This book, developed from lectures given by Prof. Johansson at the University of Illinois in 1958-59, presents in "concise, objective, and thought-provoking terms his thoughts and evidence on the application of genetics to the difficult task of moulding an animal species to a modern need". The first 3 chapters deal with: population genetics and its application to animal breeding; immunogenetics; and monozygous twin research. The remaining chapters are devoted to reviews of breeding systems, assessment of breeding value, and the inheritance of various important characteristics including fertility, body size and conformation, udder development and milking rate, milk and butterfat yield, and milk composition. Chapter references and index are