262 WALKER. 



stage of Entamceba coli ; while it differs, according to Craig, from both species 

 in its life-cycle. Besides simple division there is a development of spores within 

 a ej'st which are set free as small flagellates. The cycle is completed by the 

 development of these flagellates into amoebae. This organism is believed by 

 Craig to be responsible for the diarrhoea from which the patients suffered. 



Entamoeba tetragina was first observed by Viereck (1907 ) in 2 cases of dysentery 

 from India and designated by him as Entama;ha tetragina. At nearly the same 

 time Hartmann (1907) found this amcBba in 11 cases of dysenteiy from Southwest 

 Africa, and South America. He considered it to be distinct from Entamoeba 

 histolytica, and gave to it the name Entamaba africana ; but subsequently, becoming 

 convinced of the identity of this amoeba with that of Viereck, he withdrew the spe- 

 cific name africana in favor of the prior name, tetragina Viereck. Werne (1908) 

 has also found this species in 9 cases of amoebic dysentery from Africa. More re- 

 cently Whitmore (1911) has found it to be a common species in the dysenteries of 

 the Philippine Islands and Indo-China. Entamoeba tetragina, according to these 

 authors, has the distinct, refrangent ectoplasm, tlie vacuolated entoplasi". the active 

 motility, and the pathogenicity of Entamoeba histolytica ; but the distinct nucleus 

 with a thick, nuclear membrane and rich in chromatin, characteristic of Entamoeba 

 coli. However, the nucleus of this species shows an arrangement of chromatin 

 which, according to Hartmann, is characteristic and which serves to distinguish 

 the vegetative stage from that of both histolytica and coli. In addition to tlie 

 peripheral chromatin there is constantly present a small caryosome which exhibits 

 cyclical changes and which in its most characteristic stage is made up of a 

 minute centriol and a concentric ring of chromatin granules separated by an 

 achromatic halo. This species, moreover, resembles Entamceba coli in its life- 

 cycle. There is a sporogony in the encysted stage, but with the difference that 4 

 instead of 8 nuclei are developed in the sporo-cyat. Entamceba tetragina is 

 considered to be a pathogenic species by all three authors. Hartmann found it 

 pathogenic for kittens, but considers it less pathogenic than Entamceba histolytica. 

 Sections of the intestine of experimentally infected animals showed a typical 

 ulcerative dysentery. 



Entamceba minuta was found by Elmassian (1909) in a case of recurrent 

 dysentery in a European who had resided in Paraguay, South America. It pos- 

 sesses in the living amoeba the indistinct nucleus of Entamceba histolytica ; but the 

 absence of a distinct ectoplasm, its sluggish movements, and its reproduction 

 by sporogony in the encysted stage are characteristic of Entamoeba coli; and 

 it is distinguished from both these species by its small size, averaging from 12 

 to 14 microns in diameter, and by the development of 4 instead of 8 nuclei in the 

 sporocyst. In this latter particular it corresponds with Entamceba tetragina 

 Viereck. Elmassian believes that both Entamoeba minuta and Entamceba coli may, 

 under certain conditions, become pathogenic. 



Entamoeba nipponica was observed by Koidzumi (1909) in Japan, at first 

 together with Entamceba histolytica in advanced cases, later in early cases of 

 amoebic dysentery, and also in dysentery of bacillary origin. This species cor- 

 responds with Entamoeba histolytica in possessing a well differentiated ectoplasm, 

 a vacuolated entoplasm, a thin nuclear membrane, and the capacity for injesting 

 red blood corpuscles, but with Entamoeba coli in the richness of its nucleus in 

 chromatin and in reproduction by schizogony in the vegetative stage; but it 

 differs from all other species hitherto described in the arrangement of the 

 chromatin in the forms of 3 to 8 discrete clumps on the inner surface of the 

 nuclear membrane. Sporogony in the encysted stage was not observed. This 

 species is considered non-pathogenic by Koidzumi. 



