PLATE XXIII 
LEEUWENHOEK’S PICTURES OF THE INTESTINAL PROTOZOA OF FROGS 
From the engravings in the Dutch edition of Letter 38 (16 July 1683). X 13. 
Fig. A, Opalina (Cépédea) dimidiata. 
Fig. B, Nyctotherus cordiformis. 
Fig. C, a larval nematode ? 
facing p. 233 
