i8o 



DISCOVERY REPORTS 



(in press) may retain its importance up to mid-season. Later in the year it has not 

 been recorded in quantity, except at one station far to the south in the Bellingshausen 



Sea. 



Nitzschia seriata apparently finds its optimum later in the year than the other im- 

 portant species in the more northerly part of the area investigated. Though abundant 

 round South Georgia in spring, it was even more so at mid-season on the survey de- 

 scribed by Hardy. There is probably some falling off in February, but we have good 



Fig. 79. The probable distribution of the dominant species over the area studied in autumn. 



evidence that this is one of the dominant forms in the Scotia Sea during March and 



April. 



As far as the evidence collected for this paper goes, Biddidphia striata would appear 

 to be essentially a spring form, its abundant occurrence at a few stations far to the south 

 later in the year being explained by the lateness of the main increase in those latitudes. 

 A single instance during an earlier commission, of a rich haul with this species dominant 

 as late as April in the Bransfield Strait, points to the probability of its belonging to the 

 group of species with both spring and autumn maxima. 



Apart from these three, all the other important species fall readily into the grouping 



