362 DISCOVERY REPORTS 



the conditions in the field and the nature of the survey attempted is discussed in 

 detail. 



Part II deals with the phytoplankton. A list of species indicating those of greater 

 importance is given on p.. 41. The distribution of the different species is described 

 (pp. 42-64) and their relative abundance considered (pp. 64-65). The diatom Coscino- 

 discus appears to make a vertical migration towards the upper layers during the daytime 

 and away from them at night (pp. 45-46). The phytoplankton communities of the 

 different regions within the area examined are compared (pp. 65-76) and five different 

 types, called "phytoplankton groups", are recognised within the area examined. A 

 marked change in the phytoplankton is recorded in passing from the Antarctic to the 

 sub-Antarctic Zone (pp. 75-76). The production of phytoplankton in relation to 

 hydrography is discussed (pp. 76-87). Attention is drawn to the high phosphate con- 

 tent of the Antarctic waters which cannot be a limiting factor to production (pp. 76-77). 

 The distributional pattern of phytoplankton production bears a close correlation with 

 that of the reduction in phosphate content of the water and a lesser correlation with 

 increased oxygen content is demonstrated (pp. 80-85). Various factors governing the 

 production of phytoplankton are considered and a hypothesis relating such production 

 with the mixing of waters of different origin is put forward (pp. 85-86). The seasonal 

 changes in the phytoplankton are briefly discussed (p. 87). Twenty-five species of 

 phytoplankton common to the northern and southern hemispheres are recorded from 

 our collections (p. 87). 



Parts III and IV deal with the zooplankton. A list of species indicating those of 

 greatest importance is given on p. 89. A comparison is made of the composition of the 

 catches of the different nets employed (p. 92). The horizontal and vertical distributions 

 of the different species are described in the order given in the foregoing list (pp. 93-230). 

 Where possible notes on their general natural history are included. An increase in the 

 number of species of Copepoda at different levels descending from the surface to 750 m. 

 is clearly demonstrated (p. 121). An association is shown to exist between the amphipod 

 Vibilia antarctica and Salpa fusiformis (p. 199). The importance of Euphausia superba 

 in the economy of the Antarctic seas is discussed in the light of past and present records 

 (pp. 208-210). The swarming of these Euphausians was observed in the fjords (p. 210). 

 Abundant evidence regarding the nature and extent of the vertical migration of the more 

 important species of zooplankton organisms is provided (pp. 231-253). Nearly all 

 organisms inhabiting the upper 250 m. of water display such migrations, notable ex- 

 ceptions being the Copepoda Calanus acutus, Rhincalanus gigas and Oithona frigida, and 

 it is noteworthy that these organisms are taken only rarely in the top 50 m. (p. 241). 

 The Copepoda Pareuchaeta antarctica, Scolecithricella minor, Pleuromamma robust a, 

 Metridia gerlachei, M. lucens and the Euphausians E. frigida and E. triacantha are shown 

 to make very extensive and rapid vertical migrations, which appears to preclude the 

 possibility of locomotion itself being sufficient to account for them (pp. 236-240). 

 Experiments with series of consecutive net hauls demonstrate a remarkable patchiness 

 in the distribution of a number of forms, notably in Euphausia superba, Parathemisto 



