BRIEF OHNE UMSCHLAG Bleek, Auguste Author: Bleek, Auguste Recipient: Haeckel, Ernst Dating: 26.08.1870
BRIEF OHNE UMSCHLAG Bleek, Auguste Author: Bleek, Auguste Recipient: Haeckel, Charlotte Dating: 01.10.1870
BRIEF [O.A.] Beneden, Eduard van Author: Beneden, Eduard van Recipient: Haeckel, Ernst Dating: 11.12.1870
BRIEF OHNE UMSCHLAG Bleek, Wilhelm Heinrich Immanuel Author: Bleek, Wilhelm Heinrich Immanuel Recipient: Haeckel, Ernst Dating: 04.08.1870
BRIEF OHNE UMSCHLAG Bessels, Emil Author: Bessels, Emil Recipient: Haeckel, Ernst Corporation: Smithsonian Institution Dating: 05.03.1870