438 DISCOVERY REPORTS 



waters of the high latitudes of the continental land, the discovery there of concentrations of eggs and 

 Nauplii very close to the sea bed suggesting the distinct possibility that in these conditions the eggs 

 are laid on, or sink until they rest on, the bottom itself. A major spawning, lasting from November to 

 March, seems to be associated with the far western (and probably south-western) reaches of the 

 Weddell drift, and another, lasting from late January to March, with the slope waters of continental 

 Antarctica extending from the mouth of the Ross Sea westwards to the Princess Martha Coast, which 

 is as far as our observations go. We have many samples up to very high latitudes on the Pacific side, 

 although relatively few come from the East Wind zone, especially between 90° and 150° W where the 

 ice-cover is so heavy. Such as we have, however, from the high latitude west-going stream, between 

 80° and 160° W, show little sign of any spawning there. There are many indications too that, although 

 both gravid and spent females are commonly encountered on the South Georgia whaling grounds, 

 there is, paradoxically, virtually no spawning and certainly no successful hatching there. Hatching, 

 in so far as it appears to be a successful event, is essentially a phenomenon of the open sea, taking 

 place in the Weddell zone at great depths, in most instances far away from the continental land. In 

 the East Wind zone there is clear evidence that it takes place on or near the bottom on the continental 

 slope and at greater depths beyond, but notjvery far beyond, the 1000 fathom line. In general hatching 

 in the East Wind zone is much more closely associated with the land than it is in the northern zone. 

 There is no evidence in either the northern or southern zone of large-scale hatching on the shelf itself, 

 nor is there any that the gravid females go to the great depths at which hatching principally takes place 

 in order to lay their eggs, the vertical distribution of the spermatophore-carrying males and females 

 and of the spent and gravid females suggesting that both pairing and spawning are essentially surface 

 phenomena. There is evidence that the eggs themselves, although liberated near the surface, may sink 

 to deep levels, but it is not satisfactory enough to be conclusive. In view of these contradictory 

 phenomena — major spawning in or near coastal waters but hatching in the deep ocean, eggs manifestly 

 concentrated at great depths but gravid females to all appearances at the surface — it is suggested that 

 sinking Weddell shelf water, flowing away to the north and east as the Antarctic bottom current, out 

 of which it seems (9) the new-born krill below the Weddell stream are rising, is perhaps responsible in 

 part at least for carrying the coast eggs away to hatch at much deeper levels farther out to sea. There 

 is an obvious need, however, for systematic exploration of this cold deep stratum, so far scarcely 

 touched even by our deepest vertical nets, and for accurate measurements of its speed, before any 

 reliable picture of the full extent of its influence can be formed. There is much need, too, using large 

 nets, for systematic exploration of the great depths, down to say 3000 m. or more, at which it seems 

 the oceanic eggs are hatched. These are levels far below the deepest observations we have yet made, 

 and it may be that it is there that the gravid females are massed when about to lay their eggs. If, 

 however, they do go to such enormous depths, a journey it seems well within the powers of this large 

 and vigorous species, and one that could happen quite quickly, it is surprising that of the hundreds of 

 observations made below 100 m. during the spawning season not one, with the exception of a single 

 instance on the South Georgia whaling grounds, reveals the slightest evidence of a concentration of 

 them on their way from the surface down. The only alternative explanation of our failure to find 

 evidence of deep oceanic spawning might be that it is undertaken not by massed formations of females, 

 but by single individuals, so widely scattered as virtually to defy capture even by our largest nets, and 

 even this seems wholly inconsistent with the swarming habit (24) to which this species, from hatching 

 right through to the gravid state, seems lifelong prone (p. 176). 



23. Although no current measurements have yet been made in the bottom water, historical 

 evidence suggests that in high latitudes below the Weddell Sea, where it seems likely to be carrying 

 hatching eggs, it may be moving fairly quickly (p. 212) 



