Columbia subject headings:
Harvard subject headings:
Biologists--Germany--Biography.
Haeckel, Ernst, 1834-1919
Haeckel, Ernst, 1834-1919.
Schaxel, Julius, 1887-1943
Zoologists--Germany--Biography.
Princeton subject headings:
Biology.
Haeckel, Ernst, 1834-1919.
Schaxel, Julius, 1887-1943.