SELECTION OF MICE FOR BRAIN-WEIGHT

The results of two experiments on selection of laboratory mice for lar ge and small brain weight are presented. Selection was based on the re gression relationship between body and brain weight. This allowed cons iderable differences in brain weight to be obtained accompanied by ins ignificant interlinear differences in body weight compared to the rang e of intralinear variation. The two lines of mice with a large and a s mall brain weight (F-9-F-10) differed significantly in brain weight. T he absolute difference was 60-70 mg, i.e., approximately 13% of the br ain weight in the original heterogeneous population.