Distinguished for his researches on stationary time series and in population genetics. The application of his work on stochastic processes has led to the mathematical study of animal populations and the development of a theory of storage systems, with particular reference to water storage; his mathematical theory of population genetics provides a rigorous treatment of random processes and introduces new models and techniques to study the effects of such factors as overlapping of generations, family structure and non-random mating, which have not hitherto been considered.