272 Tramactions. — 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, 6|- inches long, 3^ broad, and 3f 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 then* 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 32 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 30 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. 



Claparede 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. 



