148 DISCOVERY REPORTS 



68'' S, 70 and 80° W, are given in Table L. From this it will be seen that they were of 

 very moderate size and of such uniform composition that detailed description is un- 

 necessary. All the stations were worked in or near the pack. Corethron valdiviae and 

 Chaetoceros neglectus were dominant throughout, and there is a hint of grading off into 

 the associations found still farther west in the increasing numbers of Nitzschia seriata 

 and Fragilaria antarctica f. bouvet found at the more westerly of these stations. 



Table LI gives the analyses of the hauls taken between 66" and 68° 10' S, 80° and 

 90° W. Here the transition between the Corethron valdiviae — Chaetoceros neglectus 

 association and the more varied plankton found farther west was even more clearly 

 shown. At the two more easterly stations, near pack-ice, the above two species still pre- 

 dominated, and at the following station, St. 565, the catch was extremely scanty. From 

 then on Nitzschia seriata, Fragilaria antarctica and f. bouvet, Thalassiothrix antarctica, 

 Chaetoceros dichaeta and Thalassiosira antarctica became increasingly important, with 

 the first-named species dominant, except at the last station, St. 576, where Corethron 

 valdiviae and Chaetoceros neglectus were again the most numerous forms. This is perhaps 

 significant in view of the fact that pack-ice was again present, though still farther west 

 the rich Nitzschia — Fragilaria — Thalassiothrix association was encountered at two 

 stations in the ice. Table LI also illustrates the interesting fact that by far the richest 

 hauls were obtained at the two most northerly stations in comparatively old warm 

 surface water of relatively high sahnity. Apart from these two stations the hauls were of 

 moderate and fairly uniform quantity, except for the very poor catch at St. 565. 



The analyses from the most westerly stations included in Table LI I complete this 

 survey of the phytoplankton of the Bellmgshausen Sea. It will be seen that the eight 

 stations were situated between 67^45' and 69° 15' S, 90° and 102° W, and that the 

 phytoplankton was of a uniform and distinctive character throughout. Almost all the 

 stations yielded richer catches than the generality of those to the eastward, and a much 

 greater variety of species was present. At the first two stations Chaetoceros neglectus and 

 to a less extent Corethron valdiviae were still of some importance. Otherwise the 

 dominant forms in this rich and varied association were: Thalassiothrix antarctica, 

 Nitzschia seriata, Fragilaria antarctica and more especially f. bouvet, and Chaetoceros 

 dichaeta. Among the less numerous forms Thalassiosira antarctica and Rhizosolenia 

 truncata were prominent, and Chaetoceros criophiltim occurred in moderate numbers at 

 all the stations. Fair numbers of Ch. atlanticus were also present at some stations, this 

 being the only occasion on which this species was observed in quantity in the far south. 

 Generally speaking it appears to find its optimum in the older, warmer Antarctic surface 

 water just to the south of the convergence. The only other remarkable feature of these 

 stations was the large number of Ch. schimperianus recorded at St. 568. The phe- 

 nomenon of rafting of Thalassiothrix antarctica was very noticeable at these stations, 

 groups of four and eight individuals, with similar poles adherent, being common. This 

 was first noted by Schimper in material from the South-east Atlantic during the voyage 

 of the ' Valdivia '. 



