BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Reimer, Ernst Dating: 22.06.1886
BRIEF MIT UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Semon, Richard Dating: 03.04.1886
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Krause, Ernst Dating: 14.01.1886
BRIEF [O.A.] Haeckel, Ernst Author: Haeckel, Ernst Recipient: Sachsen-Weimar, Karl Alexander von [Großherzog] Dating: 26.11.1886
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Niess, Albert Dating: 29.12.1886