Feather morphogenesis and feather pattern in normal and talpid mutant chick embryos.

A comparative study of feather morphogenesis and the development of feather pattern in normal and talpid embryos has been carried out. The development of talpid* CAM grafts shows that the effect of the gene is autonomous in the skin. The most striking effect of the gene upon feather morphogenesis is the failure of normal feather germ condensations to appear within the dermis. This is reflected in the abnormal distribution of alkaline phosphatase through the dermis. Dermal cells within and between condensations are not orientated in the mutant as they are in normal embryos, probably owing to the same defect in cell behaviour which causes condensation failure in talpid precartilage mesenchyme. The role of dermal cell orientation and movement in generating the overall feather pattern is examined in both normal and talpid embryos.