1924] Kcssel: Amoebae of Cidtitre Rais and Mke 531 



experimental infection in old animals that have previouslj- been 

 determined to be amoeba-free. 



10. The fact that the amoebae common in the digestive tract of 

 rats and mice may be transferred by experimental infection from one 

 species of rodent to another without immediate morphological or 

 racial change, and also that the common amoebae of the human diges- 

 tive tract may be transferred to rodents without noticeable morjiho- 

 logical change affords valuable evidence : 



(a) In favor of the morphological constancy of species of parasitic 



forms. 

 (6) Against the theory of host specificity of parasites. 



11. The fact that all rats of known positive amoebic infection that 

 have been fed on a milk diet for two weeks have cleared themselves of 

 infection while only 27 per cent of the control rats fed on table scraps 

 have been cleared of infection indicates that a diet of milk only is for 

 some reason antagonistic to the normal amoebic infection of the rat. 



Permanent slides, representing paratypes of species Council mania 

 muris, Councilmani-a decumani, and Endamoeba ratti are deposited 

 in the laboratory of the Department of Zoology, Universit.y of 

 California. 



Zoological Laboratory, 



University of California. 



Transmitted Septeviber 4, 19S3. 



LITERATURE CITED 



Balfour, A. 



1922. Observations on wild rats in England, with an account of tlieir ecto- 



aud endoparasites. Parasit., 14, 282-298, pis. 23-24, 2 figs, in te.Kt. 

 Brug, S. L. 



1919. De entamoeben van de rat. Geneesk. Tijd. Ncderlandscli-Indie, 59, 



1-1.5, pi. 1-2. 

 BtJTSCHLI, 0. 



1878. Beitriige zur Kenntniss der Flagellateu und einiger verwandten 

 Organismen. Ztsclir. wiss. Zool., 30, 206-281, pis. 11-1.5. 



Cannon, P. B., and McNease, B. W. 



1923. Factors controlling intestinal bacteria. The influence of hydrogen-ion 



concentration on bacterial types. ,lour. Inf. Dis., 32, IT.VISO. 

 Chatton, E. 



1917. L'eclosion des kystcs et les premiers stades de revolution de I'amibe 

 dysenterique humaine chez le chat. Bull. Soc. Path. Exot., 10, 

 834-841, 9 figs, in text. 



