44 MANUAL OF HUMAN PROTOZOA 



like body lying across the axostyles near the posterior third 

 of the body. The four pairs of flagella are usually arranged 

 in the following manner: The anterior pair are inserted 

 in the blepharoplasts located near the anterior end of the 

 axostyles, cross each other near the anterior tip of body, 

 follow the antero-lateral margin of the sucking disc, and 

 become free flagella. The second pair originate in the an- 

 terior part of the axostyles, travel backward along the 

 latter structure, and become divergent by following part- 

 ly the inner posterior margin of the sucking disc, leaving 

 the body about one-third from the posterior end. The third 

 (ventral) pair are thicker than others, and originate in the 

 axostyles at points behind the disc, remaining free through- 

 out. The fourth (caudal) pair arise from the posterior tips 

 of the axostyles. 



Cysts 



1. Lwing specimens. The cyst (Fig. 11, 5) is ovoid in 

 form and refractile. It measures 8-14m by 6-10^. The cyst 

 wall is thin, but distinctive, and there is ordinarily a nar- 

 row space between it and the inner protoplasmic mass. 

 Two or four rings and fibrils may be faintly seen. They are 

 the nuclei, axostyles, fibrils of sucking disc, and some of 

 the flagella. With Lugol's, these structures are more clear- 

 ly visible. 



2. Stained specimens. In stained cysts (Fig. 11, 6-8)^ the 

 cyst wall is distinctly visible. Separated from it, is a granu- 

 lated ovoid body of the flagellate. A young cyst contains 

 two nuclei, each of which divides once, so that an older 

 and mature cyst is tetranucleate. The axostyles, fibrils, 

 flagella, are usually stained conspicuously. 



