My dear Häckel

It was very good of you to write me so interesting a letter, & to tell me what points to attend to in your new book, as you know how poor a German scholar I am.¹

Your diagram of Olynthus is very striking, & I can see how readily it c^d be converted into a multitude of other forms, but it is too generous of you to send me the work in full when published, for, from the number of plates, it must be very expensive.² From what you say about correcting the proof sheets, I fear that you have been working much too hard. You will break down unless you moderate y^r labour; just reflect how much you have published & observed during the last few years. I have seen an advertisement of your Hist of Creation, but I do not believe it is actually published.³ I shall be glad when it appears; for I have never yet done it justice in the way of full reading.

I have rec^d the latter sheets of y^r book on sponges: I thought that I wd keep them for a few days so as to read a part, before forwarding them to Sir J Lubbock.⁴ I then became very unwell & left home for a week, & forgot all about them. On my return home in a few days time I will forward them with yr message about yr “Vorrede”.⁵

With respect to my book on expression, do not trouble yourself to read it, unless the subject happens to interest you. It has been very successful in England as far as sale goes.⁶

Farewell my good friend, & remember that no one can keep up such a strain on his mind as you put on yours— | yours most sincerely | Ch. Darwin

PS I have got Strauss’s new book, but the German is too difficult for me so I hope it may be translated⁷