WORMS. 221 



ai-e occasionally active during the daytime. They are exceedingly dependent on 

 moisture, for a single day in the dry air kills them, while on the other hand they will 

 survive in water for a long period ; hence, whenever there comes a " di-y spell," they 

 all retreat into the lower stratum of soil not yet j)arched by the heat upon the sur- 

 face. I have known them to retire to a depth of four feet in a period of prolonged 

 drought, which completely exhausted the moisture to that depth. In winter, too, they 

 always go down below the frost and make a little hollow or chamber at the bottom of 

 their burrow, in which they coil up to hibernate, often several of them getting to- 

 gether. They usually carry down with them a few small stones, for what purpose is 

 not known. In summer they live close to the surface, if it is not too dry, shutting up 

 the mouths of their tubes with little pellets gathered from about, or with their own 

 castings. Keeping quiet during the day, they emerge at night, stretching forth the 

 anterior end of their bodies and exploring the neighborhood ; keeping, however, most 

 of their long selves within dooi's and retreating entirely upon the least alarm ; a jar of 

 the soil, or light falling upon them, is sufficient to awaken their timidity and cause an 

 instantaneous retraction of the protruded part of their bodies. But their habit of 

 remaining so near the surface renders their timidity, even, an insufficient jjrotection, 

 for they are often discovered and dragged forth by robins and other birds, which, 

 imlike Luther, esteem the diet of worms. The Lumbrici are omnivorous ; beefsteak, 

 cabbage, fruit, green leaves and dead, dirt, stones, broken glass are all swallowed with 

 an impartiality that would do credit to Aristides. But, although it has its preferences 

 as to what it will eat, Lumbricus is not content without dirt and small stones, or other 

 hard, indigestible objects, together with more nutritious fare. Apparently from the 

 dirt it is able to extract some matter, perhaps to assimilate the microscopic organisms 

 it contains ; the stones probably act as grinders, serving to crush the food projoer and 

 mix it thoroughly with the digestive juices. The earth-worm, then, passes through its 

 intestine pretty much everything in and on the ground, which can possibly get 

 through ; but it discharges its castings upon the surface, a manure which is universally 

 known as vegetable mould, but would be more correctly termed if called animal 

 mould. Now, as the worms burrow in every direction, they constantly bring up from 

 below and deposit on the surface, so that the superficial layer grows slowly but 

 steadily. Thus it happens that if ashes are strewn on a field the earth-worm castings 

 are deposited over them, graduallj^ burying them until they finally disappear. In his 

 book on the earth-worm, Mr. Darwin gives many instances of this apparent subsidence 

 which, under the most fa^'orable circumstances, goes on at the rate of two or three 

 tenths of an inch per annum. "We quote the following account from his pages: 

 " Near Maer Hill in Staffordshire, quick-lime had been spread about the year 1827, 

 thickly, over a field of good pasture land, which had not since been ploughed. Some 

 square holes were dug in this field in the beginning of October 1837, and the; sections 

 showed a layer of turf, formed by the matted roots of the grasses, one half inch in 

 thickness, beneath which, at a depth of two and a half inches (or three inches from 

 the surface), a layer of lime in powder or in small lumps could be distinctly seen run- 

 ning all round the vertical sides of the holes." Even large objects, big stones and ex- 

 tensive pavements, are gradually buried by the worms, because their burrows extend 

 underneath, and by their collapse let the overlying object sink, while their castings 

 raise the surface around it. " When we behold," writes Mr. Darwin, " a wide, turf- 

 ■covered expanse, we should remember that its smoothness, on which so much of its 

 beauty depends, is mainly due to all the inequalities having been slowly levelled by 



