long ago that the pile could be produced from a female of the black-red
Game mated with a white Game-cock. It would seem, therefore, that the pile
is the heterozygote of black-red and 'dominant' white. Bateson, however
(_Principles of Heredity_, 1909, p. 120), writes that the whole problem of
the pile is very obscure, and treats it as a case of peculiarity in the
genetics of yellow pigments. On p. 102 of the same volume he describes the
results of crossing White Leghorn with Indian Game or Brown Leghorn, the
_F1_ being substantially white birds with specks of black and brown,
though cocks have sometimes enough red in the wings to bring them into
the category known an pile. To test the matter I have crossed White
Leghorns with a pure-bred black-red Game-cock, and in the offspring out of
eight six were fairly good piles, but with not quite so much red on the
back as in typical birds: one was a pile with yellow on the back instead
of red, and one was white with irregular specks. Of the hens, four were of
pile coloration with breast and abdomen of uniform reddish-brown colour,
back, neck, and saddle hackles laced with pale brown, tail white. The
other four were white with black and brown specks. Whether these pile
heterozygotes will breed true I do not yet know.

These results tend to show that factors are not indivisible units, and
segregation is rather the difficulty of chromatin or germ plasm from
different race uniting together. It must be remembered that the fertilised
ovum which forms one individual gives rise also to dozens or hundreds or
thousands or millions of gametes. If a given character is represented by a
portion of the chromatin in the original ovum, this has to be divided so
many times, and each time to grow to the same condition as before. How can
we suppose that the divisions shall be exactly equal or the growth always
the same? It is inevitable that irregularities will occur, and if the
original chromatin produced a certain character, who shall say what more
or less of that chromatin will produce?