it is concluded that it has not been really divided, but consists of two
or three units (Castle). Further, although Mendelism in itself shows no
evidence of the origin of the characters, it assumes that they arose as
complete units, and one suggestion is that a dominant factor might at some
of the divisions in gametegenesis pass entirely into one daughter cell,
and therefore be absent from the other, and thus individuals might be
developed in which a dominant character was absent. Bateson in his
well-known books, _Mendel's _Principles of Heredity_, 1909, and _Problems
of Genetics_, 1913, discusses this question of the origin of the factors
which are inherited independently. The difficulty that troubles him is the
origin of a dominant character. Naturally, if he persists in regarding the
determinant factor as a unit which does not grow nor itself evolve in any
way, it is difficult to conceive where it came from. The dominant,
according to Bateson, must be due to the presence of something which is
absent in the recessive. He gives as an instance the black pigment in the
Silky fowl, which is present in the skin and connective tissues. In his
own experiments he found this was recessive to the white-skin character of
the Brown Leghorn, and he assumes that the genetic properties of _Gallus
bankiva_ with regard to skin pigment are similar to those of the Brown
Leghorn. Therefore in order that this character could have arisen in the
Silky, the pigment-producing factor _P_ must be added and the inhibiting
factor _D_ must drop out or be lost. He says we have no conception of the
process by which these events took place. [Footnote: _Problems of
Genetics_, p. 85.] Now my experiment in crossing Silky with _bankiva_
shows that no inhibiting factor is present in the latter, so that only one
change, not two, was necessary to produce the Silky. Mendelians find it
so difficult to conceive of the origin of a new dominant that they even
suggest that no such thing ever occurs: what appears as a new character
was present from the beginning, but its development was prevented by an
inhibiting factor: when this goes into one cell of a division and leaves