DEVELOPMENT OF EUPHAUSIA SUPERB A 105 



the South Georgia plankton survey of November 1930. An account of the phyto- 

 planktonic conditions prevailing is given by Hart {loc. cit., pp. 41 et seq.). Concerning 

 Chaetoceros socialis he writes (p. 51): " Chaetoceros socialis .. .was taken at fourteen 

 stations only, all of which were grouped towards the southern extremity of the island, 

 some close inshore, and the others in the neighbourhood in which the pack-ice lingered 

 longest during this spring, and all in the water which from the general nature of the 

 phytoplankton as a whole, almost certainly originated in the western Weddell Sea." 

 Concerning Thallassiosira antarctica he writes: "It also reached its greatest abundance 

 in the western Weddell Sea surface water round the southern end of the island and was 

 comparatively rare to the north and north-west. It was, however, very widely distri- 



5- Z4 



STN5 



a3<x](oaDaDcz3czDcoco(Dcr)cncT^cj)cn 



Lr)tD(t3OTO(\jriUD 



'^^^^LOLOLnLDLnLnLnLnLnLnmLnLDLnLnLn 



ru en Ln 

 ru ru c\j 

 in in LD 



Fig. 28. Diagram showing the relationship between the average length of Euphausia siiperba, the abundance 

 of Thalassiosira antarctica and the occurrence of Chaetoceros socialis. 



buted, being taken at all but six stations on this survey. It occurred in the eastern 

 Weddell Sea water in considerable numbers. The minute form growing in gelatinous 

 colonies which defied estimation was, however, confined to the densely populated 

 region to the south-west with the single exception of the anomalous St. 493 on the 

 Larsen Line." In his summary too he states (p. 64) : " The richest and most varied flora 

 was found in the water, mainly of Weddell Sea origin, to the south and south-west of the 

 island. Here the dominant forms were Chaetoceros socialis, Thallassiosira antarctica and 

 Chaetoceros neglectiis." 



Fig. 28 shows that it was at the stations where Chaetoceros socialis and Thallassiosira 

 antarctica were most abundant that the young krill reached its greatest average length. 



D XIV - 14 



