the　conditions　on　which　it　depends；　I　say　that　we　have　no　right　to
  affirm　that　those　conditions　will　not　be　better　understood　by　and　by；
  and　we　have　no　ground　for　supposing　that　we　may　not　be　able　to
  experiment　so　as　to　obtain　that　crucial　result　which　I　mentioned　just
  now。　　So　that　though　Mr。　　Darwin's　hypothesis　does　not　completely
  extricate　us　from　this　difficulty　at　present；　we　have　not　the　least
  right　to　say　it　will　not　do　so。
  There　is　a　wide　gulf　between　the　thing　you　cannot　explain　and　the　thing
  that　upsets　you　altogether。　　There　is　hardly　any　hypothesis　in　this
  world　which　has　not　some　fact　in　connection　with　it　which　has　not　been
  explained；　but　that　is　a　very　different　affair　to　a　fact　that　entirely
  opposes　your　hypothesis；　in　this　case　all　you　can　say　is；　that　your
  hypothesis　is　in　the　same　position　as　a　good　many　others。
  Now；　as　to　the　third　test；　that　there　are　no　other　causes　competent　to
  explain　the　phenomena；　I　explained　to　you　that　one　should　be　able　to
  say　of　an　hypothesis；　that　no　other　known　causes　than　those　supposed　by
  it　are　competent　to　give　rise　to　the　phenomena。　　Here；　I　think；　Mr。
  Darwin's　view　is　pretty　strong。　　I　really　believe　that　the　alternative
  is　either　Darwinism　or　nothing；　for　I　do　not　know　of　any　rational
  conception　or　theory　of　the　organic　universe　which　has　any　scientific
  position　at　all　beside　Mr。　Darwin's。　　I　do　not　know　of　any　proposition
  that　has　been　put　before　us　with　the　intention　of　explaining　the
  phenomena　of　organic　nature；　which　has　in　its　favour　a　thousandth　part
  of　the　evidence　which　may　be　adduced　in　favour　of　Mr。　Darwin's　views。
  Whatever　may　be　the　objections　to　his　views；　certainly　all　others　are
  absolutely　out　of　court。
  Take　the　Lamarckian　hypothesis；　for　example。　　Lamarck　was　a　great
  naturalist；　and　to　a　certain　extent　went　the　right　way　to　work；　he
  argued　from　what　was　undoubtedly　a　true　cause　of　some　of　the　phenomena
  of　organic　nature。　　He　said　it　is　a　matter　of　experience　that　an　animal
  may　be　modified　more　or　less　in　consequence　of　its　desires　and
  consequent　actions。　Thus；　if　a　man　exercise　himself　as　a　blacksmith；
  his　arms　will　become　strong　and　muscular；　such　organic　modification　is
  a　result　of　this　particular　action　and　exercise。　　Lamarck　thought　that
  by　a　very　simple　supposition　based　on　this　truth　he　could　explain　the
  origin　of　the　various　animal　species：　he　said；　for　example；　that　the
  short…legged　birds　which　live　on　fish　had　been　converted　into　the
  long…legged　waders　by　desiring　to　get　the　fish　without　wetting　their
  bodies；　and　so　stretching　their　legs　more　and　more　through　successive
  generations。　　If　Lamarck　could　have　shown　experimentally；　that　even
  races　of　animals　could　be　produced　in　this　way；　there　might　have　been
  some　ground　for　his　speculations。　　But　he　could　show　nothing　of　the
  kind；　and　his　hypothesis　has　pretty　well　dropped　into　oblivion；　as　it
  deserved　to　do。　　I　said　in　an　earlier　lecture　that　there　are　hypotheses
  and　hypotheses；　and　when　people　tell　you　that　Mr。　　Darwin's
  strongly…based　hypothesis　is　nothing　but　a　mere　modification　of
  Lamarck's；　you　will　know　what　to　think　of　their　capacity　for　forming　a
  judgment　on　this　subject。
  But　you　must　recollect　that　when　I　say　I　think　it　is　either　Mr。　Darwin's
  hypothesis　or　nothing；　that　either　we　must　take　his　view；　or　look　upon
  the　whole　of　organic　nature　as　an　enigma；　the　meaning　of　which　is
  wholly　hidden　from　us；　you　must　understand　that　I　mean　that　I　accept　it
  provisionally；　in　exactly　the　same　way　as　I　accept　any　other　hypothesis。
  Men　of　science　do　not　pledge　themselves　to　creeds；　they　are　bound　by
  articles　of　no　sort；　there　is　not　a　single　belief　that　it　is　not　a
  bounden　duty　with　them　to　hold　with　a　light　hand　and　to　part　with　it
  cheerfully；　the　moment　it　is　really　proved　to　be　contrary　to　any　fact；
  great　or　small。　　And　if；　in　course　of　time　I　see　good　reasons　for　such
  a　proceeding；　I　shall　have　no　hesitation　in　coming　before　you；　and
  pointing　out　any　change　in　my　opinion　without　finding　the　slightest
  occasion　to　blush　for　so　doing。　　So　I　say　that　we　accept　this　view　as
  we　accept　any　other；　so　long　as　it　will　help　us；　and　we　feel　bound　to
  retain　it　only　so　long　as　it　will　serve　our　great　purposethe
  improvement　of　Man's　estate　and　the　widening　of　his　knowledge。　　The
  moment　this；　or　any　other　conception；　ceases　to　be　useful　for　these
  purposes；　away　with　it　to　the　four　winds；　we　care　not　what　becomes　of
  it！
  But　to　say　truth；　although　it　has　been　my　business　to　attend　closely　to
  the　controversies　roused　by　the　publication　of　Mr。　Darwin's　book；　I
  think　that　not　one　of　the　enormous　mass　of　objections　and　obstacles
  which　have　been　raised　is　of　any　very　great　value；　except　that
  sterility　case　which　I　brought　before　you　just　now。　　All　the　rest　are
  misunderstandings　of　some　sort；　arising　either　from　prejudice；　or　want
  of　knowledge；　or　still　more　from　want　of　patience　and　care　in　reading
  the　work。
  For　you　must　recollect　that　it　is　not　a　book　to　be　read　with　as　much
  ease　as　its　pleasant　style　may　lead　you　to　imagine。　　You　spin　through
  it　as　if　it　were　a　novel　the　first　time　you　read　it；　and　think　you　know
  all　about　it；　the　second　time　you　read　it　you　think　you　know　rather
  less　about　it；　and　the　third　time；　you　are　amazed　to　find　how　little
  you　have　really　apprehended　its　vast　scope　and　objects。　　I　can
  positively　say　that　I　never　take　it　up　without　finding　in　it　some　new
  view；　or　light；　or　suggestion　that　I　have　not　noticed　before。　　That　is
  the　best　characteristic　of　a　thorough　and　profound　book；　and　I　believe
  this　feature　of　the　'Origin　of　Species'　explains　why　so　many　persons
  have　ventured　to　pass　judgment　and　criticisms　upon　it　which　are　by　no
  means　worth　the　paper　they　are　written　on。
  Before　concluding　these　lectures　there　is　one　point　to　which　I　must
  advert；though；　as　Mr。　　Darwin　has　said　nothing　about　man　in　his　book；
  it　concerns　myself　rather　than　him；for　I　have　strongly　maintained　on
  sundry　occasions　that　if　Mr。　Darwin's　views　are　sound；　they　apply　as
  much　to　man　as　to　the　lower　mammals；　seeing　that　it　is　perfectly
  demonstrable　that　the　structural　differences　which　separate　man　from
  the　apes　are　not　greater　than　those　which　separate　some　apes　from
  others。　　There　cannot　be　the　slightest　doubt　in　the　world　that　the
  argument　which　applies　to　the　improvement　of　the　horse　from　an　earlier
  stock；　or　of　ape　from　ape；　applies　to　the　improvement　of　man　from　some
  simpler　and　lower　stock　than　man。　　There　is　not　a　single
  facultyfunctional　or　structural；　moral；　intellectual；　or
  instinctive；there　is　no　faculty　whatever　that　is　not　capable　of
  improvement；　there　is　no　faculty　whatsoever　which　does　not　depend　upon
  structure；　and　as　structure　tends　to　vary；　it　is　capable　of　being
  improved。
  Well；　I　have　taken　a　good　deal　of　pains　at　various　times　to　prove　this；
  and　I　have　endeavoured　to　meet　the　objections　of　those　who　maintain；
  that　the　structural　differences　between　man　and　the　lower　animals　are
  of　so　vast　a　character　and　enormous　extent；　that　even　if　Mr。　Darwin's
  views　are　correct；　you　cannot　imagine　this　particular　modification　to
  take　place。　　It　is；　in　fact；　easy　matter　to　prove　that；　so　far　as
  structure　is　concerned；　man　differs　to　no　greater　extent　from　the
  animals　which　are　immediately　below　him　than　these　do　from　other　members
  of　the　same　order。　　Upon　the　other　hand；　there　is　no　one　who　estimates
  more　highly　than　I　do　the　dignity　of　human　nature；　and　the　width　of　the
  gulf　in　intellectual　and　moral　matters；　which　lies　between　man　and　the
  whole　of　the　lower　creation。
  But　I　find　this　very　argument　brought　forward　vehemently　by　some。　　〃You
  say　that　man　has　proceeded　from　a　modification　of　some　lower　animal；
  and　you　take　pains　to　prove　that　the　structural　differences　which　are
  said　to　exist　in　his　brain　do　not　exist　at　all；　and　you　teach　that　all
  functions；　intellectual；　moral；　and　others；　are　the　expression　or　the
  result；　in　the　long　run；　of　structures；　and　of　the　molecular　forces
  which　they　exert。〃　　It　is　quite　true　that　I　do　so。
  〃Well；　but；〃　I　am　told　at　once；　somewhat　triumphantly；　〃you　say　in　the
  same　breath　that　there　is　a　great　moral　and　intellectual　chasm　between
  man　and　the　lower　animals。　　How　is　this　possible　when　you　declare　that
  moral　and　intellectual　characteristics　depend　on　structure；　and　yet
  tell　us　that　there　is　no　such　gulf　between　the　structure　of　man　and　that
  of　the　lower　animals？〃
  I　think　that　objection　is　based　upon　a　misconception　of　the　real
  relations　which　exist　between　structure　and　function；　between　mechanism
  and　work。　　Function　is　the　expression　of　molecular　forces　and
  arrangements　no　doubt；　but；　does　it　follow　from　this；　that　variation　in
  function　so　depends　upon　variation　in　structure　that　the　former　is
  always　exactly　proportioned　to　the　latter？　　If　there　is　no　such
  relation；　if　the　variation　in　function　which　follows　on　a　variation　in
  structure；　may　be　enormously　greater　than　the　variation　of　the
  structure；　then；　you　see；　the　objection　falls　to　the　ground。
  Take　a　couple　of　watchesmade　by　the　same　maker；　and　as　completely
  alike　as　possible；　set　them　upon　the　table；　and　the　function　of
  eachwhich　is　its　rate　of　goingwill　be　performed　in　the　sam