BY R. GREIG-SMITH. 841 



parts of water. The addition of O'l % of dextrose greatly helped 

 the growth of the protozoa, but, noting that "Killer had found 

 Giltay's solution to be one of the best for the purpose, it was 

 tested and found to be eminently suitable. The* weakening of 

 the Giltay's solution did not accelerate the growth of the pro- 

 tozoa, neither did the replacement of the potassium nitrate by 

 similar weights of either asparagin, peptone, ammonium sulphate 

 or chloride, urea, or of meat-extract. Finally, 1 % hay-infusion 

 with O'l % of nitrate was shown to be best for the growth of 

 ciliates, and Giltay's solution for the growth of amoebae. 



With the idea of obtaining a maximum growth of protozoa, a 

 poor alluvial soil* from the Hawkesbury Agricultural College 

 was air-dried, sifted, moistened, and spread out in a large photo- 

 graphic developing dish. It was maintained in the moist con- 

 dition for three weeks. Portions of the soil, containing: 10 7 of 



' o /o 



moisture, were treated with varying amounts of toluene. The 

 remainder was air-dried, and also treated with toluene. 



Moist soil ... 

 Air-dried soil 



Ciliates survived 1 -5 %, killed by 2 %. 



Amoebae survived 2 %, 



Ciliates and amoebae survived 20 %. 



The sandy soil of the Society's garden contained 12 % of 

 moisture. It was treated with toluene at once, and then air- 

 dried. 



Moist soil ... 

 Air-dried soil 



Ciliates survived 1 %, killed by 2 %. 

 Amoebee survived 2 %, killed by 5 %. 

 Ciliates and amoebae survived 20 %. 



Control-experiments confirmed these findings. 



During the experiments, which were comparatively numerous, 

 it was noted that the ciliates were less in number, and that the 

 flora was more varied in the untreated, than in the toluened 



* The protozoa, noted in cultures from this soil, were Colpoda cucullus, 

 Vortictlla, Paramcecium, Peridium tripos, Trachelocerca viride, Gercomo- 

 nas, Chatomonas, Dileptus, Trepomonas agilis, Amaba lobosa, Amaba 

 dijffluenn. 



15 



