BRIEF [O.A.] Köhler, Fritz Author: Köhler, Fritz Recipient: Haeckel, Ernst Corporation: Naturforschende Gesellschaft des Osterlandes Dating: 11.08.1919
POSTKARTE Geibel, Stephan Author: Geibel, Stephan Recipient: Haeckel, Ernst Corporation: Pierer'sche Hofbuchdruckerei Dating: 28.03.1903
TELEGRAMM Sachsen-Altenburg, Ernst II., Herzog von Author: Sachsen-Altenburg, Ernst II., Herzog von Recipient: Haeckel, Ernst Dating: 16.02.1914
TELEGRAMM Voretzsch, Max Author: Voretzsch, Max Recipient: Haeckel, Ernst Corporation: Naturforschende Gesellschaft des Osterlandes Dating: 16.02.1894