Professor Ivan Yefremov (born 1907) is well known both as a tireless fossil hunter and a talented science-fiction writer. His fantasy ranges between the mysteries of times long bygone and the distant future. His novels include The Land of Foam, where the scene is set in ancient Egypt and Greece, and the world-renowned Andromeda, in which his fantasy roams two thousand years ahead. The Heart of the Serpent, given in this volume, was written in 1959. Its subject is related to that of Andromeda. Anatoly Dnieprov (born 1919), the author of Siema, which he wrote in 1958, is a distinguished physicist who works at an institute of the U.S.S.R. Academy of Sciences. His first book appeared in 1946. His favorite subject is cybernetics - its amazing achievements to date and its breathtaking potentialities. Scientific authenticity is a salient feature of his writings. Victor Separin (born 1905), a journalist by profession, is editor of the Soviet popular geographic magazine Around the World. His fiction, which treats of present-day scientific and technical problems, is amazingly realistic. In this volume he is represented by The Trial of Tantalus, a story dealing with prospects of microbiology. Arkady and Boris Strugatsky, authors of The Six Matches, are frequent contributors to Soviet popular science periodicals. Few readers know, however, that the two brothers are not professional writers. Boris Strugatsky (born 1933) is an astronomer and works at the computer laboratory of Pulknovo Observatory. Arkady (born 1925) is a linguist and translator specializing in Japanese. Valentina Zhuravleva (born 1933) is a comparatively recent graduate of the Azerbaijan Medical Institute. She was probably prompted to try her hand at scientific fiction by the almost fantastic possibilities offering in the field of medicine. The bold flights of fancy in her scientific thinking make her stories particularly noteworthy. Bio-automation is the theme of her Stone from the Stars, written in