Introgressive hybridization

This little book is concerned with hybridization under those circumstances which we so glibh^refer to as "natural conditions," that is, with the results of hybridization outside the laboratorj nd the breeding plot. It passes no judgments on the importance of hybridization in evolution but attempts to take this whole problem outside the area of argument and opinion and into the zone of measurement and analysis. It is verj^largely concerned with how the effects of hybridization can best be measured in natural populations and with a discussion of the forces at work in such populations.