SOIL PROTOZOA IN SOUTH AFRICA. 361 



in extremely small numbers only in cultures of the surface layer. 

 Similarly, the soil Hcrpcto]no)uis was confined to the sample of 

 soil taken at ten inches deep, which layer was one of the richest 

 of the series of thirteen in numbers of species of Protozoa, and 

 was also almost the richest in total numbers of organisms present. 

 One feature of greatinterest was the finding of certain Protozoa 

 in cultures of relatively deep soils. Euglena viridis and E. oxyuris 

 were recognised first as green cysts in which the stigma was quite 

 distinct. Morphologically, the cysts presented the same appear- 

 ance, no matter what the depth of soil in which they occurred in 

 the series. The maximum number of cysts, and later of motile 

 Euglenae, was found in cultures of soil taken at ten inches from 

 the surface, the numbers being considerably- larger than those 

 obtained in cultures of soil taken at four, five and six inches deep. 

 This niay result from (a) washing down hy rain of the maximum 

 number of cysts or motile Euglenae to the depth of ten inches, the 

 organisms then lodging there and the trophic forms encysting, or 

 [h) to selective action of the Euglenae, that migrate to deeper 

 soil for purposes of encystment. The latter factor seems possible, 

 especially considering the rare occurrence of other Protozoa, such 

 as the larger Ciliates, Sti/lonifchia niytihis and Uroleptus piscis, 

 in layers of soil near the surface, compared with the larger 

 numbers observed in the deeper layers of soil. 



The Rosebank Experiment Station is a convergence of the 

 natural drainage area of the Liesbeek Piver. There is kaolin 

 underneath the Posebank district, so that there is good penetra- 

 tion of water into the surface soil above the kaolin. The results 

 recorded for Rosebank in regard to the occurrence of Protozoa at 

 various depths can perhaps hardly be considered typical for areas 

 in general. 



A compari.son of the protozoal fauna of cultures of soil from 

 the Grootfontein School of Agriculture, Middelburg, C.P., taken 

 at six and nine inches deep, may be of interest (see Tables 

 III, IV). As a general statement, the Protozoa were more 

 numerous in soil at six inches deep than in soil at nine inches deep. 



The Virgin Red Karroo soil at nine inches deep showed 

 neither Amrebte nor Difflugia, both of which occurred at a depth 

 of six inches. Neither Bodo (Proicazckia) parva nor Euglena 

 viridis were ff>und at a depth of nine inches, though both were 

 present in cultures of soil taken at six inches. Of the Ciliata, 

 Lacryrnaria olor is common to both depths while Cyclidiiim 

 glaucoma was found only in the culture of the deeper soil. 



In the case of the Cultivated Red Karroo soils, no Heliozoa 

 were found in the deeper soil cultvires, nor was Euglena viridis 

 present. ('rrco)ii(ui((s crassicauda appeared there. Oikonurnas 

 termo and Bodo (P.) parva were common to each depth. The 

 Infusoria were different from those found in cultures of soil at six 

 inches deep, the latter being Lacryrnaria olor, Colpoda sfeinii or 

 saprophila and Spirosto)nur}i amhiguum. while at nine inches 

 deep the Ciliata were Cyclidium glaucoma and C'oleps /nVfus. 



As in the cultures examined and reported upon last year 

 (this JouHXAL, Vol. XVIII, pp. 379, 380), there is a great difference 



