AMOEBAEA 205 



or the Mastigophora. In the present work they have been 

 placed in the latter group (p. 129). 



According to Calkins, four families are recognized here. 



With amoeboid and flagellate stages Family 1 Bistadiidae 



Amoeboid stage only 



With one or more nuclei of one type 



Free-living Family 2 Amoebidae 



Parasitic Family 3 Endamoebidae 



With a cytoplasmic "secondary nucleus" Family 4 Paramoebidae 



Family 1 Bistadiidae Doflein 



The Amoebaea placed in this family possess both amoeboid 

 and flagellate phases (diphasic). In the former, the organism 

 undergoes amoeboid movement by means of lobopodia and in 

 the latter the body is more or less elongated. Binary fission 

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

 members are diphasic organisms, in which the amoeboid stage 

 predominates over the flagellate. The amoeboid phase of this 

 family is frequently called the "limax amoeba" which under 

 cultural conditions may be changed into flagellated individuals, 

 as for example, by the addition of water to the culture medium. 

 Under natural circumstances, it is often exceedingly difficult 

 by observing amoebae to determine whether they belong to 

 this family or the family Amoebidae. 



There is a good deal of confusion with regard to the various 

 generic names created for the amoebae of the "limax" type. 

 Calkins' definition and difTerentiation are followed here. 



Genus Naegleria Alexeieff ( = Vahlkampfia Chatton and 

 Lalung-Bonnaire (in part) ; Wasielewskia Hartmann and 

 Chagas). Minute forms. The flagellate phase possesses two 

 flagella. The amoeboid phase is much similar to the genus 

 Vahlkampfia (family Amoebidae, p. 206), with lobopodia. The 

 cytoplasm is difTerentiated into the ectoplasm and endoplasm. 

 The vesicular nucleus contains a large endosome. There is 

 usually a conspicuous contractile vacuole. Food vacuoles con- 

 tain bacteria. Fission takes place in the amoeboid stage only. 

 Encystment is common; the cyst contains a single nucleus. 

 Free-living in stagnant water and moist soil; often coprozoic. 



Naegleria gniheri (Schardinger) (Fig. 79, a-c). Body about 



