338 DISCOVERY REPORTS 



While then the relative abundance of the older Furcilias in this late phase of their development 

 cannot adequately be determined from the gatherings of the vertical nets, it is clear from their 

 distribution that throughout winter and spring, the Weddell drift, and the South Georgia whaling 

 grounds to which it spreads, are the principal carriers of these stages in the ice-free north. The 

 Bransfield Strait, it seems, might also be a carrier, and perhaps an equally important one, the oc- 

 currence of very small numbers there in November (Fig. 94) suggesting that throughout winter 

 at any rate the late Furcilia population in this locality might be fairly substantial. Except for the 

 occurrence of a single Sbcth Furcilia in September, again it is interesting to note in the region south- 

 east of Kerguelen affected by cold surface emanation from the East Wind drift, the July-December 

 vertical nets reveal an absence of late Furcilias throughout the West Wind zone. This, however, in 

 part at least, is only an appearance that springs from the low sampling power of the vertical net when 

 used for gathering these predominantly surface-living forms. Our larger stramin nets (p. 369, Fig. 117), 

 with their far greater sampling power, reveal, in spring at any rate, not absence but great scarcity. 



Although we can now do little more than guess at what is happening in the East Wind drift, it 

 seems probable that under the ice-sheet which now extends so far to the north of this high southern 

 region of larval abundance, the late Furcilias (p. 334) do not make their appearance on a major scale 

 until some time after June. In any case it must be assumed they develop slowly, attaining the adolescent 

 state considerably later than their contemporaries in the ice-free, better illuminated, conditions of the 

 northern zone. In fact judging from the overwintering of some of them, in the Sixth Furcilia stage, 

 until well into the following year (p. 371), and from the exceptionally small size of the individuals 

 comprising many of the adolescent or mixed larval and adolescent swarms encountered in these high 

 latitudes from January to March (p. 355, Fig. 107), it is possible that in the East Wind zone the Sixth 

 Furcilia in many instances remains dominant, possibly up to the end of December. The only December 

 observation we have in these high latitudes (Fig. 107, Station RS9) does in fact show it so surviving. 



Finally, turning again to the Weddell drift, it may be noted that while the pronounced scarcity of 

 late Furcilias recorded in September (Fig. 93) must be attributable in some degree to the low 

 sampling power of the vertical net, the equally pronounced scarcity recorded in December (Fig. 94) 

 is only to be expected since it is then (p. 339) that the last Sixth FurciUas surviving in this surface 

 stream moult and become adolescent.^ 



The developmental condition of the larval, or mixed larval and adolescent, swarms encountered in 

 the ice-free Weddell zone from July to December is shown in Fig. 95. In this presentation of the 

 data the graphs portraying the percentage stage frequency are based in the vast majority of instances 

 on the analyses of the abundant material from the stramin nets, the vertical nets as a rule (p. 331) 

 providing only negligible samples. They are based principally on the larval and adolescent stage 

 frequency determinations of Eraser (1936, Appendix i) but include many similar determinations by 

 other members of the Discovery staff. 



By mid- July then, it will be seen, the Weddell drift from end to end is carrying larvae mainly in the 

 Fifth and Sixth Furcilia stage, the latter predominating, although the former may also occasionally 

 be encountered (Stations 2863, 2864) as the dominant, if only slightly dominant, stage. A few Fourth 

 Furcilias still survive and in several instances it will be seen the Sixth Furcilia has already moulted 

 and become adolescent although as yet, apart from one instance (Station 2854) only relatively small 

 numbers would appear to have progressed beyond the final larval stage. In the South Georgia area, had 

 we July observations to show it, a similar position would doubtless be disclosed. Throughout August 



^ It should be recalled, however, that the 'Terje Viken' whale stomach records (p. 138) point to the occasional, if perhaps 

 exceptional, survival of the Sixth Furcilia in Weddell East in some considerable measure of abundance until the second half 

 of December. 



