Regulation of deficiencies along the proximal distal axis of the chick wing-bud: a quantitative analysis

The wing-bud shows zero regulation following removal of a whole slice of the proximaldistal axis from stage 22 or later. Prior to this it is possible that it may show some regulation. Some of the apparent regulation may be explained by the way in which the limb grows. The bud never shows perfect size regulation or morphallaxis. The proximal-distal axis of the bud between shoulder and wrist expands uniformly from stage 20.