Dear Sir

I am greatly obliged by your note.¹ I have read with much interest & carefully perused your letter in Nature, & am looking out for a paper announced for Linn. Soc.— Your remarks shall all be in due time fully considered.² With respect to the separation of the sexes, I have often reflected on the subject; but there is much difficulty, as it seems to me & as Nägeli has insisted, in as much as a strong case can be made out in favour of the view that with plants at least the sexes were primordially distinct, then became in many cases united, & in not a few cases reseparated.³ I have during the last 5 or 6 years been making a most laborious series of experiments, by which I shall be able, I think, to demonstrate the wonderful good derived from crossing, & I am almost sure but shall not know till the end of the summer that I shall be able to prove that the good is precisely of the same kind which the adult individual derives from slight changes of conditions.—⁴

With very sincere thanks for your interest in my work, I remain | Dear Sir | Yours very faithfully | Ch. Darwin