INTRODUCTION A biological study of the Black Sea and of the Sea of Azov presents considerable difficulties to western scientists, because a large number of the newer Soviet journals are not available, either in Western Europe or in America, and reprints of papers are not obtainable. An attempt has nevertheless been made to prepare as detailed a report as possible for inclusion in the present work. Purely faunistic lists have had to be subordinated to a general ecological account and to a historical review, and the biological peculiarities associated with the hydrographic cycles require special emphasis. For several years the writer had the opportunity to make faunistic and ecological studies on the Black Sea, especially on the Bulgarian coast, which had previously been studied very little. He also visited the Rumanian coast, including the Danube delta, the Russian area at Odessa, the Crimean coast, the Caucasian coast, and a part of the Sea of Azov. There are scarcely any observations available for the Anatolian coast, so that a general biological account of the Black Sea must depend on inference for this section. A valuable base for the present review has been Zenkevich’s Fauna and Biological Productivity of the Seas, Vol. II, The Seas of the USSR (1947). Some of the references, unavailable to the author in the original, are taken from this work. I. PHYSICAL GEOGRAPHY OF THE BLACK SEA The Black Sea and the Sea of Azov form an almost isolated body of water, extending far into the greatest...