pleased I am at what you say on your belief. This part of your letter to
me is a quintessence of richness. The fact about butterflies attracted by
coloured sepals is another good fact, worth its weight in gold. It would
have delighted the heart of old Christian C. Sprengel--now many years in
his grave.

I am glad to hear that you have specially attended to "mimetic" analogies--
a most curious subject; I hope you publish on it. I have for a long time
wished to know whether what Dr. Collingwood asserts is true--that the most
striking cases generally occur between insects inhabiting the same country.


LETTER 124. TO F.W. HUTTON.
Down, April 20th [1861].

I hope that you will permit me to thank you for sending me a copy of your
paper in "The Geologist" (124/1. In a letter to Hooker (April 23rd?, 1861)
Darwin refers to Hutton's review as "very original," and adds that Hutton
is "one of the very few who see that the change of species cannot be
directly proved..." ("Life and Letters," II., page 362). The review
appeared in "The Geologist" (afterwards known as "The Geological Magazine")
for 1861, pages 132-6 and 183-8. A letter on "Difficulties of Darwinism"
is published in the same volume of "The Geologist," page 286.), and at the
same time to express my opinion that you have done the subject a real
service by the highly original, striking, and condensed manner with which
you have put the case. I am actually weary of telling people that I do not
pretend to adduce direct evidence of one species changing into another, but
that I believe that this view in the main is correct, because so many
phenomena can be thus grouped together and explained. But it is generally
of no use; I cannot make persons see this. I generally throw in their