Fig. 5.—Composite concretion of calccwm-carbonate, produced by the 
action of reducing bacteria upon caleium-sulphate, growing upon 
scalariform vegetable cells. : 
[x about 38 diam. | 
Fig. 6.—Concretion of calcium-carbonate, produced by the, action of 
bacteria upon caleium-sulphate, growing im the bacterial jelly. 
[x about 38 diam. ] ' 
