of infertility co-operate, and I really think I have overcome the
fundamental difficulties of the question and made it a good deal clearer
than Darwin left it.... I think also it completely smashes up
Romanes.--Yours faithfully,

ALFRED R. WALLACE.

* * * * *

The next letter relates to a question which Prof. Meldola raised as to
whether, in view of the extreme importance of "divergence" (in the
Darwinian sense) for the separation and maintenance of specific types,
it might not be possible that sterility, when of advantage as a check to
crossing, had in itself, as a physiological character, been brought
about by Natural Selection, just as extreme fecundity had been brought
about (by Natural Selection) in cases where such fecundity was of
advantage.

TO PROF. MELDOLA


_Frith Hill, Godalming. April 12, 1888._

My dear Meldola,--Many thanks for your criticism. It is a perfectly
sound one as against my view being a _complete explanation_ of the
phenomena, but that I do not claim. And I do not see any chance of the
required facts being forthcoming for many years to come. Experiments in
the hybridisation of animals are so difficult and tedious that even
Darwin never undertook any, and the only people who could and ought to
have done it--the Zoological Society--will not. There is one point,