322 



DISCOVERY REPORTS 



descend below the loo-m. level before being fertilized, since at the majority of the 

 stations taken in the Drake Passage and Scotia Sea (Figs. 19, 20) during the spring 

 (193 1-2), the proportion of adults is a good deal higher in the lower than in the upper 

 nets especially after the end of November (p. 326). There is no marked diflFerence at 

 any time in the proportion of stage v female copepodites in the upper and lower nets. 

 As a comparison with the figures given in the above section for adult males in the 

 Falkland Sector during the summer seasons 193 1-2 and 1932-3, the following figures of 

 Schmaus and Lehnhofer (1927) may be quoted giving the numbers of adult males and 

 females collected by the ' Valdivia ' between November 29 and December 10, 1898, from 

 the region south of South Africa. The percentage of males which these figures represent 

 has been added. 



These hauls were taken with a vertical net 1-5 m. in diameter, fished from depths 

 between 1000 and 2000 m. to the surface. The percentages are about the same as those 

 found for the same time of year in the Falkland Sector in 1932, but slightly higher than 

 those for December 193 1. 



The approach of the stock to maturity. The discussion of the composition of the 

 Rhincalanus stock in stages, which forms the following section of this paper, shows that 

 in the season 193 1-2 the population reached maturity in December and that adults 

 began to predominate in the catches from about the end of the first week of that month. 

 In 1932-3 the population would seem to have become mature earlier. Adults pre- 

 dominated at all the stations from the middle of November onwards. Most of the 

 stations at the end of November and the beginning of December, however, were taken 

 in Weddell Sea water. In the first season, 193 1-2, there were no observations from 

 December2i to January 6, but on January 7 (St. 796) and on January 10 (Sts. 802 and 803) 

 adults were very few and a new generation had made its appearance and predominated 

 in the catches. Nauplii were taken on December 18 (St. 778). In the second season, 

 1932-3, observations were lacking for January and the new generation was taken in 

 February (Sts. 1116, 1117, 1125, 1127). 



COMPOSITION OF THE STOCK OF RHINCALANUS GIGAS 



The only examination of the population of R. gigas in Antarctic waters from the view- 

 point of the composition of the stock in copepodite stages which has yet been made is 

 that of Ottestad (1932) } This author examined the material from fourteen stations taken 



^ A further paper by Ottestad has appeared while this report was in the press, see pp. 293 and 356. 



