BILDPOSTKARTE Rottenburg, Paul von Author: Rottenburg, Paul von Recipient: Haeckel, Ernst Dating: 22.12.1901
BILDPOSTKARTE Haeckel, Walther Author: Haeckel, Walther Recipient: Haeckel, Ernst; Haeckel, Agnes [Eltern] Dating: 14.05.1901
BILDPOSTKARTE Kükenthal, Willy Georg [et al.] Author: Kükenthal, Willy Georg [et al.] Recipient: Haeckel, Ernst Dating: 08.08.1901
BILDPOSTKARTE Ziegler, Heinrich Ernst Author: Ziegler, Heinrich Ernst Recipient: Haeckel, Ernst Dating: 13.08.1901