[Analysis comparing pigmentation of silkies, brown leghorns and their hybrids].

Silkies differ from Brown Leghorns not only in their plumage but also in the pigmentation of their connective tissue. The Silky fowl has intensely pigmented tissue in contrast to the Brown Leghorn. The pigmentation of the connective tissue depends on a sex-linked pair of genes (Dd) as well as a pair of genes with an intermediary effect (Pp). As the effect of those gens turns out to be only quantitative the melanocytes can be evaluated in the connected tissue of the embryos of Silkies, Brown Leghorns and the reciprocal hybrids. The result is an exact description of position and distribution of the melanocytes in the tissue.All the hybrids of Silkies and Brown Leghorns have less pigment than the Silkies, but more than the Brown Leghorns. The male hybrids (PpDd) are pigmented intermediary, whereas the female hybrids have a more (Ppd-) or less (PpD-) intense pigmentation in the internal parts of their body. Up to the 7th embryonic day extension and differentiation of the pigment cells are similar in all the breeds. The hybrids (PpD- and PpDd), however, have fewer pigment cells than the Silky fowl from the beginning.During the 8th or 9th embryonic day a distinct process of degeneration of melanocytes is developing in the Brown Leghorns and the PpD-hybrids. This process, however, cannot be observed in the Silky fowl and the hybrids with the gen combination Dd, dd, d-. This degeneration of melanocytes is caused by the gen D becoming effective rather later and being not or slightly dominant over its allel d.The periodic deviation in the process of melanocytes differentiation depends on the growth rate of the embryos. The maxima of the melanocytes differentiation correspond to the period of a minimum growth.