BRIEF [O.A.] Lindemann, Arnold Author: Lindemann, Arnold Recipient: Haeckel, Ernst Dating: 14.07.1874
BRIEF OHNE UMSCHLAG Fürbringer, Bruno Author: Fürbringer, Bruno Recipient: Haeckel, Ernst Dating: o. D.
BRIEF OHNE UMSCHLAG Stobbe, August Author: Stobbe, August Recipient: Haeckel, Ernst Dating: 15.06.1880