of　the　alimentary　canal　were　found　to　be　plainly　acid；　as　shown　by
  litmus　paper。　　This　acidity　cannot　be　attributed　to　the　nature　of
  the　digestive　fluid；　for　pancreatic　fluid　is　alkaline；　and　we　have
  seen　that　the　secretion　which　is　poured　out　of　the　mouths　of　worms
  for　the　sake　of　preparing　the　leaves　for　consumption；　is　likewise
  alkaline。　　The　acidity　can　hardly　be　due　to　uric　acid；　as　the
  contents　of　the　upper　part　of　the　intestine　were　often　acid。　　In
  one　case　the　contents　of　the　gizzard　were　slightly　acid；　those　of
  the　upper　intestines　being　more　plainly　acid。　　In　another　case　the
  contents　of　the　pharynx　were　not　acid；　those　of　the　gizzard
  doubtfully　so；　while　those　of　the　intestine　were　distinctly　acid　at
  a　distance　of　5　cm。　below　the　gizzard。　　Even　with　the　higher
  herbivorous　and　omnivorous　animals；　the　contents　of　the　large
  intestine　are　acid。　　〃This；　however；　is　not　caused　by　any　acid
  secretion　from　the　mucous　membrane；　the　reaction　of　the　intestinal
  walls　in　the　larger　as　in　the　small　intestine　is　alkaline。　　It　must
  therefore　arise　from　acid　fermentations　going　on　in　the　contents
  themselves　。　。　。　　In　Carnivora　the　contents　of　the　coecum　are　said
  to　be　alkaline；　and　naturally　the　amount　of　fermentation　will
  depend　largely　on　the　nature　of　the　food。〃　｛26｝
  With　worms　not　only　the　contents　of　the　intestines；　but　their
  ejected　matter　or　the　castings；　are　generally　acid。　　Thirty
  castings　from　different　places　were　tested；　and　with　three　or　four
  exceptions　were　found　to　be　acid；　and　the　exceptions　may　have　been
  due　to　such　castings　not　having　been　recently　ejected；　for　some
  which　were　at　first　acid；　were　on　the　following　morning；　after
  being　dried　and　again　moistened；　no　longer　acid；　and　this　probably
  resulted　from　the　humus　acids　being；　as　is　known　to　be　the　case；
  easily　decomposed。　　Five　fresh　castings　from　worms　which　lived　in
  mould　close　over　the　chalk；　were　of　a　whitish　colour　and　abounded
  with　calcareous　matter；　and　these　were　not　in　the　least　acid。　　This
  shows　how　effectually　carbonate　of　lime　neutralises　the　intestinal
  acids。　　When　worms　were　kept　in　pots　filled　with　fine　ferruginous
  sand；　it　was　manifest　that　the　oxide　of　iron；　with　which　the　grains
  of　silex　were　coated；　had　been　dissolved　and　removed　from　them　in
  the　castings。
  The　digestive　fluid　of　worms　resembles　in　its　action；　as　already
  stated；　the　pancreatic　secretion　of　the　higher　animals；　and　in
  these　latter；　〃pancreatic　digestion　is　essentially　alkaline；　the
  action　will　not　take　place　unless　some　alkali　be　present；　and　the
  activity　of　an　alkaline　juice　is　arrested　by　acidification；　and
  hindered　by　neutralization。〃　｛27｝　　Therefore　it　seems　highly
  probable　that　the　innumerable　calciferous　cells；　which　are　poured
  from　the　four　posterior　glands　into　the　alimentary　canal　of　worms；
  serve　to　neutralise　more　or　less　completely　the　acids　there
  generated　by　the　half…decayed　leaves。　　We　have　seen　that　these
  cells　are　instantly　dissolved　by　a　small　quantity　of　acetic　acid；
  and　as　they　do　not　always　suffice　to　neutralise　the　contents　of
  even　the　upper　part　of　the　alimentary　canal；　the　lime　is　perhaps
  aggregated　into　concretions　in　the　anterior　pair　of　glands；　in
  order　that　some　may　be　carried　down　to　the　posterior　parts　of　the
  intestine；　where　these　concretions　would　be　rolled　about　amongst
  the　acid　contents。　　The　concretions　found　in　the　intestines　and　in
  the　castings　often　have　a　worn　appearance；　but　whether　this　is　due
  to　some　amount　of　attrition　or　of　chemical　corrosion　could　not　be
  told。　　Claparede　believes　that　they　are　formed　for　the　sake　of
  acting　as　mill…stones；　and　of　thus　aiding　in　the　trituration　of　the
  food。　　They　may　give　some　aid　in　this　way；　but　I　fully　agree　with
  Perrier　that　this　must　be　of　quite　subordinate　importance；　seeing
  that　the　object　is　already　attained　by　stones　being　generally
  present　in　the　gizzards　and　intestines　of　worms。
  CHAPTER　IIHABITS　OF　WORMScontinued。
  Manner　in　which　worms　seize　objectsTheir　power　of　suctionThe
  instinct　of　plugging　up　the　mouths　of　their　burrowsStones　piled
  over　the　burrowsThe　advantages　thus　gainedIntelligence　shown　by
  worms　in　their　manner　of　plugging　up　their　burrowsVarious　kinds
  of　leaves　and　other　objects　thus　usedTriangles　of　paperSummary
  of　reasons　for　believing　that　worms　exhibit　some　intelligence
  Means　by　which　they　excavate　their　burrows；　by　pushing　away　the
  earth　and　swallowing　itEarth　also　swallowed　for　the　nutritious
  matter　which　it　containsDepth　to　which　worms　burrow；　and　the
  construction　of　their　burrowsBurrows　lined　with　castings；　and　in
  the　upper　part　with　leavesThe　lowest　part　paved　with　little
  stones　or　seedsManner　in　which　the　castings　are　ejectedThe
  collapse　of　old　burrowsDistribution　of　wormsTower…like　castings
  in　BengalGigantic　castings　on　the　Nilgiri　MountainsCastings
  ejected　in　all　countries。
  In　the　pots　in　which　worms　were　kept；　leaves　were　pinned　down　to
  the　soil；　and　at　night　the　manner　in　which　they　were　seized　could
  be　observed。　　The　worms　always　endeavoured　to　drag　the　leaves
  towards　their　burrows；　and　they　tore　or　sucked　off　small　fragments；
  whenever　the　leaves　were　sufficiently　tender。　　They　generally
  seized　the　thin　edge　of　a　leaf　with　their　mouths；　between　the
  projecting　upper　and　lower　lip；　the　thick　and　strong　pharynx　being
  at　the　same　time；　as　Perrier　remarks；　pushed　forward　within　their
  bodies；　so　as　to　afford　a　point　of　resistance　for　the　upper　lip。
  In　the　case　of　broad　flat　objects　they　acted　in　a　wholly　different
  manner。　　The　pointed　anterior　extremity　of　the　body；　after　being
  brought　into　contact　with　an　object　of　this　kind；　was　drawn　within
  the　adjoining　rings；　so　that　it　appeared　truncated　and　became　as
  thick　as　the　rest　of　the　body。　　This　part　could　then　be　seen　to
  swell　a　little；　and　this；　I　believe；　is　due　to　the　pharynx　being
  pushed　a　little　forwards。　　Then　by　a　slight　withdrawal　of　the
  pharynx　or　by　its　expansion；　a　vacuum　was　produced　beneath　the
  truncated　slimy　end　of　the　body　whilst　in　contact　with　the　object；
  and　by　this　means　the　two　adhered　firmly　together。　｛28｝　　That　under
  these　circumstances　a　vacuum　was　produced　was　plainly　seen　on　one
  occasion；　when　a　large　worm　lying　beneath　a　flaccid　cabbage　leaf
  tried　to　drag　it　away；　for　the　surface　of　the　leaf　directly　over
  the　end　of　the　worm's　body　became　deeply　pitted。　　On　another
  occasion　a　worm　suddenly　lost　its　hold　on　a　flat　leaf；　and　the
  anterior　end　of　the　body　was　momentarily　seen　to　be　cup…formed。
  Worms　can　attach　themselves　to　an　object　beneath　water　in　the　same
  manner；　and　I　saw　one　thus　dragging　away　a　submerged　slice　of　an
  onion…bulb。
  The　edges　of　fresh　or　nearly　fresh　leaves　affixed　to　the　ground
  were　often　nibbled　by　the　worms；　and　sometimes　the　epidermis　and
  all　the　parenchyma　on　one　side　was　gnawed　completely　away　over　a
  considerable　space；　the　epidermis　alone　on　the　opposite　side　being
  left　quite　clean。　　The　veins　were　never　touched；　and　leaves　were
  thus　sometimes　partly　converted　into　skeletons。　　As　worms　have　no
  teeth　and　as　their　mouths　consist　of　very　soft　tissue；　it　may　be
  presumed　that　they　consume　by　means　of　suction　the　edges　and　the
  parenchyma　of　fresh　leaves；　after　they　have　been　softened　by　the
  digestive　fluid。　　They　cannot　attack　such　strong　leaves　as　those　of
  sea…kale　or　large　and　thick　leaves　of　ivy；　though　one　of　the　latter
  after　it　had　become　rotten　was　reduced　in　parts　to　the　state　of　a
  skeleton。
  Worms　seize　leaves　and　other　objects；　not　only　to　serve　as　food；
  but　for　plugging　up　the　mouths　of　their　burrows；　and　this　is　one　of
  their　strongest　instincts。　　They　sometimes　work　so　energetically
  that　Mr。　D。　F。　Simpson；　who　has　a　small　walled　garden　where　worms
  abound　in　Bayswater；　informs　me　that　on　a　calm　damp　evening　he
  there　heard　so　extraordinary　a　rustling　noise　from　under　a　tree
  from　which　many　leaves　had　fallen；　that　he　went　out　with　a　light
  and　discovered　that　the　noise　was　caused　by　many　worms　dragging　the
  dry　leaves　and　squeezing　them　into　the　burrows。　　Not　only　leaves；
  but　petioles　of　many　kinds；　some　flower…peduncles；　often　decayed
  twigs　of　trees；　bits　of　paper；　feathers；　tufts　of　wool　and　horse…
  hairs　are　dragged　into　their　burrows　for　this　purpose。　　I　have　seen
  as　many　as　seventeen　petioles　of　a　Clematis　projecting　from　the
  mouth　of　one　burrow；　and　ten　from　the　mouth　of　another。　　Some　of
  these　objects；　such　as　the　petioles　just　named；　feathers；　&c。；　are
  never　gnawed　by　worms。　　In　a　gravel…walk　in　my　garden　I　found　many
  hundred　leaves　of　a　pine…tree　（P。　austriaca　or　nigricans）　drawn　by
  their　bases　into　burrows。　　The　surfaces　by　which　these　leaves　are
  articulated　to　the　branches　are　shaped　in　as　peculiar　a　manner　as
  is　the　joint　between　the　leg…bones　of　a　quadruped；　and　if　these
  surfaces　had　been　in　the　least　gnawed；　the　fact　would　have　been
  immediately　visible；　but　there　was　no　trace　of　gnawing。　　Of
  ordinary　dicotyledonous　leaves；　all　those　which　are　dragged　into
  burrows　are　not　gnawed。　　I　have　seen　as　many　as　nine　leaves　of　the
  lime…tree　drawn　into　the　same　burrow；　and　not　nearly　all　of　th