398 DISCOVERY REPORTS 



(2) Apart from measurements we have no observations on the developmental condition of the 

 females in the young summer East Wind swarms except that none were recorded carrying spermato- 

 phores. It seems clear, however, judging from the condition of the females in the northern swarms, 

 that in the East Wind drift the majority of them must remain dominantly in stage i and the remainder 

 in stages i and 2, both equally dominant, throughout the season. In the adult swarms they are 

 dominantly in stages 5, 6 and 7 in January, stage 7 (the only observation) in February and stages 7 

 and 8 in March, our failure to record stage 8 in any measure of dominance until the last month of the 

 season providing perhaps some further evidence of the lateness of the spawning (p. 177) that has been 

 shown to take place in these high latitudes. 



(3) In both young and old swarms the pattern of modal values displayed is even more heterogeneous 

 than it is in the northern zone, a phenomenon that may be directly associated with the highly variable 

 ice conditions (and the acceleration or deceleration of phytoplankton production that goes with them) 

 in which so many of them spend their summer existence. 



(4) In January the more backward of the yearling swarms fall mainly within a length range of 

 12-34 mm., themajorityof them in fact representing whale food predominantly of the small 1 1-20 mm. 

 class. The more forward young January swarms fall mainly within the 21-36 mm. range. Throughout 

 February and March the more backward yearling swarms fall principally within a length range of 

 17-28 mm., the more forward within a length range of 25-40 mm., the former, even by the end of 

 March, still having not quite outgrown their early adolescent (11-20 mm.) phase. The occurrence 

 as late as 17 March of the very backward swarm (Station 2004) in which the vast majority of the indivi- 

 duals were early (11-20 mm.) adolescents is possibly, however, exceptional. In general it will be seen 

 the overall backward summer condition of the young East Wind swarms as compared with the 

 condition of their northern contemporaries is most conspicuous. 



(5) Throughout the season the adult swarms fall dominantly within a length range of 36-56 mm., 

 the majority of them, however, in the 40-52 mm. range. It would appear, therefore, that the breeding 

 swarms in the East Wind drift consist of individuals which on the whole are smaller than their con- 

 temporaries in the northern zone. 



Autumn. The distribution and relative abundance of the staple whale food in autumn (April-June) 

 is shown in Fig. 137. 



The adolescent and adult swarms that together provide the major sustenance of the whales, now 

 everywhere, except perhaps in the East Wind zone, appear to have undergone a phenomenal decline 

 from their summer magnitude and abundance. The decline in fact is so enormous that one hesitates 

 to believe it can be altogether real. Throughout the circumpolar sea it will be seen our autumn 

 coverage is meagre, more meagre by far than in summer. Indeed in so far as the Weddell current is 

 concerned the density of observation is even lower in autumn than the coverage figures suggest, for 

 they (p. 287) refer not only to the current itself, but also to the West Wind and East Wind zones to 

 the north and south of it. If, however, the observations in the main east-flowing Weddell stream, and 

 in the South Georgia and Bransfield Strait regions affected by it, alone be considered, the coverage 

 figures for the western, middle and eastern reaches of the drift in summer and autumn resolve them- 

 selves as follows: 



