AMOEBINA 



313 



pseudopodia, show a distinct differentiation of cytoplasm; elon- 

 gated forms with a few pseudopodia, show ectoplasm only at the 

 extremities of the pseudopods; endoplasm of actively motile troph- 

 ozoites shows a distinct striation, a condition not often seen in 

 other amoebae; fluid-filled vacuoles occur in large numbers; 

 amoebae feed on starch grains, yeast cells, bacteria and proto- 

 zoans, all of which coexist in the host organ; cysts commonly 



Fig. 143. Endamoeha blattae. a-c, X530; d-f, X700 (Kudo). 



seen in the colon contents, with often more than 60 nuclei. The 

 life-cycle of this amoeba is still unknown. Mercier (1909) held 

 that when the multinucleate cysts gain entrance to the host in- 

 testine through its mouth, each of the cyst-nuclei becomes the 

 center of a gamete; when the cyst-membrane ruptures, the gam- 

 etes are set free and anisogamy takes place, resulting in forma- 

 tion of numerous zygotes which develop into the habitual tropho- 

 zoites. Among the more recent investigators, Morris (1936) is 



