BRIEF [O.A.] Agassiz, Alexander Author: Agassiz, Alexander Recipient: Haeckel, Ernst Corporation: Museum of Comparative Zoology, at Harvard College Dating: 29.12.1868
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.] Binder, Carl Ferdinand Author: Binder, Carl Ferdinand Recipient: Haeckel, Ernst Dating: 02.02.1868
BRIEF [O.A.] Charisius, A... Author: Charisius, A... Recipient: Haeckel, Ernst Corporation: Lüderitz'sche Verlagsbuchhandlung Dating: 01.05.1868