272 Transactions, — Zoology. 
doubt contributed to undermine it; upon their deserting the stone, the 
work was again resumed by worms. When measured in August, 1882, the 
most protuberant point was down 1 inch ; in October, 1883, the point was 
exactly 2 inches below the level of the surface. One end of the ground 
beneath the stone is considerably excavated ; when these burrows collapse, 
the stone will again sink. In September, 1882, a small stone with a flat 
base, rounded at the edges, 64 inches long, 34 broad, and 33 in thickness, 
was laid on the turf; on the 15th of last October it had sunk 1 inch, and 
became sufficiently embedded to require some force to raise it ; the same 
day four fresh stones were placed on the ground, and layers of broken brick 
and wood-ashes were spread for future observations. 
Darwin states that some writers doubt if worms ever swallow earth 
solely for the purpose of excavating their burrows. Worms effect an entrance 
into loose soil by inserting the attenuated anterior extremity of their body 
into any crevice or hole, or forcing aside the particles by alternately with- 
drawing and driving in the stretched-out body, the pharynx is then pushed 
forward, and the swollen extremity presses the earth aside ; not only would 
it be impossible—although possessing considerable muscular power—for 
worms to penetrate into our hard sub-soils by these means, but on three 
occasions when large worms (L. uliginosus) were placed in a pot of very com- 
pact earth, they only effected an entrance after about 40, 29, and 82 hours’ 
work, ejecting a considerable amount of castings ; again, three small worms 
were placed in a pot of firm moist siliceous sand, they were only able—in 
about 80 hours—to bury themselves by swallowing and ejecting the sand ; 
pure sand castings were thrown out for some time afterwards; as the sand 
had been well washed there could have been no nutriment in it.* Mr. 
Darwin has shown in a similar experiment, with fine ferruginous sand, that 
under the circumstances worms are compelled to swallow a large amount of 
matter unfit for food. i 
Claparéde doubts whether worms swallow any quantity of earth merely 
for the sake of obtaining nutriment from it; my own observations lead me 
to agree with Darwin, who has clearly shown that it is not improbable. 
Mr. Darwin remarks (** V.M.” p. 14) that after heavy rain, succeeding 
dry weather, an astonishing number of dead worms may sometimes be seen 
lying on the ground ; he further says :—'* I believe that they were already 
sick, and that their deaths were merely hastened by the ground being 
flooded.” As I did not clearly understand whether he meant that when 
worms, under those circumstances, came to the surface and wandered about 
during the day, they were necessarily sick, I thought it right to experi- 
mentally test whether it was the case, although I had no doubt, as far as 
our worms were concerned, that a large proportion were healthy. 
* These worms have been fed, and are forming a layer of humus on the surface, 
