DISTRIBUTION OF YOUNG STAGES OF EUPHAUSIA SUPERBA 155 



the frequency of occurrence is comparable to the frequency below 500 m. in earlier 

 larval stages. 



In the section of this paper dealing with the circumpolar cruise it was shown that 

 larvae of comparable stages of development to those last mentioned were almost in- 

 variably concentrated, whatever the time of day, in the upper of two oblique nets fished. 

 This localized distribution was most marked in the results of the June visit to the ice- 

 edge. John states that of two nets fished, one, i m. in diameter, towed at a depth of 

 2 m., caught large numbers of larvae, whereas the other, 70 cm. in diameter, towed 

 at 57 m., caught none. The process was repeated with like results. This was in close 

 proximity to pack-ice and in the daytime. Allowance has to be made for the superior 

 catching power of the i-m. net, but it is quite clear that the shoals of krill were limited 

 vertically to a range of a few feet. 



It has also been mentioned already (p. 149 supra) that, on the course taken by the 

 'Discovery 11' from Bouvet to South Georgia in October-November 1930, when the 

 ship was making its way along the edge of the pack, krill was almost always to be seen 

 at the surface in great quantity, with larval and adolescent forms predominating. 



VERTICAL DISTRIBUTION AT ST. 461 



An extract from the scientific log referring to this station says : 



Seven hauls were made at intervals of four hours with a series of six i-m. nets used obliquely. The 

 oblique nets were put on the wire at intervals of 143 m. with 140 m. between the upper net and the 

 surface. The total wire out was 855 m. The nets were hauled at 1.V-2 knots and when the upper one 

 had reached the surface the messenger was dispatched to close those below. Depths were determined 

 by a depth gauge at the end of the wire and Kelvin tube near the second net from the top, the depths 



of the individual nets being calculated The first six hauls covering a period of twenty-four hours 



were taken without any hitch, but in the seventh haul one of the messengers failed to release on im- 

 pact of that above and some nets were in consequence hauled open for longer than was intended. 



The station was made in 56° 44' S, 2° 23!' W to the south-west of Bouvet Island and 

 in the vicinity of pack-ice. As might have been anticipated from the time of year, 

 October 20-21, young E. superba were represented only by Furcilia 6 and small ado- 

 lescents. It is noteworthy that while over eighteen and a half thousand young krill were 

 taken in seven hauls, only 147 adults were found; of these 122 were in the G flight in 

 the net fishing between 750 and 560 m. and closed at 315 m. The remaining adults were 

 scattered throughout the nets of the other flights in number never more than four in 

 any one net. 



Table XL shows the quantities of young krill taken in the flights A-G. The depth of 

 the nets and time of day are stated. The numbers show that a distinction can at once be 

 made between the uppermost net catch of each flight and all the others. In five of the 

 seven hauls relatively enormous quantities of krill were taken in the uppermost net, and 

 in all seven more than 59 per cent of the total taken in each flight was in this net. In 

 dealing with the numbers in the percentage column of the table, therefore, the figure 

 given for the uppermost net is the percentage of the total caught in the flight of nets. 

 For the remaining five nets the figures are the percentages of total number in those nets 



