All figures were outlined with a camera lucida, using 1/16 Leitz objective 

 and Zeiss ocular 12. The magnification is in all cases approximately 2880. 

 Unless otherwise stated, all figures in the plates were drawn from preparations 

 fixed with hot Schaudinn 's fluid and stained in iron haematoxvlin. 



EXPLANATION OF PLATE 1 



Crtthidia leptocoridis sp. nov., preflagellate stages 



Fig. 1. Spore forms from the stomach with only one nuclear mass showing. 



Fig. 2. Developing spores from stomach, nuclear structure indefinite, but 

 probably two chromatin masses present. 



Figs. 3-7. Non-flagellates of the stomach phase in several stages of devel- 

 opment. Nucleus and kinetonucleus are shown clearly in figure 7. Capsule-like 

 covering is still present in figures 6 and 7. 



Figs. 8-9. Flagellated forms of the stomach phase. The flagellum first 

 appears, then the undulating membrane. The nuclear structure is not clear 

 until further development takes place. 



Fig. 10. Non-flagellated form of the stomach phase, showing the nucleus, 

 "kinetonucleus," rhizoplast and basal granule. 



Figs. 11-13. Flagellated forms of the stomach phase developing into pear- 

 shaped organisms which move with posterior end directed forwards and enter 

 cellular masses in this way. They show the nucleus, "kinetonucleus," rhizo- 

 plast, basal granule, flagellum and undulating membrane. 



Figs. 14-24. Preflagellate forms found in the stomach. Peculiar relation 

 of two flagellates which cannot be explained as yet, but it is strongly sug- 

 gestive of sexual reproduction and apparently not due to a process of division 

 or an "accidental attachment" of the two forms. 



Figs. 25-26. Flagellates in the stomach preparing to round up to form 

 tailed spheres. Large vesicular nuclei and well developed " kinetonuclei" are 

 present. 



Figs. 27-28. Flagellates rounding up to form spheres in the stomach. 

 These are extracellular forms. 



[16] 



