Chap. I. CALCIFEROUS GLANDS. 43 



kind is found in the intestines of worms. As 

 the leaves which are dragged into the bur- 

 rows are often dry and shrivelled, it is in- 

 dispensable for their disintegration by the 

 unarmed mouths of worms that they should 

 first be moistened and softened ; and fresh 

 leaves, however soft and tender they may be, 

 are similarly treated, probably from habit. 

 The result is that they are partially digested 

 before they are taken into the alimentary 

 canal. I am not aware of any other case of 

 extra-stomachal digestion having been re- 

 corded. The boa-constrictor bathes its prey 

 with saliva^ but this is solely for lubricating 

 it. Perhaps the nearest analogy may be 

 found in such plants as Drosera and Dionsea ; 

 for here animal matter is digested and con- 

 verted into peptone not within a stomach, but 

 on the surfaces of the leaves. 



Calciferous Glands,— These glands (see 

 Fig. 1), judging from their size and from their 

 rich supply of blood-vessels, must be of much 

 importance to the animal. But almost as 

 many theories have been advanced on their 

 use as there have been observers. They 

 consist of three pairs, which in the common 



