BRIEF OHNE UMSCHLAG Borngräber, Otto Author: Borngräber, Otto Recipient: Haeckel, Ernst Dating: 08.04.1905
BRIEF [O.A.] Baerenbach, Friedrich von Author: Baerenbach, Friedrich von Recipient: Haeckel, Ernst Dating: 21.11.1878
BRIEF [O.A.] Barthel, Walter et al. Author: Barthel, Walter et al. Recipient: Haeckel, Ernst Dating: 10.03.1908
BRIEF OHNE UMSCHLAG Behn, Wilhelm Friedrich Georg Author: Behn, Wilhelm Friedrich Georg Recipient: Haeckel, Ernst Corporation: Academia Caesarea Germanica Leopoldino-Carolina Dating: 18.02.1875
BRIEF OHNE UMSCHLAG Berghof, Jean von Author: Berghof, Jean von Recipient: Haeckel, Ernst Dating: 17.01.1908
BRIEF OHNE UMSCHLAG Bandmann, Otto Author: Bandmann, Otto Recipient: Haeckel, Ernst Dating: ??.08.1913
BRIEF [O.A.] Baerenbach, Friedrich von Author: Baerenbach, Friedrich von Recipient: Haeckel, Ernst Dating: 11.11.1878