BRIEF [O.A.] Liven, Maximilian [Fürst] Author: Liven, Maximilian [Fürst] Recipient: Haeckel, Ernst Dating: 14.03.1889
BRIEF [O.A.] Seidlitz, Georg [von] Author: Seidlitz, Georg [von] Recipient: Haeckel, Ernst Dating: 17.03.1872
BRIEF [O.A.] Seidlitz, Georg [von] Author: Seidlitz, Georg [von] Recipient: Haeckel, Ernst Dating: 06.05.1873
BRIEF [O.A.] Brandt, Alexander Author: Brandt, Alexander Recipient: Haeckel, Ernst Dating: 19.02.1914
BRIEF [O.A.] Boettcher, Arthur Author: Boettcher, Arthur Recipient: Haeckel, Ernst Dating: 06.09.1867
BRIEF [O.A.] Boettcher, Arthur Author: Boettcher, Arthur Recipient: Haeckel, Ernst Dating: 11.06.1889