BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Hertwig, Oskar; Hertwig, Richard Dating: 10.12.1872
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Hertwig, Oskar; Hertwig, Richard Dating: 28.08.1872
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Hertwig, Oskar; Hertwig, Richard Dating: 29.04.1872
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Hertwig, Oskar; Hertwig, Richard Dating: 20.02.1872