BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Sethe, Christoph Dating: 22.05.1840
BRIEF [O.A.] Osterwald, Wilhelm Author: Osterwald, Wilhelm Recipient: Haeckel, Carl Gottlob Dating: 06.03.1852
POSTKARTE Finsterbusch, Ludwig Author: Finsterbusch, Ludwig Recipient: Haeckel, Ernst Dating: 17.08.1885
