BRIEF [O.A.] Miklucho-Maclay, Nikolaj N... Author: Miklucho-Maclay, Nikolaj N... Recipient: Haeckel, Ernst Dating: 18.10.1866
BRIEF [O.A.] Hildebrand, Bruno Author: Hildebrand, Bruno Recipient: Haeckel, Ernst Dating: 21.03.1866
BRIEF [O.A.] Haeckel, Ernst Author: Haeckel, Ernst Recipient: Bleek, Wilhelm Heinrich Immanuel Dating: 15.09.1866
BRIEF [O.A.] Haeckel, Ernst Author: Haeckel, Ernst Recipient: Haeckel, Carl Gottlob Dating: 10.03.1866
BRIEF [O.A.] Kauffmann, Julius Author: Kauffmann, Julius Recipient: Haeckel, Ernst Dating: 18.09.1866