II. 



THE PART PLAYED BY WORMS IN THE 

 HISTORY OF THIS PLANET. 



The Forma- "Woems have played a more important part 



tionofVege- j n ^ e history of the world than most persons 



table Mold ,,,'„'? T ■> « 1 • j 



through the would at first suppose. In almost all humid 



Action of countries they are extraordinarily numerous, 



Earthworms, . , . • ■ t 



page 305. and for their size possess great muscular 

 power. In many parts of England a weight of more than 

 ten tons (10,516 kilogrammes) of dry earth annually 

 passes through their bodies and is brought to the surface 

 on each acre of land ; so that the whole superficial bed 

 of vegetable mold passes through their bodies in the 

 course of every few years. From the collapsing of the 

 old burrows the mold is in constant though slow move- 

 ment, and the particles composing it are thus rubbed to- 

 gether. By these means fresh surfaces are continually 

 exposed to the action of the carbonic acid in the soil, 

 and of the humus-acids which appear to be still more 

 efficient in the decomposition of rocks. The generation 

 of the humus-acids is probably hastened during the diges- 

 tion of the many half-decayed leaves which worms con- 

 sume. Thus the particles of earth, forming the super- 

 ficial mold, are subjected to conditions eminently favor- 

 able for their decomposition and disintegration. More- 



