SurelyifdisusecanbecreditedwiththevastpowersinvolvedinMr。Darwin’sstatementthatithasprobably\"beenthemainagentinrenderingorgansrudimentary,\"nolimitsareassignabletotheaccumulatedeffectsofhabit,providedtheeffectsofhabit,oruseanddisuse,aresupposed,asMr。Darwinsupposedthem,tobeinheritableatall。DarwinianshaveatlengthwokeuptothedilemmainwhichtheyareplacedbythemannerinwhichMr。Darwintriedtositonthetwostoolsofuseanddisuse,andnaturalselectionofaccidentalvariations,atthesametime。TheknellofCharles-DarwinismisrunginMr。Wallace’spresentbook,andinthegeneralperceptiononthepartofbiologiststhatwemusteitherassigntouseanddisusesuchapredominantshareinmodificationastomakeitthefeaturemostpropertobeinsistedon,ordenythatthemodifications,whetherofmindorbody,acquiredduringasinglelifetime,areevertransmittedatall。Iftheycanbeinheritedatall,theycanbeaccumulated。Iftheycanbeaccumulatedatall,theycanbeso,foranythingthatappearstothecontrary,totheextentofthespecificandgenericdifferenceswithwhichwearesurrounded。Theonlythingtodoistopluckthemoutrootandbranch:theyareasacancerwhich,ifthesmallestfibrebeleftunexcised,willgrowagain,andkillanysystemontowhichitisallowedtofasten。Mr。Wallace,therefore,maywellbeexcusedifhecastslongingeyestowardsWeismannism。
AndwhatwasMr。Darwin’ssystem?Whocanmakeheadortailoftheinextricablemuddleinwhichheleftit?The\"OriginofSpecies\"initslatestshapeisthereductionofhedgingtoanabsurdity。HowdidMr。Darwinhimselfleaveitinthelastchapterofthelasteditionofthe\"OriginofSpecies\"?Hewrote:-
\"Ihavenowrecapitulatedthefactsandconsiderationswhichhavethoroughlyconvincedmethatspecieshavebeenmodifiedduringalongcourseofdescent。Thishasbeeneffectedchieflythroughthenaturalselectionofnumerous,successive,slight,favourablevariations;aidedinanimportantmannerbytheinheritedeffectsoftheuseanddisuseofparts,andinanunimportantmanner——thatis,inrelationtoadaptivestructureswhetherpastorpresent——bythedirectactionofexternalconditions,andbyvariationswhichseemtousinourignorancetoarisespontaneously。ItappearsthatI
formerlyunderratedthefrequencyandvalueoftheselatterformsofvariation,asleadingtopermanentmodificationsofstructureindependentlyofnaturalselection。\"
The\"numerous,successive,slight,favourablevariations\"abovereferredtoareintendedtobefortuitous,accidental,spontaneous。
ItistheessenceofMr。Darwin’stheorythatthisshouldbeso。
Mr。Darwin’ssolemnstatement,therefore,ofhistheory,afterhehaddonehisbestorhisworstwithit,is,whenstrippedofsurplusage,asfollows:-
\"Themodificationofspecieshasbeenmainlyeffectedbyaccumulationofspontaneousvariations;ithasbeenaidedinanimportantmannerbyaccumulationofvariationsduetouseanddisuse,andinanunimportantmannerbyspontaneousvariations;Idonotevennowthinkthatspontaneousvariationshavebeenveryimportant,butIusedoncetothinkthemlessimportantthanIdonow。\"
Itisadiscouragingsymptomoftheagethatsuchasystemshouldhavebeensolongbelauded,anditisasignofreturningintelligencethatevenhewhohasbeenmoreespeciallythealteregoofMr。DarwinshouldhavefeltconstrainedtoclosethechapterofCharles-Darwinismasalivingtheory,andrelegateittotheimportantbutnotverycreditableplaceinhistorywhichitmusthenceforthoccupy。Itisastonishing,however,thatMr。Wallaceshouldhavequotedtheextractfromthe\"OriginofSpecies\"justgiven,ashehasdoneonp。412ofhis\"Darwinism,\"withoutbetrayinganysignthathehascaughtitsdriftlessness——fordrift,otherthanadesiretohedge,itassuredlyhasnotgot。Thebattlenowturnsonthequestionwhethermodificationsofeitherstructureorinstinctduetouseordisuseareeverinherited,orwhethertheyarenot。Cantheeffectsofhabitbetransmittedtoprogenyatall?
Weknowthatmoreusuallytheyarenottransmittedtoanyperceptibleextent,butwebelievealsothatoccasionally,andindeednotinfrequently,theyareinheritedandevenintensified。
Whatareourgroundsforthisopinion?ItwillbemyobjecttoputtheseforwardinthefollowingnumberoftheUniversalReview。
THEDEADLOCKINDARWINISM——PARTII{29}
Atthecloseofmyarticleinlastmonth’snumberoftheUniversalReview,IsaidIwouldinthismonth’sissueshowwhytheopponentsofCharles-Darwinismbelievetheeffectsofhabitsacquiredduringthelifetimeofaparenttoproduceaneffectontheirsubsequentoffspring,inspiteofthefactthatwecanrarelyfindtheeffectinanyonegeneration,oreveninseveral,sufficientlymarkedtoarrestourattention。
Iwillnowshowthatoffspringcanbe,andnotveryinfrequentlyis,affectedbyoccurrencesthathaveproducedadeepimpressionontheparentorganism——theeffectproducedontheoffspringbeingsuchasleavesnodoubtthatitistobeconnectedwiththeimpressionproducedontheparent。Havingthusestablishedthegeneralproposition,Iwillproceedtothemoreparticularone——thathabits,involvinguseanddisuseofspecialorgans,withthemodificationsofstructuretherebyengendered,producealsoaneffectuponoffspring,which,thoughseldomperceptibleasregardsstructureinasingle,oreveninseveralgenerations,isneverthelesscapableofbeingaccumulatedinsuccessivegenerationstillitamountstospecificandgenericdifference。IhavefoundthefirstpointasmuchasIcantreatwithinthelimitsofthispresentarticle,andwillavailmyselfofthehospitalityoftheUniversalReviewnextmonthtodealwiththesecond。
ThepropositionwhichIhavetodefendisonewhichnoonetillrecentlywouldhavequestioned,andevennow,thosewholookmostaskanceatitdonotventuretodisputeitunreservedly;theyeverynowandthenadmititasconceivable,andeveninsomecasesprobable;neverthelesstheyseektominimiseit,andtomakeoutthatthereislittleornoconnectionbetweenthegreatmassofthecellsofwhichthebodyiscomposed,andthosecellsthatarealonecapableofreproducingtheentireorganism。Thetendencyistoassigntotheselastalifeoftheirown,apartfrom,andunconnectedwiththatoftheothercellsofthebody,andtocheapenallevidencethattendstoproveanyresponseontheirparttothepasthistoryoftheindividual,andhenceultimatelyoftherace。
ProfessorWeismannistheforemostexponentofthosewhotakethisline。HehasnaturallybeenwelcomedbyEnglishCharles-Darwinians;
forifhisviewcanbesustained,thenitcanbecontendedthatuseanddisuseproducenotransmissibleeffect,andthegroundiscutfromunderLamarck’sfeet;if,ontheotherhand,hisviewisunfounded,theLamarckianreaction,alreadystrong,willgainstillfurtherstrength。Theissue,therefore,isimportant,andisbeingfiercelycontestedbythosewhohaveinvestedtheirallofreputationfordiscernmentinCharles-Darwiniansecurities。
ProfessorWeismann’stheoryis,thatateverynewbirthapartofthesubstancewhichproceedsfromparentsandwhichgoestoformthenewembryoisnotusedupinformingthenewanimal,butremainsaparttogeneratethegerm-cells——orperhapsIshouldsay\"germ-
plasm\"——whichthenewanimalitselfwillinduecourseissue。
Contrastingthegenerallyreceivedviewwithhisown,ProfessorWeismannsaysthataccordingtothefirstofthese\"theorganismproducesgerm-cellsafreshagainandagain,andthatitproducesthementirelyfromitsownsubstance。\"Whilebythesecond\"thegerm-cellsarenolongerlookeduponastheproductoftheparent’sbody,atleastasfarastheiressentialpart——thespecificgerm-
plasm——isconcerned;theyareratherconsideredassomethingwhichistobeplacedincontrastwiththetoutensembleofthecellswhichmakeuptheparent’sbody,andthegerm-cellsofsucceedinggenerationsstandinasimilarrelationtooneanotherasaseriesofgenerationsofunicellularorganismsarisingbyacontinuedprocessofcell-division。\"{30}
Onanotherpagehewrites:-
\"Ibelievethathereditydependsuponthefactthatasmallportionoftheeffectivesubstanceofthegerm,thegerm-plasm,remainsunchangedduringthedevelopmentoftheovumintoanorganism,andthatthispartofthegerm-plasmservesasafoundationfromwhichthegerm-cellsoftheneworganismareproduced。Thereis,therefore,continuityofthegerm-plasmfromonegenerationtoanother。Onemightrepresentthegerm-plasmbythemetaphorofalongcreepingroot-stockfromwhichplantsariseatintervals,theselatterrepresentingtheindividualsofsuccessivegenerations。\"{31}
Mr。Wallace,whodoesnotappeartohavereadProfessorWeismann’sessaysthemselves,butwhoseremarksare,nodoubt,ultimatelyderivedfromthesequeltothepassagejustquotedfrompage266ofProfessorWeismann’sbook,contendsthattheimpossibilityofthetransmissionofacquiredcharactersfollowsasalogicalresultfromProfessorWeismann’stheory,inasmuchasthemolecularstructureofthegerm-plasmthatwillgotoformanysucceedinggenerationisalreadypredeterminedwithinthestillunformedembryoofitspredecessor;\"andWeismann,\"continuesMr。Wallace,\"holdsthattherearenofactswhichreallyprovethatacquiredcharacterscanbeinherited,althoughtheirinheritancehas,bymostwriters,beenconsideredsoprobableashardlytostandinneedofdirectproof。\"
{32}
ProfessorWeismann,inpassagestoonumeroustoquote,showsthatherecognisesthisnecessity,andacknowledgesthatthenon-
transmissionofacquiredcharacters\"formsthefoundationoftheviews\"setforthinhisbook,p。291。
ProfessorRayLankesterdoesnotcommithimselfabsolutelytothisview,butlendsitsupportbysaying(Nature,December12,1889):
\"ItishardlynecessarytosaythatithasneveryetbeenshownexperimentallythatANYTHINGacquiredbyonegenerationistransmittedtothenext(puttingasidediseases)。\"
Mr。Romanes,writinginNature,March18,1890,andopposingcertaindetailsofProfessorWeismann’stheory,sofarsupportsitastosaythat\"thereisthegravestpossibledoubtlyingagainstthesuppositionthatanyreallyinheriteddecreaseisduetotheinheritedeffectsofdisuse。\"The\"gravestpossibledoubt\"shouldmeanthatMr。Romanesregardsitasamoralcertaintythatdisusehasnotransmittedeffectinreducinganorgan,anditshouldfollowthatheholdsusetohavenotransmittedeffectinitsdevelopment。
Thesequel,however,makesmeuncertainhowfarMr。Romanesintendsthis,andIwouldreferthereadertothearticlewhichMr。RomaneshasjustpublishedonWeismannintheContemporaryReviewforthiscurrentmonth。
TheburdenofMr。ThiseltonDyer’scontroversywiththeDukeofArgyll(seeNature,January16,1890,etseq。)wasthattherewasnoevidenceinsupportofthetransmissionofanyacquiredmodification。Theorthodoxyofscience,therefore,mustbeheldasgivingatanyrateaprovisionalsupporttoProfessorWeismann,butallofthem,includingevenProfessorWeismannhimself,shrinkfromcommittingthemselvestotheopinionthatthegerm-cellsofanyorganismsremaininallcasesunaffectedbytheeventsthatoccurtotheothercellsofthesameorganism,anduntiltheydothistheyhaveknockedthebottomoutoftheircase。
FromamongthepassagesinwhichProfessorWeismannhimselfshowsadesiretohedgeImaytakethefollowingfrompage170ofhisbook:-
\"Iamalsofarfromassertingthatthegerm-plasmwhich,asIhold,istransmittedasthebasisofheredityfromonegenerationtoanother,isabsolutelyunchangeableortotallyuninfluencedbyforcesresidingintheorganismwithinwhichitistransformedintogerm-cells。Iamalsocompelledtoadmititasconceivablethatorganismsmayexertamodifyinginfluenceupontheirgerm-cells,andeventhatsuchaprocessistoacertainextentinevitable。Thenutritionandgrowthoftheindividualmustexercisesomeinfluenceuponitsgerm-cells……\"
ProfessorWeismanndoesindeedgoontosaythatthisinfluencemustbeextremelyslight,butwedonotcarehowslightthechangesproducedmaybeprovidedtheyexistandcanbetransmitted。Onanearlierpage(p。101)hesaidinregardtovariationsgenerallythatweshouldnotexpecttofindthemconspicuous;theirfrequencywouldbeenough,iftheycouldbeaccumulated。Thesameapplieshere,ifstirringeventsthatoccurtothesomaticcellscanproduceanyeffectatallonoffspring。Averysmalleffect,provideditcanberepeatedandaccumulatedinsuccessivegenerations,isallthateventhemostexactingLamarckianwillaskfor。
HavingnowmadethereaderacquaintedwiththepositiontakenbytheleadingCharles-Darwinianauthorities,IwillreturntoProfessorWeismannhimself,whodeclaresthatthetransmissionofacquiredcharacters\"atfirstsightcertainlyseemsnecessary,\"andthat\"itappearsrashtoattempttodispensewithitsaid。\"Hecontinues:-
\"Manyphenomenaonlyappeartobeintelligibleifweassumethehereditarytransmissionofsuchacquiredcharactersasthechangeswhichweascribetotheuseordisuseofparticularorgans,ortothedirectinfluenceofclimate。Furthermore,howcanweexplaininstinctashereditaryhabit,unlessithasgraduallyarisenbytheaccumulation,throughheredity,ofhabitswhichwerepractisedinsucceedinggenerations?\"{33}
ImaysayinpassingthatProfessorWeismannappearstosupposethattheviewofinstinctjustgivenispartoftheCharles-Darwiniansystem,foronpage889ofhisbookhesays\"thatmanyobservershadfollowedDarwininexplainingthem[instincts]asinheritedhabits。\"
ThiswasnotMr。Darwin’sownviewofthematter。Hewrote:-
\"Ifwesupposeanyhabitualactiontobecomeinherited——andIthinkitcanbeshownthatthisdoessometimeshappen——thentheresemblancebetweenwhatoriginallywasahabitandaninstinctbecomessocloseasnottobedistinguished……Butitwouldbethemostseriouserrortosupposethatthegreaternumberofinstinctshavebeenacquiredbyhabitinonegeneration,andthentransmittedbyinheritancetosucceedinggenerations。Itcanbeclearlyshownthatthemostwonderfulinstinctswithwhichweareacquainted,namely,thoseofthehive-beeandofmanyants,couldnotpossiblyhavebeenthusacquired。\"——[\"OriginofSpecies,\"ed。,1859,p。209。]
Againweread:\"Domesticinstinctsaresometimesspokenofasactionswhichhavebecomeinheritedsolelyfromlong-continuedandcompulsoryhabit,butthis,Ithink,isnottrue。\"——Ibid。,p。214。
Again:\"Iamsurprisedthatnoonehasadvancedthisdemonstrativecaseofneuterinsects,againstthewell-knowndoctrineofinheritedhabit,asadvancedbyLamarck。\"——[\"OriginofSpecies,\"ed。1872,p。
283。]
IamnotawarethatLamarckadvancedthedoctrinethatinstinctisinheritedhabit,buthemayhavedonesoinsomeworkthatIhavenotseen。
Itistrue,asIhavemorethanoncepointedout,thatinthelatereditionsofthe\"OriginofSpecies\"itisnolonger\"theMOST
serious\"errortoreferinstinctsgenerallytoinheritedhabit,butitstillremains\"aseriouserror,\"andthisslightrelaxationofseveritydoesnotwarrantProfessorWeismanninascribingtoMr。
Darwinanopinionwhichheemphaticallycondemned。Histone,however,issooffhand,thatthosewhohavelittleacquaintancewiththeliteratureofevolutionwouldhardlyguessthatheisnotmuchbetterinformedonthissubjectthanthemselves。
Returningtotheinheritanceofacquiredcharacters,ProfessorWeismannsaysthatthishasneverbeenprovedeitherbymeansofdirectobservationorbyexperiment。\"Itmustbeadmitted,\"hewrites,\"thatthereareinexistencenumerousdescriptionsofcaseswhichtendtoprovethatsuchmutilationsasthelossoffingers,thescarsofwounds,&c。,areinheritedbytheoffspring,butinthesedescriptionstheprevioushistoryisinvariablyobscure,andhencetheevidencelosesallscientificvalue。\"
TheexperimentsofM。Brown-SequardthrowsomuchlightuponthequestionatissuethatIwillquoteatsomelengthfromthesummarygivenbyMr。Darwininhis\"VariationofAnimalsandPlantsunderDomestication。\"{34}Mr。Darwinwrites:-
\"Withrespecttotheinheritanceofstructuresmutilatedbyinjuriesoralteredbydisease,itwasuntillatelydifficulttocometoanydefiniteconclusion。\"[Thenfollowseveralcasesinwhichmutilationspractisedformanygenerationsarenotfoundtobetransmitted。]\"Notwithstanding,\"continuesMr。Darwin,\"theaboveseveralnegativecases,wenowpossessconclusiveevidencethattheeffectsofoperationsaresometimesinherited。Dr。Brown-Sequardgivesthefollowingsummaryofhisobservationsonguinea-pigs,andthissummaryissoimportantthatIwillquotethewhole:-
\"’1st。Appearanceofepilepsyinanimalsbornofparentshavingbeenrenderedepilepticbyaninjurytothespinalcord。
\"’2nd。Appearanceofepilepsyalsoinanimalsbornofparentshavingbeenrenderedepilepticbythesectionofthesciaticnerve。
\"’3rd。Achangeintheshapeoftheearinanimalsbornofparentsinwhichsuchachangewastheeffectofadivisionofthecervicalsympatheticnerve。
\"’4th。Partialclosureoftheeyelidsinanimalsbornofparentsinwhichthatstateoftheeyelidshadbeencausedeitherbythesectionofthecervicalsympatheticnerveortheremovalofthesuperiorcervicalganglion。
\"’5th。Exophthalmiainanimalsbornofparentsinwhichaninjurytotherestiformbodyhadproducedthatprotrusionoftheeyeball。
ThisinterestingfactIhavewitnessedagoodmanytimes,andIhaveseenthetransmissionofthemorbidstateoftheeyecontinuethroughfourgenerations。Intheseanimalsmodifiedbyheredity,thetwoeyesgenerallyprotruded,althoughintheparentsusuallyonlyoneshowedexophthalmia,thelesionhavingbeenmadeinmostcasesonlyononeofthecorporarestiformia。
\"’6th。Haematomaanddrygangreneoftheearsinanimalsbornofparentsinwhichtheseear-alterationshadbeencausedbyaninjurytotherestiformbodynearthenibofthecalamus。
\"’7th。Absenceoftwotoesoutofthethreeofthehindleg,andsometimesofthethree,inanimalswhoseparentshadeatenuptheirhind-legtoeswhichhadbecomeanaestheticfromasectionofthesciaticnervealone,orofthatnerveandalsoofthecrural。
Sometimes,insteadofcompleteabsenceofthetoes,onlyapartofoneortwoorthreewasmissingintheyoung,althoughintheparentnotonlythetoesbutthewholefootwasabsent(partlyeatenoff,partlydestroyedbyinflammation,ulceration,organgrene)。
\"’8th。Appearanceofvariousmorbidstatesoftheskinandhairoftheneckandfaceinanimalsbornofparentshavinghadsimilaralterationsinthesameparts,aseffectsofaninjurytothesciaticnerve。’
\"ItshouldbeespeciallyobservedthatBrown-Sequardhasbredduringthirtyyearsmanythousandguinea-pigsfromanimalswhichhadnotbeenoperatedupon,andnotoneofthesemanifestedtheepileptictendency。Norhasheeverseenaguinea-pigbornwithouttoes,whichwasnottheoffspringofparentswhichhadgnawedofftheirowntoesowingtothesciaticnervehavingbeendivided。Ofthislatterfactthirteeninstanceswerecarefullyrecorded,andagreaternumberwereseen;yetBrown-Sequardspeaksofsuchcasesasoneoftherarerformsofinheritance。Itisastillmoreinterestingfact,’thatthesciaticnerveinthecongenitallytoelessanimalhasinheritedthepowerofpassingthroughallthedifferentmorbidstateswhichhaveoccurredinoneofitsparentsfromthetimeofthedivisiontillafteritsreunionwiththeperiphericend。Itisnot,therefore,simplythepowerofperforminganactionwhichisinherited,butthepowerofperformingawholeseriesofactions,inacertainorder。’
\"InmostofthecasesofinheritancerecordedbyBrown-Sequardonlyoneofthetwoparentshadbeenoperateduponandwasaffected。Heconcludesbyexpressinghisbeliefthat’whatistransmittedisthemorbidstateofthenervoussystem,’duetotheoperationperformedontheparents。\"
Mr。Darwinproceedstogiveotherinstancesofinheritedeffectsofmutilations:-
\"Withthehorsethereseemshardlyadoubtthatexostosesonthelegs,causedbytoomuchtravellingonhardroads,areinherited。
Blumenbachrecordsthecaseofamanwhohadhislittlefingerontherighthandalmostcutoff,andwhichinconsequencegrewcrooked,andhissonshadthesamefingeronthesamehandsimilarlycrooked。Asoldier,fifteenyearsbeforehismarriage,losthislefteyefrompurulentophthalmia,andhistwosonsweremicrophthalmiconthesameside。\"
ThelateProfessorRolleston,whosecompetenceasanobservernooneislikelytodispute,gaveMr。Darwintwocasesashavingfallenunderhisownnotice,oneofamanwhosekneehadbeenseverelywounded,andwhosechildwasbornwiththesamespotmarkedorscarred,andtheotherofonewhowasseverelycutuponthecheek,andwhosechildwasbornscarredinthesameplace。Mr。Darwin’sconclusionwasthat\"theeffectsofinjuries,especiallywhenfollowedbydisease,orperhapsexclusivelywhenthusfollowed,areoccasionallyinherited。\"
LetusnowseewhatProfessorWeismannhastosayagainstthis。Hewrites:-
\"Theonlycasesworthyofdiscussionarethewell-knownexperimentsuponguinea-pigsconductedbytheFrenchphysiologist,Brown-
Sequard。Buttheexplanationofhisresultsis,inmyopinion,opentodiscussion。Inthesecaseswehavetodowiththeapparenttransmissionofartificiallyproducedmalformations……Alltheseeffectsweresaidtobetransmittedtodescendantsasfarasthefifthorsixthgeneration。
\"Butwemustinquirewhetherthesecasesarereallyduetoheredity,andnottosimpleinfection。Inthecaseofepilepsy,atanyrate,itiseasytoimaginethatthepassageofsomespecificorganismthroughthereproductivecellsmaytakeplace,asinthecaseofsyphilis。Weare,however,entirelyignorantofthenatureoftheformerdisease。Thissuggestedexplanationmaynotperhapsapplytotheothercases;butwemustrememberthatanimalswhichhavebeensubjectedtosuchsevereoperationsuponthenervoussystemhavesustainedagreatshock,andiftheyarecapableofbreeding,itisonlyprobablethattheywillproduceweakdescendants,andsuchasareeasilyaffectedbydisease。Sucharesultdoesnot,however,explainwhytheoffspringshouldsufferfromthesamediseaseasthatwhichwasartificiallyinducedintheparents。Butthisdoesnotappeartohavebeenbyanymeansinvariablythecase。Brown-
Sequardhimselfsays:’Thechangesintheeyeoftheoffspringwereofaveryvariablenature,andwereonlyoccasionallyexactlysimilartothoseobservedintheparents。’
\"Thereisnodoubt,however,thattheseexperimentsdemandcarefulconsideration,butbeforetheycanclaimscientificrecognition,theymustbesubjectedtorigidcriticismastotheprecautionstaken,thenatureandnumberofthecontrolexperiments,&c。
\"Uptothepresenttimesuchnecessaryconditionshavenotbeensufficientlyobserved。Therecentexperimentsthemselvesareonlydescribedinshortpreliminarynotices,which,asregardstheiraccuracy,thepossibilityofmistake,theprecautionstaken,andtheexactsuccessionofindividualsaffected,affordnodataonwhichascientificopinioncanbefounded\"(pp。81,82)。
ThelineProfessorWeismanntakes,therefore,istodiscreditthefacts;yetonalaterpagewefindthattheexperimentshavesincebeenrepeatedbyObersteiner,\"whohasdescribedtheminaveryexactandunprejudicedmanner,\"andthat\"thefact\"——(IimaginethatProfessorWeismannintends\"thefacts\")——\"cannotbedoubted。\"
Onastilllaterpage,however,weread:-
\"If,forinstance,itcouldbeshownthatartificialmutilationspontaneouslyreappearsintheoffspringwithsufficientfrequencytoexcludeallpossibilitiesofchance,thensuchproof[i。e。,thatacquiredcharacterscanbetransmitted]wouldbeforthcoming。Thetransmissionofmutilationshasbeenfrequentlyasserted,andhasbeenevenrecentlyagainbroughtforward,butallthesupposedinstanceshavebrokendownwhencarefullyexamined\"(p。390)。
Here,then,wearetoldthatproofoftheoccasionaltransmissionofmutilationswouldbesufficienttoestablishthefact,butonp。267
wefindthatnosinglefactisknownwhichreallyprovesthatacquiredcharacterscanbetransmitted,\"FORTHEASCERTAINEDFACTS
WHICHSEEMTOPOINTTOTHETRANSMISSIONOFARTIFICIALLYPRODUCED
DISEASESCANNOTBECONSIDEREDASPROOF\"[Italicsmine。]Perhaps;
butitwasmutilationinmanycasesthatProfessorWeismannpracticallyadmittedtohavebeentransmittedwhenhedeclaredthatObersteinerhadverifiedBrown-Sequard’sexperiments。
ThatProfessorWeismannrecognisesthevitalimportancetohisowntheoryofthequestionwhetherornomutilationscanbetransmittedunderanycircumstances,isevidentfromapassageonp。425ofhiswork,onwhichhesays:\"Itcanhardlybedoubtedthatmutilationsareacquiredcharacters;theydonotarisefromanytendencycontainedinthegerm,butaremerelythereactionofthebodyundercertainexternalinfluences。Theyare,asIhaverecentlyexpressedit,purelysomatogeniccharacters——viz。,characterswhichemanatefromthebody(soma)only,asopposedtothegerm-cells;theyare,therefore,charactersthatdonotarisefromthegermitself。
\"Ifmutilationsmustnecessarilybetransmitted\"[whichnoonethatIknowofhasmaintained],\"oreveniftheymightoccasionallybetransmitted\"[whichcannot,Iimagine,bereasonablyquestioned],\"apowerfulsupportwouldbegiventotheLamarckianprinciple,andthetransmissionoffunctionalhypertrophyoratrophywouldthusbecomehighlyprobable。\"
IhavenotfoundanyfurtherattemptinProfessorWeismann’sbooktodealwiththeevidenceadducedbyMr。Darwintoshowthatmutilations,iffollowedbydiseases,aresometimesinherited;andI
mustleaveittothereadertodeterminehowfarProfessorWeismannhasshownreasonforrejectingMr。Darwin’sconclusion。Idonot,however,dwelluponthesefactsnowasevidenceofatransmittedchangeofbodilyform,orofinstinctduetouseanddisuseorhabit;whattheyproveisthatthegerm-cellswithintheparent’sbodydonotstandapartfromtheothercellsofthebodysocompletelyasProfessorWeismannwouldhaveusbelieve,butthat,asProfessorHering,ofPrague,hasaptlysaid,theyechowithmoreorlessfrequencyandforcetotheprofounderimpressionsmadeuponothercells。
ImaysaythatProfessorWeismanndoesnotmorecavalierlywaveasidethemassofevidencecollectedbyMr。Darwinandahostofotherwriters,totheeffectthatmutilationsaresometimesinherited,thandoesMr。Wallace,whosaysthat,\"asregardsmutilations,itisgenerallyadmittedthattheyarenotinherited,andthereisampleevidenceonthispoint。\"Itisindeedgenerallyadmittedthatmutilations,whennotfollowedbydisease,areveryrarely,ifever,inherited;andMr。Wallace’sappealtothe\"ampleevidence\"whichheallegestoexistonthishead,ismuchasthoughheshouldsaythatthereisampleevidencetoshowthatthedaysarelongerinsummerthaninwinter。\"Nevertheless,\"hecontinues,\"afewcasesofapparentinheritanceofmutilationshavebeenrecorded,andthese,iftrustworthy,aredifficultiesinthewayofthetheory。\"……\"Theoften-quotedcaseofadiseaseinducedbymutilationbeinginherited(Brown-Sequard’sepilepticguinea-pigs)
hasbeendiscussedbyProfessorWeismannandshowntobenotconclusive。Themutilationitself——asectionofcertainnerves——wasneverinherited,buttheresultingepilepsy,orageneralstateofweakness,deformity,orsores,wassometimesinherited。Itis,however,possiblethatthemereinjuryintroducedandencouragedthegrowthofcertainmicrobes,which,spreadingthroughtheorganism,sometimesreachedthegerm-cells,andthustransmittedadiseasedconditiontotheoffspring。\"{35}
Isupposeamicrobewhichmadeguinea-pigseattheirtoesoffwascommunicatedtothegerm-cellsofanunfortunateguinea-pigwhichhadbeenalreadymicrobedbyit,andmadetheoffspringbiteitstoesofftoo。Themicrobehasagooddealtoanswerfor。
OnthecaseofthedeteriorationofhorsesintheFalklandIslandsafterafewgenerations,ProfessorWeismannsays:-
\"Insuchacasewehaveonlytoassumethattheclimatewhichisunfavourable,andthenutrimentwhichisinsufficientforhorses,affectnotonlytheanimalasawholebutalsoitsgerm-cells。Thiswouldresultinthediminutioninsizeofthegerm-cells,theeffectsupontheoffspringbeingstillfurtherintensifiedbytheinsufficientnourishmentsuppliedduringgrowth。Butsuchresultswouldnotdependuponthetransmissionbythegerm-cellsofcertainpeculiaritiesduetotheunfavourableclimate,whichonlyappearinthefull-grownhorse。\"
ButProfessorWeismanndoesnotlikesuchcases,andadmitsthathecannotexplainthefactsinconnectionwiththeclimaticvarietiesofcertainbutterflies,except\"bysupposingthepassiveacquisitionofcharactersproducedbythedirectinfluenceofclimate。\"
Neverthelessinhisnextparagraphbutonehecallssuchcases\"doubtful,\"andproposesthatforthemomenttheyshouldbeleftaside。Heaccordinglyleavesthem,butIhavenotyetfoundwhatothermomentheconsideredauspiciousforreturningtothem。Hetellsusthat\"newexperimentswillbenecessary,andthathehashimselfalreadybeguntoundertakethem。\"Perhapshewillgiveustheresultsoftheseexperimentsinsomefuturebook——forthattheywillprovesatisfactorytohimcanhardly,Ithink,bedoubted。Hewrites:-
\"Leavingononeside,forthemoment,thesedoubtfulandinsufficientlyinvestigatedcases,wemaystillmaintainthattheassumptionthatchangesinducedbyexternalconditionsintheorganismasawholearecommunicatedtothegerm-cellsafterthemannerindicatedinDarwin’shypothesisofpangenesis,iswhollyunnecessaryfortheexplanationofthesephenomena。Stillwecannotexcludethepossibilityofsuchatransmissionoccasionallyoccurring,forevenifthegreaterpartoftheeffectsmustbeattributabletonaturalselection,theremightbeasmallerpartincertaincaseswhichdependsonthisexceptionalfactor。\"
IrepeatedlytriedtounderstandMr。Darwin’stheoryofpangenesis,andsooftenfailedthatIlongsincegavethematterupindespair。
IdidsowiththelessunwillingnessbecauseIsawthatnooneelseappearedtounderstandthetheory,andthatevenMr。Darwin’swarmestadherentsregardeditwithdisfavour。IfMr。Darwinmeansthateverycellofthebodythrowsoffminuteparticlesthatfindtheirwaytothegerm-cells,andhenceintothenewembryo,thisisindeeddifficultofcomprehensionandbelief。Ifhemeansthattherhythmsorvibrationsthatgoonceaselesslyineverycellofthebodycommunicatethemselveswithgreaterorlessaccuracyorperturbation,asthecasemaybe,tothecellsthatgotoformoffspring,andthatsincethecharacteristicsofmatteraredeterminedbyvibrations,incommunicatingvibrationstheyineffectcommunicatematter,accordingtotheviewputforwardinthelastchapterofmybook\"LuckorCunning,\"{36}thenwecanbetterunderstandit。Ihavenothing,however,todowithMr。Darwin’stheoryofpangenesisbeyondavoidingthepretencethatIunderstandeitherthetheoryitselforwhatProfessorWeismannsaysaboutit;
allIamconcernedwithisProfessorWeismann’sadmission,madeimmediatelyafterwards,thatthesomaticcellsmay,andperhapssometimesdo,impartcharacteristicstothegerm-cells。
\"Acompleteandsatisfactoryrefutationofsuchanopinion,\"hecontinues,\"cannotbebroughtforwardatpresent\";soIsupposewemustwaitalittlelonger,butinthemeantimewemayagainremarkthat,ifweadmitevenoccasionalcommunicationofchangesinthesomaticcellstothegerm-cells,wehaveletinthethinendofthewedge,asMr。Darwindidwhenhesaidthatuseanddisusedidagooddealtowardsmodification。Buffon,inhisfirstvolumeontheloweranimals,{37}dwellsontheimpossibilityofstoppingthebreachoncemadebyadmissionofvariationatall。\"Ifthepoint,\"hewrites,\"wereoncegained,thatamonganimalsandvegetablestherehadbeen,Idonotsayseveralspecies,butevenasingleone,whichhadbeenproducedinthecourseofdirectdescentfromanotherspecies;if,forexample,itcouldbeonceshownthattheasswasbutadegenerationfromthehorse——thenthereisnofartherlimittobesettothepowerofNature,andweshouldnotbewronginsupposingthatwithsufficienttimeshecouldhaveevolvedallotherorganisedformsfromoneprimordialtype。\"Sowithuseanddisuseandtransmissionofacquiredcharacteristicsgenerally——onceshowthatasinglestructureorinstinctisduetohabitinprecedinggenerations,andwecanimposenolimitontheresultsachievablebyaccumulationinthisrespect,norshallwebewronginconceivingitaspossiblethatallspecialisation,whetherofstructureorinstinct,maybedueultimatelytohabit。
Howfarthiscanbeshowntobeprobableis,ofcourse,anothermatter,butIamnotimmediatelyconcernedwiththis;allIamconcernedwithnowistoshowthatthegerm-cellsnotunfrequentlybecomepermanentlyaffectedbyeventsthathavemadeaprofoundimpressionuponthesomaticcells,insofarthattheytransmitanobviousreminiscenceoftheimpressiontotheembryoswhichtheygosubsequentlytowardsforming。Thisisallthatisnecessaryformycase,andIdonotfindthatProfessorWeismann,afterall,disputesit。
Buthere,again,comesthedifficultyofsayingwhatProfessorWeismanndoes,andwhathedoesnot,dispute。OnemomenthegivesallthatiswantedfortheLamarckiancontention,thenexthedeniescommon-sensethebarenecessariesoflife。ForamoreexhaustiveanddetailedcriticismofProfessorWeismann’sposition,IwouldreferthereadertoanadmirablycleararticlebyMr。SidneyH。
Vines,whichappearedinNature,October24,1889。IcanonlysaythatwhilereadingProfessorWeismann’sbook,IfeelasIdowhenI
readthoseofMr。Darwin,andofagoodmanyotherwritersonbiologywhomIneednotname。Ibecomelikeaflyinawindow-pane。
Iseethesunshineandfreedombeyond,andbuzzupanddowntheirpages,everhopefultogetthroughthemtothefreshairwithout,buteverkeptbackbyamysterioussomething,whichIfeelbutcannoteithergrasporsee。ItwasnotthuswhenIreadBuffon,ErasmusDarwin,andLamarck;itisnotthuswhenIreadsucharticlesasMr。Vines’sjustreferredto。Loveofself-display,andthewantofsinglenessofmindthatitinevitablyengenders——these,Isuppose,arethesinsthatglazethecasementsofmostmen’sminds;andfromthese,nomatterhowhardhetriestofreehimself,norhowmuchhedespisesthem,whoisaltogetherexempt?
Finally,then,whenweconsidertheimmensemassofevidencereferredtobriefly,butsufficiently,byMr。CharlesDarwin,andreferredtowithoutother,forthemostpart,thanoff-handdismissalbyProfessorWeismanninthelastoftheessaysthathavebeenrecentlytranslated,Idonotseehowanyonewhobringsanunbiasedmindtothequestioncanhesitateastothesideonwhichtheweightoftestimonyinclines。ProfessorWeismanndeclaresthat\"thetransmissionofmutilationsmaybedismissedintothedomainoffable。\"{38}Ifso,then,whomcanwetrust?WhatistheuseofscienceatalliftheconclusionsofamanascompetentasIreadilyadmitMr。Darwintohavebeen,ontheevidencelaidbeforehimfromcountlesssources,istobesetasidelightlyandwithoutgivingtheclearestandmostcogentexplanationofthewhyandwherefore?Whenweseeaperson\"ostrichising\"theevidencewhichhehastomeet,asclearlyasIbelieveProfessorWeismanntobedoing,weshallinninecasesoutoftenberightinsupposingthatheknowstheevidencetobetoostrongforhim。
THEDEADLOCKINDARWINISM——PARTIII
Nowletmereturntotherecentdivisionofbiologicalopinionintotwomainstreams——LamarckismandWeismannismBothLamarckiansandWeismannists,nottomentionmankindingeneral,admitthatthebetteradaptedtoitssurroundingsalivingformmaybe,themorelikelyitistooutbreeditscompeers。Theworldatlarge,again,needsnottobetoldthatthenormalcourseisnotunfrequentlydeflectedthroughthefortunesofwar;nevertheless,accordingtoLamarckiansandErasmus-Darwinians,habitualeffort,guidedbyever-
growingintelligence——thatistosay,bycontinuedincreaseofpowerinthematterofknowingourlikesanddislikes——hasbeensomuchthemainfactorthroughoutthecourseoforganicdevelopment,thattherest,thoughnotlostsightof,maybeallowedtogowithoutsaying。According,ontheotherhand,toextremeCharles-DarwiniansandWeismannists,habit,effortandintelligenceacquiredduringtheexperienceofanyonelifegoesfornothing。Notevenalittlefractionofitendurestothebenefitofoffspring。Itdieswithhiminwhomitisacquired,andtheheirsofaman’sbodytakenointeresttherein。Tostatethisdoctrineistoarouseinstinctiveloathing;itismyfortunatetasktomaintainthatsuchanightmareofwasteanddeathisasbaselessasitisrepulsive。
ThesplitinbiologicalopinionoccasionedbythedeadlocktowhichCharles-Darwinismhasbeenreduced,thoughcomparativelyrecent,widensrapidly。TenyearsagoLamarck’snamewasmentionedonlyasabywordforextravagance;now,wecannottakeupanumberofNaturewithoutseeinghowhotthecontentionisbetweenhisfollowersandthoseofWeismann。Thismustbereferred,asIimpliedearlier,togrowingperceptionthatMr。DarwinshouldeitherhavegonefarthertowardsLamarckismornotsofar。Inadmittinguseanddisuseasfreelyashedid,hegaveLamarckiansleveragefortheoverthrowofasystembasedostensiblyontheaccumulationoffortunateaccidents。Inassigningthelion’sshareofdevelopmenttotheaccumulationoffortunateaccidents,hetemptedfortuitiststotrytocutthegroundfromunderLamarck’sfeetbydenyingthattheeffectsofuseanddisusecanbeinheritedatall。WhenthepublichadoncegottounderstandwhatLamarckhadintended,andwhereinMr。CharlesDarwinhaddifferedfromhim,itbecameimpossibleforCharles-Darwinianstoremainwheretheywere,norisiteasytoseewhatcoursewasopentothemexcepttocastaboutforatheorybywhichtheycouldgetridofuseanddisusealtogether。Weismannism,therefore,istheinevitableoutcomeofthestraitstowhichCharles-Darwinianswerereducedthroughthewayinwhichtheirleaderhadhaltedbetweentwoopinions。
ThisiswhyCharles-Darwinians,fromProfessorHuxleydownwards,havekeptthedifferencebetweenLamarck’sopinionsandthoseofMr。
Darwinsomuchinthebackground。UnwillingnesstomakethisunderstoodisnowheremanifestedmoreclearlythaninDr。FrancisDarwin’slifeofhisfather。InthisworkLamarckissneeredatonceortwice,andtoldtogoaway,butthereisnoattempttostatethetwocasessidebyside;fromwhich,asfromnotalittleelse,I
concludethatDr。FrancisDarwinhasdescendedfromhisfatherwithsingularlylittlemodification。
Proceedingtotheevidenceforthetransmissionsofacquiredhabits,Iwillquotetworecentlyadducedexamplesfromamongthemanythathavebeencrediblyattested。ThefirstwascontributedtoNature(March14,1889)byProfessorMarcusM。Hartog,whowrote:-
\"A。B。ismoderatelymyopicandveryastigmaticinthelefteye;
extremelymyopicintheright。Asthelefteyegavesuchbadimagesfornearobjects,hewascompelledinchildhoodtomaskit,andacquiredthehabitofleaninghisheadonhisleftarmforwriting,soastoblindthateye,orofrestingthelefttempleandeyeonthehand,withtheelbowonthetable。Attheageoffifteentheeyeswereequalisedbytheuseofsuitablespectacles,andhesoonlostthehabitcompletelyandpermanently。Heisnowthefatheroftwochildren,aboyandagirl,whosevision(testedrepeatedlyandfully)isemmetropicinbotheyes,sothattheyhavenotinheritedthecongenitalopticaldefectoftheirfather。Allthesame,theyhavebothoftheminheritedhisearlyacquiredhabit,andneedconstantwatchfulnesstopreventtheirhidingthelefteyewhenwriting,byrestingtheheadontheleftforearmorhand。Imitationisherequiteoutofthequestion。
\"Consideringthateveryhabitinvolveschangesintheproportionaldevelopmentofthemuscularandosseoussystems,andhenceprobablyofthenervoussystemalso,theimportanceofinheritedhabits,naturaloracquired,cannotbeoverlookedinthegeneraltheoryofinheritance。IamfullyawarethatIshallbeaccusedofflatLamarckism,butanicknameisnotanargument。\"
TothisProfessorRayLankesterrejoined(Nature,March21,1889):-
\"Itisnotunusualforchildrentoresttheheadontheleftforearmorhandwhenwriting,andIdoubtwhethermuchvaluecanbeattachedtothecasedescribedbyProfessorHartog。Thekindofobservationwhichhislettersuggestsis,however,likelytoleadtoresultseitherfororagainstthetransmissionofacquiredcharacters。Anoldfriendofminelosthisrightarmwhenaschoolboy,andhaseversincewrittenwithhisleft。Hehasalargefamilyandgrandchildren,butIhavenotheardofanyofthemshowingadispositiontoleft-handedness。\"
FromNature(March21,1889)ItakethesecondinstancecommunicatedbyMr。J。Jenner-Weir,whowroteasfollows:-
\"Mr。MarcusM。Hartog’sletterofMarch6th,insertedinlastweek’snumber(p。462),isaveryvaluablecontributiontothegrowingevidencethatacquiredcharactersmaybeinherited。Ihavelongheldtheviewthatsuchisoftenthecase,andIhavemyselfobservedseveralinstancesofthe,atleastImaysay,apparentfact。
\"ManyyearsagotherewasaveryfinemaleoftheCapramegacerosinthegardensoftheZoologicalSociety。Torestrainthisanimalfromjumpingoverthefenceoftheenclosureinwhichhewasconfined,along,andheavychainwasattachedtothecollarroundhisneck。Hewasconstantlyinthehabitoftakingthischainupbyhishornsandmovingitfromonesidetoanotheroverhisback;indoingthishethrewhisheadverymuchback,hishornsbeingplacedinalinewiththeback。Thehabithadbecomequitechronicwithhim,andwasverytiresometolookat。Iwasverymuchastonishedtoobservethathisoffspringinheritedthehabit,andalthoughitwasnotnecessarytoattachachaintotheirnecks,Ihaveoftenseenayoungmalethrowinghishornsoverhisbackandshiftingfromsidetosideanimaginarychain。Theactionwasexactlythesameasthatofhisancestor。ThecaseofthekidofthisgoatappearstometobeparalleltothatofchildandparentgivenbyMr。Hartog。IthinkatthetimeImadethisobservationIinformedMr。Darwinofthefactbyletter,andhedidnotaccusemeof’flatLamarckism。’\"
Tothislettertherewasnorejoinder。Itmaybesaid,ofcourse,thattheactionoftheoffspringineachofthesecaseswasduetoaccidentalcoincidenceonly。Anythingcanbesaid,butthequestionturnsnotonwhatanadvocatecansay,butonwhatareasonablyintelligentanddisinterestedjurywillbelieve;grantedtheymightbemistakeninacceptingtheforegoingstories,buttheworldofscience,likethatofcommerce,isbasedonthefaithorconfidence,whichbothcreatesandsustainsthem。Indeedtheuniverseitselfisbutthecreatureoffaith,forassuredlyweknowofnootherfoundation。Thereisnothingsogenerallyandreasonablyaccepted——
notevenourowncontinuedidentity——butquestionsmayberaisedaboutitthatwillshortlyproveunanswerable。Wecannotsotesteverysixpencegivenusinchangeastobesurethatwenevertakeabadone,andhadbettersometimesbecheatedthanreducecautiontoanabsurdity。Moreover,wehaveseenfromtheevidencegiveninmyprecedingarticlethatthegerm-cellsissuingfromaparent’sbodycan,anddo,respondtoprofoundimpressionsmadeonthesomatic-
cells。Thisbeingso,whatimpressionsaremoreprofound,whatneedsengagemoreassiduousattentionthanthoseconnectedwithself-protection,theprocuringoffood,andthecontinuationofthespecies?Ifthemereanxietyconnectedwithanill-healingwoundinflictedonbutonegenerationissometimesfoundtohavesoimpressedthegerm-cellsthattheyhanddownitsscarstooffspring,howmuchmoreshallnotanxietiesthathavedirectedactionofallkindsfrombirthtilldeath,notinonegenerationonlybutinalongerseriesofgenerationsthanthemindcanrealisetoitself,modify,andindeedcontrol,theorganisationofeveryspecies?
IseeProfessorS。H。Vines,inthearticleonWeismann’stheoryreferredtoinmyprecedingarticle,saysMr。Darwin\"heldthatitwasnotthesuddenvariationsduetoalteredexternalconditionswhichbecomepermanent,butthoseslowlyproducedbywhathetermed’theaccumulativeactionofchangedconditionsoflife。’\"NothingcanbemoresoundlyLamarckian,andnothingshouldmoreconclusivelyshowthat,whateverelseMr。Darwinwas,hewasnotaCharles-