for though these latter variations will always be dominants, yet many
dominant characteristics may arise from another cause, namely the
meeting of complementary factors, and special study of each case in
two generations at least is needed before these two phenomena can be
distinguished.

When such considerations are fully appreciated it will be realised
that medleys of most dissimilar occurrences are all confused together
under the term Variation. One of the first objects of genetic analysis
is to disentangle this mass of confusion.

To those who have made no study of heredity it sometimes appears that
the question of the effect of conditions in causing variation is one
which we should immediately investigate, but a little thought will
show that before any critical inquiry into such possibilities can be
attempted, a knowledge of the working of heredity under conditions as
far as possible uniform must be obtained. At the time when Darwin was
writing, if a plant brought into cultivation gave off an albino
variety, such an event was without hesitation ascribed to the change
of life. Now we see that albino _gametes_, germs, that is to say,
which are destitute of the pigment-forming factor, may have been
originally produced by individuals standing an indefinite number of
generations back in the ancestry of the actual albino, and it is
indeed almost certain that the variation to which the appearance of
the albino is due cannot have taken place in a generation later than
that of the grandparents. It is true that when a new _dominant_
appears we should feel greater confidence that we were witnessing the
original variation, but such events are of extreme rarity, and no such
case has come under the notice of an experimenter in modern times, as
far as I am aware. That they must have appeared is clear enough.
Nothing corresponding to the Brown-breasted Game fowl is known wild,
yet that colour is a most definite dominant, and at some moment since
_Gallus bankiva_ was domesticated, the element on which that special
colour depends must have at least once been formed in the germ-cell of
a fowl; but we need harder evidence than any which has yet been
produced before we can declare that this novelty came through
over-feeding, or change of climate, or any other disturbance
consequent on domestication. When we reflect on the intricacies of
genetic problems as we must now conceive them there come moments when
we feel almost thankful that