2i4 DISCOVERY REPORTS 



species which show the highest percentage occurrence are not necessarily the most abundant species 

 but rather those which are more evenly distributed. Species with a ' patchy ' distribution are liable 

 to be absent from several samples even though they may be present in the sea not far from where the 

 samples were taken. Again some species are confined either to the warmer or colder parts of the 

 Antarctic water, and if, as in some instances, the available samples tend to be grouped in one part of 

 the temperature range, a false impression is given of their occurrence in the sector as a whole. 



DECREES EAST DECREES WEST 



2.0 4p 60 8p IOCI20 140 160 180 160 140 120 100 SO 60 40 20 p 



N9 OF SAMPLES EXAMINED 



SIPHONOPHORA 



DIPHYES ANTARCTICA 

 DIMOPHYES ARCTICA 

 PYROSTEPHOS VANHOFFENI 



ANTHOMEDUSAE 



SIBOCITA BORCHCREVINKI 



POLYCHAETA 



VANADIS ANTARCTICA 

 TOMOPTERIS SPP. 



CHAETOGNATHA 



SACITTA CAZELLAE 

 S . PLANCTONIS 

 EUKROHNIA HAMATA 



ECHINODERMATA 



AURICULARIA ANTARCTICA 



MOLLUSCA 



CLECDORA SULCATA 

 LIMACINA HELICINA 

 LIMACINA BALEA 

 SPONCIOBRANCHEA AUSTRALIS 

 CLIONE ANTARCTICA 



TUNICATA 



SALPA FUSIFORMIS f.ASPERA 



Fig. 4. Occurrence of species of zooplankton in all longitudes around the Antarctic zone of the Southern Ocean, showing 

 the percentage frequency of occurrence in samples taken within every 20 of longitude. 



CONCLUSIONS 



The zooplankton can be taken first. To begin with it is not claimed that the species dealt with here 

 include every oceanic species of the macroplankton existing in the Antarctic surface water, and it 

 must be made clear that there has been no selection of those which happen to have a circumpolar 

 distribution. For this it is probably enough to point out that these species include all except two of 

 those definitely identified by Mackintosh (1937) and listed on his p. 372 in order of abundance and 



