RHINCALANUS GIGAS 319 



Four samples were examined from the line taken across the western Drake Passage in 

 October. The three samples from Sts. 988, 990 and 992 show a high percentage of un- 

 ripe or maturing females or of both. At the other station, 984, nearly all the females 

 were unripe. This was the most northerly station on the line and was in sub-Antarctic 

 water with an average temperature higher than 5-0° C. 



Five samples were examined from stations taken in the month of November. At the 

 most southerly (St. 1000), at which the average temperature for the surface 100 m. was 

 lower than — 1-5° C, and at the most northerly (St. 1021), at which the temperature was 

 again higher than 5-0° C, nearly all the females were unripe. At the two stations in the 

 area of maximum abundance of the species (Sts. 1019 and 1029) 36 and 30 per cent re- 

 spectively of ripe females were found and the remainder of the two samples consisted of 

 maturing females, many of which, at St. 1029 at any rate, were almost ripe. At St. 1033 

 again, taken in Weddell Sea water colder than 0° C, the majority of the adult females 

 were still maturing and 32 per cent were unripe. 



Three samples from stations taken in December were examined, two from Bellings- 

 hausen Sea water (1056 and 1063) and one from Weddell Sea water (1085). At St. 1056, 

 very early in the month, the sample consisted mainly of maturing females, with 26 per cent 

 which were ripe or nearly ripe. At St. 1063 in the middle of the month and St. 1085 at 

 the end of the month spent females made their appearance. The remainder of the sample 

 from St 1063 consisted of maturing females and ripe and unripe specimens in equal 

 proportions. At St. 1085 there was a large proportion of unripe and maturing specimens, 

 but while the proportion of "spent" females was high that of "ripe" females was 

 very small. The population at this station, which was taken in Weddell Sea water, 

 almost certainly contains a high proportion of females from the Weddell Sea area itself. 

 Thus the population is probably a mixture of matured and "spent" stock belonging 

 to the Bellingshausen Sea water and a still immature stock from the Weddell Sea water. 



Thus far the table indicates that the eggs were shed at the end of November and the 

 beginning of December in the waters of the Drake Passage and western Scotia Sea in 

 which the average temperature for the surface 100 m. lies between o and perhaps 3-0 

 or 4-0° C. At stations where the surface temperature is lower than cor higher than 3-0 or 

 4-0° C. the ripening ofthe eggs appears to suffer delay (Sts. 984, 1000, 102 1, 1033 and 1085). 



There are, unfortunately, no observations for January, but four samples were ex- 

 amined from stations taken in February. At St. 11 16, in the Drake Passage, a high 

 proportion of the sample consisted of spent females, but the proportion of maturing 

 females was also high. At Sts. 1125 and 1127 at the end of the month, between the 

 Falklands and South Georgia, the samples consisted mostly of unripe females (1125) or 

 maturing females (1127). The maturing females at these stations in February must 

 belong to a new generation resulting from eggs shed earlier in the summer, since ripe 

 females appeared in this region in November. Similarly at Sts. 1 148 and 1 150 in March, 

 taken in the East Wind Drift current flowing into the Weddell Sea, the unripe and 

 maturing females, of which the samples consisted, must also be an advancing new 



generation of adults. 



6-2 



