HORIZONTAL DISTRIBUTION, GROWTH AND DYNAMICS OF DISPERSAL 381 



Fig. 136, Station 2004) it seems probable that under the autumn ice-sheet that now extends over so 

 much of the East Wind zone some whale food in the 1 1-20 mm. range must survive at least into 

 April. 



The gross distribution of the small whale food is shown by seasonal symbols in Fig. 126, the 

 symbols employed again representing gatherings of not less than 100 in the straminnets, catches of 

 less than that figure being distinguished by small black plots throughout the year. The principal facts 

 of the distribution thus presented are briefly as follows : 



(i) The conspicuous massing of the 11-20 mm. group that is found in the main east-flowing 

 Weddell stream, on the South Georgia whaling grounds and in the Bransfield Strait throughout 

 winter and spring. 



(2) Its virtual disappearance from the Weddell zone in summer and its continued survival then in 

 the East Wind drift. 



(3) Its absence, virtually complete, everywhere from the ice-free parts of the circumpolar sea in 

 autumn. 



(4) The minor degree of the easterly overflow that takes place from the Weddell drift in spring, an 

 overflow chiefly affecting the West Wind region between 30° and 60° E. 



(5) The extensive area, curiously barren of this class, that appears in Weddell West in spring, a 

 phenomenon probably attributable to the fact that by this time the majority of the young swarms 

 encountered there earlier in the year have been carried eastwards out of it in the surface stream. 



(6) The moderate to substantial local populations of this class that in winter and spring have been 

 recorded in the West Wind region south-east of Kerguelen and north-east of the Ross Sea, populations 

 that owe their existence to northerly outflows stemming from the East Wind drift. 



(7) The barrenness elsewhere of the West Wind zone, especially noticeable in the heavily sampled 

 Pacific sector. 



(8) The very large area covering the southern part of the Weddell drift from about 30° W to 

 30° E which appears conspicuously barren simply because the vast majority of the observations that 

 cover it were made, and can in fact only be made, at a time (that is, in summer and autumn) when the 

 early adolescent whale food, in this particular area at least, does not, or virtually does not, exist in the 

 plankton. The whole of this region from July to December would in fact be carrying a dense popula- 

 tion of the 11-20 mm. class which like the larvae (p. 373, Fig. 121) would be under the winter ice. 



A more realistic representation of the distribution and regional abundance of the small whale food 

 during the pelagic whaling season is obtained if, as in Fig. 127, the summer and autumn condi- 

 tions, using monthly symbols, are shown together on a single chart. This brings into sharp relief the 

 great scarcity of this class that is found in the Weddell zone throughout summer and autumn and the 

 relative abundance in which it persists from January, through February, until March in the East Wind 

 drift. 



Finally, before proceeding to deal with the third and last section of this series, the staple whale food, 

 this is perhaps the most appropriate juncture at which to present in a more connected, and it is hoped, 

 more realistic manner than has hitherto been possible, the major facts of the distribution and life- 

 history of the young first year swarms in the Weddell zone, the only region of euphausian abundance 

 that remains open to investigation throughout every month of the year. The facts it is true have already 

 been given, although up till now, owing to the nature of the distributional plan, in a somewhat 

 scattered and disconnected form. The chief object of this fresh approach to the problem, which is 

 based essentially on a more comprehensive grouping of the monthly data than has hitherto been 

 adopted, is to show at a glance how the surface life-cycle of the larvae in this northern zone begins 

 and ends in the Weddell drift, how the influence of this great current, as a purely larval carrier, seems 



