RHINCALANUS GIGAS 337 



colder than — 1-5° C. many individuals do not develop beyond stage iii before the 

 spring (pp. 324, 326). 



3. In the Scotia Sea and around South Georgia the population was found to be 

 mature (in the adult stage) about the end of the first week in December (p. 326). 



4. Nauplii and very young stages were taken at one station in South Atlantic water of 

 Bellingshausen Sea origin in the middle of December (St. 778, 18. xii. 31). At the end 

 of the first week in January in this water an advancing summer generation was found in 

 stage iii (p. 326). 



5. In the oldest type of Weddell Sea water (o-i-o° C), the population was mainly 

 in stage v — except at Sts. 763, 765, 768 and 779, where it was mainly in the adult stage 

 (stage vi) (p. 330). 



6. In water flowing out of the Weddell Sea having an average temperature for 

 o-ioo m. below 0° C. the population consisted almost entirely of adults and was taken 

 in the upper nets. No young forms were found at all. In water flowing into the 

 Weddell Sea along the coast of Coats Land south of 66° S the population consisted 

 mostly of stage iv and was found in the lower nets (p. 332). 



7. A population again in stage iii was found at one station (825) in late January in the 

 Scotia Sea south of South Georgia (p. 334). 



8. Between the Falklands and South Georgia in the middle of February two stocks 

 were found — one in stages iv, v and vi in warmer Antarctic water and another in stages 

 iii and iv in colder Antarctic water near South Georgia. A much reduced yoimg 

 population was taken in sub-Antarctic water (p. 336). 



9. From the above facts it has been concluded that the spawning of R.gigas took place 

 during the season 193 1-2, in the Falkland Sector, in December and probably throughout 

 January. It occurred first in Antarctic water from the Bellingshausen Sea in the South 

 Atlantic, where the temperature was between i-o and about 4-0° C. Spawning in the 

 Scotia Sea and eastern Drake Passage took place later, also in water from the Bellings- 

 hausen Sea. There is evidence that the spawning everywhere took place earlier in 

 warmer than in colder Antarctic water. The part of the Rhincalamis stock belonging 

 to the Bellingshausen Sea current which drifted into the "oldest" type of Weddell 

 Sea water (o-i-o° C.) failed to reach maturity by the middle of January. No spawning 

 at all apparently took place in Weddell Sea water with a temperature below 0° C. at least 

 before the end of January. The population found in the southern Weddell Sea, in the 

 middle of January, in water flowing in from the east south of 66° S, was judged to be 

 the same advancing summer generation as was found in the South Atlantic at the 

 beginning of the month. The population of the Weddell Sea is thought to result from 

 an invasion from an outside area and to be carried into the Weddell Sea either in 

 Atlantic warm deep water, or in the deep current originating in the South Indian Ocean 

 which flows into the Weddell Sea south of 66° S along the coast of Coats Land. A late 

 and much reduced spawning appears to have taken place in sub-Antarctic water. 



