50 HABITS OF WORMS. Chap. I. 



Here it is evident that the supply of cal- 

 careous matter must be superabundant. 

 Nevertheless with several worms collected on 

 such a site, the calciferous glands contained 

 as many free calciferous cells, and fully as 

 many and large concretions, as did the 

 glands of worms which lived where there was 

 little or no lime ; and this indicates that the 

 lime is an excretion, and not a secretion 

 poured into the alimentary canal for some 

 special purpose. 



On the other hand, the following considera- 

 tions render it highly probable that the 

 carbonate of lime, which is excreted by the 

 glands, aids the digestive process under 

 ordinary circumstances. Leaves during their 

 decay generate an abundance of various kinds 

 of acids, which have been grouped together 

 under the term of humus acids. We shall 

 have to recur to this subject in our fifth 

 chapter, and I need here only say that these 

 acids act strongly on carbonate of lime. The 

 half-decayed leaves which are swallowed in 

 such large quantities by worms would, there- 

 fore, after they have been moistened and 

 triturated in the alimentary canal, be apt to 



