Protozoa in Relation to Soil Bacteria. 



303 



"higher point than that of the (T+W) soil. This is followed by a 

 marked drop at 43 days, whilst the (T + W) curve shows a continued 

 rise up to this time, though later on it shows a drop at 78 days. From 

 this point onwards until the 154th day the (T + 5 per cent. U) curve keeps 

 -at a lower level than the (T + W) curve. Both curves rise to a fairly 

 high level at the 223rd day, following a re-moistening of the soils, whilst at 

 the 293rd day the (T + 5 per cent. U) curve has dropped to a comparatively 

 low level again, at which time the bacterial count for the (T + W) soil 

 was unfortunately lost owing to the liquefaction of the gelatine plates. A 

 later count, however, at 323 days showed that the numbers had kept high. 

 The sharp rise at 21 clays, and the subsequent marked drop at 43 days in the 

 •(T + 5 per cent. U) curve are characteristic features of curves of treated plus 

 small quantities of untreated soil, as Eussell and Hutchinson have shown in 

 many experiments. These two investigators have also attributed the fall 

 in the numbers of bacteria to the depressing effect of the activity of the 

 protozoa added in the untreated soil. 



* It will be convenient at this point to deal with the protozoal counts for the 

 soils under consideration, and in the accompanying Table the approximate 

 numbers of protozoa per gramme of soil are set out. 





Untreated. 



Nos. 

 per gramme. 



T + W. 

 Jfos. per gramme. 



T + 5 per cent. TJ. 

 Isos. per gramme. 



At start. 



At start. 



After 

 320 days. 



At start. 



After 

 43 days. 



After 

 210 days. 



Ciliates — 

















50 







2 or 3 



100 





Gonostomum affine 



? a few 







? a few 



50 





Ehizopods — 

















10,000 



100 



200 



600 



30,000 



30,000 



Amoeba terricola 



? a few 







? a few 



200 



1,000 



Gephyramoeba delicatula 



? a few 







? a few 



200 



1,000 



Flagellates, sps. ? 



10,000 



1000 





1500 



10,000 



? 



The following protozoa occurred so irregularly in the untreated soil cultures that it was 

 Impossible to form an approximate estimate of their numbers ; only a few of each species, 

 however, appeared to be present per gramme of soil : — Colpoda cucullus, Col. maupasii, Gono- 

 stomum affine, Chilodon sp. ?, Balantiophorus sp. ?, Amceba terricola, Leptomyxa flabellata* 

 Gephyramoeba delicatula* and Chlamydophrys sp. ?. 



In the (T + 5 per cent. U) soil the numbers at 43 days are very striking, 

 especially those for Amosba Umax, and show that within six weeks from the 



* Goodey, T., "A Preliminary Communication on three new Proteomyxan Ehizopods 

 from Soil," ' Arch. f. Protistenkunde,' vol. 35, p. 89 (1914). 



