From W. S. Dallas   11 December 1867

My dear Sir

I write to apologise to you if the remarks in my note of Sunday last seem to you so much in the nature of criticism as I fear they do.—¹ Nothing was further from my intention.— The questions as to the use of the name Tadorna, the name of the Pheasant & the transposition of the notes were necessary ones,— the use of Dragon instead of Dragoon is of not the least consequence, but as I was more familiar with the latter name I noted it in passing,—& the Arab matter I mentioned, not as pointing out an error, but because I thought you might feel interested in the explanation of the point.—²

I last night timed myself & found that in 5 hours hard work I got through 3 sheets less 2 pages, & this is more than I have been able to do sometimes since working the whole of the references together.—³ The subjects often seem to elude the Index-maker, as the noticing every point taken up would often be to transpose whole pages in an altered form to the Index,—& on the other hand it is difficult, or sometimes impossible to hit upon any middle course between this elaborate Analysis & the simple notice of the general subject.—

Of course this note requires no answer, but you may depend on my pushing forward at my best speed.—

Believe me | Your’s very truly | W. S. Dallas

C. Darwin Esq^r.