396 Notes 



that they were spread out and allowed to become slightly air-dried 

 so that they could be more easily sieved. 



Large bottles capable of holding 200 ozs. were then filled with the 

 soil which had been passed through a sieve having \ inch meshes. The 

 degree of dryness of the soils varies considerably, some having about 

 3 per cent, or 5 per cent., others having from 10 to 15 per cent, of water 

 by weight; the samples for any particular year however appear to be 

 of about the same degree of dryness. In most cases the soil was taken 

 from different depths at intervals of nine inches, sampling proceeding 

 in some cases into the deep layers of the sub-soil. 



Experiments. 



It was my privilege whilst working at the Rothamsted laboratory 

 to examine culturally soil from a few of these bottles for the presence 

 of protozoa and only samples from the top nine inches of a plot were 

 tested. In some preliminary experiments in 1912 it was found that 

 Broadbalk soil bottled in 1846 revealed no protozoa in culture, but 

 that Barnfield soil bottled in 1870 yielded amoebae and flagellates, 

 and Agdell soil bottled in 1874 yielded amoebae and flagellates, and 

 the ciliates Colpoda steinii and Colpoda cucidlus, in hay-infusion cultures. 



These results were very interesting as showing that the protozoa 

 had retained their vitality probably in the encysted condition for 

 a period of 42 years in the case of the Barnfield soil and 38 years in 

 the Agdell soil. 



As there were other bottles containing soil put up between 1846 

 and 1870, I decided to make cultures of some of these with a view 

 to finding out the oldest soil from which protozoa could be obtained 

 and the different species of protozoa which had survived. 



Dr Russell, director of the laboratory, very kindly granted me 

 permission to take small quantities of the soil from those bottles which 

 I desired to test and I take this opportunity of thanking him for 

 allowing me to make use of these valuable soils. 



The following soils were tested for the presence of protozoa ; Broad- 

 balk 1856, Broadbalk 1865, Geescroft 1865, Agdell 1867, Hoosfield 

 1868, and Barnfield 1870. From all the cultures except those of 

 Broadbalk 1856 protozoa were obtained. The cultures were made 

 in small glass dishes under the usual bacteriological precautions of 

 sterile media and vessels, etc., so that there can be no doubt that 

 the organisms encountered really came from the soil and not from 

 air-borne dust particles by chance infection. 



