inct factor after hybridization.
Ancestry alone furnishes the material for the factor, and no amount of
induced change can get itself registered in the organism so as to come
into this charmed circle of ancestral characters which alone seem to be
passed on to posterity.

A quotation from Bateson ought to set this point at rest:

"The essence of the Mendelian principle is very easily expressed. It is,
first, that in great measure the properties of organisms are due to the
presence of distinct, detachable elements [factors], separately
transmitted in heredity; and secondly, that _the parent cannot pass on
to offspring an element, and consequently the corresponding property,
which it does not itself possess_."[28]

[Footnote 28: _Scientific American_ Sup., January 3, 1914.]

Heredity we now see is a method of analysis, and the facts brought to
light by Mendelism help us very much toward an understanding of living
matter. Especially does it help us to understand the complexity
underlying the facts of heredity, which until now have seemed so strange
and capricious. As Professor Punnett of Cambridge remarks:

"Constitutional differences of a radical nature may be concealed beneath
an apparent identity of external form. Purple sweet peas from the same
pod, indistinguishable in appearance and of identical ancestry, may yet
be fundamentally different in their constitution. From one may come
purples, reds, and whites; from another only purples and reds; from
another purples and whites alone; whilst a fourth will breed true to
purple. Any method of investigation which fails to take account of the
radical differences of constitution which may underlie external
similarity, must necessarily be doomed to failure. Conversely, we
realize to-day that individuals identical in constitution may yet have
an entirely different ancestral history. From the cross between two
fowls with rose and pea combs, each of irreproachable pedigree for
generations, come single combs in the second generation, _and these
singles are precisely similar in their behavior to singles bred from
strains of unblemished ancestry_. In the ancestry of the one is to be
found no single over a long series of years; in the ancestry of the
other nothing but singles occurred. The creature of given constitution
may often be built up in many ways, but once formed it will behave like
others of the same constitution."[29]

[Footnote 29: Encyclopaedia Britannica, Vol. XVIII,