Retinoic acid causes the development of feathers in the scale-forming integument of the chick embryo

Summary Injection of retinoic acid (3×62.5 g or 3×125 g) into the amniotic sac of chick embryos between 10 and 12 days of incubation resulted in the formation of club-shaped feathers within the feather tracts, and the development of feathers in the scale-forming areas of the feet. The latter finding is interpreted as caused by a disturbance of the tissue interactions which occur in the skin of the feet at this time.The address for correspondence: Universitè Scientifique et Médicale de Grepoble, Laboratoire de Zoologie et Biologie animale, Boîte Postale n^o 53-Centre de Tri, F-38041 Grenoble Cedex, France