BRIEF [O.A.] Freytag, G... Author: Freytag, G... Recipient: Haeckel, Ernst Corporation: Verlagsbuchhandlung, F. Tempsky und G. Freytag Dating: 27.03.1884
BRIEF OHNE UMSCHLAG Geddes, Patrick Author: Geddes, Patrick Recipient: Haeckel, Ernst Corporation: University College Dundee Dating: 19.05.1884
BRIEF [O.A.] Cohn Author: Cohn Recipient: Haeckel, Ernst Corporation: Verein für Geographie & Statistik Dating: 26.09.1884
BRIEF OHNE UMSCHLAG Bose, Carl August Graf Author: Bose, Carl August Graf Recipient: Haeckel, Ernst Dating: 08.05.1884