430 ZOOLOGY. 



other hand, recent observations demonstrate that worms may occur in 

 even much greater numbers than were fouud by Ileusen. An English 

 gentleman, e. g., found in Hertfordshire, "in his forest land, as many as 

 100 to the cubic yard, and in a rich strip bordering vines not less than 

 180 animals in an equal area; i. c, from 484,000 to 871,000 to an acre." 

 (Critic, N. Y., V. 2, p. 7G, 1881.) 



A little calculation will convince the most skeptical that worms with 

 the habits thus indicated and in the numbers known to occur must in 

 time produce great effects. Mr. Darwin has been observing their habits 

 and doings for many years. "Near Maer Hall, in Staffordshire, quick- 

 lime had been spread, about the year 1827, thickly over a field of good 

 pasture-land which had not since been plowed. Some square holes were 

 <lug 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, half 

 an inch in thickness, beneath which, at a depth of 2^ inches (or 3 inches 

 from the surface), a layer of the lime in powder or in small lumps could 

 be distinctly seen running all round the vertical sides of the hol^s." (P. 

 130.) Again, a quantity of broken chalk was spread on December 20, 

 1842, over part of a field near Darwin's house. "The chalk was laid 

 on the land for the sake of observing at some future period to what 

 depth it would become buried. At the end of November, 1871 — that is, 

 after an interval of 29 years — a trench was dug across this part of the 

 field, and a line of white nodules could be traced at a depth of 7 inches 

 from the surface. The mold, therefore (exclusive of the turf), had been 

 thrown uj) at an average rate of .22 inch i)er year." (P. 139.) In view 

 of such operations we can readily account for the burial of ancient 

 cities and towns, and a number of cases in jjoint are cited in a special 

 chapter on "the part which worms have played in the burial of ancient 

 buildings." The subsidence of pavements, the burial of Eoman villas 

 at Abiuger, Chedworth, Brading, and elsewhere, the entombment of 

 the Eoman towns of Silchester, Wroxeter, &c., are shown to be mainly 

 due to the action of worms. We can readily comprehend, therefore, 

 bow it is that the more ancient cities which once flourished in Asia and 

 the older seats of civilization have been covered to such a depth as to 

 have been entirely concealed, even without taking into consideration 

 the accumulation of dust and other dirt. 



Analyses of worm-casts have been communicated to the Eoyal Hor- 

 ticultural Society, by Dr. Gilbert, with reference to the amount of nitro- 

 gen involved. He found that the dried mold contained 35 per cent, 

 of nitrogen, which was considerably more than was present in the mold 

 of pasture land and two or three times more than in that of arable land. 

 It was less rich, however, than highly manured kitchen-garden mold. 

 On the whole the soil only gained from what the worms brought up 

 from below, as by trenching. 



