INFLUENCE OF EARTHWORMS ON SOIL REACTION, 425 
But, even if the effect be but a retardation and not a complete check to 
the edaphic succession, the importance of earthworm action in relation to 
vegetation may obviously be considerable. 
To summarize, then, the main conclusions :— 
(a) Wormeasts, as compared with the soil from which they are derived, are 
usually less acid (or less alkaline), the reduction amounting in some 
cases to as much as 75 per cent. 
(b) Wormeasts commonly contain a higher proportion of carbonates than 
the surface soil. 
(c) The organic content of wormeasts is very high, indicating that the 
effects produced operate on that layer of the soil which is normally 
most acid. 
(d) The frequency of earthworms in natural soils appears to be greatest in 
those which are approximately neutral in reaction, and to diminish as 
the acidity or alkalinity increases. Other favourable factors are high 
water content and a high organic content. 
(e) Earthworms may thus have a marked effect on vegetation and retard 
the “edaphic succession.” 
The conclusions (a) to (c) are unaffected by the fact that the different 
species of earthworms were not distinguished. It is not improbable that the 
frequency in relation to the factors under (d) may vary with the species, and 
that their effects (e) may be of varying magnitude, though the data obtained 
would seein to indicate that such a difference, if it exists, is one of degree 
rather than of kind. 
