DISTRIBUTION OF ANTARCTIC MACROPLANKTON 139 



hours of 0600 and 1700, and the figures for species with a marked diurnal variation in 

 lower latitudes are given in italics where the sample was taken in daytime. Where these 

 species are absent from such samples a query indicates that they might conceivably 

 have been present. Queries are also inserted where a sample is swamped by a large 

 catch of Euphansia super ba. 



If the various stations in this table are compared it will be seen that at each of the 

 seven most southerly stations (WS 544-51) the total number of organisms lies round 

 about 6000-7000, while at the other stations the totals vary from 2000 to 24,000. 

 Euphausia frigida occurs at all of the former stations at which it can be expected to be 

 found, and at none of the latter. Parathemisto occurs at most of the northerly stations 

 and at none from WS 544 onwards. Euphausia superba appears only in small numbers 

 south of WS 555 and nowhere south of WS 547. Haloptilus ocellatus is taken only at 

 WS 555 and at stations farther south, and Pleuromamma does not occur south of WS 555. 

 The steadiness of the total numbers at WS 544-51 and the wide fluctuations at the more 

 northerly stations is reflected in the composition of the plankton population. At the 

 southerly stations each species is present in roughly similar numbers, while farther 

 north no two adjacent catches are alike. At WS 536 for instance Euphausia frigida and 

 certain copepods are all plentiful, while at WS 537 the same species, with the exception 

 of Metridia, are either absent or much reduced. At WS 559 there was an enormous catch 

 of Calanus acutus and Metridia was relatively abundant, while WS 539 differed from all 

 the other stations in producing large numbers of Thysanoessa, all other species being 

 scarce. Of all the samples from this line, from WS 561 to WS 555, the only two which 

 seem to contain a similar plankton are WS 561 and WS 557, and these are widely 

 separated from one another. In this line of stations, therefore, we can recognize two 

 distinct faunistic areas, the more southerly one characterized by a very uniform plankton, 

 and the more northerly one characterized, at least to the east of the South Sandwich 

 Islands, by a sharply fluctuating plankton. Each of the two areas also seems to contain 

 certain species which are absent from the other. 



A distinction between these two areas is also found in the phytoplankton. Hart 

 (1934) gives a chart (Fig. 47, p. 102) on which the total quantities of phytoplankton are 

 shown for most of the stations included in Table IX. There were no phytoplankton 

 samples for WS 544 and WS 546, but at the stations near the South Sandwich Islands 

 the catches were variable and sometimes very large, while at the more southerly stations 

 the catches were more uniform, and, on the average, considerably smaller. The change 

 takes place, as with the macroplankton, between WS 543 and WS 545. There is also a 

 qualitative change in the phytoplankton from the South Sandwich area to the southern 

 stations, but this is not quite complete at WS 545. 



No other samples are available from the eastern Weddell Sea, but Sts. 626-8 (Fig. 14) 

 were taken about a month later on the east side of the South Sandwich Islands. At St. 627 

 the sample was swamped with krill, but Sts. 626 and 628 revealed two quite different 

 types of plankton. Between South Georgia and the South Sandwich Islands we have 

 first the William Scoresby's stations off the ice-edge in October 1928-9 (WS 287-310, 



