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 facit saltum so unreservedly; and 2nd, It is not clear to me why, if continual physical conditions are of so little moment as you suppose, variation should occur at all.

However, I must read the book two or three times more before I presume to begin picking holes.

I trust you will not allow yourself to be in any way disgusted or annoyed by the considerable abuse and misrepresentation which, unless I greatly mistake, is in store for you.  Depend upon it, you have earned the lasting gratitude of all thoughtful men.  And as to the curs which will bark and yelp, you must recollect that some of your friends, at any rate, are endowed with an amount of combativeness which (though you have often and justly rebuked it) may stand you in good stead.

I am sharpening up my claws and beak in readiness.

Looking back over my letter, it really expresses so feebly all I think about you and your noble book, that I am half-ashamed of it; but you will understand that, like the parrot in the story, “I think the more.”

Ever yours faithfully,

T.H.  Huxley.

[A month later, fortune put into his hands the opportunity of striking a vigorous and telling blow for the newly-published book.  Never was windfall more eagerly accepted.  A short account of this lucky chance was written by him for the Darwin “Life” (volume 1 page 255).]