AMOSBJ5 OF THE INTESTINAL TRACT. 199 



species may be distinguished by the amount and 

 arrangement of the nuclear chromatin, as has already 

 been described. 



METHOD OF REPRODUCTION. To one who cares to 

 devote the time and study necessary, the investiga- 

 tion of the methods of reproduction of the species 

 under discussion will definitely distinguish them. 

 While they all reproduce by simple division when 

 conditions are favorable to vegetative existence, they 

 differ widely in their methods of reproduction under 

 other conditions. Entamceba histolytica reproduces 

 by spore formation, the young spores being budded 

 off from the periphery of the mother organism, a 

 method totally different from that of Entamceba coU 

 which encysts, eight daughter amoebge being formed 

 within the cyst. Under the same conditions Enta- 

 mceba tetragena undergoes encystment, but only four 

 daughter amoebse are formed within the cyst. At a 

 certain stage in the development of Entamceba coli 

 the cyst contains only four nuclei and care must be 

 taken not to mistake this stage for the cysts of Enta- 

 mceba tetragena. These differences in the reproduc- 

 tive cycle are of the greatest importance in the differ- 

 entiation of species and whenever there is any doubt 

 concerning the nature of an amoeba present in a given 

 case the methods of reproduction should always be 

 studied. 



