938 



SCIENCE 



[N. S. Vol. XLII. No. 1096 



similarities of Entamosba coli Losch and E. 

 dysenterice Councilman and Lafleur, and their 

 long-standing confusion in the biological and 

 medical literature, notwithstanding the very 

 profound differences between them in their 

 relations to their human host, the one a harm- 



less parasite, the other a serious factor in dis- 

 ease. The conquest of amoebic dysentery was 

 conditioned by the discovery of the differences 

 between these two species, and the relations 

 of each to their common host. 



The relationship of Entammba huccalis to 

 Biggs' disease, or pyorrhea, is not only a prob- 

 lem in parasitism, but probably one also of the 

 commensal relationship of this ameeba and the 

 bacterial flora of the gingival abscesses. 



The remarkable and unique protozoan 

 fauna of the first and second stomachs of the 

 ox and other ruminants is composed of not 

 less than 6 genera and 24 species living to- 

 gether in closest proximity in a common 



mediimi, but their relationships to it are not 

 uniform. One species of the genus, Diplodin- 

 ium ecaudatum, is, for example, exclusively a 

 bacterial feeder (see Sharp, 1914), while 

 others in the same genus feed indiscriminately 

 on other components of stomach contents. 



Indeed it is not impossible that, as in the 

 case of pathogenic protozoa and bacteria, 

 there will be found to be strains or pure lines 

 within the species, whose ecological relation- 

 ships may be so different among themselves as 

 to lead to divergent conclusions regarding the 

 species. 



These facts lead to the inference that the 

 mass treatment of the protozoan fauna of the 

 soil without regard to its component species 

 will tend to obscure and confuse its relation- 

 ship to the bacterial and other flora, to the 

 chemical conditions related thereto, and to the 

 problem of sick soils and of fertility. 



In a recent survey of the literature on the 

 protozoa of the soil I have been struck by the 

 great divergence of results at the hands of 

 different investigators as to the nature and 

 extent of the protozoan fauna discovered by 

 direct examination and by culture methods. To 

 the student of the ecology of the protozoa this 

 divergence is to be expected in view of what 

 is known of the seasonal fluctuations in num- 

 bers and kinds of protozoa in the population 

 of reservoirs, ponds, lakes and streams. Ad- 

 jacent bodies of water may have a very differ- 

 ent seasonal history in these respects as I have 

 shown (1904, 1908) with regard to the plank- 

 ton of the Illinois River. Furthermore these 

 minute organisms are very susceptible to in- 

 finitesimally small doses of certain mineral 

 salts, notably copper sulphate. A treatment 

 of a reservoir with this salt to the amount of 

 only one part to ten million by weight will 

 completely kill out most flagellates having 

 chlorophyll in any of its forms in their organi- 

 zation and result in a total reorganization of 

 the microfauna and microflora of the body of 

 water thus treated, which persists for several 

 months at least. Add to the seasonal fluctua- 

 tions in heat and moisture and the local dif- 

 ferences in chemical composition, the access 

 of adventitious substances in rainfall, tillage, 

 fertilizers, flood waters and seepage, and it is 



