PLATfi 4. 



Bacillus coU eomviunis. Surface gelatine plate culture, O'l c.c. ot xT>?ifm c.c. of Rugby sewage. 



Gas in Gelatine Shake Culture, 24 hours at 20° C. 

 From lefb to right the tubes represent jhri, Tfi'nnj TnoniD rnoWn c.c. of Nottingham crude sewage. 



[ To face page 50. 



