Fresh News on Earthworms. 
87 
1883.] 
to have been aware of Darwin’s earlier memoirs on the sub- 
ject, but not of the observations of H. Thiel. He observed 
that the channels by which the roots of plants penetrate 
into the subsoil are chiefly made by the large earthworm 
( Lumbricus terrestris ), which at the same time lines them 
with finely divided mould. 
Hensen finds that the large earthworm operates in the 
subsoil, whilst the smaller species (L. communis and others) 
work in the upper layer of the soil. All of them in the 
night thrust 'their bodies partially up out of their holes, and 
drag in decaying leaves for food. This author illustrates his 
work with two plates, showing the course of the worm-holes, 
the manner in which they are lined, and the roots by which 
they are traversed. The holes or tubes he finds most dis- 
tinctly marked in sandy soils, where they descend vertically 
to a depth of 3, 4, and even 6 feet, and then extend further 
in a horizontal direction. The sides of these tubes are 
studded more or less closely with little black prominences, 
often of a line in diameter, which are the excrement of the 
worm, as appears on microscopical and chemical comparison 
with the excreta taken from the body of -the worms. 
In tubes which have existed for some time there are gene- 
rally found roots of the plants which are growing on the 
surface. Such roots, of to J line in thickness, run even 
to the very end of the tubes, giving off all the way minuter 
rootlets covered with capillaries which spread over the sides. 
This phenomenon, says Prof. Hensen, may be best observed 
with plants of the cabbage tribe. It will be readily admitted 
that such roots are placed under very favourable circum- 
stances for growth and nutrition. The matter taken from 
the sides of the tubes, and that from the intestines of the 
worms, differs little in its composition from leaf-mould. 
From his analysis Hensen concludes that worms certainly 
eat soil, but only in order to make their tubes. Their real 
nutriment consists of half-decayed vegetable, and inciden- 
tally animal matter. Ordinary garden mould would scarcely 
afford them a sufficient quantity of assimilable matter, though 
leaf-mould might do so when not too far decayeed. 
As regards the fertility of a soil the earthworm exerts a 
favourable a< 5 tion from several points of view : — 
1. It insures an equable distribution of leaves and other 
loose portions of organic matter, and removes them 
from the action of the wind. 
2. It promotes the decomposition of such organic matter 
by comminution. 
