forwards　into　this　part；　which　consequently　swells　and　pushes　away
  the　earth　on　all　sides。　　The　anterior　extremity　thus　serves　as　a
  wedge。　　It　also　serves；　as　we　have　before　seen；　for　prehension　and
  suction；　and　as　a　tactile　organ。　　A　worm　was　placed　on　loose　mould；
  and　it　buried　itself　in　between　two　and　three　minutes。　　On　another
  occasion　four　worms　disappeared　in　15　minutes　between　the　sides　of
  the　pot　and　the　earth；　which　had　been　moderately　pressed　down。　　On
  a　third　occasion　three　large　worms　and　a　small　one　were　placed　on
  loose　mould　well　mixed　with　fine　sand　and　firmly　pressed　down；　and
  they　all　disappeared；　except　the　tail　of　one；　in　35　minutes。　　On　a
  fourth　occasion　six　large　worms　were　placed　on　argillaceous　mud
  mixed　with　sand　firmly　pressed　down；　and　they　disappeared；　except
  the　extreme　tips　of　the　tails　of　two　of　them；　in　40　minutes。　　In
  none　of　these　cases；　did　the　worms　swallow；　as　far　as　could　be
  seen；　any　earth。　　They　generally　entered　the　ground　close　to　the
  sides　of　the　pot。
  A　pot　was　next　filled　with　very　fine　ferruginous　sand；　which　was
  pressed　down；　well　watered；　and　thus　rendered　extremely　compact。　　A
  large　worm　left　on　the　surface　did　not　succeed　in　penetrating　it
  for　some　hours；　and　did　not　bury　itself　completely　until　25　hrs。　40
  min。　had　elapsed。　　This　was　effected　by　the　sand　being　swallowed；
  as　was　evident　by　the　large　quantity　ejected　from　the　vent；　long
  before　the　whole　body　had　disappeared。　　Castings　of　a　similar
  nature　continued　to　be　ejected　from　the　burrow　during　the　whole　of
  the　following　day。
  As　doubts　have　been　expressed　by　some　writers　whether　worms　ever
  swallow　earth　solely　for　the　sake　of　making　their　burrows；　some
  additional　cases　may　be　given。　　A　mass　of　fine　reddish　sand；　23
  inches　in　thickness；　left　on　the　ground　for　nearly　two　years；　had
  been　penetrated　in　many　places　by　worms；　and　their　castings
  consisted　partly　of　the　reddish　sand　and　partly　of　black　earth
  brought　up　from　beneath　the　mass。　　This　sand　had　been　dug　up　from　a
  considerable　depth；　and　was　of　so　poor　a　nature　that　weeds　could
  not　grow　on　it。　　It　is　therefore　highly　improbable　that　it　should
  have　been　swallowed　by　the　worms　as　food。　　Again　in　a　field　near　my
  house　the　castings　frequently　consist　of　almost　pure　chalk；　which
  lies　at　only　a　little　depth　beneath　the　surface；　and　here　again　it
  is　very　improbable　that　the　chalk　should　have　been　swallowed　for
  the　sake　of　the　very　little　organic　matter　which　could　have
  percolated　into　it　from　the　poor　overlying　pasture。　　Lastly；　a
  casting　thrown　up　through　the　concrete　and　decayed　mortar　between
  the　tiles；　with　which　the　now　ruined　aisle　of　Beaulieu　Abbey　had
  formerly　been　paved；　was　washed；　so　that　the　coarser　matter　alone
  was　left。　　This　consisted　of　grains　of　quartz；　micaceous　slate；
  other　rocks；　and　bricks　or　tiles；　many　of　them　from　1/20　to　1/10
  inch　in　diameter。　　No　one　will　suppose　that　these　grains　were
  swallowed　as　food；　yet　they　formed　more　than　half　of　the　casting；
  for　they　weighed　19　grains；　the　whole　casting　having　weighed　33
  grains。　　Whenever　a　worm　burrows　to　a　depth　of　some　feet　in
  undisturbed　compact　ground；　it　must　form　its　passage　by　swallowing
  the　earth；　for　it　is　incredible　that　the　ground　could　yield　on　all
  sides　to　the　pressure　of　the　pharynx　when　pushed　forwards　within
  the　worm's　body。
  That　worms　swallow　a　larger　quantity　of　earth　for　the　sake　of
  extracting　any　nutritious　matter　which　it　may　contain　than　for
  making　their　burrows；　appears　to　me　certain。　　But　as　this　old
  belief　has　been　doubted　by　so　high　an　authority　as　Claparede；
  evidence　in　its　favour　must　be　given　in　some　detail。　　There　is　no　a
  priori　improbability　in　such　a　belief；　for　besides　other　annelids；
  especially　the　Arenicola　marina；　which　throws　up　such　a　profusion
  of　castings　on　our　tidal　sands；　and　which　it　is　believed　thus
  subsists；　there　are　animals　belonging　to　the　most　distinct　classes；
  which　do　not　burrow；　but　habitually　swallow　large　quantities　of
  sand；　namely；　the　molluscan　Onchidium　and　many　Echinoderms。　｛37｝
  If　earth　were　swallowed　only　when　worms　deepened　their　burrows　or
  made　new　ones；　castings　would　be　thrown　up　only　occasionally；　but
  in　many　places　fresh　castings　may　be　seen　every　morning；　and　the
  amount　of　earth　ejected　from　the　same　burrow　on　successive　days　is
  large。　　Yet　worms　do　not　burrow　to　a　great　depth；　except　when　the
  weather　is　very　dry　or　intensely　cold。　　On　my　lawn　the　black
  vegetable　mould　or　humus　is　only　about　5　inches　in　thickness；　and
  overlies　light…coloured　or　reddish　clayey　soil：　　now　when　castings
  are　thrown　up　in　the　greatest　profusion；　only　a　small　proportion
  are　light　coloured；　and　it　is　incredible　that　the　worms　should
  daily　make　fresh　burrows　in　every　direction　in　the　thin　superficial
  layer　of　dark…coloured　mould；　unless　they　obtained　nutriment　of
  some　kind　from　it。　　I　have　observed　a　strictly　analogous　case　in　a
  field　near　my　house　where　bright　red　clay　lay　close　beneath　the
  surface。　　Again　on　one　part　of　the　Downs　near　Winchester　the
  vegetable　mould　overlying　the　chalk　was　found　to　be　only　from　3　to
  4　inches　in　thickness；　and　the　many　castings　here　ejected　were　as
  black　as　ink　and　did　not　effervesce　with　acids；　so　that　the　worms
  must　have　confined　themselves　to　this　thin　superficial　layer　of
  mould；　of　which　large　quantities　were　daily　swallowed。　　In　another
  place　at　no　great　distance　the　castings　were　white；　and　why　the
  worms　should　have　burrowed　into　the　chalk　in　some　places　and　not　in
  others；　I　am　unable　to　conjecture。
  Two　great　piles　of　leaves　had　been　left　to　decay　in　my　grounds；　and
  months　after　their　removal；　the　bare　surface；　several　yards　in
  diameter；　was　so　thickly　covered　during　several　months　with
  castings　that　they　formed　an　almost　continuous　layer；　and　the　large
  number　of　worms　which　lived　here　must　have　subsisted　during　these
  months　on　nutritious　matter　contained　in　the　black　earth。
  The　lowest　layer　from　another　pile　of　decayed　leaves　mixed　with
  some　earth　was　examined　under　a　high　power；　and　the　number　of
  spores　of　various　shapes　and　sizes　which　it　contained　was
  astonishingly　great；　and　these　crushed　in　the　gizzards　of　worms　may
  largely　aid　in　supporting　them。　　Whenever　castings　are　thrown　up　in
  the　greatest　number；　few　or　no　leaves　are　drawn　into　the　burrows；
  for　instance　the　turf　along　a　hedgerow；　about　200　yards　in　length；
  was　daily　observed　in　the　autumn　during　several　weeks；　and　every
  morning　many　fresh　castings　were　seen；　but　not　a　single　leaf　was
  drawn　into　these　burrows。　　These　castings　from　their　blackness　and
  from　the　nature　of　the　subsoil　could　not　have　been　brought　up　from
  a　greater　depth　than　6　or　8　inches。　　On　what　could　these　worms　have
  subsisted　during　this　whole　time；　if　not　on　matter　contained　in　the
  black　earth？　　On　the　other　hand；　whenever　a　large　number　of　leaves
  are　drawn　into　the　burrows；　the　worms　seem　to　subsist　chiefly　on
  them；　for　few　earth…castings　are　then　ejected　on　the　surface。　　This
  difference　in　the　behaviour　of　worms　at　different　times；　perhaps
  explains　a　statement　by　Claparede；　namely；　that　triturated　leaves
  and　earth　are　always　found　in　distinct　parts　of　their　intestines。
  Worms　sometimes　abound　in　places　where　they　can　rarely　or　never
  obtain　dead　or　living　leaves；　for　instance；　beneath　the　pavement　in
  well…swept　courtyards；　into　which　leaves　are　only　occasionally
  blown。　　My　son　Horace　examined　a　house；　one　corner　of　which　had
  subsided；　and　he　found　here　in　the　cellar；　which　was　extremely
  damp；　many　small　worm…castings　thrown　up　between　the　stones　with
  which　the　cellar　was　paved；　and　in　this　case　it　is　improbable　that
  the　worms　could　ever　have　obtained　leaves。　　Mr。　A。　C。　Horner
  confirms　this　account；　as　he　has　seen　castings　in　the　cellars　of
  his　house；　which　is　an　old　one　at　Tonbridge。
  But　the　best　evidence；　known　to　me；　of　worms　subsisting　for　at
  least　considerable　periods　of　time　solely　on　the　organic　matter
  contained　in　earth；　is　afforded　by　some　facts　communicated　to　me　by
  Dr。　King。　　Near　Nice　large　castings　abound　in　extraordinary
  numbers；　so　that　5　or　6　were　often　found　within　the　space　of　a
  square　foot。　　They　consist　of　fine；　pale…coloured　earth；　containing
  calcareous　matter；　which　after　having　passed　through　the　bodies　of
  worms　and　being　dried；　coheres　with　considerable　force。　　I　have
  reason　to　believe　that　these　castings　had　been　formed　by　species　of
  Perichaeta；　which　have　been　naturalized　here　from　the　East。　｛38｝
  They　rise　like　towers；　with　their　summits　often　a　little　broader
  than　their　bases；　sometimes　to　a　height　of　above　3　and　often　to　a
  height　of　2。5　inches。　　The　tallest　of　those　which　were　measured　was
  3。3　inches　in　height　and　1　inch　in　diameter。　　A　small　cylindrical
  passage　runs　up　the　centre　of　each　tower；　through　which　the　worm
  ascends　to　eject　the　earth　which　it　has　swallowed；　and　thus　to　add
  to　its　height。　　A　structure　of　this　kind　would　not　allow　leaves
  being　easily　dragged　from　the　surrounding　ground　into　the　burrows；
  and　Dr。　King；　who　looked　carefully；　never　saw　even　a　fragment　of　a
  leaf　thus　drawn　in。　　N