RHINCALANUS GIGAS 



30s 



water — that is water flowing out of the Weddell Sea with an average temperature for 

 the surface 100 m. between and i-o° C. (Sts. 779, 797, 798, 799, 806 and 808). At four 

 other stations in colder water, at which the average temperature was between — i -o and 

 0° C. (water in which ice has recently melted), that is at Sts. 795, 804, 807 and at 761 , near 

 the South Orkneys, the catch was likewise almost entirely in the lower nets. At all other 

 stations in water flowing out of the Weddell Sea the catch occurred mainly or entirely in 

 the upper nets. 



■ MORE THAN 500 

 ^ LESS THAN 500 



Fig- 13- 



Percentage of total catch of Rhincalanus gigas in upper and lower i-m. nets, 1931-2 and 1932-3. 



Weddell Sea. 



At the Stations in the "oldest" type of Weddell Sea water (o-i-o° C.) east of South 

 Georgia (Sts. 779, 797, 798, 799, 806), at which the catch was in the lower nets, it 

 seems reasonable to assume that the Rhincalanus population originated from the South 

 Atlantic and had been carried into water from the Weddell Sea by southward-moving 

 warm deep water. At Sts. 795, 804, and perhaps 807, in Weddell Sea water carrying 

 melting pack-ice, the origin of at least a part of the population is no doubt the same, and 



