SOIL PROTOZOA IN SOUTH AFKICA. 365 



(8) Culture of soil from Onderstepoort. 



Surface film. — A)nceba proteus, ()iko})io)ias termo, 



Uroleptus piscis, all in small numbers. 

 Middle layer. — CycUdium glaucoma, HoJoplirya ovum, a 



single specimen of each. 

 Soil layer. — Eugiypha sp., OikoDwnas tcr))io, CycUdnim. 



gkiucoiiia, and Holophnja ovum in small numbers. 



From these preliminary experiments, it seems that the con- 

 clusion may be provisionally reached that Amoebae occur more 

 commonly in the surface film of water and C'iliates are more 

 abundant in the soil layer. Possibly these Amoebae are more 

 lerobic than the Ciliates. These ideas are borne out by other 

 observations, and, in estimating the numbers of organisms in any 

 one culture, we have always endeavoured to examine samples 

 including surface film, middle layer and soil layer. 



Sequence of Appearance of Protozoa in Cultures of Soil from 

 Different Depths. 



A series of observations was made on the sequence of appear- 

 ance of the different Protozoa in cultures of Rosebank (Liesbeek) 

 soil taken at successive inch depths, the soils being mmibered 1 to 

 12, as previously, and l3 being a composite sample. The Protozoa- 

 found therein have ah*eady been listed in Table II. The day of 

 culture on which each Protozoon first appeared at any given depth 

 is indicated in Table V by a number in the column opposite its 

 name (see next page). The period of observation extended over 

 93 days. 



From consideration of Table V, several inferences may be 

 made in regard to sequence of appearance of Protozoa in cultures 

 and to the succession of the Protozoa in any one soil. Thus, the 

 Flagellata, Oikomonas termo, Bodo (P.) parva and PJevromonas 

 jaculans appear in most of the depth cultures at really earh^ 

 dates, though there are exceptions in each case. On the other 

 hand, the Flagellate, Peranema tncliOipJiorain , approaches 

 more nearly to the Rhizopoda in its date of appearance ; its 

 earliest appearance being 44 days after culture, while it has 

 appeared 88 days after the culture was made. When Euglena 

 viridis and E. oxyuris have occurred in the same culture, E. 

 viridis has appeared a good deal earlier than E. oxyuris. It has 

 also died out sooner. 



As a general statement, the Flagellata appear to develop 

 relatively early in cultures from any depth of soil, EngJena viridis 

 and E. oxyuris being exceptions and appearing relatively late. 



Among the Infusoria, the organisms appearing early in 

 cultures were Lacrymaria olor, Cyclidium glaucoma, Vorticella 

 campanula and Colpidium striatum. On the other hand, Para- 

 moecium aurelia, P. putrinum and Uroleptus piscis made their 

 first appearance very late. 



