i88i.] 
Analyses of Books. 673 
soil, there is no doubt. From this point of view it is to be 
remarked that the contents of the intestines of worms and the 
castings themselves are always acid. A considerable quantity of 
dead leaves, &c., are also drawn into the burrows to the depth of 
3 to 4 inches, and thus the organic matter in the soil is increased. 
As regards the acid secreted by worms, or otherwise produced in 
their systems, we would suggest that it is not improbably the 
oxalic, a solvent well adapted for effecting the chemical disinte- 
gration of many kinds of rocks. Numbers of minute stones are 
also swallowed, and by the mechanical aCtion of the gizzard and 
their friction against each other they are in part pulverised. 
It will easily be seen that any agency which raises small quan- 
tities of earth from beneath to the surface, and deposits them 
there, must aid in the process known to geologists as denudation. 
If the surface has a slope, the fine soil thus deposited will gra- 
dually be washed down by rains, and must then find its way 
to the nearest water-course, and ultimately to the sea. In dry 
weather the castings must be dispersed by the wind, and carried 
to leeward. Hence the difficulty of believing that “ any appre- 
ciable quantity of earth can be removed from a gently inclined 
surface, covered with vegetation and matted with roots,” is re- 
moved. It may even be suggested that worms play a part in 
causing large boulders and fragments of rock to travel down 
gentle declivities. They like the shelter of stones, and by gra- 
dually excavating and removing the soil from beneath the margins 
of the block they may cause it gradually to slide downwards. 
It is also by the aCtion of worms that ancient pavements, coins, 
weapons, &c., left upon the surface of the earth, gradually dis- 
appear from view. Mr. Darwin mentions that a footway leading 
across his lawn, and constructed of flagstones set edgewise, had 
become covered with an inch of mould between the years 1843 
and 1877. 
The interesting account of the habits of the earth-worm can 
be but very briefly noticed. From careful observations and expe- 
riments it appears that worms do not possess eyes, but can 
nevertheless distinguish light from darkness. If brightly illu- 
minated they withdraw, not by a reflex aCtion, but voluntarily. 
They have no power of hearing, but are very sensitive to vibra- 
tions and to changes of temperature. They appear to possess 
the senses of smell and taste, though very imperfectly developed. 
Though omnivorous, and even given to cannibalism, they prefer 
some kinds of food to others. From the experiments] of Mr. 
Darwin, on the manner in which they drag into their burrows 
leaves of different shapes, they may even be considered as not 
entirely without intelligence. 
We must here close our survey of this work, with which natu- 
ralists will do well to make themselves acquainted, both for the 
fads which it makes known and as a model how researches of 
this nature ought to be conducted. 
