THE INFLUENCE of the phenotype for a simply inherited or qualitative trait on a more complex trait such as body weight has been studied to some extent in chickens.Kan et al. (1959) reported that comb type (single or pea) had no significant influence on body weight at six weeks of age; however, when housed at seven months of age, the single-comb birds were heavier than the pea-comb ones. Siegel and Dudley (1963) reported that cockerels with pea combs were significantly heavier than those with single combs at six and nine weeks of age in only one of three experiments. No significant differences were observed in the other two experiments at three, six, or nine weeks of age. Collins et at. (1961) concluded that the weight differences between single and heterozygous pea-comb progeny in favor of the single-comb phenotype were generally greater and more frequently significant in the male than…