Over two-thirds, of the earth's surface is covered by oceans, and the authors, two authorities on this vast subject, describe. Man's knowledge of the seas and how it is gained. They discuss the nature of oceans, the action and behaviour of tides, plant life, animaI life from whales to pIankton, sea fisheries and research, and Man's exploitation and cultivation of products. Man's infiuence on the sea is a current topic with the everpresent problem of pollution. Very few co-authors have had the good fortune to see the publication of an extensively revised, enlarged and newly illustrated edition of their book almost half a century after its initial appearance in 1928. Yet it is felt that The Seas still holds its pIace as a book covering those aspects of the biology of the sea most likely to interest the generaI reader as well as to stimulate the inquiring student. The outlines followed in this fourth edition remain unchanged except for the inclusion of two new chapters. There are 48 plates, 24 in colour and 24 in black and white, with numerous line drawings throughout the text.