It may be from multiple origin. The eggs from the Musk and the common duck take an intermediate period in hatching; but I should rather look at it as one of the ten thousand cases which we cannot explain-- namely, when one part or function varies in one species and not in another.
Hooker has told me nothing about his explanation of few Arctic forms; I knew the fact before. I had speculated on what I presume, from what you say, is his explanation (106/3. "Outlines of the Distribution of Arctic Plants," J.D. Hooker, "Trans. Linn. Soc." Volume XXIII., page 251, 1862. [read June 21st, 1860.] In this paper Hooker draws attention to the exceptional character of the Greenland flora; but as regards the paucity of its species and in its much greater resemblance to the floras of Arctic Europe than to those of Arctic America, he considers it difficult to account for these facts, "unless we admit Mr. Darwin's hypotheses" (see "Origin," Edition VI., 1872, Chapter XII., page 330) of a southern migration due to the cold of the glacial period and the subsequent return of the northern types during the succeeding warmer period. Many of the Greenland species, being confined to the peninsula, "would, as it were, be driven into the sea--that is exterminated" (Hooker, op. cit., pages 253- 4).); but there must have been at all times an Arctic region. I found the speculation got too complex, as it seemed to me, to be worth following out.
I have been doing some more interesting work with orchids. Talk of adaptation in woodpeckers (106/4. "Can a more striking instance of adaptation be given than that of a woodpecker for climbing trees and seizing insects in the chinks of the bark?" (Origin of Species," Edition HAVE I., page 141).), some of the orchids beat it.
I showed the case to Elizabeth Wedgwood, and her remark was, "Now you have upset your own book, for you won't persuade me that this could be effected by Natural Selection."
LETTER 107. TO T.H. HUXLEY. July 20th [1860].
Many thanks for your pleasant letter. I agree to every word you say about "Fraser" and the "Quarterly." (107/1. Bishop Wilberforce's review of the "Origin" in the "Quarterly Review," July, 1860, was republished in his "Collected Essays," 1874. See "Life and Letters, II., page 182, and II., page 324, where some quotations from the review are given. For Hopkins' review in "Fraser's Magazine," June, 1860, see "Life and Letters," II., 314.) I have had some really admirable letters from Hopkins. I do not suppose he has ever troubled his head about geographical distribution, classification, morphologies, etc., and it is only those who have that will feel any relief in having some sort of rational explanation of such facts. Is it not grand the way in which the Bishop asserts that all such facts are explained by ideas in God's mind? The "Quarterly" is uncommonly clever; and I chuckled much at the way my grandfather and self are quizzed. I could here and there see Owen's hand. By the way, how comes it that you were not attacked? Does Owen begin to find it more prudent to leave you alone? I would give five shillings to know what tremendous blunder the Bishop made; for I see that a page has been cancelled and a new page gummed in.
I am indeed most thoroughly contented with the progress of opinion. From all that I hear from several quarters, it seems that Oxford did the subject great good. (107/2. An account of the meeting of the British Association at Oxford in 1860 is given in the "Life and Letters," II., page 320, and a fuller account in the one-volume "Life of Charles Darwin," 1892, page 236. See also the "Life and Letters of T.H. Huxley," Volume I., page 179, and the amusing account of the meeting in Mr. Tuckwell's "Reminiscences of Oxford," London, 1900, page 50.) It is of enormous importance the showing the world that a few first-rate men are not afraid of expressing their opinion. I see daily more and more plainly that my unaided book would have done absolutely nothing. Asa Gray is fighting admirably in the United States.