cross, or that it was due to the meeting of complementary factors. In
medical literature, however, there are numerous records of the spontaneous
origin of various abnormalities which behave as dominants, such as
brachydactyly, and Bateson considers the authenticity of some of these to
be beyond doubt. He concludes that it is impossible in the present state
of knowledge to offer any explanation of the origin of dominant
characters. In a note, however, he suggests the possibility that there are
no such things as new dominants. Factors have been discovered which simply
inhibit or prevent the development of other characters. For example, the
white of the plumage in the White Leghorn fowl is due to an inhibiting
factor which prevents the development of the colour factor which is also
present. Withdraw the dominant inhibiting factor, and the colour shows
itself. This is shown by crossing the dominant white with a recessive
white, when some birds of the F(2) generation are coloured.[Footnote:
Bateson, _Principles of Heredity_, p. 104.] Similarly, brachydactyly in
man may be due to the loss of an inhibiting factor which prevents it
appearing in normal persons. It is evident, however, that it is difficult
to apply this suggestion to all cases. For example, the White Leghorn fowl
must have descended from a coloured form, probably from the wild species
_Gallus bankiva_. If Bateson's suggestion were valid we should have to
suppose that the loss of the factor for colour caused the dominant white
to appear, and then when this is withdrawn colour appears again, so that
the colour factors and the inhibiting factors must lie over one another in
a kind of stratified alternation. And then how should we account for the
recessive white?

In his Presidential Address to the meeting of the British Association in
Australia, 1914, Bateson explains his suggestion somewhat more fully with
a command of language which is scarcely less remarkable than the subject
matter. The more true-breeding forms are studied the more difficult it is