THE LARVAL STAGES ii, 



Table 20. Diurnal vertical distribution of total larvae {Calyptopis 2 to Furcilia 4) 

 recorded by Fraser at depths below 250 m. 



Depth 1400-1800 1800-2200 2200-0200 0200-0600 0600-1000 1000-1400 



(m.) Second Calyptopis 



500-250 39 2 2 7 14 45 



750-500 I 2 — — _ _ 



1000-750 21 I — J 



Third Calyptopis 

 500-250 93 18 — 2 9 203 



750-500 — — I _ 3 J 



1000-750 2 — 2 — 



First Furcilia 



500-250 17 2 — — I 156 



750-500 _____ J 



1000-750 2 I — — 



Furcilias 2-4 



500-250 49 3 — — 5a 132 



750-500 _ _ _ _ 21 36 



1000-750 I — — — 



Fraser (1936, p. 152, Figs. 72 and 73), in Calyptopes i, 2 and 3, in Furcilia i and in the combined 

 Furcilia stages 2, 3 and 4, shows a very much more pronounced diurnal vertical movement than my 

 Figs. 9-1 1 reveal, his results for Furcilias 5 and 6, however, being in general agreement with mine. Our 

 conflicting findings, in so far at least as the First Calyptopis is concerned, can, however, partly 

 be explained because the volume of material at my disposal was so large^ and partly because in 

 presenting his data Fraser did so without regard to the possibility that the climbers could prejudice 

 the result. In consequence his graphs for the period 0600-2200 hr., from dawn in fact throughout 

 daylight to nightfall, are affected by the disturbing influence of the deep, still climbing, larvae (see again 

 Fig. 6) that spring from the moulting Metanauplii at Stations 636, 637, 638 and WS 197. No 

 such disturbing influence, of course, can have affected his graphs for Calyptopes 2 and 3, Furcilia 

 I and Furcilias 2-4, for such larvae have long since accomplished the developmental ascent and their 

 vertical movements can no longer be obscured by the presence in deep water of young climbers still 

 reaching for the surface, as the vertical movements of the First Calyptopis so often are. Even so, 

 the numbers of these stages he has recorded below 250 m., although distinctly suggesting (Table 20) 

 a diurnal migration by some of the larvae well down into the warm layer by day, are not on the whole 

 I think large enough to justify the conclusion that the mass of the surface population behaves in a 

 similar way. Indeed the massive accumulation of larvae revealed by our two short-term 50 m. hauls 

 above 100 m. (see again catch-tables for Figs. 9-1 1 which include Eraser's catch-figures as well as my 

 own), throughout all hours of night and day, distinctly suggests it does not. If it did I should have 

 expected equally large daylight gatherings from below 250 m., where our nets are hauled for five 

 times as far, with daylight scarcity or even void at the surface. 



I therefore conclude that although both Calyptopes and Furcilias migrate away from the 

 surface down into the warm deep layer, especially it seems (Figs. 9 and 11) between 0600 and 



1 A conspicuous deep day massing of First Calyptopes, 70% of them in the 250-100 m. layer, the remainder in the 

 500-250 m. layer, appears between 1400 and 1800 hr. in Eraser's Fig. 72. This graph, however, is based on the occurrence 

 of only seven specimens. 



