ecies, but in all the great
problems of biology a new era began. So unexpected was the discovery
that many naturalists were convinced it was untrue, and at once
proclaimed Mendel's conclusions as either altogether mistaken, or if
true, of very limited application. Many fantastic notions about the
workings of Heredity had been asserted as general principles before:
this was probably only another fancy of the same class.

Nevertheless those who had a preliminary acquaintance with the facts
of Variation were not wholly unprepared for some such revelation. The
essential deduction from the discovery of segregation was that the
characters of living things are dependent on the presence of definite
elements or factors, which are treated as units in the processes of
Heredity. These factors can thus be recombined in various ways. They act
sometimes separately, and sometimes they interact in conjunction 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 living 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 thes