Scale development in talpid3 mutant chick embryos.

The fact that dermal condensations are not, as they are in feather development, involved in early scale morphogenesis in birds suggests that in the mutant talpid3, where mesenchymal cell surface and motility properties are impaired, scales might develop relatively normally though feathers do not. This prediction has been checked using chorioallantoic membrane grafts of talpid and normal hind limbs, and found to be substantially justified although the abnormal overall shape of the talpid limb has a distorting effect on scale patterning. However, the abnormal talpid dermis seems to have effects on the direction and extent of epidermal invagination at scale margins. Since the control of epidermal invagination is a relatively unexplored area, this is a particularly useful finding.