Jermyn Street, London, May 20, 1867.

My dear Haeckel,

Your letter, though dated the 12th, has but just reached me.  I mention this lest you should think me remiss, my sin in not writing to you already being sufficiently great.  But your book did not reach me until November, and I have been hard at work lecturing, with scarcely an intermission ever since.

Now I need hardly say that the “Morphologie” is not exactly a novel to be taken up and read in the intervals of business.  On the contrary, though profoundly interesting, it is an uncommonly hard book, and one wants to read every sentence of it over.

I went through it within a fortnight of its coming into my hands, so as to get at your general drift and purpose, but up to this time I have not been able to read it as I feel I ought to read it before venturing upon criticism.  You cannot imagine how my time is frittered away in these accursed lectures and examinations.

There can be but one opinion, however, as to the knowledge and intellectual grasp displayed in the book; and, to me, the attempt to systematise biology as a whole is especially interesting and valuable.

I shall go over this part of your work with great care by and by, but I am afraid you must expect that the number of biologists who will do so, will remain exceedingly small.  Our comrades are not strong in logic and philosophy.

With respect to the polemic excursus, of course, I chuckle over them most sympathetically, and then say how naughty they are!  I have done too much of the same sort of thing not to sympathise entirely with you; and I am much inclined to think that it is a good thing for a man, once at any rate in his life, to perform a public war-dance against all sorts of humbug and imposture.

But having satisfied one’s love of freedom in this way, perhaps the sooner the war-paint is off the better.  It has no virtue except as a sign of one’s own frame of mind and determination, and when that is once known, is little better than a distraction.

I think there are a few patches of this kind, my dear friend, which may as well come out in the next edition, e.g. that wonderful note about the relation of God to gas, the gravity of which greatly tickled my fancy.

I pictured to myself the effect which a translation of this would have upon the minds of my respectable countrymen!

Apropos of translation.  Darwin wrote to me on that subject, and with his usual generosity, would have made a considerable contribution towards the expense if we could have seen our way to the publication of a translation.  But I do not think it would be well to translate the book in fragments, and, as a whole, it would be a very costly undertaking, with very little chance of finding readers.

I do not believe that in the British Islands there are fifty people who are competent to read the book, and of the fifty, five and twenty have read it or will read it in German.