A HARMLESS AM(EBA OF MAN 151 



E. coli is a medium-sized amoeba, being 12 to 

 25 fjb in diameter when it is quiescent. When mov- 

 ing, the amoeba is fairly active, producing short, 

 blunt pseudopodia (Fig. 30, ps.) with some rapidity. 

 It has a peculiar greyish colour, and the round, 

 vesicular nucleus (Fig. 30, n.) is clearly visible in life. 

 The ectoplasm is best seen during movement, as the 

 pseudopodia, when first formed, are entirely ecto- 

 plasmic. The endoplasm is compact, and as a rule 

 vacuoles are absent or few, E. coli differing from some 

 pathogenic amoebae in this respect. Food debris 

 (Fig. 30, v.) and bacteria occur in the endoplasm, 

 but blood-corpuscles only occur there exceptionally. 

 The parasite seems to avoid blood-corpuscles as food, 

 and rarely, if ever, ingests them, even when supplied 

 with them in abundance another difference from the 

 known pathogenic forms. 



The multiplication of the Entamoeba occurs usually 

 by simple division into two daughter forms. The 

 nucleus, which has a well-marked membrane and a 

 central chromatin mass or karyosome, divides first 

 into two, and then the cytoplasm follows. Rapid 

 multiplication by schizogony also occurs. The 

 schizont withdraws its pseudopodia and becomes 

 roughly rounded. The nucleus increases in size, 

 and divides by a process of multiple fission until 

 there are eight daughter nuclei in the amoeboid 

 body. An eight-nucleate schizont is thus produced. 

 Internally the cytoplasm collects around each nucleus, 

 and the miniature amoebae thus produced separate as 

 eight merozoites. 



Under unfavourable conditions encystment occurs. 



