RHINCALANUS GIGAS 345 



of Weddell Sea water, where the stock is probably of mixed origin. It was also high 

 at stations in the Bellingshausen Sea current proper from the middle of November to the 

 end of December (Sts. 1021, 1054, 1063, 1066, 1083, see Table V b). A high proportion 

 of adult males was thus found in the catches from the middle of November to the end of 

 December in the season 1932-3, instead of from the middle of December to the end of 

 that month as in the season 193 1-2 (see p. 320, Table V a and Fig. 18). Since there were 

 no observations for January 1933 it is not possible to decide exactly when the catches 

 ceased to contain a high percentage of adult males during that season. 



Thus, in the season 1932-3, we find the stock of Rhincalanus reaching maturity from 

 the end of November and throughout December in the Bellingshausen Sea current, and 

 adult males appearing in the catches at the same time. Adult males therefore appeared 

 slightly earlier than in the previous season and the population became mature slightly 

 earlier also. In 193 1-2 the first station at which a mature stock was found was St. 763 

 (8. xii. 31), which was in Weddell Sea water, while at Sts. 774 and 775 (16. xii. 31) in the 

 Bellingshausen Sea current itself there was still a high proportion of stage v in the 

 catches. In 1932-3 the first station at which a mature stock was found was St. 103 1 

 (20. xi. 32) in Weddell Sea water and the first in the Bellingshausen Sea current was 

 St. 1054 (3. xii. 32). It may therefore be assumed that, since maturity was reached at 

 least a fortnight earlier and adult males made their appearance a month earlier, so also 

 spawning probably began earlier in this season than in the preceding one. Throughout 

 December, however, there was no appearance of nauplii or young stages such as would 

 indicate the hatching of eggs. At Sts. 1054 and 1056, north of South Georgia (3. xii 

 and 4. xii) there was a very small percentage of stage iii — 5 per cent and less — but these 

 hardly indicate that hatching had taken place recently or on an appreciable scale. It is 

 possible that spawning never took place around South Georgia during the month 

 of December on a scale large enough to produce a catch of nauplii in the i-m. net. 



During January 1933 the ' Discovery II ' was engaged in making a running survey of 

 the South Orkney Islands. During that month no plankton stations were taken, so that 

 observations for the month of January 1933 are unfortunately lacking. At the end of 

 that month and during the first week in February a number of plankton stations were 

 taken in the Bransfield Straits (Sts. 1097-1110; Fig. zb). R. gigas was almost com- 

 pletely absent from this area, as was found at the end of October and the beginning of 

 November. The next stations, therefore, at which samples of Rhincalanus large enough 

 to be analysed were taken, are those worked in the Drake Passage at the end of the first 

 week in February. 



Drake Passage, early February 1933 (Fig. 28, Table VI h) 

 At the most southerly station (1115) in the Drake Passage there was a small catch 

 in the lower nets only. The stock curve shows that it consisted of stages iv, v and vi. 

 At St. 1 1 16, the station to the north, the stock consisted of stages iv and v, without 

 the high percentage of adults found at St, 11 15. The latter station (11 15) was situated 

 just off the Antarctic continental shelf, in a position, again, where warm deep water wells 



