2^4 DISCOVERY REPORTS 



(2) The absence of any major overflow of this teeming population, as larvae, into the West Wind 

 region east of 30° E. 



(3) The existence, at all times of the year, of discrete pockets of larval abundance in the otherw^ise 

 virtually barren West Wind drift that springs from the intrusion of cold surface tongues carrying 

 larvae from the East Wind zone. 



(4) The barrenness, almost absolute, of the heavily sampled West Wind zone of the Pacific 

 sector and of such northerly parts of the East Wind drift as have also been sampled there. 



(5) The high latitude region of larval abundance in the East Wind drift detectable, owing to the 

 ice conditions there, only in summer and autumn. 



(6) The vast area of the principal region of larval abundance in the East Wind-Weddell surface 

 stream which in the depth of winter is completely encompassed by the polar pack. 



The small whale food 



In the construction of the winter and spring charts illustrating the distribution of the 1 1-20 mm. 

 class, the larger Sixth Furcilias which (p. 365) contribute heavily to the small whale food population 

 in September, October and November, and upon which the whales (p. 138) undoubtedly sometimes 

 feed, have not been included. The charts in consequence deal exclusively with krill, of the 11-20 mm. 

 class, that have definitely been recognised as adolescent. The inclusion of the Sixth Furcilia would 

 have involved overlap and confusion in the presentation of the distributional data, the obscuring 

 (see below) of some important aspects of the distribution itself and in any case, our catch-figures 

 show, have resulted in no more than a stepping-up here and there of some of the lower orders of 

 abundance of the 11-20 mm. class without, however, materially affecting the major facts of its 

 distribution gathered from the adolescent material alone. 



Winter. The obvious starting-off point for plotting the distribution of the small whale food is 

 winter, for it is winter which marks the beginning of the post-larval life when the Sixth Furcilias 

 surviving from the previous summer's hatchings first begin to moult and become increasingly ado- 

 lescent. Its distribution and relative abundance during this period is shown in Fig. 122. By now, 

 everywhere throughout the ice-free zone, the young winter swarms, consisting essentially of mixtures 

 of larvae and adolescents, and exhibiting considerable variation both in length frequency and range 

 (p. 367, Fig. 116), in most instances fall within an overall maximum range of 8-16 mm. All, or 

 practically all, in addition to their purely larval component, include krill of the 11-20 mm. class, both 

 larval and adolescent, and it is therefore not surprising that in its major aspects the winter distribution 

 of the latter should follow closely that of the younger, purely larval, developmental phase (p. 366, 

 Fig. 115) from which it stems. In fact the only essential point of difference between the winter 

 distribution of the massed larvae and that of the 1 1-20 mm. adolescents, to which the former are giving 

 rise, is that whereas the larvae are spread along the Weddell drift from west to east in more or less 

 uniformly enormous numbers, comparable concentrations of adolescents appear exclusively in the 

 western part of the drift with only moderate, diminishing to minor or insignificant, concentrations in 

 the east. Having regard to the winter distribution of the massed larvae, which are no less abundant in 

 the east than in the west, the relative scarcity of the early adolescent population recorded in Weddell 

 East shows that in their development the young winter swarms as a whole are more advanced in the 

 western than in the far eastern reaches of the drift, ^ a phenomenon that can doubtless be traced to 

 the backward condition of the larval and mixed larval and adolescent swarms we have repeatedly 

 recorded eastward of 0° (p. 339, Fig. 95 and p. 353, Fig. 105) from July onwards. 



1 A fact which would have been obscured if the heavy winter concentrations of large Sixth Furcilias in the 11-20 mm. 

 range had been used in the construction of Fig. 122. 



