BRIEF OHNE UMSCHLAG Allmers, Hermann Author: Allmers, Hermann Recipient: Haeckel, Ernst Dating: 06.06.1889
BRIEF [O.A.] Bovio, Giovanni Author: Bovio, Giovanni Recipient: Haeckel, Ernst Corporation: Camera dei Deputati Dating: 18.06.1889
BRIEF OHNE UMSCHLAG Brettauer, Josef Author: Brettauer, Josef Recipient: Haeckel, Ernst Dating: 01.12.1889
BRIEF [O.A.] Capellini, Giovanni Author: Capellini, Giovanni Recipient: Haeckel, Ernst Corporation: R. Università di Bologna, R. Istituto Geologio e Paleontologio Dating: 31.12.1889