354 ■ DISCOVERY REPORTS 



Sea in March 1933 might perhaps suggest that some degree of spawning may take place 

 in the warmer water of Weddell Sea origin much later in the season than the main 

 spawning in waters of Bellingshausen Sea origin. The station in question here, how- 

 ever, certainly does not provide sufficient evidence for a statement on this point. 



In both seasons, between the Falklands and South Georgia, a similar state of affairs 

 was found — a maturing summer generation in warm Antarctic water near the con- 

 vergence and a younger generation in colder water near South Georgia. Similarly in the 

 Drake Passage in February 1933 the summer generation was found to be much older in 

 warmer Antarctic water than in colder water farther south. Appearances suggest that 

 in both seasons spawning took place later in the colder than in the warmer Antarctic 

 water. In 193 1-2 it took place later in the Scotia Sea, south-west of South Georgia 

 (St. 825), than in South Atlantic water east of the island, and further the stock 

 spawned in the Scotia Sea was found in February of both seasons, between the Falklands 

 and South Georgia, to be of the same age, so that the presumption is that spawning 

 occurred at roughly the same time in the Scotia Sea in both years. In the season 193 1-2 

 spawning began in early December in the South Atlantic, in water of Bellingshausen 

 Sea origin, east of South Georgia and spread later into the Scotia Sea. In 1932-3 there 

 is also evidence that spawning took place first in the warmer Antarctic water and later 

 spread into the colder waters of the Scotia Sea, and in the Drake Passage in this season 

 there is evidence of a similar movement of the spawning southwards from warmer into 

 colder water. There is thus discernible in both seasons a trend of the spawning south- 

 ward as the summer advances. 



DISCUSSION 



The conditions revealed by the stock curves for the latter half of the seasons 193 1-2 

 and 1932-3 do not admit of any straightforward explanation. We saw that in the Ant- 

 arctic water flowing northwards from the Drake Passage and Bellingshausen Sea the 

 Rhincalanus population came to maturity in late November or in December around South 

 Georgia. Adult males appeared in the lower nets at that time, and one may assume 

 that the main spawning occurred then. It is evident, however, that during both seasons 

 a number of different populations was sampled having difTerent ages in different regions, 

 even when allowance has been made for patching and swarming and for the inaccuracies 

 of the type of net employed. 



In the season 193 1-2, at least three age groups were found east of South Georgia in 

 January. In Bellingshausen Sea water, in the South Atlantic Ocean, there was an 

 advancing summer generation. In Weddell Sea water of a certain temperature (between 

 o and i-o° C.) there was a population mainly in copepodite stage v, which was presumed 

 to have been carried southward in the Atlantic warm deep water, and in Weddell Sea 

 water with a temperature below 0° C. there was a population consisting almost entirely 

 of adults. At the end of January 1932 a station (825) near the boundary between 

 Weddell Sea and Bellingshausen Sea water near South Georgia showed a population 



