STRUCTURE AND LIFE-HISTORY OF CRITHIDIA MELOPHAGIA. 201 



pierce the walls of the alimentary tract and make their way 

 to the ovaries of the ked, where their development is con- 

 tinued. 



Text-figtjres 1-10. 



a 9 10 



Encystment of Crithidia melopliagia in the rectum. 



Text-figs. 1-5. — Parasite rounding off and flagellum disappearing. 

 Text-figs. 6-7. — Show bending of parasite on itself. 

 Text-figs. 8-10. — Final stages in loss of flagellum and assumption 

 of typical cyst form. 



Swingle (1909, p. 104) has described thick-walled cysts. 

 I have but rarely seen the thick-walled forms (PI. 13, fig. 114), 

 most of the cysts found being thin-walled. 



