“You will see he lays much stress on the difficulty of several remotely allied forms all imitating some one species. Mr. Wallace did not think that there was so much weight in this objection as I do. It is, however, possible that a few species in widely different groups, before they had diverged much, should have accidentally resembled, to a certain extent, some one species. You will also see in this letter a strange speculation, which I should not dare to publish, about the appreciation of certain colours being developed in those species which frequently behold other forms similarly ornamented. I do not feel at all sure that this view is as incredible as it may at first appear. Similar ideas have passed through my mind when considering the dull colours of all the organisms which inhabit dull-coloured regions, such as Patagonia and the Galapagos Is. I suppose you know Mr. Riley’s excellent essay on mimicry in the last report on the noxious insects of Missouri or some such title.
“I hope your work may be in every way successful.
“I remain, dear Sir, yours faithfully,
“Charles Darwin.”
The next letter deals with mimetic resemblance:—
“Mar. 28, 1872.
“Down.
“Dear Sir—I thank you for your information on various subjects. The point to which you allude seems to me very obscure, and I hardly venture to express an opinion on it. My first impression is that the colour of an imitating form might be modified to any extent without any tendency being given to the retention of ancient structural peculiarities. The difficulty of the subject seems to me to follow from our complete ignorance of the causes which have led to the generic differences between the imitating and imitated forms. The subject however seems worth investigating. If the imitator habitually lives in company with the imitated, it would be apt to follow in some respects the same habits of life, and this perhaps would lead to the retention or acquirement of some of the same structural characters.
“I wish you all success in your essay, and remain, dear Sir, yours very faithfully,
“Ch. Darwin.”
The next very brief letter, acknowledging the receipt of a note, was written from Down, March 26th, 1873. It contained some sympathetic remarks upon the progress of Meldola’s work upon Mimicry. In the succeeding letter, printed below, we find a very definite statement of opinion as to the rôle of monstrosities in evolution:—