368 SOIL PROTOZOA IN SOUTH AFRICA. 



HoJoplinja ovinii, one of the ciliates more rarely observed, 

 exhibited this pecuharity. Thus, in the culture of the Liesbeek 

 soil taken at six inches deep, H. ovum appeared on the twelfth 

 day. It disappeared the next day and was not seen again luitil 

 the 95th day of culture. 



Prorodon nvu»i appeared once in the culture of Liesbeek soil 

 of one inch depth on the 47th day of culture and has not been 

 seen since. 



EntoHijihoii nulcdtitni appeared in a culture of soil from the 

 Observatory Garden, Lourenco Marques, on tlie seventh day of 

 culture. It was present in very small numbers, had entirely 

 disappeared next day, and has not reappeared since. 



Colcps hirtus, again, was erratic. In cultures of soil from 

 Lourengo Marques, it appeared in very small numbers on days 

 7, 8, 22, 37, 38, 39, 45, 50, 51, 62 and 63, and was absent during 

 the intervening periods. 



Another case of interest is where an organism appears early 

 in cultures and is practically the dominant or subdominant for a 

 short time. It then disappears and only reappears again sporadic- 

 ally and often only in units. Cyclidium glaucoma fairly often 

 has behaved in this manner in our cultures. 



Two suggestions may be made to explain this sporadic 

 appearance of certain trophic Protozoa in soil cultures. Possibly 

 but few encysted organisms are present in the soil. Those that 

 excyst early either seem unable to persist and multiply and the 

 reappearances are due to later excy station of contemporaneous 

 cysts, or multiplication of trophic forms may be immediately 

 followed by encystment, when the newly-formed cysts provide 

 the succeeding sporadic trophic Protozoa. The existence of 

 small strains of various Protozoa in soil cultures has been often 

 noticed by us, and may have arisen in the way indicated, or they 

 may represent definite small strains or varieties. 



It is obvious that detailed daily examinations are necessary 

 if the true protozoal fauna of any soil is to be accurately 

 ascertained. 



Seasonal Variation in the Protozoal Fauna of Certain Soils. 



A few observ;itions have been made in connection with the 

 possible influence of the season of the year on the protozoal fauna 

 of certain soils, though, unfortunately, the depths at which the 

 soil samples were taken for us were not always the same. 



Thus, samples of Virgin Eed KaiToo soil and Cultivated Pied 

 Karroo soil, at a depth of six inches, collected on September 29 at 

 the Grootfontein School of Agriculture, Middelburg, were reported 

 on, as to protozoal content, in this Journal, Vol. XVIII. 

 pp. 379-380. The previous findings may be compared M-ith those 

 now recorded, as the second samples were taken on April 11, 

 1922, at approximately the same spots where the previous samples 

 were obtained, but at nine inches deep. Six months' interval 

 occurred between the collecting of the two samples, and 

 the results may be presented in tabular form (Tables VI and VII). 



