After heterotopically grafting premigratory neural crest cells from quail 
embryos to the wing buds of chicken embryos, Schwann cells, non-epidermal 
melanocytes and epidermal melanocytes develop in the wings of the host embryos. 
This indicates that these neural crest derived cell populations are determined 
before the onset of emigration of neural crest cells from the crest. Epidermal 
melanocytes of donor origin are found essentially distally from the grafts, 
whereas non-epidermal melanocytes and Schwann cells are found proximally and 
distally therefrom. If the apical ectodermal ridge is removed from wing buds 
that have received a graft of neural crest cells, the directionality of the 
migration of epidermal melanocytes is lost. This indicates that the apical 
ectodermal ridge might account for the directional movement of epidermal 
melanoblasts. This situation is compared to myoblasts that behave in a similar 
way within the avian embryonic wing bud.