165 



A Contribution to our Knowledge of the Protozoa of the Soil. 

 By T. Goodey, M.Sc. ^Birm.), Mackinnon Student of the Boyal 

 Society, Bothamsted Experimental Station. 



{Communicated by A. D. Hall, F.K.S. Beceived May 19, — Bead June 1, 1911.) 

 [Plate 4.] 

 CONTENTS. 



PAGE 



Introduction 165 



Part I. — Protozoa Found. 



a. Methods 167 



b. Systematic , 168 



c. Active Protozoa Found on the Surface of the Soil 169 



Part II. — Experimental. 



d. Thermotaxis 170 



e. Galvanotaxis 171 



/. Excystation Experiments 177 



g. Summary and General Conclusions 178 



Literature and Explanation of Plate. 



Introduction. 



In the 'Journal of - Agricultural Science,' Vol. Ill, Bart 2, 1909, 

 Drs. Bussell and Hutchinson of this laboratory published an account of 

 their investigations on the effect of partial sterilisation of soil on the 

 production of plant food. In this paper it is shown that, when soils are 

 heated or treated with certain volatile antiseptics, and brought again under 

 conditions favourable to plant growth, they show a great increase in fertility. 

 It is further shown that, although the bacteria are at first reduced very 

 considerably in numbers, yet under conditions of temperature, moisture, and 

 aeration favouring growth, they subsequently increase enormously in 

 numbers. Pari passu with this increase in the number of bacteria, there 

 is an increase in the production of ammonia in the soil, and it is to this that 

 the soil owes its greater power of production. 



In explanation of these results, the theory is advanced that the treatment 

 by heating or with volatile antiseptics has removed some factor which in the 

 untreated soil normally limits the growth of bacteria, and thus the rate of 

 ammonia production. This limiting factor is looked upon as being biological 

 in character, but not of a bacterial nature. 



It was found in cultures of untreated soil in suitable nutrient media that 

 certain animal organisms belonging to the phylum protozoa became very 



