My dear Sir

I thank you sincerely for your very kind letter, and for the present of your new work. My son Francis, if he had been at home, would have likewise sent his thanks.¹ I will immediately begin to read your book, and when I have finished it, will write again. But I read German so very slowly, that your book will take me a considerable time, for I cannot read for more than half-an-hour each day. I have, also, been working too hard lately and with very little success, so that I am going to leave home for a time and try to forget science.²

I quite expect that you will find some gross errors in my work, for you are a very much more skilful and profound experimentalist than I am. Although I always am endeavouring to be cautious and to mistrust myself, yet I know well how apt I am to make blunders. Physiology, both animal and vegetable, is so difficult a subject that it seems to me to progress chiefly by the elimination or correction of ever recurring mistakes. I hope that you will not have upset my fundamental notion that various classes of movement result from the modification of a universally present movement of cirumnutation.³

I am very glad that you will again discuss the view of the turgescence of the cells being the cause of the movement of parts. I adopted De Vries’ views as seeming to me the most probable, but of late I have felt more doubts on this head.⁴

Thanking you again heartily for your kind note I remain with much respect | My dear Sir | Yours very faithfully | Charles Darwin