Foreword, by A. S. Boughey -- The lemming cycle at Baker Lake, Northwest Territories, during 1959-62; discussion, by C. J. Krebs -- Animal numbers and behavior, by D. Chitty -- Endocrines, behavior, and population, by J. J. Christian and D. E. Davis -- The prey of carnivores during one cycle of mouse abundance, by O. P. Pearson -- Regulation in animal societies and population, by V. C. Wynne-Edwards -- The nutrient-recovery hypothesis for Arctic microtine cycles; introduction, by F. A. Pitelka -- The nutrient-recovery hypothesis for Arctic microtine cycles: ecosystem variables in relation to Arctic microtine cycles, by A. M. Schultz. -- The analysis of survival and reproduction in the unsprayed area (area 1), by R. F. Morris -- The development of predictive equations for the spruce budworm based on key-factor analysis, by R. F. Morris -- An experimental component analysis of population processes, by C. S. Holling.