524 University of Culifoniia Puhlirafions in Zoology [^'ol. 20 



podia cannot belong to the same species as an amoeba that forms granu- 

 lar pseudopodia. This difference alone should be suificient evidence 

 for the establishment of a new species. 



During this investigation, an amoeba has been encountered in the 

 intestinal tract of the rat which moves by the formation of granular 

 and coarsely vacuolated pseudopodia. Except in very rare instances, 

 when the amoeba is very sluggish in movement and for the most part 

 rounded, when a narrow hyaline margin of ectopla.sm may occur for 

 an instant only, this amoeba shows absolutely no differentiation 

 between ectoplasm and endoplasm. It ha.s never been observed to 

 form a pseudopodium, completely hyaline, which is the only type of 

 pseudopodium ever observed in Council niania. The type of pseudo- 

 podial formation observed in this amoeba resembles that described by 

 Dobell (1921) for E. coli. 



The nuclear structure of this amoeba also differs from the nuclear 

 structure of Councilmania in that the karyosome is solid rather than 

 diffuse. It further- differs from species of amoebae found in the rat 

 that belong to the genus Councilmania in that reproduction by bud- 

 ding from the cyst in the caecum has not been observed in it. Because 

 of these differences, it is concluded that this species of amoeba cannot 

 be placed in the genus Councilmania. 



Since the pseudopodia are of the granular type and since the 

 karyosome is massed and excentrie, as in the type species E. blattae 

 (Biitschli) and also in E. coli (Losch), we conclude that this amoeba 

 from the rat should be placed in the genus Endamoeba. 



This amoeba found in the rat differs from E. coli of man in size 

 and in the type of chromatoidal body, which simulates the chroma- 

 toidal body of C. decumani more than the chromatoidal body of E. coli. 

 There is also less tendency for the chromatin material encrusted on the 

 nuclear membrane to arrange itself in a bead-like structure. It is 

 usually encrusted in a solid ring, or in granides spaced widely apart. 

 This, however, may be physiological rather than specific. Because of 

 these differences between the amoeba possessing granular pseudopodia 

 that is found in the rat and E. coli of man, it is proposed to call this 

 amoeba Endamoeba ratti sp. nov. 



Pseudopodial formation. — The structure of the protoplasm and the 

 type of pseudopodia formed by the various amoebae, both free-living 

 and parasitic, must be associated with the biochemical construction 

 of the protopla.sm of which the specific amoebae are composed. It 

 has been suggested by some investigators that the difference in pseudo- 



