PHYTOPLANKTON 87 



environment to bring about the required change in the protoplasmic-environmental 

 relationship. It is possible of course that the mere fact of the colder water of the Weddell 

 Sea current meeting the warmer water of the Bellingshausen Sea current may bring 

 about an active propagation of the cells carried in the former, e.g. Chaetoceros socialis on 

 the western side. 



SEASONAL CHANGES IN THE PHYTOPLANKTON 



It is impossible to draw more than the most slender and general conclusions from the 

 data of the present survey. When the results of the surveys of subsequent years are 

 published there should be sufficient data to form a more adequate idea of the changes 

 taking place. In the present survey we can but compare the N 50 V net results taken 

 on the C line in December 1926, March 1926, and late May 1927. March 1926 we 

 have seen was remarkably poor in phytoplankton (p. 73); it gives an average total 

 of but 18,000 phytoplankton organisms for the three N 50 V nets taken. It may 

 have been an exceptional year, and since it belongs to a different season from that of 

 December 1926 and May 1927 it should not be compared with these two. A com- 

 parison between the N 50 V nets on the C line of December and May of the same season 

 gives an average total of phytoplankton organisms for December as 1,143,000 as com- 

 pared with 65,000 for May. This we can provisionally take as an indication of the change 

 taking place between early summer and late autumn. 



Again, since our autumnal data are based on only five stations in one locality it is 

 unwise to attempt to draw conclusions as to the succession of species throughout the 

 year. We can, however, say that our results confirm those of Mangin (1915), that 

 Coscinodiscus bouvet, Thalassiosira antarctica and Biddulphia seriata are characteristic of 

 the spring and early summer. 1 There are indications that Chaetoceros atlanticus is a late 

 summer and autumn species. 



Tables XLVIII and XLIX, showing the seasonal changes in temperature off the 

 north-east coast of South Georgia, are given in the section dealing with seasonal changes 

 in the zooplankton on pp. 265-267. 



ARCTIC AND ANTARCTIC PHYTOPLANKTON 



Karsten (1905) and Mangin (1915, 1922) have already discussed in detail the com- 

 parison of the Arctic and Antarctic phytoplankton. We may state here, however, that 

 the following northern forms were recorded in our catches ; those printed in heavy 

 type appear to be recorded in the Antarctic for the first time : 



Coscinodiscus centralis Asteromphalus hookeri Nitsschia seriata 



C. concinnus Rhizosolenia alata Peridtmum depression 



C. curvatulus Rh. obtusa Dinophysis ovum 



C. excentricus Rh. shrubsolei Ceratium gibberum 



C. lineatus Rh. styliformis C. tripos atlantica 



C. sub-bulliens? Chaetoceros dichaeta Halosphaera viridis 



C. subtilis Ch. atlanticus Distephanus speculum 



C. stellaris Ch. socialis 



Actinoptychus undulatus Ch. tortissimus 



1 These conclusions are further confirmed by Hart's (1934) results. 



