BRIEF OHNE UMSCHLAG Bölsche, Wilhelm Author: Bölsche, Wilhelm Recipient: Haeckel, Ernst Dating: 31.12.1897
BRIEF OHNE UMSCHLAG Sachsen-Meiningen, Georg II., Herzog von Author: Sachsen-Meiningen, Georg II., Herzog von Recipient: Haeckel, Ernst Dating: 08.04.1897
TELEGRAMM Heldburg, Helene Freifrau von Author: Heldburg, Helene Freifrau von Recipient: Haeckel, Ernst Dating: 08.07.1897
TELEGRAMM Heldburg, Helene Freifrau von Author: Heldburg, Helene Freifrau von Recipient: Haeckel, Ernst Dating: 09.07.1897
TELEGRAMM Heldburg, Helene Freifrau von Author: Heldburg, Helene Freifrau von Recipient: Haeckel, Ernst Dating: 11.07.1897
BRIEF [O.A.] Schleicher, Fréres Author: Schleicher, Fréres Recipient: Haeckel, Ernst Dating: 27.01.1897
BRIEF [O.A.] Schulz, Arthur Author: Schulz, Arthur Recipient: Haeckel, Ernst Corporation: Zeitschrift "Der Bahnbrecher" Dating: 16.04.1897