BRIEF OHNE UMSCHLAG Weismann, August Author: Weismann, August Recipient: Haeckel, Ernst Dating: 15.10.1865
BRIEF [O.A.] Vérany, Jean-Baptiste Author: Vérany, Jean-Baptiste Recipient: Haeckel, Ernst Dating: 01.03.1865
BRIEF OHNE UMSCHLAG Salverda, Matthijs Author: Salverda, Matthijs Recipient: Haeckel, Ernst Dating: 22.08.1865
BRIEF OHNE UMSCHLAG Salverda, Matthijs Author: Salverda, Matthijs Recipient: Haeckel, Ernst Dating: 19.08.1865