BRIEF OHNE UMSCHLAG Greeff, Richard Author: Greeff, Richard Recipient: Haeckel, Ernst Dating: 21.11.1870
BRIEF [O.A.] Gümbel, Wilhelm von Author: Gümbel, Wilhelm von Recipient: Haeckel, Ernst Dating: 10.11.1870
BRIEF OHNE UMSCHLAG Focke, Wilhelm Olbers Author: Focke, Wilhelm Olbers Recipient: Haeckel, Ernst Dating: 29.06.1870
BRIEF OHNE UMSCHLAG Ehlers, Ernst Author: Ehlers, Ernst Recipient: Haeckel, Ernst Corporation: Zootom. Institut Dating: 12.12.1870