Chap. II. PROTECTION OF THEIR BURROWS. 61 



" holes had 8 or 9 small stones over 

 " them ; after four nights one had about 

 " 30, and another 34 stones."* One stone 

 which had been dragged over the gravel-walk 

 to the mouth of a burrow weighed two 

 ounces ; and this proves how strong worms 

 are. But they show greater strength in some- 

 times displacing stones in a well-trodden 

 gravel-walk ; that they do so, may be inferred 

 from the cavities left by the displaced stones 

 being exactly filled by those lying over the 

 mouths of adjoining burrows, as I have my- 

 self observed. 



Work of this kind is usually performed 

 during the night ; but I have occasionally 

 known objects to be drawn into the burrows 

 during the day. What advantage the worms 

 derive from plugging up the mouths of their 

 burrows with leaves, &c, or from piling 

 stones over them, is doubtful. They do not 

 act in this manner at the times when they 

 eject much earth from their burrows ; for their 

 castings then serve to cover the mouth. 

 When gardeners wish to kill worms on a 



* An account of her observations is given in the ' Gardeners 

 Chronicle,' March 28th, 1868, p. 324. 



