I am glad to welcome this reprint of a book which the late Dr. A. P. Orr and I had much pleasure in writing. Since it was first published in 1955 there has been a great expan- sion of work on the metabolism of copepods, especially on Calanus finmarchicus and its related species. Some pages of more recent references have therefore been added to the bibliography. In the main text there is, of course, no discussion of, or reference to, the work described in these papers, but they will be useful to students who want to pursue the subject further. In the additional references Calanus finmarchicus is taken in its original wider sense and includes those forms which are now con- sidered to be separate species, e. g. C. helgolandicus, C. pacificus, C. glacialis, C. ponticus. Millport, January 1972 S. M. Marshall Frrmlispil1ce Photo: D. P. WILSON Female Calanus finmarchi.cus (helgolandicus form) THE BIOLOGY OF A MARINE COPEPOD Calanus finmarchicus (Gunnerus) by S. M. MARSHALL, D.Se., F.R.S.E., and A. P. ORR, M.A., D.Se., F.R.S.E.