ocesses of
Heredity. These factors can thus be recombined in various ways. They
act sometimes separately, and sometimes they interact in conduction
with each other, producing their various effects. All this indicates a
definiteness and specific order in heredity, and therefore in
variation. This order cannot by the nature of the case be dependent on
Natural Selection for its existence, but must be a consequence of the
fundamental chemical and physical nature of living things. The study
of Variation had from the first shown that an orderliness of this kind
was present. The bodies and the properties of livings things are
cosmic, not chaotic. No matter how low in the scale we go, never do we
find the slightest hint of a diminution in that all-pervading
orderliness, nor can we conceive an organism existing for a moment in
any other state. Moreover not only does this order prevail in normal
forms, but again and again it is to be seen in newly-sprung varieties,
which by general consent cannot have been subjected to a prolonged
Selection. The discovery of Mendelian elements admirably coincided
with and at once gave a rationale of these facts. Genetic Variation is
then primarily the consequence of additions to, or omissions from, the
stock of elements which the species contains. The further
investigation of the species-problem must thus proceed by the
analytical method which breeding experiments provide.

In the nine years which have elapsed since Mendel's clue became
generally known, progress has been rapid. We now understand the
process by which a polymorphic race maintains its polymorphism. When a
family consists of dissimilar members, given the numerical proportions
in which these members are occurring, we can represent their
composition symbolically and state what types can be transmitted by
the various members. The difficulty of the "swamping effects of
inter-crossing" is practically at an end. Even the famous puzzle of
sex-limited inheritance is solved, at all events in its more regular
manifestations, and we know now how it is brought about that the
normal sisters of a colour-blind man can transmit the colour-blindness
while his normal brothers cannot transmit it.

We are still only on the fringe of the inquiry. It can be seen
extending and ramifying in many directions. To enumerate these here
would be impossible. A whole new range of possibilities is being
brought into view by study of the inter-relations between the