ZOOPLANKTON 209 



evenly as possible in each of these sectors, and to note which species were present. There were never 



less than ten samples available in each sector. If some species were absent, then a few more samples 



would be examined. Hence, as will be seen in Table 2, the number of samples examined from each 



sector varies between ten and sixteen. The total amounts to 230 and the positions of the stations at 



which they were taken is shown in Fig. 1. The station numbers are given in Table 3, p. 217. 



Most of the samples used were taken during the southern summer (October-April) but in order to 



cover each sector satisfactorily it has been necessary to include twenty-eight winter stations. The 



sectors in which these occur and the relative numbers of winter and summer stations are shown in 



Table 2. 



Table 2. Proportion of winter to summer stations 



IDENTIFICATION OF SPECIES 

 During the years prior to the last war a large number of plankton samples were analysed by various 

 members of the staff. This has greatly facilitated the present work, since just over half the data used 

 here have come from samples in which the species were already identified. The methods (of fractioning, 

 etc.) used in these analyses have been described by Mackintosh (1934), but it is necessary to give here 

 some idea of the accuracy of identifications as they affect this present work. 



Where a large number of plankton samples have to be examined it is essential that a technique 

 should be developed that enables each to be dealt with comparatively rapidly. Descriptions and 

 reference specimens of the common Antarctic zooplankton were provided by specialists, and it was 

 found that with the aid of these in the first instance the worker very soon became familiar with the 

 general appearance and one or two diagnostic features of the larger and more characteristic forms, 

 which enabled them to be identified by the naked eye. 



Thus it will be seen that the analyses are based on a familiarity with the species that are commonly 

 found in the samples, and this obviously allows a slight risk of inaccurate identification where some of 

 the forms are concerned. I have therefore made a further check on the identifications of the species. 

 For this purpose specimens were taken from samples from each of the following four sectors of the 

 Antarctic circumpolar area, 0-20 E., 80-100 E., 180-160 W. and 100-80 W. These specimens 

 were then submitted to specialists for examination. As a result it was found that in all but two 

 instances, which are considered below, the selected specimens had been correctly identified. 



I would like to take this opportunity of thanking the specialists concerned for their assistance. 

 Captain A. K. Totton of the British Museum very kindly examined the Siphonophores and Mr N. 

 Tebble of the British Museum the Polychaets. I would particularly like to thank Dr J. P. Harding, 



