THE GREGARINES AND COCCIDIA 



329 



of the Acephalina, the latter of the Cephalina. In either case, 

 the first effect of the parasite is to produce a hypertrophy, often 

 very great, of the cell attacked (Fig. 143, B] ; later, however, the 

 cell atrophies, dies, and shrivels up (Fig. 143, C). 



(a) In the Acephalina the intracellular parasite is set free from 

 the cell by its dissolution, and, if lodged in the epithelium of the 

 gut, may pass out of the epithelium either on its inner side, into the 

 lumen of the gut again, or on its outer side, into the bloodvessels 

 or body-cavity. 



(6) In the Cephalina the relation of the parasite to the host- 



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A B 



FIG. 143. Lankesteria ascidia, parasite of Ciona intestinalis. 



A, Young intracellular stages in the intestinal epithelium ; 



B, older intracellular stage ; G, extracellular trophozoite 

 attached by a process of the anterior end of the body to 

 a withered epithelial cell, ep., Normal epithelial cell ; ep. '', 

 hypertrophied epithelial cell containing (G. )the young grega- 

 rine ; n., nucleus of normal cell ; n/, nucleus of infected cell. 

 After Siedlecki, magnified 750. 



cell varies greatly, and has been studied in detail by Leger and 

 Duboscq (618 and 620). The sporozoite may merely prick the 

 surface of an epithelial cell with its rostrum (e.g., Pterocephalus) , 

 or may dip a short stretch of its anterior end into the cell (e.g., 

 Pyxinia), or may penetrate so far that the nuclear region of the 

 parasite is within the cell (e.g.,Stylorhynchus), or, finally, may become 

 completely intracellular (e.g., Stenophora) . Ultimately, in all cases, 

 the chief mass of the body of the gregarine projects from, or grows out 

 of, the host-cell into the cavity of the digestive tract, and becomes 

 the protomerite and deutomerite in septate forms ; the attached 



