Collecting specimens was an indispensable part of Darwin’s scientific method. In this collection of letters, Darwin corresponds with a variety of people to secure specimens and information for his barnacle book.
Letter 1140 — Darwin, C. R. to Ross, J. C., 31 Dec 1847
Darwin asks Ross to collect cirripedes for him on Ross’s forthcoming expedition to the Arctic in search of Sir John Franklin.
Letter 1262 — Darwin, C. R. to Hancock, Albany, [29–30 Oct 1849]
Darwin thanks Hancock for specimens of Alcippe. He comments on sketches by Hancock, on a cirripede paper by Lovén, and discusses Lithotrya and its burrowing habits.
Letter 1495 — Darwin, C. R. to Hancock, Albany, 25 Dec 
Darwin discusses the capacity of some cirripedes to bore into rock and mentions Alcippe specimens borrowed from Hanocock. He asks Hancock to look at his collection to check on his suspicions.
Letter 1370 — Darwin, C. R. to Covington, Syms, 23 Nov 1850
Darwin thanks Covington for the box of cirripedes specimens. He thanks him for the trouble taken and is pleased with “one so rich from one locality”. This one contains a new species of genus which, to Darwin’s knowledge, only one specimen is known to exist in the world.
Letter 1251 — Darwin, C. R. to Gould, A. A., 20 Aug 
Darwin thanks J. D. Dana for cirripede specimens. Darwin describes his work. He comments on Ibla. He would like to see Gould’s notes and figures on Anatifa, and asks for references to cirripede descriptions by T. A. Conrad.