1. Paul Kammerer Papers, American Philosophical Society Library, Philadelphia, B/K128 [cited as “Kammerer Papers”]
2. Ernst-Haeckel-Haus, Jena, Best. A, Abt. 1
3. Bateson Papers, American Philosophical Society Library, Philadelphia, History of Science Collection, Microfilm no. 26, Reel E, Section Balto #32 [cited as “Bateson Papers”]
4. Richard Goldschmidt Papers, Bancroft Library, University of California, Berkeley [cited as “Goldschmidt Papers”]
5. Nachlaß August Weismann, Universitätsbibliothek Freiburg, Freiburg im Breisgau [cited as “Weismann Papers”]