5° 



DISCOVERY REPORTS 



on the north-east side of the island as shown in Fig. 19. Over ten million were taken at 

 St. 124. In actual numbers it is third in importance in the survey. The first place is 

 taken by Chaetoceros socialis, of which it was estimated that some 1 500 million cells were 

 taken in our samples, and the second place by Nitzschia seriata with a total of 211 

 million. Chaetoceros socialis and Nitzschia seriata are very small diatoms, the former 

 occurring in dense swarms; and they were not so widely distributed as Corethron 

 valdiviae. The total estimated number of C. valdiviae taken was nearly 24 million. 



D < 10,000 



□ 10,000-50,000 



Q 50,000-100,000 



. ^"%,' N 



-B- 



G 



si 



CD 



35* 



Fig. 18. Distribution of Thalassiosira antarctica round South Georgia in the December-January 1926-7 



survey. For full explanation see legend of Fig. 16. 



Its abundance on the November C line cannot be judged from the N 70 V nets (the 

 N 50 V nets not being used), since all but a few usually pass through their meshes. 

 However, it may be mentioned that at St. 20 in this line 22,800 were recorded in the 

 N 70 V nets (100-0), which is the second highest figure for Corethron occurring in the 

 analyses of these nets. At Sts. 131 and 132, where the N 50 V nets gave 3,216,000 and 

 1,003,500 respectively, the N 70 V nets gave only 740 and 450. It would appear that 

 this diatom was at any rate fairly abundant in November; but this is all we can say, 

 since no true relation can be established between the N 70 V nets and the N 50 V nets 

 in regard to this diatom on account of its usual passage through the meshes. It may well 



