i 5 8 DISCOVERY REPORTS 



a high proportion of cold-water species in spring and a low proportion in autumn, and 

 there is little doubt that the warm-water species remain dominant during the winter in 

 spite of the lower temperature of the water. The distribution of the cold-water species 

 appears to have some connection with the movements of the pack-ice, but in the lower 

 latitudes, which are not reached by the pack, the same reduction takes place as the 

 season advances. In a cold summer there is a higher proportion of cold-water species 

 which, however, become reduced in the same way. The material, so far as it goes, 

 suggests further that an exceptionally cold summer season in the Atlantic sector of the 

 Antarctic may not necessarily be accompanied by a correspondingly cold season on the 

 west side of the Drake Passage. 



Different plankton communities can be distinguished in different water masses. 

 Fig. 48 shows roughly the different areas in which a characteristic plankton population 

 was found. These areas coincide to a large extent with different water masses. In the 

 outer or northern zone of the Antarctic there is a uniform plankton population which 

 undergoes little change in composition during the year. In other places, such as to the 

 east of the South Sandwich Islands and in parts of the Orkney-Shetland region the 

 plankton may fluctuate sharply from place to place and from time to time. It appears 

 that where the hydrological conditions are uniform and undisturbed there is a uniform 

 and stable plankton, and where the hydrological conditions are complex and variable 

 there is a variable and unstable plankton population. 



In the last section the connection between the macroplankton and the distribution of 

 whales is discussed. It seems that whales are found in regions characterized by a 

 variable plankton rather than in those with a uniform and stable plankton, and there is 

 evidence which suggests that in certain circumstances the distribution of whales may 

 be correlated with the distribution of the quantity of plankton. 



LIST OF LITERATURE 



Barnard, K. H., 1932. Amphipoda. Discovery Reports, v, pp. 1-326, text-figs. 1-174, pi. i. 

 Benham, W. B., 1921. Polychaeta. Australian Antarctic Exped., ser. C, vi (3), pp. 1-128, pis. 5-10. 

 Bigelow, H. B., and Leslie, M., 1930. Reconnaissance of the Waters and Plankton of Monterey Bay, July, 



1928. Bull. Mus. Comp. Zool., lxx, 5, pp. 427-581, text-figs. 1-43. 

 Bonnevie, K.R., 1913. Pteropoda. Rep. Sci. Results 'Michael Sars' North Atlantic Deep-Sea Exped., II, 



Pt. 1, Zoology, pp. 1-15, text-figs. A and B, pis. i-v. 

 Browne, E. T., 1910. Coelenterata. V. Medusae. National Antarctic Exped., v, pp. 1-62, pis. i-vii. 

 Chun, C, 1897. Die Siphonophoren der Plankton-Expedition. Erg. d. Plankton-Expedition der Humboldt- 



Stiftung, 11, K.b, pp. 1-126, text-figs. 1-2, pis. i-viii. 

 Deacon, G. E. R., 1933. A General Account of the Hydrology of the South Atlantic Ocean. Discovery 



Reports, VII, pp. 171-238, text-figs. 1-24, pis. viii-x. 

 Eliot, C, 1907. Mollusca. VI. Pteropoda. National Antarctic Exped., in, pp. 1-15, pis. i-ii. 

 Hansen, H. J., 1913. Crustacea Schizopoda. Swedish Antarctic Exped. 1901-3, pp. 1-44, pis. i-vi. 

 Hardy, A. C, and Gunther, E. R., 1934. The Plankton of the South Georgia Whaling Grounds and 



Adjacent Waters, 1926-7. Discovery Reports (in press). 



