6o RESEARCH IN PROTOZOOLOGY 



gain access to feces either by contamination of the excrement after 

 passage or by the entry of encysted forms, via air, food, or water, 

 into the ahmentary canal. In the latter case, the organisms do not 

 emerge from their cysts within the intestine but excyst when the 

 contents have been voided. Dilution of the stool, particularly in 

 warm weather, favors the appearance of these forms. 



Ignorance or misapprehension of the bionomics of these pro- 

 tozoa has in some cases led to a confusion of them with parasitic 

 organisms or to a description of new species alleged to be entozoic. 

 In some instances, the contaminating organisms have been intro- 

 duced with the diluent used in making the smear. In order to guard 

 against mistakes of this nature, three things should be borne in 

 mind : ( i ) stools should be passed into containers which have been 

 freshly sterilized or whose interior has never been exposed (e.g., 

 the ice-cream containers recommended by Hegner and Taliaferro, 

 1924, p. 483), (2) the fluid used for diluting the stool for purposes 

 of examination should have been recently sterilized and kept free 

 from exposure, and (3) while it is not possible to prevent the oral 

 ingress of cysts and the consequent appearance of coprozoic tro- 

 phozoites in the feces, a coprozoic fauna may be distinguished 

 from a parasitic one by keeping the stool for a day or two and 

 observing the relative increase in the number of organisms which 

 will take place if they are of the coprozoic habit, or the decrease 

 and disappearance which will occur if they are truly entozoic. 



It is not known just how many species of free-living protozoa 

 can live readily in feces, but the number must be very great. In 

 this laboratory various species of Vorticella, Oxytricha, Stylony- 

 chia, Pleurotricha, Chilodon, Chilomonas, Colpoda, Euglena and 

 the "limax" amoebae have been repeatedly encountered in stale stool 

 cultures. Dobell (1921) has given a list of twelve organisms, most 

 of which have been noted frequently in human stools, as an 

 introduction to the subject. To his account the reader is referred 

 for illustrations, bibliography, and a more detailed description 

 than can be offered here. The following condensed descriptions of 

 very common forms are taken largely from Dobell and O'Connor 

 (1921) and Hegner and Taliaferro (1924). 



physiologically separate groups should exist as subdivisions of the coprozoa, 

 the writer does not feel qualified to say. The field might well be studied 

 with the view of introducing more precision into our understanding of the 

 bionomics of these very interesting protozoa. 



