THE NORTH SEA: CHALLENGE AND OPPORTUNITY, Edited by M. M. Sibthorp. Published for the David Davies Memorial Institute of International Studies, by Europa Publications Ltd. 1975, 324 pp. £6.95. MAMMALS OF THE SEA; INSTINCT AND INTELLIGENCE; PHARAOHS OF THE SEA; Jacques Cousteau, 1975, Angus and Robertson, London. All £2.80. PYCNOGONIDS, P. E. King, 1974, St. Martin's Press, New York. $8.95. GEOGRAPHICAL AND SEASONAL VARIABILITY OF MARINE PLANKTON. Edited by Zh. A. Zvereva. Academy of Sciences of the U.S.S.R., Zoological Institute (Translated from Russian—Israel Programme for Scientific translations, Jerusalem, 1975). 303 pp.