BILDPOSTKARTE Recipient: Haeckel, Ernst Corporation: Verlagsbuchhandlung Georg Reimer in Berlin Dating: 18.04.1908
BILDPOSTKARTE Meyer, Elisabeth Author: Meyer, Elisabeth Recipient: Haeckel, Ernst; Haeckel, Agnes [Eltern] Dating: 04.06.1896
BILDPOSTKARTE Eulenberg, Herbert; Eulenberg, Hedda Author: Eulenberg, Herbert; Eulenberg, Hedda Recipient: Haeckel, Ernst Corporation: Universum Film Aktiengesellschaft Dating: 19.06.1918