I finished your book yesterday, a lucky examination having furnished me
with a few hours of continuous leisure.

Since I read Von Baer's essays, nine years ago, no work on Natural
History Science I have met with has made so great an impression upon me,
and I do most heartily thank you for the great store of new views you
have given me. Nothing, I think, can be better than the tone of the
book--it impresses those who know about the subject. As for your
doctrine, I am prepared to go to the stake, if requisite, in support of
Chapter 9 [The Imperfection of the Geological Record], and most parts of
Chapters 10 [The Geological Succession of Organic Beings], 11, 12
[Geographical Distribution], and Chapter 13 [Classification, Morphology,
Embryology, and Rudimentary Organs] contains much that is most
admirable, but on one or two points I enter a caveat until I can see
further into all sides of the question.

As to the first four chapters [Chapter 1, Variation under Domestication;
2, Variation under Nature; 3, The Struggle for Existence; 4, Operation
of Natural Selection; 5, Laws of Variation], I agree thoroughly and
fully with all the principles laid down in them. I think you have
demonstrated a true cause for the production of species, and have thrown
the onus probandi, that species did not arise in the way you suppose, on
your adversaries.

But I feel that I have not yet by any means fully realised the bearings
of those most remarkable and original Chapters--III, IV, and V, and I
will write no more about them just now.

The only objections that have occurred to me are--1st, That you have
loaded yourself with an unnecessary difficulty in adopting Natura non