Toc: Content: Edited by Page iii Copyright page Page iv Contributors To Volume VI Page v Map Construction in Neurospora Crassa Original Research Article Pages 1-93 Raymond W. Barratt, Dorothy Newmeyer, David D. Perkins, Laura Garnjobst Genetic Changes in Human Populations, Especially Those Due to Gene Flow and Genetic Drift Original Research Article Pages 95-139 Bentley Glass Monozygotic Twins in Cattle Original Research Article Pages 141-181 John Hancock The Genetics of the Newer Human Blood Factors Original Research Article Pages 183-234 Philip Levine Comparative Incompatibility in Angiosperms and Fungi Original Research Article Pages 235-285 D. Lewis Cytoplasmic Inheritance in Epilobium and Its Theoretical Significance Original Research Article Pages 287-401 P. Michaelis The Genetics of Colias (Lepidoptera) Original Research Article Pages 403-450 Charles L. Remington Artificial Insemination and Livestock Improvement Original Research Article Pages 451-472 Alan Robertson Author Index Pages 473-480 Subject Index Pages 481-485