BRIEF [O.A.] Fiedler, Bh... [?] Author: Fiedler, Bh... [?] Recipient: Haeckel, Ernst Dating: 09.04.1878
BRIEF [O.A.] Marchi, Pietro; Marchi, Elena Author: Marchi, Pietro; Marchi, Elena Recipient: Haeckel, Ernst Dating: 15.11.1878
BRIEF [O.A.] Krauseneck, Heinrich Author: Krauseneck, Heinrich Recipient: Haeckel, Ernst Dating: 05.01.1878