cu .. P.X. 315

como widely divergent. E .... tinct forms arc f!Cidom dirc<:tly intcn ncdiato bctwC<!n existing fonns; but are ink'nn(!(liato only by n long and cin:uitous coutiiC through many extinct and w!ry different fon!U!. We can tlcnrly see why the Ol}."'mic remains of cloecly con· !le<'Uti,·e fonna.tions are more clOilely allif'd to each othf'r, than are tboeo of remote fom1ations; for the fonns nrc more ciOi!Cly linked together by gf'nemtion: wo ('ftn clearly 9ee why tho remains of an intenncdinte fonnntiou nrc intcnncdinto in dmmctcr.

'l'ho inhnbiUmt.s of cu.th successi\'e period in t]l(l

world's hktory have beaten their prcdc<!C8i!Ol'8 in the mce for life, and nrc, in 110 far, higher in tho l!(•nlo of nature; and this may Q('(.'()nnt for that ,·ague ye~ ilJ. dr>fin<'<i f!Cntimcnt, felt by many palreontolov;ii:ltll, that OrgRnisntion on the whole lll\s progreS\!6(1. li it should lu'renftcr be Jlro\'Cd that ancient animals resemble to a ec.rtnin extent tho cmbry011 of more recent 1mimnls of tho snmo cl.ass. tho fact will be intelligible. Tl1o 8\I(!('('Sfliou of t he !liltnO t)'l>CB of structure within tlu:­so.me arens duriug tho later b'COiogical]K'riods ccnac8 to be my~tcrions. and is simply <'Xplaincd by inheritnnC<!.

lf then tho geological reronl be as imperfC<'t ns I I.IE.'Iie,·o it to be, and it may at least be R88ertcd that tho reronl cannot be )ITO\'cd to be much more perfect, t ho main objections to tho theory of natural selection are greatly d iminished or disappear. On tho oth<'r hand, all the chief laws of po.la!ontol~ plainly Jll'O­claim, as it ~~eems to me, that spedes lul\·e ))e(>n pro­dur>c<l by onlinary gencrntion: old fonns ha\'ing be<>n rmpplnuted by new anrl imJlro,·ed forlllll of life, produced by tho lawa of variation still acting round us, and pre­f!C n ·cd by No.tuml Selection.

Q 3

3-Hl OEOOfl,\l'lllC.\L DlSTniDL"TIOS". CH,.P. XI.

CIL\P1'EH XJ.

GEOOR.O.PHIC~L IJIIITIIIBll'l'lON.

J'TC~totdi&tributioneannotbeaoco:mntedforbydilferenOI.'Iinphy· &kal oonditiona-lmportanoo o(barricn-Affinity of tl1c pro.­ductiollllo(tbe .. mooontineut-Ceutfl'llofcrcation-lleane of di~pcnal, by chaDJ:8 ofclimato and of the lnel of the land, •nJ by OOOQion•l mean•- Di•t~l during the Olacialperkd oo-eltenai>·e..,·itbtllfl"1ll'ld.

b ronsidering the tlist.ribution of organic beings o,·cr tho> face of tl1e globe, the first great fllCt which strik{'B 11.~ i.~, thnt neitlu•r the similarity nor the dissimilarity of the inlmbitnnU of ,·arious regions ean be fl('("'unted for loy their climntnl and other pl1ysicnl conditionll. Of late, almost m·{'ry author who hns studied the subject hns oomo to this C.'Ondtl::!ion. 1'ho caSe of Americu alone would almost suffice to pro,·e its truth: for if we (•!dude tho northern pnrU where the cireuntjJOlar lnnd is almost oontinuous, all Ruthol'l! agree thnt one of the most fundnmcntnl divisions in geogro.phicnl distribution is that between the New and Old Worlds; yet if we trawl O\'er the l'fl!~t American oontincnt, from t.he centrnl po.rts of the United States to its extreme I!Outhenl ]JOint, we meet with the most di,·ersified con· ditions; the mOilt humid districts, arid deserts, lofty mountains, gmssy plains, forests, Jnaf'li!hes, IRkcs, nnd grcnt riYers, under nlmOflt eYcry tempera.tnre. 1'hcro is hardly a. elimRte or condition in the Old World wh.ieh c.'llnnot be pnralleled in the Xew-nt lenat u.s closely ns tho snme B])('(!ica generolly reqttire; for it is t\ m011t rare case to fiud n group of organisms confined to any smRII spot., luwing conditions peculiar in only a &light

Th lin

GEOGIL\l'lliCAL DISTIIIDCTIOX. 3 17

dcgrN>; for instnnC<', smnll UI"{'M in tho Old World {'Ou!d 00 pointed out hotter thnn any in tl•o Nl'w World, yet these nrc not inhabit('() by a peculiar fauna or flora. XotwithstRmling tl•is JlflmUclism in tho con­ditions of the Old and :\ew Worlds, l10w widcly differ­ent are their li\·ing productions!

Jn the sont\l('rn hcmisphcl"(', if we compare lnrgo tl"fLtt.s of lund in Anstrnlin, South AfriCfl. nnd W('Stcrn ~uth A.m{'riCfl, between lntitudCII 2.i0 nnd 3J·, we s:hnll find Jlftrlil extn:mcly similar in aU their condi t ion!', yct it would not be JJOt;,;.ible to JlOint out three fuum115 nnd flonu more utterly di:;.;imilnr. Or n~"'l.in we mny com­p.uo tho )JI"OI.luctions of South America south of Jut. ;;1,)0 with those north of 2J0

, which ro•l.&.'<)uently inhabit a coll.i!idernbly different climate, nnd they will be found inromp!lrnbly more clotocly rclatcd to ('O.Ch oth{'r, than th('y Are to tho pnxluctious of A u~tmliR or Africa und{'r nenrly the snmo climate. Annlogous facti! could bo ~i,•en with re~peet to the inhnbitRnts of the sen.

A II('('Ond great fo.ct which strikNI us in our gcncrnl nn·i,..w is, that barri{'r!J of any kind, or obtstneiCII to fT"I'e migmtion, o.re relnt('() in a cl0116 nnd importunt JMWII'r to the differences loetween the prodnctiolll! of mrions regions. We sec thi~ in the great difference of nenrly n\1 the terrcstri;1l Jlrodnctions of the :Kew and Old World.~ e.xcepting in the northem )XIrt.s, whcl'(' thc lnml almost joins, and where, under a slightly differi'nt climate, there might hal"e been frro w.igmtion for the northern tempemto fonns, ~ th<"re now is for the ~t ri<" tly nri'tic Jl rodu<"tions. We sec tl•e same fi1<"t in tho great difference between tho inhnbitnnts of Ans­tnlliu, LVrica. nnd South Amcriffi under the sanK' Inti­tuM: for theeo oountriefl are almost ns much i,Jo\ntrd from eneh oth<"r nil ill possible. On {'tiCh ctmtineut, a\110, we sec tho f!Rmo fuct; for on thl' O)lpori te Bi(\cs of

318 GEOORAPHIC.\L OLSTRI8L'TIO~. CII4P. :0.:1.

lofty anJ rontinu.-.us mouutain-nu~ and of great d•'!ll·rb, llll<l l!<>mo•tim('ll ewn of large riwno., \\C find diffi•n·nt prodnctioll.il; though u nJOuntilin-d~&inR. dP,.....rta, &., are not as imr•-U•, or lik~l~· to haw endun'il ao long ru1 tho oceans IM'Jlftmtiug: <'ontin<"nt~. the dill'eren("('B are very inferior in do•grce to tl101!C clm­nwtcristic ofdistinctoontinN•i.l<.

'l'uming to the sea, we find tho 81lmo law. Ko two marin" fmmru aro more ditttinct, with lmnlly a fi.,;h, sho·ll, or cmb in oontnJOU. than thoec of the eeat<'m and lH ... tf'rn .i!hOn'll of South and Central America; ret th.-~ great fnunaa are fM'J)flnlot{'d only L~· the narrow, hut iUIJifL!<'!able, ibthnlllll or Panama. We.twanl or the ~hnf'('tl of .\m<'rim, a llidl• 8))8('(' of O)X'Il OC't'B.n utendi!, with Ml an i:Jand 811 a halting:·tliart> for NnigranUI ; lwn• we luwe a bo.rrio·r of &.noth{'r kilt~\, and M IJOOn ns thi~ i8 J~~Uo.~ wo llle<'t in tho e~U:~tenl i~laud~ of the l'owifk, with another and totnlly di~tinet finmn. So thnt h"re thrro mnrine fnunl\8 rnnf;(' far northwnnlnnd t~outlnrnnl, in Jlftmllel Iin('ft 110t fur from each olll<'r, und"r corre"1JOnding dima!t.•11; hnt from being lie)Jft·

rnt•·•l from (·och oth{'r by iiUJlt'·'"*'ble barriers, eitl1er of land. or O)IE'Il I!C&, th<'y at(' ··holly di...tinct. On the otlwr !Ulnd, proce«ling 11till furtbf'r we~twanl from the ('Mt•·m i:;landi! of the tropical , .. ru of tilt' Pacifi<', we <'ll("())lllt('r no imJl&i!S8ble barrif.rs, and. we l~&t'e innu­m('mbl<' i.!land!l 811 halting·)J!acet~, until nfter tra\·elling m·<'r a h('mi.~phcro we rome to tho shon>ll of Africa; nnd owr thiB ,.W!t IIJ)A{'(l we mrct with no well-ddined ami di~tinl't. marino faunas. Although lmnlly one ahell, cn\b or fish ill common to the abcwe--nnmed thn>e approximate faunas of .Eastcn1 and We~tcn1 Amerit'll and the e1111teru Pacific Wand4, yet 1u.nny fish muge from the Pa<'ific into the ludian Ocean. and many ~belli are common to the cutem islaud.s of the l)acific

n~e -:.omolete Wort<,. o f Char1 Qarw.Ll Onlloe

OEOGII.\PUICAL DISTIIIBL'TION. 3-19

and tho castcn1 shores of Africa, on almo<tt cxnetlv opposil<'mcridian.l!of longitude. ·

A thin! l,rr-Mt r.~t. ptu1.ly included in tl1o foregoi ng stnt.-.mcnl~, is tho n!linity of tho productions of tl1e snme continent or sen, though tho specirs t hemsehcs nro distinrt at different points and stations. It is n law of tho widest genernlity, nnd e,·ery continent offel"j innumernble instances. New•rthrle81:1 the nntu­mlist in tl'lwclling, for instance, from nort h to f!Outh nr,·er r~•ils to be stn1rk bv the mnnn('r in whirh ~uc­re~~ i ,·c b"'''illl8 of beings, ~ifirnlly di.;tinct, yet clearly rclllted, rcplnro each other. H e h('al'8 from doedy Rlli••d, vet distinct kin<b! or bird!!, 110tee II('Srh· s.imilar, aud ~.s thrir ueets s.imilnrly OOll81tU('I<'d, bnt ~JOt quite alike, with e{;!,'tl ooloured in nearly tho same mnnner. Tlw plnins near tho Stmit.s or Ungdlnn are inhabited by ono species of llhea (American oetrieh), and north· wan! the plains of La Plata by another speeica of the Mmo genua; nnd not by a tnte ostrirh or emeu, like t hoso found in Mrica and Austmlin umlf'r tho same latitude. On tlJCSO llllme plnins of La 1-'lntn, wo sco tho agouti and bizcachn, animals having nrarly the same 1111bits 1111 our hares and ro.bbits and belonging to th11 snmc onl•'r or Rodents, but tl1ry plainly di'lplay an Amcrienn typo of structure. Wo /lll('('nd the lofty JX"ak:! of tho Conlillero aud we find nu alpine 8!Jeeies of bizcaelm; we look to the wate111, and wo do not find tho beaY('r or musk-mt, but the ooypn and eapylmm, rodents of tho American type. Innumeroblo other in­shmees could be gh·en. If wo look to the i.•lnruls oil' the American ahorc, howeyer much they may diiJCr in grological structure, the inhahitnnt.s, though tl1cy may bo all JX'<.'nliar apocies, are eBSCntially A111criean. We may look OOek to pnst ages, aa sho"·n in t he l1111 t chapter, and we find .\.mericnn l)1X"' then )lteYalcut on

350 GEOOIIAPHIC,\L DISTUIDUTIO!I.

the American continent and in the American SCil1:'.

We see in tl1csc facts some deep organic bond, prevail­ing tllrongl1ont space ami tlme, OW;!r the same nn:M of land and water, and independent of their physical con­ditions. The naturalist must feel little curiosity, wl10 is not led to inquire what this bond is.

~fhis bond, on my theory, is simply inheril:fLncc, that cause whicl1 alone, as far as we positi1·ely know, JlTO-­

duces organisms quite like, or, as we see in the case of mricties nearly like each other. The dissimilarity of the inhabitants of different regions may be attributed to modification through natuml selection, and in n quite subor(linate degree to tho direct influence of dif'l'erent phy~ical conditions. The degree of dissimilarity will de­pend on the migmtion of tho more dominant fonns of life from one region into another having been cfl'eeted with more or less ease, at periods more or less remote ;-on tl10 uature 1111d number of tho fonner immigrants;­nnd on tl1eir netion nnd reaction, in their mutual stn1ggles for life ;-the relation of organism to organism being, illl llun·o alrendy often remarked, the most im­portant of all relations. 'l'hu.s the high importance of barriers comes into play by checking mi!,'l'Ution; as does time for the slow process of modification through natnrol selection. \ridcly-mnging species, aboumliug in indi\·iduals, which have already trinmplwd over many competitors in their own widely-extended homes will have the best chance of seizing on new places, when tl1ey sprend into new countries. b1 their new homes tl1ey will be exposed to new conditions, and will frequently undergo further modification and impro\·emcnt; and thus they will become still further yietorious, and will prodtu..-e group!! of modified descendants. On this prin­citJle of inheritance with modification, we can under­stand how it is that scetions of genera, whole genera,

I W rk f s rwin nli

C11u. XI. SISGU: CE:!<.IRES OF Clt£.\TIOS. 3.31

nnd {'\'l'll fttmiliCII aro ronfincd to the Sttme area.q. lUI iB 1:10 oonuuonly and notoriou.4f the ('tlll('.

l lx>li(•\"{', as "1UI remarked in the last chapter, in no l•lw of nt'C'Ceso.ry de,·elopment. As the nu-inloility of f'arh l!JJt'('ies is an indcpend<'nt proprrty, nnd will be taken ndmntng..' of by nntnral !!election, only 50 farM it pro!llil the indi"idlllll in ita romplcx struggle for ljf,,, 110 the d<'~rre of modifiC'fltion iu different speci<'e will Jx. no unifvnn quantity. lf, for in~;tnn(•e, n mnnlx>r of ~X'Cie"- whi1•h l!tand in dif'('Ct t'Ompetition with ('il('h

othf'r, mip'atO i11 n body into a 1\f'W a111l al'tf'rwnnls bolat('() oountn"; thq· will be little liable to modifirn­tiou; for llf'ith~r mii'ratiou nor il!Olntiou in t\l(·m.-·l'l'es eon do anything. 'l'll<'&' principl(•e rome into Jlln~· on.l~· by brin~ing orgnnis.ms into new relntionl! with Nwh othl'r, and in a k~r degree with the l!nrrounding Jlhy .. ienl oon­dition~. As we ha,·o !!CCII in the laat dliiJller that 110n1o form!J hn,·e retained nenrly the s.une clmnlcler from an ('normon~ly remote grological period, 80 ccrtnin ~JI('{'ics haw mig-rotetl on•r ,·nst spo.Cft!, And ha,·e not beeom<' grratly modifl('(i.

On IIM·'!C ,·iews, it iB ob\'iol.l8, that thl'l ll<'wrol ~J)('('iCR of the ~~t~me Rt'IIU8, though inhabiting d~e mo.;t di...tant quartl'l"ll of the world, mu,;t originally han• prof'(•eded from l11e 81\me I!()UI'('(', as 1i1ev hn\·e df'I!N'nded from the f<On1e p~nitor. l n thf' ~"<' of th0110 ~i<'!'l, wlii<'h b ... we undergone during whole ~log-i<'ol JX'riods but !itt if' modiflention, th<'~ is not mud1 di.ffieulty in Ll'lic\·­ing tlmt they IliA~· ha,·e migrote<l from the Mill<' ro.'gion; for 1luring tho ''liSt gcogrnphiell l nml ('\ im11tul clmngcs whi('\o wi ll hM·e BIIJ)('rvenNi sine(l nneit•nt tim<'~ almost any amount of migration iB Jl{lf<,;il>l<'. But in mtmy other CM('", in whieh we hav(' n:'fl..oon to belie,·(' thnt the IIJleei<'s of a ~·nus hn,·c hN-n produeed within OOIII ))BNiti,·ely I"C('('Ilt tim('l!., there i.! great difficulty on thi~ }}('ad. It

£.... ~ c...,molete Work of ~harles Darwon

:h)2 GEOOIL\1'111CAL DISTntBl:TION.

is nlso ob,·io11..~ that the indh·idnalil of tho snme 8J.lE'Cie!l,. tl1ongh now inhabiting di.!tant and isolated n>gions, mllllt haw Jl~M from one !<pot, where tht> ir parents were first JH·oduccd: for, as explain('(! in the IIU!t chapter, it is inel\'<liLlc that indi\·idunls idcntie111ly the Mme should C\'Cr luwo ])e{>n ]Jroduced through n11hunl selection from

pnronts spccifirolly distinct. We nro thus brought to tho quc&tion which has been

lnrgdy discll.'!l!ed by natu.mlists. nnmcly, whether species June Lccn created at one or more point-'1 or the earth's surraec. Undoubtedly there are ,-cry many cases of extreme difficulty, in undell:llnnding how the Slime S]Je­

cif's oould Jl088ibly haYe migrated rrom. aome one point to the sen:rul distant and i80lllt(!(l points, where now found. Xe,·ertheleSil the simplicity of tl1e virw that each species wna first produC(-'(] within a single region ct~ptinJt('S the mind. lie who rojC'Cta it, l'l"jccts the wra car11a of ordinary gcnemtiou with subeequcnt mi· gmtion, 11nd calla in the t~gi-'ney of a mimclc. It is univ('rSitlly admitted, that in moet CiU1es tho area in­hnbited by a SJM!eies is continuous; and wl1en a Jllant or auim11l inhnbits two pointa IJO di~taut from each other, or with an inten·al of llliCh a lliitnre, th.nt the llpROO oould not be eD.8ily pMeed o,·cr by ntigration, the fact ill f.,-iWm 8.8 aomething remarkable nnd exCE'ptiounl. '!'he C11pncity of migrating aci"Ot!8 thf' l!Cn is more dis­tinetly limited in terrestrial mnmmnl~ thnu perhaps in nny otl1er organic beings; nnd, neoordinp:ly. we find no inexplienble CaBell of the samo mnmmnl inhubiting dis­tant points of the world. No gwlogist will fed any difliculty in such CIIJles ns Gre11t l3ritain hnving been fonnerly united to Europe, and consequently po&!CSSing the l!fllliO quadrupeds. But if tho Mmo species can be produced nt two separate ]JOints, why do wo not find a single mal1llll8! oommon to Euro]l-'0 and Aus­tralia or South America? The conditions or lifo nre

Cn1o~. XI. ~IXGLF. CE:."TilES OF CREATIOX. 3J3

nNnly the same, so that n multitude ofEuropean animals and plantll hn,·c become n11tnmlised in AmeriPn and Austmlin; and some of the aOOriginalJllnntilnro identi­cally tl1o snme at these distant points of tl1o northern and eouthem hemisphere&! 'l11e Rnswer, 1\8 1 belien•, i3, that mammals ha\·e not been able to migmte, whereas eome tJlants,from their \"aried mell.1l!lofd.isJM.'I'Sill,lm'·o migmted across the n'st and broken interspace. 'l'lm grt'M and striking influence which bnrriera of every kind have had on distribution, is intelligible only on tho ,·icw thnt tho grt'nt mfljority of SJ)I'!Cies htne been produced on one sidr nlouo, and hare not been able to mig-rotc to tho other si1\e. Some few families, many sub-fn.miliel!', wry many genem, and a still greater number of IJCC·

lions of g.:-nera arc confined to a l!iugle region; and it hae been obaerved by 1!6\·cral u.a.tumlists, that tho mOilt Mlnml g.:-ncra, or th010 b<Cncm in which the species aro most cl06<'1y related to each other, are gcncrn.lly local, or confined to one llrt'll. \\'hat a strn.nge anomaly it would be, if, whe11 coming one step lower in the IM.'ries. to the indi,·iduals of the llfUIIC species, fl. dii'(>Ct]y OllJIO­site nile llrt'mile<l; and SJ)('('iCII were not local, but had been Jlrodueed in two or more 1listinct aretiJS!

H en('(! it !IC<'IDS to me, 1\8 it bas to many other nntu­rn.li~>ts, tlmt the ,·iew or each speeies haring lleen llTO­duc('d in one nrea nlonc, nnd Jun·ing subsequently mi· gr;tted from thnt arcn all for ae its powcra of migmtion and subl'li>:~tcnoo undrr ]Wt rmd pll'sent condit ions pcr­mitkd, is thl' m011t 11robahl('. Undoubtedly mnny cases occur, in wh.il'h we cannot t·J:I>lnin how the snme !IJ"I('("iee ooultl luwe p!L'3Sed from one point to the other. But the ~"l'Rph.ical and dimntnl ehnn~-es, which lml·e cer­tainly occurred within n'('Cnt grologicnl tirne~~t must lm\'(' intCTTU]Jtcd or ll'nd('Tt'd discontinuo\19 tho for­merly rontinnous mnWJ of mnny species. So tl1nt we nre reduced to consider whether the exceptions to

if) The. Comolete..Wuri...:>f Charles Darwr. Onlin~!>

3,)-J GEOGnAPlllCAL DlSTnim;TIOX.

continuity of nmge nre so numerous nud of so gmve a nnture, thnt we ought to giYe 11p tl1e belief, rendered probable hy geneml oon~idcmtions, that each species has been produced within one flren, find has migmted theni.'C as fflr ns it could. It would be hopelessly tediOIIS to discuss fill tho exceptionnl eiiSC!I of the sumo species, now living at distflnt and sepnmtcd poiuts; nor do I for a moment pretend that nuy explnnfltion oould be ofl'en'd of many such eases. But after some preliminary remarks, I will discuss o. few of the moat striking classes of facta; nnmely, the existence of the sumo species on the summits of distant mountain-ranges, and o.t distnnt points in the arctic and antnretic regions; an{\ scooudly (in the following chapter) , the wide distribution offresll· wat;;or productions; nnd thirdly, the occurrence of the sumo terrestrial species on islnnds and on tl1e maiulnnd, though scpamted by humlreds of mii('S of open sco.. If the exi~tenoo of the Slime speci;;oa at distant and isolated pointa of the earth's ~mrfnce, can in many instances bo explained on tho ,-iew of ei\Ch species luwing migmted from o. single birthplaoo; th('n, considering our ignor­nnce with respect to former clUnntal and geogmphir:al chanfies and Yarious OI.'CMionalmellnS of tnmsport, the belief thnt this haa been the 1miversnllnw, seems to me inoompnrebly the safest..

h <liscus.;ing this subject, we slmll be enabled nt the same time to colll!ider 11 }Xlint equally im}Xlrttmt for u;o, namely, whether the severe! distinct species of a genus, wllich on my theory ho.ve all descended from a common pi'Og';;-Jtitor, can have migmted (undergoing modificntion during some pmt of their migmtion) from the area inhabited by their progenitor. If it cnn bo shol•'n to be nlmost invariably the <:use, that a region, of which lllOii!t of its inhabitants ure closely related to, or bcloug to tile same gencm with the speeies of a seoond region,

Rl The Complete Work of Charle~ Darwin OnPne

~ISot.E CE~"TnES OP CREATIO~. 3J5

has probably re«>i\·cd at 110me fonner period immi~uts from thi~J othrr region, my tl1eory v.-illlx> strengthen•'<~; for we r~m dearly understand, on the principle of modifieation, why the inhabitants of a region ~hou.ld 00 related to thoee of another rcgion, whcnec it has been stocked. A \'Oicauie islnnd, for insllln~, lljlhean~d ond fornl<'d nt the tlistmu.·o of a few lmndrc,Jg of miles from a rontinrnt, would Jlrobably rreei"e from it in tho ('()urse of time n ft•w rolonistR, and their d{'!!('('ndant.<l, though modifit>o:l, would still be Jllninly related by inlu•ritnnee to tho in.habitantil of tho continent. C'n&t•s of thhl nature are rommon, 11nrl are, ns we shall b('rt'nftt>r morc fully Be(', in<':rplicnblc on the throry of ind('pell(\(·nt crrntion. This ,.j{'w of tho relation of ~<peei~ in one n>gion to tllOS(' in another, doe3 110t differ much (by subl!titutin~ til{' won! mriety for SJ:.NiC!!) from tlmt lately tuh-anccd in fin iug<>uious pnpcr by Mr. Walln('(', in which he con· dud,·~ thnt "C\'Cry species lUIS como into existence coincidrnt both in spuoo and time with n pre"<'xi~ting closely n!li('d species." And 1 now kuow from corre· 11pondcnC<', thflt this coincidence he nltrilmtca to gene­ration with modifiC'fltion.

'll1e prc,·ionll remarks on "single and miJhiple e<>ntres of Cl'('ation" do not directly bear on anoth,...r allied qut'!!tion.-Mmely whether all the iudil'idual.s of the lllllllO llj){'('i<'S lm\'O deaccndcd from a sin~!(' poir, or single )l{'nunphrodite, or whether, aa fiOmo authors ~UJlj)()!;l(', from mnny indh·iduul.s lrimultaueou.>ly Cl'('nted. With thOIIC organic being!! whieh 11('\'Cr infN'('l'OSII (if such rxi~t), tho speei,...s, on my theory, must Jun-e de-­!ll.'endf'll from a 81\('ccssion of improv('(\ varirti('!l, wl1ich wi\lncn•r hfi\'O Llendcd with other individlllllil or \RTi<'­ti e~. Lut will hnw auppluntcd cach otll<'r; so thnt, ntcoeh Bll('('('&;i\'e ~tngo of modification and improl'('ment., oil the imli\'iduals of eoch ,·ariety will haxo d(•>IC(·nded from

3.)6 GEOOP.APIIICAL DISTII!DUTIOS.

o. single parent. But in the majority of ensc~. namely, witl1 all orgallisms which hnbitw11ly Wlite for each birth, or which often intercross, I belic\·o that during tho slow process ofmodificution tho individuals of the species will lun·e been kept nearly uniform by intercrossing; so that many indi,•iduala will luwe gone on simultaneously changing, and the whole amount of modification will not hAve been due, at ench stage, to descent from a single parent. 'l'o illustmte what I mean: our English mee· horses differ slightly from the horses of e\'Cry other breed; but they do not owe their di!Tereuco and supe· riority to descent from any single pair, but to contiJJued care in selecting and training many indi\·idnala during many genemtions.

lkforo discussing the three classes of facts, which I hal'c selected as presenting tho greatest amount of difficulty on tho theory of" single cent res of creation," I must say a few words on the menus of dispersaL

Mean.1 of Ditper~al.-Sir C. Lyell and other authors have ably treated tl1is subject. I can give here only tho bri('fcst nbstmct of tho more importnnt facts. Change of climate must have bad o. powerful influenoo on migmtion: a region when its climate WIUI different may lnwe been a high rood for migmlion, but JIOW be impassable; I shall, howowr, presently \un-o to {liscuss this brnneh of the subject in some detail. Chll.ngcs of le,·el in tho land must also ha\'e been l1ighly inllu­entinl: a narrow isthmus now separates two marine fuuMs; submerge it, or let it fonnerly have been sub­merged, and the two faunas will now blend or may formerly have blende<i; where the sea now extends, land may at a fonner period ha,•o connected is\anW. or possibly even continents together, and thus huvo allowed terrestrial productions to pass from one to the other.

dh f h rl ~ lin

l!E.~:SS OF DlBI'EIISAL. 3Jj

Xo geologiet will dlilpute that great mutations of )('W~I. have OC<!Um..><l within the period of existing organisms. ]~dward Forbes insi~ted that all the ialand.s in tl1e Atlantic must recently have been connected "ith Europe or Africa, and Europe likewi110 with America Other anthon ha\'C thus hypotheti('Hlly bridged over every ocean, und l1twe united almost ew•ry i~llmd to somo mninluii(L 1 f indeed the urgumcnts used by PorlX'fl nro to 00 trusted, it must be ftdmitt;xl that IIC8.1'C<'Iy n single island exist& which hRB not n_'('('ntly been unit('(} to aomo continent. 'fhie ,-iew cuts thl' Gordian knot of the dis)X'rsal. of the- same ~pecii'S to til(' mOilt (litstant poin~ nnd rernoves many n diOiculty: but to the beet of my judgment we are not authoriU>d in admitting such cnomJOus geographical dumgcs within thf' period of ('Xisting species. lt seems to JU<l thnt we ha,-e abundant C\'idence of great oscillations of lncl in our continents; but not of such \'llilt chAnges in their position nnd utension, fUI to luwe unit('(! them within the recen t pt'riod to eiiCh other and to the sovcrol inter­\·ening oecilnic islands. I freely ndmit the fonn('r ex:­i,tence of many itslnnds, now burie·d h<'nMth th(' 8Cft,

which mny hn\"C sen·ed as halting places for lllnnts nnd for runny JlnimalJJ during the-ir migration. Jn the coral-producing ocea•m such sunken i~Jnmls llr(' now mark('(~ 1111 J belie,·e, Ly rings of corn! or nto!IJJ standing o\·er them. Whcnen!r it til fully admit!<'<~ as l believe it will aome day be, that each BJ)(!('ies lms pro«•eded from n single birthplace, ami wheu in tho eonrsc of time we kno11· lJOmcthing definite about the means of dis­tribution, we shall he ('nnbled to speculnte with llC<'Ilrity on tl1o fonncr extension of the J.md. llut J do not belic,·e that it will ewr he pron~l tlmt within the J'('CCIII period cont inents which nrc now quite IK•J)flrnte, have ~n continuously, or nlm08t eontinuetUily, united

The Com.clete Work of Ch· Jes Darwin Online

3.)8 GEOOIL\PlliCAL OISTRIBL"TIOS.

with each other, nnd with the many exi~ting <JoCennic i~l nnds. Re\·crnl fucts iu ili>~tribution,-snch na the gn.'at difrereuoo iu the marine faunas on the opp06ite sidPs of alm06t c,·cry contincut,-the cloee relation of th" tcrtinrv inhabitant!! of sovernllands and cHm seas to their pn>srnt inhabitantil,-ll. ~rtnin degree of relation (as we ~\mil lwreo.fier !!00) between the distribution of mammals and tho depth of the BCa,-theso and oth"r such facts 8(l('lll to me oppot;o..'<l to the admiiiilion of such Jm:xligious b"C<lS'"'Phieal re\·olutions within the l'CC('Ut

period, as are uooes;;:itated on the view admnccd by l•'orbcs and admitted by his many follo"·ers. 'l'he nature and re lnti\'c proportions of tho inhabitants of oeeanic i:dands likewise !lOOm to me oppoecd to the lx-lief of tll(·ir former eontinuity with coutin"nts. X or does theiralm~t.lminrsally \"Oioouie OODIJlOI!itiou fnwur the admi!<~iun that thry nrc the wl'("ck8 of sunken continent" ;-if tliey had originally existed ns moun­tnin-rang<>s on the land, i!Ome at least of the i~laucb

would hnve ~~~ formed, like other mouutain-fiiWuniU, of granite, metamorphic .khista, old fOSOiiliferous or other sul·h rocb, U!i!tead of con~;.isting of mere piles of,·olcnnic mutter.

I mllllt now My a fow won:k on whnt urc enlled ueei­dcnt.nl mean11, but which more properly mip::ht be culled ()('('ll:;ional metuUI of distribution. I simi! hf'rf' confine my:;clf to Jllanta. 1n botanical works, thitl or that plant is stntf'<l to be ill adapted for wide dis.it:minatiou; but for trimsport ll.('r()lj8 the BCn, tho g-reater or lc!lll facilitie~ Jun.y bo f!nifl to 00 almost who!Jy unknown. U uti! J trie<~ with i\lr. Berkeley'& ttid, t\ few cxperimcnta, it was not e,·en known how far f!Ce<k could re~ist the inju­riOIL':I action of BCa-wnter. To my I!Urpri.,;c I fo1md that out of 87 kind.i, G4 gcnninntcd 11fter nn immersiou of 28 days, 11nd o. few sur\'i,•cd o.n immersion of 137 days.

~ Jhj: Comole.te Work of~' Darw1n .&no!!

~IEA!i8 OF DlSI'Eill!AL. 3;)[1

For convrnicnce f!flke I chiclly tried small seeds. without tho eupsule or fn1it; and 118 all of these ~m.nk in 11 few dnya, they could not Ue floated rrcross wide SJ:wtees of tho_ sen, whether or not they were injured by the salt-water. Aftenmrds I tried some larger fn1it.s, eapmlles, &c., and some of these Hooted for a long time. It is well know11 what n dillCrcnco thoro is in tho lmoyaney of grocn and BCIISOncd timber; nnd i~ occurred to me that fl.ood.s might wash down plants or branches, uncl thnt thC'se might be dried on the lmnks, and tlwn br a fresh riso in tho stream 00 washed into the sen. lienee I W!Ul Jed to dry stems nnd branches of !H plants with ripe rruit, and to place them on sea wuter. 'fhe majority Slink quickJy, but SOOlO which whilst green Hooted for n very short time, when dried flootcd much longer; for intltance, ripe har.el-nuts sank immcd.iatelr, but when clricd, they flooted for 00 days and afterwards when plll.ntcd thor gcnninuted; nn nspnragus plnnt with ripe Uenics ftorrt.cd for 23 dnys, when dried it, floal.ed for S5 days, nud the seeds nftcrward;; germi­nated: tho ri1X! seeds ofJTclosciudium &"Ink in two dnys, when dried they floated for nbo1·c 90 dnys, nnd after­wnnls gcrminuted. Altogether out of the 9·! dried plants, 18 floated for e..boYe 28 days, and EIOIIlO of tl10 18 floated for a 1·ery much longer period. So thnt us i} f!C'Nls genninuted u.ftc1· nn immen~ion of 28 tlays; nnd ns ~: plnnlil with ripe fruit (but. not all tl1o Slime species ns in the forebtOing e..·~"(X!riment) floated, after being dried, for obo•e 28 duys, n.s fnr lUI we llliiY infer anything from tlwse scanty f(l.Cts, we mar conclude that tho sce<ls of fv~u plant.~ of uny country might 00 flontetl by scu.-cul·­rcnts d11ring 28 <h1~·s, and would retain tl1cir power of g.:-nnillfl.tion. lnJohnston'sl'hysicalAtlas, the lll"Cnlg(l

rute of the SCI'eral Atluntic CUIT('IIts is 33 miles per diem (some currents ruwdug at the rate of GO miles

300 OEOORAPIIICAL OISTRIDt."'TJO)I".

p('r diem); ou this 1wemge, the ~!Cedi! of .. Mii plants IJelouging to one rountry might be Rooted across 92 I miles of i!Ca to auothc-r country; and when stranded, if blown to a fa\-01111\ble spot by an inlaml f:,'tl.le, they would f:,~nninat('.

8ubecqncntly to my l'xperim('uts, :M. Marten& tried l!imilar OJK'll, but iu a much better mllnn('r, for ho placed t}}() &ee~:la in 11 box in the actual 8l·a, 80 that th('y were altemately wet •nd exposed to the air like really !looting Jllnnta. He tried 98 seMs, mostly different from mine; but he ehose m11ny large fnLits 11nd likewi010 eee<ls from plants whicll Ji,·o near tho sen; and this wo1t1d lun·e famnred the 11.\·ertlh"' length of tl1eir flota· tion and of tlu!.ir rt"ffi.ltaul'e to the injuriona action of the ~~alt.-water. On the other hand 1}() di<'l not pw,·iously dry the plimta or Lmn ... hca with the fruit; and this, aa we lun·e seen, would ll•t,·c cau>!('(l110me of th('m to ll.llxc lloo.trd much lonf.,'\'r. 'fhe l'('!lll\t waa tlmt U of hill BOC<Li fl011tcd for ·12 days, and were t]I('JI C•lpaLlo of gcr· mination. But J do not doubt that Jllanta exposed to the wf\n•s would flont for a )('88 time than tllO!Ie pro­te<"tcd from ,-iolent mowment ft!l in our experiments. 'fhrrefore it wm1M JICrhaps be safer to a.M\une that the t~o'Cds of about n.,n0 planl-8 of a 11om, arter having bef.n dried. rould be £looted ael'OM a ll(lROO of tll·a {)()() ntlles in wi1ltiJ, and would th('n ge-nninate. The fnct of the i11rg<>r fmil;! often flontiu~ longer th11n tho 11mall, is in· t('resting; ft!l Jllnnta with huge IJ(!('(li! or fmit <.'Oilld hardly be trnnsporW by any other means; nod AJ1lh. d~~ Candolle hru~ shown that such IJlanu h~'wrally ha,·e rt"fftricted rouges.

But see<ls may be occas.ionally transported in another mam1er. Drift timber ill thrown up on moet i,Jands, <wen on th0110 in tho mid:.t of thf> wide~t ()('('ans; and the nath·es of the oorol-isiRnds in tl1e Pncifl(•, procure

The Comolete '~~'- fCI.arles Da>.Nin~"llinl't

li.EA.~S OF DISPElts..\1... 3tH

:.tones for their tool!, 80lely from the roota of drifted t rees, these stonet~ being a l-aluable royal tax. J fin1l on extuninntion, that when irregu]arly shnJJC<I ;stomo;~

aro cmbeddt.>d in tl1e roots of tree~ sumll JlRfCCls of earth aro \'t.lry frequently enclOiled in their iutcntice~ and behi1td th'im,-i!O perfectly that not n porticlc could be witshed away in the longe~t tmusport: out of ouo small portion of earth thus oomplttely cntloecd Ly wood iu 1111 ook a lxmt 50 yean old, throo dicotyle­donous plnnl3 ~;enniuutcd : l am certain of t1~e oc-curacy of this ohl!ermtion. Again, I can show t1Ult the car· ca..;ses of bird.!, when £looting on the sen, 80mctim1·~ Cst'6po being inun(.o.diately de,·ourcd; tmd IIC(•(Li of mnny 1duds in t110 crops of £looting binli:l loug retain their ,·itality: J>CNI and \'etches, for il.J.,;tanoo, aro killed by oven n few days' immersion in 8eiL·wntcr; but 80mc taken out of tho CtOll of a pigeon, which hncl flootL'<i on artificial st~lt-wnter for 30 days, to my surpride ncorly all germinated.

-Lh·ing birds can hardly fail to be highly c fl'eetire ngcntl in tho t mllilportnlion of SC('(ls. I oould gi1·e many fJlCtl! showing how frequently birds of many kind.i are blo\111 by ~'IIICII to mst d.i;.taucea ~lObi! th•• ot'(.-'tlll. " 'e may 1 think st~fcly llSI!IIIne thnt tmdcr sud1 tircum· 11tauees their mte of flight would often be a.:; mill-'il au hour; and 110me authol'\1 ha\·e gi,·cn a far hi{!hcr u;ti· mate. 1 ha,·o llC,·er f!CCn 11n iil:ltanco of uutrilio~ IIL'e<ls JlR88.ing through the inlet:!tinca or a bird; Lut hard &cedi! of fruit will Jl638 uninjtli'L'd t11rough e\'('11

the digesti,·e organa of a turkey. In the oourso of two months, I Jlickcd IIJl iu my garden 12 kiud~ of scccla, out of the cxeremcut of snutll Lird.s, and thc110 lk'<'llled

pcrf~t, and 81.!1116 of them, which 1 tried, ~rmiuate<L But the following fnct is more imr10rtant: the CTOJiil of Lir!U do not ~~CCreto b'lltitric juice, and do not in the

"

3G2 OEOORAI'IliCAL Dl8TniBVTIOS".

least injure, u 1 know by trial, the germination of eeed8; now after a bird baa found and devoured a large tup)>ly offood,iti.positi\"ely~rted thatalJ the graina do not Jla&l into the gizzard for 12 or e\·en 18 hour&. A bird in thil interval might et~o~~ily be blowu to the dis­tance of 500 miles, and hawk& aro known to look out for tired birds, and the contcntl of their tom CI'Oflll

might thWI readily get IJCftttered. Ur. Brent inforDlll me tlmt a friend of hit had to give up ftying carrier-pigoollB from .Franoo to England, u the bawkt on tho Engli!!h OOMt dct.troyed eo many on their arri\'11.1. Some hawb and owlt bolt their prey whole, and after an interTal of from twelve to twenty bolll"', ffillb"'rge pelle~ which, u 1 know from experiments made in tho Zoolngical Gardent~, include aeeda capable of genninatiou. Some IIOe<b of tho oot. wheat, millet, canary, hemp, clover, and beet gt-nninatOO afU!r lun-ing been from twelve to twenty-one hon111 in the stoml\('hfl of different birda of prey; nnd two IN:lCds of bc!ct grew after IIA\'ing been I hue l'('!ainod for two dnye and fourtocn hou111. Fresh· wRter flah, I find, ent aeedtl of mnny land and water J>lanta: flgb are frequently devoured by birde, and tllus tho IIN'<LI might be transported from place to place. I forced mll.lly kinds of flOOds into the etomachs of dead f~:~h, and then gave tlwir bodies to fl..;h.ing-eaglce, st.nrb, and pe]ica.na ; theee birds after an interval of many hours. either rejected the eoode in pcllcta or JliUI8ed tl1em in their excrement; and Blweral of the9e eoode retained their power of genninatiou. Certain I!C<!<ls, IM>we,·er, were always killed by this pi"'N'88.

Altllough the beak! nnd f~t of hiniB arc generally quite clean, I can show that earth IOJll('tilll('fl adhercfl to them : in one inetance 1 removed twf'nty-two pRillB of dry argil.laceott! earth from one foot of a partridge, ll!ld in thie earth there nB a pebble quite aa large aa

Th.. .;...,molete WorK ofCha rl~ D&rwln 0~---

li.ZAN8 OP DI.8P£RSAL 3(3

I he I!IOOd or a vetch. ThUB seeds might occasionally be trtUliJIOrted to great distancea ; for many facta could be gin•o lhowing that aoil allllOfJt everywhere is charged with IOOd& Reflect for a. moment on the milli0111 or quails which aonoally Croll the Mediterranean; and tao we doubt that the earth adhering to their foot 1\·ould BOmctimes include a few minute &OOda? But I shall Jlresently hn-re to recur to thia mbject.

JU icebergs are knowu to he 10mctim.ea loaded with earth and stonee, and ha,·e e\·en carried bruahwood, bon('fl, and the Deflt oC a land-bini. I can brudly doubt that they must occaaionally ba\·e tr&ll8)JOrted seeds from one JIOrt to another of the arctic and antarctic rcgiona, 111 sugg.:l!tcd by Lyell; and during the Glacial period from one JIOrt of tho now temperato regiollll to another. In the .t\wree, from the larg9 number of the spcciet of Jllant.il common to Europe, in oomptuison with the plant.& or other ooeanic islands ncorcr to the mainland, and (lUI remarked by Mr. ll. C. Wa180n) from the IOID&­

whnt northern chamcter of the flora in compari110n with the latitude, 1 suspected that thceo islands had been )lllrtly •tucked by ice-borne lltleds, during the Glacial epo('h. At my requctt Sir C. Lyell wrote toll. Hartung to inquire whether. he had obeen·ed erratic bould(·l"8 on thNiO islands, and he all.llwered that he had found laJb'e fragments of granite and other ~ka, which do not occur in the archipelago. Uenoo wo may snfcly infer that icebergs fonnerly landf'd their rocky burtlW!.DJ on the shore~ or tl~e~e mi(l-ooean iJauds, and it it at lca&t J>o~o>ible that t!M>y may have brought thither tho lll'C<lsofuorthem Ilifmt.l.

CoWiidering that tho acnral abo,·o means of trnra­port, and that IC"I""cral other mcallll, which without doubt remain to be d.illoo,..ercd, hal"e been in action year after year, for centuries and tena or thousand~ or

R 2

:::0..1 OEOOIL\.PHIC.-\1, DISTRIBUTIO:<",

years, it would I think be n marvellonil fuct if many plants had not thus become widely tnlll~flOrt('(l Thc;;c llll.'allil of trans110rt aro somNime11 co.lled ll.C('idental, but tiW ii! nOt strictly correct: thf' currentsofthf' sea arc not ~~identa l , nor is tho dii'(>Ction of prc\·alcnt gales of wind. lt sllonld be oboscr.-cd that acarcdy any moollll of transport would carry seeds for \'cry great di:!tauces; for ii('C(li! do not retain their 'itality when eXJlO!I('(\ for 11 great length of time to the nction of ~~Ca·

water ; nor could they be long carried in the crops or iutestinesof birds. These mclln:J, bowe\·cr, would sullioo for occasioua.l tmnaport acro;e: tractil or &ell eomc hun· drcd miles in breadtb, or from island to island, or from Jl continent to a neighbouring island, hut not from one tlitltnnt continent to auotl1cr. 'l'ho floras of distant continents would not Oy such means booorue mingled iu 1my great (\et,rroc ; but would remain as di~tinet ns we now seo them to be. 'l'he currents, from their course, would never bring seeds from North America to Britain, though they might and do bring S(>(>JS

from the " 'Cflt Indies to our wcstcn1 sl1orcs, whel'(>, if not killed by eo long an immel'!!ion in 118lt-water, they could uot enduro our climate. .tUmOI:!t e\·cry year, one or two land-birds nro blown II('TOSS tho whole Atlautic Ocean, from Xorth America to the wc,.tcm sl10re& of lrelilnd a1ul England; but seeds could be lmnS)lOrt('() by tl1eso w1wdcre.rs only by one mean~, namely, in dirt sticking to their fee t, which is in itself a rnro accident. EYen in this case, how small would the chance Le of n ~falling on fa,·onr· ublo 110il, and coming to maturity! But it would be a great error to argue tlult because 11 well-stock('() i:ililnd, like Grcnt Britain, lmsnot., ru1 far ae is known (and it would be Yerydifficnlt to Jlro\'e this), f'eC{'ivcd within the bt few centuries, through occasional means

i:l .;be t,.;vmolet..WQfk of Charles Darw1n OnLnt~

m ; m:s:O THE OT.ACIAI. l'F.RIOD. :.IG5

of tmnsport, immigrnnta from Europe or any other continl'nt, that a J)()Orly-stocked island, though fl"tnuding more remote from the mainland, would not re«>h·e colonist-8 by similar menU& I do not doubt tlmt out of twenty seeds or animuls tmu.sported to an island, ewn if far l e&~ well-stock('(! than 13ritnin, scarcely more than one would be 80 well fitted to its uew homt', n.,. to \.Jerome fUlturalilll'(i. But thia, ns it seems to lilt', is no ,·alid argument ngain,;t what would be efTl'<'INI hy OCCftl!iounl meniL .. of tnmsport, during the long IRJl8e of gt'Ol~i('ll.l time, whilst an ishmd was being npht'nvcd and formed, and before it lwl bcrome fully lltOC'kNI with inhabitants. On almost bnro laml, witl1 few or no destn1clive in~lil or birds )i,·ing tl1ere, nearly C\"t'ry seed, which dmnood to nrrh·e, woultl be sure to h<enni­natc and survive.

Di8per~al durin9 tM Glacial p!ri0d'.-1'he identity of many plaut-8 nnd animals, on mountain-sununit.~ l!C'po­nlted from ro<"h otht'r by lnmdrcde of mil~ of low­land'". where the Alpine species could not JJ06,~ibly exist, is one of the m08t striking C1UlC8 known of tho l!llme ~pC('ioe living at di10lant points, without tho npJlflrent J)OII.~iUi l ity of their ha,·ing migrnted from ouo to tht' otht'r. J t is inde·cd a remarkable fact to sre 80 mnnv of the snme :Jllanta lh·ing on thf'l snowy regions of th;, Alps or Pyreu('('ll, und in the <'lllremc northl'nl ports of £urope; but it is far more remarkablc, th,.t thc plants on the Whit<~ 31ountnins, in tho United States of America, are nil tho Slime with those of Labrador, nud nearlr all the snme,ns we hear from.\sn Gmy, with th08C on thl' loftiest mountain!l of £uroJK'- Even 8!1 long a~ as 1747, such fllCiil led Gmelin to conclude tlmt th(• 81\me IIJJeCies mu,-t l11n-e been' indeJJendl'ntly eretltcd at 80\"Cral distinct points; t1nd we mif:ht have l'('lllfl i ne~l

360 OEQORAI'lUCAL DfSTUIOL"TIO!'o', C11.oP. XI.

in this llftmo beli,f, had not AgMI!liZ and others called vi\·id attention to tile Glacial period. wl1ich, na we shall immedifLtcly ~. niTurds 11 simple cxt>lnnation of tlwso fi1cts. "'e hn\"O c\·idcnce of almost cwry conceivable kind, organic and inorganic, that within a wry rceent geological periol~ ceutl'fl.l Europe and North AmeriCD 1uffercd under an Arctic climate. The ruins of a bouse Lumt by fire do not tdl their tale more plainly, thau do the mountains of Scotla.nd nne! Wales, with their BCOred flanks. polished surft~ccs, and ~rchcd boulders, of tho icy streams witb which tbeir ,·alll'ys were lately fillecl So greatly lw the climate of .Europe changed, that in Northern Italy, gigantic mol'fl.inc R, left by old glaciers, are now clothed by the \·iue and maize. 'Through· out a largo pert of tho United States. erratil" bouJders, and rocklii!C'Orcd by drifted icebergs and (l()ft.St-ice, plainly rC\"Cal a former cold pcri<Hl.

Tho former infhfcnce of the glncial elimato on tl1e distribution of tho inbaLitnut11 of EuroJX•, WI explained with remarkable elcameiJS by E<hmrd l~orbcs, is sub. Btantinlly WI followa. But we shall follow the changt"'l more readily, by supposing a now glat'ial period to como slowly on, and then p!lllil away, as formerly occurred. A11 tho cold came on, and as each more 80utlwrn zone became fitted for arctic being~~ and ill-fitt(l(l for their former more temperate inhabitants, tho ]filter W011ld be sn1>· planted and arctic productions would take their place~. i'he inhabitants of lhe more temperate regions would at the f!fliile tUne tm,·el 80Uthward, mliC88 they were stopped by barrierB, in which ct~Se they would periBlL Tho mOWitainJ would become covel't'd with mow and ice, and their fonncr Alt>ine inhabitantil would descend to tho plains. Dy tho time that the colcll11~ reached iti! maximum, we &hould htn·e a unifonn EU"Ctie fauna and ftom, CO\"ering the central po.rts of .Europe, All far

iii The Comolete No.1; ..>f Charles Da~~.N!n "II

l)UJIINO TilE GLACIAL P£RIOD. 367

aouth us the Alps and Pyrenees, and oren stretching into SJI8in. TI1e now temperate n>gio1111 or the t:nited States would likewiso be covered by aretie plnntil aud ani mala, and thC!IC would be nearly the SD.mo with thOEIO or Europe; for tho present cireumf10lnr in.1mbitnuts, which wo suppose to hare overyll'ilero travelled aouth­wnrd, nro rcm"rknbly uniform round tl10 worl!l \Vo may suppose that tho Glncinl JX!riod ctuno on i\ liltlo earlier or later in North America than iu ]~urope, 110

will the 10uthenl migration there hn\·e been a little earlier or lat('r; but this will make no difference iu tlu~ final re;rult.

As the warmU1 returned. tho fU'Ctie fonne ... -ould re­treat northwnrd, cl011e)y followed up in their retreat by tho productions of the more temperate regions. And 811 the snow melted from the bases of tho mountains, tho arctic forma \I"Ould seize on tho clcllred and tlmwe<l ground, always ascending higher and higher, as the warmth increased, wh.il.at their brethren were pursuing their northern journey. Hence, when tho wannU1 had fully returned, tho same arctic epecice, which had lately li\·e<l in a OOdy together on tho Jowland8 of tl10 Old fWd !\ew Worltl.a, would be left. isolated ou d.i.t!tant mounta.in­sulllmitl (ha\·ing been exterminated on alliCI8Cr bPights) and in the arctic rcgio1111 of hoili hcmist1hert'J8.

Thus we can unden1tand the identity of many planta at points 10 immensely remote 811 on the mountainll of tho United StatOB and or Europe. Wo e&n thus aOO unden~tand the fact that the Alpino plants of ench mountain-rongo are more cepociully rclntOO to tho arctic fom18 Jil'ing duo north or nearly duo north of them: for tho migration 811 the cold oomo on, nnd tho rc-mi~,'·ration on the returning wam1th, wil1 gi>Uerally Jm,·e been due 110uth and north. 'l1le A !pine plnnts, for ex.ample, nf Sootlnnd, as remarked by Mr.ll. C. Watson,

308 OEOOil.\PIIIC.U DISTmnrT10N, <'M••· XI

find tlltW of thl' Prrenf'e!l. Ill! remarkl"d hy R11mond, flft'

nmre (';<pecially nl\i,'(( to liw, planiJ! of northen1 Senn· dinM·in; thOIO(> of thl' United Staf('t to LnLmdor; !hOI!(' of tht' mountain~ of Silx>ria to th,. art"tic n>gions of t11at ronnt~·· '111~ ,.i('wl<, grounded lUI thl'y lin.' on i!Jt' Jlt'rft'Ctly wel\-l\l'('(·rtainrd OCX'llrn.'D('e of a former Gltl{"inl 1>~·riod. seem to lilt' to t'Xplain in /110 flftti~fnrto~· a llllllllll'r tl1e pf(lfl('nt. di.,;tribution of the Alpine aud Aretic prodllC'tion!l of .Europe and America, tlmt. when in other "'h-ions wo tlncl tlw Mme spt'('iCII on distant moun· tnino41nmmiU., Wt' may nhnost oonclnd11 without other e,·jd,..n('(', that a ookler dimatc permitted their Conner migration ACroM til(! low inten·ening tracts, einoo be­rome too "'rm for their existenci

H the climate, linl:'tl the GlacialJMlriod. lw O'I"Cr be<-n in any d~ wanner than at lln'l'l'llt (88 110me gro­lfl.rkltil in the rnited Rtlltes bdiOYO to lum~ been the riWl, chiefly from tl1n distribution of tll(l fOAAil Gnatho­llon), thrn thonrctie nnd tempernto )lt'QIIUt'liOIIIIwil\ ot R very Into period hn,·e mllrchcd n litt[(l furthrr north. nurl ~ubeequently lun·e rematcd to their prt'8C'nt !Jom!'fl; l•nt I hn\·e met "·ith no sati&factory t''l"illen<>ewith !'ei'))('("t.

tn thia intercalated slightly wanner period, f!inl'e theo (~IIW'ial period.

'TIIC arctic fomu, during their Jon~ 110utht'm migm· tionand re-migration northward, will hn,·e bet>n t'xposed to nearly the flftmo dimnte, and. as is e8JX>Cially to he noti('l:'(l, they will Jun·e kept in a body together; eou­IC<JU<'ntly th('ir nmtual rt'latiouJ! will not have been murh dis:turbed, ami, in aceonla.noo with the JlrincipiE'!I in!'ulcated in this mlume, they 1'dll D()t hn,·e been liable to much modili!"fltion. But with onrAIJlino Jlrodnctionl<, lc•n i!ola.ted from tho moment of th(' returning wanuth. ll.,.t at. the 00!1('11 nnd ultimatdy on tho summits of tl1e mountaillll, tho mse will I.Jn,·e i>e(>u 110mewhat dif-

.Cbarid..O.W'""'""----

DC AlSO TilE GLACIAL I'ERIOD. 3(l!)

fl'ft'nt; for it is not likely that all the 1111mo art"lic @])('·

ci('ll 11·ill have ON>n lef't on mountain mngc~ distant from CA.Ch other, and ha\·o !1\ln·i,-cd there O\·er sin«'; thev will, also, in all JlrollRbility htn·e br-come miug]('(! witi, flll<'icnt Alpine SJlCCi('ll, which mu~l hanl cxi>~tcd ou tho mountains beforo tl1o eommcn<>emcnt of thn Glacial epoch, and whkh during its coldC'Bl period will June be<'n IC!U]Xlrtlrily dri\·en do1111 to thn plains; t}l(')' will, abo. ha,·e ))('(>n 1'X]l08C<l to &OIIl<'what different dimAt.ol influ•·nce;o.. Their mutual relAtions 'll"ill th113 haw• bclc>n in IIOIIle degree dbtnrbcd ; eoru;e.q,wntly they will Jun·o LI..'Cn liable to ruodiflcntion; and thia we find has leen the case; for if we compare tl1c j)f'('8('nt Alpine plnnt~ llnd animalil of tho t'KlW!ra.l ~~ European mountain· range~<, though \'Cry many of tllC sp('('iCfl are idl•ntieflll~· th(' same, &Omo Jlret!Cnt nrietie11, 110me arc ranked ~ douLtful fonu11, nnd 801110 few aro diiltinct y<'t clOICly allied or representnti,·o 1<peeiC8.

l n illnstmting wlmt, ns l l.lclic\'(', nctunlly took plnce during the Gl.acinl period, 1 IUIStuncd tlmt at its oom­m('u~ml'nt the nretie productions were 1111 unifonn round the polar l'('giOIU as tlk'y aro at the Jln"f'('nt day. But tl11' foregoin~ remarb on diiltril.mtion aJlply not only to strictly nretie fonns, but Rl!!O to many suOOretie find to !lOme f<!w northcn1 tempemte fonns, for !IOmo of tii('IIC are the snrue on thclow('r mountains and on thl' plains of North America and Europe; and it may he rt'MOnably asked how I IUX()Unt for tho n~ry d('­groo of unifonnity of tiJC suOOI'I'tic and northern tem­J~nltc fonus round tho world, at the oommen('('mcnt of the Glnciul period. At tho p«'scnt day, the suOOn•t ic and northern t('mJ~r&to prodnctions of tlll\ Old and New Worlda aro lk't)llrated from each other by tllC Atlanti<' Oeean and by thl' extrem<' northf'nl ])llrl of the Pneifie. During the Glacinl J~riod. when tho in-

><3

370 OEOQRAPRICAL DlSTniDtiTO!o.",

habitants of thl' Old and Xew Worlds lh·ed furthPr f!Outhwnnls than at preaent, th>:'y mnat have been still more completely fl('pnrotcd by wider &JXLCe8 of OCI:fln. 1 Jx-licJ·o the al.>ovo difficulty may be surmounted by looking to still earlier changes of climate of an opposite nature. We havo good reaaon to belic,·e that during the newer Pliocene period, before the Glacial epoch, and whi.lat the majority of the inhabitants of the worM W>:'rt' apceifically the snme 8.!1 now, the climate waa \\11nner than at the llreaent dny. flenco we may sul>­]>OEII'l that the Ofb"'miams now living under tl10 climate of latitude 60°, during the Pliocene period Jh·ed furtl1er north under tho Polar Circle, in latitude 66<>-V"i"; and that the strictly arctic Jlroductions thrn Jj,·ed on tl1o broken land 11Lillncarer to the pole. Now if we look at a globe, we slut.U liE!<! tllflt nuder the Polar Circle there is almost continuoua land from Welltern Europe, through Ri!x>rin, to eastem America. And to tltie continuity of the eircumpolilr land, and to the consequent ffC('{lom for intermigmtion under a more ftn•ourublo climate, I attribute the uocessnry amount of unifom1ity in the 1111b-ru-ctie and nortben1 temperoto Jlroduetioll.8 of tl1e Old and NewWorldt, at a period tmterior to the Glacial <pocb.

BeJieJ•ing, from ~fLBOil.8 before alluded to, that our continents have long remained in nearly the sa.mo «'la­tive position, tl1ough subjected to lnTg(', but })(l.rtial oecillntiollll of lC\·el, I am strongly indincd to extend tl1e nbol""o ,-jew, and to infer that during eome enrlier and still warmer period, I!Dch aa the older Pliocene period, a large number of the snme plilnta and animals inhabited the alm011t oontinuoUB circumpolar land; and tllflt the9e plants and atllmals, both in tho Old and New Worlds. began elowly to migrate eouthwards aa the climate became leM warm, long before the com-

Cll.iP. XI. DUilL'iG THE GLACIAL PEIIIOD. 371

meni'Cment of the Glacial period. \Ye now ace, as I IJelie,·e, their dctiC('nda.nt.s, mostly in a modified con· clition, in tho centml ]JartB or Europe nnd tl1o United. Statee. On this '-lew we cno tmderstnnd the relntion· ship, with ,·cry little identity, between tho productions or North America nnd Europc,-n relntionship which is most remnrknblc, OOil.Sidering tho distnneo of tho two nrens, nnd tl•cir 11Cpnrntion by tlu} Atlnntic ~an. \\'o can further understand tlw singular fnd remnrkcd on by sen~rn l oiJ&en·cl"'l, that tho Jlroductio!UI of Euro]Je and .\mcricn during the later tert.inry etngce were more cloecly related. to each other than they arc ftt tlw pre-­sent time ; for during these Wllm!er Jleriods the northern port.B of tho Old ftnd X ow Worlds willlmve bet>n almost ooutinuons.ly m•ited. Ly land, I!Cn·ing lUI a bridl--e, since remlf'ro<l impM&lble by oold, for tho inter--migration of their inhabitantil.

During tho slowly decreasing wannth of tho f'!i(X:(!ne period, ns soon ns the species in commou, which inhubitcd tho Now nud Old Worlds, migmted 110uth of tho 1~olar Cirt'ic, they must have been OOID]Jiet(']y cutotr from each other. Tili&IICJXIrnlion, as fur M the more temperate ]JfO.

ductions aro concerned, took ]Jiace long agee llb-"0. And f\.11 tho plants and animals migrated IIOilthwnrd, they will have become miugled in the one grt>at region with tho nati,·o American productions, and have had to compete \l-ith them; and in tlu~ other great rt>gion, with thoso of tho Old World. Consequently we hnxe here every· thing fa,·oumLle for much modificntion,-for fllr mom modification thnn with the Alpine production!!, left isolated, within a much more recent period, on tl•c ec,·erol mountain·rnngcs and on tho nrctic lands of tho two Worlds. Hence it has come, that when we comrere the now living productiolll! of the temperate regions of tho New IUJd Old Worlds, we find ,·cry few identi('al

----"'4l.c"'-'""" te .tl'orkf' .arle0..J<IIliltne

372 OEOOR.-I.PIIIC.\L DII!TRIBUTIO~,

I<JlC'Cies (thong-ll AAA Gmy hns lntdy sllown thnt more Jllnnts nrc itlt•nticnl thnn wn" fonnrrly PIIJ'lX~.-rl), but we find in ew•ry peat r\!IAA many fonns., whirh &Orne naturalists rank a' ~plliroll'IK'e!l,and otiH.'nl lUI dis­tinct PpeciNJ; and a host of d()!;('ly nllif'd or n>Jln'!len­tntinJ fonns which nrc mnk<'<l by all no.tur;,liJOi.i as ~peeifieally distinet.

.>\~ on the lnnd, 110 in tlw waten1 of the l!t:'a, n slow routhf'nl migmtim1 of n marine fauna, which during tht> Pli(l('(!M or ewn a 110mewhat earlif'r JX'riod, was llf'nrly unifonn 11.long tlu• eontinuoUll s!Jores of the PolAr Circle, will acrount, ou the throry of modifiCfltion, for many dosely nllied fonns now li\·ing in fli'('IUI completely Stmdell:'d. Tllllil, I think, we ean understand the pre­f!('Uf"e of many existing and tt'rtiary n')Jf'('9('1ltntin• forms on the etu~tem and wel!tenJ i!hOI'I'fl of temprmtc North Auwrica; nnd tll<': still moro 11triking eru.oe of many clo;;ely nlliNl rmstn('('an8 (ll8 drscribed in Dnnn'8 ad­mirable work), of110me fi8h nnd other marine nnimnl.s, in thr i\[editrrmnf'an and in the seas of Jnpan,-nl'('ns now S('pamWd by a eontin('nt flnd by nf'nrly 11 hcmi­I<Jlhf'reofequatorinl OO('(IJL

'L'hrf;C CIU!('jJ of relationship, without idf'ntity, or the inhabitantt~ of S('IUI now di~joine1~ and lik('willO of til(' past and IJrescnt inhabitants or the temJl<'rRf(\ lands of North A1n('rii'U. nml Europ{•, aro inexplienblr on the theory of t'l'l'81ion. We cannot say that they lun·e been CJ'('ft!ed &like, in OOM'('IIIJOndPnOO with tho ll('(lrly similar phr~i('tl\ oooditiollll of the areas; ror ir we oom­fli'l'l', for instance, certain pnrta of South America with the south('rn continents of tho Old World, we 8CC countries doecly corrcS!lOUding in all their physical oonditions, but witl1 their inhabitants utterly dissimilar.

But we mu~t n-turn to our moro immediate subject, th(' Glncinl period. I am com·inccd that Yorbea's view

('llu. XI. m:Rili"O TilE GLACIAl, r'EiliOl"l. 3i3

may he larw:-1~· elltendcd. In Enrop<• we lw.n• thf' ])lnin('~t e,·jd;•n{'(' of the oold peri(l(~ from tile w('Sten1 shoree of nritain to the Onml mnge, and I!Oulh"~ml to tlu.• Pyn>n{'('!l. We may infe r, from the fro:r.en maJnmnls and lliltnf'(' of the mountain ,·egetntion, tllilt Ri\x>rin WllS ~ imilnrly affecte-d. Along the llimalnrn, nt J)()ints 000 m ii('S npnrt, glncicrs have left the mnrke of tl1eir fonner low dPII('('nt; nnd in Sikkim, Dr. Hooker 1111w mai:r.o growing on ~i~ntic ancient momincs. Routh of th<' equntor, we hnvc 110me direct t''·idl'n{'(' of fonner glncinl action in Xrw 7..('fllnud; and thf' 1111me plnnf.i!. found on widely IM'plll"flted mountains in this islnnd, tt•ll the Mme story. If one ncrount which 11811 been llllbli.•h('(l can be tm~ted, we haw• 1lirect e,·idf'nre of glaeinl netiou in the IIOUth-<'astem oon1er of ..~.\ust.rnlin.

Looking to America ; in the nortiK'nl half, i('('-bome flltgmenlil of llX'k have been obscn·ed on the enstern side ns fnr 11011th as Int.. 36°-37°, and on the shores of the P~~~:·ifk, whNe the climate i~ now 80 different, us fnr 11011th fiB Int .. •16°; errntic boulders llll.n:>, nl'!O, been notie«l on the Hocky llonntains. In tlu~ Cordillem of Eqna1orinl South AmeriCIL, p;lacicrs on{'(' cxt(•nded ftu· below tlK'ir lli"Cflent Je,·el. Jn ecntllll Chilo J was astonishe·d at tho stn1eltl.J"(' of a vast mound of dPtritul', about 800 f{'('t in height, C1"088ing a 1'Ailey of the Andl'8; And this I now feel oom·in('('(! wns a gi~ntie momine, lert far below rmy existing glacier. J•'urthcr 11011th on both sides of tho oontincnt, from lat.. 4 I to tho 11011thennnost extrem ity, we hm·e tho eh;nt{'st o\·idenee of fonner glacial net ion, in huge boulders tmnsported fnr from their pnrent 11011~.

\\'e do not ).·:now that the Glaeinl ~'llOCh WIIS ~trietly simnltan('()US nt these sewml far distAnt points on opllO­site side~ of the wori<L But we han! gtKXl c,·ideuoo in almOI!t c\·ery Cfl!JC.', that the t')lOCh wu included witl1in

3i4 OlroORAI'ntCAL DlSTRIDCTIO,_, Ca .. P. XI.

the latest geological JX'riod. We haw•, abo, excdlcnt evidence, that it endured for an enonnous time, as measured by years, at en.cl1 point. 'Ihc eold may hrn·e como on, or luwc ceaacd, earlier at one JlOint of the globe t.han at another, Lut seeing that it endured for long nt each, and that it W1l8 contNUllOf8neoull in a goologica.l I!Cille, it IE.'CillB to me probnblc that it was, during a po.rt at least of the )Jeriod, actually simulta­nooWJ throughout tho world. Witl10ut 110me distinct el·idcnce to the contrary, we may at I~ admit as probable that the glacinl action wl\ll simu.ltnncous on tim eaateru ami westeru sides of North America, in the Cordillera under the eqUD.tor and m1drr the wanner tcmperote zones, and on both 1!id011 of the IIOUU}Cm

extremity of tho continent. Ir tl1is be admitted, it is difficult to avoid believing that the tCIUJJCrnture of tl1e whole world WRI at this period s.imn1tnucously cooler. But it would suffice for my purpo8t•, if the tcmJJCrnturc was at the same time lower along certain brood belts of longitude.

On tllis l'icw or the whole world. or at ICtlllt or brood longitudinal belts, having been simultanoollf!1y colder from pole to pole, much light can be thrown on the Jlresent distribution of identical and allil'd '!JeCiCII. In America, Dr. Hooker haa shown that hl'tw(!('u forty and fifty of the flowering plants of1'icrm del :E'ucgo, forming no inconsiderable part of its scanty flora, nrc co1nmon to Europe, enonuously remote as tiK-f!C two points are; nud there arc many cl011ely allied spcci011. Ou tho lofty mountains or equatorial America a h011t or pE'(.'llliar species belonging to }:uropean gt-ncra occur. On tho highest mountains or Dmz.i~ 110me few E1uopean genera were found by Gardner, which do not uist in the wide inten·ening hot countries. So on tho Silln. of Caraceas tho illustrious li umboldt long fle"'' found species belong-

,,. ~" r w n._ f Chdfie,s_O"""'~~---

Dt:niSO TUE GLACIAL I'EniOD. 375

ing to gcncm clmrncteristiOJ of tho Cordillcro. On tho mountuillll of Abyasinia, 8(Weml European fonns and eomo few repreecntatin~s of the peculiar flom of tho Ca1)(1 of Good HoJIO occur. At tho Cape of Good Hope a ,·cry few Europenu species, belie,·ed not to ha,·o bet>n introduced by man, and on tho mountain.~, eomo few rcprt'IK'ntath·o ]~uropcrm fonns are found, which Jmvo not bt:><>n discowrcd in the intertropical po.rta of Africn. Ou the ll.irua.1lya, ami on the isolntcd mountain-mnw-!'1 of the penirumla of lndia, on th{l heights of Ceylon, and on tho volcanic cones of J1n·a, many plants occur, cith('r identically tho same or representing cnch other, nnd at tho 81\lllO time representing plant8 of Europe, not found in the interwning hot lowlands. A list of the ~nom oolltX"tcd on the loftier peaks of Ja,-n ra~ a Jli<"ture of a rollection made on a hill in EuroJ)C! Rtill more striking is tho fuet that southern Australian foma nro clcMly reJlresented by Jllants growing on the summits of tho mountains of Uon100. &me of these Auatralinn fon!Ul, a.s 1 hear from Dr. Hooker, cxtcud alon~ the bci!!;hts of tl10 pcniu.sula of lfalacca, and are thinly IJCilltt'red, on thl' 0110 hand o,·cr India and on tho other a.sfRrnorthiiii J fljiRil.

On tho southern mountains of Austrnlia, Dr. 1~.

l\Hlllcr has diil('()vcred se\·crnl European spcdcs; other BJX'Ciell, not iutrodueed by nmu, artur on the lowlnnds; and n l01Jfi list con be gi,·eu, u 1 am infom11Xl by Dr. J looker, of European geuem, fom1d in Alliltrnlia, but not in tho intenncdiato torrid n'b-iOill!. In tho aclmir­ablo ' Introduction to the I'lom of New Zenlnnd,' by Dr. Hooker, tmfllogous ancl striking facts 11ro gil·('n iu regard to tl10 Jllauts of that large island. Hence we see that throughout tho world, the plants growing on tho more lofty mountains, and on tho tcmpernte lowlands of the northern and sou them hemispheres, nrc sometimes

Workof .... .arlA..

376 Of:OGR.\PIII('.~L DI.'!TlliBrTIOS',

identic-ally tho Mme; but thry are much oft<'nf'r spec.i­fkall~· di.~tinM.. though rclnted to each olhf'r in a mO!'t remarkable manner.

This brif'f abl!truet a!l!)li<'ll to plant.'! alone : somr strictly analogous facts Mnld be given on the dil!tribu­tion or t<'rr(>~trinl flllimals. In marinf' Jlroductioruo. similar Cll-'1<'!1 OC'<'tU"; as an cxampl<', 1 mny quote n wmark by till' higbe11t authority, Prof. Dunn, that "it i~ certainly a wonderful rll('t that New Zen.land should haw a dotiCr re8('mblanee in its en!Jitaero to Gret~t Britain, itil anti1Jode, than to any oth<>r )l8rt or th<> world." Sir J. Hichnnbon, also, spenks of the. re­BJlpcarnn('(' ou tl1e shores of New 7..ealnud, 'l'RSmnnin, &c., or northern romUI of llsh. Dr. llooker infonnll mo that twenty-th-e specie~~ of A.lgm nre common 10 New Zealand ami to Euro!)(', but haYo not be<!n round in the int('nnf'diate tropi('ftl 8('88..

It sl10uld be obston·('(l th.nt the northent BJ)('('icllllnd fom1s found in tl•o IIOUthent po.rts of the IJQnthem hemi­sphen', and on thomountnin-nmges of tl•e intertropical regions, are not arctic, hut beloug to th~> northern tem­pernte Wn<'L All Ur. n. C. Watson hall 1'(-'(_"elltly re-­marked, " .In reeeding from polar townnli! equ.ntorinl latitudes, the Alpine or mountain floms 1'\'fllly become less 1111(1 IC88 nrctie." l\[nnr or the fonne ]i,·ing on the mountains of the wnrn1er n'gionll of the Nlrth ami in tho BOuthem hemi!!phero 1\ro of doubtful ,-nlue, being m1lked by BOttle natumlists Bll specifi('811y di.«tiuct, hy others as \'llrieties; but 110mo are eertRinly idf'utiml, and many, though el09Cly related to northern fonns, must be nlnk~\11!1 di~tinct S])('('iea.

X ow l<'t ua ace what light ean be thrown on the fore­~ing fll('t.;o, on the belief, supported Bll it is by a large body of grologieal el·idenoe, that the wholo world, or n ltu·ge part of it, wns during the Glacial period aimulta-

lll;'IUSO TilE GLAC'IA.L 1'£1\101). 3 77

ll('()U~Iy mnc.'h ro!d('r than nt p~nt. The (Haria! peri01~ lUI mf•twured by yl"ftrs, must Jun-e lx-en ,-ery long; and when we remember ow•r ~~-Jmt n1st ~~~ 110me tunumliM'd pl.nnta and nnimnlslun-c IIJ)n't\d 11itbin a few ('('n turi<'l!, tbis period "iJI Jun-e ~~~ ample for any nmonnt of mign1tion. A8 the rold ('nme sloll·ly on, nil the tropi('ill plnnta ami oth('r produ(' tions will have J'('frt-'nl<'·d from both 11ides towartl.! thi> C'Qtu\tor. followed in tho n.'flt by tho tNtlpemto Jlroductionll, and th£'&e by the at'(' tic.'; but \\ill• the lattC'r we nre not now con· CC' rnNI. 'fhe II'OJiirol plnntil p roOObly sufl'et'('·d mul'h e:.;tin<'lion; how mul'h no OIIE' ("811 !Ill~'; JX•rhnps for­mNly the tropics supported lUI many !lpC("iPil aa we see at lh<> Jln!eellt (l.ny cro11-ded togethC'r at the Cape of Good !l op<>, and in parts of temJM:mte Au&mlin. As we know tlmt many tropical plnnta and a1Linmls can witlll!tand n conl!idcmble amount of rold, many might lmnl eBCaped utennination during a modrmto full of t empemtul'(', moro especially by <'ll('nping into tlw wnnn("IJt ~po t ~. llut the great fad to bear in mind is, that all tropi('il.) produl'tions willlum! rrutr~·l'('(l to a cer­ta.iu utent. On the otl1er hnn(~ the temp(·mte I'~

durtiom1, artC'r mi~.'·mting nearer to thi> c-qnntor, tho1lf!'h th<-y will llll,'e ~~~ J>laced under 1101ll£>11'llllt Jl("W ron­ditinnll., will htn'(' l!lllfered IC'fJ8. And it is C(•ttain that many temjl('mtc plaul", if protcel('(] from tho inn:xi(L~

of comp<'titol'$, oon withstand n llHI"h wanner dimnte than their own. Hence, it 8('('11l8 to mC' ]~ible.

l.x-aring in miml that the tropiC'Ill Jlt'()(luctioll8 were in fl suffering stato and could 110t hnve Jll'l.'8Cntcd n finn front n,:,"'linllt intruders, thnt a certain nmnber of thll more ,·i~-o'Orous and domillllnt temJX"ntte fonns mip;-ht hnH~ JX'II<'Imt('(] the llll.ti\·e ranks nnd hill'<' reft("b('d or <'l'C'II<'l'OAA('(lthc NJ1Uilor. 'l1tein''flllionwould, of('OUJ'8(', han> ~~~ gt'('atl~· fn,·olned by ltigh land. and JX'rhaps

378 GEOGRAPlllCAL DISTRlBUTIOY,

by a dry climate; for Dr. Falconer infonns me that it is the da.mp with the heat of the tropics which is so destnJCtive to perennial planta from a temperate cli­Ill[l.te. On the other hund, the most humid and hottest districts will lun·e afforded an asyhun to the tropical no.tives. 'l'he mountain-ranges north-west of the Hima­laya, o.nd the long line of the Cordillern, seem to lliwe afforded two great lines of invasion: and it is a striking fact, lately communicated to me by Dr. Hooker, that all the flowering plant8, about forty-six in number, common to 'l'ierra del Fuego and to Europe stiU exist in North America, which must luwe lain on the line of mnrch. But I do not doubt that some temperate productiollB entered and ci'QBSed even the Wwkmda of tlae tropics at the period when the cold was most intense,-when arctic forms had migrated some twenty-five degrees of latitude from their II!Lth·e country and co\·ered the land at the foot of tl1e Pyrenees. At this period of ex­treme cold, I believe that the climate under tho equAtor at tho level of the sea wna about the same with that now felt there at the height of six or scn:m thousand feet. During this the coltlest period, I !!Uppo!!C tho.t large spaces of tl1e tropical lowlands were clotlaed w:itlt a mingled tropical and tempen1te vegetation, like that now growing with strange ltuuriancc nt tho base of the llimalayo., as graphically described by Hooker.

'l'hus, El8 1 beliow, a considerable number of plants, a few ter-restrial animals, and some mo.rine productions, migrn.tOO during the Glacial period from tho northern and southern tern perote zones into the intertropical re­gions, and some e\"en crossed tlae equator. As the warmth returned, theso tempemte fonns would naturally MIC('Jid the higher mountains, being e:<tem\inatcd on the low­lands; those which had not reached the equator, would rc-migmte northward or southward towards their former

C•••· XI. DL""B.IN'O TilE OLAClAL PERIOD. 370

borne~; but the forma, chiefly northern, whii'h lwl crollt"d the equator, would tmvellitill furtl1er from their hom01 into the more tempcmte latitudes of the opposite hemisphere. Although we luwe reMOn to believe from geoiOJ:.,oical eridence that thll 'lll'hole body of arctic shell• underwent ~Ce.rt'('ly any modiJkation during tht-ir long aouthcm migration and re-mif:,"'1lliou northward, the cue may ha\·e been ~·holly different with thole intruding forma whi<·h lll"ltled thtlll!l('ln~s on tllC interlroJlical meunt.nins, tmd in the IIOUthem hemisp!Jcre. 'l'bcae beinp; aummndcd by strnngt'tl will ha,·e had to oompcte with many new fonns of life; and it U Jlrobo.ble that III!II'Cted modificatio1111 in their structure, habiu,and con. stitutiona will ha\·c Jlrnfited them. il1U1 ronny or theee wandcrel'8, though 1till Jllainly related by inberitanoo to their bn-thren of the nortben1 or 80Utbern hemiliJlhrn>A, now uist in tl1eir new homes 11.9 well-marked ,·nrietiea ornadi.tltinetii))CCies.

1t iJ ~~ remarkable fact., strongly in.sistcd on by Hooker in regard to Amerit'ft, and by Alph. de C'andolle in re~rd to Austmlill, that mnny more identiral plnntll and nllied forms have apparently m.igrated from the north to the llOtllh. thnn in a reveraed direction. We liN', howovcr, a few 10Uthen1 vegetable fonns on the mountains of Domoo and Ah)-.inia. 1 IIW!)JCCt that this preponderant migration from north to 1011th iJ due to the greater ext<>nt of lnnd in the north, an1l to the northern fom11 luwing existed in tbei~ OWII homes in greatl·r numbcl'8, and l11,ing 00ll3C:'<)_nently lx'<·u aJ. ,,.,ll('N\ through Mtural k'lection and COOlJICtitiou to a hij!IW·r ttage ofperft-'(!tioln or dominating po~l!r, t1180 the 10uthem fumu. .\nd thus. when they becam~J rom· miuglNI during the Glneial period, tl1e northern fuma were enabled to beat the lri!IIJ JIO~·erfuliOnthem forms. Ju~t in the 18We lll.lllnner M we eee at tilC )JI"(''I('nt day,

380 GEOGilAPlliCAL DlSTRIBt."TlOX,

that w•ry many European productioll!l co,·er the ground in La Plata, and in a le~r degree in Australia, lind have to a ecrtain extent beaten the natives; whereas extremelv few southen1 fonns have become natnroliscd in tmy 1~rt of ]~llrGJX', t!Jough hides, wool, ami other objects likely to ('flrry soo:la have been largely im­ported into Europe during the lnst two or three cen­turies from Ln Pinta, 11ml during the last tl1irty or forty years from Au~trolia. Something of the Slime kind must haw occurred ou the intertropical mountains: no doubt before the Glnciill period they were stocked with endem ic Alpine forms; but thesc hal·e almost ewry­whore largely yielded to the more dominant fonull, genernted in tho larger areas and more efficieut work­shops of tl1e Jlorth. In many islands the nn.tive JltO­

ductions nro 11early equnlle<l or el·en outnnmbered by the natnrnliaed; and if the nntives have not been nctu­nlly extenninnte<l, thei r numbers have been grently reduced, nnd this is tl1e first stage to"·anla extinction. A mountain is an isl11nd on the lund; and the inter· tropical mountains before the Glacial period must have been completely isolated; and I beliero that the pro­ductions of t!Jeile islands on tl1e land yielded to those produ~ within the larger arens of the north. just in the MnHl way ns the productions of real islands have everywhero lately yielded to continentnl fonns, natu­rulised by man's agency.

I tun fur from supposing tl1at ull difficulties are r('­

ll\0\"('':1 on the 1'ie1v here giren in regard to the rung-e and affinities of the allied species which live in the northern 11nd southen1 tempernte zones and on the mountains of the intertropical regions. Yery man~·

ditliculties remain to be sol red. 1 do not pretend to imlicate the exact lines 11nd 1neuns of migrntiou, or ll1e reason why certain species and not others ha1·c migrnted;

lr\ Th•· CnmpiPtP Wor~ of Charle~ Darwin Onl;ne

Dt:"HI!\0 TilE OLACIAI, PERIOD. :.181

why certain lt~iea htn·e IJcen ll!Odifil'd and hn,·o b-ircu riile to nf'w b'TUII!III of fonns, and otlw111 luwe remain('(). unalt<'rcd. We c•fmuot. hope to e.1plaiu such facts, until we can MY why one BJ)('('ie!l and not another 00-oomMI naturaliicd by num'a Rb'('uey iu a foreign land; why 0110 mn~t t.wioo or thriffl 11.11 fn.r, n.nd is twiM or thrice lUI common, 11.11 another specic11 within their own homrs.

I hn.,·e I!Did thnt numy difficnltif'.ll remnin to be 110h·OO: somf' of tho m08t n'lllflrkablo are stat<'<! voitl1 admirablf' clcanw<li! by Dr. llooker iu hi.i botanical works on tlw nntaretic regionJJ. 1l1f'lle caunot bo lw>re dil!cu.,•.•d. I will only lillY thnt 11!1 far as n'f.,'llnLi the occnm:•n<'e of ido·ntical ~])('(!i<'s at pointa 80 cnonnously n·mottl Ill!

Ke'l,'11CI•·n Lnnd, New Zealand, and Fncgia, J hclie,·o that to'llllr<M the doee of the Glacial period, icebetgll, llll ~>ttggct~ted by Lyell, bft,-e been lall,<ely coneen~t:d iu their disper1111l. nut the exitltencc of sewrnl quito di~tinet speeie~, belonging to genem ucluaivdy confined to tho south, at thriK! and other distant points of tlto 10uthen~ hen1isphe"', is, on my th•'Ory of dht(.~·nt with modifiration, n far more reUJIU'kable C88C of diftio•tllty. For somo of tht>ec epcdes are 10 ditltiuct, that 'IIC cannot bllp(XlbO that. there hM been time ~oinee the eunmwncc­lllf'lll of the Glacial period for their migration, and for tl1eir su~uent modiflen.tiou to the nOOl'ssaty d~'W'CC· Tho fll('ta seem to mo to iudieato that 1)6-I'Uliar aud l'('l)' di&iuct species h.a,·e migrntt'd in radi ating liu68 Crom aome common ('('litre; and I am in­dined to look in the 110uthen1, till in the northPm hemi­sphere, to u for111er uud wnnncr period, l>eforo till' com· m('nrement of tho Gh10inl period, whrn tho nntnrctie lnn!ls, now cowrcd with iee, suppof'WI:I a highly peculiar and isolated flora. I 81~>-lM!d that before this ftom wna utenninatt-d by the Glacial epoch, a few fomlll were

._ ___ ..., ____ 0~-k ..:hanoiN; Da!Win llll'l..

382 OEOORAPHICA.L OlSTIIIBUT!OS.

widely dispersed to yarious points or tho aouthem hemisphere by oeeas.ionnl meanB of transport, and by t110 aid, as halting-plaees, of eJ.i~ting and now woken island!!, and perhape at t110 commencement of tho Glacial period, by icebergs. Dy theao menWI, lUI I be­lic,·c, the southern sl10res of Amerien, Australia, New Zenl,md have become slightly tinted by tl1o same pecu­liar forms of vegetable life.

Sir C. Lyell in a striking 1~ has speculated, in language almoet identical with mine, on tho effects of b"'\!ilt alternations of climate on geographical distri­bution. I believe that the world has recently felt one of his great cycles of change; and thnt on this view, combined with modification through n.aturo.l eeloction, o. multitude of facts in tl10 J)fell<'-ut distribution both of tho aame and of allied forms or lifo can be ex­plained. Tho li1•ing wnten may be aaid to have flowed during ouo ~hort period from tl1o nortl1 and from tho iiOUill, Mel to IIBvo CI'OBBCd at tl1o equator; but to ha.l'O flowed with greater force from the north so as to lml'O freely inundated tl1o south. Aa the tide leaves its drift in horizontal Iince, tl1ough rising higher on tho ehores where the tide risca highest, so lun·e the liling waters left their Ji,•ing drift on our mountain­summita. in a line gently rising from the aretic low­lands to a great height under tl10 equator. The ;arious beings thualel\ stranded may be compared with s1wage races of man, dri\•en U}l and sun·i\·ing in tho mouutain­f1Ultnc88C& of almost every land, which scn·o as a. record, full of interest to us, of tho fonncr iuhabitantll of tho surrounding lowlands.

ha mo~ W rk o Ch • n r ... ; rlnln,..

C!t&r. XJI, FHESII·WATEU PUODUOTJOXS. 383

CHAPTER XII.

Distribution of fresh-water productiOWI- On the inhabitant. of occnnicillandt-Abeenoeofllatrl(:hilllll!landofte!Tl'lltrialMam­mRII-Ontborelationofthoinhabitan~ofillnnd•tothOIIeof thenOIU'CIItmninlaud-On coloni•tion fromthencart'llt-auroe with •nblrqucnt modification-Summa:ryoftbe l11.1t andJ>ro­IIWtchApten.

A.s lakes nml ri\·er-systems are sepnmted from ooch other by barriers of laud, it might ba,-o boon thought that fresh-wnter productions would not ban) ranged widely within the Bnmo oom~try, and o.s the 1100 it ap­parently n. still more impassnblo barrier, that they never would have c:lteuded to distant countries. But the enso is oxnctly tho reverse. Not only hnvo tunny frosh-wntcr Bpcoios, belonging to quito diflCrcut classes, an cnot·mous ntngc, but alliecl epocica prevail iu a rcmnrknblo manuel' throughout tho world. I well re­member, when flrat collecting in tho f.rcali wntcrB of Brnzil, feeling much surprise at the similarity of the fJ'CIJlt-water insects, shcll.a, &c., and at the disei.milarity of the surrouuding terrestrial beings, compo.rcd with th080ofBritain.

But this JKIWCr in fresh-water productions of ranging widely, t110ugh so unexpected. can, I tJUnk. in most cases be CXJllnincd by their having become fitted, in a mnnner highly ueeful to them, for short nnd frequent migrations from pond to pond, or from stream to stream ; and liability to ";do dispersal would follow from tills enpncity 119 au nlmOBt neecst!O.ry consequence. ""e can hero ootlBider {lnly a few cases. In tCf,'i\rd to

© h r f Is r i

38 I OEOOIIAPUICAI, lHSTitiDl."TIO'I".

fish, I bdim·o that the so.me SJlCeiC!I no\·er occur in tho fresh waters of di..itant continents. llut ou tho 8Rme continent tho species often mub>c widely nml almost eapriciowtly; for two riwr·i!Jllltlll.ll will ha\·o some fish in eommou and 110me different. A few facts seem to fa,·our tho J)()ll!l.ibility or thl'ir ()(_Uljional tran.'l-­port by IU'Ciclentalmeans; like that of the lh·e fbh uot mrely dropped by whirlwiuda in India, and the \itality of their om when remo\·ed from the water. But 1 am inclined to attribute the disJX!.raal of fre,.b-water fbh mainly to sl4:ht changes within tho rooent period in the len•! of tho land, luning eauae<l ri,·era to flow into each othf'r. LlStances, also. could be gi\·en of thill luu·ing occurred during floods, without auy chango of le\•el. We Jun-e e\·idenC\l in tho loe811 of tho Hhine of considerable chauboe8 of Je,·el in the land within a ,·cry re<'('llt geologieul period, nnd when tho surface wo.s peoplt'(l by exi~t ing lnml and frcsh-watcr shelL!. 'l'ho wide diffcrcnoo of tho fish on O)Jj)()8ito sill,~s of con­tinuous motmt,lin-rnngeg, which from nu enrly period mti.St lm,•o puted river-systems nnd completely pre­vented their in08Culntion, seems to lead to thill Bt11no

concl~ion. With respect to allied fresh·1111ter fish ot-eu.rring at \·cry dbtant points of the world, no doubt there nre many CMC8 which cam1ot at pl'(':l('nt. 00 cx­Jllained: but some fresh-\\uter fil!h belong to wry anrirnt forms, and ii1 auch CtUICII there will han:- been ample time for great geogra.IJhieal eh.auges, and con­Bequently time and mea11S for much mign\tiou. Ju tl~e aerond place, snit-water fish cnn with care be slowly accustomed to Ii,·e in freah water; and, aooord.ing to \'RlcndellllCII, there iii hardly a ainglo group of fishes confined nclush·ely to fresh W'llter, eo that we may imagine that a marino member of a fresh-water group might traYcl far along the shorce of the sea, and sullec-

Fn&~lJ-WA.T£R I'RODt:CTIONS. 3&)

qut>ntly berome modi8ed and adapted to the fresh watertofR distant land.

Some S]MlCi{'fJ Of (!1!8h-water ShelliJ hl\\"0 a Yery wide rnnge, and a.Ui,'<l. species, which, on my theory, are de­I!C'endOO from a common parent and mnst lun·e Jlrooeeded from a sin,z;le aource, prenil throughoul the world. ~'heir dbtribntion at first perplexed me much, R8 tht>ir 0\'8 RN not likt>ly to be tmnsported by bin4, and they arc inun.-dia.tely kill('() by sea lll'ftter, 88 are d1t' adults. I C()U](J not en~n understand how 110me naturnlised Spe<'io·s )18,·e rapidly spread throughout tht> Mmt> country. nut hro facts. whieh J lun·e oL.!cn· •. ·d-and no d•JUbt mAll)' other~ remain to be ob.,..:n-00-throw IJOJn~;~ li~ht on this aubjt_'Ct. \\l1..-n a duck audd.·n1y emt'l'{;\'8 from a pond ('<wered with diK'k-weoed, l haYe twil-ellet'n tiK'fiO little Jllants adhering to its bark; and it Ma hnppeued to JUt', in remo,·ing a little duf'k­Wl'('(l from ono aqtw.rium to another, tlw.t 1 Jw.,·e quite nnintc'ntionnlly stocked the one with fresh-water shell.il fro111 t he other. Dut rmother ngency ii:l perhll]l8 more efti:ettw.l: 1 SUSJK'Ilcled a duek's feet) which 111ight represent th0110 of a Lin! slcejJing in a natnrnl pond. in an aquarium, where many 0\'8 of fres!J-wnur ~hei!JI w..-ro hatching; and l round tlw.t number• or the ex­tremely minute aud jllilt batehed aheU. crawled ou the Ct•('t, and dung to them 10 firmly that y,·ben tak~·n out or the water they could not be jnrred oft', dJough at R I!Ome11'bat moro adnmN!d age they would Yoluutarily drop on: These jn.:~t hatched moUU!1C8, though aqtuttic in tht'ir Jutturc, survired on the dnek's f~X:t, in damp air, from tweh·c to twenty hour~; and in d1is h:ngth of tim~> n duck or l1eron might fly ot leaat six or &e\'eu hnmlred mile11, nml would be sure to alight on a JlOOI or rindet, if blow-n acro&8 sea to au oreauic blaud or to any otht'r d.i,;tant point. Sir Charle~ Ly..-11 aJ..o

8

380 OEOORAI'UlC.U DllrrRIDl.'TIOS.

infonn1 me that a Dyticul hRa been caught with an Ancyhw (a frei!h-water shell like a limJICt) fmn.ly ad­he ring to it; ~~.nd a water-beetle of the 8fl.me family, a ColymbctCI, once flelll· on boord the 'Beagle,' when fQrty-lho mile6 dif!tant from the nNU1'8t land: how mneh farther it might have flown with 11. ftwouring gale nooneeuntcll.

With rei~pect to J:dR.ntll, it baa long been kno"ll what enonnone rangoa rnauy freeh-wnter and even marsh· BJICCie& haw, both o,·er contincntll and to tim most remote oceanic island!. This if! strikingly Bhown, 8.8

remarked by Alph. de Candolle, in large gronp!l of tcrrcetrial Jlla.nts, which have only a ,-ery few aquntie membert; for these latter aeem immcdintely to acquire, as if in consequence, a very wide mnf.,<e. I think fuvoUT· able meiUlS of disJJel'Sfll explain thil fact. I ha,·e before mentioned tlmt earth ocrosiouaUy, though mrely, ad­heres in 80me qtmnlity to tho ff!et o.nd beaks of birds. Wading birds, which frequent the muddy edges of poudd, if suddenly flushed, wou.ld be tho most likely to lun·o muddy foot. Birds of thil order I can show arc tho greatest \l'ftndQrers, and arc occas.iOillllly found on the m011t remote and bamou illamb in tho open ocean; tlu>y would not be likely to al..ij:!;bt on the su.rlace of the BCtl, 80 that tlm dirt would not be washed off their feet; when making land, they would be sure to fly to tbf.ir natural fi'C6h-water haunt& I do not believe that butllnislll aro aware how charged the mud of ponds il witl1 8IX'd.il: 1 hrn·e tried ac,·crol little upcriments, but will hero give only the m011t striking case: 1 took iu Fcbnmry three table-flpoonfuls of mud from three dif· fcrent poin~ beneath water, on the edge of a. little pond; this mud when dry wcighrd only G~ OW\{'(.'8; I kept it awered up in my study for a.ix montha, .tmlli.ng up and counting each plaut 11.1 it b"''CW; the plautll "·ere

e, ; .e C lmolete Work of Charle~; Oarwll'l Onlio.

o( many kinds. and were alt~tllcl' 537 in nwulot>r; and yet the viacid mnd was all contained in a breakr...t cup I Cooaidering thNe facti, J thi..uk it would ~ an inexplicable circ~tance it water-binlll did not trau­port the lf!eda or l're8h-water planu to \-..&l diiltanct.'ll,

and if COlU!e<Jnently the range o( thc!ell pla.nta was not rcry great. The Mille agency may have oome into Jllay •·ith the egg. ol 10me of the amalJur fl'elh-ntt>r aniatalL

Otber and unlmo11'11 agenci•'l prol.bly ba\·e aL,o playN a J•rt. 1 ha,-e stated that fresh-water fulh c.t 10me kinds or IC«ls, though t~y rejcet many otlltr kind. nfter hiwing 81l'8llowN them ; even small fu;h ,_now eeedl of moderato me, 11.11 or the yellow watel'­lily audPotamogetOIL HeroD! and othe.r binD, ~nuuy after t"entury, have gone on <laily devouring fish; they then take Right and go to other waten~, or are blown 8.('1'011 the &ea; and we luwe IM.'ell that eoods retain their power of gem1inntion, when r<'jettcd in pcllote or in ezcrement, mnny honl'fl nfterwarde. "'ben 1 III.W thfl great size of the 11(!('11.& of that fine ~llter-lily, the !\c.>lumbilml, and remc.>mben'(l AI)Jh. de Caudolle'• I'(_\.

markt on this plant, J thought that ita ditotribntion mnift remain quite i.nczplii"Rble; but Audubon atah~t tl-.at he fo1md the ee«U of tlw> ~t 10utbem water· lily (probably, IW.'eOnling toDr.lJookcr, tbeNelumbium lnk'um) in a beroo'• etomach; although I do uot lrnow the fao:·t, yet analogy makee me belie'fe that a ht•ron 8Jing to another pond aud getting a hearty mMl of fla!h, would probably rejeet from ill &tomat'h a pell<'t tvntAiuing the .00. o( the Nt-lumbium undi~ted; or the teed~ might be dn>Jlp!'d by the Lird ··hil~t r ..... ling itt young, in the l!&llle way u fWl are kno1111 10m~time1 to be dropped.

In COil&iJcring dw. le'feral meana ol d.iatribution. s2

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388 G£00RAT'IIICAL DlSTniBCTIOS.

it should be remembered tlmt when n pond or stream is first fonnc<l, for instance, on a rising islet, it will be unoccupied; and n single seed or egg will\un·c a good chnnoo of IJ\Jccceding. Allhougb there will always boa llln1ggle for life between tl1e indiYiduals of the spceies, how;n·cr few, already OC'Cnpyiug any JKmd, yet aa the number of kinde is small, oompnred with those on the lnm~ tl1e romtJelition will Jlrobo.bly be less IIC\'ere between aquatic than between terrcstrinl species; con­scqu('ntly nn intnlClcr from the waters of n foreign country, would Jnwo n better clmnoo of seizing on a plaoo, than in the case of terrestriill colonjgt& " 'o ~hould, nL!o, remcml>cr thnt some, perhaps 1nany, fresh· water productions a.ro low in the acnle of nature, and that we ha\'O reason to belie,·e that surh low beings chango or become modified leti8 quickly than the high; nnd thiB will give longer time tha n the un~rngc for the migrntion of the 81\me nquatic specicr!. We should not forget the probol.Jility of many species hiiVing fonnerly rouged as continuously ll8 frcsh.water ]Jroductions ever ctm rouge, o1·er i.tnmellll6 nreiUI, and ha,·ing 8Ubsequently become extinct in intcnnediate regions. But the "ide dinribntion of fi'Cflh ·water plants and of the lower animals. whetl1er retaining the same idrutical form or in some degree modified, I bclic,·e mainly depends on the "ide dispef11nl of their seeds and egg~~ by animals, more especially by fresh·lfate r birds, which luwe large powers of flight, and nntumlly tmvel from one to another nnd often distant piece of water. Nntnfl', like a careful gardener, dull! takes her scros from fl bed of n ]JOrticular nature, and tlrops them in another equo.lly well fitted for them.

0" tlte Inlwhitant~ uf Ocemdc Itlandt.-We 11ow come to the last of the tbroo cln8ies of facts, which I

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OCEA..''HC ISLAXD;I. 389

Jun-o seJootcd ns pre!M!nting the greatest runouut of diffictilty, on tho l'iew that all tho indh·idunlB both of tho SDmo and of allied species Jun-o deK-end('(l from a single Jlt\rent; and therefore have all proce«led from a common birthplo.cc, notwithl!tanding tlu1t in tho conrso of time they hnvo come to inhabit distnnt points of tl1o globe. 1 have nlreudy stat-ed that I cannot ltonestJy admit }~orbcs's view on continental extensions, which, if legitiumtcly followed out, would let«! to tho bclief thilt within tho recent period 1111 eJ:.isting islunds lmYo been nCilrly or quite joined to t10me continent. 'l'hia view would remo\"0 numy difficulties, but it would not, I think, e~ploin all tho facts in regard to insular ])roduc­tion& l n tho following reDlllrb 1 slmll not confine myself to tho mero question of dispcrsnl; bnt ~lmll consi(ler some other facts, which bear on tho truth of tho two theories of independent crention and of de~~Ceut wit h modifkation.

'l'he species of all kinds wiUch inhabit oceanic islands aro few irl number comjlElred with those on equal con­tinental areas : Alph. de Caudollo ndmitll tltis for Jllont8, and \\" ollu.ston fo r insecta. lf we look to the large size and \·aricd stations of Now Zealand, extending owr 780 miles of latitude, and comJlElro its flowering plants, only 7,j(l in number, with those 011 an equnl area at tho Capo of Good llopo or in Au.,;trnlin, wo must, I think, Jl(hnit that something quito iudcpendently of nnydifTI!renoo in physical conditioua lms caU&C<I 80 great n di!1Crenoo in number. }:,·en tho unifonu county of Cambridge liM 817 plants, nml tho little islAnd of Anglesea 71H, but a few ferns and n few introduced. plAnt~ aro included in theso numbers, and tho com­po.rison in t!OillO other respects is not quito fnir. We ha\'C el·idenoo that tho barren island of Ascension aborigitmlly J)()8iJCf!Sed under lmlf1\-dozen flowering

____ ll'"I:,;C ;JO!eteWork.;,f ies; ;-w100r..lllll

8!)(} OEOORAPHICAL Dl.STRlBl.'TIOS". C'KAP. XII

J>limt.t ; yet many ham become naturalilled on it, u tlwy ha\·e on Xew Zealand and on en!ry other ooeani<.- island which tan be named In St. Helena there is reason to beJ.K.,·e that the naturalised plauta and animals ha\"e nearly or quite extemtinated mlllly native production& lie who adtnita the doctrine or the Cn:'ation of f'ft('h Be)lftrft(O BJM!<'i('l, 'Aill ha\·e to admit, that a sufficient llllmber o{' tho beet ada)Jted plana and Animals have not been c!'l'flted on oceanic islands; for man has uuintentioually stoek~l them from \·ariollil 110ur·ces far more fully aud perfectly tlw.n baa nntul'(>.

Although i11 OCl'flnio islands the number of kinds Of inhabitant& is ICftllly, the proportion 0£ endemic apeei011 (i. t. th0110 found nowhere cl.ae in the world) is oft('n extn:-mely large. Jfwe colllpnre. for instan<X', the number of the endemic lund""'hclls in l\f11deim, or of the Cll(lmnic birdll in the Galapagos .An·hipelag'o, with tho number found on nny CQntinrnt, nnd then compnn:­thl' area of tlte islmHis with tliRt of the continent, we @hll ll llCe tlmt this is true. ~'his r.\Ct mi~ht luwo IJecn CJ:Jl{!Cied ou my t11rory, for, lUI already explain~!, ape­l'iOIIO!'CilSionnlly arriving After loug intcrn1ls in R new Rllll isOlated di.ltriet, and }m,·ing to compete with new R8110Cintcs. will be eminently liable to mi.Xlificalion, and will oft.en Jlrodnee group~~ of modifi('(l dCil'endant& But it by no mean! follows, that, because in an island nearly Ill the speeiee of one clus arc peculiar, th011e of another ('laM, or of another IICCtion or the 8RD16 class, are pe<'u­linr; nod tiW dift'crenoo I!Cl'ms to dcpcml on the rpecil'il which do not become modified haYing immigrated with fndlity and in a body, 110 that their mutne.l ~laliont1 ha,·e not been much didnrbed ThM in the Gal11pago1 Islands nee.rly every land-bird, but on1y two out of the ele\·cn marine binls, are peculiar; and it is obvious that

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C..a.r. XII. 391

marine birda could arrh·e at tl1C8e Wanda more MSily than land-bird&. Bennuda, on the other hand, which lief! at about tho ~~~orne distance from North .America 8.8 the 0RiftJJag01 h.lnnda do from South America, and which hll.B l\ rery peculiar 110il, does not JXlMCfl8 one endemic ltmd bird ; nnd we ln1ow from Ur. J. :u. J ones's nd­mimblo account of Bemmda, tJmt \"Cry many North American birds. during their great annual migmtioiiiJ, visit either periodically or O('Cflllionnlly tl1is i!lnnd :aradoira dOCB not JKI8i:leSS one peculiar bini. and many European and African birds arcalm011t e\·ery year blown there, fiB I am informed by Mr. E. \T.llaroourt. So tho.t tbCIJO two islands of Bermuda and l\ladeira have been stocked by birds, which for long agee hare struggled together in their foru1er homes, and Jun-e btwmo mutu­ally a.dapte<l to each other; and when eettled in their new homCfl, each kind will ha\·e been keJlt by the others to their proper places and habits, and will consequently have been little liable to modification. ?i[adeim, again, is inhabited by a wonderful number of JlCCU.I.inr land­shelh, wherciUI not one SJlCCiCfl of &C0.-6hell is confined to ita Bhoret: now, though we do not know how &ea-6heUs arc dispeJ'IIC<l, yet we can see tl1nt their e~ or larrr, )JerhaJl8 attached to ll!!aweed or fl~ting timber, or to the foot of wading-birds. might be tmruq)()rted fnr more eMily than lnnd-llhella, aero~~~ three or four hundred mi!Cfl of open IK.'tl. The different orders of inae<!ts in ?!Ladeim appal'('ntly present analogoll8 faet8.

Oooanic islands !Ire somctimeB deficient in certain dll.SSCB, nnd th('ir places are nppnrcntly occupied by the other in.hnbitnntll; in the Gnlapngoa lslandB reptiiCfl, and in New Zealnud gigantic winglC88 birds, take the pln.c!(' of mammals. In the plants of the Onlapegoa lslnnds, Dr. Hooker h..ea s.hown that the proJ)()r1ion.nl munbers of the diff~reut orders are very different from

392 GEOGRAPIJIC.\L DISTIUBliTIOS".

wl1at they nre clsowhore. Such cases arc ~nerally ilc­couute<i for by tho pl1ysical conditions of tho islo.nds; Uut this c..xplcmatiou seems to me not a little doubtful. :Facility of immigmtion, I believe, lms been at lell.St as important as the nature of the comlitions.

Manr remarkable little facts eould be gin:n witl1 respect to tho inhnbitnnts of remote isltmds. For instance, in certain islands not tenanted by mallllllals, some of the endemic plants htwo brontifnlly hooked seeds; yet few relationa are more striking tl~.·m the adaptation of hooked seeds for trnnsportal by the wool and fw· of q1llldrnpods. ~'his case Jlresents no difficulty on my view, for a hooked seed migllt be tronl':ported to an island by some other meall3; nnd the Jllnnt then becoming slightly modified, but still retaining its hooked seeds, woulcl fonn 1m endemic species, lun·ing ns useless nu nppendnge ll.S any rudimcntnry orgon,-for instance, ns the shrivelled wings nuder tlw eoldrred elytrn of' many insular beet lcs. Agniu, islands often possess trees or bushes belonging to orders which el.sewhcro include on.ly hcrbnceons species; now trees, as AIJlh. de Can­dolle has shown, genemlly have, wlmtever tho CflllS6 may be, ctmfined nmges. llenoo trees would be little likely to reach distanL oceauic islands; and au herb­aceous plant, though it would ha\·o no cha1100 of successfully competiug in stature with ~~ fully deve­loped tree, when eatilblished on an island and having to compete witl1 llcrbacooJIS plantJ; alone, might readily gain an ad,·antage by growing taller and taller and overlOJlping tl10 other plants. If so, JJUtural selection would often tend to add to the stature of herbaceous IJlants when growing on an islam~ to whatever order they belonged, and thus comert them first into bushes and ultimately into trees.

With respect to tim absence of whole orders on

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Cll.t.P.XH. 303

occnnic isL:m(l$, Dory St. Vincent long ago I'(>JU!\rked thnt Bntmchinllll (f%"!:!, toods, nc\11&) have never been found on any of tl1e runny islands with which the grrot OCCfl.llll are studd(!(l. I have taken pains to verify till~ nsecrtion, and 1 IIA,·e found it strictly true. I htn·e, howe,·cr, been assured that a frog exists on the moun· 1Ains of the great island of New Zcnlnud; but I suspect tllAt thiB exce}ltion (if tl1e infommtion be correct) may be explained through gl.acinl llb'\'IICy. ThiB b'('ncml ab8enl'C of frogs, tooda. and nE'wtB on so many oceanic islnmls cnnnot be accounted £or by their physirol ron­ditions; indeed it eecrns that islands are peculinrly well fitted for these nnimnla; for frogs IUJve been introdut'C{I into ~fadeiro, the A:r.ores, and lf1111ritius, and have multijllied so ns to btx'Qme n nuisance. But RB tlwsc animals and their fl]lnwn are known to be imme<liatdy killed by sea-water, on my ,·iew we can liCe tbnt there would be great difficulty in their tmnsportnl nci'088 the sen, nnd therefore why they do not exist on nny oceanic is\a!l(L But why, on the theory of e~1t ion. they should not !UJ\'O been created there, it would bo YC!)'difficulttoe:rplain.

M.nnuuals offer nnotbcr and similar case. I IIA\·e cnrcfully senrehed the oldest Yoynges, but !UJvo not linishl'(l my senl'(;h ; na yet I lm,·e not found a single instan('C, free from doubt, of n. terrestrial nlllnuual (excluding domesticated animab keJlt by the nntiYcs) inllAbiting an island sit\lated aboYe 300 miles from a continent or great t:ontincntnl island; and many islnnds si tuAted at a mueh Jess distance arc cqllfllly l:mrou. 'l'ho Fo.lklnnd Jalands. which nrc inhabited by a wolf­like fox, come nearest to nn exception; but this group ('8nnot be considered as oceanic, ll8 it lies on a bo.nk ron· ncctcd with the mnin.Jand; morc<m!r, icebergs fom1c rly brought boulders to its westen1 shores, and tl1cy may

'3

_____ ""'_ ..... ....,,on,.,

30-! OI:OOR.WRICAL DtSTltlBt7riON.

hnYo formerly trnW!portcd fo:o;cs, as 110 frequently now hntlpt:.'US in tho arctic n>gions. Yet it cannot be suid that small Wands will not ~upporl small mammals, for thf'y OI.'Cur in many tJRrts of the world on ,·ery slllilll isl!uuls, if cl0110 to a rontinent; tlnd hnnlly fin island Cl\n be nnmed on whif'h our srnall!'r qundn1pcd.'1 llfl\·o 110t become nnturoliscd and greatly multiplied. It cannot be said, on the onlinary view of creation, thnt thl'rc bas not been time for the l'rcation o£ mam­mals; many ,·olcauio islnnds are sufficiently ancient, as shown by tho stupendous dcgrndntion which they hnxe suffered and by tl1eir tertiary strata: tl•ere lm~ also been time for tho Jlnxlnction of endemic specie~ belonging to other el.as8l's; and on rontinents it is thought that mammals aJlpcnr ami dii!tlppMr at a quicker mto thnn other nnd lower animaLs. 'Though terre~trial mammals do not oocur on l'lCCilnio islnuds, nCrialmammn.ls do oceur on nhnost e,·ery island. New Zen.hmd l>OSIM'SSCs two bnts found nowl1ero elso in tho world: Norfolk bhmd, the \"iti ArclUpclngo. the Bo!Un blnuds, the Caroline and ll11ritlnno An:'hipelng<ll'!J. and ~lauritius, all poe!lCSS their lX'Culiar bat& Why, it may be Clsket~ has the suppoeed creatiYo foroo produced Lats and no other mammuls on rcmol(l islands? On my Yiew this question enn ensily bo answered; for 110 terrcstrifll mammal can bo tnmsportetl acl"'M a wide srlftce or aca, but bats eon lly across. Jlats ha\·e been aeen wandering by day fnr O\'er the .\tlantic Ocean; and two North .-\merican species eith<!r rcgnlnrlr·or OCCilsionnlly Yisit Jkmmdn, at the distance of 600 miles from thr> nminlaud. 1 hcCir from Mr. 'l'omes, who has specially stuclietl this £11mily, that many or tho !!limo speeica ha\'O enonnous mnges. and Bffl found on c.'Onti­nenta ancl on far distant isltmds. Hence wo Jm,·o onk to l!llp]lOflC that suc\1 wandering spc<!iea hCI\·o been modi-

fled tlm)llgh Mtoral &eledion in their new homes in relation to tl1eir new positio11, and we ('ftll undentand the pre&enoo of endemic bali! on islands, with the ab-8CUOO of nll tcrreBtrial mammal&

nesides tiJO ab!icnoo of tciTClltrinl!IUlmmnla in rela­tion to tiro remotcne88 of island.. from contirl(!nt.s, tlrero is nlso a relation, to a certain extent indcpeudcnt of db;ianC<', between tho depth of tiro 8Ca 8Cpnrating an island from tho neighbouring mainland, nnd tho pre--111!1100 in both of the same mammifcrons speeiea or of allied Bpe<>iea in a more or 1C8i! modified comlition. :i\r r. Windaor Eorllw made BOrne Btriking obeen-ations on thi.il head in regard to the great Malay ArdUpelago. whieh is tm,·er&ed near Celebes by a 11pace of deep ocean; and this ll(.l&Ct' ICJJQmtca two widely di>~tinct mammalian faunna On either side tho island.11 are situated on moderately deep eubn111rinc bnuke, and they are inhabited I.Jy closely allied or idcnti('ft] qundrupedl!. No doubt BOmo few anomalies occur iu this great nrdU­pelab.-o, and there is much difficulty iu fonning a. judg­ment in 110mo caaes owing to the Jlrobablc 1w.turnliAAtion of rertniu ummrnals through Jllftn'll ageney; but we 11lmll IIOOil Jw.,•e mueh light thrown on the natural hil;tory of this archipel.a,<ru by tire admirable zeal and reeenrrhesofi\rr. Wallace. llw.,·euotaaycthadtimeto follow UJl this subject in all other qnartel"'l of tbe world; but as fnr as lJm,-e gone, the relation genen1lly holds good. We llCC llritain sepamte<l by n shn!Jow clmnnel from Europe, tmd the mmJJmals are the 8fllllO on both side8; we meet with analogous fncts on many islund11 !lepnmted by similar channels from All>~trn l ia. The West Indian llllnndsstand on a dcejlly suluncrge<l bo.nk, neurly 1000 fnthoma in depth, and here we find American fonns, but the «pceie11 and c,·en tho gtoncm are dU;tinet AA tho amount of modi6caC.on in all eruJCe depends to

ha mp~ w.,,.y () r:h

306 OEOOI\Al'DICAL DTSTlllDI..l!Ol<.

a certain d~ on the lapse of tim<', and as during chang<'ll of lt•\·el it i11 ob,ious that iftiandslll•JJOmtc<l by shallow channels lire more likely to hn\·e been eou­tiuuously uuit<'d within n. re<'ellt p<'riod to the maiu­J.o.n,J than islamls llf'Jiflmted by d~JlCr chAmlPl~ we rnn undPrstand tl1e flt'<]uent rclntion ll<'twNn thP (iPpth of tlK' ilea and tl~ dl•grN' of affinity of thP mammali11n inhabitants of i>!IRmis with thot!e of a neighbouring con­tinent,-an incXJllil'l!.blo relation on tho licw of inde­JI<'Udent nctsofcr('fltion.

All the foregoing remarks on tho inlmbitants of OC'Canic is.IRml>~,-nRmdy, the ~~earcity of kinds-tho ril'hncss in <'ndcmie fonus in Jlftrlicular dnSFJ('s or sec­tioll8 of diU!i!ell,-lhe alw>noo of wl1ole groups, fllJ of bs.tmchians, 811(1 of l<'rrestrial mamma Iii notwithstanding the preacnce of aCrinl bats,-the singular proportions of ('l('rtain orders of Jllant.s.-herbnceous forms }m,·ing been d"w·lope<i into In:'('~ &c.,-accm to Ill(' to flCCQrd better with the view of 01'('1\Sionnl means of transport having ~n latg('ly ellicirnt in the long courso of time, tlmn with the \'iew of Rll our oceani(' islands lutdng been formerly oonn('('te<l by oontinumm land with tl1e nearest continent; for on this latter vipw the 111igntlion would probnbly ba,·e h<'en more COWJ)Iete ; and if modifi­cation be w:lmitt{'([, all the fonn!l of life would lu"·e bi:!eu more equally modified. in accordunoo with the vuromouut importance of the relation of orgnuis.m to orgnnis.m.

r do not ck>ny that there are many nud gnwe dillt­eultics in under11tanding how several of t11e inhabitants of the 111oro remote islands., whether still retaining the 118me s~ifie fonn or modified sinee their arrh·al, could lllwe reaehed their prc~~ent home& nut the ))robahility of many Wands lmving existed as halting-places, of which not a wreck now remains, must not be over-

OCEANIC ISLANDS. 307

looked. I will here give o. single instance of one of the cases of difficulty. Almost all oceanic i~lnnds,

even tl10 most isolnted and smallest, arc inhabited by land-shells, generolly by endemic species, bnt eometimes by SJlC<'ies founcl elsewhere. Dr. Aug. A. Gould has given eewral intere~ting caaes in rcgard to the land­shells of the islands of tho H~eific. ~ow it is notorious that Jnnd-shelh nro ,·cry easily killed by Mit; their egw-. at least suf'h as 1 hnYe tried, sink in aoo-wnter nnd nro killed by it. Yet there must be, on my ,-iew, some unknown, but highly ellieient means for their trnns­portal. Wou1d tl1o jnst-lmkhed young ()C('liS:ionnlly era.wl on and adhere to the f(!(!t of birds roosting on tho gr01md, and thus get tmngported? Jt oceurr«l. to me tiVlt land-shells, when hybcmating and ha,·iug a membmnous diaphragm O\'Cr tbe mouth o£ the shell, might be flooted in chinks of drifted timber acl'Q88 modemtely wide anus of tl1e een. And 1 fotmd that SC\"Cml species did in tl1is SllllO withstand uninjured an immersion in sea-water during sm·en days: one of these shells was tho lleli.x pomatin, and after it had again hybcnmted I put it in sen-water for twenty days, and it pcrf(!(!tl)' reeo,·el'(!(l As this spccif's has R

tl1iek calcareous operculum, I rcmo,·ed it, and when it lmd formed R new mcmbnmous one, I immersed it for fourteen days in sea-water, and it recovered und cmwled away: but more experiments nrc wanted on this hcrul

'l'he most striking 11nd important fact for us in l'('gEird

to tbe inhAbitants or islandg. is t!Jeir affinity to those of tile nearest mainlan<~ without being actually tho snme species. Kumerous instances oou1d be gi,·cn of this fuct. I will gi,·o only one, that of tllo Galapegos Arehipelago, situated under the equator, betw(!(!n 500 and 600 miles from the shores of South America. llero

308 GEOOR.U'DICAL DISTRIDUTIOS.

ahn08t ev-ery product of the land ami water bears the tmmi.stakeable stamp of the AmeMn continent. 'l'bere nro twenty.&x land binls, and twenty-fi,·o of these are ranked by ?lrr. GouM as distinct species, SIIJl]lOied to luwe been created here; yet tho cloeo affinity of m011t of tll(l9(l birds to Amerioon spociCIJ in e,·cry chnrnctcr, in their lu1bits, gestures, and tones of,oice, wil.8 mani­fest. So it is \lith the other animals, nnd with nearly nil the Jllnnts, ail shown by Dr. Hooker in his ndmimble memoir on the Flora of this archipelago. 'l'he lllltn· ralmt, looking at tho inhabitantil of tiiC80 'l'"olcanie islands in tl10 Pacific, distant &eveml hundred milCfl fl'Oln tl10 continent, yet feela that !10 i.s stuuding on American Lmd Why sbou1d tl~ be 80? why should tho IJIOC.iea which arc 1mppo!!Cd to ha,·o beeu created. in tho GalaJiil.go& An:hipelago, and nowhere else, benr 80

)linin n IUI.IllJl of nflinity to th086 created in America? 'J'hero i.s nothing iu the conditjonl! of life, in the geo­logical n.nturo of the i.elnnda, in their height or dimotc, or in tlto !lTOJlOrliou.s in wbjcb the aev-en1l classes ore a880Ciate<l together, which re8C.'mble1 ei08Cly the con· ditions of the South American coost: in fact there is a conaidemble dli!sllnilnrity in all th('&e reapecta. Ou the other hand, there is a conaidemble d('gree of re-8C.'mblanoo in the Yolcanic nature of tb(' BOil. in climate, hf'ight, and Bi~ of tlte islauda, bct.11·('(>n the Galapagoa and Cape de Verde Archipelagos: but what an entire nncl nbeolute difference in the ir inhabitants! 1'he in­habitants of the Cape de Verde lslnnds are related to thoee of Africa, like th086 of the Gnl•lllil.g08 to America. 1 IJelie,·o this grand fact can TCC('ive no 110rt of upla­lltl.tion on the ordinary view or independent creation; whel'Cil.l on tllO view here maintained, it is obvious that the GalaJiil.go& Island.& would be likely to rccein~ eoloniilts, whether by occasional means of tmna:tlOrt or

oc:a: ... -L~IO ISL.-ums. 390

by formerly continuous land, from Americn; and the Cn)Je do Venle Islands from Afriea; and that 1meh colonist& would be liable to modification ;-the princiJlle of inheritllnce still betraying their original birthplace.

:Many analogous fncts cou1d be gil'cn: indeed it is an nlm06t universal mle thnt tho endemic productio1111 of islnmlsnrc related to thoeo of tho nearest continent, or of other ncnr islands. 'l'he exceptions nrc few, and m08t of them eun be explaine<l 'l'hus the plants of licrgu£~1cn Land, though standing nearer to Africa than to ... \mcrica, arc related, and that ,·cry ci08Ciy, tliJ we know from Dr. llookcr's aceo1mt., to thoeo of America: but on tho view that this island hll8 been mainly stocked by IIC(!(ls brought with eanb ami ltoocs on icelwf!tS, drifted by the tJre,·ailing curn>nlf\ this n.nomaly dis. RJlJlClll'8. New Zealand in ita endemic Jlhmts is much more cloecly rclntcd to Austmlia, tho nearest mainland, tluon to any other region: and this is wlu\t might have l.JC<>n eXJlCC'te<l ; but it is nlso plninly rotated to South America, whic\l, although tl1e next JlNlrcst continent, it liO enormously remote, that tho fnct becom('8 an anomaly. J3ut this difficulty almoA disappcan on the ,·icw that both New Zealand, South America, and otlll'r southcn1 lands were long ago )Jnrtially stocked from a nearly intcnnediate though di~;tllnt point, namely from the antarctic islands, wbcn they were clotlW'd with ,·egetatiou, before the commencement of the Gla­cial tJCriod. Tho aftinity, which, though feeble, J am 1188Uf('(\ by Dr. Hooker is real, bctwC<ln tho f\om of tho south-western corner of Austmlia and of the Capo of Good H ope, is a far more remarkable cnec, and is at prciJCnt incxplienblc: but this nftinity is confined to the plnulf\ and will, I do not doubt, be some day ex· plain(!(\.

'l'hc law whieh causes the inhabitants of an archi-

400 OEOOJLU>UICAL DlSTniUt'TIOS.

pelA~ though ll)~ifkally di~till('t, to be ciOIK'ly allied to t)u"'(l of tb4:1 nf'fl.rest contilwnt, we 10n1etimes see di$J>layed on a s:mnll IJC81<', yet in a m08l intt:reatiug nuHlner, within the limits of the ~~nme ftl'('hipclngo. 'fhtl8 tho fl(ln:>ml islands oftlw Gah1pog:011 Archipelago are tennntro, as 1 luwc elsewhere ~hown, in n qui to mnn·<'llOtl8 nmnncr, by Yery d06<'ly rdnted &J)('Cies:; IJO that the inhabitants: of each llf!pRr>lte ll!lnnd, tl10ugh m06tly distinct, are related in an incompnmbly cloaer d.-grce to each other than to the inhabitants of any other 1•rt of the world. And this i! ju.,t what might han~ been expected on my ,·iew, for t.ho is:lnuds arc situawd 10 near each other that tbey ~·ou1d alm08t ~rtaillly reet'i'l'"e irmnib"f''lnts from the fll\me origiWil IJOUJ"C(', or from each other. Unt this diAAimilarity betwC('n 'the endemic inhabitants: of the islands may be tl8l'<i f\8 an argument ngain&t my ,·it'"'~; for it maY bo fl8kNI, how hll8 it happened in tho ecwml illlanda &itunkd wit hin aight of each other, hnving the 81\lllC

geologirol nature, the 81\me height, climate, ,\:c., that many of the immigrants: should hare been diiTereJttly modiflrd, though only in a 1mall dch"l'e('· Thll! long ap))('fln"d to me a great difficulty: b11t it ari.!es: i11 chief )Jart from the deeply«ated error of considering tho phy&ical conditioiUI of a country lUI the m08t im· JIOrtRnt for iLl inhabitants:; whereas it cannot, 1 tl1iok, be disputed that tho llflturo of tho other inhnbiumts, with which each hall to comJX!le, iw at least lUI iln JIOr­tant, nnd gcnero.lly a far moro imJIOrtnnt element of SW'('(!II!!. Now if we look to thoee inlmbitnnl8 of the OnlJI)Jtlgoe Archipelago which 11ro found in other 1)1\rts of the world (laying on one side for t ho moment the endemic species:. which cannot bo hero fi1irly included, 11.!1 wo are oon&idering how they have come to be modi­fied linoo their arrim1), we find. a considerable amount

The ....;.molete Wort..o f Char1 Darw&.l onw~~--

OC'EASIC ISl.A.."DE!. 401

of {liffercnco in tho &e\·emt islands. 'l1ris dif'l"crcnoo m ight ind~ hnve ~~~ expected on the view of the islnndl! luwiug been stocked by occasional menus of tnm.sJKJrt--o. seed, for instance, of one Jllant Juwing becu brought to one k!land, and that of another plant to IUlOtlicr island. 1 [enco when in fonner limes nn irnm.igrnnt acttled on nny one or more of the islunds, or when it snbeeqncntly sprcftd from one island to another, it "·ou.ld undoubtedly be expo8C<I to different conditiollB or life in the different il!lnnds, for it would haxo to rom pete with difl"t'rent sets of organ.i,;ms: n plnnt. for inllllHwe, would find tho bc~t-fitted ground more per· fectly OCCII]Jied by di...tiuct Jllants in one island than in another, and it would be expoeed to the attnck11 of 110mewhat different enemies. lf then it mried, nnturnl selection would probably fiwour differcnt mrieties in tho different islands. Some species, howo,·er, miglrt spread and yet retain tho smno character throughout tho group, just lUI we BOO on continents aomo species spl"(>ading widely nud l"(>mniu.ing the same.

'l'he rcully surprising f>lCt iu this case of tho Galn­£1'lb'08 Archipclngo. nnd in a lesser degree iu eomo analogous in.:;tances, is that tho new species fonned in tho IJ('(lflrRto i:Jall(ls lm\·a not quickly spread to the other islnmls. But the islands, though in sight of each other, !Ire 8(-'J)Hnlted by deep arms of the sea, in most cases wider thnn tho British Channel, and there is 110 renson to sup})()kl that they have at any former period beeu continuously united. The C\llTCJtta of the sea are rnpid aud sweep acnJSil tho nrehipelngo, and gales of "iud are ex.troonlinarily roro; 10 that the islnnda are far more effc<:tually separated from each other than they appear to be on a map. Nc,·erthele118 a good many speci1'8, both those found iu other parts of the world and those confined to the ardUpclago, are common to

102 OEOORAPIIICA.L DISTRIBUTIOY.

the aevcrnl islands, and we may infer from certain fuch that theao have Jlrobably spread from BOme one ialand to the others. But we often take, I think, an erro. ucous ,·iew of the Jlrobe.bility of closely allic<l species im·ading eacl1 other's territory, when put into free intercommunication. U udoubtcdly if ouo species has any admntago whatever over another, it will in a wry brief lime wholly or in part supJllant it; but if both are equally well fitic<l for their own place~~ in nature, both probably will hold their own places and keep separate for almost any length of time. Bciug familiar with the fact that many species, naturalised through man's agency, have spread with astonishing rapidity over new countries. we are apt to infer that most species would tlllls spread; but we should remem­ber that the forma which become llllturnlised in new countriCII are not generally cl011Cly allied to the aboriginal inhabitants, but !lf6 very distinct species, belonging in a large proportion of ca.see. as shown Ly AlpiL de Candolle, to distinct genern. In the Galapagos Archipelago, many even of the birds, though so well adn)Jted for flying from island to island, are distinct on t.>4CIJ ; thus there are three closely-allied species of mocking-thrush, each confined to its own ialand. Now let us suppose the mocking-thrush of Chatham Island to be blown to Charles lsland, which has its own mocking-thrush: why should it Bllccecd in establisl1ing itself there? We may safely infer that Charles Island is well stocked with ils O"ll species, for annually more eggs are luid there than can poeaibly be reared; and we may infer that tho mocking-thrush peculiar to Charles Island is at least as well fitted for its homo as i.i the speciet; peculiar to Chatham Island. Sir C. Lyell and Mr. Wolllll!ton ha,·e communicated to me a remarkable fact bearing on this subject; !lllmely, that Madeira and the adjoh1ing islet of

I W ri< f ~ rwin nli "

Porto Santo posseee many distinct but repf'OJ(!ntath·e lnnd~helts, 80me of wl1ich li1·e in cro,·iceiJ of stone; and although largo quantities of stone are annually trans· ported from Porto Santo to Madeira, yet tl•is latter island hM not become colonised by the J>orto Santo species: nm·ertbelell8 both islands run-e been colonised by aome European land-shells, which no doubt had aome ach·autage over the indigenous S]lecil!!!. }~rom these com;iderotions I think we nood not greatly mar..-el at the Cltdemio aud reprosentative epeeies, which inlmbit the severo! islands of the Galapagos Archipeltlgo, not ha.ving unil·crsnlly sprood from island to island. In many other instancet~, flll in tl1e sel·crol dU.tricts of the same oontincnt, pi"C-OC<!npRtion baa Jlroba.bly played an im)Xlrtant l)arl in chocking the commiJ1gling of &pecies under the same conditions of life. 'fhns, the 80Ulh-eRSt and aouth-west con1ers of Australia haye nearly the same Jlhyaical conditions, and are united by continuous lund, yet they are inhabited by a mst number of dil!tinct nmm1nals. birds, and Jllants.

The principle which df:'termines the generol chal"8("tcr of the fauna and 11om of ocean.ic islands, nnmelv, that the inhnbitauLJ, when not identically the same, )·et are Jllninly related to the inl~t~bitants of that region wl1ence colouiats could mOBt readily lrnve ~n derived,-thc colonists ruwing been subsequently modified nud !Jetter fitlcd to tl1eir new homcs,-is of tho widf'st npplicu­tion throughout nature. " 'e soo this on e\·ery moun· lain, in e\·ery lake and ma111h. For Alj)ine species, exeept ing in so far all the l!aroe forms, ehi{'fly of j)lantll, luwe spread ·widely tluoughout the world during the roocnt GlncW epoch, are related to thoee or the sur­rounding lowlands ;-thus we hin-e in South America, Alpine humming-birds, Alpine rodents, Alpine J)lant.s, '~c., all of strictly American fonna, and it is obl'iOWJ

---~...n~.~-'ole t w 1< c.f :h- 11"

40 l 0£00RAPIIICAL OISTRI BI.:TlOY.

thnt a mountain, n11 it became slowly UJlhen,·e<~ would naturally 00 eoloniscd from the ~urrounding lowlnnds. So it ~ with the inhnUitanl;l of lake11 oud marshes, excepting in 80 far M gt'(!at facility of tmn11p0rt hn.s gi,·en the llmne ~neral fonn11 to thl.\ whole world. \Ve see this so. me prindple in the blind nnimale inlutbiting the ctweg of America ami of J~urope. Other tmnlogous facts could 00 gi\·en. And it will, I bclicn.,, be uni­wrso.lly fmmd to be true, that where'fer in two n>gions, let them be e,·er 80 distnut, •ntmy closely allied or re­presentatinl species Ottur, there will Likewise be found 80me identical spe<'ies, showing, in accordnnoo with tJ1o foregoing 1·iow, that ut aomo fonucr period there hns been intereommunicatioll or migration between the two n"gioll8. _\nd where'fer mnny closely..ellicd !<peeies occur, there will be found mnuy fonns which some nntural.i.sts nmk as distinct species, and 801Jle fill ,·aric­tics; thC!!e doubtful fonns showing us the steps in the Jlrocessofmodifleation.

This n"lntion between the power and extent ofmigrn­tion of a specietJ, either at the Jlresent time or at some fonner period under different pll)'ilieal eomlitions., and tho existence nt n"moto 110intil of the world of other species all.ie<l to it, ~ 11hown in another nnd more t:,-eneral 'my. Mr. Gould l'(!marked to me long ago, that in those genem of hirdi! which mnge O'fer the world, many of the 11)Jeeic11 ha\·e n.,ry wide nu1~ I can hardly doubt tllEit this mle is g.:nerally tn1c, though it would be diflicnlt to pr<we it. ..lmongst mammals, we liCe it strikingly displayed in Bats, nnd in a leeecr degree in the l<'clidro and C~tnid.w. Wo 800 it, if we eomporo tho distribution of bnttertlice and beetles. So it ill with most freah-wnter productions, in which so llUiny b"Cuem mnge m·er tho world, nnd many individual11peciea ha,·e enonnoll!l nmgcs. It ~ not meant that in world-

Charles Dena:~'-----

mnging g<>nCI'Il all the ~>tJeCiee ha\·6 a wide mnge, or 6\"('U that they htn·e on an a~rag. a wide mnge; but only that eome of the spe<:ies mnge ,-cry widely; fur the facility with which widely·rnnging spedes vary and gh·e rise to new fonns will largely dctennine their a,·ernge rnnge. .For instance, two mrioties of tho same speciea inlHLbit America and Europe, nml tl•c spooiea thus hal! nn immense mngo; but, if tho,·arintion l•nd been alittlo grenter, tho two mrietie~~ would luwo been ronked na dis­tinct 8]>eciea_ and tl•e comJuou mngo would bn,·e been grootly reduced. Still less i3 it meant, that a II)Jeeies whid1 a)lj)fl~ntly has the Cll.)JQCity of ei'Oiilling Le.rrienL and ranging widely, as in the easo of certain powerfully· winged birds, will necessarily ron~ widely; for we should U('\"er forget that to rongo wid··ly imJJiies not only tho po"·er of ef08Sing barriers, but the more im· portant power of being victorious in distnnt lnnds in tho stnL,I!glo for lifo with fordgu nBlMX'intes. But on tho ,-icw of all tho spedes of n genus hnviug de­dNLoended from a single parent, tlJOugh now distributed to the mOO remote points of the worl1~ wo oug-ht to find, and 1 belie,·e aa a generol nlie we do find, that &eme at least of the I]JeCiee muge ,.e11· lli•iely; for it is nect"SSI\1)" tlmt the wunodified parent should rouge llidely, undergoing modification during ita diffu~ion, and should )>lACe itse\C under di'l"el"80 conditions fa'l"onrable for tl•e oon,·er'Sion of ita off,-Jlring, firstly into oownrie­tiee &II() ultimately into new ~J~Ceies.

ln <:onsidcring the llido distribution of certain genero, we should benr in mind thnt some nro extremely nncicnt, and mtlBt hnvo bmJlched off from n common po.rent nt a remote opocl1; so tl111t in su<'h cases there will llll\"C been ample time for great dim.ntalnnd geogrophicnl ellllngel and for acciclents of traU$jXlrl; and oolll!C­quently for the migration of some of tbo IIJ>OOiCS into all

'----~;,.._.__,..,;.,-"lo!ete ••· 'k f ie'

406 GEOO R.\l'UICAL DISTRIBUT IO~'.

quo.rters of the world, where they may have become slightly modified in rela tion to their new conditions. '!'here ill, al110, some reason to believe from geological evidence that organisms low in the BCale within each great cla&l, genemlly change at a slower mte than tl1e higher forms; and eonacquently the lower forms will have had a bet ter chance of mnging widely ami of still re· taining the same specific character. 'J~his fact , together with tho seeds and eggs of many low forms being very minute and better fitted for <listnut transportation, Jlro­bably accounts for a law which has long been observed, and which baa lately been adlnimbly diseUSI!Cd by AI ph. do CandoUe in regan! to plants, nnmcly, that the lower any gron1J oforganislll8iil, the more widely it is ll}Jttomnge.

'l'he relatiollll just diBcnssed,-namely, low und slowly­changing organisms ranging more widely than the high,--60me of tho species of wi<lely·rnnging genern thcmseh·es rnnging widely,-oruch foots, us alpine, lacll.s­trine, and marsh productions being related (with the excetJt ions before specified) to thoee on the surrounding low lands and dry Ianda, though the116 stations are so different-the very elose re lat ion of tho distinct species which inhabit the islets of the same archi!M!lago,-and esJM!<:ially the striking relAtion of tl1e inhabitants of each whole archiJM!lago or island to those of the nearest maiuland,--are, J th ink, 11tterly inexplicable on tho ordinary view of the independent creation of each S]M!· cie~, but aro CXJJliooble on the ''iew of colonisation from the nearest a11d readiest souroo, together with the subsequent modification and better adaptation of the colonists to their new hon~es.

Summary of laft and pretent OhapUrr.-In t he110 chapters 1 h.e. ,'e endeavoured to show, that if we make due allowance for our ignorance of the full effects of all

f) Th"' Complete WorY of Charle~ Darl"in Onl;n,

C11u. XII. 107

the changes of climate and of tho le,·el of the land. which have certainly occurred within the recent period, and of otlu!r similar ehan.,<>eB which may hne occu.rred within tho same period; if we remember how pro­foundly ignomnt we ace with re11pect to the many and curioUil n\eallll of occaaiona.l transport,-a subject whi(.'h has hardly over been properly experimentised on; if wo l>ear in mind bow often a spe<:ies may Juwo ranged continuously over a wide area, and tllen llaYe become extinct in the intermediate tmeta, I think the diffieuhiCB in beliering that all the indi,·idnals of the i!ll.lllC speeica, where,·er located, Jw,·e d('ll('('nded from the wme pnrontll, are not insuperable. And we are led to this oonclu.sion, which ha.il been arrin!<l at by many naturalists under the designation of lingle centres of creation, by aome general oonsidemtions, more especially from the importance of barrieN and from tile analogical distribution of sub-genem, genem, and fiunilics.

W itl1 respect to the distinct species of the same genus, which ou my tboory must ha,·e spread from one pareut­BOnrec; if we make the same allowa.n001 t\8 before for our ignorance, and remember that aome fonns of life chango most slowly, enormous periods of time being thus granted for tllCir ntigrntion, I do not think that tho difficulties are ill.Silpemblc; though they ofieu are in this case, an<l in that of the indi,·idunt. of the .same spe­cies, extreme! y grn ,-e.

1u exemplifying the effoctil of climatal changes on distribut ion, I hare attempted to show hOw important lm11 been the influence of the modem Glncinl period, wl1iell I am fully convinced simult.nnoouely affected the whole world, or at least great meridional belts. As showing how di,·ersified aro the means of occasional transport., I hare di&cussed at 801ue little length the meo.m of dispersnl. of fresh-water production&

108 GEOORAPIIICAL DISTRIDUTION.

If the difficulties be not insuperable in admitting that in tho long course of time the indi\·iduals of tho aamo 11peciet. and likewiliO of nllied speciefl, have pn> eoo(}od from some one 110uroo; then lthink nll the grnud leading f[l('ti of geographical (!istribntion nro eJttllicable on tho theory of migration (gcnen11ly of tho more do­minant formll of life), together with subsequent modifi· cation allfl tl1C multipliootion of new fonn& We can thus understand the high importrulCC of barriers, whether of land or water, which aepamte our &l.weral zoological and botauicn.l JllOl"inccs. We can thtu undentand the locali!llltiun of llllb-gencm, genera, and families; and how it d that under dil'f'ereni latitndee., for iJ\J!tanoo in f'outh America. the inhabitanti of the pla.i.Jl& and mountains. of tho fon'lt.i, marshes, and desert.11, are in ao mysterioull a manner linked together by affinity, o.ud aro likewise linked to tho e.~tinct beings which fonncrly inhaUitcd the AAmO continent. lleariug in mind tlmt tho mutual rein· lions of organism to organism aro of tho l1ighe~t import­RUe<', we Cll.ll aoo why two IU"OOII having m•nrly tho MillO J•hysi<"'ll conditions should ofteu be inhabited by ,-cry different form.ll of life; for acronliug totheltngthoftimo wb.i1•h haa elnpscd since new inlmLitanta entered one regi011 ; nceonling to the nature of tl1C oommuniootion which allowed certain fornlil and not oth~>rs to enter, either in grrotl'r or I!!8Ser numben ; according or not, as tboee whid1 entered liappened to oomc in more or ICM direet competition witb eacb other and with the aborigines; nnd ncrordi~ lUI tho immigrnnta "·ero ropnble of vary· ing moro or 10811 ru.pidly, there would ensue in different regions, independently of their )lhysieal conditio1111, infi. 11itely di,·ersified conditions of l ife,-thero wou1d be an almost endless runonnt of organic action and reaction,­ancl ""0 ahould fwd, 811 we do fiml, &Ome groups of beings greatly, and aomo only aligbtly modilied,--«m1e de,·e-

loJM><l in grrot for('(', IJOme existing in I!M'a:nty numbers­in the different grt."at geographical l'""·incee of the world.

On thNJe BRmC prinl'iplcs, we ean understand, 1u1 1 luwe cndrarourod to show, wiLy oecnnic i~lands alLould han• f~·w inhnl!itant.~ Lnt of thr~ !l great number should be endemic or peculiar; and wiLy, in l'(']ation to the m<>ans of migrntion, one group of lx>in~ evNL within the lllllll<' d11.~~. should hru·e 1111 itil I!Jl(l(•i,... <'lld('mie, anrl another ftroup 11hould h:we all it.i! S]l('f'ics common to oth•·r qnartrn of thl' 11·orld. We ('tl.LI IJI'IoC wh~· whole gnnLJ>'~ Cof o~niarns. as batrnchinn~ and I(!I'TMrinl mam­mal~~, llh<mld be absent from OI."C81li<· i:Jim(ls, whil;rt the mOo<t i:10lated i~lnnds IIO!SiJeSS their own JMl('t!liar species of nCrial mammals or bnUI. We can IK'O ~hy there ~:~hould be 1101110 rt'lation hetween the presence of mnmmall'l, in a more or !('88 modified condition, nml tho depth of tho !!('a l.ot•tweeu nn island and tho main land. \\'o can r lenrly !1('{1 why all tho inlmbitnnts of an nn:hipelugo, though spc'<'ifienlly diatinet on the sc\·eml i~]('IS, should be clo,.dy rdntt'd to each other, and likewi..;e be rolntcd, but lea rlOoM'h•, to t]u)!;e of tbr> noo.reat oontinrnt or oth('r IIOUI"CC whr>nf'C immigrants w~rc Jlrobably dr>ri\·ed We t'flll 1'('(1 why in two areas, howe,·<>r di4aut !'rom I'RCb other, tl\l'rc l'llould be a correlation, in the J•n..,....n('(' of id~nti<'Bl sperics, or l"ari~tics, of doubtful ~j)('('i('ll, and of di<tin('t but representative spe('i~.

As the late .Edward Forbes often inllisted, there is a llfriking pamllelism in tho lnws of lifu tlLroughout t ime and ~JIII('(l: t he laws govcn1ing t ho suect''lOiiOn of forms in past times being nearly the MillO with th080 b'OY('riLing at tho Jlre&ent ti111e tl1e differcn~ in dilf~rcnt nrctll!. W e 8l'6 thit in many fllCta. 'l'he l'nduran('e of I'RCh species and group of species is continuo~ in ti111e ; for tho cx~ptious to tbe rule arc IJO few, that tl1er may

T

410 GEOGllA.PlllCAL DISTitlllUTION.

fairly be attributed to our not lla\·ing aa yet disco'l"ered iu an intennedinte det:nrit the forms which are therein absent, but which occur alxwe and below : 110 in space, it certainly is the general rule that tl1e areo. iJJha­bitod by a. single species, or by a group of species, is coutinuon.s; and tlw exceptions, which aro not rare, may, asl have attcm]Jted to show, bo accounted for by migrntion ot some former period under dill'ercut con­ditions or by occasional means of truusport., and by the species having become extinct in the iutermedinte tmcta. lloth in time and space, species and groups of species ha,·o their poinUI of maximum doYelopmcnt Groups of spocics. belonging either to a certain period of time, or to a certain area. are often characterised by trifling cba­racten in common, as of iiCnltJture or colour. In look­ing to the long succession of ages, as in now looking to diatunt provim,"eS throughout tho world, we find thnt somo organisms differ little, whilst others belonging to n dinCrent class, or to a different order, or oven only to a (lin'orcnt family of the same order, differ greatly. In both limo and space the lower members of ea.ch class gencrnlly change less than the higl1er; but there are in both <lfLSC!I marked exceptions to the rule. On my theory tl1ese se,·eral relations throughout time and space nro intelligible; for wbetber we look to tl10 foi'IIU! of life which ha\·v changed during I!UCcessh·e ages within the same quarter of tho world, or to those which ha,-e chnngcd after ba\'iog migrnte<l into distnnt quarters, in both cuscs tl1e forms within each clnsa Lave boon con­Jlected by tl10 JIDme boncl of ordinnry generation; and the more nearly any two fonns nro relnted in blood, tho nwrcr tl1oy will geuemlly stand to cnch otl1cr in time and spuce; in both casea the laws of \'llriation ha\'e been tho snme, nnd modifications hare ~n nccwnulated by tho 81lme power of natural selection.

©The Comolete Work of Charles Dar i lin

411

CHAPTER Xlll

i\[UTOALArPili"LTI.UOr0IIOAl<IOIJEJl<(ll: lfORI'UQI.OOf:

EJ<UII'rOLOOY: lluLH.III!IM'ARYOIIO.ue.

Ct.A!'""I<:'IoTLO:s, 11:1'011]• aubordina«! to group~-1'\'atunU IJ·atem-1\ul"*' a"'\ difficuhi"" in dauificali(ln, explained oo th the.xy of detocnt with modification- ClaMi6catioo otvarieti01- Deaoent ahnyautedinduo.i6catioa-Analofcicalor..Japti.-echan>cters - AffinitiN. ~tt'Lieral, complex Uld r.diatin~t- Extinction a~I.M aod delina grou[lt- MOIU'uOI.()(IT, bet"'OIIl'II D>f'Jllben or tl>~> arne eta., bet'«t'fl 1•ru or the ame indi.-idual­•=•uvowtn,luoaof,uplaiiiO!Idbyvariati<,.,.D<>I.IIIUJil'f\'euing atanarlylll;f!,and being inherit& at a o:'>.on'ei]!OOdingage­ll~ni.II&!IT.t.IIT o&O.ose; their origin uplaiOO!.I - bummary.

FnOll the first dawn of life, nil organic beinga are found to resemble each otl1er in descending degrees, flO that they Cilll be dussed in groups under groups. 'J'Jtis clnss.i· ficatiou ill evidently not arbitro.ry like the grouping of the stars in const.ellntioll.!l. 'l'hc exi.stenoo of groups would lun·e been of simple signification, if one group had been f'xclu.aively fitted to in1laLit tl1e Lmd, and another the water; one to feed en Jlc.;h, anolher en ,·egetable matter, and 110 en; but the case is widely different in nature; for it is notorioUB bow commonly members of evcu tl1e 81\me sub-group Juwo difiCrcnt habits. In our &l'OOlld nu<l fourth chaptef'll, on \" ariation und on Nutuml Selection, I hu1•e attempted to show tlwt it is the widely runging, tho much di!l'used and common, that is tho dominnut species belonging to tho lnrgcr gcne:m, which mry lll06t. The ,·nrieties, or incipient species, thllil tlrodu.ced ultimately become oom·ert.cd, as I bclicl'e, into new and (lilltinct speciee; and theec, on the principle of iuhcritnuce, tend to produce ether new il.nd dom.inant

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