Briefe
zu den Filteroptionen- Haeckel, Ernst ; Verworn, MaxJena, 3.3.1913 [3.3.1913]
- Haeckel, Ernst ; Verworn, MaxJena, 20.2.1913 [20. Februar 1913]
- Haeckel, Ernst ; Verworn, MaxJena, 3.3.1912 [3.3.1912]
- Haeckel, Ernst ; Verworn, Josephine ; Haeckel, AgnesJena, 17.4.1912 [17. April 1912]
- Haeckel, Ernst ; Verworn, MaxJena, 28.2.1917 [28.2.1917]
- Haeckel, Ernst ; Verworn, Max ; Verworn, JosephineRapallo, Hotel Eden, 29.12.1903
- Haeckel, Ernst ; Verworn, MaxBenniehausen [Poststempel], 27.5.1904 [27.5.[19]04]
- Haeckel, Ernst ; Verworn, MaxJena, 6.5.1904 [6. Mai 1904]
- Kaiser, Alfred ; Verworn, MaxSuez, 27.4.1891 [27. April [18]91]
- Haeckel, Ernst ; Verworn, MaxJena, 11.6.1890 [11. Juni [18]90]
- Haeckel, Ernst ; Verworn, MaxJena, 4.6.1890 [4. Juni [18]90]
- Haeckel, Ernst ; Verworn, MaxJena, 3.3.1905 [3.3.1905]
- Haeckel, Ernst ; Verworn, MaxJena, 4.11.1917 [4.11.1917]
- Haeckel, Ernst ; Verworn, MaxJena, 28.7.1890 [28. Juli 1890]
- Haeckel, Ernst ; Verworn, MaxJena, 5.11.1890 [5. Novbr. 1890]
- Haeckel, Ernst ; Verworn, MaxJena, 3.3.1895 [3.3.1895]
- Haeckel, Ernst ; Verworn, Max ; Haeckel, Agneso.O., 12.12.1889 [12. Dec. 1889]
- Haeckel, Ernst ; Verworn, Max ; Haeckel, Agneso.O., [30. November [o.J.]]