Sir

I trust to what I hear of your character of wishing to assist all Naturalists, to excuse the great liberty I take in addressing you.— I have been employed for nearly two years on an Anatomical & Systematic Monograph on the Cirripedia. It is my intention to describe the animal of every species, which by soaking I am enabled to do even with dry specimens. All the descriptions, without exception, which I have hitherto seen are too imperfect for the identification of species: external forms, proportions & state of surface are nearly valueless as characters. I have excellent materials placed in my hands in the collection of M^r Cuming, Stutchbury, Sowerby, Lyell &c &c, & the Trustees of the British Museum have done me the unusual honour of allowing me to have the public collection at my own house: I mention this merely to show that I am considered here a trustworthy person.— Now the object of this letter is to ask the great and unusual favour of the loan (I paying carriage both ways) of any N. American (or other) collection.¹

The species of the United states would be particularly interesting to me, for comparison with Europæan, on account of Geographical range. I am aware that you have described some species,² & I am most anxious to avoid giving a second name, which I cannot do without seeing specimens of yours & being allowed to disarticulate one or two of each kind.

Say has described a Coronula denticulata from the King-Crab:³ his description does not allow me even to know the genus. & I am particularly anxious to know this form, which I imagine to be a Platylepas, though all the other species are parasitic on Vertebrata.⁴ This species will perhaps be in some Public collection would it be possible, considering that no monograph has been ever been written on the Cirripedia, to get me the loan of a specimen or the gift of one to be deposited afterwards in the British Museum, to which body I give all my own collection.—

Of course the species inhabiting the coast of the United states near Boston would be most valuable to me in Spirits.—

I cannot offer any sufficient apology for the intrusion of this letter, but must rely solely on your kindness.

With much respect, | I beg to remain | Sir | Your faithful & obliged servant | Charles Darwin To | D^r. Gould | &c &c &c

Since writing the above I have heard from M^r Lyell, who says I may use his name as some introduction to you⁵