128 



DISCOVERY REPORTS 



analyses of the phytoplankton material collected on this line are given in Table XLI, 

 together with the analysis of the haul from St. 555, worked slightly to the westward of 

 the middle of the line a week later. 



It will be seen that on this line the phytoplankton was poor, and that Corethron 

 valdiviae was dominant throughout. The haul at St. 549 at the northern end close in to 

 Snow Island was somewhat richer and more varied than the others, but even here none 

 of the species other than Corethron reached any high degree of importance. One would 

 have expected a more varied phytoplankton at this station owing to its proximity to the 

 deepest western inlet into the Bransfield Strait — that between Snow and Smith Islands. 

 It was very evident throughout this survey that the influx of Bellingshausen Sea surface 

 water was at a minimum and that the spring maximum within the body of the strait was 

 over. The hauls from the more southerly stations on this line fully bear out this view. 

 One hint of a possible renewal of the invasion from the Bellingshausen Sea was afforded 

 by a richer haul, with Corethron dominant, at the very last station of the survey, St. 555, 

 mentioned above. 



The additional isolated stations worked off the western end of the strait somewhat 

 later in the year have been included on the distribution charts for the sake of con- 

 venience. Their consideration is better left until conditions on the survey proper have 

 been summarized. 



The following is a list of all the species recorded on the whole of the survey, with 

 their total abundance and the number of stations at which each occurred. The letter W 

 after the figures indicates that the numbers of the species were mainly due to a strong 

 maximum at the three stations, Sts. 541, 546 and 547, worked in surface water of 

 Weddell Sea origin : 



Corethron valdiviae (17) 

 Chaetoceros neglectus (9) 

 Ch. socialis (3) 

 Thalassiosim antarctica (14) 

 Chaetoceros tortissimm (3) 

 Fragihnia antarctica (9) 

 Biddulphia striata (9) 

 Eucampia antarctica (6) 

 Rhizosolenia alata f. gracillima (12) 

 R. alata (3) 

 R. truncata (6) 

 Nitzschia seriata (6) 

 Chaetoceros flexuosns (3) 



59,510,200 

 (co+) 4,329,100 W 



00 W 



3,882,600 w 



3,873,000 w 



2,095,500 w 



1,184,400 w 



1,050,800 w 



461,850 



360,600 w 



338,540 w 



300,000 w 



246,000 w 



207,000 w 



Chaetoceros criophihim (5) 219,000 



Cosciiiodiscus spp. (5) 130,700 



Thalassiothrix antarctica (5) 53,200 



Rhizosolenia stylijormis (5) 50,500 



Silicoflagellata (2) 50,400 



Coscinodisciis bouvet (2) 27,600 



Synedra spathulata (2) 21,600 



Peridinium spp. (2) 12,800 



Navicula peUucida {i) 12,000 



Navicula spp. (4) 2,800 



Lycmopliora sp. (2) 2,100 



Thalassiothrix sp . ( i ) i ,200 



Ch. dichaeta (2) 



Estimated total phytoplankton 78,723,790. 



The total estimated phytoplankton taken on this survey (17 stations) of course 

 excludes the minute uncountable Chaetocerids. The proportion of "other species" 

 was 31-6 per cent of the total, Corethron valdiviae forming 68-4 per cent. The pro- 

 portion of other species was thus much greater than that found during the spring or 

 autumn surveys, but, as we have seen, this was almost entirely due to the three hauls 

 obtained in Weddell Sea surface water. It will be evident that, if we consider only 



