BRIEF OHNE UMSCHLAG Ihering, Hermann von Author: Ihering, Hermann von Recipient: Haeckel, Ernst Dating: 02.05.1880
BRIEF [O.A.] Zeppenfeld, Victor Author: Zeppenfeld, Victor Recipient: Haeckel, Ernst Dating: 04.11.1880
BRIEF OHNE UMSCHLAG Rolle, Friedrich Author: Rolle, Friedrich Recipient: Haeckel, Ernst Dating: 08.03.1880
BRIEF OHNE UMSCHLAG Rodenberg, Julius Author: Rodenberg, Julius Recipient: Haeckel, Ernst Corporation: Deutsche Rundschau Dating: 27.04.1880