297 



Further Observations on Protozoa in Relation to Soil Bacteria. 



By T. Goodey, D.Sc, Protozoologist, Research Laboratory in Agricultural 

 Zoology, University of Birmingham. 



(Communicated by Prof. F. W. Gamble, F.R.S. Received March 16, 1916.) 



CONTENTS. 



PAGE 



Introduction 297 



Methods 298 



Eesults — 1. Inoculation of Partially Sterilised Soil with 5 per cent. 



Untreated Soil 302 



2. Confirmatory Experiment 304 



3. Mass Inoculations of Protozoa 307 



4. Mass Inoculations of Bacteria-free Amoeba Cysts 309 



Discussion 310 



Summary 313 



Conclusions 314 



Introduction. 



The work recorded in the present paper is a continuation and an extension 

 of my earlier work on the inoculation of protozoa into soil, an account of 

 which has already been published in these Proceedings.* I pointed out in 

 that paper (p. 455) that the introduction of large numbers of bacteria into the 

 soil along with the added protozoa must be a source of disturbance to the 

 bacterial flora, and by reason of this the experiments could not be considered 

 as showing a clear issue between the added protozoa and the soil bacteria. 

 The investigations dealt with in the present paper represent an attempt to 

 eliminate this source of experimental error, my aim being primarily to 

 inoculate a partially sterilised soil with protozoa freed from bacteria. 



The work was begun some months before Russell's paperf replying to my 

 previous communication appeared, so that the experiments described here 

 are open to much of the criticism levelled at the earlier work. However, as 

 I have obtained certain very interesting results which are worthy of record, 

 and as I may not be able to continue the investigation much longer, it seems 

 desirable to publish an account of the work, and give the results obtained. 

 My best thanks are due to Prof. F. W. Gamble for his helpful criticisms and 

 suggestions throughout the course of the work, and especially during the 

 preparation of this paper. 



* ' Roy. Soc. Proc.,' B, vol. 88, p. 437 (1915). 

 t 'Roy. Soc. Proc.,' B, vol. 89, p. 76 (1915). 



