440 Mr. T. Goodey. Investigations on Protozoa in 



in order to allow the bulk of the water to evaporate off, and a heating lamp 

 was put into the house in order to accelerate slightly the evaporation. 



The reason for thus driving off the bulk of the water from the soil was 

 that I desired to bring about in the soil all the conditions possible for aiding 

 the excystation of the added encysted protozoa, for I had found in experi- 

 menting with cysts that if they were slightly air-dried and then moistened, 

 excystation was more rapid than where no slight drying had been allowed. 



The water-contents of the inoculated soils, when bottled again at the end 

 of these few days of air-drying, were as follows : — Untreated, 6"2 per cent. ; 

 Untreated + Bacteria,* 2*7 per cent. ; U. + Col. cucullus, 7'4 per cent. ; U. + 

 Col. steinii, 7*22 per cent. ; U. + Col. maupasii, 6*9 per cent. ; U. + Vort. 

 microstoma, 6 -8 per cent. ; U. + Amoibce, 7*5 per cent. ; U. + Flagellates, 

 7"5 per cent. : U. + 1870, 6-5 per cent. 



Sterile distilled water Was next added to all the soils, in sufficient quantity 

 to bring up the water-content of each to 18 per cent. 



In the case of the seven bottles of Hoosfield soil, the samples were 

 inoculated with protozoa from the sand-hay-infusion cultures in exactly the 

 same way as described above. These lots were spread out on sheets of sterile 

 brown paper and left in the drying room for five hours at a temperature of 

 about 20° or 22° C. in order to drive off the bulk of the added water and 

 bring about conditions favourable to the excystation of protozoa after 

 re-moistening. The water-content of the various soils after drying was as 

 follows : — Untreated (U.), 7"4 per cent. ; Toluened and heated (T.), 5"9 per 

 cent. ; T. + Untreated (T + U.), 5-8 per cent. ; T. + Ciliates (T. + C), 

 3-1 per cent. ; T. + Amceba (T. -f Am.), 2'7 per cent. ; T. + Flagellates 

 (T. + Fl.), 3 per cent. ; T. + Bacteria (T + B.), 1-6 per cent. Sterile 

 distilled water was then added, as in the case of the 1846 set, in order to 

 bring up the water-content of each lot to 18 per cent, by weight. 



Both sets of bottles were then left in a small warmed glass-house, the 

 temperature of which varied between 45° and 55° F. Later on they were 

 taken from the glass-house and kept in the laboratory in a room at about 

 12-15° C. At various intervals during the course of the work the water- 

 content of each soil has been determined in order to estimate the loss of 

 water by gradual evaporation, and at these times the loss from each has been 

 made good by the addition of sufficient sterile distilled water to bring up the 

 water-content to 18 or 20 per cent, by weight. 



In attempting to estimate the numbers of protozoa present in the soils the 

 following methods have been employed : — 



* This lot was treated in the same manner as the inoculated Hoosfield soil described 

 further on. 



