BRIEF [O.A.] Liven, Maximilian [Fürst] Author: Liven, Maximilian [Fürst] Recipient: Haeckel, Ernst Dating: 14.03.1889
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
BRIEF MIT UMSCHLAG Baer, Karl Ernst von Author: Baer, Karl Ernst von Recipient: Haeckel, Ernst Dating: 29.12.1876
BRIEF [O.A.] Brandt, Alexander Author: Brandt, Alexander Recipient: Haeckel, Ernst Dating: 19.02.1914
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 OHNE UMSCHLAG Staël von Holstein, Reinhold Baron Author: Staël von Holstein, Reinhold Baron Recipient: Haeckel, Ernst Dating: 01.03.1888