AMOEBINA 



305 



Amoeboid stage only 



With one or more nuclei of one kind 



Free-living Family 2 Amoebidae (p. 306) 



Parasitic Family 3 Endamoebidae (p. 312) 



With a 'secondary nucleus' Family 4 Paramoebidae (p. 321) 



Family 1 Dimastigamoebidae Wenyon 



The members of the two genera placed in this family possess 

 both amoeboid and flagellate phases {diphasic). In the former, 

 the organism undergoes amoeboid movement by means of lobo- 

 podia and in the latter the body is more or less elongated. Binary 

 fission seems to take place during the amoeboid phase only. Thus 

 these are diphasic protozoans, in which the amoeboid stage pre- 

 dominates over the flagellate. The amoeboid phase resembles a 

 'limax' amoeba; under natural circumstances, it is often exceed- 

 ingly difficult by observing the amoeboid stage only, to deter- 

 mine whether they belong to this family or the family Amoebidae. 



Genus Dimastigamoeba Blochmann {Naegleria Alexeieff). 

 Minute; flagellate stage with 2 flagella; amoeboid stage resembles 

 Vahlkampfia (p. 310), with lobopodia; cytoplasm differentiated; 

 vesicular nucleus with a large endosome; contractile vacuole con- 

 spicuous; food vacuoles contain bacteria; cysts uninucleate; 

 free-living in stagnant water and often coprozoic. 



Fig. 139. a-c, trophozoite, flagellate phase and cyst (all stained) of 

 Dimastigamoeba gruberi, X750 (Alexeieff); d-f, similar stages of D. 

 bistadialis, X750 (Kiihn); g-j, trophozoite, flagellate phase, cyst and 

 excj'station of Trimastig amoeba philippinensis, X950 (Whitmore). 



D. gruberi (Schardinger) (Fig. 139, a-c). Amoeboid stage 10- 

 50 fjL long; cyst wall with several openings; flagellate stage 10-30/x 

 long. 



