I really have no criticism to make. (148/2. Mr. Bates' paper on mimetic butterflies was read before the Linnean Society, November 21st, 1861, and published in the "Linn. Soc. Trans." XXIII., 1862, page 495, under the title of "Contributions to an Insect Fauna of the Amazon Valley.") Style seems to me very good and clear; but I much regret that in the title or opening passage you did not blow a loud trumpet about what you were going to show. Perhaps the paper would have been better more divided into sections with headings. Perhaps you might have given somewhere rather more of a summary on the progress of segregation of varieties, and not referred your readers to the descriptive part, excepting such readers as wanted minute detail. But these are trifles: I consider your paper as a most admirable production in every way. Whenever I come to variation under natural conditions (my head for months has been exclusively occupied with domestic varieties), I shall have to study and re-study your paper, and no doubt shall then have to plague you with questions. I am heartily glad to hear that you are well. I have been compelled to write in a hurry; so excuse me.

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