no DISCOVERY REPORTS 



It will be seen that at St. WS 382 a very moderate haul was obtained, in which 

 Corethron valdiviae was dominant, and Thalassiosira antarctica was present in fairly 

 large numbers. The littoral character of the surface water here was well shown by the 

 presence of a small species of Tintinnidae, which was found throughout the season in 

 Cumberland Bay, South Georgia, and has been frequently encountered elsewhere in 

 inshore waters. This may account for the comparatively large proportion of Th. antarctica 

 found here so late in the season, as it would appear that this species persisted in the 

 inshore waters on the northern side of the strait, though practically absent elsewhere 

 during the present survey. 



At each of the next four stations to the southward Corethron valdiviae was very 

 strongly dominant, in moderately rich hauls that showed a decrease as one proceeded 

 south. Other forms were present only in entirely subordinate numbers, and but few 

 species were recorded. The fairly high temperature of the upper layers, and the low 

 salinity at Sts. WS 385 and WS 386 indicate that the surface water here was of Bellings- 

 hausen Sea origin. At St. WS 387 a slight fall in temperature with a rise in salinity 

 indicated a slight degree of admixture with surface water from the Weddell Sea, and 

 this feature was more pronounced at the most southerly station, St. WS 388. The only 

 reflection of this change in the nature of the surface water in the phytoplankton was a 

 slight increase in the small numbers of Chaetoceros criophilum present, otherwise the 

 hauls were very similar to those obtained farther north, being moderate in quantity and 

 with Corethron vahiiviae very strongly dominant. 



On the two subsequent surveys worked earlier in the year the influence of the eddy 

 of western Weddell Sea surface water round Joinville Island was most marked, a con- 

 siderable increase in the number of species recorded, and in the proportion of small 

 forms to Corethron, being found in the vicinity of these last two stations, especially on 

 the December survey. The absence of any marked Weddell Sea influence on this autumn 

 survey bears out the observation made in the preceding section, that after mid-season 

 the flow of the western Weddell Sea current slackens and the nature of the phytoplankton 

 in areas previously affected by it undergoes just such a change as is indicated here 

 (see p. 104). 



Among the rarer species present on this line Rhizosolenia alata f. gracillima was only 

 recorded from the two northernmost stations. This form is hereinafter referred to as 

 Rh. gracillima for the sake of brevity. It has been observed abundantly to the north- 

 west of the Bellingshausen Sea slightly earHer in the year, in surface water which ap- 

 parently invades the Bransfield Strait from the west somewhat over a month later. Its 

 occurrence at these two stations only on the eastern line, and in small numbers, in- 

 dicates that this invasion was not complete at the time of the survey during the season 

 in question. 



The next line of stations was worked from a point south of Macfarlane Strait to a 

 point north-west of Astrolabe Island, forming a section across the middle of the deepest 

 basin of Bransfield Strait. At the most northerly station, St. WS 393, Corethron valdiviae 

 was again very strongly dominant in a moderate haul, but five other species of diatoms 



