Dear Sir

Your criticisms are profoundly interesting to me.² A downright good objection or difficulty is very nearly as interesting as a favourable fact.— Your Review always struck me as very able (though I am not now quite so much shaken by some remarks as I was at first)³ & I have given some few of your objections in a new German edition.⁴ Very sincere thanks for the Pelargonium leaves.⁵ I sh^d. certainly rank this as a case of true correlation; because the parts are homologous & it seems to me inherently probable that parts, which are quite alike in an early stage of development on the same individual would be apt to be similarly affected by the unknown causes of variation. If you will look at my discussion in Ch. V. Origin (p. 162–164 3^d. Edit) you will see that I expressly guard against the assumption that parts going together throughout whole classes are necessarily correlated.⁶ But I now see that I ought more plainly to have said that “correlation of growth” contains a most heterogenious set of facts.⁷ If you had asked me yesterday about hair & sexes, I sh^d. have said that it was only a case correlation so far as that the Hairy character had become attached to the male sex, in the same accidental (to speak loosely) manner in which large wattles have become correlated with male Carrier pigeons.— But your remarks show me that there is something more. I sh^d. hardly have said that the ox was quite like a cow; or an old woman like a man; but I think I have read of female birds quite like males in their plumage, & the case seems very strange & inexplicable. I must remember & attend to this; but the subject is far too large for me.—⁸ I cannot help looking confidently to all vertebrata as having descended from an Hermaphrodite form; (though only one hermaphrodite genus still exists) & that males & in lesser degree females have acquired new characters in “correlation” (to use my favourite term) or in “accidental correlation” with sex.⁹ But a man must be a fool to hope even to conjecture (supposing for the moment that my views are in the main correct) how all the wondrous changes have been effected. I had not forgotten your good case of coadapted structure at or before birth.¹⁰ I do not quite see necessity of such close simultaneous development as you do. Some Young fish are born with bag of yolk, & this might last long till milk was secreted. Those young Batrachians which are hatched in a quasi marsupial pouch on mothers back are believed to feed on mucus secreted by whole surface; concentration of glands would make a mamma, & in the Ornithorhynchus (marsupial order) the mammary glands are still diffused. But this is all conjectural rubbish. Pray however (I must add) reflect on the quasi-placenta in cartilaginous fishes.

I have lately published a small Book on Orchids (small portions of which alone bear on the general question of Species) parts of which I think would interest you. I cannot conceive how I forgot your name when I made out a list of copies to send away.—¹¹ As I hope you will permit me to send you a copy, I will today write to my publisher.—¹² I sh^d. be much pleased, if any criticisms occur to you, to hear them, or read them if ever you review semi-botanical works.—

I assure you that I feel most sincerely grateful for your remarks & for the very kind manner in which you make them.—

Pray believe me | My dear Sir | Yours sincerely | C. Darwin