaetoceros dichaeta were the 

 most numerous at this station, where, however, they were of quite subordinate im- 

 portance. These two species have been found to be the most frequent of the smaller 

 species in surface water of the eastern Weddell Sea type, in which the three large species 

 first mentioned normally predominate to a marked extent, although their numbers 

 relative to one another vary enormously. 



At the very next station to be considered, St. 528, worked still farther to the south- 

 east, a good demonstration of this was given. The surface water here was certainly of 

 eastern Weddell Sea origin, and Rhizosolenia styliformis was strongly dominant. Both 



