62. See also
"Descent of Man", page 261.) Darwin also admitted the justice of
Professor E.S. Morse's contention that the shells of molluscs are often
adaptively coloured. ("More Letters", II. page 95.) But he looked
upon cryptic colouring and also mimicry as more especially Wallace's
departments, and sent to him and to Professor Meldola observations and
notes bearing upon these subjects. Thus the following letter given to me
by Dr A.R. Wallace and now, by kind permission, published for the first
time, accompanied a photograph of the chrysalis of Papilio sarpedon
choredon, Feld., suspended from a leaf of its food-plant:

July 9th, Down, Beckenham, Kent.

My Dear Wallace,

Dr G. Krefft has sent me the enclosed from Sydney. A nurseryman saw a
caterpillar feeding on a plant and covered the whole up, but when he
searched for the cocoon (pupa), was long before he could find it, so
good was its imitation in colour and form to the leaf to which it was
attached. I hope that the world goes well with you. Do not trouble
yourself by acknowledging this.

Ever yours

Ch. Darwin.

Another deeply interesting letter of Darwin's bearing upon protective
resemblance, has only recently been shown to me by my friend Professor
E.B. Wilson, the great American Cytologist. With his kind consent and
that of Mr Francis Darwin, this letter, written four months before
Darwin's death on April 19, 1882, is reproduced here (The letter is
addressed: "Edmund B. Wilson, Esq., Assistant in Biology, John Hopkins
University, Baltimore Md, U. States."):

December 21, 1881.

Dear Sir,

I thank you much for having taken so much trouble in describing fully
your interesting and curious case of mimickry.

I am in the habit of looking through many scientific Journals, and
though my memory is now not nearly so good as it was, I feel pretty sure
that no such case as yours has been described (amongst the nudibranch)
molluscs. You perhaps know the case of a fish allied to Hippocampus,
(described some years ago by Dr Gunther in "Proc. Zoolog. Socy.") which
clings by its tail to sea-weeds, and is covered with waving filaments
so as itself to look like a piece of the same sea-weed. The parallelism
between your and Dr Gunther's case makes both of them the more
interesting; considering how far a fish and a mollusc stand apart. It
would be difficult for anyone to explain such cases by the direct
action of the environment.--I am glad that you intend to make fur