POSTKARTE Sarasin, Paul; Sarasin, Fritz Author: Sarasin, Paul; Sarasin, Fritz Recipient: Haeckel, Ernst Dating: 07.02.1902
POSTKARTE Herdman, William A... Author: Herdman, William A... Recipient: Haeckel, Ernst Dating: 14.03.1908
BRIEF OHNE UMSCHLAG Rautenfeld, Paul von Author: Rautenfeld, Paul von Recipient: Haeckel, Ernst Dating: 25.02.1909
BRIEF OHNE UMSCHLAG Marshall-Ward, Harry Author: Marshall-Ward, Harry Recipient: Haeckel, Ernst Dating: 14.01.1882
BRIEF OHNE UMSCHLAG Ankenbrand, Ludwig Author: Ankenbrand, Ludwig Recipient: Haeckel, Ernst Dating: 15.03.1914