54 HABITS OF WORMS. Chap. I. 



carried down to the posterior parts of tlie 

 intestine, where these concretions would be 

 rolled about amongst the acid contents. The 

 concretions found in the intestines and in the 

 castings often have a worn appearance, but 

 whether this is due to some amount of 

 attrition or of chemical corrosion could not 

 be told. Claparede believes that they are 

 formed for the sake of acting as mill-stones, 

 and of thus aiding in the trituration of the 

 food. They may give some aid in this way ; 

 but I fully agree with Perrier that this must 

 be of quite subordinate importance, seeing 

 that the object is already attained by stones 

 being generally present in the gizzards and 

 intestines of worms. 



