INTRODUCTION 19 



. 1920 The discovery of the intestinal Protozoa of man. 



Proc. Roy. Soc. Med., Vol. 13. 

 DOFLEIN, F. and E. Reichenow. 1929 Lehrbuch der Proto- 



zoenkunde. Jena. 

 NoRDENSKiOLD, E. 1928 The history of biology. New York. 

 Sandon, H. 1927 The composition and distribution of the 



protozoan fauna of the soil. Edinburgh. 

 Whipple, G. C. (revised by G. M. Fair and M. C. Whipple) 



1927 The microscopy of drinking water. Fourth ed. 



New York. 



