Studies of oogenesis occupy an important place in current in­ vestigations in developmental biology. Today no one has any doubt whatsoever that oogenesis is not just the prelude to development, but is development itself, and a very essential part of it. These words of an eminent Soviet scientist, B. L. As taurov , taken by T. B. Aizenshtadt as an epigraph to her chapter in this book, make a good epigraph for the entire book. It is now clear that during oogenesis not only vast reserves of ribosomes and mitochondria, of yolk, carbohydrates, and lipids, and of enzymes for protein and nucleic acid synthesis and for carbohydrate and fat metabolism (which ensures the energy supply and metabolism of the oocyte and the developing embryo) are formed, but also long-lived mRNA and proteins are synthesized, which determine both the completion of oocyte maturation and the initial stages of embryonic development. In the last 15-20 years, the use of molecular biology methods, electron microscopy, autoradiography, and microsurgical methods of experimental embryology in studying the pre-embryonic development of animals has greatly increased our knowledge of oogenesis. This has led to the need to systematize the data obtained, to reinter­ pret old ideas, and to review the results obtained by new research trends which have emerged in the last few years and which are of general biological interest. Such a task was undertaken in the book Sovremennye Problemy Oogeneza (Current Problems of Oogenesis), published in 1977 (in Russian).