BRIEF [O.A.] Ferber, M... R... Author: Ferber, M... R... Recipient: Haeckel, Ernst Dating: 23.06.1868
BRIEF [O.A.] Engelmann, Theodor; Engelmann, Wilhelm Author: Engelmann, Theodor; Engelmann, Wilhelm Recipient: Haeckel, Ernst Corporation: Wilhelm Engelmann Verlagsbuchhandlung Dating: 24.03.1868
BRIEF [O.A.] Charisius, A... Author: Charisius, A... Recipient: Haeckel, Ernst Corporation: Lüderitz'sche Verlagsbuchhandlung Dating: 13.06.1868
BRIEF [O.A.] Cotta, Bernhard von Author: Cotta, Bernhard von Recipient: Haeckel, Ernst Dating: 18.10.1868
BRIEF [O.A.] Focke, Gustav Waldemar Author: Focke, Gustav Waldemar Recipient: Haeckel, Ernst Dating: 15.05.1868
BRIEF [O.A.] Gaedechens, Rudolph Author: Gaedechens, Rudolph Recipient: Haeckel, Ernst Dating: 15.11.1868