NOTES ON SOME METHODS FOR THE 

 EXAMINATION OF SOIL PROTOZOA. 



By C. H. martin, M.A., and K. R. LEWIN, B.A. 



(Rolhamsted Experimental Station.) 



(With Plates II and III.) 



I. Introduction. 



DuRiNCi the last three or four years, the protozoa of the soil have 

 been the object of a considerable degree of interest, and investigations 

 into their occurrence and importance have been made by workers here 

 and elsewhere. The aim of the present paper is to indicate what we 

 know of the life of the protozoa in the soil, and to furnish descriptions 

 of certain methods which have been found useful in work on this 

 subject. 



When attention was directed to the protozoan inhabitants of soils, 

 it was quickly found that protozoa in great numbers and variety were 

 easily obtained by inoculating soil into a suitable medium. Retting 

 out from this fact, investigators have frequently been led to describe 

 the forms found in cultures from a soil as the fauna of the soil, thus 

 making the more or less tacit assumption that every form found in 

 cultures from a soil was leading a trophic bfe in the soil at the moment 

 when the culture was made. 



Unfortunately, what may be termed the "cultural fauna" of a soil 

 is of relatively little value in forming an idea of the protozoa actually 

 living in the soil. On the one hand the cultural fauna consists in part 

 of protozoa which were present in the soil only as cysts ; on the other, 

 some forms relatively important in the soil, notably the thecamoebae, 

 appear very late, or not at all, in cultures on the ordinary media. 



The protozoa in any soil may occur in the active (trophic) state, or 

 enclosed in cysts. We propose to call the former the "active fauna." 

 and the latter the "cyst fauna" ; and we would emphasize the necessity 

 of keeping these two classes clearly distinguished. 



