154 ANIMAL ACTIVITIES. 
the use of plants. He renders the earth porous for the 
better spread of moisture and the more rapid pushing 
of plant-roots. He buries rocks far beneath the soil 
and covers old fields with fresh loam. All pupils 
should read Mr. Darwin’s book entitled ‘‘ The Forma- 
tion of Vegetable Mould.’’ 
The Earthworm’s Relatives. Along with the 
earthworm are classified many animals which outwardly 
bear no resemblance to him. It sometimes seems as if 
naturalists reserved the sub-kingdom Vermes as a sort 
of waste-box in which to place all creatures not easily 
classified elsewhere. The strange ways of the Vermes 
must be studied by the help of other books. 
