3 oo DISCOVERY REPORTS 



The probability that these correlations in six instances (including December-January 

 1926-7) between the distribution of the whales and that of the phosphate values are due 

 to chance must be small. That the distribution of two species of whale are so closely 

 similar shows that they are being influenced by the same factor. We know that the two 

 species feed exclusively upon the same species of Euphausia, and we have seen how 

 closely their distribution in March 1926 and December-January 1926-7 appeared to 

 be bound up with the distribution of this Euphausian. We have seen how very closely 

 the pattern of phosphate consumption agrees with the pattern of phytoplankton pro- 

 duction in the December-January survey, also in the results of Kreps and Verjbinskaya 

 (1930) and from Gran's (1931) treatment of Ruud's samples from the Weddell Sea, 

 referred to on p. 78. In addition we have seen how the phosphate values of other 

 surveys are inversely correlated with the/>H values. We have seen how the Euphausians 

 are distributed in December-January 1926-7, away from the densest production of 

 phytoplankton, as they are also in the figures of Mackintosh in the survey of 1928 given 

 above. 



The evidence would appear to point to the conclusion that the distribution of the 

 phytoplankton is inversely linked with that of the Euphausian E. saperba, and that the 

 distribution of this Euphausian closely governs that of the whales. The possibility that 

 the phosphate content of the water acts directly upon the Euphausians or the whales, or 

 both, will be discussed and dismissed in a later section (p. 332). It is, of course, possible 

 but hardly probable that the phytoplankton might act directly upon the whales them- 

 selves as well as on the Euphausians, and most probable that the whales will as a matter 

 of behaviour avoid the dense phytoplankton knowing that the Euphausians are not to 

 be found there. Plate xxiii in the report by Kemp and Bennett shows the distribution 

 of all the Blue and Fin whales taken around South Georgia in the seasons 1923-4 to 

 1 930-1, and we see that the distribution of the whales at the time of our survey in 

 December-January 1926-7 conformed to the general pattern of the fishery taken as a 

 whole over all these years. This is fortunate, for one may conclude that the planktonic 

 conditions during our detailed survey were fairly normal for the area. 



A FULLER EXAMINATION OF THE HYPOTHESIS OF 



ANIMAL EXCLUSION 



We have seen that in general the greater the phytoplankton production the greater is 

 the reduction in the phosphate content in the water, and we have seen that relative 

 reduction in phosphate content would appear to be a better index in studying the 

 interrelationship between phyto- and zooplankton than phytoplankton itself, not only 

 because measurements of phytoplankton either by numbers of cells or by volume are 

 so unsatisfactory, but because the relative reduction in phosphates at different stations 

 gives a measure of phytoplankton production over some little time in the past. The 

 phytoplankton crop will not always bear a relation to the contemporary phosphate 

 values; in our survey, at the inshore stations WS 41 and WS 42, there is evidence that 



