Earth- Worms in History. 5 7 



indispensable for the unarmed mouths of worms that they 

 should first be moistened and softened, their disintegration 

 being thereby the more readily effected. Fresh leaves, how- 

 ever soft and tender they may be, are similarly treated, prob- 

 ably from habit. Thus the leaves are partially digested before 

 they are taken into the alimentary canal, an instance of 

 extra-stomachal digestion, whose nearest analogy is to be 

 found in such plants as Dionaea and Drosera, for in them 

 animal matter is digested and converted into peptone, not 

 within a stomach, but on the surfaces of the leaves. 



But no portion of the economy of worms has been 

 more the subject of speculation than the calciferous glands. 

 About as many theories have been advanced on their utility 

 as there have been observers. Judging from their size and 

 from their rich supply of blood-vessels, they must be of vast 

 importance to these animals. They consist of three pairs, 

 which in the Common Earth-worm debouch into the ali- 

 mentary canal in front of the gizzard, but posteriorly to it, in 

 some genera. The two posterior pairs are formed by lamellae, 

 diverticula from the oesophagus, which are coated with a 

 pulpy cellular layer, with the outer cells lying free in infinite 

 numbers. If one of these glands is punctured and squeezed, 

 a quantity of white, pulpy matter exudes, consisting of these 

 free cells, which are minute bodies, varying in diameter from 

 two to six millimetres. They contain in their centres a small 

 quantity of excessively fine granular matter, that looks so 

 like oil globules that many scientists are deceived by its 

 appearance. When treated with acetic acid they quickly 

 dissolve with effervescence. An addition of oxalate of ammo- 

 nia to the solution throws down a white precipitate, showing 

 that the cells contain carbonate of lime. The two anterior 

 glands differ a little in shape from the four posterior ones by 

 being more oval, and also conspicuously in generally con- 

 taining several small, or two or three larger, or a single very 

 large concretion of carbonate of lime, as much as one and 

 one-half millimetres in diameter. With respect to the function 



