BRIEF [O.A.] Mayer, Louis Author: Mayer, Louis Recipient: Haeckel, Ernst Corporation: Institut Océanographique Dating: 07.01.1910
BRIEF [O.A.] Poincaré, Henry Author: Poincaré, Henry Recipient: Haeckel, Ernst Corporation: Institut General Psychologique Dating: 14.11.1910
POSTKARTE Porter, Carlos Emilio Author: Porter, Carlos Emilio Recipient: Haeckel, Ernst Dating: 15.10.1910
BRIEF [O.A.] Vayssiere, A... Author: Vayssiere, A... Recipient: Haeckel, Ernst Corporation: Université D Aix-Marseille Dating: 28.07.1910
BRIEF OHNE UMSCHLAG Strasburger, Eduard Author: Strasburger, Eduard Recipient: Haeckel, Ernst Dating: 06.04.1910