390 DISCOVERY REPORTS 



SU 



rface at night and descends during the day, and its distribution in October and No- 

 vember is much the same. This species is mostly to the north of the Antarctic con- 

 vergence in December and March, but in September, October and November it ex- 

 tends farther south. 



Sagitta maxima rarely enters the surface layers. Table VIII shows that in summer 

 (December and March) it is commonest at 250-100 m., in September it is a little deeper 

 and in spring it approaches the December level. 



S. gazellae (Table IX) a conspicuous Chaetognath in the Antarctic macroplankton, 

 shows no definite tendency to descend into deep water in winter. It occurs near the 

 surface in each month except November, and even here it might have been found in the 

 upper layers if the stations had been extended a little farther north. 



S. planctonis (Table X) like S. maxima does not enter much into the surface layers. 

 It shows a distinct descent in September, no specimen being taken at less than 500 m. 

 The distribution in October and November is intermediate between that of September 

 and December. 



S. maxima and S. gazellae occur rather more frequently on the north side of the 

 convergence, but S. planctonis is commoner to the south. 



The small Siphonophore, Dimophyes arctica, resembles Sagitta maxima in living in 

 summer at about 250-100 m. and descending a little in winter (Table XI). 



Parathemisto gaudichaudi (Table XII) is nearly always between the surface and 250 m. 

 and although occasional specimens are taken in deeper water we have no evidence of an 

 annual vertical migration. The adults were mostly taken in December, March and 

 September, and the young forms predominated in spring. 



Conchoecia hettacra (Table XIII) is another species exhibiting daily vertical migra- 

 tions. The small numbers that were taken suggest that it may reach higher levels in 

 March than in other months, but none was taken in September, and the question of an 

 annual migration must be left open. 



Primno macropa (Table XIV) does not show any very definite grouping in its vertical 

 distribution. It is very scarce in winter, and there is nothing to suggest that it descends 

 into deeper water at that time of year. The few adults taken in March however were in 

 deep water, and the younger forms in this month occurred at all depths. 



Enkrohnia hamata f. antarctica (Table XV) is a normal inhabitant of deep water. It 

 very rarely appears in the Antarctic surface water but it seems to lie a little deeper in 

 September than in other months. 



Haloptilus oxycephalic (Table XVI) was scattered irregularly in depth and latitude, 

 and no definite conclusions can be drawn. 



Calanus propinquus (Table XVII) was very scarce in 8o° W in comparison with its 

 abundance in some other parts of the Antarctic, and the figures here are not perhaps 

 very valuable. It lives mainly in the upper layers and there is no suggestion of a descent 

 in winter. In September indeed it was taken only at the ice edge and in the Antarctic 

 surface layer, and it may be mentioned that it was taken here also in moderate numbers 

 in the oblique nets. 



