BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Siebold, Carl Theodor Ernst von Dating: 27.01.1871
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Weismann, August Dating: 03.05.1871
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Focke, Wilhelm Olbers Dating: 24.05.1871