86 
Fresh News on Earthworms . 
[February, 
V. FRESH NEWS ON EARTHWORMS, 
cy. 
J IT is noteworthy how much we find is to be learnt con- 
I cerning even the most despised plant or animal when 
once some genuine observer points the way. Darwin’s 
researches on the earthworm had extended over forty years, 
yet the subject is not yet exhausted. There was room left 
for Mr. Kinahan to make valuable and interesting observa- 
tions, which are recorded in our last volume.* MM. Pasteur 
and Feltz have shown that these little creatures may be a 
source of danger by bringing to the surface virulent matter 
from the bodies of buried men and animals. M. Trouessart 
has observed that a common species ( Lumhricus agricola) 
constructs towers at the mouth of its burrow, just as is done, 
according to Darwin, by the nearly allied genus Pinchceta . 
And now we find that Prof. Victor Hensen, Herr von 
Lengerke, and the Danish zoologist P. E. Mullert have all 
been engaged with the stud)' of earthworms, and have elicited 
additional faCts in connection with their habits, their food, 
their part in the formation of “ vegetable mould,” as it is 
commonly called, and their influence on the fertility of the 
soil. This, as we shall see below, is probably even greater 
than was supposed. 
It was formerly considered that humus was derived entirely 
from the decomposition of vegetable matter. Darwin, as we 
know, showed that animal agency played here an essential 
part, and concluded that all such mould had been passed 
again and again through the intestinal canal of worms, and 
owed its characteristic properties to this aCtion. 
As far back as 1865 H. Thiel, without reference to the 
earlier researches of Darwin commencing in 1837, observed 
that the roots of red clover penetrate into the soil to the 
depth of 2 yards and more, by means of tubes or channels 
pre-existing in the sub-soil. These channels he thought 
might have been formed by the roots of trees which had 
formerly traversed the soil and had subsequently decayed ; 
or by some animal. What animal he does not appear to 
have ascertained. 
In 1 877 Prof. Hensen made a further advance. He seems 
* Journal of Science 7882, p. 331, 377. 
f See Landwithschaftliche Jahrbiicher, 1882, p. 661 ; Der Norddeutsche 
Landwith, 1881, p. 568; and Biedermann’s Central Blatt, 1882, p. 723. 
