, 94 DISCOVERY REPORTS 



applicable to the present work because they refer to local areas and for the most part do not extend to 

 the true oceanic fauna and flora. There are relatively few data from oceanic areas, and apart from the 

 observations to be considered here there are in the Southern Ocean only a few ' Meteor ' stations and 

 the material collected on the B.A.N. Z.A.R. Expedition and described by Sheard (1947). 



From other regions there are the results of the few expeditions already mentioned, which, although 

 limited, have allowed something to be known of conditions in the open ocean. The ' Meteor ' observa- 

 tions, for example, have enabled Hentschel to make valuable distinctions between regions of rich and 

 poor plankton in the Atlantic Ocean. 



In the warmer latitudes it may be that there are no very great seasonal variations in the standing 

 crop. Nevertheless, when observations are made only at one time of year there can be no certainty 

 that the amount measured is much indication of the amounts which may be present at other times of 

 year. Indeed, it seems hardly possible to make true quantitative comparisons of fertility over large 

 areas without data suitably spread in time as well as in space. It is felt that the material collected by 

 the 'Discovery II ' in the Southern Ocean allows for a new step forward because it has been taken 

 from almost all parts of a large oceanic area — the Southern Ocean — at almost all times of year. 

 Measurement of the volumes of samples is no doubt a crude method, but it allows many samples to 

 be dealt with quickly and it gives an approximate estimate of the standing crop which is at least 

 significant for large-scale or persistent differences. Furthermore, measurements from the Southern 

 Ocean can be used to some extent as a basis for comparison of the standing crop with that of other 

 oceanic regions. 



Probably no other oceanic region is richer in life than the Antarctic, an area far greater than any other 

 of comparable fertility. It is hoped that even a rough comparison of the abundance of plankton in 

 different parts of the Southern Ocean, an account of the variations which take place, and an indica- 

 tion of the standing crop in the Antarctic compared with other regions, will contribute to what is 

 known of the fertility of the oceans as a whole. 



The features to be measured and compared are (a) the seasonal vertical movements between super- 

 imposed water masses, and seasonal variations in the amount of plankton, (b) the standing crop in 

 different latitudes, and (c) the standing crop in different longitudes and faunistic areas. 



ACKNOWLEDGEMENTS 



This study was undertaken at the suggestion of Dr N. A. Mackintosh, C.B.E., who has extended 

 helpful criticism and advice. 



I was also fortunate to have the help and advice of many of my colleagues, and I am particularly 

 grateful for the suggestions of both Dr T. J. Hart, who read the first draft of the paper, and Mr R. I. 

 Currie, who read and corrected the typescript. I should also like to thank Mr A. de C. Baker, who 

 assisted me in the initial stages of the work, and Mr J. W. S. Marr, who read and advised me on the 

 sections relating to his special study — Euphansia superba. 



MATERIAL 

 This paper is based on material collected with the ' Discovery ' pattern 70 cm vertical closing net 

 (N70V), the construction and operation of which is described in detail in Kemp, Hardy & Mackintosh 

 (1929, pp. 183 and 199). The net provides a standard series of hauls which, by virtue of a constant 

 speed of hauling and an accurate knowledge of the depth of closure, are more reliable for quantitative 

 purposes than samples from horizontally or obliquely towed nets (Mackintosh, 1937, p. 371). The 

 N70V is closed on the Nansen principle by means of a throttling rope, and Barnes (1949) maintains 



