SOIL PROTOZOA IX SOUTH AFRICA. 341 



In order really to comprehend what organisms are present in 

 soils and their inter-relationships, soils must be examined in tht-ir 

 natm-al condition, without the addition of artificial culture media. 

 As mentioned in our previous communication, it is possible that 

 the biological activities of both Protozoa and bacteria are altex'ed 

 in artificial media, and hence the method of water culture has 

 been continued by us, this approximating most nearly to the con- 

 dition obtaining in nature. Eecord also is needed of all the- 

 Protozoa present in any one soil, and the protozoal fauna must be 

 considered as a complete whole. Organisms that develop relatively 

 slowly may, in the end, prove to be more important than those 

 that develop more quickly, and numbers are not always a mark of 

 importance. 



Material axd Methods. 



In connection with material, soils have been collected as 

 before, care being taken to make each sample of soil representa- 

 tive of the area concerned. Particulars of each sample are given 

 under the accounts, of the Protozoa found in the water cultures of 

 each soil. 



The method (jf water culture has been employed for the 

 I'eason already given, and cultures have usually been made in 

 the proportion of 5 grams of soil to 10 c.c. of boiled tap water. 

 The usual bacteriological precautions have been taken to avoid 

 contamination. 



For the purpose of counting the actual numbers of organisms, 

 the method used was as follows: — Measured quantities of culture 

 fluid, including portions from the various levels or depths of the 

 culture have been examined in the graduated chamber of a hsemo- 

 cytometer. The slow moving organisms, such as thecamoebae, 

 amoebae and Euglcna oxijuris, are then easily counted in life. For 

 rapidly moving organisms, such as some Flagellates and Ciliates 

 (when moving too quickly to be counted alive), a measured 

 volume of culture fluid has been mixed with an equal quantity 

 of hot .Schaudinn fliud or Carnoy fixative, and the organisms are 

 thus killed and fixed. A little methyl green has sometimes been 

 added and found useful. The number of organisms has then 

 been counted either in the hoemocytometer or in a series of cover- 

 slip wet preparations. Naturally, thecamoebse and amoebae can be 

 estimated by this method, though it has often been found easier 

 to count them in the living condition. 



Eesults of Examinations of Various Ordinary. 

 (Xon-WaterlogctEd) Soils. 



The soils herein discussed may be grouped according to the 

 geographical area whence they were obtained. 



Cape Province Soils. 



An intensive study of soil from three areas of the Eosebank 

 Experimental Station, near Cape Town, was made, and Eastern 

 Province soils were represented by samples from the Grootfon- 



