given off from the soil, but has failed to find any considerable 

 evolution, and it soon became clear that the reaction, if it takes 

 place at all, goes on too slowly to be studied in a limited time in the 

 laboratory. 



The way round a difficulty of this sort is to seek out and study 

 carefully an exaggerated case as nearly as possible parallel to the 

 one in hand, and we had an obvious instance in a manure heap, 

 where marked losses of nitrogen take place from its compounds. 

 A manure heap, however, is an extraordinarily complex problem to 

 attack and required far more time than we could give it. Fortunately, 

 the Hon. Rupert Guinness came forward and enabled us to secure the 

 services of Mr. E. H. Richards, formerly of the Sewage Commission, 

 who now devotes himself entirely to this question. We are now, there- 

 fore, steadily developing our attack : while Messrs. Horton and 

 Appleyard are studying the chemical processes in the soil, Mr. 

 Richards is investigating the much more intense processes in the 

 manure heap. Apart from the valuable light this last investigation 

 may be expected to throw on the soil work, it is of great intrinsic 

 importance by reason of its general bearing on the nitrogen losses 

 from the farm. 



The agents bringing about the production of nitrate, the loss of 

 nitrogen, and apparently other reactions in the soil, are bacteria, 

 and these are being studied in the James Mason Laboratory by Dr. 

 Hutchinson and Mr. MacLennan. Hitherto they have been dealt 

 with in groups only, but it has now become necessary to make 

 a closer study of the various types, and about a hundred have 

 accordingly been isolated and grown in pure culture. 



The stock of soil bacteria appears to be remarkably varied ; Mr. 

 Buddin finds some which can develope in presence of strong 

 organic poisons, such as phenol, cresol, hydroquinone, etc., and, 

 indeed, apparently feed on these substances. 



The conditions under which soil bacteria work have for some 

 years been under investigation here, and in last year's Report 

 reference was made to experiments showing that the bacteria are 

 not the only active organisms in the soil, but that other and larger 

 organisms are present which are inimical to them and keep their 

 numbers down. Provisionally these organisms were identified with 

 soil protozoa, and a survey of the soil fauna was begun to ascertain 

 if protozoa were present in our soil, and, if so, whether they acted 

 detrimentally to bacteria. Various forms were isolated from hay 

 infusions inoculated with soil, but there was nothing to show 

 whether they occurred in the soil in active forms or as cysts. 

 Fortunately, Mr. Martin devised a method by which some of the 

 protozoa can be extracted from the soil in the form in which they 

 actually exist, and he and Mr. Lewin have shown that numbers of 

 amoebae and of flagellates are in the active form and some at least 

 feed on bacteria in the soil. The amoebae are at present under 

 investigation, and prove to be new forms of considerable interest. 



When soil is treated with mild antiseptics, gentle heat, or in 

 other ways inimical to life, it is found that the soil bacteria, after 

 a preliminary depression finally multiply more rapidly than before, 

 and the harmful factor is put out of action. Dr. Hutchinson and 

 Mr. MacLennan have shown that quicklime behaves like other 

 antiseptics and causes first a depression and then a great increase 



