The somitic mesoderm of the wing level was replaced in a two-day chick embryo by quail somitic mesoderm obtained from the level of the wing, the leg or the neck. The musculature of the host's wing on the operated side was exclusively or almost exclusively constituted by quail cells, whereas the skeleton, the dermis, the tendons and the muscular envelopes were formed by chick cells. This result demonstrates that, under the present experimental conditions, the wing musculature is originated from the somitic mesoderm of any level of the cephalocaudal axis.