POSTKARTE Amsberg, August von Author: Amsberg, August von Recipient: Haeckel, Ernst Dating: 16.05.1897
BRIEF [O.A.] Barchudarian, Johannes Author: Barchudarian, Johannes Recipient: Haeckel, Ernst Dating: 16.12.1897
BRIEF OHNE UMSCHLAG Marchal, Edmond Author: Marchal, Edmond Recipient: Haeckel, Ernst Corporation: Académie Royale des Sciences, des Lettres et des Beaux-Arts de Belgique Dating: 15.12.1897