HORIZONTAL DISTRIBUTION, GROWTH AND DYNAMICS OF DISPERSAL 367 



We measured the young krill to the nearest milUmetre from the anterior margin of the eye^ to the 

 tip of the telson, the vast bulk of the work being carried out daily at sea in the course of the routine 

 examination of the samples from the stramin nets. To eliminate the effect of (i) personal errors intro- 

 duced because the labour of measuring was shared by several (at least six) individuals, (2) errors 

 arising through the variable contraction or distortion of the specimens in the formalin fixative, and 

 (3) multiple errors arising through the very rapidity with which perforce so much of this enormous 

 task had to carried out, the length frequencies are presented in 2-mm. groups. The number of 

 specimens upon which each developmental graph (whether expressed as a length or stage frequency) 

 is based is shown at the bottom of each seasonal diagram, both of which, although based largely on 

 the field observations described above, include the highly accurate measurements (to the nearest 

 ^ mm.) and larval and adolescent determinations of Fraser (1936, Appendices i and 11). 



JULY 



AUGUST 



SEPTEMBER 



STATION 



ADOL 

 FURCILIA 



18 



16 

 14 

 12 

 10 

 B 

 5 



N? EXAM- 

 -INEO 



B 9 10 II II 12 12 13 13 15 16 16 [IB 19 21 22 22 24 2B282B 29 29 29 2 4 13 17 17 17 IB IB 19 19 25 25 29 30 

 2B5I 2853 2855 2B57 2859 2372 23942405240B W26I W264 W267 I403 W279W2B2 W285 W287 2431 2443 

 2852 2854 2856 2365 2863 2864 2398 2406 2412 W263 W266 W26B W276 W280W283 W2B6 W288 2432 2445 



■i*f%fi|ftkW™"if™f 



M 



Scale per cent 



M 



41 103 33 51 58 

 75 80 47 40 32 



no ISO 50 lOO 45 lOO 362 100 lOO lOO 100 62 192 

 56 100 lOO 186 100 52 59 59 50 lOO 100 lOO 405 90 



ADOL 

 6 FURCILIA 



16 

 14 

 12 

 10 



N2 EXAM - 

 - INED 



Fig. 1 1 6. Developmental condition of the massed surface larvae and small whale food in 



the 1 1-20 mm. range in winter. 



The distribution and relative abundance of the massed surface larvae in winter (July-September) 

 is shown in Fig. 115. They are now, as Fig. 116 shows, exclusively late Furcilias, predomin- 

 antly the Sixth, and becoming increasingly adolescent. As in autumn they continue to fill the 

 Weddell drift and the South Georgia whaling grounds, for the most part in enormous numbers, and 

 again, judging from our negative August line of observations between 30° and 60° E, there as yet does 

 not appear to have been any major overflow of this teeming population eastwards of 30° E. The West 

 Wind drift is barren except as before where it is affected by cold East Wind penetrations, namely, 

 south-east of Kerguelen, north-east of the Ross Sea near 150° W (both September records) and again 

 (possibly) in the southern part of the Drake Passage. Such observations as we have in the Pacific 

 sector (in the West Wind drift only) are negative except as aforementioned in such small part of it as 

 is affected by north-easterly outflow from the Ross Sea. As to what is taking place in the East Wind 

 drift, now completely encompassed by the winter pack, further comment is unnecessary, the probable 

 position there having already been outlined in the commentary on the winter and spring distribution 

 of the larvae based on the data (pp. 334-8) from the vertical nets.^ 



The developmental condition of the principal concentrations of the massed surface larvae in winter, 

 based throughout on our observations in the Weddell drift and on the South Georgia whaling grounds, 

 is shown in Fig. 116. The major features of it may be summarised thus: 



(i) Substantial numbers of purely larval swarms (Furcilias 4-6) persist throughout July and August, 

 giving place in September to older swarms consisting almost exclusively of Sixth Furcilias and adolescents. 



^ We found it convenient, and time saving, to use this, rather than the distal end of the rostrum, as the anterior end of the 

 body. In E. superba the rostrum projects forward as far as, but no farther than, the eye. In fixed specimens, however, the eye 

 blankets the rostrum when the animal lies, as it will only do, on its side. 



" See also pp. 355-6. 



