SOIL PROTOZOA IN SOUTH AFRICA. 38/ 



twenty-four hours, Pleuromonas jaculans was seen once only in 

 a six hours' culture, while in water cultures of five other soils it 

 did not appear until after twenty-seven days had elapsed. 



Ciliate Infusoria appeared in cultures either concurrently with 

 or usually rather later than Mastigophora. The shortest period of 

 culture before motile Ciliates were detected was nineteen hours, 

 the Ciliates being Spirostomum ambiguum and Col pidium steinii. 

 As in the case of Mastigophora, the period for excystation showed 

 much variation. Thus Lacrymaria olor appeared in a series of 

 cultures of different soils in thirty-one hours, forty-seven hours, 

 eight days, nine days and thirteen days respectively. In 

 the latter cases several generations may have occurred before they 

 were noticed. 



Occasionally one specimen of a Ciliate would be observed after 

 a short period of culture, and then no further specimen would be 

 seen for several days. Thus Goleps hirti/s first appeared in a 

 certain culture after three days, as did Lacrymaria olor in another. 

 Both organisms were not seen again for over a fortnight. Again, 

 Cyclidium glaucoma was observed in one culture twenty-four 

 hours after it was made. The organism disappeared from the cul- 

 ture and was not seen again for thirty-one days, when it reappeared 

 in fair numbers. 



In connection with the Sarcodina, it has been unusual in the 

 cultures of soils hitherto examined to find trophic forms early in 

 the cultures, though occasionally this has occurred. Usually 

 Amoebae and Thecamoebae were the last groups of organisms to 

 appear, though much variation was shown in this respect in dif- 

 ferent soil cultures. Thus, iu soils from Potchefstroom and Cedara 

 Amoeba Umax was found in a two days' old culture, it occurred 

 in a three days' old culture of Cedara cultivated soil, but was not 

 observed until nine days in a culture of Heathfield soil, twenty-four 

 days in Stellenbosch soil, and twenty-six days in soils from St. 

 James and Sinionstown. In some cultures as long as three months 

 have elapsed before an amoeba was detected. 



It is clear that dogmatic statements cannot be made, as soils 

 vary much among themselves. We are glad to note that similar 

 ideas regarding variability of factors have already been put forward 

 by Martin and Lewin. 



When first we attempted a determination of the number of 

 species of Protozoa found, which was done after twenty-three soils- 

 had been examined, we considered that the Ciliates were the most 

 numerous, Flagellates next and Sarcodina least, which observation 

 corroborates that of Fellers and Allison. After examining a few 

 more soils, making twenty-seven in all, it was found that eighteen 

 species of Ciliates, ten of Flagellates, and twelve of Sarcodina had 

 been found and identified. The relative positions of Flagellates 

 and Sarcodina as regards number of species thus were interchanged. 



The relative numbers of individuals of each of these groups 

 varies, and from the point of view of actual total numbers, Flagel- 

 lates are preponderant. 



