Forgive me for writing at such length, and believe me yours very sincerely,
CH. DARWIN.
P.S.—I am very sorry that you have given up sexual selection. I am not at all shaken, and stick to my colours like a true Briton. When I think about the unadorned head of the Argus pheasant, I might exclaim, Et tu, Brute!
Down, Beckenham. June 25, 1876.
My dear Wallace,—I have been able to read rather more quickly of late and have finished your book. I have not much to say. Your careful account of the temperate parts of South America interested me much, and all the more from knowing something of the country. I like also much the general remarks towards the end of the volume on the land molluscs. Now for a few criticisms.
P. 122:[108] I am surprised at your saying that "during the whole Tertiary period North America was zoologically far more strongly contrasted with South America than it is now." But we know hardly anything of the latter except during the Pliocene period, and then the mastodon, horse, several great Dentata, etc. etc., were common to the North and South. If you are right I erred greatly in [pg 293]my Journal, where I insisted on the former close connection between the two.
P. 252, and elsewhere: I agree thoroughly with the general principle that a great area with many competing forms is necessary for much and high development; but do you not extend this principle too far—I should say much too far, considering how often several species of the same genus have been developed on very small islands?
P. 265: You say that the Sittidæ extend to Madagascar, but there is no number in the tabular heading.[109]
P. 359: Rhinochetus is entered in the tabular heading under No. 3 of the Neotropical sub-regions.[110]