DISTRIBUTION OF ANTARCTIC MACROPLANKTON 85 



Where a pair of stations is shown in the above list the convergence lies between them. 

 Thus at WS 254 the cold layer lies at 100 m., while at WS 253 it lies at 750 m. : WS 253 

 is therefore in sub-Antarctic and WS 254 in Antarctic water. At WS 404 the cold layer 

 is at 150 m., while at WS 405 it has become obscured through sinking and mixing with 

 deeper water. This indicates that WS 405 is well on the north side of the convergence. 

 At such stations the cold layer can be detected only as an irregularity in a curve showing 

 the rate of decrease of temperature as the depth increases. WS 469 lies just about on the 

 convergence itself. At some stations no temperatures, or only surface temperatures, are 

 given. Thus WS 413, 466 and St. 390 probably lie very near the convergence. Sts. 630-3 

 lie near an eddy, which is roughly indicated by the bend of the convergence in Fig. 1. 

 From its surface temperature it is evident that St. 630 is in Antarctic water. Sts. 631 

 and 633 are probably very close to the convergence, and St. 632 in Antarctic water. 

 Sts. 391 and 395,* at which the N 100 B was not fished, are omitted from the list. 



A full account of the differences and resemblances which exist between the plankton 

 of the surface waters of the Antarctic and sub-Antarctic Zones would be a large subject 

 and will probably be dealt with in subsequent publications. I will give here only a brief 

 indication of the effect of the convergence as a faunistic barrier, and for this purpose 

 have examined the N 100 B analyses for twenty stations lying between 100 and 200 

 miles north of the convergence. The Copepoda have been identified in only eight of 

 these analyses, but they will serve for a purely qualitative comparison. 



Antarctic species occurring north of the convergence can be divided into the following : 



Normal inhabitants of sub-Antarctic water 



Calanus simillimus. Occurs at five out of eight stations, sometimes in moderate 

 numbers. 



Rhincalanus gigas. Occurs at seven out of eight stations, and is generally the most 

 numerous copepod. 



Pleuromamma robusta. Appears to occur at four out of eight stations, but its specific 

 identity at these sub-Antarctic stations has not been checked with absolute certainty. 



Eticalanus sp. Occurs at four out of eight stations, usually in small numbers. 



Parathemisto gaiidichandi. Occurs at seventeen out of twenty stations. Barnard (1932, 

 pp. 6-19) records this species in surface waters at various stations in comparatively low 

 latitudes. 



Primno macropa. Occurs at nine out of twenty stations, a high proportion for this 

 species. Occurrence in sub-Antarctic waters confirmed by Barnard. 



Vibilia antarctica. Occurs at four out of twenty stations — a sufficiently high pro- 

 portion. Recorded by Barnard in two sub-Antarctic surface hauls. It is evidently less 

 common than Primno in these latitudes. 



Etiphausia vallentini. Recorded in only eleven out of the twenty stations, but occurs 

 sometimes in large numbers and is actually a typical sub-Antarctic species which only 

 occasionally strays into the Antarctic. 



