Scientific specialism and detail
Experimental practice
- Letter 4895 — Darwin, C. R. to Müller, J. F. T., 20 Sept [1865]
- Letter 5173 — Müller, J. F. T. to Darwin, C. R., 2 Aug 1866
- Letter 5429 — Müller, J. F. T. to Darwin, C. R., 4 Mar 1867
- Letter 5480 — Müller, J. F. T. to Darwin, C. R., 1 Apr 1867
- Letter 5551 — Darwin, C. R. to Müller, J. F. T., 26 May [1867]
Using microscopes
- Letter 207 — Darwin, C. R. to Fox, W. D., 23 May 1833
- Letter 1018 — Darwin, C. R. to Hooker, J. D., [6 Nov 1846]
- Letter 1166 — Darwin, C. R. to Owen, Richard, [26 Mar 1848]
- Letter 1167 — Darwin, C. R. to Henslow, J. S., [1 Apr 1848]
- Letter 1174 — Darwin, C. R. to Hooker, J. D., 10 May 1848
Collecting specimens
- Letter 1140 — Darwin, C. R. to Ross, J. C., 31 Dec 1847
- Letter 1262 — Darwin, C. R. to Hancock, Albany, [29–30 Oct 1849]
- Letter 1495 — Darwin, C. R. to Hancock, Albany, 25 Dec [1852]
- Letter 1370 — Darwin, C. R. to Covington, Syms, 23 Nov 1850
- Letter 1251 — Darwin, C. R. to Gould, A. A., 20 Aug [1849]
Theory and practice
- Letter 1202 — Darwin, C. R. to Hooker, J. D., 6 Oct [1848]
- Letter 1220 — Hooker, J. D. to Darwin, C. R., 3 Feb 1849
- Letter 1260 — Darwin, C. R. to Hooker, J. D., 12 Oct 1849
- Letter 1319 — Hooker, J. D. to Darwin, C. R., 6 & 7 Apr 1850
- Letter 1339 — Darwin, C. R. to Hooker, J. D., 13 June [1850]