EUPHAUSIACEA 



203 



in distribution, although, as far as our observations go, to nothing like the same degree. 

 This patchiness is described on p. 256 and illustrated in Fig. 131. Owing to its diurnal 

 migration it is impossible to compare the November and May lines with those of Decem- 

 ber and March, and so come to a conclusion regarding its seasonal fluctuations. 



We should not expect this species to be present in the warmer waters of the sub- 

 Antarctic Zone, and it was absent, except curiously enough for a single specimen taken 

 in an N 100 H net at a depth of 146 m. at St. WS 70 far across the line of Antarctic 

 Convergence. The temperature at this depth was 4-35° C. and the salinity 34-16 °/ 00 . 



A complete record of the occurrence of adult and larval forms is given in Appendix 

 II. The distribution of larval forms as revealed by the N 70 V nets is shown in Fig. 91. 

 No larvae were taken on the oceanic line approaching South Georgia from the north-east 

 in February 1926. In November only calyptopis and furcilia stages were taken, whereas 

 in May only one furcilia was taken all the rest being cyrtopia. Calyptopis stages were 

 never abundant. In the December- January survey larvae were almost equally abundant 

 on each side of the island. 



The proportions of the different stages taken at different seasons round South Georgia 

 may be summarized as follows : 



It should be remembered that the January samples were nearly all taken to the west 

 and south-west of the island (see Fig. 37) whereas those of all other seasons are confined 

 to the north-east and south-east side of the island. 



The distribution in depth of the adult and larval stages is given in the following tables, 

 in which the hauls are divided into day and night hauls. Here there is further evidence 

 of the vertical migration of the species, showing the centre of abundance for the adult 

 in the daytime to be between 250 and 500 m. and at night between 50 and 100 m. ; and 

 for larval forms between 100 and 250 m. in daytime and 50 and 100 m. at night. The 

 question of the reality of this vertical migration is more fully discussed in the special 

 section on p. 244. 



Tattersall (1924) in his report on the Euphausiacea collected by the British Antarctic 

 (Terra Nova) Expedition states that, except for the record by Zimmer (1914) of fourteen 

 specimens collected by the German South Polar (Gauss) Expedition in 58 29' S, all the 

 specimens up to then recorded were taken from within the isotherm 12 C. and outside 

 the limits of pack-ice. Recently Rustad (19306) and Ruud (1932) on the Norvegia and 

 Vikingen Expeditions obtained specimens between Bouvet Island and South Georgia, 

 the latter obtaining odd specimens at four stations between 6i° 23'and6i° 37' S. During 



