of how each of two forms of female produces offspring like the other
female as well as like itself, but no intermediates?

If you "know varieties that will not blend or intermix, but produce
offspring quite like either parents," is not that the very physiological
test of a species which is wanting for the _complete proof_ of the
origin of species?

I have by no means given up the idea of writing my Travels, but I think
I shall be able to do it better for the delay, as I can introduce
chapters giving popular sketches of the subjects treated of in my
various papers.

I hope, if things go as I wish this summer, to begin work at it next
winter. But I feel myself incorrigibly lazy, and have no such system of
collecting and arranging facts or of making the most of my materials as
you and many of our hard-working naturalists possess in
perfection.--With best wishes, believe me, dear Darwin, yours most
sincerely,

ALFRED R. WALLACE.

* * * * *

_Down, Bromley, S.E. Tuesday, February, 1866._

My dear Wallace,--After I had dispatched my last note, the simple
explanation which you give had occurred to me, and seems satisfactory. I
do not think you understand what I mean by the non-blending of certain
varieties. It does not refer to fertility. An instance will explain. I
crossed the Painted Lady and Purple sweet peas, which are very
differently coloured varieties, and got, even out of the same pod, both
varieties perfect, but none intermediate. Something of this kind, I
should think, must occur at first with your butterflies and the three
forms of Lythrum; though these cases are in appearance so wonderful, I
do not know that they are really more so than every female in the world
producing distinct male and female offspring.

I am heartily glad that you mean to go on preparing your
Journal.--Believe me yours very sincerely,

CH. DARWIN.

* * * * *

_Hurstpierpoint, Sussex. July 2, 1866._

My dear Darwin,--I have been so repeatedly struck by the utter inability
of numbers of intelligent persons to see clearly, or at all, the
self-acting and necessary effects of Natural Selection, that I am led to
conclude that the term itself, and your mode of illustrating it, however
clear and beautiful to many of us, are yet not the best adapted to
impress it on the general naturalist public. The two last cases of this
misunderstanding are (1) the article on "Darwin and