Amebic Dysentery 



635 



tion is quite different from that seen in Entamoeba coli, and only 

 takes place when conditions are unfavorable to continued division. 

 It is accomplished by a peculiar nuclear budding, by which chromatin 

 granules or chronidia are pushed out from the nucleus toward the 

 ectoplasm, where they develop into new nuclei, about which the 

 cytoplasm collects until a distinct bud is formed and cast off as a 

 small but distinct new organism a. spore or bud. These when 

 separated are round or oval, measure 3 to 6 ^u in diameter, and are 



Fig. 259. Reproductive cycle of parasitic, ameba (Wenyon). The small 

 circle indicated by i, 2, 3, 3' and 3" indicated multiplication by schizogony or 

 binary division. The large circle indicated by 1-12, thesporogeny or sexual cycle. 

 The ameba having arrived at its full size (3) becomes encysted (4). The nu- 

 cleus then divides into two (5), each half expels a small fragment of nuclear 

 material (6), and when this has been effected, they conjugate (7) forming 

 a synkaryon. The synkaryon then divides into two, into four, and then 

 generally into eight (8-9-10-11-12) when the cyst ruptures, the spores are liber- 

 ated (i) and both cycles are again started. 



surrounded by a yellowish envelope, which resists drying and the 

 penetration of stains and chemicals. 



Craig gives a tabulation of the differential features of Entamoeba 

 coli, Entamoeba histolytica, and Entamoeba tetragena (Me infra). 



3. Entamoeba Tetragena (Viereck*). This organism resembles 

 Entamoeba histolytica more than Amoeba coli, but differs from it 

 in the mode of reproduction, the sporocysts containing four instead 

 of eight spores. 



* "Archiv. f. Schiffs. u. Tropenhygiene," 1907, n, i. 



