1924] Kessel: Amofhac of Ciiltiirc Rats and Mke 491 



Brug (1919) concluded that the amoebae of the rats, idi'iititicd 

 a-s Mus rattus, and of the mice examined by him were identical, and 

 that their resemblances to Endamoeba coli were close, the greatest 

 difference being in the size. His figures indicate that he was dealing, at 

 least for the most part, M-ith the species Council mania- decumani. 

 Rudovsky (1921) described and figured an amoeba found in five rats of ' 

 the species Mies decumanus Pall., which is a synonym for Ra.ftus nor- 

 vegicus (Erxleben). Their figures show that Rudovsky and Brug have 

 described an identical species. Rudovsky, however, drew a morpho- 

 logical distinction between Endamoeba coli and the amoeba of the 

 mouse, which he described as having a heavy nuclear membrane, a 

 large karyosome, and little outer chromatin; and also, between these 

 two amoebae and the amoeba of the rat, which he described as having a 

 thin nuclear membrane, small granules of peripheral chromatin, and 

 a small karyosome. He speaks of this amoeba of the rat as Endamoeba 

 mitris decumani. 



In our own work, following investigations, first of an amoeba of the 

 mouse and then of an amoeba of the rat, it was thought that there was 

 a difference between the morphological characteristics of the two 

 amoebae. But a second lot of rats produced amoebae identical in all 

 respects with the amoeba found in the mouse. For a time it seemed 

 that the differences noted in the first rats examined represented differ- 

 ent pha-ses of the same life cycle, but further investigation has led to 

 the conclusion that there are at least three species of amoebae parasitic 

 in the intestine of culture rats and mice. 



For reasons to be stated later, these three species of amoebae should 

 be classified as Councilmania muris (Grassi, 1881, emend. Wenyon, 

 1907) Kessel emend.; the species Councilmania decumani (Rudovsky, 

 1921) Kessel, emend.; and Endamoeba ratti, sp. nov., a species having 

 granular pseudopodia and found, to date, only in the rat. 



ACKNOWLEDGMENTS 



The writer is greatly indebted to Professor C. A. Kofoid, under 

 whose supervision the M'ork here presented has been completed; to 

 Dr. E. L. Walker of the Hooper Foundation, who has offered many 

 helpful suggestions; and to Dr. Olive Swezy, who has been generous 

 in extending many courtesies. The work of the past year has been 

 made possible by the writer's appointment as University Fellow in 

 Zoology. 



