BRIEF [O.A.] Verworn, Max Author: Verworn, Max Recipient: Uslar-Gleichen, Bernhard von Dating: 12.01.1909
BRIEF [O.A.] Haeckel, Ernst Author: Haeckel, Ernst Recipient: Marx, Ernst Dating: 1909.??.?? [nach 20.03.1909]
BRIEF [O.A.] Haeckel, Ernst Author: Haeckel, Ernst Recipient: Uslar-Gleichen, Bernhard von Dating: 13.03.1909
BRIEF [O.A.] Haeckel, Ernst Author: Haeckel, Ernst Recipient: Uslar-Gleichen, Bernhard von Dating: 07.09.1909
BRIEF [O.A.] Haeckel, Ernst Author: Haeckel, Ernst Recipient: Uslar-Gleichen, Bernhard von Dating: 21.12.1909
BRIEF [O.A.] Grobben, Karl Author: Grobben, Karl Recipient: Haeckel, Ernst Corporation: 1. Zoologisches Institut, K. K. Universität Wien Dating: 02.02.1909