To Henry Denny   28 January [1865]¹

Dear Sir

I thank you very sincerely for your interesting note & answers to my queries.² I am also much obliged for M^r Murray’s paper;³ (returned by this Post) but the interest of this paper to my mind is much enhanced or rather almost wholly depends on a sentence in your note, viz. “Yet the same species of Lice infest the different varieties of Fowl, pigeon & dog.” Now as I understand this, you have never observed distinct varieties of the same species of Pediculus on different domestic varieties.— If, as is probable, I allude to this subject, I sh^d. like to quote on your authority this statement.⁴ But then (though I am ashamed to give so much trouble) I sh^d be glad to know whether you have often looked to the vars. of our domestic mammals & birds. It is not probable, but if you have ever received pediculi from the domesticated animals inhabiting distant lands, or recently brought from such lands & have found them the same, this w^d. add immensely to the value of the statement, I presume you have not attended to the domestic vars. of other animals, besides Fowls, Pigeons & Dogs.⁵ I fear that you will think me very troublesome; pray excuse me & believe me—

Yours very faithfully | Ch. Darwin