Earth-Worms tn History. 57 
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 Dionwa 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 lamelle, 
diverticula from the cesophagus, 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 
