While translating this book, I was in close communication with the author, S. S. Shvarts (Schwarz), who read and commented on the entire translated manuscript. In particular, any ambiguities as to the identity of organisms described only by common names in the original text were removed, because the author kindly supplied the Latin names in all such cases. Com­ mon names are retained in the translation, but the Latin names are also added where needed. Some of the terminology used in the Russian is a transliteration from English words employed now more by European workers than Americans. I have defined these terms or noted their more common equivalents used in current American literature where it seemed useful in the text. A final chapter, "Recent Work on the Evolutionary Ecology of Ani­ mals," is presented as Appendix II to the translation of the original text. I have written this chapter in order to update the material presented in the original edition published in 1969. The chapter discusses important recent contributions relevant to the subject matter presented by Shvarts. I would like to thank W. Z. Lidicker, Jr., and Y. B. Linhart for reading this final chapter and providing very helpful suggestions and comments. I am particularly grateful to the author, S. S. Shvarts, for his careful reading of the translated manuscript.