ANSICHTSKARTE Haeckel, Walther Author: Haeckel, Walther Recipient: Haeckel, Ernst; Haeckel, Agnes Dating: 26.06.1886
POSTKARTE Haeckel, Walther Author: Haeckel, Walther Recipient: Haeckel, Ernst; Haeckel, Agnes Dating: 07.11.1883
BRIEF [O.A.] Haeckel, Walther Author: Haeckel, Walther Recipient: Allmers, Hermann Dating: 14.05.1885