Dec. 13, 191S 



Activity of Soil Protozoa 



481 



sampling. In order to ascertain whether the soils contained cysts of 

 protozoa which would become active when conditions became favorable 

 after they had been examined, the soils collected at the third sampling 

 were water-logged with sterile tap water and allowed to stand in the 

 laboratory for 40 hours, when they were examined for motile protozoa. 

 (See Table II.) 



Table II. — Extent of protozoan activity in field soils under different conditions of 



moisture"' 



Lab- 

 ora- 

 tory 

 No. 



Soil treatment. 



Normal 

 moisture 

 content. 



Presence of active pro- 

 tozoa when soil sam- 

 ples were water- 

 logged.* 



Shale 



Sandy loam .... 

 Gravelly sandy 



loam. 



Clay loam 



Gravelly clay . . 



Clay loam 



Silt loam 



do 



Sandy 



Gravelly silt 



loam. 



Shale 



Gravelly silt 



loam. 



Silt loam 



Sandy loam .... 



Bare 



Orchard. . 

 Garden . . . 



Orchard. . 

 Meadow. . 



...do 



Wheat.... 

 Weeds .... 



Com 



Fallow. . . . 



Bare 



Wheat.... 



Com 



Vetch and 

 tomatoes 



25.07 



13-73 

 9. 62 



IS- 14 

 15-67 

 19.65 

 II. 22 

 13-42 

 11-34 

 10.93 



19.88 

 9. 60 



10. 90 



6.74 



S.C.tttF-t 

 S.C.ttF.tt 

 S.C.fF.t 



S.C.fF.t 

 S.CtttL-CtF.t 

 S.CtL.C.fF.t 

 S.C.tt F.t 

 S.C.ttL.C.fF.t 

 S.C.tt F.tt 

 S.C.tt F.t 



S.CtttL.C.tF.t 

 S.Ct F.t 



S.C.tt F.t+ 

 Do. 



o Under normal conditions and two and five days after a heavy rain no active protozoa were observed. 

 * S. C.= small ciliates; L. C.= large ciliates; F.= flagellates; A.=amebse; t=few; tt= several; ttt=many. 



The careful examination of the 1 4 soils in no case revealed any motile 

 protozoa, indicating that under the normal and even somewhat abnor- 

 mal conditions of moisture active protozoa did not seem to be present 

 in the soils examined. Several samples of standing rain water were 

 collected when the second and third samplings were made. Upon 

 examination all of the samples of water showed the presence of many 

 small ciliates and flagellates, which indicates that the protozoa are 

 active in accumulated water. In all cases where the 14 soils were 

 water-logged small ciliates and flagellates, and in some cases even large 

 ciliates, were present in the active state. The data presented in Table 

 II point to the fact that all ordinary soils contain cysts of protozoa, 

 and in the 14 soils examined the active organisms were not observed 

 until sufficient moisture was present. It would seem that if the pro- 

 tozoa did become active when the moisture content was higher than 

 it was at the time of the first sampling after the heavy rain, they re- 

 mained active but a very short period of time, as in no case were they 



