BRIEF [O.A.] Gümbel, Wilhelm von Author: Gümbel, Wilhelm von Recipient: Haeckel, Ernst Dating: 10.11.1870
BRIEF [O.A.] Engelmann, Theodor; Engelmann, Theodor Wilhelm Author: Engelmann, Theodor; Engelmann, Theodor Wilhelm Recipient: Haeckel, Ernst Dating: 14.03.1870
BRIEF [O.A.] Czermak, Johannes Author: Czermak, Johannes Recipient: Haeckel, Ernst Dating: 03.12.1870
BRIEF [O.A.] Fleischer, Richard Author: Fleischer, Richard Recipient: Haeckel, Ernst Dating: 04.11.1870
BRIEF [O.A.] Fleischer, Richard Author: Fleischer, Richard Recipient: Haeckel, Ernst Dating: 07.07.1870