AMOEBINA 



465 



occur in one week. Encystment takes place soon after the death of 

 the host or occasionally when the organisms become detached from 

 the host; cysts are spherical, measure 27.5-29m, and contain one or 

 more nuclei, nematocysts and a large vacuole (h). Nuclear division 

 (Reynolds and Threlkeld, 1929). 





Fig. 198. a-c, Dobellina mesnili (Bishop and Tate) (a, b, stained uni- 

 and multi-nucleate trophozoites, X2200; c, a stained cyst with six nu- 

 clei, X1760); d, e, stained trophozoite and cyst of Schizamoeba salmonis, 

 X1070 (Davis); f-1, Hijdramoeba hydroxena (f, h-1, Ito; g, Reynolds and 

 Looper) (f, a trophozoite in life, X330; g, a trophozoite feeding on ecto- 

 dermal cells of a Hydra in section, X470; h, a living cyst, X530; i-1, 

 stages of infection in Hydra, X6.5); m, Paramoeba pigmentifera with its 

 nucleus in center, X800 (Janicki). 



Family 4 Paramoebidae Poche 



Genus Paramoeba Schaudinn. The amoeba possesses a nucleus and 

 nucleus-like secondary cytoplasmic structure, both of which mul- 

 tiply by division simultaneously; free-living or parasitic. 



P. pigmentifera (Grassi) (Fig. 198, m). About 30/x long; sluggish; 



