I hope that the world goes well with you. Do not trouble yourself by acknowledging this.--Ever yours, CH. DARWIN. Accompanying this letter, which has been published in "Darwin and Modern Science" (1909), was a photograph of the chrysalis (_Papilio sarpedon choredon_) attached to a leaf of its food-plant. Many butterfly pupæ are known to have the power of individual adjustment to the colours of the particular food-plant or other normal environment; and it is probable that the Australian _Papilio_ referred to by Darwin possesses this power. * * * * * _Nutwood Cottage, Frith Hill, Godalming, July 9, 1881._ My dear Darwin,--I am just doing, what I have rarely if ever done before--reading a book through a second time immediately after the first perusal. I do not think I have ever been so attracted by a book, with perhaps the exception of your "Origin of Species" and Spencer's "First Principles" and "Social Statics." I wish therefore to call your attention to it, in case you care about books on social and political subjects, but here there is also an elaborate discussion of Malthus's "Principles of Population," to which both you and I have acknowledged ourselves indebted. The present writer, Mr. George, while admitting the main principle as self-evident and as actually operating in the case of animals and plants, denies that it ever has operated or can operate in the case of man, still less that it has any bearing whatever on the vast social and political questions which have been supported by a reference to it. He illustrates and supports his views with a wealth of illustrative facts and a cogency of argument which I have rarely seen equalled, while his style is equal to that of Buckle, and thus his book is delightful reading. The title of the book is "Progress and Poverty." It has gone through six editions in America, and is now published in England by Kegan Paul. It is devoted mainly to a brilliant discussion and refutation of some of the most widely accepted maxims of political economy, such as the relation of wages and capital, the nature of rent and interest, the laws of distribution, etc., but all treated as parts of the main problem as stated in the title-page, "An Enquiry into the Cause of Industrial Depressions and of Increase of Want with Increase of Wealth." It is the most startling novel and original book of the last twenty years, and if I mistake not will in the future rank as making an advance in political and social science equal to that made by Adam Smith a century ago. I am here settled in my little cottage engaged in the occupation I most enjoy--making a garden, and admiring the infinite variety and beauty of vegetable life. I am out of doors all day and hardly read anything. As the long evenings come on I shall get on with my book on the "Land Question," in which I have found a powerful ally in Mr. George. Hoping you are well, believe me, yours most faithfully, ALFRED R. WALLACE.