4 DISCOVERY REPORTS 



would be useful at this stage to present the systematic results in advance, particularly since there has 

 been such confusion and divergence of opinion regarding the relationship between S. fusiformis and 

 S. fusiformis aspera. 



ACKNOWLEDGEMENTS 



This study would have been severely restricted in scope were it not for the specimens so kindly made 

 available to me by other workers. It is with pleasure that I record my indebtedness to Professor T. 

 Tokioka, Seto Marine Biological Laboratory, Japan; Dr Leo Berner, Jnr, Scripps Institution of 

 Oceanography, La JoUa, U.S.A. ; Dr J. L. Yount, University of Florida, Gainesville, U.S.A. ; Dr J. H. 

 Eraser, F.R.S.E., Department of Agriculture and Eisheries for Scotland, Marine Laboratory, 

 Aberdeen; and Dr E. Beyer, Institutt for Marine Biologi, Oslo, Norway. I should also like to thank 

 Dr E. S. Russell, E.R.S., Director, Marine Biological Association, Plymouth, who kindly allowed me 

 to participate in a cruise of R.V. 'Sarsia' where I was able to examine material from the Bay of 

 Biscay. 



I am particularly grateful to Dr J. H. Eraser, E.R.S.E., for his comments on the original typescript 

 and to my colleague, Mr P. M. David, who has given me helpful advice throughout this study. 



I wish to thank Baron Marc de Selys Longchamps for permission to reproduce two figures (fig. za, h) 

 from the Reports of the Belgica Expedition, and the Editor, Commonwealth Scientific and Industrial 

 Research Organization, Melbourne, for permission to reproduce two figures (fig. i a, b) from. 

 H. Thompson's Pelagic Tunicates of Australia. Eigures i and 2 have been prepared for publication 

 by Mr A. Style. 



MATERIAL AND METHODS 



This paper is based for the most part on material collected by ships of the Discovery Committee and 

 subsequently the National Institute of Oceanography. As the ultimate aim of the work was a quanti- 

 tative appraisal of an animal's distribution in time and space in relation to its life-history, I have used 

 plankton samples taken with a standard net fished in a standard manner. In this paper only a small 

 part of the total data — that relating to the systematic results — will be used. 



Most of the material was collected with a i -metre stramin net towed obliquely (NiooB) or hori- 

 zontally (NiooH) at stations which were selected, from a vast number available,, to give as com- 

 plete a geographical coverage of the Southern Ocean as possible. It was soon realized that the 

 subantarctic and antarctic data should be compared with that from other oceans, and so where lines of 

 stations have extended north of the subtropical convergence (indicated by a dotted line in Text-fig. 10, 

 p. 28) use has been made of samples collected at them irrespective of the gear used. Such samples 

 include those taken with the 2-metre stramin net fished obliquely (TYEB) or horizontally (TYEV) and 

 use has also been made of material collected in the North Atlantic with the Isaacs-Kidd Midwater 

 Trawl. While not relevant to this paper, full descriptions of the i -metre and 2-metre nets and their 

 method of use may be found in Kemp, Hardy and Mackintosh (1929), while the Isaacs-Kidd Mid- 

 water Trawl is described by Isaacs and Kidd (1953). 



I have, in addition, been able to examine specimens collected with a variety of gear from areas not 

 represented in the Discovery Collections. These include specimens from the eastern and central 

 Pacific, Japan, Bay of Biscay, and Iceland. I have also been able to augment the Discovery Pacific 

 stations with material collected quite independently by the Norwegian 'Brategg' Expedition of 

 1947-48. 



All the measurements on which this study is based were made on specimens preserved in 5-10% 

 neutral sea-water formalin. As the period of preservation prior to examination varies from a few 

 months to 30 or so years some shrinkage can be assumed to have taken place. A few specimens, how- 



