46 DISCOVERY REPORTS 



elements and Furcilia 3 in which the elaboration of the telson and ' final definition ' of the pleopods 

 takes place. His Furcilias i and 2 are the same as Eraser's but his FurciUa 3 telescopes Eraser's 

 Furcilias 3, 4, 5 and 6. In this report I follow Eraser throughout, regarding the lumping of his 

 Eurcilias 3-6 into a single stage as an unnecessary over-simplification of the developmental path he 

 elaborated with such care and precision. As Boden (1955), who also follows Eraser, has said, 'it is less 

 useful to "lump" the furcilia stages than to "split" them', and this became repeatedly obvious to me 

 when I began to work out the distribution and horizontal movements of the larval population, and 

 again when I came to investigate the swarming habit to which (p. 226) the young krill are prone. 

 MauchUne (1959) follows Sheard, except that he suggests it would be better if all furcilias with five 

 setose pleopods, but retaining the primitive seven-spined telson condition of Eraser's Eurcilias 1-3, 

 should be excluded from Eurcilia 2 and regarded as a separate stage, Eurcilia 3, his Eurcilia 4 

 telescoping Eraser's Eurcilias 4, 5 and 6. It will become abundantly clear, however, as we proceed 

 that neither the Sheard nor the Mauchline plan can be used to follow the growth, distribution and 

 movements of the larvae with precision and that neither will serve to demonstrate the finer points of 

 the structure of the larval swarms. It would repeatedly happen in fact, to take a concrete instance 

 involving distributional confusion, or misrepresentation, that charts portraying the distribution of the 

 last larval stage of Sheard or MauchUne would at the same time purport to display the distribution of 

 a developmental phase, with all the hard and fast morphological characters of Eraser's EurciUa 6, 

 when it did not in fact exist in the plankton. Marshall (1954) calls attention to some striking anatomical 

 diflterences between this voracious herbivore and certain omnivorous or rapacious Antarctic euphau- 

 sians of essentially more catholic taste. Peters (1955), reporting on the examination of some 8000 whale 

 stomachs by German expeditions from 1936 to 1939, notes that the percentage of empty stomachs in 

 the pelagic catch is higher than that found by Mackintosh and Wheeler (p. 138) at South Georgia. 

 South-west of Kerguelen, in the early part of December 1937, he records a maximum percentage 

 empty of 897, the pronounced local scarcity of euphausians this high figure suggests again being 

 attributable to the fact that the expedition concerned was operating in the krill-poor West Wind drift. 

 Marr (1955) gives a condensed account of the southern krill referring briefly to its great ecological 

 importance, its virtually nektonic behaviour, uneven distribution, swarming habit and predominantly 

 surface habitat. Marr (1956) gives a preliminary account of its distribution during the modern 

 pelagic whaling season showing that the principal concentrations are confined to high latitudes 

 near the Antarctic mainland and elsewhere only to such lower latitudes as are affected by the 

 current from the Weddell Sea. He calls attention to the marked asymmetry of its circumpolar dis- 

 tribution, refers again to its congregating at the surface, and shows that east of 30° E the circumpolar 

 West Wind drift is very sparsely populated. Zimmer (1956) gives a useful summary of the work of 

 earlier students of this species, referring particularly to the more recent papers by Mackintosh (1934), 

 Hardy and Gunther (1935), Eraser (1936), John (1936), Bargmann (1937), Barkley (1940) and Barg- 

 mann (1945). Dall and Dunstan (1957) record euphausian remains, undoubtedly those of E. superba, 

 in the stomach of a humpback caught off southern Queensland in July 1956 and suggest that the krill 

 are not confined to the Antarctic, but may sometimes occur as bathypelagic inhabitants of lower 

 latitudes to which they would get carried in the deep north-flowing Antarctic intermediate layer. 

 As Jonsgard (1957) points out, however, this at first sight quite sensational find, without postulating 

 any pathological condition affecting digestion, could readily be explained if the animal had been 

 killed immediately on arrival from the southern feeding grounds after an extraordinarily rapid 

 passage.! j^g emphasises that even in 'burnt' whales, in which the stomach contents have been 

 reduced to an amorphous chyme, partially digested eyes, fragments of carapaces and other hard 

 1 At a steady 4-3 knots (Chittleborough, 1953) it could have done it in 21 days. 



