Pigmented and "white" hybrid embryos. They are the unhatched progeny of the cross between a B/B female Coturnix and a Bl/+ male Gallus with a "blue" plumage. The embryo on the left shows greyish feathers, and the embryo on the right has apparently only whitish feathers, the only two plumage colours that would be expected in +/B and Bl/B hybrids if blue and silver were allelic mutations.
Minvielle et al. BMC Genetics 2010 11:15 doi:10.1186/1471-2156-11-15