BRIEF [O.A.] Arnhold, Heinrich Author: Arnhold, Heinrich Recipient: Haeckel, Ernst Dating: 15.02.1904
BRIEF OHNE UMSCHLAG Bergh, Ernst van den Author: Bergh, Ernst van den Recipient: Haeckel, Ernst Dating: 06.08.1904
BRIEF OHNE UMSCHLAG Bölsche, Johanna Author: Bölsche, Johanna Recipient: Haeckel, Ernst Dating: 21.09.1899
BRIEF [O.A.] Bimler, Wilh... Author: Bimler, Wilh... Recipient: Haeckel, Ernst Corporation: Jac. Ziegler Dating: 11.12.1885
BRIEF OHNE UMSCHLAG Bermann, Cipri Adolf Author: Bermann, Cipri Adolf Recipient: Haeckel, Ernst Dating: 12.05.1905
BRIEF [O.A.] Ketelhodt, Hans Freiherr von Author: Ketelhodt, Hans Freiherr von Recipient: Haeckel, Ernst Dating: 28.06.1903
POSTKARTE Recipient: Haeckel, Ernst Corporation: Die Expedition der Kölnischen Zeitung Dating: 13.10.1903