66 Life and Immortahty. 
Two ways are adopted by worms in excavating their bur- 
rows. Either the earth is pushed away on all sides or it is 
swallowed by the animal. In the former case the worm 
inserts the stretched-out and attenuated anterior extremity 
of its body into any little crevice or hole, and the pharynx 
is pushed forward into this part, which consequently swells 
and pushes away the earth on all sides, the anterior extremity 
thus actingasawedge. When placed in loose mould a worm 
will bury itself in between two and three minutes, but in 
earth that is moderately pressed down it often requires as 
many as fifteen minutes for its disappearance. But whenever 
a worm burrows toa depth of several feet in undisturbed 
compact ground, it must form its passage by swallowing the 
earth, for it is impossible that the ground could yield on all 
sides to the pressure of the pharynx when pushed forward 
within the worm’s body. Great depths are reached only 
during continued dry weather and severe cold, the burrows 
sometimes attaining to a depth of from seven to eight feet. 
The burrows run down perpendicularly, or, more commonly, | 
obliquely, and are sometimes said to branch. Generally, or 
invariably as I think, they are lined with fine, dark-colored 
earth voided by the worm, so that at first they must be made 
a little wider than their ultimate diameter. Little globular 
pellets of voided earth, still soft and viscid, often dot the 
walls of fresh burrows, and these are spread out on all sides 
by the worm as it travels up or down its burrow, the lining 
thus formed becoming very compact and smooth when 
nearly dry and closely fitting the worm’s body.  Ex- 
cellent points of support are thus afforded for the minute 
reflexed bristles which project in rows on all sides from the 
body, thus rendering the burrow well adapted for the rapid 
movement of the animal. The lining appears also to 
strengthen the walls, and perhaps saves the worm’s body 
from being scratched, which would assuredly be the case 
when the burrows, as is occasionally observed, pass through 
a layer of sifted coal cinders. The burrows are thus seen to 
