68 Life and Immortality. 
if spread out uniformly, would form in many places a layer 
of one-fifth of an inch in thickness. But this large amount 
is not deposited within the old unused burrows. If the 
burrows did not collapse, the whole ground would be first 
thickly riddled with holes to the depth of ten inches or 
more, which in fifty years would grow into a hollow, unsup- 
ported place ten inches deep. 
Hardly any animal is more universally distributed than 
worms. The earth-worm is found in all parts of the world, 
and some of the genera have an enormous range. They 
inhabit the most isolated islands, abounding in Iceland, and 
also being known to exist in the West Indies, St. Helena, 
Madagascar, New Caledonia and Tahiti. Worms from 
Kergulen Land in the Antarctic regions have been described 
by Ray Lankester, and Darwin has reported them as being 
found in the Falkland Islands. How they reach such 
isolated islands is quite unknown. They are easily killed 
by salt water, and it does not seem likely that young worms 
or their egg-capsules could be carried in earth adhering to 
the feet or beaks of land-birds, especially to Kergulen Land, 
for it is not now inhabited by any terrestrial bird. 
We have seen that worms are found in nearly every part 
of the globe, that they are very numerous, as many as 
348,480 having been found in an acre of rich ground in New 
Zealand, and that by the peculiar economy of their nature 
they are fitted to accomplish a great deal of good in the 
earth. They have played a more important part in the 
history of the world than most persons would at first sup- 
pose. In many parts of England, according to Darwin, a 
weight of more than ten tons of dry earth annually passes 
through their bodies and is brought to the surface in each 
acre of land, so that the entire superficial bed of vegetable 
mould passes through their bodies in the course of every 
few years; and in most parts of the forests and pasture-lands 
of Southern Brazil, where several species of earth-worms 
abound, the whole soil to a depth of a quarter of a metre 
