lojj DISCOVERY REPORTS 



First Nauplii, 1296 of them being so far advanced as to appear almost on the point of hatching. 

 Many of the most advanced had lost their shells, large numbers of which were found in the catch, 

 and while the loss may have occurred through jostling in the net or immersion in the formalin fixative, 

 the fact that it did occur suggests how very close to hatching, if not actually on the point of hatching, 

 these ripe eggs must have been. Ripe however though they were, it is considered unlikely that 

 hatching in oceanic water would normally take place at this comparatively shallow level. The high 

 incidence of negative observation in the 1 500-1000 m. layer, and our complete and highly significant 

 failure to strike the First Nauplius there, points it would seem to its being a much deeper phenomenon. 

 Accordingly, I would suggest, the presence of these ripe eggs so near to the surface is perhaps to be 

 ascribed to the unusually powerful, and probably purely local, upwelling of the cold deep water that 

 evidently must have occurred in this particular region, an upwelling that also brought with it the 

 Second Nauplius (see Table 13) to a considerably higher level than usual. The large catch of Second 

 NaupUi in the 1000-750 m. layer at Station 823 (Table 13) could also it seems be ascribed to local 

 upwelling, influenced possibly in this instance by the proximity of the submarine ridge of the Scotia 

 Arc which, with minimum soundings of just over 200 fathoms, lay less than 40 miles away to the 

 north-west. 



It would appear then from the data presented in Table 17 that the deep movement of eggs and 

 larvae towards the east probably has its origin in the western part of the Weddell drift, in the sector 

 I have called Weddell West (see again Fig. 4), in December, although considerations based on 

 the occurrence of eggs and Second Nauplii in the Bransfield Strait in November (p. 290) suggest it may 

 even be earUer. By February, probably, it has spread to the sector I have called Weddell Middle, and 

 by March possibly to the far eastern sector, Weddell East.^ It is probable that by the end of March 

 no eggs or Nauplii are left in the deep east-going current, the occurrence in April of deep Meta- 

 nauplii only suggesting that by that time the Nauplii have completed their natural span or at any 

 rate have already deserted the cold deep stratum below. There can be no absolute certainty of this, 

 however, because although nets have been fished in April below 1000 m., all of them with negative 

 results, there were none, as Table 13 shows, worked below this level at any of the stations 

 where Metanauplii actually occurred. If there had been, it is possible, they might have revealed 

 the last surviving Second Nauplii rising from below. From April onwards, it seems evident from 

 the vertical distribution, eastward transport must for all practical purposes be confined to the 



surface drift. 



Eastward transport in the surface stream it seems has its beginnings in Weddell West in December 

 when the larvae first begin to reach the surface in small numbers. It is in full swing there in Januarj^^ 

 and by February has already progressed as far as Weddell Middle. It is not, however, until April 

 that its eifect is seen on any appreciable scale in the far eastern sector, Weddell East. 



A natural outcome of the repeated populating of the surface stream by very young larvae from below 

 is that in regions such as the Weddell drift, where spawning (p. 177) is spread over a long period, there 

 will always, as might be expected, while spawning and hatching continue, be two broadly distinguish- 

 able larval stocks in the sea, an older that has already reached the surface and a younger rising from 

 below. This phenomenon is illustrated in Table 18 in which the figures in roman type show the total 

 larval catch at all stations where deep rising larvae occurred and the figures in italics the corresponding 

 catch at stations where the deep risers were absent. Although manifestly characteristic of the Weddell 

 drift the dual age of the larval stock does not, our observations seem to show, have its counterpart 



1 See, however, p. 208. 



« Table 17 does not show this. The Norwegian ' Vikingen' expedition, however (Ruud, 1932, p. 35, Table 10), recorded 

 enormous numbers of First Calyptopes on the surface in Weddell West in January. 



