100 PARASITIC AMOEBJS OF MAN. 



which can be compared in activity with that com- 

 monly observed in the two other species mentioned. 

 Reproduction. Before Schaudinn's researches 

 little was known regarding the exact methods of 

 reproduction of the amoebae occurring in the human 

 intestine. A few observers had roughly described 

 certain reproductive phenomena, but as they were 

 unable to distinguish species their descriptions are 

 confused and of little value in the study of this sub- 

 ject. Celli and Fiocca, working in all probability 

 with Entamceba coli, described the life cycle as con- 

 sisting of an amoeboid stage, a resting stage and an 

 encysted stage, but their descriptions are incomplete, 

 and it was not until the work of Casagrandi and 

 Barbagallo appeared that the exact method of repro- 

 duction in Entamceba coli was known. They described 

 simple division and the formation, under certain con- 

 ditions, of cysts in which eight young amoebae devel- 

 oped. Their work was confirmed and extended by 

 Schaudinn, who found that reproduction during the 

 vegetative stage occurs by simple division and by 

 schizogony, with the formation of eight daughter 

 amoebae. When conditions are unfavorable for vege- 

 tative existence cysts are formed in which eight young 

 amoebae are developed. Complicated nuclear changes 

 occur during schizogony and development within the 

 cysts, which are best studied in preparations kept 



