330 DISCOVERY REPORTS 



in the three main oceanic regions, as shown in Fig. 17. Another interesting point may 

 be seen on comparing Fig. 10, which shows the cycle in the oceanic Northern Region, 

 with Fig. 13 showing the cycle in the neritic South Georgia area. Apart from the 

 vastly greater richness of the latter it will be seen that the maximum is attained some- 

 what earlier in the year, in striking agreement with Gran's observations upon offshore 

 and inshore phytoplankton off the coast of Norway. 



Our ideas of the extreme richness of phytoplankton production in Antarctic seas 

 were gained when the work was chiefly confined to the Falkland sector. Now that 

 2500-]— 



JanuarL| Februart| March Apnl MaL| June JuIl) August September October November December 



JuIlj 



August September October November December Januaru February Marcti Apnl 



Mau 



June 



Fig. 18. Seasonal variation in plant pigments per m.^ in the Northern Region of the Antarctic zone com- 

 pared with that in the English Channel (monthly figures calculated from Harvey et al. 1935, Fig. i). Thick 

 line: Northern Region. Thin line: English Channel. 



larger numbers of observations from more truly oceanic areas are available it is evident 

 that these ideas stand in need of some modification. The effect of land masses in 

 producing conditions suitable for rapid, rich phytoplankton development appears to 

 be very important, as has long been known in the northern hemisphere. In the far 

 south, however, where all biophysical phenomena appear on the grand scale, the bene- 

 ficial effects of neritic influence appear at much greater distances from land. Only 

 where these influences are felt do the Antarctic seas retain their claim to be amongst 

 the richest in the world. 



A comparison of the cycle in the oceanic Northern Region and that in the English 

 Channel (with the appropriate double-time scale) is given in Fig. 18. It will be seen 



