321 



HORIZONTAL DISTRIBUTION, GROWTH AND DYNAMICS OF DISPERSAL 



large, possibly very large, numbers. The backward development of the swarms we have repeatedly 

 encountered there earlier in the season strongly supports such a view, for even in late April it will be 

 seen (Fig. 83) they have progressed little beyond the First Calyptopis stage. It is probable, in 

 fact, that in May and June the Calyptopes survive in these high latitudes in far greater abundance 

 than they do, for instance, in the far eastern reaches of the Weddell drift. 



SECTOR 60W 



LONGITUDE 

 DATE 

 STATION 

 FURCILIA 



54° 47° 44° 44° 41° 



2 21 20 4 17 



W529W200WI99 1331 WI97 



WEDDELL 

 WEST 



30 W 



WEDDELL 

 MIDDLE 



WO E 



WEDDELL 

 EAST 



30 E SECTOR 



23° 22° 14° OB° OI° OI° OI° 04° 19° 20' 

 23 26 27 28 14 15 16 30 27 26 

 1346 1350 1351 1352 2316 2318 2320 1353 2346 2344 



LONGITUDE 

 DATE 

 STATION 

 6 FURCILIA 

 5 



Fig. 82. Developmental condition of surface larvae in the Weddell drift in April. 



MONTH 



DATE 

 STATION 

 FURCILIA 5 

 5 

 4 

 3 

 2 

 I 



CALYPTOPIS 3 

 2 



DEEP LARVAE 



28 

 1662 



2 17 28 

 1671 NI9 1545 



3 4 8 10 22 26 

 26002603 26IO 1312 1713 1720 



Scol e per cent 

 o so too 



.ik„„iil 



20 20 22 

 854 855 2335 



13 19 424 227 1455 38 — 9 



MONTH 



DATE 

 STATION 

 6 FURCILIA 

 5 

 4 

 3 

 2 



I 



3 CALYPTOPIS 



2 



I 



DEEP LARVAE 



* LARVAE ABOUT TO REACH THE SURFACE 



Fig. 83. Developmental condition of surface larvae in the East Wind drift. 



The principal inferences to be drawn from the distribution of the surface Calyptopis population, 

 a general view of which is given in Fig. 84, are as follows : 



(i) Although there are a few scattered and on the whole insignificant occurrences in November and 

 December, the majority of them, including the larger, in Weddell West in December, the Calyptopes 

 do not reach the surface on a major scale in this locality until rather late in January. They gradually 

 spread to the eastward, reaching 30° W by the end of February. 



(2) About a month later they begin to appear in the surface waters of the East Wind drift, but it is 

 probably not until March that the completion of the developmental ascent becomes general there. 



(3) By March in the Weddell drift they have spread to a position about half-way along Weddell 

 Middle and by April cover the whole of the drift from west to east. 



(4) Their eastward spreading is due partly to the influence of the surface stream and partly to that 

 of the eastward movement of the deep larvae carried in the bottom water below. It is unlikely, how- 

 ever, that the influence of the bottom water as a larval carrier extends farther east than about 18° W. 



(5) The spreading may be accelerated or retarded largely owing to the complexity and vagaries of 

 the triple current system in which the larval population spends its early existence. 



(6) The occasional presence of Calyptopes on the South Georgia whaling grounds and in the 

 Bransfield Strait must be ascribed to the influence of the surface drift and not to any local large-scale 

 hatching that takes place in either region. 



37 



