Studies on the development of feathers have as yet provided only inadequate answers to many fundamental problems. The evolution of feathers themselves and their relation to reptilian scales are still matters of hypothesis, and will remain so until more crucial information is forthcoming. Again, the phylogenetic sequence of events relating embryonic to definitive feathers is inconclusive, and it cannot be said with certainty whether the embryonic down feather is a secondary modification of the ordinary contour feather, or whether the latter has been evolved from a primitive down-like primary feather. Investigations upon the development of epidermal structures in general, and of feathers in particular, were favoured by workers in Germany during the last century, culminating in the classical work of Davies (1889) on the development of feathers in the pigeon. His views still form the accepted basis for work on plumage, but recent knowledge has necessitated a re-examination of them. (Lillie and Juhn, 1932.)