RHINCALANUS GIGAS 301 



Owing to the refitting of the ship in Auckland and to other work around New Zealand 

 there are no observations for the two months July and August 1932. During September, 

 however, at the beginning of which month the ship left New Zealand for the last stages 

 of her circumpolar cruise across the Pacific Ocean, it was found that Rhincalaniis 

 had virtually disappeared from the catches. Only at St. 961, just south of the converg- 

 ence in the western Pacific, a catch of 26 individuals was obtained (Fig. 11). Rhincalanus 

 reappeared in the catches at St. 978 off Cape Horn in early October. 



Two processes, then, appear to take place during the winter months around the 

 Antarctic Continent — firstly, the restriction of Rhincalamis to the Antarctic zone so that 

 the species becomes wholly Antarctic instead of mainly Antarctic, and secondly the 

 diminution of the catches followed by the disappearance of Rhincalanus from the surface 

 250 m. after about mid-winter. It reappears in this layer again in the following spring. 



BATHYMETRICAL DISTRIBUTION, SEASONS 1931-2 AND 1932-3 



Falkland Sector (Table IV a) 



It is proposed now to deal with the bathymetrical distribution of R. gigas, so far as it 

 can be understood from these hauls, before considering the horizontal distribution in 

 the Falkland Sector during the second of the two seasons covered by this work, since the 

 horizontal distribution in the early part of the season 1932-3 can only be understood in 

 the light of the facts revealed by a study of the vertical movements of the species from 

 month to month. 



Although the two oblique towings made with the i-m. net from 250 to 100 m. and 

 from 100 to o m. do not give a very adequate picture of the vertical distribution and 

 movements of the plankton, yet some idea of the vertical movements from month to 

 month can be obtained from them. 



Fig. 12 shows the percentage of the total catch in the upper (loo-om. approx.) and 

 lower (250-100 m. approx.) hauls at stations in the Falkland Sector during November 

 and December 1931 and January and February 1932, between South Africa and Aus- 

 tralia in April 1932, and again in the Falkland Sector in October, November and 

 December 1932 and February 1933. All the catches illustrated in the diagram amount 

 to over 500 individuals in the combined hauls, with the exception of those shown in 

 lighter shading which represent hauls of more than 250 but less than 500 individuals. 

 The diagram does not include any stations in Weddell Sea water, since special conditions 

 appear to exist in that area so far as this species is concerned. 



A difference in the proportion of the catch taken in the upper and lower nets in sum- 

 mer and winter is immediately noticeable from the figure. This difference is most 

 pronounced between the winter months, April and October 1932, and the summer 

 months of the season 1932-3 (lower half of the figure), but is less clearly shown by 

 the diagram for the summer months of the previous season 193 1-2 (upper half of the 

 figure). 



During April 1932, in the South Indian Ocean, and October 1932, in the Drake 



