Apoptotic bodies within feathers were observed mainly in the thin layer of epithelium bounding the medulla of the ramus within individual barb ridges. Apoptotic cells within the feather were distributed along the longitudinal axis of the feather, and were highly localized along the proximal distal gradient. This preliminary investigation supports our hypothesis that apoptosis plays a role in both sculpting of feathers and shedding of the periderm. As is the case with cell differentiation within the feather, apoptosis seems to move proximally along the longitudinal axis of the feather as development progresses. Furthermore, there is strong evidence to suggest that the loss of the periderm is temporally specific, and does not occur until day 18 of incubation.
Apoptosis appears to be the mechanism by which the periderm is removed.
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