HORIZONTAL DISTRIBUTION, GROWTH AND DYNAMICS OF DISPERSAL 305 



Now it might well be supposed from such a disposition that the missing eggs at this station were in 

 fact lying hatching on the bottom itself and that the First Nauplii to which they were giving rise had, 

 as they began to climb, all moulted and become Second Nauplii before reaching the level traversed 

 by the deep 1400-1000 m. net. If this were so, and if it be assumed that the newly hatched Nauplius 

 immediately begins to climb, in view of the very short distance it would have had to travel in this 

 instance before reaching the 1400 m. level, there would seem to be good grounds for supposing, as 

 Fraser (p. 119) originally suggested, that the life span of the First Nauplius in the plankton is in fact 

 exceedingly short. On the other hand, if it did not rise immediately but lay for some time dormant 

 on the bottom, or again if the rate of climb were very slow, as it might well be for such a puny 

 creature, it would follow that its existence might not after all be so ephemeral as Fraser imagined. 



I can suggest three possible reasons for the presence of these very recently hatched larvae so close 

 to the bottom: (i) the eggs sank there from some higher level before hatching, (2) the females spawned 

 on or near the bottom, and (3) the eggs, although laid perhaps at some higher level, got carried to the 

 bottom by local sinking of the adjacent shelf water. 



The occurrence of the Second Nauplius at Station 2603 is the only record of this stage we have for 

 March-April and it is significant and perhaps to be expected that it should come from the East Wind 

 drift where the main spawning takes place so much later than elsewhere. Whether or not it survives 

 there into April is harder to say, since none of our East Wind April nets go deeper than 1000 m. 

 At two stations, however, off Enderby Land (p. 93, Table 14) substantial numbers of Metanauplii 

 were recorded on the 20th of the month and in view of the lateness of the date it (the Second 

 Nauplius) might well it seems survive in these high latitudes until at least over March. 



The one exceptional occurrence of deep larvae to which I have already alluded, exceptional in 

 the sense that it belongs neither to the East Wind nor to the Weddell stream, is of a relatively 

 enormous number of Metanauplii and deep First Calyptopes in the oceanic water of the Scotia Sea 

 at a point more than 100 miles north-north-west of the northern boundary of the Weddell drift. The 

 occurrence could in fact be described not only as exceptional but as highly anomalous, for the locality 

 in which it was recorded falls strictly speaking within the southern limits of the West Wind drift, 

 a region already shown throughout its vast circumpolar extent, to be barren of eggs or of recently 

 hatched larvae in the deeper layers. It was recorded on 12 March at Station 647 and is represented in 

 Fig. 71 by the large black and white plot to the north of Graham Land, a little eastward of 

 meridian 60° W. The deep larvae were disposed vertically as follows : 



Clearly somewhere far below the 1000 m. level in this locality, although not necessarily (p. 304) 

 directly below it, there must have existed, in all probability some time previously, a mass of hatching 

 eggs, resulting, it might be supposed, from another instance of large-scale oceanic spawning in either 

 the deep or surface layers far away from land. Probable, however, though it may seem, this explana- 

 tion of the anomaly is not altogether satisfactory, for not only have we failed consistently to find any 

 evidence of large-scale spawning in this locality either from our records of spent and gravid females 

 or from our records of eggs, but throughout these investigations have repeatedly found the area to be 

 barren, or virtually barren, of a potential breeding stock as well. In fact the net yield of breeding 



35 DM 



