Chap. I. CALCIFEROUS GLANDS. 55 



" tion."* Therefore it seems highly probable 

 that the innumerable calciferous cells, which 

 are poured from the four posterior glands 

 into the alimentary canal of worms, serve to 

 neutralise more or less completely the acids 

 there generated by the half-decayed leaves. 

 We have seen that these cells are instantly 

 dissolved by a small quantity of acetic acid, 

 and as they do not always suffice to neu- 

 tralise the contents of even the upper part of 

 the alimentary canal, the lime is perhaps 

 aggregated into concretions in the anterior 

 pair of glands, in order that some may be 

 carried down to the posterior parts of the 

 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. Olaparede 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 ; 



* M. Foster, ut sup. p. 200. 



