RHINCALANUS GIGAS 341 



carried up towards the surface in upwelling warm deep water in the divergence region 

 between the East and West Wind Drift currents. 



4. Adults were absent from the catches after the end of April and had, after that time, 

 presumably sunk out of reach of the 250-100 m. net. 



Drake Passage, October to mid-November 1932 

 (Fig. 26, Table VI /) 



When Rfimcalajius gigas reappeared in the catches in October 1932 on the line of 

 stations across the western end of the Drake Passage (Sts. 984-95) we find a remarkably 

 high proportion of adults in the catches. This is particularly noticeable in the lower 

 hauls at stations north of the convergence. In the upper nets a high proportion of 

 stages iv and v was present at each of the three stations north of the convergence, 

 while the catches in the lower nets at these stations were composed almost entirely of 

 adults. This might perhaps suggest that the younger stages rise to the surface earlier 

 in the season than the adults. At St. 978, at the beginning of October, we find a high 

 proportion of stage iii in the upper nets but the catch was too small to give a reliable 

 estimate of the population. The population generally seems to be in a much more ad- 

 vanced condition than in November 1931 in this same region. On the other hand at Sts. 

 1015, 1019 and 1021, about a fortnight later at the eastern end of the Drake Passage, the 

 population consisted of stages v and vi (adults) and was thus in the same condition as at 

 the end of November 193 1 in this area. This must be due to the growth of stage iv into 

 stage v in the fortnight intervening between these two north to south lines (Sts. 984- 

 95, 1015 and 1019). On the evidence available it is not possible to speculate much on 

 the condition of the population at the western end of the Drake Passage in October 1932. 

 The stages iv and v certainly belong to the winter-spawned generation, and the condition 

 of the ovaries (p. 318) indicates that the adults do also, since they were all "unripe" 

 or "maturing". Evidently a higher proportion of the winter-spawned generation had 

 reached the adult condition by the spring of 1932-3 than was the case in 193 1-2. 

 Comparison of the isotherm maps (Figs. 5 and 6) shows that the 2 and 3° isotherms 

 occupied a more southerly position in October 1932 than in November 193 1. It has 

 already been remarked that the season 193 1-2 was colder and later than 1932-3 in the 

 South Georgia region, and the same appears to have been true in the Drake Passage also. 

 This may perhaps account for the comparatively advanced condition of the overwintered 

 Rhincalatms population in October 1932 as compared with its condition in November 

 1931. The population, as was found in November 1931, seems to have advanced farther 

 in development north of the convergence than south of it, but there is no appearance 

 of stage iii in the coldest water such as occurred at Sts. 735 and 737. 



Scotia Sea and South Atlantic Ocean, mid-November to 

 mid-December 1932 (Fig. 27, Table VI ^) 

 At Sts. 1015, Id 9 and 1021, in the western Scotia Sea and in sub- Antarctic water 

 near the Falklands, we find the population in stages v and vi in the same condition as in 



