BRIEF OHNE UMSCHLAG Anonym ("H. B.") Author: Anonym ("H. B.") Recipient: Haeckel, Ernst Dating: 15.02.1906
BRIEF OHNE UMSCHLAG Altmann-Reich, Amalie Author: Altmann-Reich, Amalie Recipient: Haeckel, Ernst Dating: 06.01.1906
BRIEF OHNE UMSCHLAG Bertololy, Carl Author: Bertololy, Carl Recipient: Haeckel, Ernst Dating: 08.02.1906
BRIEF OHNE UMSCHLAG Kükenthal, Willy Author: Kükenthal, Willy Recipient: Haeckel, Ernst Dating: 14.02.1906
BRIEF OHNE UMSCHLAG Weber, Johannes Author: Weber, Johannes Recipient: Haeckel, Ernst Dating: 30.12.1906