The main theme of this monograph - conditions of regenera­ tion of organs in mammals - reflects an area of increasing empha­ sis which permeates much current Soviet research on regeneration. The introduction of this theme goes back about 25 years, and empha­ sis on the influence of environmental conditions upon regenerative processes has fluctuated until the mid-1960s, when the viewpoints on this subject were established in much the same form as they are expressed in this book. For years, Russian regeneration research has been charac­ terized by the presence of several dominant and often conflicting schools of thought. Since an acquaintance with these makes the in­ terpretation of many of the theoretical implications of this book, particularly in the introductory and concluding chapters, consider­ ably clearer, those not familiar with the Russian literature might profit by reading my brief survey of this field (Carlson, B. M., 1968. Re­ generation research in the Soviet Union, Anat. Rec., 160:665-674).