170 University of California Puhlications in Zoology ["Vol. 20 



The intensive study of the protozoan infections of the human diges- 

 tive tract incident to the prevalence of dysentery during the late war 

 among troops on the Western, and especially the Near Eastern fronts, 

 has clearly established the unexpectedly wide distribution of amoebic 

 infections in man. 



In the case of these amoebae the confusion is increased by the 

 existence of no less than six different valid species of amoebae in 

 human stools and of size races within some, if not all, of these. These 

 are the three common species: Endamoeba dysenteriae (Councilman 

 andLafleur), Endamoeba coli (Losch), Endolimax nana (Wenyon and 

 O'Connor), and the rare Dientamoeba fragilis (Dobell and Jepps). 

 We have recently found a clearly established ease of human infection 

 with a fifth amoeba called Entamoeba muris (Grassi) by Brug (1919), 

 which Brug and ourselves find to be a normal parasite of wild and 

 culture rats. Under Endolimax nana we include tentatively the form 

 known as the "iodine body" which we regarded (see Kofoid, Korn- 

 hauser, and Swezy, 1919) as the large glycogen-bearing race of Endo- 

 limax nana. 



In connection with Endamoeba coli some differences of opinion 

 and of observation still persist with regard to its activities, structure, 

 and life history. Specifically these concern the appearance of the 

 pseudopodia, the rapidity of formation of pseudopodia and of move- 

 ment, the ingestion of red blood corpuscles, pathogenicity, the struc- 

 ture of the karyosome, and the formation of amoebulae by a process 

 resembling budding from cysts in the stools. These debated points 

 we hope will be cleared up by the evidence here presented that there 

 is in man another amoeba hitherto undescribed and heretofore con- 

 fused with Endamoeba coli, primarily because of its eight-nucleated 

 cyst. 



It is the purpose of this paper to describe this sixth species of 

 amoeba from the human intestine, which may be present in enormous 

 numbers, appears to have pathogenic capacities, and has apparently 

 been passed over as E. coli because of its large size, its eight-nucleated 

 cyst, and its high resistance to stains, all of which tend to obscure its 

 distinctive characteristics. 



We take pleasure in naming this amoeba Councilmania lafleuri, in 

 recognition of the critical discovery in 1891 by these two investigators 

 of the relation of the amoeba called by them Amoeba dysenteriae to 

 dysentery and hepatic abscess, a landmark in the medical conquest of 

 this widespread infection of man. 



