My dear Busk

I thank you cordially. It has been really most kind in you to take so much trouble to explain to me my error.² It is a dreadful, inexcusable blunder, & dearly bought experience shows me how often I blunder. With respect to part of my blunder, viz in confounding the two foramina, Rolleston wrote about a fortnight ago to me pointing it out, so that I have corrected this in the latter 2000 copies, but I could not even notice it in the Errata in the first & larger lot of copies.³

I thought the supra-condyloid foramen was present in the anthropomorpous apes, & I have found the cause of my error. Mivart says it “is only present in the Anthropoidea, in Cebus &c &c, & in almost all the Lemuroidea”.— Now I forgot the sense in which he uses Anthropoidea, & translated it in my own mind as the apes nearest allied to man.⁴ In this case it would, I think, have been a fair inference that the foramen had been occasionally retained or had reappeared by reversion in man. I do not see that this in any way depends on the functional importance of the foramen on natural selection, anymore that the occasional reappearance, for instance, of leg-stripes in the ass.

With respect to the other foramen, which Huxley thought I might call the inter-condyloid,⁵ & to which you allude in your paper Mivart speaks of it as present in Troglodytes & Simia & sometimes in Hylobates, & man & some other monkeys.⁶

So that it appears that the remarks made in my book are fairly applicable in this case. About the Supra-condyloid foramen, I must either strike out the whole passage in any future Edition or qualify it very strongly as the foramen seems very doubtfully related to the structure of Man’s progenitors.⁷

Towards the close of this coming week the new Reprint or new Edit (I do not know which it is be called) will be out, containing a few corrections. Do you possess my book & do you care to have a copy of the Reprint—⁸ It would give me pleasure to send you one.—

Accept my cordial & sincere thanks | Yours very truly | Ch. Darwin

If you care to have a copy send me a card.