ii THE WEB OF LIFE 23 



(Siphonogaster) somewhat different from the common 

 Lumbricus are exceedingly numerous. From two separate 

 square feet of land chosen at random, Mr. Alvan Millson 

 collected the worm-casts of a season and found that they 

 weighed when dry 10 Ib. At this rate about 62,233 

 tons of subsoil would be brought in a year to the surface 

 of each square mile, and it is also calculated that every 

 particle of earth to the depth of tw r o feet is brought to 

 the surface once in 27 years. We do not wonder that 

 the district is fertile and healthy. 



mi 



Devouring the earth as they make their holes, which 

 are often 4 or even 6 feet deep ; bruising the particles 

 in their gizzards, and thus liberating the minute elements 

 of the soil ; burying leaves and devouring them at 

 leisure ; preparing the way by their burrowing for plant 

 roots and rain-drops, and gradually covering the surface 

 with their castings, worms have, in the history of the 

 habitable earth, been most important factors in progress. 

 Ploughers before the plough, they have made the earth 

 fruitful. It is fair, however, to acknowledge that vege- 

 table mould sometimes forms independently of earth- 

 worms, that some other animals which burrow or which 

 devour dead plants must also help in the process, and 

 that the constant rain of atmospheric dust, as Richthofen 

 has especially noted, must not be overlooked. 



In 1777, Gilbert White wrote thus of the earthworms- 



" The most insignificant insects and reptiles are of much more 

 consequence and have much more influence in the economy of 

 nature than the incurious are aware of. ... Earthworms, though 

 in appearance a small and despicable link in the chain of Nature 

 yet, if lost, would make a lamentable chasm. . . . Worms seem to 

 be the great promoters of vegetation, which would proceed but 

 lamely without them, by boring, perforating, and loosening the 

 soil, and rendering it pervious to rains and the fibres of plants ; by 

 drawing straws and stalks of leaves and twigs into it ; and, most 

 of all, by throwing up such infinite numbers of lumps of earth called 

 worm-casts, which, being their excrement, is a fine manure for 

 grain and grass. Worms probably provide new soil for hills and 

 slopes where the rain washes the earth away ; and they affect 

 slopes probably to avoid being flooded. . . . The earth without 

 worms would soon become cold, hard-bound, and void of fermenta- 

 tion, and consequently sterile. . . . These hints we think proper 



