My dear Sir

Many thanks for your letter with the kind expressions towards me, & for what information you could give on the Gorgoniæ: I hardly expected any, but thought the specimens worth sending for the mere chance.¹ Thank you, also, for kindly wishing to oblige me & the British Museum about the cave animals,² should opportunity offer.—

The Sooloo cirripede is the Acasta sporillus;³ it differs from other members of the genus, (& indeed of the family) in the carino or postero-lateral compartment tending to become rudimentary, not extending down to the basal cup; & secondly in the very peculiar reticulated condition of the inside of the walls of the shell. Acasta is a genus or sub-genus for convenience sake only, as it is hardly separable from Balanus.⁴ The animal’s body rarely offers amongst the Balanidæ generic characters: I do not think any person could possibly distinguish the mouth & cirri of Balanus & the several succeeding genera: these parts sometimes offer specific characters, but then the parts must be examined in great detail. I am much surprised that you found A. sporillus alive, for I cannot but think the shell must be normally embedded in some substance like all its close congeners.⁵

I have seen, & been very much pleased with, the notice of my volume, which you have inserted in the N. American Journal:⁶ it has, I can assure you, given me great satisfaction. You will I think participate in my pleasure, when I tell you that Prof. Owen quite believes my facts as to Males of Ibla &c.— If ever opportunity offers, I hope you will carefully examine the attachment of the Lerneidæ⁷ with the fused legs: I may venture to suggest the use of hot caustic potash, as this in the case of cirripedes does not act on the chitinous cement. With respect to the larvæ of cirripedes, it is quite certain that during the first stage they have two anterior pairs of organs within cases, distinct from the 3 pair of legs round or near the probosciformed mouth: whether the organs are really antennæ may, of course, be disputed.⁸

I congratulate you sincerely on the progress of your Herculean labours on the Crustacea:⁹ I have a neighbour, who is very anxious to see this work; he is the son (very young) of Sir J. Lubbock, the great astronomer & Banker, who has taken up the smaller Crustacea with great zeal, & will soon publish a paper on a sub-genus, of Portia.¹⁰

I used the term of maxillipods by a gross blunder; I have a most unfortunate weakness in allowing errors of this kind to pass even when I know the derivations:¹¹ I perceived this blunder too late to put it in the errata: the term struck me as excellent in one of your letters. I shall read with interest your Geographical discussion in M^r Lubbock’s copy when he can purchase it.¹²

You ask whether I shall ever come to the U. States; I can assure you that no tour whatever could be half so interesting to me, but with my large family I do not suppose I shall ever leave home it would be a real pleasure to me to make your personal acquaintance.

Believe me, my dear Sir with thanks & every good wish— Yours most sincerely | C. Darwin