EXPLANATION OF PLATE 16 



All figures were drawn with the camera from preparations fixed in hot 

 Schaudinn's fluid and stained with iron haematoxylin. X 2480. 



Figs. 1 to 3. Monocercomoiias melolonthae (Grassi) from the intestine of 

 PUthodoii oregonensis. 



Fig. 1. Monocercomonas melolonthae, showing the typical axostyle, fou- 

 equal anterior flagella, and vesicular nucleus. 



Fig. 2. The same, with chromatin granules lying against the nuclear 

 membrane. 



Fig. 3. The same, showing variations in size and contour. 



Figs. 4 to 9. Polymastix iufonis from the intestine of Diemyctylus torosus. 



Fig. 4. Ordinary trophozoite with large vacuoles in the cytoplasm and a 

 karyosome in the nucleus. 



Fig. 5. Trophozoite showing the rhizoplast connecting the parabasal body 

 and the blepharoplast. 



Fig. 6. View of trophozoite from the anterior end, showing the entire 

 structure of the parabasal body. 



Fig. 7. Large trophozoite with vesicular nucleus and large parabasal body. 



Fig. 8. Early prophase of division. 



Fig. 9. Early prophase of division. The blepharoplast has divided and the 

 chromatin has become condensed into granules. 



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