386 SOIL PROTOZOA IN SOUTH AFRICA. 



nesburg. It was was collected on 14th December. The following 

 protozoal organisms were found in one-fifth c.c. of ooze: — 



Rhizopoda. — 2 A moeba radiosa. 



Mastigophora. — 14 Bodo parva. 



Infusoria. — 1 Cole pa hirtus, 3 Cyelidium glaucoma, 5 

 Vorticella campanula. 



Specimen 5. — This was collected from flooded mealie land near 

 Johannesburg on 2nd December. On direct examination of ooze 

 •only motile Euglena viridis were found, but Bodo parva, 

 •Oikomonas termo and Paramoecium aurelia, as well as Euglena 

 viridis, were subsequently obtained in cultures, which also con- 

 tained some active Vibrios. 



Water cultures of each of the five waterlogged soils usually 

 yielded the same organisms observed on direct examination, and in 

 addition Oikomonas termo and Bodo parva appeared when pre- 

 viously not present in the trophic form. 



From the foregoing it appears that trophic Protozoa are present 

 normally in waterlogged soils, where cysts have also been observed, 

 while in soils with the ordinary water content (frequently only 

 hygroscopic moisture) the Protozoa seem to exist chiefly in the 

 ■encysted condition, trophic forms only being detected in water 

 cultures. 



Appearance and Periodicity of the Protozoal Organisms 

 Observed in South African Soils. 



From the examinations mentioned before it is seen that all the 

 soils examined so far in South Africa have contained Protozoa, 

 the majority often occurring naturally in the encysted condition. 

 Some organisms, such as Paramoecium, Cyelidium, were common 

 to several of the soils, while other soils showed quite different 

 genera, but the relative abundance of any one organism in the 

 •different soils showed considerable variation. 



Occasionally, sudden crops of Protozoa appear, which disappear 

 as suddenly. For example, a culture of soil collected at St. James 

 was made on 31st March, 1921. Actinophrys sol appeared 43 days 

 after the culture was made (that is, on 13th May). They were 

 •abundant for fourteen days, during which time apparent conjuga- 

 tion was observed. After this they continued to flourish for six 

 days, and then began decreasing in number. They disappeared 

 (possibly encysted) on 16th June, that is, 34 days after their first 

 appearance, to reappear in very small numbers one week later. 

 Since then they have not been observed in the culture. 



Mastigophora were usually the earliest Protozoa to appear in 

 -any number in cultures. Sometimes trophic Oikomonas termo and 

 Euglena viridis have been observed in as short a period as three 

 hours after culture, though none could be detected except as cysts in 

 •direct examinations prior to culture. Usually motile Flagellates have 

 appeared in soil cultures, other than as isolated units, after about 

 two days. Certain Mastigophora have developed in cultures long 

 before others. Thus, Oikomonas (Monas) termo was observed 

 .after three bours' culture, Euglena viridis was detected after 



