Further observations on protozoa in relation to soil bacteria

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 paper 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.