Chap. V. AND DENUDATION. 249 



therefore cannot have the power of utilising 

 stones. 



During the grinding process, the particles 

 of earth must be rubbed against one another, 

 and between the stones and the tough 

 lining membrane of the gizzard. The softer 

 particles will thus suffer some attrition, and 

 will perhaps even be crushed. This con- 

 clusion is supported by the appearance of 

 freshly ejected castings, for these often re- 

 minded me of the appearance of paint which 

 has just been ground by a workman between 

 two flat stones. Morren remarks that the 

 intestinal canal is " impleta tenuissima terra, 

 veluti in pulverem redacta." * Perrier also 

 speaks of " l'etat de pate excessivement fine a 

 laquelle est re'duite la terre qu'ils rejettent," 

 &c.f 



As the amount of trituration which the 

 particles of earth undergo in the gizzards 

 of worms possesses some interest (as we 

 shall hereafter see), I endeavoured to obtain 

 evidence on this head by carefully examining 

 many of the fragments which had passed 



* Morren, { De Lumbrici terrestris,' &c, p. 16. 



f Archives de Zooiog. ExpeY.' torn. iii. 1874, p. 418. 



