AMOEBINA 463 



Encysted stage has not been observed. Degenerating trophozoites 

 often develop vacuoles which coalesce into a large one and the or- 

 ganisms may then resemble Blastocystis hominis (p. 893) which is 

 very common in faeces. Transmission may be carried on by tropho- 

 zoites. According ot Wenrich (1940), this amoeba if left in the faeces 

 remains alive up to 48 hours at room temperature, but disappears 

 probably by disintegration in 2 hours at 3.5°C. Since all attempts 

 to bring about experimental infection by mouth or by rectum failed, 

 Dobell considered that the amoeba may be transmitted from host 

 to host in the eggs of nematodes such as Trichuris or Ascaris, as in 

 the case of Histomonas (p. 335). 



The amoeba inhabits the lumen of the colon. There is no indica- 

 tion that it is histozoic or cytozoic. Some workers attribute certain 

 intestinal disturbances to this amoeba, but no definite evidence for 

 its pathogenicity is available at present. It seems to be widely dis- 

 tributed, but not as common as the other intestinal amoebae men- 

 tioned above, although in some areas it appears to be common. Nu- 

 clear division (Wenrich, 1936, 1939, 1944a; Dobell, 1940). 



Genus Martinezia Hegner and Hewitt. The nucleus consists of a 

 wrinkled membrane, a large compact or granular endosome and 

 heavy peripheral beads; cysts unknown; parasitic. 



M. baezi H. and H. (Fig. 196, g, h). In the intestine of iguanas, 

 Ctenosaura acanthura; 8-21/* by 6.5-16/*; nucleus about 4/* in diame- 

 ter; two nuclei in about 3 per cent of the organisms; cysts not seen. 



Genus Dobellina Bishop and Tate. Trophozoite: small amoeba; 

 ectoplasm and endoplasm differentiated; usually monopodal; 

 nucleus one to many ; nucleus with a large central endosome and an 

 achromatic nuclear membrane; nuclear divisions mitotic and simul- 

 taneous; no solid food vacuoles; no contractile vacuole; with refrin- 

 gent granules. Cysts: spherical; thin-walled; devoid of glycogen and 

 of chromatoid bodies; 2 or more nuclei; parasitic (Bishop and Tate, 

 1939). 



D. mesnili (Keilin) (Fig. 198, a-c). Uninucleate amoebae as small 

 as 3.6/* in diameter; multinucleate forms 20-25/* by 10-15/*; cysts 

 8-11/* in diameter; in the space between the peritrophic membrane 

 and the epithelium of the gut in the larvae of Trichocera hiemalis, 

 T. annulata, and T. regelationis (winter gnats). 



Genus Schizamoeba Davis. Nucleus vesicular, without endosome, 

 but with large discoid granules arranged along nuclear membrane; 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 



