RHINCALANUS GIGAS 323 



in the season 1929-30 by the ' Vikingen ' and one taken by the ' Norvegia ' in 1928. Some 

 of these stations were taken in water flowing out of the Weddell Sea between the South 

 Sandwich Islands and Bouvet Island, and some in Weddell Sea water south of the South 

 Sandwich Islands and east of the South Orkneys. 



The conclusions at which Ottestad arrived from the data at his disposal will be 

 seen to be largely confirmed in what follows. He found that two age groups were dis- 

 tinguishable in the population taken at the earlier 'Vikingen' stations at the end of 

 November and early December. One of these consisted of stages ii, iii and iv, and the 

 other, the older one, of stages iv, v and vi. In the latter half of December the older of 

 these two groups had disappeared. At the Norvegia station, taken in mid-January 1928, 

 the older group had disappeared and the younger group had advanced to stages iv, v 

 and vi. Ottestad concluded (p. 51), since he never found nauplii or stage i at any of the 

 stations taken by the ' Vikingen ', " that the stock existing in the Weddell Sea is due to an 

 invasion from another spawning area". He suggested that Rhincahttus spends the 

 winter in deep water, rising to the surface before spawning in the spring, and is carried 

 into the Weddell Sea by the "Antarctic Intermediate water" (warm deep water — 

 Deacon, 1933). Of these two last assumptions we have already seen that the former 

 is very strongly supported by the data collected by the ' Discovery II '. The latter assump- 

 tion we also believe to be correct, though Rhincalanus is probably carried into the Wed- 

 dell Sea to a greater extent by warm deep water originating in the South Indian Ocean 

 (East Wind Drift current) than by water originating in the South Atlantic. 



Finally, Ottestad writes (p. 51): "No renewal of the stock takes place in the Weddell 

 Sea as the mature stock disappears without previously spawning. . .neither is it possible 

 to prove that spawning of this species takes place in the Weddell Sea." 



In the present work the copepodite stages were identified according to the description 

 of Schmaus and Lehnhofer (1927). There are, as usual, five copepodite stages between 

 the nauplius and the adult, which is counted as stage vi. Stages iii, iv and v were of 

 frequent occurrence in the hauls, but stages i and ii occurred less frequently and only, 

 presumably, when present in the water in such abundance that they could not all 

 escape through the meshes of the stramin net. Nauplii occurred even less frequently 

 and, again, only presumably when present in immense numbers in the water. It can 

 hardly be expected, therefore, that the numbers of the younger copepodite stages taken 

 in these hauls will be very accurate or give more than an approximate picture of the 

 condition of the population at the stations where they occur. 



Drake Passage and South Atlantic Ocean, November 193 1 

 (Fig. 19, Table VI a) 



Fig. 19 shows the percentage of the various copepodite stages in the catches in the 

 upper and lower nets at stations in the Drake Passage and western Scotia Sea from the 

 middle to the end of November 1 93 1 . At the end of November the dominant stages are 

 iv and v at nearly all stations in the Drake Passage. However, it will be noticed that at 

 stations north of the Antarctic convergence (Sts. 725-7, 750 and 751, at the beginning 



