WORMS. 221 



are occasionally active during the daytime. They are exceedingly dejiendent 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 "dry sjiell," they 

 all retreat into the lower stratum of soil not yet parched by the heat upon the sur- 

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

 drought, which com2:)letely exhausted the moisture to that depth. In winter, too, they 

 always go down below the frost and make a little hollow or chaml)er at the lidlloni 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 uj) 

 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 doors and retreating entirely upon the least alarm ; a jar of 

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

 instantaneous retraction of the protruded ])art of their bodies. But their habit of 

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

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

 unlike Luther, esteem the diet of worms. The Lumhrici are omnivorous; beefsteak, 

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

 an iirii)artiality that would do credit to Aristides. But, although it has its preferences 

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

 liard, indigestible objects, together with more nutritious fare. Ajjparently 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 ])roper and 

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

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

 through ; but it discharges its castings u])on the surface, a manure which is universally 

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

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

 below and dc]iosit on the surface, so that the superficial layer grows .slowly but 

 steadily. Thus it happens th.at if ashes are strewn on a tield the earth-worm castings 

 are deposited over tJiem, gradually burying them until they finally disappear. In his 

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

 which, under the most favorable 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, qui<3k-liuie had been spread about the year 1827, 

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

 S(|uare 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 lumjis 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 colla])se 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 

 I)eauty depends, is mainly due to all tin- inecpialitics having lieen slowly levellccl by 



