BRIEF [O.A.] Dreyer, Friedrich Author: Dreyer, Friedrich Recipient: Haeckel, Ernst Dating: 10.12.1884
BRIEF [O.A.] Eisenhardt, Friedr... Author: Eisenhardt, Friedr... Recipient: Haeckel, Ernst Dating: 10.03.1917
POSTKARTE Weißenborn, Wilhelm Author: Weißenborn, Wilhelm Recipient: Haeckel, Ernst Dating: 08.04.1892
BRIEF OHNE UMSCHLAG Weißenborn, Wilhelm Author: Weißenborn, Wilhelm Recipient: Haeckel, Ernst Dating: 28.08.1887
BRIEF OHNE UMSCHLAG Weißenborn, Wilhelm Author: Weißenborn, Wilhelm Recipient: Haeckel, Ernst Dating: 08.05.1889
BRIEF OHNE UMSCHLAG Weißenborn, Wilhelm Author: Weißenborn, Wilhelm Recipient: Haeckel, Ernst Dating: 19.02.1889
BRIEF OHNE UMSCHLAG Weißenborn, Wilhelm Author: Weißenborn, Wilhelm Recipient: Haeckel, Ernst Dating: 11.09.1890