44 DISCOVERY REPORTS 



was the dominant form, with lesser numbers of Thalassiosira antarctica and Fragilaria 

 antarctica. At St. 488 a moderate proportion of Thalassiosira was found, but at the three 

 succeeding stations out to the end of the line it became comparatively scarce. Chaetoceros 

 criophihim was still dominant at St. 488 and the two succeeding stations, but at these 

 increasing proportions of Coretfirofi were found, and at the outermost station this form 

 was again dominant. 



It will be seen from the tables that except at St. 485 and the outermost stations on the 

 line the quantity of phytoplankton collected was not so great as that found almost 

 everywhere on the Larsen line previously described. The totals at Sts. 486, 487 and 488 

 were in fact among the smallest estimated on this survey. 



The general character of the phytoplankton indicates that most of the stations on this 

 line were worked in comparatively old water, mainly originating from the eastern 

 Weddell Sea type. The high proportion of Corethron at the two inshore stations indicates 

 that these were worked in the eddy off the north-east coast mentioned in connection 

 with the inshore stations on the previous line. At the outermost stations on the Prince 

 Olaf line the increase of Corethron and Chaetoceros neglectus, and the proportionate 

 decrease of the large Ch. criophilntn, are possibly indicative of mixing with old 

 Bellingshausen Sea water from the west, but more probably to the fact that the phyto- 

 plankton of the Weddell Sea water loses some of its sharply defined character as the 

 water gets older, so that the phytoplankton of all old Antarctic surface waters becomes 

 very much the same. 



The Bird Island line (Fig. 4) provided the smallest samples taken on this survey, 

 which is not surprising in view of the fact that it apparently cut into the old Bellings- 

 hausen Sea surface water to the north-west of the island. This water must have travelled 

 a great distance from its source of origin, and all our evidence goes to show that except 

 perhaps in autumn, the phytoplankton of the Bellingshausen Sea water reaches its 

 maximum when that water is comparatively young, an observation which has been con- 

 firmed by Mr John during the following (1931-2) season. 



From Table XI, in which the full analyses of the material collected on this line are 

 given, it will be seen that the flora encountered, though much smaller quantitatively, 

 was richer in species than that of the lines previously described. The numbers and pro- 

 portions of the leading forms are shown in Table 7. 



From this table it will be seen that at the inshore station Corethron valdiviae was en- 

 tirely dominant in the smallest catch, in point of numbers, obtained during this survey. 

 Probably this station was worked in surface water similar to that found at the inner- 

 most stations on the previous line. At the next three stations proceeding offshore the 

 influence of old eastern Weddell Sea surface water mixing with old Bellingshausen Sea 

 surface water approaching from the west was very clearly indicated. The dominant 

 forms Corethron, Chaetoceros criophihim and Thalassiosira antarctica, whose abundant 

 development is characteristic of the old eastern Weddell Sea type, show a steady decrease 

 in proportion, while the percentages of the small forms Fragilaria antarctica, Nitzschia 

 seriata and Chaetoceros neglectus, characteristic of the older Bellingshausen Sea water, 



