AMOEBAEA 



207 



extent. Holozoic on Protophyta, Protozoa, Rotifera, and in a 

 few cases even Nematoda. The endoplasm contains crystals 

 which are enclosed in vacuoles and which possess form and size 

 characteristic of various species (Schaeffer). These crystals 

 seem to be composed of calcium phosphate and probably meta- 

 bolic products. Numerous species. 



Amoeba proteus (Pallas) (Fig. 80, a-d). A widely distributed 

 large amoeba living in fresh water, reaching often 600 microns 



s% 



^,fe,:Ari:^ 



m 



Fig. 80 a-d. Amoeba proteus. (After Schaeffer, except d). a, an active 

 trophozoite (XlOO); b, typical form of crystal ; c, eight nuclei in 

 optical section; d, encysted form (after Doflein). 



e-g. Amoeba discoides. (After Schaeffer). e, active trophozoite 

 (XlOO); f, typical crystal; g, five nuclei in optical section. 



h-j. Amoeba dubia. (After Schaeffer). h, active trophozoite (XlOO); 

 i, various forms of crystals found in it; j, two nuclei in optical 

 section. 



or more in diameter. The amoeba creeps with a few large lobo- 

 podia, but floating individuals may possess a large number of 

 short blunt lobopodia which show longitudinal ridges. The 

 differentiation of the cytoplasm into two regions is usually 

 distinct. One nucleus occurs in each individual and is charac- 



