EXPLANATION OF PLATE 15 



All figures from material fixed in Schaudinn 's fluid aud stained by the wet 

 irou-haematoxylin method. X 3195. 



Figs. 21-28, inclusive, from the stomach; figs. 29-47, from the rectum. 



Fig. 21. Rolled-up crithidial stage in U-shape with central lacuna aud long, 

 free flagellum. 



Fig. 22. Later phase of rolled-up crithidial stage, suggesting preparation 

 for intracellular multiple fission. 



Figs. 22-28. Transition from crithidial forms in the stomach to the haptoni- 

 onad crithidial forms in the rectum. 



Fig. 22. Small crithidial form suggestive of the nectonionad phase, with 

 nucleus well forward. 



Fig. 2:i. Very large crithidial type with nucleus far forward, rhizoplast 

 extending to nuclear membrane with granules on membrane, and granular 

 axostyle. 



Figs. 2-4-26. Slender crithidial types with posterior nucleus, attenuate an- 

 terior end, and small nuclei. 



Figs. 27, 28. Stouter crithidial types approaching the haptomonad phase. 



Figs. 29-.30. Small, stout, rectal haptomonads, granular axostyle in figure 29. 



Figs. 31-33. Transition forms from haptomonad phase to the rectal try- 

 l)aniform phase, showing progressive lateral and posterior migration of the 

 parabasal. 



Fig. 31. With axostyle, figure 32 with myonemes. 



Figs. 34—13. Rectal trypaniform stages, showing transformation of the 

 vesicular nucleus to the elongate, granular, asymmetrical nucleus. Note small 

 but variable parabasal. 



Figs. 45-47. Rounded-up haptomouad stages from the rectum. 



[126] 



