THE OLDER STAGES 199 



to reveal. Their failure, however, can readily be explained, for, as Table 42 shows, it is simply due to the 

 fact that whereas in the rich northern zone the older Calyptopes and the Furcilia stages are found in the 

 surface from January onwards, reaching a maximum in March, in the East Wind drift, even as late as 

 March, the young surface population is not very large and still dominantly First Calyptopis, a stage that 

 (see above) is virtually unrepresented in the catches of the stramin nets except possibly when present in 

 exceptional abundance. The relative scarcity and backward development of the larvae in the East Wind 

 zone is again probably to be ascribed (p. 177) to the shortness of the summer there and the brief 

 blooming of the phytoplankton in these high latitudes. 



Table 42. Composition of the larval populations in the Weddell and East Wind zones in summer, 

 Weddell larvae in roman type, East IVitid larvae in italics 



Calyptopes 



Furcilias 



In a recent paper on some problems in larval ecology Wilson (1958) observes that spawning seasons 

 in general may be related and adapted 'to particular biological characteristics of a water normally 

 occurring at a certain time of year, just as we know that they often are related and adapted to tempera- 

 ture '. It could well be that it is temperature above all that is determining the geographical distribution 

 of the spawning krill, the virtually always sub-zero temperature of the coastal waters of the continental 

 land. 



Time of hatching 



From the occurrences of the Nauplii (p. 90, Tables 13 and 14) it is clear that hatching begins in 

 November and continues throughout summer until autumn, probably ending, as a major phenomenon, 

 in March. It seems likely, however, that it may continue sporadically and on a much reduced scale 

 until later, the several rich hauls of Metanauplii (Tables 13 and 14) recorded in late April in the 

 Weddell and East Wind zones suggesting that in both regions some hatching must take place in 

 the earlier part of that month. As with the spawning (p. 177) the hatching in the East Wind drift must 

 be late, not beginning on any appreciable scale (Table 14) until January. 



Depth and localities of hatching 



Although much of the evidence (again having particular regard to the rich haul of shelf-laid 

 eggs recorded at Station 540 and to the rich coastal haul of Nauplii recorded near the bottom at 

 Station 2603) seems to point to the spawning of this species being, in its major aspects at least, a 

 shallow water coastal phenomenon, taking place on a particularly large scale in the far western reaches 

 of the Weddell drift and in the coastal waters of higher latitudes, it is a remarkable fact that our data 

 provide very little evidence that hatching on any major scale takes place in the shallow conditions in 

 which it seems the eggs are laid. All our observations in fact point to the contrary, that it is deep down 

 in oceanic water, principally in the Weddell and East Wind zones, either close to the shelf regions on 

 the Antarctic continental slope or at some considerable distance away from them, that any such large- 



