I have taken my leisure in thanking you for your last letter and
discussion, to me very interesting, on the increase of species. Since your
letter, I have met with a very similar view in Richardson, who states that
the young are driven away by the old into unfavourable districts, and there
mostly perish. When one meets with such unexpected statistical returns on
the increase and decrease and proportion of deaths and births amongst
mankind, and in this well-known country of ours, one ought not to be in the
least surprised at one's ignorance, when, where, and how the endless
increase of our robins and sparrows is checked.

Thanks for your hints about terms of "mutation," etc.; I had some
suspicions that it was not quite correct, and yet I do not see my way to
arrive at any better terms. It will be years before I publish, so that I
shall have plenty of time to think of better words. Development would
perhaps do, only it is applied to the changes of an individual during its
growth. I am, however, very glad of your remark, and will ponder over it.

We are all well, wife and children three, and as flourishing as this
horrid, house-confining, tempestuous weather permits.


LETTER 18. TO J.D. HOOKER.
Down [1845].

I hope you are getting on well with your lectures, and that you have
enjoyed some pleasant walks during the late delightful weather. I write to
tell you (as perhaps you might have had fears on the subject) that your
books have arrived safely. I am exceedingly obliged to you for them, and
will take great care of them; they will take me some time to read