2i 4 DISCOVERY REPORTS 



In summer the average quantity of plankton between ioo and o m. is a reflexion of the variation in 

 the total quantity of plankton between iooo and o m., which, of course, is consistent with the fact that 

 in summer the bulk of the plankton is concentrated near the surface. In winter, however, there is 

 no great latitudinal variation in the upper layer, and this is in contrast to the marked variation, 



30 35 40 



LATITUDE 



65 70 



SOUTH 



Fig. io. Comparison of the mean quantities of zooplankton in different latitudes in winter and summer. Results are given 

 for the ioo-o m. horizon and for the whole water column sampled (iooo-o m.). No summer observations are available between 

 o° and 30° S. Numbers of observations are given in Table 5. 



similar to that in summer, of the total volume of plankton. This again is undoubtedly due to the 

 seasonal vertical variation that occurs in the distribution of the plankton, the bulk of it being concen- 

 trated below 250 m. in winter, more particularly in the Antarctic but also in the sub-Antarctic. 



The presentation of the data in the form of Fig. 10 has the disadvantage that it gives no indication 

 of the range of variation in individual volume that occurs between the arbitrary latitudinal limits. 

 In Fig. 11 all the individual total volumes from each station (i.e. 1 000-0 m.) have been plotted 

 according to their actual latitude in the form of a scatter diagram, and the latitudinal range has been 



