300 DISCOVERY REPORTS 



During the fourth commission the phytoplankton estimations were carried out by 

 our assistant, Mr W. F. Fry, under the supervision of Mr J. W. S. Marr. The positions 

 of the stations considered here are shown in Figs. 6 and 7. Work in the Antarctic zone 

 was begun late in November 1935, on an eastward cruise along the ice-edge south of 

 the Indian Ocean. The observations were arranged along a series of zigzags with the 

 ice-edge as the southern turning point for each leg of the course, as in most of our long 

 range work. Quantities of phytoplankton were very moderate in both Intermediate 

 and Northern Regions, with indications of the beginning of the main increase at the 

 end of November. It may, of course, have been an exceptionally late season, but we 

 have subsequently found indications of similar moderate development in November, 

 followed by a very sudden main increase, in this part of the Northern Region. The 

 average position of the Antarctic convergence is slightly farther south there than it is to 

 the south of the Atlantic. At the same time, the land to the south is somewhat farther 

 north, so that to the south of the Indian Ocean a slight degree of ' telescoping ' in the 

 north-south gradient of the conditions may occur. This is probably the cause of the 

 incidence of the main increase being slightly later there, but the difference does not 

 seem to be sufficient to necessitate consideration of this region as a ' special area '. 



At the beginning of December it became necessary for the ship to proceed at once to 

 the rescue of Lincoln Elsworth at ' Little America'. This she did after a record passage 

 through the Ross Sea pack, and observations were resumed far south in the Ross Sea 

 at the middle of January 1936. Eighteen stations were worked south of the Antarctic 

 circle, some as far as 78° S. Most of the hauls were very moderate in quantity, as we 

 had already learnt to expect at this time of the year in the Southern Region. Two 

 stations yielded richer catches towards the end of the month. Mr Marr's preliminary 

 qualitative observations indicate that there are probably features peculiar to these most 

 southerly waters known, but quantitatively the results fit in quite normally with those 

 from the Southern Region in general. 



On the voyage northwards to Australia very small quantities of phytoplankton were 

 recorded in February in the Intermediate Region, and throughout the month of March 

 when the ship was working in the Northern and Intermediate Regions south of 

 Australia, the quantities observed were also poor. The summer post-maximal decrease 

 is evidently marked in these waters. Observations on the southward run suggested that 

 it may be even more marked in the Intermediate than in the Northern Region. 



After crossing the Indian Ocean westwards to South Africa in lower latitudes, obser- 

 vations in the Antarctic zone were resumed at the end of May and continued throughout 

 the first fortnight of June, between o and 20° E, where several results from the Inter- 

 mediate as well as the Northern Region were obtained. In the Intermediate Region 

 some vestiges of the autumnal secondary increase were still apparent — possibly as a 

 result of transport from farther south. To the north minimal winter values only were 

 recorded. 



The following season, after refitting at Simonstown, the ship crossed to South 

 Georgia on the usual zigzag type of course, the general direction being south-west. 



