EXPLANATION OF PLATE 4 



Crithidia leptocoridis sp. nov., postflagellate stages 



Fig. 74. Free rectal form, showing great widtli of body, nuclear network 

 and chromosome-like granules in the nucleus, rhizoplast, and a myonemie fiber 

 running along the nuclear membrane, thence to flagellum. 



Fig. 75. Free rectal form, showing a so-called longitudinal canal, a rhizo- 

 plast and "axostyle" are both present. There is also a chromatin granule 

 at the base of the "axostyle." 



Fig. 76. Free rectal form preparing for division. Nucleus shows two 

 chromatin masses and a spindle-like structure, within the nuclear membrane. 



Figs. 77-79. Large, spherical, rectal forms with vesicular nucleus. In 

 figures 77 and 78 the chromatin material stains lightly, indicating possibly a 

 degenerate form. 



Fig. 80. A free rectal form undergoing division. Cytoplasm is vacuo- 

 lated. 



Fig. 81. A free rectal form. Nucleus is elongated, posterior end of body 

 is very blunt and the ' ' axostyle ' ' line extends around the posterior end. 



Figs. 82-86. Free rectal forms. Figure 83 shows many small granules 

 within the nucleus. All these forms show the vesicular nucleus with a rhizoplast 

 connecting the nucleus and the "kinetonucleus." 



Figs. 87-90. Free rectal forms preparing for encystmeut. The flagellum is 

 coalescing with the body and later disappearing. A shrinking of these forms 

 also shown here. 



Figs. 91-92. Free rectal forms, showing the flagellum almost entirely ab- 

 sorbed, especially in figure 92. 



Figs. 93-97. Attached flagellates of the lower part of the rectum. Ee- 

 duced size due to continued longitudinal division and to a change in shape. 

 Undulating membrane almost absent. Rhizoplast clearly shown but ' ' axostyle ' ' 

 can not be demonstrated. Nucleus relatively large. 



Figs. 98-99. Attached rectal forms which have become free just prior to 

 encystment. 



Figs. 100-104. Free rectal forms encysting. The rhizoplast is still present 

 and flagellum is rapidly disappearing. The nucleus is relatively large and 

 vesicular. 



Figs. 105-108. Final stages in spore formation in rectum. Spores have a 

 thick protective covering and apparently a single chromatin mass in the 

 center. 



[22] 



