PROTOZOA. 



ectosarc, produced by circular or spiral muscle fibrillae. These 

 muscles explain the peristaltic motion and the occasional sharp 

 bending of the body, but not the peculiar gliding motion like that 

 of diatoms by which locomotion is usually effected. This is 



pm. 



I. 



en. 



FIG. 155. Development of Gregarina blattarum. I, conjugation ; II, A-C, a cyst in 

 transformation into pseudonavicellae; III, A, a pseudonavicella greatly enlarged; 

 B, same with sickle-formed sporozoites; CM, cuticle; dm, deutomerite; ek, ecto- 

 sarc; en, entosarc; ?i, nucleus; pm, protomerite; pn, pseudonavicellae; rJc, re- 

 sidual body; sfc, sickle-form sporozoites. 



explained by the view that the gregarines secrete stiff gelatinous 

 threads from the posterior end, and the elongation of these forces 

 the body forward. 



In many gregarines (Poly cyst idae) the body is divided by a cir- 

 cular incision into a smaller anterior part, the protomerite, and a 

 larger deutomerite. Internally this division is marked by a bridge 

 of ectosarc across the entosarc. The vesicular nucleus (there is 

 but one in any gregarine) lies in the deutomerite. An epimerite 

 a structure connected with the peculiar type of parasitism occurs 

 in many species. All gregarines are parasitic in youth inside of 

 cells. They later leave these, but many remain for a long time 

 with a process of the protomerite imbedded in the cells. This 

 process the epimerite is provided with threads or hooks for 



