68 



DISCOVERY REPORTS 



samples obtained by the N 50 V nets, which give us a good picture of the phytoplankton 

 present. 



The totals of the phytoplankton cells taken at each station are charted in Fig. 38, in 

 order to give an idea of the relative production in different parts of the area. It must, 

 however, be remembered that we are dealing with diatoms of very different sizes — from 

 the large Coscinodiscus bouvet to the small Chaetoceros socialis and Nitzschia seriata — and 

 this fact must be borne in mind when forming a picture of relative production. Corn- 



Fig. 35. Chart showing the stations in the South Georgia December-January 1926-7 survey distinguished 

 according to their different phytoplankton floras. For further explanation see text. 



parison of volumes of settled plankton are, however, also misleading, for the different 

 types of diatom pack and settle so very differently: those with long spines such 

 as Chaetoceros occupying much more space than compact rounded forms such as 

 Coscinodiscus. In a preliminary description of the work of the expedition published in 

 the Geographical Journal, the author (1928) gave a diagram illustrating the pro- 

 visional results of this survey by showing the distribution of the phytoplankton round 

 South Georgia as volumes ; these were volumes measured on board at the time of the 

 survey after the sample had been allowed to settle for some 24 hours. After these samples 

 had been allowed to stand in their tubes for a very much longer period, a year or so, the 



