My dear Professor Semper

I have been much pleased to receive your letter but I did not expect you to answer my former one.¹ I think you are quite right not to answer to Ray Lankester’s article, for as far as I can judge, controversy does no good at all.² It is the best plan to modify any future publication & to acknowledge any criticism which seems just; & in any other case to take no notice..— I cannot remember what I wrote to you, but I am sure that it must have expressed the interest which I felt in reading your book.

I thought that you attributed too much weight to the direct action of the environment; but whether I said so, I know not, for without being asked I sh^d. have thought it presumptuous to have criticised your book. Nor should I now say so, had I not during the last few days been struck with Prof. Hoffmans review of his own work in the Botanische Zeitung on the variability of Plants;³ & it is really surprising how little effect he produced by cultivating certain plants under unnatural conditions, as to presence of salt, lime, zinc &c &c, during several generations.— Plants, moreover were selected, which were the most likely to vary under such conditions, judging from the existence of closely allied forms adapted for these conditions. No doubt I originally attributed too little weight to the direct action of conditions.; but Hoffman’s paper has staggered me.—⁴ Perhaps hundreds of generations of exposure are necessary. It is a most perplexing subject. I wish I was not so old & had more strength, for I see lines of research to follow. Hoffmann even doubts whether plants vary more under cultivation than in their native home & under their natural conditions!⁵

If so the astonishing variations of almost all cultivated plants must be due to selection & breeding from the varying individuals. This idea crossed my mind many years ago, but I was afraid to publish it as I thought that people w^d. say “how he does exaggerate the importance of selection”.—⁶

I still must believe that changed conditions give the impulse to variability, but that they act in most cases in a very indirect manner. But as I said it is a most perplexing problem.— Pray forgive me for writing at such length; I had no intention of doing so when I sat down to write.—

I am extremely sorry to hear, for your own sake & for that of Science, that you are so hard-worked & that so much of your time is consumed in official labour.—

Pray believe me | Dear Professor Semper | Yours sincerely | Charles Darwin