111 HISTORY. 



EARTH-WORMS are found throughout the world. 

 Though few in genera, and not many in species, yet 

 they make up in individual numbers, for it has been esti- 

 mated that they average about one hundred thousand to the 

 acre. Our American species have never been monographed, 

 which renders it impossible to judge of their probable num- 

 ber. Their castings may be seen on commons, so as to 

 cover almost entirely their surface, where the soil is poor 

 and the grass short and thin, and they are almost as numer- 

 ous in some of our parks where the grass grows well and 

 the soil appears rich. Even on the same piece of ground 

 worms are much more frequent in some places than in others, 

 although no visible difference in the nature of the soil is 

 manifest. They abound in paved court-yards contiguous to 

 houses, and on the sidewalks in country towns, and instances 

 have been reported where they have burrowed through the 

 floors of very damp cellars. 



Beneath large trees few castings can be found during cer- 

 tain parts of the year, and this is apparently due to the 

 moisture having been sucked out of the ground by the in- 

 numerable roots of the trees, an explanation which seems to 

 be confirmed by the fact that such places may be observed 

 covered with castings after the heavy autumnal rains. 

 Although most coppices and woods support large numbers 

 of worms, yet in forests of certain kinds of tree-growths, 

 where the ground beneath is destitute of vegetation, not a 

 casting is seen over wide reaches of ground, even during the 

 autumn. In mountainous districts worms are mostly rare, it 



