CHAP. V. AND DENUDATION. 251 



and very many of these beads and fragments 

 were picked up and swallowed by the worms, 

 for they were found in their castings, intes- 

 tines, and gizzards. They even swallowed 

 the coarse red dust, formed by the pounding 

 of the tiles. Nor can it be supposed that 

 they mistook the beads and fragments for 

 food ; for we have seen that their taste is 

 delicate enough to distinguish between dif- 

 ferent kinds of leaves. It is therefore 

 manifest that they swallow hard objects, 

 such as bits of stone, beads of glass and 

 angular fragments of bricks or tiles for 

 some special purpose ; and it can hardly be 

 doubted that this is to aid their gizzards 

 in crushing and grinding the earth, which 

 they so largely consume. That such hard 

 objects are not necessary for crushing 

 leaves, may be inferred from the fact 

 that certain species, which live in mud 

 or water and feed on dead or living 

 vegetable matter, but which do not swallow 

 earth, are not provided with gizzards,* and 

 therefore cannot have the power of utilising 

 stones. 



* Perrier, 'Archives de Zoolog. exper.' torn. iii. 1874, p. 419. 



