230 



DISCOVERY REPORTS 



A complete record of their numbers is given in Appendix II. 



They occurred in the largest numbers in the top ioo m., as will be seen from the 

 following table , but it is likely that we are dealing with more than one species , one or more 

 of which are inhabiting deeper layers than those found near the surface. 



Table XXXVIII 

 The depth distribution of Oikopleura spp. as shown by the N 70 V nets 



THE ZOOPLANKTON OF DIFFERENT REGIONS 

 WITHIN THE AREA 



We have seen (on p. 68) that it was possible to divide the area into a number of 

 regions each of which had a characteristic phytoplankton. For convenience we termed 

 the groups of stations comprising each region a phytoplankton group and numbered 

 them I to V. The distribution of these groups is shown in Fig. 35 and they are made 

 up as follows: 



Group I. Water of Bellingshausen Sea origin. 

 Group II. An area of mixture to the west of the island. 

 Groups III and IV. Water of Weddell Sea origin and mixture. 

 Group V. Coastal water. 

 There are also the stations in the sub-Antarctic Zone across the line of Antarctic 

 Convergence. 



We might expect each of these areas to have also a characteristic zooplankton, but 

 actually in general we find surprisingly little difference in their fauna. The average 

 number of the more important organisms taken at the stations within each group is 

 shown in Table XXXIX. Naturally the plankton of the coastal stations and that of the 

 sub-Antarctic stations will differ in some important respects from that of the remaining 

 groups. Drepanopus, as we have seen, is a shallow-water coastal form; the copepods 

 Metridia gerlachei, M. lucens and Scolecithricella minor are deep-water forms, likewise 

 the Radiolaria, and these are rarely met with in the coastal regions. The sub-Antarctic 

 stations are marked by an abundance of Calanus propinquus, Ctenocalanus vanus and 

 Metridia lucens, and an absence, or all but absence, of the Antarctic copepods Calanus 

 acutus, Metridia gerlachei and the Euphausians E. superba and E. frigida. The zoo- 



