BRIEF [O.A.] Miklucho-Maclay, Nikolaj N... Author: Miklucho-Maclay, Nikolaj N... Recipient: Haeckel, Ernst Dating: 18.10.1866
BRIEF [O.A.] Haeckel, Charlotte Author: Haeckel, Charlotte Recipient: Haeckel, Ernst Dating: 10.03.1866
BRIEF [O.A.] Sethe, Wilhelmine (geb. Bölling) Author: Sethe, Wilhelmine (geb. Bölling) Recipient: Haeckel, Ernst Dating: 25.01.1866
BRIEF [O.A.] Sethe, Wilhelmine (geb. Bölling) Author: Sethe, Wilhelmine (geb. Bölling) Recipient: Haeckel, Ernst Dating: 14.02.1866