In an effort to provide further information concerning the pleiotropic effects of the gene mutation responsible for micromelia in White Pekin ducklings, a histological examination was made oq the abnormal feathers associated with the mutation. Abnormalities found in mutant feathers included decreased overall size, absence of prelumulae and prefiloplumulae feathers, an abnoramlly small rhachis with a disproportionally small medulla, thickening of the feather-sheath, and increased abundance of pulp cells. Embryos having the most abnormally developed feathers and the thickest periderm and feather-sheaths. The nature of many of the abnormalities found in mutant feathers suggests a common source in defective embryonic mesoderm.