Dear Darwin,—­Many thanks for your new edition of the “Origin,” which I have been too busy to acknowledge before.  I think your answer to Mivart on the initial stages of modification ample and complete, and the comparison of whale and duck most beautiful.  I always saw the fallacy of these objections, of course.  The eye and ear objection you have not so satisfactorily answered, and to me the difficulty exists of how three times over an organ of sight was developed with the apparatus even approximately identical.  Why should not, in one case out of the three, the heat rays or the chemical rays have been utilised for the same purpose, in which case no translucent media would have been required, and yet vision might have been just as perfect?  The fact that the eyes of insects and molluscs are transparent to us shows that the very same limited portion of the rays of the spectrum is utilised for vision by them as by us.

The chances seem to me immense against that having occurred through “fortuitous variation,” as Mivart puts it.

I see still further difficulties on this point but cannot go into them now.  Many thanks for your kind invitation.  I will try and call some day, but I am now very busy trying to make my house habitable by Lady Day, when I must be in it.—­Believe me yours very faithfully,

ALFRED R. WALLACE.

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Down, Beckenham, Kent.  July 27, 1872.

My dear Wallace,—­I have just read with infinite satisfaction your crushing article in Nature.[90] I have been the more glad to see it, as I have not seen the book itself:  I did not order it, as I felt sure from Dr. B.’s former book that he could write nothing of value.  But assuredly I did not suppose that anyone would have written such a mass of inaccuracies and rubbish.  How rich is everything which he says and quotes from Herbert Spencer!

By the way, I suppose that you read H. Spencer’s answer to Martineau:  it struck me as quite wonderfully good, and I felt even more strongly inclined than before to bow in reverence before him.  Nothing has amused me more in your review than Dr. B.’s extraordinary presumption in deciding that such men as Lyell, Owen, H. Spencer, Mivart, Gaudry, etc. etc., are all wrong.  I daresay it would be very delightful to feel such overwhelming confidence in oneself.

I have had a poor time of it of late, rarely having an hour of comfort, except when asleep or immersed in work; and then when that is over I feel dead with fatigue.  I am now correcting my little book on Expression; but it will not be published till November, when of course a copy will be sent to you.  I shall now try whether I can occupy myself without writing anything more on so difficult a subject as Evolution.

I hope you are now comfortably settled in your new house, and have more leisure than you have had for some time.  I have looked out in the papers for any notice about the curatorship of the new Museum, but have seen nothing.  If anything is decided in your favour, I beg you to inform me.—­My dear Wallace, very truly yours,