My dear Huxley

As you seemed somewhat interested about changes in proportions of Pigeons, I will tell you the general results after reworking the whole subject in every possible manner & by the aid of about (more or less) ten thousands rule of three sums.—²

Sternum, scapulæ & furcula invariably reduced in size. Feet & tarsi generally reduced, in size, but are more plainly governed by correlation with length of Beak.—

Wings, measured from end to end of radius, generally reduced in length—viz in 17 Birds (of different races); but in 8 other birds rather increased in length, but then 5 of these 8 are long-beaked birds. But the wings if measured from extreme tip to tip are generally much increased in length—viz in 21 birds longer & in only 5 shorter.—

So that the proportion of birds with longer or shorter wings proportionally with the wild rock-pigeon are reversed, according as the measurement is made from tip to tip of wing or from end to end of radius.—

The increased length of wing, when measured from tip to tip, seems wholly due to greater length of the primary wing feathers, & may not be more related to use & disuse than the quicker or slower growth of nails on our fingers.—

Have you seen last Saturday Review?³ I am very glad of the defence of you & of myself.—   I wish the Reviewer had noticed Hooker.—⁴ The Reviewer, whoever he is, is a jolly good fellow, as this Review & the last on me, showed. He writes capitally & understands well his subject.—   I wish he had slapped Owen a little bit harder⁵

Ever yours | C. Darwin

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