320 



PROTOZOOLOGY 



some, but with chromatin granules arranged along nuclear mem- 

 brane; 1 to many nuclei; cyst-nuclei formed by fragmentation 

 of those of the trophozoite and possess a large rounded chromatic 

 endosome, connected at one side with the nuclear membrane by 

 achromatic strands, to which chromatin granules are attached; 

 in stomach of salmonoid fish. One species. 



S. salmonis D. (Fig. 147, a, h). Sluggish amoeba; 10-25m in 

 diameter; 1 to several nuclei; multiplication by binary fission; nu- 

 clear division amitotic. Cysts are said to be more abundant than 

 trophozoites and their appearance seems to be correlated with 

 the amount of available food; cysts spherical, 15-35)U in diameter; 



Fig. 147. a, b, Schizamoeba salmonis, xSOO (Davis); c, d, Hydra- 

 moeba hydroxena (c, a heavily infected Hydra oligactis which lost its 

 tentacles, X70; d, section of an infected hydra showing a trophozoite 

 feeding on ectodermal cells, X350) (Reynolds and Looper); e, Para- 

 moeba pigmentifera with its nucleus in the center, X600 (Janicki). 

 • 

 cyst-membrane thin and nuclei vary from 3 to many; during en- 



cystment, chromatin bodies of trophozoite become collected in 

 several masses which then disintegrate and each chromatin grain 

 becomes the endosome of newly formed nucleus; cyst contents 

 divide sooner or later into 4-11 multinucleate bodies and the 

 whole increases in size; finally cyst-membrane disintegrates and 

 the multinucleate bodies become set free. Trophozoites are said to 

 occur in the mucous covering of stomach of host fish; cysts occur 

 in both stomach and intestine. Aside from the loss of certain 

 amount of available food, no pathogenic effect of the amoeba up- 

 on the host fish was noticed by Davis. 



Genus Hydramoeba Reynolds et Looper. Nucleus vesicular 

 with a large central endosome composed of a centriole (?) and 

 chromatin granules embedded in an achromatic mass, achromatic 



