long wished that some one
would dissect the forms of the male stag-beetle with smaller mandibles,
and see if they were well developed, i.e., whether there was an
abundance of spermatozoa; and the same observations ought, I think,
to be made on the rarer form of your Cicada. Could you not get some
observer, such as Dr. Hartman (453/2. Mr. Walsh sent Mr. Darwin
an extract from Dr. Hartman's "Journal of the doings of a Cicada
septendecim," in which the females are described as flocking round the
drumming males. "Descent of Man" (1901), page 433.), to note whether the
females flocked in equal numbers to the "drumming" of the rarer form as
to the common form? You have a very curious and perplexing subject of
investigation, and I wish you success in your work.

LETTER 454. TO A.R. WALLACE. Down, June 15th [1869?].

You must not suppose from my delay that I have not been much interested
by your long letter. I write now merely to thank you, and just to say
that probably you are right on all the points you touch on, except, as
I think, about sexual selection, which I will not give up. My belief in
it, however, is contingent on my general belief in sexual selection. It
is an awful stretcher to believe that a peacock's tail was thus formed;
but, believing it, I believe in the same principle somewhat modified
applied to man.

LETTER 455. TO G.H.K. THWAITES. Down, February 13th [N.D.]

I wrote a little time ago asking you an odd question about elephants,
and now I am going to ask you an odder. I hope that you will not think
me an intolerable bore. It is most improbable that you could get me
an answer, but I ask on mere chance. Macacus silenus (455/1. Macacus
silenus L., an Indian ape.) has a great mane of hair round neck, and
passing into large whiskers and beard. Now what I want most especially
to know is whether these monkeys, when they fight in confinement (and
I have seen it stated that they are sometimes kept in confinement), are
protected from bites by this mane and beard. Any one who watched them
fighting would, I think, be able to judge on this head. My object is to
find out with various animals how far the mane is of any use, or a mere
ornament. Is the male Macacus silenus furnished with longer hair than
the female about the neck and face? As I said, it is a hundred or a
thousand to one against your finding out any one who has kept these
monkeys in confinement.

LETTER 456. TO F. MULLER. Down, August 28th [1870].