286 



THE EARTHWORM AND OTHER ANNULATA 



soil with a plow. Objects like stones or a layer of gravel grad- 

 ually sink below the surface, as soil is brought up from beneath 

 and deposited above them, until they rest near the lower level of 

 the worms' activities. Darwin showed by observations upon the 

 fields near his home that this sinking occurred where layers of 



;ii»H««a«««*««l' 



■ mi ■ V ■■ ■ ■WMaiUi BOii i 



Fiu. 138. — Burial of objects by earthworms. 



Above, section through a fallen stone of the Druids' "temple" at Stonehenge, England, 

 showing how much it had sunk into the ground (scale J inch to 1 foot). 



Below, section of part of a Roman ruin at Silchester, England, showing a stone floor 

 upon which was a mass of charred wood, represented in black, and rubbish twenty-seven 

 inches thick, all covered by nine inches of fine soil. 



(From Darwin, " \'egetable Mould and Earthworms," copyright, 1892, by D. Appleton 

 and Co., reprinted by permission.) 



foreign material had been spread upon the ground. Pie explained 

 the settlement of great stones and even the burial of pavements 

 and debris of Roman buildings (Fig. 138), that have been exca- 

 vated in England as due to the worms bringing up soil year 

 after year as they burrowed between and below the stones, until a 

 structure that was originally at the surface came to rest at a lower 

 level. In the localities observed by Darwin, it was found that 



