Abstract
SUMMARY 1. Response to selection was achieved with all strains of Myxoma virus used. 2. Heritability of resistance to myxomatosis was determined by intra-sire correlation using survival time as an index and by an all-or-none probit analysis. Both resulted in an estimate of heritability of about 35–40%. 3. The ability of animals to survive myxomatosis varied widely with environ mental variation in time. I am indebted to W. Menzies for his very able assistance in all aspects of the work; to Dorothy Conolly for her critical assistance with data analysis, and to Dr J. M. Rendel for suggesting the probit analysis for determining heritability.