AMOEBINA 351 



fission; mitotic figure a sharply pointed spindle. Cysts spherical; 

 10-15ju in diameter; with a smooth inner and a much wrinkled outer 

 wall; easily cultivated from old faeces of man and animals; also in 

 soil and fresh water. 



Genus Sappinia Dangeard. With two closely associated nuclei. 



S. diploidea (Hartmann and Nagler). Coprozoic in the faeces of 

 different animals; pseudopodia short, broad, and few; highly vacu- 

 olated endoplasm with 2 nuclei, food vacuoles, and a contractile 

 vacuole; surface sometimes wrinkled; the nuclei divide simultane- 

 ously; during encystment, two individuals come together and secrete 

 a common cyst wall; 2 nuclei fuse so that each individual possesses 

 a single nucleus; finally cytoplasmic masses unite into one; each 

 nucleus gives off reduction bodies (?) which degenerate; 2 nuclei 

 now come in contact without fusion, thus producing a binucleate 

 cyst (Hartmann and Nagler). 



Family 3 Endamoebidae Calkins 



Exclusively parasitic amoebae; the vegetative form is relatively 

 small and occurs mostly in the alimentary canal of the hosts; con- 



«) 



Fig. 164. Diagrams showing the nuclei of the trophozoites of 5 genera 

 of parasitic amoebae, a, Endamoeba; b, Entamoeba; c, lodamoeba; 

 d, Endolimax; e, Dientamoeba. 



tractile vacuoles absent, except in Hydramoeba; multiplication by 

 binary fission; encystment common. The generic differentiation is 

 based upon the morphological characteristics of the nucleus. Sum- 

 mary No. 99 of 'Opinions Rendered' by the International Commis- 

 sion of Zoological Nomenclature (1928) holds that Entamoeba is a 

 synonym of Endamoeba; in the present work, however, Endamoeba 

 and Entamoeba are separated, since the two groups of species placed 

 under them possess different nuclear characteristics (Fig. 164) and 

 since it is not advisable to establish another generic name in place of 

 Entamoeba which has been so frequently and widely used through- 

 out the world. 



Genus Endamoeba Leidy (1879). Nucleus spheroidal to ovoid; 



