This 1981 collection of papers focuses on a wide range of topics in the general field of evolutionary biology. It will be of interest to scientists and advanced students concerned with cytogenetics and evolution. The authors are distinguished workers in their field who have been associated with Professor M. J. D. White, who was the world authority on chromosomal evolution and speciation, to whom this volume was presented on the occasion of his seventieth birthday. Their contributions cover hybrid zones, speciation and chromosomal evolution in various groups of insects, lizards and mammals.