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Lectures on Evolution

Thomas Henry Huxley

The Project Gutenberg Etext of Lectures on Evolution, by HuxleyThis is Essay #3 from "cience an! Hebre Tra!ition"

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Title4 Lectures on Evolution

Title4 This is Essay #3 from "cience an! Hebre Tra!ition"

5uthor4 Thomas Henry Huxley

6ay, 7881 9Etext #7:72;

The Project Gutenberg Etext of Lectures on Evolution, by Huxley

orrecte! E)+T+<= of our etexts get a ne =>60E/, 3saht11'txt.E/+<= base! on se$arate sources get ne LETTE/, 3saht18a'txt

Processe! by )'/' Thom$son ?!rthom@ihug'co'nAB

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Processe! by )'/' Thom$son ?!rthom@ihug'co'nAB

Lectures on EvolutionThis is Essay #3 from "cience an! Hebre Tra!ition"by Thomas Henry Huxley

+THE TH/EE HP<THEE /EPET+=G THE H+T</ <- =5T>/E

(e live in an! form $art of a system of things of immense!iversity an! $er$lexity, hich e call =atureM an! it is amatter of the !ee$est interest to all of us that e shoul! form just conce$tions of the constitution of that system an! of its$ast history' (ith relation to this universe, man is, in extent,little more than a mathematical $ointM in !uration but afleeting sha!oM he is a mere ree! sha%en in the in!s of force'0ut as Pascal long ago remar%e!, although a mere ree!, he is athin%ing ree!M an! in virtue of that on!erful ca$acity of thought, he has the $oer of framing for himself a symbolicconce$tion of the universe, hich, although !oubtless highly

im$erfect an! ina!euate as a $icture of the great hole, is yetsufficient to serve him as a chart for the gui!ance of his$ractical affairs' +t has ta%en long ages of toilsome an! oftenfruitless labour to enable man to loo% stea!ily at the shiftingscenes of the $hantasmagoria of =ature, to notice hat is fixe!among her fluctuations, an! hat is regular among her a$$arentirregularitiesM an! it is only com$aratively lately, ithin thelast fe centuries, that the conce$tion of a universal or!er an!of a !efinite course of things, hich e term the course of =ature, has emerge!'

0ut, once originate!, the conce$tion of the constancy of the

or!er of =ature has become the !ominant i!ea of mo!ern thought'To any $erson ho is familiar ith the facts u$on hich thatconce$tion is base!, an! is com$etent to estimate their significance, it has cease! to be conceivable that chance shoul!have any $lace in the universe, or that events shoul! !e$en!u$on any but the natural seuence of cause an! effect' (e havecome to loo% u$on the $resent as the chil! of the $ast an! asthe $arent of the futureM an!, as e have exclu!e! chance from a$lace in the universe, so e ignore, even as a $ossibility, thenotion of any interference ith the or!er of =ature'(hatever may be mens s$eculative !octrines, it is uite certainthat every intelligent $erson gui!es his life an! ris%s his

fortune u$on the belief that the or!erof =ature is constant, an!that the chain of natural causation is never bro%en'

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+n fact, no belief hich e entertain has so com$lete a logicalbasis as that to hich + have just referre!' +t tacitlyun!erlies every $rocess of reasoningM it is the foun!ation of every act of the ill' +t is base! u$on the broa!est in!uction,an! it is verifie! by the most constant, regular, an! universalof !e!uctive $rocesses' 0ut e must recollect that any humanbelief, hoever broa! its basis, hoever !efensible it may seem,

is, after all, only a $robable belief, an! that our i!est an!safest generalisations are sim$ly statements of the highest!egree of $robability' Though e are uite clear about theconstancy of the or!er of =ature, at the $resent time, an! inthe $resent state of things, it by no means necessarily follosthat e are justifie! in ex$an!ing this generalisation into theinfinite $ast, an! in !enying, absolutely, that there may havebeen a time hen =ature !i! not follo a fixe! or!er, hen therelations of cause an! effect ere not !efinite, an! hen extraFnatural agencies interfere! ith the general course of =ature'autious men ill allo that a universe so !ifferent from thathich e %no may have existe!M just as a very can!i! thin%er

may a!mit that a orl! in hich to an! to !o not ma%e four,an! in hich to straight lines !o inclose a s$ace, may exist'0ut the same caution hich forces the a!mission of such$ossibilities !eman!s a great !eal of evi!ence before itrecognises them to be anything more substantial' 5n! hen it isasserte! that, so many thousan! years ago, events occurre! in amanner utterly foreign to an! inconsistent ith the existinglas of =ature, men, ho ithout being $articularly cautious,are sim$ly honest thin%ers, unilling to !eceive themselves or !elu!e others, as% for trustorthy evi!ence of the fact'

)i! things so ha$$en or !i! they notR This is a historical

uestion, an! one the anser to hich must be sought in the sameay as the solution of any other historical $roblem'

o far as + %no, there are only three hy$otheses hich ever have been entertaine!, or hich ell can be entertaine!,res$ecting the $ast history of =ature' + ill, in the first$lace, state the hy$otheses, an! then + ill consi!er hatevi!ence bearing u$on them is in our $ossession, an! by hatlight of criticism that evi!ence is to be inter$rete!'

>$on the first hy$othesis, the assum$tion is, that $henomena of =ature similar to those exhibite! by the $resent orl! have

alays existe!M in other or!s, that the universe has existe!,from all eternity, in hat may be broa!ly terme! its$resent con!ition'

The secon! hy$othesis is that the $resent state of things hasha! only a limite! !urationM an! that, at some $erio! in the$ast, a con!ition of the orl!, essentially similar to thathich e no %no, came into existence, ithout any $rece!entcon!ition from hich it coul! have naturally $rocee!e!'The assum$tion that successive states of =ature have arisen,each ithout any relation of natural causation to an antece!entstate, is a mere mo!ification of this secon! hy$othesis'

The thir! hy$othesis also assumes that the $resent state of things has ha! but a limite! !urationM but it su$$oses that this

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state has been evolve! by a natural $rocess from an antece!entstate, an! that from another, an! so onM an!, on thishy$othesis, the attem$t to assign any limit to the series of $ast changes is, usually, given u$'

+t is so nee!ful to form clear an! !istinct notions of hat isreally meant by each of these hy$otheses that + ill as% you to

imagine hat, accor!ing to each, oul! have been visible to as$ectator of the events hich constitute the history of theearth' <n the first hy$othesis, hoever far bac% in time thats$ectator might be $lace!, he oul! see a orl! essentially,though $erha$s not in all its !etails, similar to that hich noexists' The animals hich existe! oul! be the ancestors of those hich no live, an! similar to themM the $lants, in li%emanner, oul! be such as e %noM an! the mountains, $lains, an!aters oul! foresha!o the salient features of our $resent lan!an! ater' This vie as hel! more or less !istinctly, sometimescombine! ith the notion of recurrent cycles of change, inancient timesM an! its influence has been felt !on to the

$resent !ay' +t is orthy of remar% that it is a hy$othesishich is not inconsistent ith the !octrine of >niformitarianism, ith hich geologists are familiar'That !octrine as hel! by Hutton, an! in his earlier !ays byLyell' Hutton as struc% by the !emonstration of astronomersthat the $erturbations of the $lanetary bo!ies, hoever greatthey may be, yet sooner or later right themselvesM an! that thesolar system $ossesses a selfFa!justing $oer by hich theseaberrations are all brought bac% to a mean con!ition'Hutton imagine! that the li%e might be true of terrestrialchangesM although no one recognise! more clearly than he thefact that the !ry lan! is being constantly ashe! !on by rain

an! rivers an! !e$osite! in the seaM an! that thus, in a longer or shorter time, the ineualities of the earths surface must belevelle!, an! its high lan!s brought !on to the ocean'0ut, ta%ing into account the internal forces of the earth,hich, u$heaving the seaFbottom give rise to ne lan!, hethought that these o$erations of !egra!ation an! elevation mightcom$ensate each otherM an! that thus, for any assignable time,the general features of our $lanet might remain hat they are' 5n! inasmuch as, un!er these circumstances, there nee! be nolimit to the $ro$agation of animals an! $lants, it is clear thatthe consistent or%ing out of the uniformitarian i!ea might lea!to the conce$tion of the eternity of the orl!' =ot that + mean

to say that either Hutton or Lyell hel! this conce$tionFFassure!ly notM they oul! have been the first to re$u!iate it'=evertheless, the logical !evelo$ment of some of their argumentsten!s !irectly toar!s this hy$othesis'

The secon! hy$othesis su$$oses that the $resent or!er of things,at some no very remote time, ha! a su!!en origin, an! that theorl!, such as it no is, ha! chaos for its $henomenalantece!ent' That is the !octrine hich you ill fin! state! mostfully an! clearly in the immortal $oem of Sohn 6iltonFFtheEnglish ?iB)ivina omme!iaFF?NiB "Para!ise Lost'" + believe itis largely to the influence of that remar%able or%, combine!

ith the !aily teachings to hich e have all listene! in our chil!hoo!, that this hy$othesis oes its general i!e !iffusionas one of the current beliefs of EnglishFs$ea%ing $eo$le' +f you

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turn to the seventh boo% of "Para!ise Lost," you ill fin! therestate! the hy$othesis to hich + refer, hich is briefly this4That this visible universe of ours came into existence at nogreat !istance of time from the $resentM an! that the $arts of hich it is com$ose! ma!e their a$$earance, in a certain!efinite or!er, in the s$ace of six natural !ays, in such amanner that, on the first of these !ays, light a$$eare!M that,

on the secon!, the firmament, or s%y, se$arate! the atersabove, from the aters beneath the firmamentM that, on the thir!!ay, the aters !re aay from the !ry lan!, an! u$on it avarie! vegetable life, similar to that hich no exists, ma!eits a$$earanceM that the fourth !ay as signalise! by thea$$arition of the sun, the stars, the moon, an! the $lanetsMthat, on the fifth !ay, auatic animals originate! ithin theatersM that, on the sixth !ay, the earth gave rise to our fourFfoote! terrestrial creatures, an! to all varieties of terrestrial animals exce$t bir!s, hich ha! a$$eare! on the$rece!ing !ayM an!, finally, that man a$$eare! u$on the earth,an! the emergence of the universe from chaos as finishe!'

6ilton tells us, ithout the least ambiguity, hat a s$ectator of these marvellous occurrences oul! have itnesse!' + !oubtnot that his $oem is familiar to all of you, but + shoul! li%eto recall one $assage to your min!s, in or!er that + may be justifie! in hat + have sai! regar!ing the $erfectly concrete,!efinite, $icture of the origin of the animal orl! hich 6ilton!ras' He says4FF

"The sixth, an! of creation last, arose(ith evening har$ an! matin, hen Go! sai!,Let the earth bring forth soul living in her %in!,attle an! cree$ing things, an! beast of the earth'

Each in their %in!& The earth obeye!, an!, straight<$ening her fertile omb, teeme! at a birth+nnumerous living creatures, $erfect forms,Limbe! an! fullFgron' <ut of the groun! u$rose, 5s from his lair, the il! beast, here he ons+n forest il!, in thic%et, bra%e, or !enM 5mong the trees in $airs they rose, they al%e!MThe cattle in the fiel!s an! mea!os greenMThose rare an! solitaryM these in floc%sPasturing at once, an! in broa! her!s u$s$rung'The grassy clo!s no calve!M no half a$$earsThe tany lion, $aing to get free

His hin!er $artsFFthen s$rings, as bro%e from bon!s, 5n! ram$ant sha%es his brin!e! maneM the ounce,The libbar!, an! the tiger, as the mole/ising, the crumble! earth above them thre+n hilloc%sM the sift stag from un!ergroun!0ore u$ his branching hea!M scarce from his moul!0ehemoth, biggest born of earth, u$heave!His vastnessM fleece! the floc%s an! bleating rose 5s $lantsM ambiguous beteen sea an! lan!,The riverFhorse an! scaly croco!ile' 5t once came forth hatever cree$s the groun!,+nsect or orm'"

There is no !oubt as to the meaning of this statement, nor as tohat a man of 6iltons genius ex$ecte! oul! have been actually

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visible to an eyeFitness of this mo!e of origination of living things'

The thir! hy$othesis, or the hy$othesis of evolution, su$$osesthat, at any com$aratively late $erio! of $ast time, our imaginary s$ectator oul! meet ith a state of things verysimilar to that hich no obtainsM but that the li%eness of the

$ast to the $resent oul! gra!ually become less an! less, in$ro$ortion to the remoteness of his $erio! of observation fromthe $resent !ayM that the existing !istribution of mountains an!$lains, of rivers an! seas, oul! sho itself to be the $ro!uctof a slo $rocess of natural change o$erating u$on more an! morei!ely !ifferent antece!ent con!itions of the mineral frameFor%of the earthM until, at length, in $lace of that frameFor%, heoul! behol! only a vast nebulous mass, re$resenting theconstituents of the sun an! of the $lanetary bo!ies' Prece!ingthe forms of life hich no exist, our observer oul! seeanimals an! $lants, not i!entical ith them, but li%e them,increasing their !ifferences ith their antiuity an!, at the

same time, becoming sim$ler an! sim$lerM until, finally, theorl! of life oul! $resent nothing but that un!ifferentiate!$roto$lasmic matter hich, so far as our $resent %nole!ge goes,is the common foun!ation of all vital activity'

The hy$othesis of evolution su$$oses that in all this vast$rogression there oul! be no breach of continuity, no $oint athich e coul! say "This is a natural $rocess," an! "This is nota natural $rocessM" but that the hole might be com$are! to thaton!erful o$eration of !evelo$ment hich may be seen going onevery !ay un!er our eyes, in virtue of hich there arises, outof the semiFflui! com$aratively homogeneous substance hich e

call an egg, the com$licate! organisation of one of the higher animals' That, in a fe or!s, is hat is meant by thehy$othesis of evolution'

+ have alrea!y suggeste! that, in !ealing ith these threehy$otheses, in en!eavouring to form a ju!gment as to hich of them is the more orthy of belief, or hether none is orthy of beliefFFin hich case our con!ition of min! shoul! be thatsus$ension of ju!gment hich is so !ifficult to all but traine!intellectsFFe shoul! be in!ifferent to all ?iBa $riori?NiBconsi!erations' The uestion is a uestion of historical fact'The universe has come into existence someho or other, an! the

$roblem is, hether it came into existence in one fashion, or hether it came into existence in anotherM an!, as an essential$reliminary to further !iscussion, $ermit me to say to or threeor!s as to the nature an! the %in!s of historical evi!ence'

The evi!ence as to the occurrence of any event in $ast time maybe range! un!er to hea!s hich, for convenience sa%e, + ills$ea% of as testimonial evi!ence an! as circumstantial evi!ence'0y testimonial evi!ence + mean human testimonyM an! bycircumstantial evi!ence + mean evi!ence hich is not humantestimony' Let me illustrate by a familiar exam$le hat +un!erstan! by these to %in!s of evi!ence, an! hat is to be

sai! res$ecting their value'

u$$ose that a man tells you that he sa a $erson stri%e another

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an! %ill himM that is testimonial evi!ence of the fact of mur!er' 0ut it is $ossible to have circumstantial evi!ence of the fact of mur!erM that is to say, you may fin! a man !yingith a oun! u$on his hea! having exactly the form an! character of the oun! hich is ma!e by an axe, an!, ith !ue care inta%ing surroun!ing circumstances into account, you may conclu!eith the utmost certainty that the man has been mur!ere!M

that his !eath is the conseuence of a blo inflicte! by another man ith that im$lement' (e are very much in the habit of consi!ering circumstantial evi!ence as of less value thantestimonial evi!ence, an! it may be that, here thecircumstances are not $erfectly clear an! intelligible, it is a!angerous an! unsafe %in! of evi!enceM but it must not beforgotten that, in many cases, circumstantial is uite asconclusive as testimonial evi!ence, an! that, not unfreuently,it is a great !eal eightier than testimonial evi!ence'-or exam$le, ta%e the case to hich + referre! just no'The circumstantial evi!ence may be better an! more convincingthan the testimonial evi!enceM for it may be im$ossible, un!er

the con!itions that + have !efine!, to su$$ose that the man methis !eath from any cause but the violent blo of an axe iel!e!by another man' The circumstantial evi!ence in favour of amur!er having been committe!, in that case, is as com$lete an!as convincing as evi!ence can be' +t is evi!ence hich is o$ento no !oubt an! to no falsification' 0ut the testimony of aitness is o$en to multitu!inous !oubts' He may have beenmista%en' He may have been actuate! by malice' +t has constantlyha$$ene! that even an accurate man has !eclare! that a thing hasha$$ene! in this, that, or the other ay, hen a carefulanalysis of the circumstantial evi!ence has shon that it !i!not ha$$en in that ay, but in some other ay'

(e may no consi!er the evi!ence in favour of or against thethree hy$otheses' Let me first !irect your attention to hat isto be sai! about the hy$othesis of the eternity of the state of things in hich e no live' (hat ill first stri%e you is, thatit is a hy$othesis hich, hether true or false, is not ca$ableof verification by any evi!ence' -or, in or!er to obtain either circumstantial or testimonial evi!ence sufficient to $rove theeternity of !uration of the $resent state of nature, you musthave an eternity of itnesses or an infinity of circumstances,an! neither of these is attainable' +t is utterly im$ossiblethat such evi!ence shoul! be carrie! beyon! a certain $oint of

timeM an! all that coul! be sai!, at most, oul! be, that so far as the evi!ence coul! be trace!, there as nothing to contra!ictthe hy$othesis' 0ut hen you loo%, not to the testimonialevi!enceFFhich, consi!ering the relative insignificance of theantiuity of human recor!s, might not be goo! for much in thiscaseFFbut to the circumstantial evi!ence, then you fin! thatthis hy$othesis is absolutely incom$atible ith such evi!ence ase haveM hich is of so $lain an! so sim$le a character that itis im$ossible in any ay to esca$e from the conclusions hich itforces u$on us'

ou are, !oubtless, all aare that the outer substance of the

earth, hich alone is accessible to !irect observation, is notof a homogeneous character, but that it is ma!e u$ of a number of layers or strata, the titles of the $rinci$al grou$s of hich

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are $lace! u$on the accom$anying !iagram' Each of these grou$sre$resents a number of be!s of san!, of stone, of clay, of slate, an! of various other materials'

<n careful examination, it is foun! that the materials of hicheach of these layers of more or less har! roc% are com$ose! are,for the most $art, of the same nature as those hich are at

$resent being forme! un!er %non con!itions on the surface of the earth' -or exam$le, the chal%, hich constitutes a great$art of the retaceous formation in some $arts of the orl!, is$ractically i!entical in its $hysical an! chemical charactersith a substance hich is no being forme! at the bottom of the 5tlantic <cean, an! covers an enormous areaM other be!s of roc%are com$arable ith the san!s hich are being forme! u$on seaFshores, $ac%e! together, an! so on' Thus, omitting roc%s of igneous origin, it is !emonstrable that all these be!s of stone,of hich a total of not less than seventy thousan! feet is%non, have been forme! by natural agencies, either out of theaste an! ashing of the !ry lan!, or else by the accumulation

of the exuviae of $lants an! animals' 6any of these strata arefull of such exuviaeFFthe soFcalle! "fossils'" /emains of thousan!s of s$ecies of animals an! $lants, as $erfectlyrecognisable as those of existing forms of life hich you meetith in museums, or as the shells hich you $ic% u$ u$on theseaFbeach, have been imbe!!e! in the ancient san!s, or mu!s, or limestones, just as they are being imbe!!e! no, in san!y, or clayey, or calcareous subaueous !e$osits' They furnish us itha recor!, the general nature of hich cannot be misinter$rete!,of the %in!s of things that have live! u$on the surface of theearth !uring the time that is registere! by this great thic%nessof stratifie! roc%s' 0ut even a su$erficial stu!y of these

fossils shos us that the animals an! $lants hich live at the$resent time have ha! only a tem$orary !urationM for the remainsof such mo!ern forms of life are met ith, for the most $art,only in the u$$ermost or latest tertiaries, an! their number ra$i!ly !iminishes in the loer !e$osits of that e$och' +n theol!er tertiaries, the $laces of existing animals an! $lants areta%en by other forms, as numerous an! !iversifie! as those hichlive no in the same localities, but more or less !ifferent fromthemM in the mesoAoic roc%s, these are re$lace! by others yetmore !ivergent from mo!ern ty$esM an!, in the $aleoAoicformations, the contrast is still more mar%e!' Thus thecircumstantial evi!ence absolutely negatives the conce$tion of

the eternity of the $resent con!ition of things' (e can say,ith certainty, that the $resent con!ition of things has existe!for a com$aratively short $erio!M an! that, so far as animal an!vegetable nature are concerne!, it has been $rece!e! by a!ifferent con!ition' (e can $ursue this evi!ence until e reachthe loest of the stratifie! roc%s, in hich e lose thein!ications of life altogether' The hy$othesis of the eternityof the $resent state of nature may therefore be $ut outof court'

-ig' 1'FF+!eal ection of the rust of the Earth'

(e no come to hat + ill term 6iltons hy$othesisFFthe

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hy$othesis that the $resent con!ition of things has en!ure! for a com$aratively short timeM an!, at the commencement of thattime, came into existence ithin the course of six !ays' + !oubtnot that it may have excite! some sur$rise in your min!s that +shoul! have s$o%en of this as 6iltons hy$othesis, rather thanthat + shoul! have chosen the terms hich are more customary,such as "the !octrine of creation," or "the 0iblical !octrine,"

or "the !octrine of 6oses," all of hich !enominations, asa$$lie! to the hy$othesis to hich + have just referre!, arecertainly much more familiar to you than the title of the6iltonic hy$othesis' 0ut + have ha! hat + cannot but thin% arevery eighty reasons for ta%ing the course hich + have $ursue!'+n the first $lace, + have !iscar!e! the title of the "!octrineof creation," because my $resent business is not ith theuestion hy the objects hich constitute =ature came intoexistence, but hen they came into existence, an! in hat or!er'This is as strictly a historical uestion as the uestion henthe 5ngles an! the Sutes inva!e! Englan!, an! hether they$rece!e! or folloe! the /omans' 0ut the uestion about creation

is a $hiloso$hical $roblem, an! one hich cannot be solve!, or even a$$roache!, by the historical metho!' (hat e ant to learnis, hether the facts, so far as they are %non, affor! evi!encethat things arose in the ay !escribe! by 6ilton, or hether they !o notM an!, hen that uestion is settle! it ill be timeenough to inuire into the causes of their origination'

+n the secon! $lace, + have not s$o%en of this !octrine as the0iblical !octrine' +t is uite true that $ersons as !iverse intheir general vies as 6ilton the Protestant an! the celebrate!Sesuit -ather uareA, each $ut u$on the first cha$ter of Genesisthe inter$retation embo!ie! in 6iltons $oem' +t is uite true

that this inter$retation is that hich has been instille! intoevery one of us in our chil!hoo!M but + !o not for one momentventure to say that it can $ro$erly be calle! the 0iblical!octrine' +t is not my business, an! !oes not lie ithin mycom$etency, to say hat the Hebre text !oes, an! hat it !oesnot signifyM moreover, ere + to affirm that this is the0iblical !octrine, + shoul! be met by the authority of manyeminent scholars, to say nothing of men of science, ho, atvarious times, have absolutely !enie! that any such !octrine isto be foun! in Genesis' +f e are to listen to many ex$ositorsof no mean authority, e must believe that hat seems so clearly!efine! in GenesisFFas if very great $ains ha! been ta%en that

there shoul! be no $ossibility of mista%eFFis not the meaning of the text at all' The account is !ivi!e! into $erio!s that e mayma%e just as long or as short as convenience reuires' (e arealso to un!erstan! that it is consistent ith the original textto believe that the most com$lex $lants an! animals may havebeen evolve! by natural $rocesses, lasting for millions of years, out of structureless ru!iments' 5 $erson ho is not aHebre scholar can only stan! asi!e an! a!mire the marvellousflexibility of a language hich a!mits of such !iverseinter$retations' 0ut assure!ly, in the face of suchcontra!ictions of authority u$on matters res$ecting hich he isincom$etent to form any ju!gment, he ill abstain, as + !o, from

giving any o$inion'

+n the thir! $lace, + have carefully abstaine! from s$ea%ing of

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this as the 6osaic !octrine, because e are no assure! u$on theauthority of the highest critics an! even of !ignitaries of thehurch, that there is no evi!ence that 6oses rote the 0oo% of Genesis, or %ne anything about it' ou ill un!erstan! that +give no ju!gmentFFit oul! be an im$ertinence u$on my $art tovolunteer even a suggestionFFu$on such a subject' 0ut, thatbeing the state of o$inion among the scholars an! the clergy, it

is ell for the unlearne! in Hebre lore, an! for the laity, toavoi! entangling themselves in such a vexe! uestion'Ha$$ily, 6ilton leaves us no excuse for !oubting hat he means,an! + shall therefore be safe in s$ea%ing of the o$inion inuestion as the 6iltonic hy$othesis'

=o e have to test that hy$othesis' -or my $art, + have no$reju!ice one ay or the other' +f there is evi!ence in favour of this vie, + am bur!ene! by no theoretical !ifficulties inthe ay of acce$ting itM but there must be evi!ence'cientific men get an a%ar! habitFFno, + ont call it that,for it is a valuable habitFFof believing nothing unless there is

evi!ence for itM an! they have a ay of loo%ing u$on belief hich is not base! u$on evi!ence, not only as illogical, but asimmoral' (e ill, if you $lease, test this vie by thecircumstantial evi!ence aloneM for, from hat + have sai!, youill un!erstan! that + !o not $ro$ose to !iscuss the uestion of hat testimonial evi!ence is to be a!!uce! in favour of it'+f those hose business it is to ju!ge are not at one as to theauthenticity of the only evi!ence of that %in! hich is offere!,nor as to the facts to hich it bears itness, the !iscussion of such evi!ence is su$erfluous'

0ut + may be $ermitte! to regret this necessity of rejecting the

testimonial evi!ence the less, because the examination of thecircumstantial evi!ence lea!s to the conclusion, not only thatit is incom$etent to justify the hy$othesis, but that, so far asit goes, it is contrary to the hy$othesis'

The consi!erations u$on hich + base this conclusion are of thesim$lest $ossible character' The 6iltonic hy$othesis containsassertions of a very !efinite character relating to thesuccession of living forms' +t is state! that $lants, for exam$le, ma!e their a$$earance u$on the thir! !ay, an! notbefore' 5n! you ill un!erstan! that hat the $oet means by$lants are such $lants as no live, the ancestors, in the

or!inary ay of $ro$agation of li%e by li%e, of the trees an!shrubs hich flourish in the $resent orl!' +t must nee!s be soMfor, if they ere !ifferent, either the existing $lants havebeen the result of a se$arate origination since that !escribe!by 6ilton, of hich e have no recor!, nor any groun! for su$$osition that such an occurrence has ta%en $laceM or elsethey have arisen by a $rocess of evolution from theoriginal stoc%s'

+n the secon! $lace, it is clear that there as no animal lifebefore the fifth !ay, an! that, on the fifth !ay, auaticanimals an! bir!s a$$eare!' 5n! it is further clear that

terrestrial living things, other than bir!s, ma!e their a$$earance u$on the sixth !ay an! not before' Hence, it follosthat, if, in the large mass of circumstantial evi!ence as to

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hat really has ha$$ene! in the $ast history of the globe efin! in!ications of the existence of terrestrial animals, other than bir!s, at a certain $erio!, it is $erfectly certain thatall that has ta%en $lace, since that time, must be referre! tothe sixth !ay'

+n the great arboniferous formation, hence 5merica !erives so

vast a $ro$ortion of her actual an! $otential ealth, in thebe!s of coal hich have been forme! from the vegetation of that$erio!, e fin! abun!ant evi!ence of the existence of terrestrial animals' They have been !escribe!, not only byEuro$ean but by your on naturalists' There are to be foun!numerous insects allie! to our coc%roaches' There are to befoun! s$i!ers an! scor$ions of large siAe, the latter so similar to existing scor$ions that it reuires the $ractise! eye of thenaturalist to !istinguish them' +nasmuch as these animals can be$rove! to have been alive in the arboniferous e$och, it is$erfectly clear that, if the 6iltonic account is to be acce$te!,the huge mass of roc%s exten!ing from the mi!!le of the

PalaeoAoic formations to the u$$ermost members of the series,must belong to the !ay hich is terme! by 6ilton the sixth'0ut, further, it is ex$ressly state! that auatic animals too%their origin on the fifth !ay, an! not beforeM hence, allformations in hich remains of auatic animals can be $rove! toexist, an! hich therefore testify that such animals live! atthe time hen these formations ere in course of !e$osition,must have been !e$osite! !uring or since the $erio! hich 6iltons$ea%s of as the fifth !ay' 0ut there is absolutely nofossiliferous formation in hich the remains of auatic animalsare absent' The ol!est fossils in the ilurian roc%s are exuviaeof marine animalsM an! if the vie hich is entertaine! by

Princi$al )ason an! )r' ar$enter res$ecting the nature of the?iBEoAoon?NiB be ellFfoun!e!, auatic animals existe! at a$erio! as far antece!ent to the !e$osition of the coal as thecoal is from usM inasmuch as the ?iBEoAoon?NiB is met ith inthose Laurentian strata hich lie at the bottom of the series of stratifie! roc%s' Hence it follos, $lainly enough, that thehole series of stratifie! roc%s, if they are to be brought intoharmony ith 6ilton, must be referre! to the fifth an! sixth!ays, an! that e cannot ho$e to fin! the slightest trace of the$ro!ucts of the earlier !ays in the geological recor!' (hen econsi!er these sim$le facts, e see ho absolutely futile arethe attem$ts that have been ma!e to !ra a $arallel beteen the

story tol! by so much of the crust of the earth as is %non tous an! the story hich 6ilton tells' The hole series of fossiliferous stratifie! roc%s must be referre! to the last to!aysM an! neither the arboniferous, nor any other, formationcan affor! evi!ence of the or% of the thir! !ay'

=ot only is there this objection to any attem$t to establish aharmony beteen the 6iltonic account an! the facts recor!e! inthe fossiliferous roc%s, but there is a further !ifficulty' 5ccor!ing to the 6iltonic account, the or!er in hich animalsshoul! have ma!e their a$$earance in the stratifie! roc%s oul!be thus4 -ishes, inclu!ing the great hales, an! bir!sM

after them, all varieties of terrestrial animals exce$t bir!s'=othing coul! be further from the facts as e fin! themM e %noof not the slightest evi!ence of the existence of bir!s before

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the Surassic, or $erha$s the Triassic, formationMhile terrestrial animals, as e have just seen, occur in thearboniferous roc%s'

+f there ere any harmony beteen the 6iltonic account an! thecircumstantial evi!ence, e ought to have abun!ant evi!ence of the existence of bir!s in the arboniferous, the )evonian, an!

the ilurian roc%s' + nee! har!ly say that this is not the case,an! that not a trace of bir!s ma%es its a$$earance until the far later $erio! hich + have mentione!'

5n! again, if it be true that all varieties of fishes an! thegreat hales, an! the li%e, ma!e their a$$earance on the fifth!ay, e ought to fin! the remains of these animals in the ol!er roc%sFFin those hich ere !e$osite! before the arboniferouse$och' -ishes e !o fin!, in consi!erable number an! varietyMbut the great hales are absent, an! the fishes are not such asno live' =ot one solitary s$ecies of fish no in existence isto be foun! in the )evonian or ilurian formations' Hence e are

intro!uce! afresh to the !ilemma hich + have alrea!y $lace!before you4 either the animals hich came into existence on thefifth !ay ere not such as those hich are foun! at $resent, arenot the !irect an! imme!iate ancestors of those hich no existMin hich case, either fresh creations of hich nothing is sai!,or a $rocess of evolution, must have occurre!M or else the holestory must be given u$, as not only !evoi! of any circumstantialevi!ence, but contrary to such evi!ence as exists'

+ $lace! before you in a fe or!s, some little time ago, astatement of the sum an! substance of 6iltons hy$othesis'Let me no try to state as briefly, the effect of the

circumstantial evi!ence bearing u$on the $ast history of theearth hich is furnishe!, ithout the $ossibility of mista%e,ith no chance of error as to its chief features, by thestratifie! roc%s' (hat e fin! is, that the great series of formations re$resents a $erio! of time of hich our humanchronologies har!ly affor! us a unit of measure' + ill not$reten! to say ho e ought to estimate this time, in millionsor in billions of years' -or my $ur$ose, the !etermination of its absolute !uration is holly unessential' 0ut that the timeas enormous there can be no uestion'

+t results from the sim$lest metho!s of inter$retation, that

leaving out of vie certain $atches of metamor$hose! roc%s, an!certain volcanic $ro!ucts, all that is no !ry lan! has oncebeen at the bottom of the aters' +t is $erfectly certain that,at a com$aratively recent $erio! of the orl!s historyFFtheretaceous e$ochFFnone of the great $hysical features hich at$resent mar% the surface of the globe existe!' +t is certainthat the /oc%y 6ountains ere not' +t is certain that theHimalaya 6ountains ere not' +t is certain that the 5l$s an! thePyrenees ha! no existence' The evi!ence is of the $lainest$ossible character an! is sim$ly this4FF(e fin! raise! u$ on theflan%s of these mountains, elevate! by the forces of u$heavalhich have given rise to them, masses of retaceous roc% hich

forme! the bottom of the sea before those mountains existe!'+t is therefore clear that the elevatory forces hich gave riseto the mountains o$erate! subseuently to the retaceous e$ochM

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an! that the mountains themselves are largely ma!e u$ of thematerials !e$osite! in the sea hich once occu$ie! their $lace' 5s e go bac% in time, e meet ith constant alternations of seaan! lan!, of estuary an! o$en oceanM an!, in corres$on!ence iththese alternations, e observe the changes in the fauna an!flora to hich + have referre!'

0ut the ins$ection of these changes gives us no right to believethat there has been any !iscontinuity in natural $rocesses'There is no trace of general cataclysms, of universal !eluges,or su!!en !estructions of a hole fauna or flora'The a$$earances hich ere formerly inter$rete! in that ay haveall been shon to be !elusive, as our %nole!ge has increase!an! as the blan%s hich formerly a$$eare! to exist beteen the!ifferent formations have been fille! u$' That there is noabsolute brea% beteen formation an! formation, that there hasbeen no su!!en !isa$$earance of all the forms of life an!re$lacement of them by others, but that changes have gone onsloly an! gra!ually, that one ty$e has !ie! out an! another has

ta%en its $lace, an! that thus, by insensible !egrees, one faunahas been re$lace! by another, are conclusions strengthene! byconstantly increasing evi!ence' o that ithin the hole of theimmense $erio! in!icate! by the fossiliferous stratifie! roc%s,there is assure!ly not the slightest $roof of any brea% in theuniformity of =atures o$erations, no in!ication that eventshave folloe! other than a clear an! or!erly seuence'

That, + say, is the natural an! obvious teaching of thecircumstantial evi!ence containe! in the stratifie! roc%s' +leave you to consi!er ho far, by any ingenuity of inter$retation, by any stretching of the meaning of language, it

can be brought into harmony ith the 6iltonic hy$othesis'

There remains the thir! hy$othesis, that of hich + have s$o%enas the hy$othesis of evolutionM an! + $ur$ose that, in lecturesto come, e shoul! !iscuss it as carefully as e have consi!ere!the other to hy$otheses' + nee! not say that it is uiteho$eless to loo% for testimonial evi!ence of evolution' The verynature of the case $reclu!es the $ossibility of such evi!ence,for the human race can no more be ex$ecte! to testify to its onorigin, than a chil! can be ten!ere! as a itness of its onbirth' <ur sole inuiry is, hat foun!ation circumstantialevi!ence len!s to the hy$othesis, or hether it len!s none, or

hether it controverts the hy$othesis' + shall !eal ith thematter entirely as a uestion of history' + shall not in!ulge inthe !iscussion of any s$eculative $robabilities' + shall notattem$t to sho that =ature is unintelligible unless e a!o$tsome such hy$othesis' -or anything + %no about the matter, itmay be the ay of =ature to be unintelligibleM she is often$uAAling, an! + have no reason to su$$ose that she is boun! tofit herself to our notions'

+ shall $lace before you three %in!s of evi!ence entirely base!u$on hat is %non of the forms of animal life hich arecontaine! in the series of stratifie! roc%s' + shall en!eavour

to sho you that there is one %in! of evi!ence hich is neutral,hich neither hel$s evolution nor is inconsistent ith it'+ shall then bring forar! a secon! %in! of evi!ence hich

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in!icates a strong $robability in favour of evolution, but !oesnot $rove itM an!, lastly, + shall a!!uce a thir! %in! of evi!ence hich, being as com$lete as any evi!ence hich e canho$e to obtain u$on such a subject, an! being holly an!stri%ingly in favour of evolution, may fairly be calle!!emonstrative evi!ence of its occurrence'

LET>/E <= E.<L>T+<=++

THE HP<THE+ <- E.<L>T+<=' THE =E>T/5L 5=)THE -5.<>/50LE E.+)E=E'

+n the $rece!ing lecture + $ointe! out that there are threehy$otheses hich may be entertaine!, an! hich have beenentertaine!, res$ecting the $ast history of life u$on the globe' 5ccor!ing to the first of these hy$otheses, living beings, such

as no exist, have existe! from all eternity u$on this earth'(e teste! that hy$othesis by the circumstantial evi!ence, as +calle! it, hich is furnishe! by the fossil remains containe! inthe earths crust, an! e foun! that it as obviously untenable'+ then $rocee!e! to consi!er the secon! hy$othesis, hich +terme! the 6iltonic hy$othesis, not because it is of any$articular conseuence hether Sohn 6ilton seriously entertaine!it or not, but because it is state! in a clear an! unmista%ablemanner in his great $oem' + $ointe! out to you that the evi!enceat our comman! as com$letely an! fully negatives that hy$othesisas it !i! the $rece!ing one' 5n! + confess that + ha! too muchres$ect for your intelligence to thin% it necessary to a!! that

the negation as eually clear an! eually vali!, hatever thesource from hich that hy$othesis might be !erive!, or hatever the authority by hich it might be su$$orte!' + further state!that, accor!ing to the thir! hy$othesis, or that of evolution,the existing state of things is the last term of a long seriesof states, hich, hen trace! bac%, oul! be foun! to sho nointerru$tion an! no breach in the continuity of naturalcausation' + $ro$ose, in the $resent an! the folloing lecture,to test this hy$othesis rigorously by the evi!ence at comman!,an! to inuire ho far that evi!ence can be sai! to bein!ifferent to it, ho far it can be sai! to be favourable toit, an!, finally, ho far it can be sai! to be !emonstrative'

-rom almost the origin of the !iscussions about the existingcon!ition of the animal an! vegetable orl!s an! the causeshich have !etermine! that con!ition, an argument has been $utforar! as an objection to evolution, hich e shall have toconsi!er very seriously' +t is an argument hich as firstclearly state! by uvier in his criticism of the !octrines$ro$oun!e! by his great contem$orary, Lamarc%' The -renchex$e!ition to Egy$t ha! calle! the attention of learne! men tothe on!erful store of antiuities in that country, an! thereha! been brought bac% to -rance numerous mummifie! cor$ses of the animals hich the ancient Egy$tians revere! an! $reserve!,

an! hich, at a reasonable com$utation, must have live! not lessthan three or four thousan! years before the time at hich theyere thus brought to light' uvier en!eavoure! to test the

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hy$othesis that animals have un!ergone gra!ual an! $rogressivemo!ifications of structure, by com$aring the s%eletons an! suchother $arts of the mummies as ere in a fitting state of $reservation, ith the corres$on!ing $arts of there$resentatives of the same s$ecies no living in Egy$t'He arrive! at the conviction that no a$$reciable change ha!ta%en $lace in these animals in the course of this consi!erable

la$se of time, an! the justice of his conclusion isnot !is$ute!'

+t is obvious that, if it can be $rove! that animals haveen!ure!, ithout un!ergoing any !emonstrable change of structure, for so long a $erio! as four thousan! years, no formof the hy$othesis of evolution hich assumes that animalsun!ergo a constant an! necessary $rogressive change can betenableM unless, in!ee!, it be further assume! that four thousan! years is too short a time for the $ro!uction of achange sufficiently great to be !etecte!'

0ut it is no less $lain that if the $rocess of evolution of animals is not in!e$en!ent of surroun!ing con!itionsM if it maybe in!efinitely hastene! or retar!e! by variations in thesecon!itionsM or if evolution is sim$ly a $rocess of accommo!ationto varying con!itionsM the argument against the hy$othesis of evolution base! on the unchange! character of the Egy$tian faunais orthless' -or the monuments hich are coeval ith themummies testify as strongly to the absence of change in the$hysical geogra$hy an! the general con!itions of the lan! of Egy$t, for the time in uestion, as the mummies !o to theunvarying characters of its living $o$ulation'

The $rogress of research since uviers time has su$$lie! far more stri%ing exam$les of the long !uration of s$ecific forms of life than those hich are furnishe! by the mummifie! +bises an!roco!iles of Egy$t' 5 remar%able case is to be foun! in your on country, in the neighbourhoo! of the falls of =iagara'+n the imme!iate vicinity of the hirl$ool, an! again u$on Goat+slan!, in the su$erficial !e$osits hich cover the surface of the roc%y subsoil in those regions, there are foun! remains of animals in $erfect $reservation, an! among them, shellsbelonging to exactly the same s$ecies as those hich at $resentinhabit the still aters of La%e Erie' +t is evi!ent, from thestructure of the country, that these animal remains ere

!e$osite! in the be!s in hich they occur at a time hen thela%e exten!e! over the region in hich they are foun!' Thisinvolves the conclusion that they live! an! !ie! before thefalls ha! cut their ay bac% through the gorge of =iagaraMan!, in!ee!, it has been !etermine! that, hen these animalslive!, the falls of =iagara must have been at least six milesfurther !on the river than they are at $resent'6any com$utations have been ma!e of the rate at hich the fallsare thus cutting their ay bac%' Those com$utations have varie!greatly, but + believe + am s$ea%ing ithin the boun!s of $ru!ence, if + assume that the falls of =iagara have notretreate! at a greater $ace than about a foot a year' ix miles,

s$ea%ing roughly, are 38,888 feetM 38,888 feet, at a foot ayear, gives 38,888 yearsM an! thus e are fairly justifie! inconclu!ing that no less a $erio! than this has $asse! since the

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shellFfish, hose remains are left in the be!s to hich + havereferre!, ere living creatures'

0ut there is still stronger evi!ence of the long !uration of certain ty$es' + have alrea!y state! that, as e or% our aythrough the great series of the Tertiary formations, e fin!many s$ecies of animals i!entical ith those hich live at the

$resent !ay, !iminishing in numbers, it is true, but stillexisting, in a certain $ro$ortion, in the ol!est of the Tertiaryroc%s' -urthermore, hen e examine the roc%s of the retaceouse$och, e fin! the remains of some animals hich the closestscrutiny cannot sho to be, in any im$ortant res$ect, !ifferentfrom those hich live at the $resent time' That is the case ithone of the cretaceous lam$Fshells C?iBTerebratula?NiBD, hichhas continue! to exist unchange!, or ith insignificantvariations, !on to the $resent !ay' uch is the case ith the?iBGlobigerinX,?NiB the s%eletons of hich, aggregate! together,form a large $ro$ortion of our English chal%'Those ?iBGlobigerinae?NiB can be trace! !on to the

?iBGlobigerinae?NiB hich live at the surface of the $resentgreat oceans, an! the remains of hich, falling to the bottom of the sea, give rise to a chal%y mu!' Hence it must be a!mitte!that certain existing s$ecies of animals sho no !istinct signof mo!ification, or transformation, in the course of a la$se of time as great as that hich carries us bac% to the retaceous$erio!M an! hich, hatever its absolute measure, is certainlyvastly greater than thirty thousan! years'

There are grou$s of s$ecies so closely allie! together, that itnee!s the eye of a naturalist to !istinguish them one fromanother' +f e !isregar! the small !ifferences hich se$arate

these forms, an! consi!er all the s$ecies of such grou$s asmo!ifications of one ty$e, e shall fin! that, even among thehigher animals, some ty$es have ha! a marvellous !uration'+n the chal%, for exam$le, there is foun! a fish belonging tothe highest an! the most !ifferentiate! grou$ of osseous fishes,hich goes by the name of ?iB0eryx'?NiB The remains of that fishare among the most beautiful an! ellF$reserve! of the fossilsfoun! in our English chal%' +t can be stu!ie! anatomically, sofar as the har! $arts are concerne!, almost as ell as if itere a recent fish' 0ut the genus ?iB0eryx?NiB is re$resente!,at the $resent !ay, by very closely allie! s$ecies hich areliving in the Pacific an! 5tlantic <ceans' (e may go still

farther bac%' + have alrea!y referre! to the fact that thearboniferous formations, in Euro$e an! in 5merica, contain theremains of scor$ions in an a!mirable state of $reservation, an!that those scor$ions are har!ly !istinguishable from such as nolive' + !o not mean to say that they are not !ifferent, butclose scrutiny is nee!e! in or!er to !istinguish them frommo!ern scor$ions'

6ore than this' 5t the very bottom of the ilurian series, inbe!s hich are by some authorities referre! to the ambrianformation, here the signs of life begin to fail usFFeven there,among the fe an! scanty animal remains hich are !iscoverable,

e fin! s$ecies of molluscous animals hich are so closelyallie! to existing forms that, at one time, they ere grou$e!un!er the same generic name' + refer to the ellF%non

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?iBLingula?NiB of the ?iBLingula?NiB flags, lately, inconseuence of some slight !ifferences, $lace! in the ne genus?iBLingulella'?NiB Practically, it belongs to the same greatgeneric grou$ as the ?iBLingula,?NiB hich is to be foun! at the$resent !ay u$on your on shores an! those of many other $artsof the orl!'

The same truth is exem$lifie! if e turn to certain great$erio!s of the earths historyFFas, for exam$le, the 6esoAoice$och' There are grou$s of re$tiles, such as the?iB+chthyosauria?NiB an! the ?iBPlesiosauria,?NiB hich a$$ear shortly after the commencement of this e$och, an! they occur invast numbers' They !isa$$ear ith the chal% an!, throughout thehole of the great series of 6esoAoic roc%s, they $resent nosuch mo!ifications as can safely be consi!ere! evi!ence of $rogressive mo!ification'

-acts of this %in! are un!oubte!ly fatal to any form of the!octrine of evolution hich $ostulates the su$$osition that

there is an intrinsic necessity, on the $art of animal formshich have once come into existence, to un!ergo continualmo!ificationM an! they are as !istinctly o$$ose! to any viehich involves the belief, that such mo!ification may occur,must ta%e $lace, at the same rate, in all the !ifferent ty$es of animal or vegetable life' The facts, as + have $lace! thembefore you, obviously !irectly contra!ict any form of thehy$othesis of evolution hich stan!s in nee! of theseto $ostulates'

0ut, one great service that has been ren!ere! by 6r' )arin tothe !octrine of evolution in general is this4 he has shon that

there are to chief factors in the $rocess of evolution4 one of them is the ten!ency to vary, the existence of hich in allliving forms may be $rove! by observationM the other is theinfluence of surroun!ing con!itions u$on hat + may call the$arent form an! the variations hich are thus evolve! from it'The cause of the $ro!uction of variations is a matter not at all$ro$erly un!erstoo! at $resent' (hether variation !e$en!s u$onsome intricate machineryFFif + may use the $hraseFFof the livingorganism itself, or hether it arises through the influence of con!itions u$on that form, is not certain, an! the uestion may,for the $resent, be left o$en' 0ut the im$ortant $oint is that,granting the existence of the ten!ency to the $ro!uction of

variationsM then, hether the variations hich are $ro!uce!shall survive an! su$$lant the $arent, or hether the $arentform shall survive an! su$$lant the variations, is a matter hich !e$en!s entirely on those con!itions hich give rise tothe struggle for existence' +f the surroun!ing con!itions aresuch that the $arent form is more com$etent to !eal ith them,an! flourish in them than the !erive! forms, then, in thestruggle for existence, the $arent form ill maintain itself an!the !erive! forms ill be exterminate!' 0ut if, on the contrary,the con!itions are such as to be more favourable to a !erive!than to the $arent form, the $arent form ill be extir$ate! an!the !erive! form ill ta%e its $lace' +n the first case, there

ill be no $rogression, no change of structure, through anyimaginable series of agesM in the secon! $lace there ill bemo!ification of change an! form'

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Thus the existence of these $ersistent ty$es, as + have terme!them, is no real obstacle in the ay of the theory of evolution'Ta%e the case of the scor$ions to hich + have just referre!'=o !oubt, since the arboniferous e$och, con!itions have alaysobtaine!, such as existe! hen the scor$ions of that e$ochflourishe!M con!itions in hich scor$ions fin! themselves better

off, more com$etent to !eal ith the !ifficulties in their ay,than any variation from the scor$ion ty$e hich they may have$ro!uce!M an!, for that reason, the scor$ion ty$e has $ersiste!,an! has not been su$$lante! by any other form' 5n! there is noreason, in the nature of things, hy, as long as this orl!exists, if there be con!itions more favourable to scor$ions thanto any variation hich may arise from them, these forms of lifeshoul! not $ersist'

Therefore, the stoc% objection to the hy$othesis of evolution,base! on the long !uration of certain animal an! vegetablety$es, is no objection at all' The facts of this characterFFan!

they are numerousFFbelong to that class of evi!ence hich + havecalle! in!ifferent' That is to say, they may affor! no !irectsu$$ort to the !octrine of evolution, but they are ca$able of being inter$rete! in $erfect consistency ith it'

There is another or!er of facts belonging to the class of negative or in!ifferent evi!ence' The great grou$ of LiAar!s,hich aboun! in the $resent orl!, exten!s through the holeseries of formations as far bac% as the Permian, or latestPalaeoAoic, e$och' These Permian liAar!s !iffer astonishinglylittle from the liAar!s hich exist at the $resent !ay'om$aring the amount of the !ifferences beteen them an! mo!ern

liAar!s, ith the $ro!igious la$se of time beteen the Permiane$och an! the $resent !ay, it may be sai! that the amount of change is insignificant' 0ut, hen e carry our researchesfarther bac% in time, e fin! no trace of liAar!s, nor of anytrue re$tile hatever, in the hole mass of formations beneaththe Permian'

=o, it is $erfectly clear that if our $alaeontologicalcollections are to be ta%en, even a$$roximately, as an a!euatere$resentation of all the forms of animals an! $lants that haveever live!M an! if the recor! furnishe! by the %non series of be!s of stratifie! roc% covers the hole series of events hich

constitute the history of life on the globe, such a fact as this!irectly contravenes the hy$othesis of evolutionM because thishy$othesis $ostulates that the existence of every form must havebeen $rece!e! by that of some form little !ifferent from it'Here, hoever, e have to ta%e into consi!eration that im$ortanttruth so ell insiste! u$on by Lyell an! by )arinFFtheim$erfection of the geological recor!' +t can be !emonstrate!that the geological recor! must be incom$lete, that it can only$reserve remains foun! in certain favourable localities an!un!er $articular con!itionsM that it must be !estroye! by$rocesses of !enu!ation, an! obliterate! by $rocesses of metamor$hosis' 0e!s of roc% of any thic%ness cramme! full of

organic remains, may yet, either by the $ercolation of ater through them, or by the influence of subterranean heat, lose alltrace of these remains, an! $resent the a$$earance of be!s of

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roc% forme! un!er con!itions in hich living forms ere absent'uch metamor$hic roc%s occur in formations of all agesM an!, invarious cases, there are very goo! groun!s for the belief thatthey have containe! organic remains, an! that those remains havebeen absolutely obliterate!'

+ insist u$on the !efects of the geological recor! the more

because those ho have not atten!e! to these matters are a$t tosay, "+t is all very ell, but, hen you get into a !ifficultyith your theory of evolution, you a$$eal to the incom$letenessan! the im$erfection of the geological recor!M" an! + ant toma%e it $erfectly clear to you that this im$erfection is a greatfact, hich must be ta%en into account in all our s$eculations,or e shall constantly be going rong'

ou see the singular series of footmar%s, !ran of its naturalsiAe in the large !iagram hanging u$ here C-ig' 7D, hich + oeto the %in!ness of my frien! Professor 6arsh, ith hom + ha!the o$$ortunity recently of visiting the $recise locality in

6assachusetts in hich these trac%s occur' + am, therefore, ableto give you my on testimony, if nee!e!, that the !iagramaccurately re$resents hat e sa' The valley of the onnecticutis classical groun! for the geologist' +t contains great be!s of san!stone, covering many suare miles, hich have evi!entlyforme! a $art of an ancient seaFshore, or, it may be, la%eFshore' -or a certain $erio! of time after their !e$osition,these be!s have remaine! sufficiently soft to receive theim$ressions of the feet of hatever animals al%e! over them,an! to $reserve them afterar!s, in exactly the same ay as suchim$ressions are at this hour $reserve! on the shores of the 0ayof -un!y an! elsehere' The !iagram re$resents the trac% of some

gigantic animal, hich al%e! on its hin! legs' ou see theseries of mar%s ma!e alternately by the right an! by the leftfootM so that, from one im$ression to the other of the threeFtoe! foot on the same si!e, is one stri!e, an! that stri!e, ase measure! it, is six feet nine inches' + leave you, therefore,to form an im$ression of the magnitu!e of the creature hich, asit al%e! along the ancient shore, ma!e these im$ressions'

-ig' 7'FFTrac%s of 0rontoAoum'

<f such im$ressions there are untol! thousan!s u$on thesesan!stones' -ifty or sixty !ifferent %in!s have been !iscovere!,an! they cover vast areas' 0ut, u$ to this $resent time, not abone, not a fragment, of any one of the animals hich left thesegreat footmar%s has been foun!M in fact, the only animal remainshich have been met ith in all these !e$osits, from the time of their !iscovery to the $resent !ayFFthough they have beencarefully hunte! overFFis a fragmentary s%eleton of one of thesmaller forms' (hat has become of the bones of all theseanimalsR ou see e are not !ealing ith little creatures, butith animals that ma%e a ste$ of six feet nine inchesM an! their remains must have been left somehere' The $robability is, that

they have been !issolve! aay, an! com$letely lost'

+ have ha! occasion to or% out the nature of fossil remains, of

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hich there as nothing left exce$t casts of the bones, thesoli! material of the s%eleton having been !issolve! out by$ercolating ater' +t as a chance, in this case, that thesan!stone ha$$ene! to be of such a constitution as to set, an!to allo the bones to be afterar! !issolve! out, leavingcavities of the exact sha$e of the bones' Ha! that constitutionbeen other than hat it as, the bones oul! have been

!issolve!, the layers of san!stone oul! have fallen together into one mass, an! not the slightest in!ication that the animalha! existe! oul! have been !iscoverable'

+ %no of no more stri%ing evi!ence than these facts affor!, of the caution hich shoul! be use! in !raing the conclusion, fromthe absence of organic remains in a !e$osit, that animals or $lants !i! not exist at the time it as forme!' + believe that,ith a right un!erstan!ing of the !octrine of evolution on theone han!, an! a just estimation of the im$ortance of theim$erfection of the geological recor! on the other, all!ifficulty is remove! from the %in! of evi!ence to hich + have

a!verte!M an! that e are justifie! in believing that all suchcases are exam$les of hat + have !esignate! negative or in!ifferent evi!enceFFthat is to say, they in no ay !irectlya!vance the hy$othesis of evolution, but they are not to beregar!e! as obstacles in the ay of our belief in that !octrine'

+ no $ass on to the consi!eration of those cases hich, for reasons hich + ill $oint out to you by an! by, are not to beregar!e! as !emonstrative of the truth of evolution, but hichare such as must exist if evolution be true, an! hich thereforeare, u$on the hole, evi!ence in favour of the !octrine' +f the!octrine of evolution be true, it follos, that, hoever !iverse

the !ifferent grou$s of animals an! of $lants may be, they mustall, at one time or other, have been connecte! by gra!ationalformsM so that, from the highest animals, hatever they may be,!on to the loest s$ec% of $roto$lasmic matter in hich lifecan be manifeste!, a series of gra!ations, lea!ing from one en!of the series to the other, either exists or has existe!'>n!oubte!ly that is a necessary $ostulate of the !octrine of evolution' 0ut hen e loo% u$on living =ature as it is, e fin!a totally !ifferent state of things' (e fin! that animals an!$lants fall into grou$s, the !ifferent members of hich are$retty closely allie! together, but hich are se$arate! by!efinite, larger or smaller, brea%s, from other grou$s' +n other

or!s, no interme!iate forms hich bri!ge over these ga$s or intervals are, at $resent, to be met ith'

To illustrate hat + mean4 Let me call your attention to thosevertebrate animals hich are most familiar to you, such asmammals, bir!s, an! re$tiles' 5t the $resent !ay, these grou$sof animals are $erfectly ellF!efine! from one another' (e %noof no animal no living hich, in any sense, is interme!iatebeteen the mammal an! the bir!, or beteen the bir! an! there$tileM but, on the contrary, there are many very !istinctanatomical $eculiarities, ellF!efine! mar%s, by hich themammal is se$arate! from the bir!, an! the bir! from the

re$tile' The !istinctions are obvious an! stri%ing if youcom$are the !efinitions of these great grou$s as they no exist'

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The same may be sai! of many of the subor!inate grou$s, or or!ers, into hich these great classes are !ivi!e!' 5t the$resent time, for exam$le, there are numerous forms of nonFruminant $achy!erms, or hat e may call broa!ly, the $ig tribe,an! many varieties of ruminants' These latter have their !efinite characteristics, an! the former have their !istinguishing $eculiarities' 0ut there is nothing that fills u$

the ga$ beteen the ruminants an! the $ig tribe' The to are!istinct' uch also is the case in res$ect of the minor grou$sof the class of re$tiles' The existing fauna shos uscroco!iles, liAar!s, sna%es, an! tortoisesM but no connectinglin% beteen the croco!ile an! liAar!, nor beteen the liAar!an! sna%e, nor beteen the sna%e an! the croco!ile, nor beteenany to of these grou$s' They are se$arate! by absolute brea%s'+f, then, it coul! be shon that this state of things ha! alaysexiste!, the fact oul! be fatal to the !octrine of evolution'+f the interme!iate gra!ations, hich the !octrine of evolutionreuires to have existe! beteen these grou$s, are not to befoun! anyhere in the recor!s of the $ast history of the globe,

their absence is a strong an! eighty negative argument againstevolutionM hile, on the other han!, if such interme!iate formsare to be foun!, that is so much to the goo! of evolutionMalthough, for reasons hich + ill lay before you by an! by, emust be cautious in our estimate of the evi!ential cogency of facts of this %in!'

+t is a very remar%able circumstance that, from the commencementof the serious stu!y of fossil remains, in fact, from the timehen uvier began his brilliant researches u$on those foun! inthe uarries of 6ontmartre, $alaeontology has shon hat she asgoing to !o in this matter, an! hat %in! of evi!ence it lay in

her $oer to $ro!uce'

+ sai! just no that, in the existing -auna, the grou$ of $igFli%e animals an! the grou$ of ruminants are entirely !istinctMbut one of the first of uviers !iscoveries as an animal hichhe calle! the ?iB5no$lotherium,?NiB an! hich $rove! to be, in agreat many im$ortant res$ects, interme!iate in character beteenthe $igs, on the one han!, an! the ruminants on the other'Thus, research into the history of the $ast !i!, to a certainextent, ten! to fill u$ the breach beteen the grou$ of ruminants an! the grou$ of $igs' 5nother remar%able animalrestore! by the great -rench $alaeontologist, the

?iBPalaeotherium,?NiB similarly ten!e! to connect together animals to all a$$earance so !ifferent as the rhinoceros, thehorse, an! the ta$ir' ubseuent research has brought to lightmultitu!es of facts of the same or!erM an! at the $resent !ay,the investigations of such anatomists as /utimeyer an! Gau!ryhave ten!e! to fill u$, more an! more, the ga$s in our existingseries of mammals, an! to connect grou$s formerly thought tobe !istinct'

0ut + thin% it may have an es$ecial interest if, instea! of !ealing ith these exam$les, hich oul! reuire a great !eal of te!ious osteological !etail, + ta%e the case of bir!s an!

re$tilesM grou$s hich, at the $resent !ay, are so clearly!istinguishe! from one another that there are $erha$s no classesof animals hich, in $o$ular a$$rehension, are more com$letely

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se$arate!' Existing bir!s, as you are aare, are covere! ithfeathersM their anterior extremities, s$ecially an! $eculiarlymo!ifie!, are converte! into ings by the ai! of hich most of them are able to flyM they al% u$right u$on to legsM an! theselimbs, hen they are consi!ere! anatomically, $resent a greatnumber of excee!ingly remar%able $eculiarities, to hich + mayhave occasion to a!vert inci!entally as + go on, an! hich are

not met ith, even a$$roximately, in any existing forms of re$tiles' <n the other han!, existing re$tiles have no feathers'They may have na%e! s%ins, or be covere! ith horny scales, or bony $lates, or ith both' They $ossess no ingsM they neither fly by means of their foreFlimbs, nor habitually al% u$rightu$on their hin!FlimbsM an! the bones of their legs $resent nosuch mo!ifications as e fin! in bir!s' +t is im$ossible toimagine any to grou$s more !efinitely an! !istinctly se$arate!,notithstan!ing certain characters hich they $ossess in common'

5s e trace the history of bir!s bac% in time, e fin! their remains, sometimes in great abun!ance, throughout the hole

extent of the tertiary roc%sM but, so far as our $resent%nole!ge goes, the bir!s of the tertiary roc%s retain the sameessential characters as the bir!s of the $resent !ay' +n other or!s, the tertiary bir!s come ithin the !efinition of theclass constitute! by existing bir!s, an! are as much se$arate!from re$tiles as existing bir!s are' =ot very long ago noremains of bir!s ha! been foun! belo the tertiary roc%s, an! +am not sure but that some $ersons ere $re$are! to !emonstratethat they coul! not have existe! at an earlier $erio!' 0ut, inthe course of the last fe years, such remains have been!iscovere! in Englan!M though, unfortunately, in so im$erfectan! fragmentary a con!ition, that it is im$ossible to say

hether they !iffere! from existing bir!s in any essentialcharacter or not' +n your country the !evelo$ment of thecretaceous series of roc%s is enormousM the con!itions un!er hich the later cretaceous strata have been !e$osite! are highlyfavourable to the $reservation of organic remainsM an! theresearches, full of labour an! ris%, hich have been carrie! onby Professor 6arsh in these cretaceous roc%s of (estern 5merica,have rear!e! him ith the !iscovery of forms of bir!s of hiche ha! hitherto no conce$tion' 0y his %in!ness, + am enable! to$lace before you a restoration of one of these extraor!inarybir!s, every $art of hich can be thoroughly justifie! by themore or less com$lete s%eletons, in a very $erfect state of

$reservation, hich he has !iscovere!' This ?iBHes$erornis?NiBC-ig' 3D, hich measure! beteen five an! six feet in length, isastonishingly li%e our existing !ivers or grebes in a great manyres$ectsM so li%e them in!ee! that, ha! the s%eleton of ?iBHes$erornis?NiB been foun! in a museum ithout its s%ull, it$robably oul! have been $lace! in the same grou$ of bir!s asthe !ivers an! grebes of the $resent !ay'?1B0ut ?iBHes$erornis?NiB !iffers from all existing bir!s, an! sofar resembles re$tiles, in one im$ortant $articularFFit is$rovi!e! ith teeth' The long jas are arme! ith teeth hichhave curve! crons an! thic% roots C-ig' D, an! are not set in!istinct soc%ets, but are lo!ge! in a groove' +n $ossessing true

teeth, the ?iBHes$erornis?NiB !iffers from every existing bir!,an! from every bir! yet !iscovere! in the tertiary formations,the toothFli%e serrations of the jas in the ?iB<!onto$teryx?NiB

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of the Lon!on clay being mere $rocesses of the bony substance of the jas, an! not teeth in the $ro$er sense of the or!' +n vieof the characteristics of this bir! e are therefore oblige! tomo!ify the !efinitions of the classes of bir!s an! re$tiles'0efore the !iscovery of ?iBHes$erornis,?NiB the !efinition of the class 5ves base! u$on our %nole!ge of existing bir!s mighthave been exten!e! to all bir!sM it might have been sai! that

the absence of teeth as characteristic of the class of bir!sMbut the !iscovery of an animal hich, in every $art of itss%eleton, closely agrees ith existing bir!s, an! yet $ossessesteeth, shos that there ere ancient bir!s hich, in res$ect of $ossessing teeth, a$$roache! re$tiles more nearly than anyexisting bir! !oes, an!, to that extent, !iminishes the?iBhiatus?NiB beteen the to classes'

-ig' 3FFHes$erornis regalis C6arshD

-ig' FFHes$erornis regalis C6arshD

Ci!e an! u$$er vies of half the loer jaM si!e an! en! viesof a vertebra an! a se$arate tooth'D

The same formation has yiel!e! another bir!, ?iB+chthyornis?NiBC-ig' D, hich also $ossesses teethM but the teeth are situate!in !istinct soc%ets, hile those of ?iBHes$erornis?NiB are notso lo!ge!' The latter also has such very small, almostru!imentary ings, that it must have been chiefly a simmer an!a !iver li%e a PenguinM hile ?iB+chthyornis?NiB has strongings an! no !oubt $ossesse! corres$on!ing $oers of flight'?iB+chthyornis?NiB also !iffere! in the fact that its vertebrae

have not the $eculiar characters of the vertebrae of existingan! of all %non tertiary bir!s, but ere concave at each en!'This !iscovery lea!s us to ma%e a further mo!ification in the!efinition of the grou$ of bir!s, an! to $art ith another of the characters by hich almost all existing bir!s are!istinguishe! from re$tiles'

-igure' FF+chthyornis )is$ar C6arshD'i!e an! u$$er vies of half the loer jaM an! si!e an! en!vies of a vertebra'D

5$art from the fe fragmentary remains from the Englishgreensan!, to hich + have referre!, the 6esoAoic roc%s, ol!er than those in hich ?iBHes$erornis?NiB an! ?iB+chthyornis?NiBhave been !iscovere!, have affor!e! no certain evi!ence of bir!s, ith the remar%able exce$tion of the olenhofen slates'These soFcalle! slates are com$ose! of a fine graine! calcareousmu! hich has har!ene! into lithogra$hic stone, an! in hichorganic remains are almost as ell $reserve! as they oul! be if they ha! been imbe!!e! in so much $laster of Paris' They haveyiel!e! the ?iB5rchaeo$teryx,?NiB the existence of hich asfirst ma!e %non by the fin!ing of a fossil feather, or rather

of the im$ression of one' +t is on!erful enough that such a$erishable thing as a feather, an! nothing more, shoul! be!iscovere!M yet, for a long time, nothing as %non of this bir!

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exce$t its feather' 0ut by an! by a solitary s%eleton as!iscovere! hich is no in the 0ritish 6useum' The s%ull of thissolitary s$ecimen is unfortunately anting, an! it is thereforeuncertain hether the ?iB5rchaeo$teryx?NiB $ossesse! teeth or not'?7B 0ut the remain!er of the s%eleton is so ell $reserve!as to leave no !oubt res$ecting the main features of the animal,hich are very singular' The feet are not only altogether bir!F

li%e, but have the s$ecial characters of the feet of $erchingbir!s, hile the bo!y ha! a clothing of true feathers'=evertheless, in some other res$ects, ?iB5rchaeo$teryx?NiB isunli%e a bir! an! li%e a re$tile' There is a long tail com$ose!of many vertebrae' The structure of the ing !iffers in somevery remar%able res$ects from that hich it $resents in a truebir!' +n the latter, the en! of the ing ansers to the thumban! to fingers of my han!M but the metacar$al bones, or thosehich anser to the bones of the fingers hich lie in the $almof the han!, are fuse! together into one massM an! the holea$$aratus, exce$t the last joints of the thumb, is boun! u$ in asheath of integument, hile the e!ge of the han! carries the

$rinci$al uillFfeathers' +n the ?iB5rchaeo$teryx,?NiB theu$$erFarm bone is li%e that of a bir!M an! the to bones of theforearm are more or less li%e those of a bir!, but the fingersare not boun! togetherFFthey are free' (hat their number mayhave been is uncertainM but several, if not all, of them ereterminate! by strong curve! clas, not li%e such as aresometimes foun! in bir!s, but such as re$tiles $ossessM so that,in the ?iB5rchaeo$teryx,?NiB e have an animal hich, to acertain extent, occu$ies a mi!ay $lace beteen a bir! an! are$tile' +t is a bir! so far as its foot an! sun!ry other $artsof its s%eleton are concerne!M it is essentially an! thoroughlya bir! by its feathersM but it is much more $ro$erly a re$tile

in the fact that the region hich re$resents the han! hasse$arate bones, ith clas resembling those hich terminate theforelimb of a re$tile' 6oreover, it has a long re$tileFli%e tailith a fringe of feathers on each si!eM hile, in all true bir!shitherto %non, the tail is relatively short, an! the vertebraehich constitute its s%eleton are generally $eculiarly mo!ifie!'

Li%e the ?iB5no$lotherium?NiB an! the ?iBPalaeotherium,?NiBtherefore, ?iB5rchaeo$teryx?NiB ten!s to fill u$ the intervalbeteen grou$s hich, in the existing orl!, are i!elyse$arate!, an! to !estroy the value of the !efinitions of Aoological grou$s base! u$on our %nole!ge of existing forms'

5n! such cases as these constitute evi!ence in favour of evolution, in so far as they $rove that, in former $erio!s of the orl!s history, there ere animals hich overste$$e! theboun!s of existing grou$s, an! ten!e! to merge them into larger assemblages' They sho that animal organisation is more flexiblethan our %nole!ge of recent forms might have le! us to believeMan! that many structural $ermutations an! combinations, of hichthe $resent orl! gives us no in!ication, may neverthelesshave existe!'

0ut it by no means follos, because the ?iBPalaeotherium?NiB hasmuch in common ith the horse, on the one han!, an! ith the

rhinoceros on the other, that it is the interme!iate formthrough hich rhinoceroses have $asse! to become horses, or ?iBvice versaM?NiB on the contrary, any such su$$osition oul!

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certainly be erroneous' =or !o + thin% it li%ely that thetransition from the re$tile to the bir! has been effecte! bysuch a form as ?iB5rchaeo$teryx'?NiB 5n! it is convenient to!istinguish these interme!iate forms beteen to grou$s, hich!o not re$resent the actual $assage from the one grou$ to theother, as ?iBintercalary?NiB ty$es, from those ?iBlinear?NiBty$es hich, more or less a$$roximately, in!icate the nature of

the ste$s by hich the transition from one grou$ to the other as effecte!'

+ conceive that such linear forms, constituting a series of natural gra!ations beteen the re$tile an! the bir!, an!enabling us to un!erstan! the manner in hich the re$tilian hasbeen metamor$hose! into the bir! ty$e, are really to be foun!among a grou$ of ancient an! extinct terrestrial re$tiles %nonas the ?iB<rnithosceli!a'?NiB The remains of these animals occur throughout the series of mesoAoic formations, from the Trias tothe hal%, an! there are in!ications of their existence even inthe later PalaeoAoic strata'

6ost of these re$tiles, at $resent %non, are of great siAe,some having attaine! a length of forty feet or $erha$s more'The majority resemble! liAar!s an! croco!iles in their generalform, an! many of them ere, li%e croco!iles, $rotecte! by anarmour of heavy bony $lates' 0ut, in others, the hin! limbselongate an! the fore limbs shorten, until their relative$ro$ortions a$$roach those hich are observe! in the shortFinge!, flightless, ostrich tribe among bir!s'

The s%ull is relatively light, an! in some cases the jas,though bearing teeth, are bea%Fli%e at their extremities an!

a$$ear to have been envelo$e! in a horny sheath' +n the $art of the vertebral column hich lies beteen the haunch bones an! iscalle! the sacrum, a number of vertebrae may unite together intoone hole, an! in this res$ect, as in some !etails of itsstructure, the sacrum of these re$tiles a$$roaches thatof bir!s'

0ut it is in the structure of the $elvis an! of the hin! limbthat some of these ancient re$tiles $resent the most remar%ablea$$roximation to bir!s, an! clearly in!icate the ay by hichthe most s$ecialise! an! characteristic features of the bir! mayhave been evolve! from the corres$on!ing $arts of the re$tile'

+n -ig' :, the $elvis an! hin! limbs of a croco!ile, a threeFtoe! bir!, an! an ornithosceli!an are re$resente! si!e by si!eMan!, for facility of com$arison, in corres$on!ing $ositionsMbut it must be recollecte! that, hile the $osition of thebir!s limb is natural, that of the croco!ile is not so' +n thebir!, the thigh bone lies close to the bo!y, an! the metatarsalbones of the foot Cii', iii', iv', -ig' :D are, or!inarily,raise! into a more or less vertical $ositionM in the croco!ile,the thigh bone stan!s out at an angle from the bo!y, an! themetatarsal bones Ci', ii', iii', iv', -ig' :D lie flat on thegroun!' Hence, in the croco!ile, the bo!y usually lies suat

beteen the legs, hile, in the bir!, it is raise! u$on the hin!legs, as u$on $illars'

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+n the croco!ile, the $elvis is obviously com$ose! of threebones on each si!e4 the ilium C?iB+l'?NiBD, the $ubisC?iBPb'?NiBD, an! the ischium C?iB+s'?NiBD' +n the a!ult bir!there a$$ears to be but one bone on each si!e' The examinationof the $elvis of a chic%, hoever, shos that each half is ma!eu$ of three bones, hich anser to those hich remain !istinctthroughout life in the croco!ile' There is, therefore, a

fun!amental i!entity of $lan in the construction of the $elvisof both bir! an! re$tileM though the !ifference in form,relative siAe, an! !irection of the corres$on!ing bones in theto cases are very great'

0ut the most stri%ing contrast beteen the to lies in the bonesof the leg an! of that $art of the foot terme! the tarsus, hichfollos u$on the leg' +n the croco!ile, the fibula C?iB-?NiBD isrelatively large an! its loer en! is com$lete' The tibiaC?iBT?NiBD has no mar%e! crest at its u$$er en!, an! its loer en! is narro an! not $ulleyFsha$e!' There are to ros of se$arate tarsal bones C?iB5s', a', Yc'?NiBD an! four !istinct

metatarsal bones, ith a ru!iment of a fifth'

+n the bir!, the fibula is small an! its loer en! !iminishes toa $oint' The tibia has a strong crest at its u$$er en! an! itsloer extremity $asses into a broa! $ulley' There seem at firstto be no tarsal bonesM an! only one bone, !ivi!e! at the en!into three hea!s for the three toes hich are attache! to it,a$$ears in the $lace of the metatarsus'

+n the young bir!, hoever, the $ulleyFsha$e! a$$arent en! of the tibia is a !istinct bone, hich re$resents the bones mar%e!?iB5s', a',?NiB in the croco!ileM hile the a$$arently single

metatarsal bone consists of three bones, hich early unite ithone another an! ith an a!!itional bone, hich re$resents theloer ro of bones in the tarsus of the croco!ile'

+n other or!s, it can be shon by the stu!y of !evelo$ment thatthe bir!s $elvis an! hin! limb are sim$ly extreme mo!ificationsof the same fun!amental $lan as that u$on hich these $arts aremo!elle! in re$tiles'

<n com$aring the $elvis an! hin! limb of the ornithosceli!anith that of the croco!ile, on the one si!e, an! that of thebir!, on the other C-ig' :D, it is obvious that it re$resents a

mi!!le term beteen the to' The $elvic bones a$$roach the formof those of the bir!s, an! the !irection of the $ubis an!ischium is nearly that hich is characteristic of bir!sMthe thigh bone, from the !irection of its hea!, must have lainclose to the bo!yM the tibia has a great crestM an!, immovablyfitte! on to its loer en!, there is a $ulleyFsha$e! bone, li%ethat of the bir!, but remaining !istinct' The loer en! of thefibula is much more slen!er, $ro$ortionally, than in thecroco!ile' The metatarsal bones have such a form that they fittogether immovably, though they !o not enter into bony unionMthe thir! toe is, as in the bir!, longest an! strongest'+n fact, the ornithosceli!an limb is com$arable to that of an

unhatche! chic%'

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-ig' :'FF0ir!' <rnithosceli!an' roco!ile'The letters have the same signification in all the figures'?iB+l',?NiB +liumM ?iBa'?NiB anterior en!M ?iBb'?NiB $osterior en!M ?iB+a'?NiB ischiumM ?iBPb',?NiB $ubisM ?iBT,?NiB tibiaM?iB-,?NiB fibulaM ?iB5s',?NiB astragalusM ?iBa',?NiB calcaneumM+, !istal $ortion of the tarsusM i', ii', iii', iv', metatarsalbones'

Ta%ing all these facts together, it is obvious that the vie,hich as entertaine! by 6antell an! the $robability of hichas !emonstrate! by your on !istinguishe! anatomist, Lei!y,hile much a!!itional evi!ence in the same !irection has beenfurnishe! by Professor o$e, that some of these animals may haveal%e! u$on their hin! legs as bir!s !o, acuires great eight'+n fact, there can be no reasonable !oubt that one of thesmaller forms of the ?iB<rnithosceli!a, om$sognathus,?NiB thealmost entire s%eleton of hich has been !iscovere! in theolenhofen slates, as a bi$e!al animal' The $arts of this

s%eleton are somehat tiste! out of their natural relations,but the accom$anying figure gives a just vie of the generalform of ?iBom$sognathus?NiB an! of the $ro$ortions of itslimbsM hich, in some res$ects, are more com$letely bir!Fli%ethan those of other ?iB<rnithosceli!a'?NiB

-ig' 'FF/estoration of om$sognathus Longi$es

(e have ha! to stretch the !efinition of the class of bir!s soas to inclu!e bir!s ith teeth an! bir!s ith $aFli%e fore

limbs an! long tails' There is no evi!ence that?iBom$sognathus?NiB $ossesse! feathersM but, if it !i!, itoul! be har! in!ee! to say hether it shoul! be calle! are$tilian bir! or an avian re$tile'

5s ?iBom$sognathus?NiB al%e! u$on its hin! legs, it must havema!e trac%s li%e those of bir!s' 5n! as the structure of thelimbs of several of the gigantic ?iB<rnithosceli!a,?NiB such as?iB+guano!on,?NiB lea!s to the conclusion that they also mayhave constantly, or occasionally, assume! the same attitu!e, a$eculiar interest attaches to the fact that, in the (eal!enstrata of Englan!, there are to be foun! gigantic footste$s,

arrange! in or!er li%e those of the ?iB0rontoAoum,?NiB an! hichthere can be no reasonable !oubt ere ma!e by some of the?iB<rnithosceli!a,?NiB the remains of hich are foun! in thesame roc%s' 5n!, %noing that re$tiles that al%e! u$on their hin! legs an! share! many of the anatomical characters of bir!s!i! once exist, it becomes a very im$ortant uestion hether thetrac%s in the Trias of 6assachusetts, to hich + referre! sometime ago, an! hich formerly use! to be unhesitatingly ascribe!to bir!s, may not all have been ma!e by ornithosceli!anre$tilesM an! hether, if e coul! obtain the s%eletons of theanimals hich ma!e these trac%s, e shoul! not fin! in them theactual ste$s of the evolutional $rocess by hich re$tiles gave

rise to bir!s'

The evi!ential value of the facts + have brought forar! in this

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Lecture must be neither over nor un!er estimate!' +t is nothistorical $roof of the occurrence of the evolution of bir!sfrom re$tiles, for e have no safe groun! for assuming that truebir!s ha! not ma!e their a$$earance at the commencement of the6esoAoic e$och' +t is, in fact, uite $ossible that all thesemore or less aviFform re$tiles of the 6esoAoic e$ochs are notterms in the series of $rogression from bir!s to re$tiles at

all, but sim$ly the more or less mo!ifie! !escen!ants of PalaeoAoic forms through hich that transition asactually effecte!'

(e are not in a $osition to say that the %non?iB<rnithosceli!a?NiB are interme!iate in the or!er of their a$$earance on the earth beteen re$tiles an! bir!s' 5ll that canbe sai! is that, if in!e$en!ent evi!ence of the actualoccurrence of evolution is $ro!ucible, then these intercalaryforms remove every !ifficulty in the ay of un!erstan!ing hatthe actual ste$s of the $rocess, in the case of bir!s, mayhave been'

That intercalary forms shoul! have existe! in ancient times is anecessary conseuence of the truth of the hy$othesis of evolutionM an!, hence, the evi!ence + have lai! before you in$roof of the existence of such forms, is, so far as it goes, infavour of that hy$othesis'

There is another series of extinct re$tiles hich may be sai! tobe intercalary beteen re$tiles an! bir!s, in so far as theycombine some of the characters of both these grou$sM an! hich,as they $ossesse! the $oer of flight, may seem, at first sight,to be nearer re$resentatives of the forms by hich the

transition from the re$tile to the bir! as effecte!, than the?iB<rnithosceli!a'?NiB

These are the ?iBPterosauria,?NiB or Ptero!actyles, the remainsof hich are met ith throughout the series of 6esoAoic roc%s,from the lias to the chal%, an! some of hich attaine! a greatsiAe, their ings having a s$an of eighteen or tenty feet'These animals, in the form an! $ro$ortions of the hea! an! nec%relatively to the bo!y, an! in the fact that the en!s of the jas ere often, if not alays, more or less extensivelyensheathe! in horny bea%s, remin! us of bir!s' 6oreover, their bones containe! air cavities, ren!ering them s$ecifically

lighter, as is the case in most bir!s' The breast bone as largean! %eele!, as in most bir!s an! in bats, an! the shoul!er gir!le is stri%ingly similar to that of or!inary bir!s' 0ut, itseems to me, that the s$ecial resemblance of $tero!actyles tobir!s en!s here, unless + may a!! the entire absence of teethhich characterises the great $tero!actyles ?iBCPterano!onD?NiB!iscovere! by Professor 6arsh' 5ll other %non $tero!actyleshave teeth lo!ge! in soc%ets' +n the vertebral column an! thehin! limbs there are no s$ecial resemblances to bir!s, an! hene turn to the ings they are foun! to be constructe! on atotally !ifferent $rinci$le from those of bir!s'

-ig' O'FFPtero!actylus $ectabilis C.on 6eyerD'

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There are four fingers' These four fingers are large, an! threeof them, those hich anser to the thumb an! to folloingfingers in my han!FFare terminate! by clas, hile the fourth isenormously $rolonge! an! converte! into a great jointe! style'ou see at once, from hat + have state! about a bir!s ing,that there coul! be nothing less li%e a bir!s ing than this

is' +t as conclu!e! by general reasoning that this finger ha!the office of su$$orting a eb hich exten!e! beteen it an! thebo!y' 5n existing s$ecimen $roves that such as really the case,an! that the $tero!actyles ere !evoi! of feathers, but that thefingers su$$orte! a vast eb li%e that of a bats ingM in fact,there can be no !oubt that this ancient re$tile fle after thefashion of a bat'

Thus, though the $tero!actyle is a re$tile hich has becomemo!ifie! in such a manner as to enable it to fly, an! therefore,as might be ex$ecte!, $resents some $oints of resemblance toother animals hich flyM it has, so to s$ea%, gone off the line

hich lea!s !irectly from re$tiles to bir!s, an! has become!isualifie! for the changes hich lea! to the characteristicorganisation of the latter class' Therefore, viee! in relationto the classes of re$tiles an! bir!s, the $tero!actyles a$$ear to me to be, in a limite! sense, intercalary formsM but they arenot even a$$roximately linear, in the sense of exem$lifyingthose mo!ifications of structure through hich the $assage fromthe re$tile to the bir! too% $lace'

LET>/E <= E.<L>T+<=

+++THE )E6<=T/5T+.E E.+)E=E <- E.<L>T+<=

The occurrence of historical facts is sai! to be !emonstrate!,hen the evi!ence that they ha$$ene! is of such a character asto ren!er the assum$tion that they !i! not ha$$en in the highest!egree im$robableM an! the uestion + no have to !eal ith is,hether evi!ence in favour of the evolution of animals of this!egree of cogency is, or is not, obtainable from the recor! of the succession of living forms hich is $resente! to us by

fossil remains'

Those ho have atten!e! to the $rogress of $alaeontology areaare that evi!ence of the character hich + have !efine! hasbeen $ro!uce! in consi!erable an! continuallyFincreasinguantity !uring the last fe years' +n!ee!, the amount an! thesatisfactory nature of that evi!ence are somehat sur$rising,hen e consi!er the con!itions un!er hich alone e can ho$e toobtain it'

+t is obviously useless to see% for such evi!ence exce$t inlocalities in hich the $hysical con!itions have been such as to

$ermit of the !e$osit of an unbro%en, or but rarely interru$te!,series of strata through a long $erio! of timeM in hich thegrou$ of animals to be investigate! has existe! in such

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abun!ance as to furnish the reuisite su$$ly of remainsM an! inhich, finally, the materials com$osing the strata are such asto ensure the $reservation of these remains in a tolerably$erfect an! un!isturbe! state'

+t so ha$$ens that the case hich, at $resent, most nearlyfulfils all these con!itions is that of the series of extinct

animals hich culminates in the horsesM by hich term + mean to!enote not merely the !omestic animals ith hich e are all soell acuainte!, but their allies, the ass, Aebra, uagga, an!the li%e' +n short, + use "horses" as the euivalent of thetechnical name ?iBEui!ae,?NiB hich is a$$lie! to the holegrou$ of existing euine animals'

The horse is in many ays a remar%able animalM not least so inthe fact that it $resents us ith an exam$le of one of the most$erfect $ieces of machinery in the living orl!' +n truth, amongthe or%s of human ingenuity it cannot be sai! that there is anylocomotive so $erfectly a!a$te! to its $ur$oses, !oing so much

or% ith so small a uantity of fuel, as this machine of natures manufactureFFthe horse' 5n!, as a necessary conseuenceof any sort of $erfection, of mechanical $erfection as of others, you fin! that the horse is a beautiful creature, one of the most beautiful of all lan!Fanimals' Loo% at the $erfectbalance of its form, an! the rhythm an! force of its action'The locomotive machinery is, as you are aare, resi!ent in itsslen!er fore an! hin! limbsM they are flexible an! elasticlevers, ca$able of being move! by very $oerful musclesM an!, inor!er to su$$ly the engines hich or% these levers ith theforce hich they ex$en!, the horse is $rovi!e! ith a very$erfect a$$aratus for grin!ing its foo! an! extracting therefrom

the reuisite fuel'

(ithout attem$ting to ta%e you very far into the region of osteological !etail, + must nevertheless trouble you ith somestatements res$ecting the anatomical structure of the horseMan!, more es$ecially, ill it be nee!ful to obtain a generalconce$tion of the structure of its fore an! hin! limbs, an! of its teeth' 0ut + shall only touch u$on those $oints hich areabsolutely essential to our inuiry'

Let us turn in the first $lace to the foreFlimb' +n mostua!ru$e!s, as in ourselves, the foreFarm contains !istinct

bones calle! the ra!ius an! the ulna' The corres$on!ing regionin the horse seems at first to $ossess but one bone' arefulobservation, hoever, enables us to !istinguish in this bone a$art hich clearly ansers to the u$$er en! of the ulna' This isclosely unite! ith the chief mass of the bone hich re$resentsthe ra!ius, an! runs out into a slen!er shaft hich may betrace! for some !istance !onar!s u$on the bac% of the ra!ius,an! then in most cases thins out an! vanishes' +t ta%es stillmore trouble to ma%e sure of hat is nevertheless the fact, thata small $art of the loer en! of the bone of the horses forearm, hich is only !istinct in a very young foal, is really theloer extremity of the ulna'

(hat is commonly calle! the %nee of a horse is its rist'The "cannon bone" ansers to the mi!!le bone of the five

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metacar$al bones, hich su$$ort the $alm of the han! inourselves' The "$astern," "coronary," an! "coffin" bones of veterinarians anser to the joints of our mi!!le fingers, hilethe hoof is sim$ly a greatly enlarge! an! thic%ene! nail' 0ut if hat lies belo the horses "%nee" thus corres$on!s to themi!!le finger in ourselves, hat has become of the four other fingers or !igitsR (e fin! in the $laces of the secon! an!

fourth !igits only to slen!er s$lintFli%e bones, about toFthir!s as long as the cannon bone, hich gra!ually ta$er totheir loer en!s an! bear no finger joints, or, as they areterme!, $halanges' ometimes, small bony or gristly no!ules areto be foun! at the bases of these to metacar$al s$lints, an! itis $robable that these re$resent ru!iments of the first an!fifth toes' Thus, the $art of the horses s%eleton, hichcorres$on!s ith that of the human han!, contains one overgronmi!!le !igit, an! at least to im$erfect lateral !igitsM an!these anser, res$ectively, to the thir!, the secon!, an! thefourth fingers in man'

orres$on!ing mo!ifications are foun! in the hin! limb'+n ourselves, an! in most ua!ru$e!s, the leg contains to!istinct bones, a large bone, the tibia, an! a smaller an! moreslen!er bone, the fibula' 0ut, in the horse, the fibula seems,at first, to be re!uce! to its u$$er en!M a short slen!er boneunite! ith the tibia, an! en!ing in a $oint belo, occu$yingits $lace' Examination of the loer en! of a young foals shinbone, hoever, shos a !istinct $ortion of osseous matter, hichis the loer en! of the fibulaM so that the a$$arently single,loer en! of the shin bone is really ma!e u$ of the coalesce!en!s of the tibia an! fibula, just as the, a$$arently single,loer en! of the foreFarm bone is com$ose! of the coalesce!

ra!ius an! ulna'

The heel of the horse is the $art commonly %non as the hoc%'The hin!er cannon bone ansers to the mi!!le metatarsal bone of the human foot, the $astern, coronary, an! coffin bones, to themi!!le toe bonesM the hin! hoof to the nailM as in the foreFfoot' 5n!, as in the foreFfoot, there are merely to s$lints tore$resent the secon! an! the fourth toes' ometimes a ru!imentof a fifth toe a$$ears to be traceable'

The teeth of a horse are not less $eculiar than its limbs' Theliving engine, li%e all others, must be ell sto%e! if it is to

!o its or%M an! the horse, if it is to ma%e goo! its ear an!tear, an! to exert the enormous amount of force reuire! for its$ro$ulsion, must be ell an! ra$i!ly fe!' To this en!, goo!cutting instruments an! $oerful an! lasting crushers arenee!ful' 5ccor!ingly, the telve cutting teeth of a horse arecloseFset an! concentrate! in the foreF$art of its mouth, li%eso many a!Aes or chisels' The grin!ers or molars are large, an!have an extremely com$licate! structure, being com$ose! of anumber of !ifferent substances of uneual har!ness' Theconseuence of this is that they ear aay at !ifferent ratesMan!, hence, the surface of each grin!er is alays as uneven asthat of a goo! millstone'

+ have sai! that the structure of the grin!ing teeth is verycom$licate!, the har!er an! the softer $arts being, as it ere,

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interlace! ith one another' The result of this is that, as thetooth ears, the cron $resents a $eculiar $attern, the natureof hich is not very easily !eci$here! at firstM but hich it isim$ortant e shoul! un!erstan! clearly' Each grin!ing tooth of the u$$er ja has an ?iBouter all?NiB so sha$e! that, on theorn cron, it exhibits the form of to crescents, one in frontan! one behin!, ith their concave si!es turne! outar!s' -rom

the inner si!e of the front crescent, a crescentic ?iBfrontri!ge?NiB $asses inar!s an! bac%ar!s, an! its inner faceenlarges into a strong longitu!inal fol! or ?iB$illar'?NiB-rom the front $art of the hin!er crescent, a ?iBbac% ri!ge?NiBta%es a li%e !irection, an! also has its ?iB$illar'?NiB

The !ee$ inters$aces or ?iBvalleys?NiB beteen these ri!ges an!the outer all are fille! by bony substance, hich is calle!?iBcement,?NiB an! coats the hole tooth'

The $attern of the orn face of each grin!ing tooth of the loer ja is uite !ifferent' +t a$$ears to be forme! of to crescentF

sha$e! ri!ges, the convexities of hich are turne! outar!s'The free extremity of each crescent has a ?iB$illar,?NiB an!there is a large !ouble ?iB$illar?NiB here the to crescentsmeet' The hole structure is, as it ere, imbe!!e! in cement,hich fills u$ the valleys, as in the u$$er grin!ers'

+f the grin!ing faces of an u$$er an! of a loer molar of thesame si!e are a$$lie! together, it ill be seen that the o$$ose!ri!ges are nohere $arallel, but that they freuently crossMan! that thus, in the act of mastication, a har! surface in theone is constantly a$$lie! to a soft surface in the other, an!?iBvice versa'?NiB They thus constitute a grin!ing a$$aratus of

great efficiency, an! one hich is re$aire! as fast as it ears,oing to the longFcontinue! groth of the teeth'

ome other $eculiarities of the !entition of the horse must benotice!, as they bear u$on hat + shall have to say by an! by'Thus the crons of the cutting teeth have a $eculiar !ee$ $it,hich gives rise to the ellF%non "mar%" of the horse' There isa large s$ace beteen the outer incisors an! the front grin!er'+n this s$ace the a!ult male horse $resents, near the incisorson each si!e, above an! belo, a canine or "tush," hich iscommonly absent in mares' +n a young horse, moreover, there isnot unfreuently to be seen in front of the first grin!er, a

very small tooth, hich soon falls out' +f this small tooth becounte! as one, it ill be foun! that there are seven teethbehin! the canine on each si!eM namely, the small tooth inuestion, an! the six great grin!ers, among hich, by an unusual$eculiarity, the foremost tooth is rather larger than thosehich follo it'

+ have no enumerate! those characteristic structures of thehorse hich are of most im$ortance for the $ur$ose e havein vie'

To any one ho is acuainte! ith the mor$hology of vertebrate!

animals, they sho that the horse !eviates i!ely from thegeneral structure of mammalsM an! that the horse ty$e is, inmany res$ects, an extreme mo!ification of the general mammalian

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$lan' The least mo!ifie! mammals, in fact, have the ra!ius an!ulna, the tibia an! fibula, !istinct an! se$arate' They havefive !istinct an! com$lete !igits on each foot, an! no one of these !igits is very much larger than the rest' 6oreover, in theleast mo!ifie! mammals, the total number of the teeth is verygenerally fortyFfour, hile in horses, the usual number isforty, an! in the absence of the canines, it may be re!uce! to

thirtyFsixM the incisor teeth are !evoi! of the fol! seen inthose of the horse4 the grin!ers regularly !iminish in siAe fromthe mi!!le of the series to its front en!M hile their cronsare short, early attain their full length, an! exhibit sim$leri!ges or tubercles, in $lace of the com$lex fol!ings of thehorses grin!ers'

Hence the general $rinci$les of the hy$othesis of evolution lea!to the conclusion that the horse must have been !erive! fromsome ua!ru$e! hich $ossesse! five com$lete !igits on eachfootM hich ha! the bones of the foreFarm an! of the legcom$lete an! se$arateM an! hich $ossesse! fortyFfour teeth,

among hich the crons of the incisors an! grin!ers ha! a sim$lestructureM hile the latter gra!ually increase! in siAe frombefore bac%ar!s, at any rate in the anterior $art of theseries, an! ha! short crons'

5n! if the horse has been thus evolve!, an! the remains of the!ifferent stages of its evolution have been $reserve!, theyought to $resent us ith a series of forms in hich the number of the !igits becomes re!uce!M the bones of the foreFarm an! leggra!ually ta%e on the euine con!itionM an! the form an!arrangement of the teeth successively a$$roximate to those hichobtain in existing horses'

Let us turn to the facts, an! see ho far they fulfil thesereuirements of the !octrine of evolution'

+n Euro$e abun!ant remains of horses are foun! in the Uuaternaryan! later Tertiary strata as far as the Pliocene formation'0ut these horses, hich are so common in the caveF!e$osits an!in the gravels of Euro$e, are in all essential res$ects li%eexisting horses' 5n! that is true of all the horses of thelatter $art of the Pliocene e$och' 0ut, in !e$osits hich belongto the earlier Pliocene an! later 6iocene e$ochs, an! hichoccur in 0ritain, in -rance, in Germany, in Greece, in +n!ia, e

fin! animals hich are extremely li%e horsesFFhich, in fact,are so similar to horses, that you may follo !escri$tions givenin or%s u$on the anatomy of the horse u$on the s%eletons of these animalsFFbut hich !iffer in some im$ortant $articulars'-or exam$le, the structure of their fore an! hin! limbs issomehat !ifferent' The bones hich, in the horse, arere$resente! by to s$lints, im$erfect belo, are as long as themi!!le metacar$al an! metatarsal bonesM an!, attache! to theextremity of each, is a !igit ith three joints of the samegeneral character as those of the mi!!le !igit, only very muchsmaller' These small !igits are so !is$ose! that they coul! haveha! but very little functional im$ortance, an! they must have

been rather of the nature of the !eFclas, such as are to befoun! in many ruminant animals' The ?iBHi$$arion,?NiB as theextinct Euro$ean threeFtoe! horse is calle!, in fact, $resents a

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foot similar to that of the 5merican ?iBProtohi$$us?NiBC-ig' 2D, exce$t that, in the ?iBHi$$arion,?NiB the smaller !igits are situate! farther bac%, an! are of smaller $ro$ortional siAe, than in the ?iBProtohi$$us'?NiB

The ulna is slightly more !istinct than in the horseM an! thehole length of it, as a very slen!er shaft, intimately unite!

ith the ra!ius, is com$letely traceable' The fibula a$$ears tobe in the same con!ition as in the horse' The teeth of the?iBHi$$arion?NiB are essentially similar to those of the horse,but the $attern of the grin!ers is in some res$ects a littlemore com$lex, an! there is a !e$ression on the face of the s%ullin front of the orbit, hich is not seen in existing horses'

+n the earlier 6iocene, an! $erha$s the later Eocene !e$osits of some $arts of Euro$e, another extinct animal has been!iscovere!, hich uvier, ho first !escribe! some fragments of it, consi!ere! to be a ?iBPalaeotherim'?NiB 0ut as further !iscoveries thre ne light u$on its structure, it as

recognise! as a !istinct genus, un!er the nameof ?iB5nchitherium'?NiB

+n its general characters, the s%eleton of ?iB5nchitherium?NiBis very similar to that of the horse' +n fact, Lartet an! )e0lainville calle! it ?iBPalXotherium euinum?NiB or ?iBhi$$oi!esM?NiB an! )e hristol, in 1O, sai! that it!iffere! from ?iBHi$$arion?NiB in little more than thecharacters of its teeth, an! gave it the name of ?iBHi$$aritherium'?NiB Each foot $ossesses three com$lete toesMhile the lateral toes are much larger in $ro$ortion to themi!!le toe than in ?iBHi$$arion,?NiB an! !oubtless reste! on the

groun! in or!inary locomotion'

The ulna is com$lete an! uite !istinct from the ra!ius, thoughfirmly unite! ith the latter' The fibula seems also to havebeen com$lete' +ts loer en!, though intimately unite! ith thatof the tibia, is clearly mar%e! off from the latter bone'

There are fortyFfour teeth' The incisors have no strong $it'The canines seem to have been ell !evelo$e! in both sexes'The first of the seven grin!ers, hich, as + have sai!, isfreuently absent, an!, hen it !oes exist, is small in thehorse, is a goo!FsiAe! an! $ermanent tooth, hile the grin!er

hich follos it is but little larger than the hin!er ones'The crons of the grin!ers are short, an! though the fun!amental$attern of the horseFtooth is !iscernible, the front an! bac%ri!ges are less curve!, the accessory $illars are anting, an!the valleys, much shalloer, are not fille! u$ ith cement'

even years ago, hen + ha$$ene! to be loo%ing critically intothe bearing of $alaentological facts u$on the !octrine of evolution, it a$$eare! to me that the ?iB5nchitherium,?NiB the?iBHi$$arion,?NiB an! the mo!ern horses, constitute a series inhich the mo!ifications of structure coinci!e ith the or!er of chronological occurrence, in the manner in hich they must

coinci!e, if the mo!ern horses really are the result of thegra!ual metamor$hosis, in the course of the Tertiary e$och, of aless s$ecialise! ancestral form' 5n! + foun! by corres$on!ence

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ith the late eminent -rench anatomist an! $alaeontologist,6' Lartet, that he ha! arrive! at the same conclusion from thesame !ata'

That the ?iB5nchitherium?NiB ty$e ha! become metamor$hose! intothe ?iBHi$$arion?NiB ty$e, an! the latter into the ?iBEuine?NiBty$e, in the course of that $erio! of time hich is re$resente!

by the latter half of the Tertiary !e$osits, seeme! to me to bethe only ex$lanation of the facts for hich there as even asha!o of $robability'?3B

5n!, hence, + have ever since hel! that these facts affor!evi!ence of the occurrence of evolution, hich, in the sensealrea!y !efine!, may be terme! !emonstrative'

5ll ho have occu$ie! themselves ith the structure of ?iB5nchitherium,?NiB from uvier onar!s, have ac%nole!ge! itsmany $oints of li%eness to a ellF%non genus of extinct Eocenemammals, ?iBPalaeotherium'?NiB +n!ee!, as e have seen, uvier

regar!e! his remains of ?iB5nchitherium?NiB as those of as$ecies of ?iBPalaeotherium'?NiB Hence, in attem$ting to tracethe $e!igree of the horse beyon! the 6iocene e$och an! the 5nchitheroi! form, + naturally sought among the various s$eciesof Palaeotheroi! animals for its nearest ally, an! + as le! toconclu!e that the ?iBPalaeotherium minus CPlagiolo$husD?NiBre$resente! the next ste$ more nearly than any form then %non'

+ thin% that this o$inion as fully justifiableM but the$rogress of investigation has thron an unex$ecte! light on theuestion, an! has brought us much nearer than coul! have beenantici$ate! to a %nole!ge of the true series of the $rogenitors

of the horse'

ou are all aare that, hen your country as first !iscovere!by Euro$eans, there ere no traces of the existence of the horsein any $art of the 5merican ontinent' The accounts of theconuest of 6exico !ell u$on the astonishment of the natives of that country hen they first became acuainte! ith thatastoun!ing $henomenonFFa man seate! u$on a horse'=evertheless, the investigations of 5merican geologists have$rove! that the remains of horses occur in the most su$erficial!e$osits of both =orth an! outh 5merica, just as they !o inEuro$e' Therefore, for some reason or otherFFno feasible

suggestion on that subject, so far as + %no, has been ma!eFFthehorse must have !ie! out on this continent at some $erio!$rece!ing the !iscovery of 5merica' <f late years there has been!iscovere! in your (estern Territories that marvellousaccumulation of !e$osits, a!mirably a!a$te! for the $reservationof organic remains, to hich + referre! the other evening, an!hich furnishes us ith a consecutive series of recor!s of thefauna of the ol!er half of the Tertiary e$och, for hich e haveno $arallel in Euro$e' They have yiel!e! fossils in an excellentstate of conservation an! in unexam$le! number an! variety'The researches of Lei!y an! others have shon that forms allie!to the ?iBHi$$arion?NiB an! the ?iB5nchitherium?NiB are to be

foun! among these remains' 0ut it is only recently that thea!mirably conceive! an! most thoroughly an! $atiently or%e!Foutinvestigations of Professor 6arsh have given us a just i!ea of

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the vast fossil ealth, an! of the scientific im$ortance, of these !e$osits' + have ha! the a!vantage of glancing over thecollections in ale 6useumM an! + can truly say that, so far asmy %nole!ge exten!s, there is no collection from any one regionan! series of strata com$arable, for extent, or for the careith hich the remains have been got together, or for their scientific im$ortance, to the series of fossils hich he has

!e$osite! there' This vast collection has yiel!e! evi!encebearing u$on the uestion of the $e!igree of the horse of themost stri%ing character' +t ten!s to sho that e must loo% to 5merica, rather than to Euro$e, for the original seat of theeuine seriesM an! that the archaic forms an! successivemo!ifications of the horses ancestry are far better $reserve!here than in Euro$e'

Professor 6arshs %in!ness has enable! me to $ut before you a!iagram, every figure in hich is an actual re$resentation of some s$ecimen hich is to be seen at ale at this $resent timeC-ig' 2D'

-ig' 2'

The succession of forms hich he has brought together carries usfrom the to$ to the bottom of the Tertiaries' -irstly, there isthe true horse' =ext e have the 5merican Pliocene form of thehorse C?iBPliohi$$us?NiBDM in the conformation of its limbs it$resents some very slight !eviations from the or!inary horse,an! the crons of the grin!ing teeth are shorter' Then comes the?iBProtohi$$us,?NiB hich re$resents the Euro$ean

?iBHi$$arion,?NiB having one large !igit an! to small ones oneach foot, an! the general characters of the foreFarm an! leg tohich + have referre!' 0ut it is more valuable than the Euro$ean?iBHi$$arion?NiB for the reason that it is !evoi! of some of the$eculiarities of that formFF$eculiarities hich ten! to shothat the Euro$ean ?iBHi$$arion?NiB is rather a member of acollateral branch, than a form in the !irect line of succession'=ext, in the bac%ar! or!er in time, is the ?iB6iohi$$us,?NiBhich corres$on!s $retty nearly ith the ?iB5nchitherium?NiB of Euro$e' +t $resents three com$lete toesFFone large me!ian an!to smaller lateral onesM an! there is a ru!iment of that !igit,hich ansers to the little finger of the human han!'

The Euro$ean recor! of the $e!igree of the horse sto$s hereMin the 5merican Tertiaries, on the contrary, the series of ancestral euine forms is continue! into the Eocene formations' 5n ol!er 6iocene form, terme! ?iB6esohi$$us,?NiB has three toesin front, ith a large s$lintFli%e ru!iment re$resenting thelittle fingerM an! three toes behin!' The ra!ius an! ulna, thetibia an! the fibula, are !istinct, an! the short crone! molar teeth are anchitherioi! in $attern'

0ut the most im$ortant !iscovery of all is the ?iB<rohi$$us,?NiBhich comes from the Eocene formation, an! is the ol!est member

of the euine series, as yet %non' Here e fin! four com$letetoes on the front limb, three toes on the hin! limb, a ellF!evelo$e! ulna, a ellF!evelo$e! fibula, an! shortFcrone!

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grin!ers of sim$le $attern'

Thus, than%s to these im$ortant researches, it has becomeevi!ent that, so far as our $resent %nole!ge exten!s, thehistory of the horseFty$e is exactly an! $recisely that hichcoul! have been $re!icte! from a %nole!ge of the $rinci$les of evolution' 5n! the %nole!ge e no $ossess justifies us

com$letely in the antici$ation, that hen the still loer Eocene!e$osits, an! those hich belong to the retaceous e$och, haveyiel!e! u$ their remains of ancestral euine animals, e shallfin!, first, a form ith four com$lete toes an! a ru!iment of the innermost or first !igit in front, ith, $robably, aru!iment of the fifth !igit in the hin! footM?B hile, in stillol!er forms, the series of the !igits ill be more an! morecom$lete, until e come to the fiveFtoe! animals, in hich, if the !octrine of evolution is ell foun!e!, the hole series musthave ta%en its origin'

That is hat + mean by !emonstrative evi!ence of evolution'

5n in!uctive hy$othesis is sai! to be !emonstrate! hen thefacts are shon to be in entire accor!ance ith it' +f that isnot scientific $roof, there are no merely in!uctive conclusionshich can be sai! to be $rove!' 5n! the !octrine of evolution,at the $resent time, rests u$on exactly as secure a foun!ationas the o$ernican theory of the motions of the heavenly bo!ies!i! at the time of its $romulgation' +ts logical basis is$recisely of the same characterFFthe coinci!ence of the observe!facts ith theoretical reuirements'

The only ay of esca$e, if it be a ay of esca$e, from theconclusions hich + have just in!icate!, is the su$$osition that

all these !ifferent euine forms have been create! se$arately atse$arate e$ochs of timeM an!, + re$eat, that of such anhy$othesis as this there neither is, nor can be, any scientificevi!enceM an!, assure!ly, so far as + %no, there is none hichis su$$orte!, or $reten!s to be su$$orte!, by evi!ence or authority of any other %in!' + can but thin% that the time illcome hen such suggestions as these, such obvious attem$ts toesca$e the force of !emonstration, ill be $ut u$on the samefooting as the su$$osition ma!e by some riters, ho are +believe not com$letely extinct at $resent, that fossils are meresimulacra, are no in!ications of the former existence of theanimals to hich they seem to belongM but that they are either

s$orts of nature, or s$ecial creations, inten!e!FFas + hear!suggeste! the other !ayFFto test our faith'

+n fact, the hole evi!ence is in favour of evolution, an! thereis none against it' 5n! + say this, although $erfectly ellaare of the seeming !ifficulties hich have been built u$ u$onhat a$$ears to the uninforme! to be a soli! foun!ation' + meetconstantly ith the argument that the !octrine of evolutioncannot be ell foun!e!, because it reuires the la$se of a veryvast $erio! of timeM hile the !uration of life u$on the earththus im$lie! is inconsistent ith the conclusions arrive! at bythe astronomer an! the $hysicist' + may venture to say that + am

familiar ith those conclusions, inasmuch as some years ago,hen Presi!ent of the Geological ociety of Lon!on, + too% theliberty of criticising them, an! of shoing in hat res$ects, as

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it a$$eare! to me, they lac%e! com$lete an! thorough!emonstration' 0ut, $utting that $oint asi!e, su$$ose that, asthe astronomers, or some of them, an! some $hysical$hiloso$hers, tell us, it is im$ossible that life coul! haveen!ure! u$on the earth for as long a $erio! as is reuire! bythe !octrine of evolutionFFsu$$osing that to be $rove!FF+ !esireto be informe!, hat is the foun!ation for the statement that

evolution !oes reuire so great a timeR The biologist %nosnothing hatever of the amount of time hich may be reuire! for the $rocess of evolution' +t is a matter of fact that the euineforms hich + have !escribe! to you occur, in the or!er state!,in the Tertiary formations' 0ut + have not the slightest meansof guessing hether it too% a million of years, or ten millions,or a hun!re! millions, or a thousan! millions of years, to giverise to that series of changes' 5 biologist has no means of arriving at any conclusion as to the amount of time hich may benee!e! for a certain uantity of organic change' He ta%es histime from the geologist' The geologist, consi!ering the rate athich !e$osits are forme! an! the rate at hich !enu!ation goes

on u$on the surface of the earth, arrives at more or less justifiable conclusions as to the time hich is reuire! for the!e$osit of a certain thic%ness of roc%sM an! if he tells me thatthe Tertiary formations reuire! 88,888,888 years for their !e$osit, + su$$ose he has goo! groun! for hat he says, an! +ta%e that as a measure of the !uration of the evolution of thehorse from the ?iB<rohi$$us?NiB u$ to its $resent con!ition' 5n!, if he is right, un!oubte!ly evolution is a very slo$rocess, an! reuires a great !eal of time' 0ut su$$ose, no,that an astronomer or a $hysicistFFfor instance, my frien! ir (illiam ThomsonFFtells me that my geological authority is uiterongM an! that he has eighty evi!ence to sho that life coul!

not $ossibly have existe! u$on the surface of the earth88,888,888 years ago, because the earth oul! have then beentoo hot to allo of life, my re$ly is4 "That is not my affairMsettle that ith the geologist, an! hen you have come to anagreement among yourselves + ill a!o$t your conclusion'"(e ta%e our time from the geologists an! $hysicistsM an! it ismonstrous that, having ta%en our time from the $hysical$hiloso$hers cloc%, the $hysical $hiloso$her shoul! turn roun!u$on us, an! say e are too fast or too slo' (hat e !esire to%no is, is it a fact that evolution too% $laceR 5s to theamount of time hich evolution may have occu$ie!, e are in thehan!s of the $hysicist an! the astronomer, hose business it is

to !eal ith those uestions'

+ have no, la!ies an! gentlemen, arrive! at the conclusion of the tas% hich + set before myself hen + un!ertoo% to !eliver these lectures' 6y $ur$ose has been, not to enable those amongyou ho have $ai! no attention to these subjects before, toleave this room in a con!ition to !eci!e u$on the vali!ity or the invali!ity of the hy$othesis of evolutionM but + have!esire! to $ut before you the $rinci$les u$on hich allhy$otheses res$ecting the history of =ature must be ju!ge!Man! furthermore, to ma%e a$$arent the nature of the evi!ence an!the amount of cogency hich is to be ex$ecte! an! may be

obtaine! from it' To this en!, + have not hesitate! to regar!you as genuine stu!ents an! $ersons !esirous of %noing thetruth' + have not shrun% from ta%ing you through long

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!iscussions, that + fear may have sometimes trie! your $atienceMan! + have inflicte! u$on you !etails hich ere in!is$ensable,but hich may ell have been earisome' 0ut + shall rejoiceFF+shall consi!er that + have !one you the greatest service hichit as in my $oer to !oFFif + have thus convince! you that thegreat uestion hich e have been !iscussing is not one to be!ealt ith by rhetorical flourishes, or by loose an! su$erficial

tal%M but that it reuires the %een attention of the traine!intellect an! the $atience of the accurate observer'

(hen + commence! this series of lectures, + !i! not thin% itnecessary to $reface them ith a $rologue, such as might beex$ecte! from a stranger an! a foreignerM for !uring my brief stay in your country, + have foun! it very har! to believe thata stranger coul! be $ossesse! of so many frien!s, an! almosthar!er that a foreigner coul! ex$ress himself in your languagein such a ay as to be, to all a$$earance, so rea!ilyintelligible' o far as + can ju!ge, that most intelligent, an!$erha$s, + may a!!, most singularly active an! enter$rising

bo!y, your $ress re$orters, !o not seem to have been !eterre! bymy accent from giving the fullest account of everything that +ha$$en to have sai!'

0ut the vessel in hich + ta%e my !e$arture toFmorro morning iseven no rea!y to sli$ her mooringsM + aa%e from my !elusionthat + am other than a stranger an! a foreigner' + am rea!y togo bac% to my $lace an! countryM but, before !oing so, let me,by ay of e$ilogue, ten!er to you my most hearty than%s for the%in! an! cor!ial rece$tion hich you have accor!e! to meMan! let me than% you still more for that hich is the greatestcom$liment hich can be affor!e! to any $erson in my $ositionFF

the continuous an! un!isturbe! attention hich you have bestoe!u$on the long argument hich + have ha! the honour to laybefore you'

-<<T=<TE

C1D The absence of any %eel on the breastFbone an! some other osteological $eculiarities, observe! by Professor 6arsh,hoever, suggest that ?iBHes$erornis?NiB may be a mo!ificationof a less s$ecialise! grou$ of bir!s than that to hich theseexisting auatic bir!s belong'

C7D 5 secon! s$ecimen, !iscovere! in 1O, an! at $resent in the0erlin museum, shos an excellently $reserve! s%ull ith teethMan! three !igits, all terminate! by clas, in the fore limb'1O23'

C3D+ use the or! "ty$e" because it is highly $robable that manyforms of ?iB5nchitheriumF?NiBli%e an! ?iBHi$$arionF?NiBli%eanimals existe! in the 6iocene an! Pliocene e$ochs, just as manys$ecies of the horse tribe exist no, an! it is highlyim$robable that the $articular s$ecies of ?iB5nchitherium?NiB or ?iBHi$$arion,?NiB hich ha$$en to have been !iscovere!, shoul!

be $recisely those hich have forme! $art of the !irect line of the horses $e!igree'

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CD ince this lecture as !elivere!, Professor 6arsh has!iscovere! a ne genus of euine mammals C?iBEohi$$us?NiBD fromthe loest Eocene !e$osits of the (est, hich corres$on!s verynearly to this !escri$tion'FF?iB5merican Sournal of cience,?NiB=ovember, 1O:'

En! of The Project Gutenberg Etext of Lectures on Evolution, by Huxley

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