HORIZONTAL DISTRIBUTION, GROWTH AND DYNAMICS OF DISPERSAL 323 



(7) The May-June chart, more than any other in the vertical series, emphasises the primary role of the 

 Weddell stream as the carrier and instrument of dispersal of these surface forms in the Atlantic sector. 

 Its influence, however, seems to cease somewhat abruptly in the neighbourhood of meridian 30° E. 



(8) The Calyptopes have probably all but outgrown themselves in Weddell West and Weddell 

 Middle by early May, but survive in considerable abundance in Weddell East into June. In the late- 

 spawning, slow-growing region of the East Wind drift, however, they must survive, it seems, in great 

 abundance into June, if not later. 



(9) The larvae seem to take about a month or more to accomplish the developmental ascent, and 

 from the relative positions and ages of the swarms in the surface stream it would appear that the 

 development from First to Third Calyptopis takes about the same time. 



(10) In its major aspects the distribution of these stages is essentially a feature of the East Wind- 

 Weddell surface stream, the West Wind drift being barren, or virtually barren, except where it is 

 affected by tongues of cold water emanating from the East Wind zone or by the penetration of bottom 

 water into the Scotia Sea. 



The shallow living First, Second and Third Furcilias 



Before proceeding to deal with the distribution of the early Furcilias it might be observed that in 

 the principal region of their abundance in the Weddell drift the distribution of the two groups of 

 larvae so far described has conformed in each instance to a distinct pattern and time schedule, a 

 westerly beginning in the early part of the season followed by a gradual spreading to the east as the 

 season advances. To this pattern and schedule both groups of Furcilias, as they successively appear 

 in the plankton, also conform, except that, as would be expected, their westerly beginnings happen 

 later and later in the season. 



Jfanuary-February. Furcilias 1-3 then first appear in the plankton of Weddell West and the South 

 Georgia whaling grounds in January. They are everywhere, however, very scarce, and as both 

 Figs. 77 and 85 show it is not until late February that they have been recorded in this region in any 

 measure of abundance. In this developmental phase they are now fast beginning to crowd the near 

 surface stratum both by day and by night^ and in consequence are becoming more and more involved 

 in the movement of the surface drift. Their presence in major concentration in longitude 30° W 

 (Stations 361 and 362 in Fig. 77) can therefore, I think, be ascribed to risings that took place 

 considerably farther west, such as that for instance, disregarding the date, recorded (Fig. 77) 

 at Station 1965 in 47° W. The absence of comparable concentrations west of 30° W at this time 

 (that is, in February) is perhaps a little surprising, but is possibly due to the chance failure 

 of our nets to strike them. In the South Georgia area, where our observations are particularly 

 numerous and closely spaced, there has evidently as yet been no large-scale incursion of early Furcilias 

 borne upon the surface drift. The few young Furcilias recorded there, the majority of them in 

 February, might therefore, it seems, represent the local growth of the scattered and, with one excep- 

 tion, meagre Calyptopis population recorded there in January. 



As far as the Weddell drift is concerned it is, of course, only to be expected that in the first months 

 of their appearance the early Furcilias should be found concentrated exclusively in the western part 

 of the current, for it is there too that the surface Calyptopes are also concentrated (p. 310, Fig. 74) 

 in the January-February period. The barren, or virtually barren, condition of the East Wind drift 

 is also to be expected, for although there is a solitary occurrence there of a single First Furcilia on the 

 northern outskirts of the Ross Sea (a late February record) it is obvious from Fig. 83 that the 

 early Furcilias cannot normally make their appearance in these high latitudes until long after April. 



1 See p. no, Fig. n in the section on diurnal migration. 



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