376 DISCOVERY REPORTS 



Except where it is affected locally by East Wind influence, namely, south-east of Kerguelen, north- 

 east of the Ross Sea and again possibly in the southern part of the Drake Passage, the West Wind drift 

 is to all appearances barren of whale food in the 1 1-20 mm. range. 



In the East Wind drift, although the position is obscure, it seems probable (pp. 355-6) that the young 

 swarms survive the winter in a purely larval state and that the early adolescents in the 1 1-20 mm. 

 range, already well established in the Weddell zone, do not appear until later. 



Turning again to Fig. 116 (p. 367) in which the developmental condition and length frequencies 

 of the young winter swarms are shown, it will be seen that as might be expected they develop an 

 increasingly dominant 1 1-20 mm. component as the season advances, a component rather infrequently 

 dominant in July, more frequently dominant in August and exclusively dominant in September. 



Spring. The distribution and relative abundance of the 1 1-20 mm. class in spring is shown in 

 Fig. 123. By October the young swarms, everywhere throughout the ice-free zone, develop 

 length frequencies which for all practical purposes (p. 370, Fig. 118) fall exclusively within the 

 1 1-20 mm. range, and spring in consequence becomes the season when this group of very small 

 (larval and early adolescent) whale food is at the peak of its abundance. It is the season too par 

 excellence of the early adolescent when the last surviving larval stage, the Sixth Furcilia, becoming 

 scarcer and scarcer, finally disappears from the plankton. ^ Vast numbers of the 11-20 mm. class are 

 now found on the South Georgia whaling grounds, in Weddell Middle and Weddell East. There is 

 again, however (see p. 369, Fig. 117), a conspicuous scarcity of these young swarms in Weddell 

 West, a scarcity that as already suggested could be attributed to the fact that the still younger swarms, 

 so abundant in this region earlier in the year, have already drifted out of it by spring, moving eastwards 

 in the surface stream. The two minor concentrations of the 1 1-20 mm. class recorded in Weddell West 

 (Fig. 118, Stations 1866 and 1868) together with the minor to moderate concentrations recorded in 

 the Bransfield Strait could, therefore, it seems (p. 368), be of East Wind rather than of local origin. 



In the West Wind drift there is more evidence of the easterly overflow of the young swarms that 

 (p. 368) evidently takes place from the richly populated Weddell drift in November, the three minor 

 adolescent concentrations plotted between 30° and 65° E representing the 11-20 mm. components 

 of three mixed larval and adolescent swarms that it seems must have drifted away from the region of 

 rich larval and post-larval abundance west of 30° E. Elsewhere in the West Wind drift the influence 

 of surface deflection from the East Wind zone is to be seen in the moderate to substantial population 

 of early adolescents that has been recorded (in November and December) in the region south-east 

 of Kerguelen, while farther east, between 180° and 150° W, there is another, although much less 

 substantial, population of these young stages that has evidently been carried north-eastwards out of 

 the Ross Sea. Several very small occurrences appear too, west of Graham Land, in the region affected 

 by the north-going East Wind flow that occurs near Peter I Island. For the rest the barrenness of the 

 heavily sampled eastern half of the Pacific sector is again noteworthy. 



In the East Wind drift, judging from the position there in January (p. 355, Fig. 107), it seems 

 likely that the small whale food is now beginning to get well established and that towards the end of 

 spring it might be present as a substantial or even dominant component in the young mixed larval 

 and adolescent swarms in these high latitudes. 



Turning again to p. 370, Fig. 118, it will be seen that the principal features of the develop- 

 mental condition of the young spring swarms, in so far at least as their 11-20 mm. components are 

 concerned, may be summarised as follows: 



(i) Throughout October, whether they be of purely larval, mixed larval and adolescent, or purely 

 adolescent stock, they fall fairly, and for all practical purposes exclusively, within the 1 1-20 mm. class. 



1 That is, from the plankton of the ice-free northern zone, not however (p. 371), from the plankton of the East Wind drift. 



