nce of many useless organs, and (2)
the continuous development of secondary sexual characters beyond any
conceivable utility, and, apparently, till checked by inutility. It
explains both these. Disuse alone, as I and many others have always
argued, cannot do the first, but can only cause _regression to the
mean_, with perhaps some further regression from economy of material.

As to the second, I have always felt the difficulty of accounting for
the enormous development of the peacock's train, the bird of paradise
plumes, the long wattle of the bell bird, the enormous tail-feathers of
the Guatemalan trogon, of some humming-birds, etc. etc. etc. The
beginnings of all these I can explain as recognition marks, and this
explains also their distinctive character in allied species, but it does
not explain their growing on and on far beyond what is needful for
recognition, and apparently till limited by absolute hurtfulness. It is
a relief to me to have "germinal selection" to explain this.

I do not, however, think it at all necessary to explain adaptations,
however complex. Variation is so general and so large, in dominant
species, and selection is so tremendously powerful, that I believe all
needful adaptation may be produced without it. But, if it exists, it
would undoubtedly hasten the process of such adaptation and would
therefore enable new places in the economy of nature to be more rapidly
filled up.

I was thinking of writing a popular exposition of the new theory for
_Nature_, but have not yet found time or inclination for it. I began
reading "Germinal Selection" with a prejudice against it. That prejudice
continued through the first half, but when I came to the idea itself,
and after some trouble grasped the meaning and bearing of it, I saw the
work it would do and was a convert at once. It really has no relation to
Lamarckism, and leaves the non-heredity of acquired characters exactly
where it was.--Yours very truly,

ALFRED R. WALLACE.

* * * * *

The next letter relates to the great controversy then being carried on
with respect to Weismann's doctrine of the non-inheritance of "acquired"
characters, which doctrine implied complete rejection of the last trace
of Lamarckism from Darwinian evolution. Wallace ultimately accepted the
Weismannian teaching. Darwin had no opportunity during his lifetime of
considering this question, which was raised later in an acute form by
Weismann.