not to be had. We must, I think,
leave the case in the hands of others, and I am in hopes that my paper
may call sufficient attention to the subject to induce some of the great
school of Darwinians to take the question up and work it out thoroughly.
You have brought such a mass of facts to support your view, and have
argued it so fully, that I hardly think it necessary for you to do more.
Truth will prevail, as you as well as I wish it to do. I will only make
one or two remarks. The word "voluntary" was inserted in _my proofs
only_, in order to distinguish clearly between the two radically
distinct kinds of "sexual selection." Perhaps "conscious" would be a
better word, to which I think you will not object, and I will alter it
when I republish. I lay no stress on the word "voluntary."

Sound- and scent-producing organs in males are surely due to "natural"
or "automatic" as opposed to "conscious" selection. If there were
gradations in the sounds produced, from mere noises, up to elaborate
music--the case would be analogous to that of "colours" and "ornament."
Being, however, comparatively simple, Natural Selection, owing to their
use as a guide, seems sufficient. The louder sound, heard at a greater
distance, would attract or be heard by more females, or it may attract
other males and lead to combats _for_ the females, but this would not
imply _choice_ in the sense of rejecting a male whose stridulation was a
trifle less loud than another's, which is the essence of the theory as
applied by you to colour and ornament. But greater general vigour would
almost certainly lead to greater volume or persistence of sound, and so
the same view will apply to both cases on my theory.

Thanks for the references you give me. My ignorance of German prevents
me supporting my views by the mass of observations continually being
made abroad, so I can only advance my own ideas for what they are worth.

I like Dorking much, but can find no house to suit me, so fear I shall
have to move again.

With best wishes, believe me yours very faithfully,

ALFRED R. WALLACE.

* * * * *

_Down, Beckenham, Kent. September 5, [1877]._

My dear Wallace,--"Conscious" seems to me much better than "voluntary."
Conscious action, I presume, comes into play when two males fight for a
female; but I do not know whether you admit that, for instance, the
spur of the cock is due to sexual selection.

I am quite willing to admi