DISTRIBUTION OF ANTARCTIC MACROPLANKTON 155 



travelling and those which are not, and it is almost certain that the whales are influenced 

 by the position of the pack-ice, the proximity of which is not necessary to the existence 

 of "krill". Ruud (1932), in studying the connection between the whaling grounds and 

 the distribution of Euphaiisia superba, points out that the "krill " is widely distributed 

 in Antarctic waters, but suggests that the principal feeding grounds of the whales are in 

 the "areas of convergence, backwaters, vortices of mixed layers, and in the centre of 

 areas with a cyclonic motion ", where a special concentration of ' ' krill " is brought about. 

 Since the present paper is concerned only with the distribution of the macroplankton 

 as a whole, these conclusions cannot be examined in detail, but there are certain aspects 

 of the distribution of the macroplankton which may have a bearing on them. We have 

 seen that in the northern zone and the eastern Weddell area there are few whales and 

 little or no "krill". These are also the two areas which apparently contain a particularly 

 homogeneous plankton population, a fact which should presumably be attributed to the 

 undisturbed flow of the ocean currents. In contrast to this an extremely variable plank- 

 ton was found to the east of the South Sandwich Islands, and here the ' ' krill "was abun- 

 dant and Fin whales were very numerous. The complex plankton distribution suggests 

 complex or disturbed hydrological conditions, which might be of the kind postulated 

 by Ruud as favourable to the concentration of ' ' krill ". Around the South Orkney Islands 

 also, and between the South Orkneys and the South Shetlands, the plankton, as we 

 have seen, tends to be variable and patchy, and here again large numbers of whales are 

 often seen. This apparent connection between a variable plankton and the occurrence 

 of whales does not always hold good, however, for in the Bellingshausen Sea, between 

 Sts. 565 and 566, and 577 and 578 (see Fig. 14) large numbers of whales were seen by 

 the ' Discovery II ', yet the plankton here could hardly be described as very variable 

 and patchy (see Table XII). 



There is reason also to believe that in certain circumstances some connection exists 

 between the distribution of whales and the distribution of the total quantity of macro- 

 plankton. The evidence for this is inconclusive, but is worth mention. It has been shown 

 by Kemp and Bennett (1932, p. 178) that during the first half of the whaling season at 

 South Georgia, the whales are mostly to be found on the north-east side of the island, but 

 that in the later part of the season there is a tendency towards a greater concentration on 

 the south-west side. This tendency was noticeable in all four seasons of the period 1 927-3 1 . 

 We have already seen that there is evidence to suggest a similar shift of the more abundant 

 plankton from the north or north-east to the south or south-west side of South Georgia, 

 and it seems possible that this shift of both whales and plankton may be due to some 

 common cause. In particular the concentration of both whales and macroplankton on the 

 south side of the island in February-March 1927-8, is very striking (compare Fig. 24 with 

 Kemp and Bennett, pis. xi and xix). A further indication that concentrations of whales 

 are connected with concentrations of macroplankton is to be found in the cruises to the 

 Bellingshausen Sea by the 'William Scores by' in 1929-30 and by the 'Discovery II' 

 in 1930-1. The 'William Scoresby' took some plankton samples early in January in 

 the eastern part of the Bellingshausen Sea (WS 496-501). Here the plankton was 



