NATURAL HISTORY. 



itly broughl to the surface, and thus slowly but surely new layers 

 1(ll |,,l on top, while the older ones sink, thus increasing the thickness 

 the soil or loam. Did space permit we could make many an extract. 

 from Mr. Darwin's work which would show this and many other facts, but 

 a few will have to suffice to show how slowly yet how constantly the earth- 

 ms, unnoticed by man. are doing an enormous work: — 

 "Near Maer Bill, in Staffordshire, quicklime had been spread about 

 the year L827, thickly, over a field of good pasture land, which had not. 

 since been ploughed. " Some square holes were dug in this field in the be- 

 ginning of October, 1837. and the sections showed a layer of turf formed 

 by the malted 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 sur- 

 ; layer of lime in powder or in small lumps could be distinctly seen 

 running all round the vertical sides of the holes." This layer above the 

 line was almost entirely brought there by the earthworms. 



Every one is familiar with the fact that old stones in a meadow gradu- 

 ally sink beneath the surface. The writer remembers an old mill-stone 

 which had sunk so that its face was level with the surrounding ground, 

 and yel it had lain there for less than fifty years. This sinking was 

 caused by the fact that the earthworms had burrowed beneath it, allowing 

 it to subside gradually? while around it their deposits had gone on, thus 

 elevating the surrounding surface. Again Mr. Darwin writes: — 



•• When we behold a wide, turf-covered expanse, we should remember 

 that it- smoothness, on which so much of its beauty depends, is mainly 

 due t<> all the inequalities having been slowly levelled by worms. It is a 

 marvellous reflection that the whole of the superficial mould over any rich 

 expanse has passed, and will again pass, every few years, through the 

 bodies of worms. The plough is one of the most ancient and most valua- 

 ble of man's inventions, but long before he existed the land was in fact 

 ularly ploughed, and still continues to be ploughed, by earthworms." 

 Allied to the earthworm are many other forms, occurring in the earth, 

 in fresh water, and in the sea. Along the whole New England coast, under 

 below ami above low-water mark, one of these (Clitellio by name) 

 in large numbers; it is very slender, about two or three inches long,, 

 -oid red in color, but these marine forms yield in interest to some of those 

 '.nin- in Eresh water. One of these is Tubifex, the tube-builder, which 

 Ion- tubes in the ooze at the bottom of ponds as well as. 

 Nais is another small fresh-water genus, remarkable 

 ity to divide itself into two individuals. Our cut shows a speci- 

 nen, greatly enlarged, with this division going on. At the left end of the 

 worm which is crawling over a bit of fresh-water alga) is seen the head,. 



