BRIEF [O.A.] Boettger, O.. Author: Boettger, O.. Recipient: Haeckel, Ernst Corporation: Redaktion der Zeitschrift "Der Zoologische Garten" Dating: 17.08.1904
BRIEF [O.A.] Blum, J... Author: Blum, J... Recipient: Haeckel, Ernst Corporation: Senckenbergische Naturforschende Gesellschaft Dating: 25.12.1897
BRIEF [O.A.] Baumann, Adolph Author: Baumann, Adolph Recipient: Haeckel, Ernst Corporation: Adolph Baumann, Passementerie-, Corsetten- & Stramin-Fabrik Dating: 08.01.1877
BRIEF OHNE UMSCHLAG Almeroth, Hans Author: Almeroth, Hans Recipient: Haeckel, Ernst Dating: 16.02.1915
BRIEF [O.A.] Bechhold Author: Bechhold Recipient: Haeckel, Ernst Corporation: Die Umschau Dating: 12.01.1904
BRIEF [O.A.] Bechhold Author: Bechhold Recipient: Haeckel, Ernst Corporation: Die Umschau Dating: 12.01.1904
BRIEF [O.A.] Bechhold Author: Bechhold Recipient: Haeckel, Ernst Corporation: Die Umschau Dating: 08.04.1907