20 



the bacterid ; Dr. B. Muriel Bristol the alf^ae ; Dr. W. B. Brierley 

 and Miss S. T. Jewson the tuiii^i, Mr. H. M. Morris the inse(Ms, 

 while till recently Dr. T. Goodey studied the nematodes and Mrs. 

 Matthews the more general relationships. The ultimate aim of the 

 agriculturist is to (H)ntrol this soil population in just the same wav 

 as the animal breeder has controlled and developed the (original 

 wild animals. But control is not possible without full i<nowledo;e 

 of what the organisms are, \\ hat they do and how they live. It is 

 this knowledge which the scientific workers are endeavouring m 

 gain. 



The first thing is to ascertain the numbers of each kind (A 

 organism present in the soil under different natural conditions. 

 That is being done for bacteria and protozoa, and some striking 

 relationships are observed. A new technique has been devised for 

 counting protozoa and a new medium' for use in bacterial estima- 

 tions. As the organisms multiply much more rapidly than 

 larger animals it is necessary to make the determina- 

 tions frequently and regularly: counts of bacteria and 19 

 species of protozoa — 4 ciliates, 6 amoebae and 9 flagellates — are 

 now made daily at Rothamsted, and it is intended to continue 

 these for 365 consecutive days and then to look for corre- 

 lations with temperature, soil moisture, rainfall, etc. Two interest- 

 ing features are clearly brought out ; the numbers of bacteria vary 

 inversely with the numbers of active amoebae, and one of the 

 llagellates (Oiconionas tcniio Martin) shows a remarkable two 

 davs' pcriodicitv, its numbers being high one day and low tlie next 

 witliout anv apparent external reason (p. 39). 



Further, an examination of the drain gauge results lias indi- 

 cated the existence of soil organisms capable of absorbing nitrates, 

 and thus competing with plants (p. 35). Algae have been found 

 which can do this, and Dr. Bristol is investigating their mode of 

 life and their function in the soil. Bacteria can also take up 

 nitrates. Large numbers of fungi have been found in the soil, and 

 are being studied by Dr. Brierley and Miss Jewson. 



The insect and other invertebrate fauna has been studied by 

 Mr. H. M. Morris, who hr.s taken samples each jilternate week 

 from the unmanured and the dunged plots on Broadbalk field. 

 Each sample contained 729 cubic inches of soil : the whole was 

 thoroughly sifted and the animals identified and (^ounted. Tlie 

 averaire results were : — 



Total Numi'.ers Pkr Acre. 



Farmyard Manure. 



7.727.000 



532.000 



1,010,000 



1,781,000 



Ants . . (2.946.000) 

 Collenibola (2,301.000) 



f Chirononiid 



"( Larvrr (515.000) 



