3o6 DISCOVERY REPORTS 



females from fifty stations operated during the spawning season and covering the whole West Wind 

 region of the Scotia Sea, or more precisely that part of it lying between the northern boundary of the 

 Weddell drift and the Antarctic convergence, was twelve gravid and two spent, the average yield 

 per station of potential breeders, say euphausians over 30 mm. long, being only two. In view of 

 these virtually negative findings we must again it seems turn to the distribution and movements of 

 the bottom water for a more satisfactory explanation of the presence of these deep larvae so far 

 outside their normal locus of abundance in this sector. Between the South Orkney Islands and the 

 South Shetland Islands and on either side of the relatively shallow ridge of the Scotia Arc, Deacon 

 (1937, p. 108) has shown that some bottom water is formed by a convection current which reaches 

 from the surface to the bottom in winter. Some of this water (Deacon, 1937; Clowes, 1938) spreads 

 westward for a short distance into the Drake Passage and, assuming it to be carrying hatching eggs 

 and developing Nauplii, the former shed say somewhere in the slope waters associated with the Scotia 

 Ridge, this westerly movement might conceivably be held responsible for the presence of the Meta- 

 nauplii at Station 647, where, it is interesting to record (p. 90, Table 13), an isolated patch of bottom 

 water was in fact encountered at a depth of a little over 3000 m. 



The principal inferences to be drawn from the distribution of the deep larvae, a comprehensive 

 picture of which is given in Fig. 72, may be summarised then as follows : 



(i) Although the main mass of the Nauplii, represented exclusively by Second Nauplii, has only 

 been sampled on a few occasions, because in the vast majority of instances our nets, in the right places 

 and at the right time of year, did not go deep enough, from the distribution of the Metanauplii, of 

 which we have substantial gatherings, it is clear that hatching, in its major aspects, is a phenomenon 

 of the deep oceanic water of the Weddell drift (where it probably takes place in the bottom water) 

 and also of the slope or coastal waters of the continental land. In shallow shelf regions it only takes 

 place on a negligible scale and virtually never it seems happens on the South Georgia whaling grounds. 



(2) There is an early hatching deep down in the oceanic water of Weddell West in December and 

 although it appears so far only to have taken place on a very small scale much deeper observations 

 than we have at present will probably reveal it, then if not before, as a major event. 



(3) There is a later hatching associated with the slope, coastal or near-coastal waters of the East 

 Wind drift, which, beginning on a reduced scale in January, is in full swing by February. The East 

 Wind hatching, however, seems to be confined to the New Zealand, Australian, Indian Ocean and 

 Atlantic sectors. 



(4) The deep larvae spread eastwards in the bottom water below the Weddell drift and by early 

 March have reached a point about half-way along Weddell Middle. 



(5) There is again evidence (e.g. at Station 2346) that spawning must sometimes, if rarely, take 

 place in or over deep oceanic water far away from land or banks. 



(6) Hatching in general is restricted almost exclusively to deep water below the East Wind- Weddell 

 surface stream, but in rare instances it seems hatching eggs and developing Nauplii may be carried 

 through the movement of the bottom water some distance outside this system into the West Wind 

 region of the Scotia Sea. 



(7) In the Pacific sector there is no evidence of any hatching, but it can be seen from Figs. 70 and 71 

 that the pack-ice there mostly extends to the northern boundary of the East Wind zone so that all but 

 a few of our samples are in fact from the West Wind drift. If any large-scale hatching does occur in 1 

 this region, it must take place in the inaccessible waters beyond the 70th parallel, though even thisi 

 (p. 124) seems improbable. 



(8) Since the occurrences of the deep climbers must coincide approximately with those of the eggs] 

 from which they spring, in other words must betray the existence, or recent existence, at still deeper] 



