for　he　and　they　are　alike　identical　with　the　primordial　cell；　and　we
  have　already　noted　it　as　an　axiom　that　things　which　are　identical
  with　the　same　are　identical　with　one　another。　　This　is　practically
  making　him　one　with　all　living　things；　whether　animal　or　vegetable；
  that　ever　have　existed　or　ever　willsomething　of　all　which　may　have
  been　in　the　mind　of　Sophocles　when　he　wrote：…
  〃Nor　seest　thou　yet　the　gathering　hosts　of　ill
  That　shall　en…one　thee　both　with　thine　own　self
  And　with　thine　offspring。〃
  And　all　this　has　come　of　admitting　that　a　man　may　be　the　same　person
  for　two　days　running！　　As　for　sopping　common　sense　it　will　be　enough
  to　say　that　these　remarks　are　to　be　taken　in　a　strictly　scientific
  sense；　and　have　no　appreciable　importance　as　regards　life　and
  conduct。　　True　they　deal　with　the　foundations　on　which　all　life　and
  conduct　are　based；　but　like　other　foundations　they　are　hidden　out　of
  sight；　and　the　sounder　they　are；　the　less　we　trouble　ourselves　about
  them。
  What　other　main　common　features　between　heredity　and　memory　may　we
  note　besides　the　fact　that　neither　can　exist　without　that　kind　of
  physical　continuity　which　we　call　personal　identity？　　First；　the
  development　of　the　embryo　proceeds　in　an　established　order；　so　must
  all　habitual　actions　based　on　memory。　　Disturb　the　normal　order　and
  the　performance　is　arrested。　　The　better　we　know　〃God　save　the
  Queen；〃　the　less　easily　can　we　play　or　sing　it　backwards。　　The
  return　of　memory　again　depends　on　the　return　of　ideas　associated
  with　the　particular　thing　that　is　rememberedwe　remember　nothing
  but　for　the　presence　of　these；　and　when　enough　of　these　are
  presented　to　us　we　remember　everything。　　So；　if　the　development　of
  an　embryo　is　due　to　memory；　we　should　suppose　the　memory　of　the
  impregnate　ovum　to　revert　not　to　yesterday；　when　it　was　in　the
  persons　of　its　parents；　but　to　the　last　occasion　on　which　it　was　an
  impregnate　ovum。　　The　return　of　the　old　environment　and　the　presence
  of　old　associations　would　at　once　involve　recollection　of　the　course
  that　should　be　next　taken；　and　the　same　should　happen　throughout　the
  whole　course　of　development。　　The　actual　course　of　development
  presents　precisely　the　phenomena　agreeable　with　this。　　For　fuller
  treatment　of　this　point　I　must　refer　the　reader　to　the　chapter　on
  the　abeyance　of　memory　in　my　book　〃Life　and　Habit；〃　already　referred
  to。
  Secondly；　we　remember　best　our　last　few　performances　of　any　given
  kind；　so　our　present　performance　will　probably　resemble　some　one　or
  other　of　these；　we　remember　our　earlier　performances　by　way　of
  residuum　only；　but　every　now　and　then　we　revert　to　an　earlier　habit。
  This　feature　of　memory　is　manifested　in　heredity　by　the　way　in　which
  offspring　commonly　resembles　most　its　nearer　ancestors；　but
  sometimes　reverts　to　earlier　ones。　　Brothers　and　sisters；　each　as　it
  were　giving　their　own　version　of　the　same　story；　but　in　different
  words；　should　generally　resemble　each　other　more　closely　than　more
  distant　relations。　　And　this　is　what　actually　we　find。
  Thirdly；　the　introduction　of　slightly　new　elements　into　a　method
  already　established　varies　it　beneficially；　the　new　is　soon　fused
  with　the　old；　and　the　monotony　ceases　to　be　oppressive。　　But　if　the
  new　be　too　foreign；　we　cannot　fuse　the　old　and　the　newnature
  seeming　to　hate　equally　too　wide　a　deviation　from　ordinary　practice
  and　none　at　all。　　This　fact　reappears　in　heredity　as　the　beneficial
  effects　of　occasional　crossing　on　the　one　hand；　and　on　the　other；　in
  the　generally　observed　sterility　of　hybrids。　　If　heredity　be　an
  affair　of　memory；　how　can　an　embryo；　say　of　a　mule；　be　expected　to
  build　up　a　mule　on　the　strength　of　but　two　mule…memories？　　Hybridism
  causes　a　fault　in　the　chain　of　memory；　and　it　is　to　this　cause　that
  the　usual　sterility　of　hybrids　must　be　referred。
  Fourthly；　it　requires　many　repeated　impressions　to　fix　a　method
  firmly；　but　when　it　has　been　engrained　into　us　we　cease　to　have　much
  recollection　of　the　manner　in　which　it　came　to　be　so；　or　indeed　of
  any　individual　repetition；　but　sometimes　a　single　impression；　if
  prolonged　as　well　as　profound；　produces　a　lasting　impression　and　is
  liable　to　return　with　sudden　force；　and　then　to　go　on　returning　to
  us　at　intervals。　　As　a　general　rule；　however；　abnormal　impressions
  cannot　long　hold　their　own　against　the　overwhelming　preponderance　of
  normal　authority。　　This　appears　in　heredity　as　the　normal　non…
  inheritance　of　mutilations　on　the　one　hand；　and　on　the　other　as
  their　occasional　inheritance　in　the　case　of　injuries　followed　by
  disease。
  Fifthly；　if　heredity　and　memory　are　essentially　the　same；　we　should
  expect　that　no　animal　would　develop　new　structures　of　importance
  after　the　age　at　which　its　species　begins　ordinarily　to　continue　its
  race；　for　we　cannot　suppose　offspring　to　remember　anything　that
  happens　to　the　parent　subsequently　to　the　parent's　ceasing　to
  contain　the　offspring　within　itself。　　From　the　average　age；
  therefore；　of　reproduction；　offspring　should　cease　to　have　any
  farther　steady；　continuous　memory　to　fall　back　upon；　what　memory
  there　is　should　be　full　of　faults；　and　as　such　unreliable。　　An
  organism　ought　to　develop　as　long　as　it　is　backed　by　memorythat　is
  to　say；　until　the　average　age　at　which　reproduction　begins；　it
  should　then　continue　to　go　for　a　time　on　the　impetus　already
  received；　and　should　eventually　decay　through　failure　of　any　memory
  to　support　it；　and　tell　it　what　to　do。　　This　corresponds　absolutely
  with　what　we　observe　in　organisms　generally；　and　explains；　on　the
  one　hand；　why　the　age　of　puberty　marks　the　beginning　of　completed
  developmenta　riddle　hitherto　not　only　unexplained　but；　so　far　as　I
  have　seen；　unasked；　it　explains；　on　the　other　hand；　the　phenomena　of
  old　agehitherto　without　even　attempt　at　explanation。
  Sixthly；　those　organisms　that　are　the　longest　in　reaching　maturity
  should　on　the　average　be　the　longest…lived；　for　they　will　have
  received　the　most　momentous　impulse　from　the　weight　of　memory　behind
  them。　　This　harmonises　with　the　latest　opinion　as　to　the　facts。　　In
  his　article　on　Weismann　in　the　Contemporary　Review　for　May　1890；　Mr。
  Romanes　writes：　　〃Professor　Weismann　has　shown　that　there　is
  throughout　the　metazoa　a　general　correlation　between　the　natural
  lifetime　of　individuals　composing　any　given　species；　and　the　age　at
  which　they　reach　maturity　or　first　become　capable　of　procreation。〃
  This；　I　believe；　has　been　the　conclusion　generally　arrived　at　by
  biologists　for　some　years　past。
  Lateness；　then；　in　the　average　age　of　reproduction　appears　to　be　the
  principle　underlying　longevity。　　There　does　not　appear　at　first
  sight　to　be　much　connection　between　such　distinct　and　apparently
  disconnected　phenomena　as　1；　the　orderly　normal　progress　of
  development；　2；　atavism　and　the　resumption　of　feral　characteristics；
  3；　the　more　ordinary　resemblance　inter　se　of　nearer　relatives；　4；
  the　benefit　of　an　occasional　cross；　and　the　usual　sterility　of
  hybrids；　5；　the　unconsciousness　with　which　alike　bodily　development
  and　ordinary　physiological　functions　proceed；　so　long　as　they　are
  normal；　6；　the　ordinary　non…inheritance；　but　occasional　inheritance
  of　mutilations；　7；　the　fact　that　puberty　indicates　the　approach　of
  maturity；　8；　the　phenomena　of　middle　life　and　old　age；　9；　the
  principle　underlying　longevity。　　These　phenomena　have　no　conceivable
  bearing　on　one　another　until　heredity　and　memory　are　regarded　as
  part　of　the　same　story。　　Identify　these　two　things；　and　I　know　no
  phenomenon　of　heredity　that　does　not　immediately　become　infinitely
  more　intelligible。　　Is　it　conceivable　that　a　theory　which　harmonises
  so　many　facts　hitherto　regarded　as　without　either　connection　or
  explanation　should　not　deserve　at　any　rate　consideration　from　those
  who　profess　to　take　an　interest　in　biology？
  It　is　not　as　though　the　theory　were　unknown；　or　had　been　condemned
  by　our　leading　men　of　science。　　Professor　Ray　Lankester　introduced
  it　to　English　readers　in　an　appreciative　notice　of　Professor
  Hering's　address；　which　appeared　in　Nature；　July　18；　1876。　　He　wrote
  to　the　Athenaeum；　March　24；　1884；　and　claimed　credit　for　having　done
  so；　but　I　do　not　believe　he　has　ever　said　more　in　public　about　it
  than　what　I　have　here　referred　to。　　Mr。　Romanes　did　indeed　try　to
  crush　it　in　Nature；　January　27；　1881；　but　in　1883；　in　his　〃Mental
  Evolution　in　Animals；〃　he　adopted　its　main　conclusion　without
  acknowledgment。　　The　Athenaeum；　to　my　unbounded　surprise；　called　him
  to　task　for　this　（March　1；　1884）；　and　since　that　time　he　has　given
  the　Heringian　theory　a　sufficiently　wide　berth。　　Mr。　Wallace　showed
  himself　favourably　enough　disposed　towards　the　view　that　heredity
  and　memory　are　part　of　the　same　story　when　he　reviewed　my　book　〃Life
  and　Habit〃　in　Nature；　March　27；　1879；　but　he　has　never　since
  betrayed　any　sign　of　being　aware　that　such　a　theory　existed。　　Mr。
  Herbert　Spencer　wrote　to　the　Athenaeum　（April　5；　1884）；　and　claimed
  the　theory　for　himself；　but；　in　spite　of　his　doing　this；　he　has
  never；　that　I　have　seen；　referred　to　the　matter　again。　　I　have　dealt
  sufficiently　with　his　claim　in　my　book；　〃Luck　or　Cunning。〃　｛43｝
  Lastly；　Professor　Hering　himself　has　never　that　I　know　of　touche