14 DISCOVERY REPORTS 



in the northern part of this region, in the Orkney-Sandwich-Georgia area and west as 

 far as Elephant and Clarence Islands, by the R.R.S. 'Discovery II'. In January- 

 February 1931 the R.R.S. 'William Scoresby', finding ice conditions favourable, was 

 able to extend a most valuable series of observations from South Georgia south and east 

 of the South Sandwich Islands to 68° 53' S, 13° 03' W. The phytoplankton collected 

 on this cruise has proved of great value in interpreting the results obtained from the 

 other material collected to the north and west during the same season. During this 

 cruise the scientific work on the R.R.S. 'William Scoresby' was directed by Dr 

 N. A. Mackintosh. 



Three plankton surveys of the Bransfield Strait have been considered in this paper. 

 The first was carried out by the R.R.S. 'William Scoresby' in February 1929, when 

 Mr John was senior scientific officer, and the second by the same ship in November of 

 that year, when Mr G. W. Rayner was in charge of the scientific work. In December 

 1930 a survey worked by the R.R.S. ' Discovery II ' provided material showing the con- 

 ditions prevailing at mid-season in this area. It is therefore probable that from this 

 material valuable evidence as to seasonal changes will be obtained. 



Some scattered stations were taken in the Bellingshausen Sea by the R.R.S. ' William 

 Scoresby' during 1929-30, and a valuable line of close stations was worked off Adelaide 

 Island, the phytoplankton material from which shows striking agreement with that 

 found in the same locality the following year. Finally, in January 193 1, the R.R.S. 

 ' Discovery II ' worked forty-eight stations in this area at which phytoplankton material 

 was collected. Both ships have made a few stations, in the channels and outside the 

 islands, on their way to and from the Bellingshausen Sea, but at these the phytoplankton 

 appears to be of a rather local character. 



The numbers and in most cases the positions of all these stations will be found at the 

 top of the tables of analyses, for further information it is only necessary to refer to the 

 Station Lists, ^ at the end of which charts will be found showing the positions of all the 

 stations. 



METHODS 



The Gran net used for the capture of phytoplankton is made from the finest bolting 

 silk with 200 meshes to the linear inch, and the circular ring is 50 cm. in diameter. 

 A full description of this net will be found in Discovery Reports, vol. i, p. 183. A recent 

 innovation of protecting the net with a loose outer covering of stronger material has not 

 proved successful, owing to the ease with which small tears can develop unnoticed in 

 the silk net if it is not constantly watched when fished in bad weather. The speed of 

 hauling was as nearly as possible \ m. per second. In practice this was found to be 

 almost exactly the slowest speed at which the deck engine could be persuaded to turn 

 over without stopping on the top of a roll. 



The catches having been brought on board were transferred to tall glass cylinders 

 and fixed and preserved by the addition of the requisite proportion of strong formalin 



^ Discovery Reports, iii, pp. 1-132, Pis. i-x and iv, pp. 1-232, Pis. i-v. 



