h 13th, 1871.

(458/1. We are indebted to Mr. Murdoch for a draft of his letter dated
March 10th, 1871. It is too long to be quoted at length; the following
citations give some idea of its contents: "In your 'Descent of Man,' in
treating of the external differences between males and females of the
same variety, have you attached sufficient importance to the different
amount and kind of energy expended by them in reproduction?" Mr. Murdoch
sums up: "Is it wrong, then, to suppose that extra growth, complicated
structure, and activity in one sex exist as escape-valves for surplus
vigour, rather than to please or fight with, though they may serve these
purposes and be modified by them?")

I am much obliged for your valuable letter. I am strongly inclined to
think that I have made a great and complete oversight with respect to
the subject which you discuss. I am the more surprised at this, as I
remember reflecting on some points which ought to have led me to your
conclusion. By an odd chance I received the day before yesterday a
letter from Mr. Lowne (author of an excellent book on the anatomy of
the Blow-fly) (458/2. "The Anatomy and Physiology of the Blow-fly (Musca
vomitaria L.)," by B.T. Lowne. London, 1870.) with a discussion very
nearly to the same effect as yours. His conclusions were drawn from
studying male insects with great horns, mandibles, etc. He informs me
that his paper on this subject will soon be published in the "Transact.
Entomolog. Society." (458/3. "Observations on Immature Sexuality and
Alternate Generation in Insects." By B.T. Lowne. "Trans. Entomolog.
Soc." 1871 [Read March 6th, 1871]. "I believe that certain cutaneous
appendages, as the gigantic mandibles and thoracic horns of many males,
are complemental to the sexual organs; that, in point of fact, they are
produced by the excess of nutriment in the male, which in the female
would go to form the generative organs and ova" (loc. cit., page 197).)
I am inclined to look at your and Mr. Lowne's view as specially valuable
from probably throwing light on the greater variability of male than
female animals, which manifestly has much bearing on sexual selection.
I will keep your remarks in mind whenever a new edition of my book is
demanded.

LETTER 459. TO GEORGE FRASER.

(459/1. The following letter refers to two letters to Mr. Darwin, in
which Mr. Fraser pointed out that illustrations of the theory of Sexual
Selection might be found amongst Britis