My dear Sir

You are very kind in telling me not to write; & though I am too hard worked, it is a pleasure to me to write, otherwise I would not do so.— Your note is a real gold-mine of facts & suggestions, all new to me.² I am very glad to hear of Gratiolets remark,³ for I remember being very anxious to know how the case was; & I remember wishing to know how early an organ modified in a very unusual manner in its class appeared, relatively to its homologue in other members of the same class: & I thought that a Bat’s wing would be good case, but I could not find any description.—⁴

Your cases of analogous variations are very valuable to me, & indeed all your note.— I do not know whether Craniologists can be at all believed, who assert that the Head alters in shape after peculiar studies in the adult.— I may mention a little personal anecdote. I worked hard during voyage of the Beagle & was a very idle sportsman before; & when I returned after 5 years, my Father almost immediately exclaimed, “Why the shape of your head is altered.”—

I was much interested by your papers in Nat. Hist. R.⁵ & I was pleased to see in Silliman’s Journal that your article was specially noticed.—⁶

I have had a hard morning’s dissection at some plants & am tired & will not amuse myself, by scribbling any more.

With hearty thanks for favours past & to come! | Yours sincerely | Charles Darwin