PHYSICAL ENVIRONMENT 69 



approximately 160 miles wide between Stations 2344 and 2346 in 53° 35-5' S, 19° 29-3' E, a consider- 

 ably narrower belt than that encountered less than fortnight before along the meridian of Greenwich, 

 but not inconsistent with the assumption that it is somewhere about here, in about 20° E, that the 

 Weddell current is beginning to lose its momentum and is probably dying away. On 23 August of 

 the same year, with the pack now practically up to the position of Station 2344, Station 241 1 was made 

 on its northern edge in 56° 25' S, 19° 54-7' E, 11,177 larvae, predominantly Furcilia 6, being taken 

 along with a few adolescents. 



Other instances of both summer and autumnal ice-free abundance with corresponding abundance 

 at the ice-edge in winter could also be given. The above, however, are enough to show that it is simply 

 the advent of the polar winter and the resultant freezing over of the sea that leads to the apparent 

 concentration of the larvae at the ice-edge upon which John and Eraser remark. At the same time it is 

 easy to see how these authorities, both former colleagues, were left with this impression, for it was 

 not until after their work was pubUshed that these repeated Weddell observations, which have contri- 

 buted so much else to our understanding of the whale food distribution as a whole, were for the most 

 part made. 



It must be admitted that the existence of young or older stages of krill, in places remote from the 

 nearest ice at the time of sampling, is not in itself enough to demonstrate that their distribution is 

 entirely independent of that of the pack-ice. The figures for ' the open sea ' in Tables i and 2 represent 

 our average gatherings from many stations, some of them far, others not so very far, from the ice. 

 Many in fact are no more than 10-20 miles from it, although equally many are much farther away, 

 especially in the Weddell drift and round South Georgia where they are separated by some hundreds 

 of miles from the nearest pack. Now since the presence or absence of pack-ice in one region or another 

 is seasonal it could be argued that the krill at some early stage, notably for instance when as a First 

 Calyptopis (p. 97) it reaches the surface from deep water, is in fact in some way dependent on the 

 presence or proximity of sea ice, and that when the pack melts (or retreats) it can as it were fend for 

 itself when left behind 'in the open sea'. Then indeed its distribution would at least be affected by 

 the ice. It is fair too to add that in the Weddell drift a great belt of ice persists in a low latitude across 

 the Atlantic sector well into summer, being separated then by open water from a more southerly ice- 

 belt girdling the Antarctic continent. This northern ice appears to last through December, but breaks 

 up and melts away in early January so that by the end of the month it has vanished except in the more 

 westerly parts of the current near the South Sandwich and South Orkney Islands. Populations of 

 krill left behind in the Weddell stream would then be hundreds of miles from any existing pack-ice, 

 but it could be said that some of them at least had been brought there along with the ice drifting 

 eastwards from the northern part of the Weddell Sea, and that their distribution was not, therefore, 

 entirely independent of the pack. Obviously, however, the massive accumulation of young surface 

 forms, mainly Calyptopes and early Furcilias, that seems to fill the ice-free waters of the Weddell 

 stream in autumn (p. 363, Eigs. 112 and 113), cannot be said to have been 'left behind ' by the retreat 

 of the pack. On the contrary the great bulk of this teeming population could not yet it seems have 

 been ' overtaken ' by the advance of the pack, for we find it there, on the whole an obviously not long 

 born community, long after the northern ice has gone and long before the winter ice in this sector, 

 creeping up from the south, has begun to approach even remotely near the low latitudes in which the 

 Weddell stream is flowing. In fact the idea that the krill in its very early stages is in some way de- 

 pendent on the pack, and is perhaps left behind in open water when the ice retreats, can only be true 

 if it should prove that the advent of the larvae at the surface (see again p. 97) is exclusively or very 

 largely an ice-edge phenomenon, and not, as we so repeatedly find (p. 301, Eigs. 70 and 71), a by no 

 means uncommon occurrence in the open sea. It is distinctly possible of course, indeed I think likely, 



