Dear Sir.

I am very much obliged to you for so kindly sending me the excellent drawings of the 2^nd leg of the larva in the different stages,¹ & for giving me permission to refer to your paper as if published;² & that it will most likely be before my volume which will include in the introduction a mere brief abstract on the anatomy of the cirripedia.— With regard to the metamorphoses my chief work has been in the last stage—& I have done the anatomy in much detail at that period.— It has occurred to me before now, to have been working hard at a subject, & then found that my results had been previously published, & very much provoked I have felt.—³ therefore I can appreciate & admire the very pleasant manner in which you received my unpleasant tidings.—⁴ I think you will find it useful to preserve small objects, in a way in which I have been accustomed to preserve the results of most of my minute anatomical researches, namely in common water without any spirits, with a Bit of thin glass over the object (without any cell) & gold size all round the rough edge—objects thus prepared will sometimes keep for a long time & generally for some months.—⁵ If you are inclined to take the trouble to rear any larvæ to the second stage, you could so send them me or better in a very minute bottle of spirits—⁶ Every cirripede that I dissect I preserve the jaws &c. &c. in this manner, which takes no time & often comes in very useful. This very day I have been using preparations thus made two years since, & they are perfectly clear & with some colour preserved, As I am in the way of suggesting—I would strongly advise you to get one of the glass ruled micrometers to slip in eye piece, the whole does not cost much above half a guinea, you would only have to send medium eyepiece to London & you could measure to the 120,000^th or less of an inch, without delaying your work half a minute.—⁷

With every good wish—Believe me | Dear Sir. | Yours faithfully. | C. Darwin

P.S. I suppose the Balanus which you call balanoides encrusts the rocks between high & low water, & are not very large— I ask as a caution, because there are three or four British species, but only one common on tidal rocks, At Tenby there is however a large, dark coloured steeply conical kind common on tidal rocks—viz—B. perforatus.⁸