and　Dr。　King；　who　looked　carefully；　never　saw　even　a　fragment　of　a
  leaf　thus　drawn　in。　　Nor　could　any　trace　be　discovered　of　the　worms
  having　crawled　down　the　exterior　surfaces　of　the　towers　in　search
  of　leaves；　and　had　they　done　so；　tracks　would　almost　certainly　have
  been　left　on　the　upper　part　whilst　it　remained　soft。　　It　does　not；
  however；　follow　that　these　worms　do　not　draw　leaves　into　their
  burrows　during　some　other　season　of　the　year；　at　which　time　they
  would　not　build　up　their　towers。
  From　the　several　foregoing　cases；　it　can　hardly　be　doubted　that
  worms　swallow　earth；　not　only　for　the　sake　of　making　their　burrows；
  but　for　obtaining　food。　　Hensen；　however；　concludes　from　his
  analyses　of　mould　that　worms　probably　could　not　live　on　ordinary
  vegetable　mould；　though　he　admits　that　they　might　be　nourished　to
  some　extent　by　leaf…mould。　｛39｝　　But　we　have　seen　that　worms
  eagerly　devour　raw　meat；　fat；　and　dead　worms；　and　ordinary　mould
  can　hardly　fail　to　contain　many　ova；　larvae；　and　small　living　or
  dead　creatures；　spores　of　cryptogamic　plants；　and　micrococci；　such
  as　those　which　give　rise　to　saltpetre。　　These　various　organisms；
  together　with　some　cellulose　from　any　leaves　and　roots　not　utterly
  decayed；　might　well　account　for　such　large　quantities　of　mould
  being　swallowed　by　worms。　　It　may　be　worth　while　here　to　recall　the
  fact　that　certain　species　of　Utricularia；　which　grow　in　damp　places
  in　the　tropics；　possess　bladders　beautifully　constructed　for
  catching　minute　subterranean　animals；　and　these　traps　would　not
  have　been　developed　unless　many　small　animals　inhabited　such　soil。
  The　depth　to　which　worms　penetrate；　and　the　construction　of　their
  burrows。Although　worms　usually　live　near　the　surface；　yet　they
  burrow　to　a　considerable　depth　during　long…continued　dry　weather
  and　severe　cold。　　In　Scandinavia；　according　to　Eisen；　and　in
  Scotland；　according　to　Mr。　Lindsay　Carnagie；　the　burrows　run　down
  to　a　depth　of　from　7　to　8　feet；　in　North　Germany；　according　to
  Hoffmeister；　from　6　to　8　feet；　but　Hensen　says；　from　3　to　6　feet。
  This　latter　observer　has　seen　worms　frozen　at　a　depth　of　1。5　feet
  beneath　the　surface。　　I　have　not　myself　had　many　opportunities　for
  observation；　but　I　have　often　met　with　worms　at　depths　of　3　to　4
  feet。　　In　a　bed　of　fine　sand　overlying　the　chalk；　which　had　never
  been　disturbed；　a　worm　was　cut　into　two　at　55　inches；　and　another
  was　found　here　at　Down　in　December　at　the　bottom　of　its　burrow；　at
  61　inches　beneath　the　surface。　　Lastly；　in　earth　near　an　old　Roman
  Villa；　which　had　not　been　disturbed　for　many　centuries；　a　worm　was
  met　with　at　a　depth　of　66　inches；　and　this　was　in　the　middle　of
  August。
  The　burrows　run　down　perpendicularly；　or　more　commonly　a　little
  obliquely。　　They　are　said　sometimes　to　branch；　but　as　far　as　I　have
  seen　this　does　not　occur；　except　in　recently　dug　ground　and　near
  the　surface。　　They　are　generally；　or　as　I　believe　invariably；　lined
  with　a　thin　layer　of　fine；　dark…coloured　earth　voided　by　the　worms；
  so　that　they　must　at　first　be　made　a　little　wider　than　their
  ultimate　diameter。　　I　have　seen　several　burrows　in　undisturbed　sand
  thus　lined　at　a　depth　of　4　ft。　6　in。；　and　others　close　to　the
  surface　thus　lined　in　recently　dug　ground。　　The　walls　of　fresh
  burrows　are　often　dotted　with　little　globular　pellets　of　voided
  earth；　still　soft　and　viscid；　and　these；　as　it　appears；　are　spread
  out　on　all　sides　by　the　worm　as　it　travels　up　or　down　its　burrow。
  The　lining　thus　formed　becomes　very　compact　and　smooth　when　nearly
  dry；　and　closely　fits　the　worm's　body。　　The　minute　reflexed
  bristles　which　project　in　rows　on　all　sides　from　the　body；　thus
  have　excellent　points　of　support；　and　the　burrow　is　rendered　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。　　I　think　so　because　several　burrows　which
  passed　through　a　layer　of　sifted　coal…cinders；　spread　over　turf　to
  a　thickness　of　1。5　inch；　had　been　thus　lined　to　an　unusual
  thickness。　　In　this　case　the　worms；　judging　from　the　castings；　had
  pushed　the　cinders　away　on　all　sides　and　had　not　swallowed　any　of
  them。　　In　another　place；　burrows　similarly　lined；　passed　through　a
  layer　of　coarse　coal…cinders；　3。5　inches　in　thickness。　　We　thus　see
  that　the　burrows　are　not　mere　excavations；　but　may　rather　be
  compared　with　tunnels　lined　with　cement。
  The　mouths　of　the　burrow　are　in　addition　often　lined　with　leaves；
  and　this　is　an　instinct　distinct　from　that　of　plugging　them　up；　and
  does　not　appear　to　have　been　hitherto　noticed。　　Many　leaves　of　the
  Scotch…fir　or　pine　（Pinus　sylvestris）　were　given　to　worms　kept　in
  confinement　in　two　pots；　and　when　after　several　weeks　the　earth　was
  carefully　broken　up；　the　upper　parts　of　three　oblique　burrows　were
  found　surrounded　for　lengths　of　7；　4；　and　3。5　inches　with　pine…
  leaves；　together　with　fragments　of　other　leaves　which　had　been
  given　the　worms　as　food。　　Glass　beads　and　bits　of　tile；　which　had
  been　strewed　on　the　surface　of　the　soil；　were　stuck　into　the
  interstices　between　the　pine…leaves；　and　these　interstices　were
  likewise　plastered　with　the　viscid　castings　voided　by　the　worms。
  The　structures　thus　formed　cohered　so　well；　that　I　succeeded　in
  removing　one　with　only　a　little　earth　adhering　to　it。　　It　consisted
  of　a　slightly　curved　cylindrical　case；　the　interior　of　which　could
  be　seen　through　holes　in　the　sides　and　at　either　end。　　The　pine…
  leaves　had　all　been　drawn　in　by　their　bases；　and　the　sharp　points
  of　the　needles　had　been　pressed　into　the　lining　of　voided　earth。
  Had　this　not　been　effectually　done；　the　sharp　points　would　have
  prevented　the　retreat　of　the　worms　into　their　burrows；　and　these
  structures　would　have　resembled　traps　armed　with　converging　points
  of　wire；　rendering　the　ingress　of　an　animal　easy　and　its　egress
  difficult　or　impossible。　　The　skill　shown　by　these　worms　is
  noteworthy　and　is　the　more　remarkable；　as　the　Scotch　pine　is　not　a
  native　of　this　district。
  After　having　examined　these　burrows　made　by　worms　in　confinement；　I
  looked　at　those　in　a　flower…bed　near　some　Scotch　pines。　　These　had
  all　been　plugged　up　in　the　ordinary　manner　with　the　leaves　of　this
  tree；　drawn　in　for　a　length　of　from　1　to　1。5　inch；　but　the　mouths
  of　many　of　them　were　likewise　lined　with　them；　mingled　with
  fragments　of　other　kinds　of　leaves；　drawn　in　to　a　depth　of　4　or　5
  inches。　　Worms　often　remain；　as　formerly　stated；　for　a　long　time
  close　to　the　mouths　of　their　burrows；　apparently　for　warmth；　and
  the　basket…like　structures　formed　of　leaves　would　keep　their　bodies
  from　coming　into　close　contact　with　the　cold　damp　earth。　　That　they
  habitually　rested　on　the　pine…leaves；　was　rendered　probable　by
  their　clean　and　almost　polished　surfaces。
  The　burrows　which　run　far　down　into　the　ground；　generally；　or　at
  least　often；　terminate　in　a　little　enlargement　or　chamber。　　Here；
  according　to　Hoffmeister；　one　or　several　worms　pass　the　winter
  rolled　up　into　a　ball。　　Mr。　Lindsay　Carnagie　informed　me　（1838）
  that　he　had　examined　many　burrows　over　a　stone…quarry　in　Scotland；
  where　the　overlying　boulder…clay　and　mould　had　recently　been
  cleared　away；　and　a　little　vertical　cliff　thus　left。　　In　several
  cases　the　same　burrow　was　a　little　enlarged　at　two　or　three　points
  one　beneath　the　other；　and　all　the　burrows　terminated　in　a　rather
  large　chamber；　at　a　depth　of　7　or　8　feet　from　the　surface。　　These
  chambers　contained　many　small　sharp　bits　of　stone　and　husks　of
  flax…seeds。　　They　must　also　have　contained　living　seeds；　for　on　the
  following　spring　Mr。　Carnagie　saw　grass…plants　sprouting　out　of
  some　of　the　intersected　chambers。　　I　found　at　Abinger　in　Surrey　two
  burrows　terminating　in　similar　chambers　at　a　depth　of　36　and　41
  inches；　and　these　were　lined　or　paved　with　little　pebbles；　about　as
  large　as　mustard　seeds；　and　in　one　of　the　chambers　there　was　a
  decayed　oat…grain；　with　its　husk。　　Hensen　likewise　states　that　the
  bottoms　of　the　burrows　are　lined　with　little　stones；　and　where
  these　could　not　be　procured；　seeds；　apparently　of　the　pear；　had
  been　used；　as　many　as　fifteen　having　been　carried　down　into　a
  single　burrow；　one　of　which　had　germinated。　｛40｝　　We　thus　see　how
  easily　a　botanist　might　be　deceived　who　wished　to　learn　how　long
  deeply　buried　seeds　remained　alive；　if　he　were　to　collect　earth
  from　a　considerable　depth；　on　the　supposition　that　it　could　contain
  only　seeds　which　had　long　lain　buried。　　It　is　probable　that　the
  little　stones；　as　well　as　the　seeds；　are　carried　down　from　the
  surface　by　being　swallowed；　for　a　surprising　number　of　glass　beads；
  bits　of　tile　and　of　glass　were　certainly　thus　carried　down　by　worms
  kept　in　pots；　but　some　may　have　been　carried　down　within　their
  mouths。　　The　sole　conjecture　which　I　can　form　why　worms　line　their
  winter…quarters　with　little　stones　and　seeds；　is　to　prevent　their
  closely　coiled…up　bodies　from　coming　into　close　contact　with　the
  surrounding　cold　soil；　and　such　contact　would　perhaps　interfere
  with　their　respiration　which　is　effected　by　the　skin　alone。
  A　worm