Amebic Dysentery 



63s 



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, the sporogeny 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 (vide infra). 



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

 Entamoeba histolytica more than Amoeba coU, but differs from it 

 in the mode of reproduction, the sporocysts containing four instead 

 of eight spores. 



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



