To George Henry Kendrick Thwaites   8 March 1856

My dear Sir

Though I have nothing very particular to say I must thank you cordially for the extremely kind manner with which you have received my letter.¹ I remember at Oxford that you had attended to many of the points on which I was then & am now so much interested.² I hope that you will publish some of the facts on variation to which you allude: I sh^d. be particularly glad to see in print or M.S. some particulars in regard to the species from different elevations, which show different degrees of capacity for cultivation at a new level: Hooker has published a similar case in regard to the Himmalaya Rhododendrums.³

As you have received my letter in so very friendly a spirit, I will mention one or two other points on which I am much interested; viz in regard to the distribution of alpine plants; have you collected at the greater heights in Ceylon, & is there anything new in relation to the vegetation at these heights in comparison with the Himmalaya, Neilgherries or other mountains? Again have you observed whether the introduced & perfectly naturalised plants tend to vary much in Ceylon? The courrse of my work makes me more & more sceptical on the eternal immutability of species; yet the difficulties on the other theory of common descent seem to me frightfully great. In my work, which I shall not publish for 2 or 3 or perhaps more years; it is my intention to give, as far as I can & that will be very imperfectly, all the arguments & facts on both sides of the case, stating which side seems to me to preponderate.—

You cannot possibly render me more material assistance than by getting me any skins of Indian or Ceylon (or any breed except English) breeds of Pigeons;⁴ for I have concluded it would be better to work carefully at the varieties of a few animals, than compile brief notices on all our domestic animals. I have now all English breeds of Pigeons alive, & am carefully observing them, making skeletons & crossing them. There are some remarkable Tumblers in India.—⁵ Have you any domestic Ducks? or Rabbits These I mean to work at, as well as at Poultry. Any skeleton of Ducks w^d. be very valuable.— D^r. Kellaart has offered to help me in regard to Poultry, for I met him accidentally at Brit. Museum, after writing to you;⁶ but I do not know how far he will be so kind as to take trouble for me.—

When I began, I meant merely to thank you; but when a beggar once begins to beg he never knows when to stop!⁷

Pray accept my very cordial thanks & good wishes & believe me, My dear Sir | Your’s very sincerely | Ch. Darwin.