the other free, the suppressed character appears. This is the principle
proposed to get over the difficulty of the origin of a new dominant. All
characters are due to factors, and all factors were present in the
original ancestor--say Amoeba. Evolution has been merely 'the rejection of
various factors from an original complex, and a reshuffling of those that
were left.' Professor Lotsy goes so far as to say that difference in
species arose solely from crossing, that all domestic animals are of mixed
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