CIRCULATION OF THE M ACROPLANKTON 



407 



evidence that in the Bellingshausen Sea current and the Antarctic water of the West 

 Wind Drift Rhmcalanus gigas normally inhabits the surface layer in summer and the 

 deeper water in winter. There cannot then be very much doubt that the annual vertical 

 migration implied in this difference in vertical distribution normally takes place through- 

 out at least the greater part of the Antarctic. 



180° 



Fig. 9. Winter and summer stations in the western Pacific Ocean. 



THE PROCESS OF CIRCULATION 

 It has been shown in previous papers (Mackintosh, 1934; and Hardy and Gunther, 

 1935) that some species of the Antarctic macroplankton undergo extensive daily vertical 

 migrations while others do not. Most of the species considered on pp. 381 to 404 are not 

 much influenced by the alternation of daylight and darkness. This can be seen in most 

 cases by inspection of Tables III-XX. Four of them however do make daily migra- 

 tions, and move through a considerable range of depth. These are Pleiiromamma robusta, 



