BRIEF [O.A.] Haltermann, Hermann Author: Haltermann, Hermann Recipient: Haeckel, Ernst Dating: 08.05.1871
BRIEF [O.A.] Haltermann, Hermann Author: Haltermann, Hermann Recipient: Haeckel, Ernst Dating: 12.05.1871
BRIEF OHNE UMSCHLAG Focke, Wilhelm Olbers Author: Focke, Wilhelm Olbers Recipient: Haeckel, Ernst Dating: 09.05.1871
BRIEF [O.A.] Gildemeister, E... Author: Gildemeister, E... Recipient: Haeckel, Ernst Dating: 18.01.1871
BRIEF [O.A.] Gildemeister, E... Author: Gildemeister, E... Recipient: Haeckel, Ernst Dating: 23.02.1871