stocks, and that it is easier to believe that a given race was derived from some ancestor of which all trace has been lost than that all races of fowls, for example, arose by variation from a single species, but the evidence that our varieties of pigeons have been derived from _C. livia_, and of fowls from _G. bankiva_, is too strong to be disregarded because it does not agree with theoretical conceptions. My own experiments in crossing Silky fowls with _Gallus bankiva_ (_P.Z.S._, 1919) show that the recessive is not always pure, that segregation is not in all cases complete. The colour of the _bankiva_ is what is called black-red, these being probably the actual pigments present, mixed in some parts of the plumage, in separate areas in other parts: the Silky is white. There are seven pairs of characters altogether in which the Silky differs from the _bankiva_. Both the pigmented skin of the Silky and the colour in the plumage of the _bankiva_ are dominant, so that all the offspring in _F1_ or the first generation are coloured fowls with pigmented skins. But in later generations I found that with regard to skin pigment there were no pure recessives. Since the heterozygote in _F1_ was deeply pigmented, it is certain that a bird with only a small amount of pigment in its skin was a recessive resulting from incomplete segregation of the pigmented character. The pigment occurred chiefly in the skin of the abdomen and round the eyes, and also in the peritoneum and in the connective tissue of the abdominal wall. It varied in different individuals, but in some, at any rate, was greater in later generations than in the earlier. The condition bred true, as pure recessives do; and when such an impure recessive was mated with a heterozygote with black skin, the offspring were half pigmented and half recessive, with some pigment on the abdomen of the latter. Still more striking was the incomplete segregation in the plumage colour. The white of the Silky was recessive, all the birds of the _F1_ generation being fully coloured. In the _F2_ generation there were two recessive white cocks which when mature showed slight yellow colour across the loins. These two were mated with coloured hens, and in later generations all the recessives instead of being pure white, like the Silky, had reddish-brown pigment distributed as in pile fowls. [Illustration: PLATE I. Recessive Pile Fowls] In the hens (Plate I., fig. 1) it was chiefly confined to the breast and abdomen, and was well developed, not a mere tinge or trace, but a deep coloration, extending on to the dorsal coverts at the lower edge of the folded wings. The back and tail were white. In the cocks the colour was much paler, and extended over the dorsal surface of the wings, where it was darker than on the back and loins (Plate I., fig. 2). These pile-coloured fowls when mated together bred true, with individual differences in the offspring.