172
31R. A . R. WALLACE O N THE ZOOLOQICAL
grey ; veins black ; pobrachial vein forming an obtuse angle at its
junction with the discal transverse vein, tlie latter very oblique, parted
by little more than half its length from the border, and by nearly thrice
its length from the priebrachial transverse ; lialteres uhitisli. Length
of tlie body 24 lines; of the nings 4+ 1‘ines.
Pam. PIIOKTDX, I€aZicZoy.
Geu.
PIIOltA,
Latr.
2338. PHORA
B I P A S C I A T A , n. s . Frptn. Atra, subtus flavescenti-alba,
antennis fulvis, abdomine lanceolato, fasciis duabus apice pedibus
halteribusque flavescenti-albis, pcilibus posticis aigris basi flavescentialbis, tarsis intermediis nigrirantibus, alis cinereis.
Female. Deep black, yellowish white beneath ; antennae tawny ; abtlomen lanceolate, much longer than the thorax ; sides elevated, a broad
basal yellowish white band, and a narrower one be~oirdtlie middle,
tip also yellowish white ; anterior legs and halteres yellowish white,
middle tarsi blackish, hind femora with the basal half yellowish white ;
wings cinereous, veins black, pale at the base ; costal vein ending at
a little beyond half the length of the wing ; radial cubital, praebrachial,
and pobrachial veins parallel and equally distinct. Length of the
body 2-2t lines ; of the wings 5-6 lines.
On the Zoological Geography of tlie nlalay Arcliipelago. By
ALFREDIt. \VALLACE, Esq. Comniunicated by CHABLES
J)ARWIN, Esq., F.K.S. & L.S.
LRead NOT.h l , 18.59 ]
IN Jlr. Bclater’s p a p 011 tlie Geographical Distribution of Birds.
read before the Limean Socicty, and published in the ‘ Proceediugr’ for February 1858, he lian pointed out that the western
islands of the Archipelago helong to the Indian, and the easterii
to the A4ustralianregion of Oriiitliology. My researches in thehe
,,ouiitries lead me to bt4ieve that t h e same tLi\isiou ail1 holcl goor1
In t’kery branch of Zoology ; aud tlic ol),jcc.t of lily preseut COINniunicatiou is to mark out the precise limits of each region, and
t o cull attention t o some inferences of great general importance :IS
r e p r d s the study of’the laws of organic distribution.
The Ruvtralian and Indian regions of Zoology are very stroiigly
contrasted. I n one thc Marsupial order constitutes the great mass
of the rnammalia,-in the otlicr not a solitary marsupial animal
exists. l f a r s i i p d s of at least two genera ( c t ~ s c u sand Bezidexs)
are foulid dl over the Moluccas and in Celebes; but none have
LiEOURhl’llT 0 1
rill, 31 \ILLY
AILCHII’CI~ACIO.
1 73
been detected in the adjamit ialaiids of J a w and Boriico. Of all
the varied forins of QuwilTi.uticnt?rc,C‘arnivom, Insectivora and Rumiizantia which abound in the a e d ern half of the Archipelago, the
only genera found in the hloluccas are Parndoxurzis nud cerercics.
The Xciuride, so numerous in thc western islands, are represented
in Celebes by only two or three species, while not oiic is found
further east. Birds furnish equally remarkable illustrations. The
Australian region is tlicl rirliebt 111 the woi-ld in Parrots ; the
Asiatic is (of tropical regionh) tlitl poorest. Three entire families
of the Psittacine order nrc peculiar to the former region, and two
of them, the Coclratoos ant1 thc Idories, extend up to its extremi~
limits, mithout a solitnq sj)t~icdpaSaing into thc Iudian islands 01’
the Archipelago. The griinr Palroi.wis is, on the other Iinnd, confined with equal strictiicw to thcl Iudian region. In the l i s a o r i d
order, the PJaasioniiI~are I i d i n i i , the Ne~ynpodiidc~
A u s t r a h n ; but
in this case one species of’ c~rclifhinilp just passes the liinits into
the adjacent region. Tlic gtwus Y’ropidorkynchs, highly chiiracteristic of the ,4ustrnliaii rcgioii, aud cveryn licre abundaiit as well
in the Moluccas a i d Nev (2~1ticaas in Australia, is quite 111111nown in Java aud Boruco. On the other hand, the entire faniilics
of Bucconida, Trogonic-lu.and Phyl/ornithicke, and the genera Pericroeotu8, Pic?aonotzis, 2’rwhop~iorzis,Ixos, in fact, dmost all the
vast family of Thrushes :uid a liost of other genera, ceazpe abrupt11
at the eastern side of Bornc.o, Jnva, and Bali, A11 these groups
are eowizofi birds in tlw great ludian islands ; they abound everj where ; they are the cliar:ic+c&tic feabures of the oruithology ; and
it is most striking to a nalural~st,on passing the iiarrow straits of
Macassar and Lombock, sntldtdy to miss tlieiu entirely, togetlier
with the Quadrumam niid Fditl(c, the Insertiz*orn a i d Rorlriatza,
whose varied species lxoplu tlir forests of Sumatra, Jma, and
Borneo.
To define exactly the Innits ol‘ the two regions nhere they art’
(geographically) most iiit 111ia
connected, I n ~ i iillention
~’
tlint duringa few days’ stay in ttrc islmitl of Bali I f‘ou~idbirds of‘the genera
Copsyckus, Xegalniirta, l’/yu. J’Juwzis, :ind X t i i i - i i o ~ ~ n s t oall
i ~ ,c1i:irLi(ateristic of the Jiidiim rvgioir and abundant in Jlnl:zcca, Ja\ a, nu0
Borneo ; ~rhilc011 croasiiiq c n (‘rt o LoinboCk, d~iriiigthree iiioiitlii
collecting there, not oiic of‘ tlicui I\ el er s e ~ ;n licither Iiit\ c the!
occurred in Celebes iior in any of the more castcrii i&mcia I ha1 v
visited. Taking this in coiinesion with the fact of Cacntua, 15-012dorhynchus, and Jftycyodius having their western limit in Loinbock, ~e ma!- considcr it esinhlishrd that the Strait of Loml~och
15 1
MII. 9. R . WALLACE OY THE ZOOI~OOICAT,
(only 15 miles wide) inarks the liiiiils and abruptly separates tu o
Tlrc Pbilippinr
14:iiids are in some rexpccts of tloubtfiil loration, resembling and
difc~irigfrom both regions. T h y are deficient in the varied
INallnnals of Borneo, b a t they contain no Alarsupials. The Psittaci
arc scarce, as in thc Indian region ; the I~oriesare altogether absent, but there is one representative ofthc c'ocl~atoos.Woodpeckers,
Trogons, and thc geiicra Lros. f70pqc.hics, a i d Ploceics are highly
c11nr:icteristic of India. T'%rny+fPra and ilIeynpodius, again, arc
A n s t rdirtn forms, but these beein represented by only solitary
spccies. The islands possess also a felri peculiar genera. W e
mnst on the whole plxcr the Pliilippme Islands in the Indian region,
but n i t h the reinark that tlicy are deficient in some of its most
stribing features. They possew sevcral isolated forins of the Australian region, but by J I O means sufficient to constitute a real
tr.an.ition thereto.
Lcaring the Philippilies out of the quehtion for thv present, tlie
1%
estcrn and eastern islmidx of the Arcliipelngo, as here divided,
belong to regions more distinct and coiitimtccl than any other of tlie
great zoological divisionr of the qlohe Moulli America and Africa,
sep:irated by the Atlantic, do not ilifrr 50 widely as Asia and
Austyalia : Asia with it? abunilnnce and vnridy of large AZnmmals
and no lICarsupials, arid Australia \%ith scarcely anything but
l l a i slipids ; Asia v ith its gorgeous Phafiiccnitke, Australia with
its dull-colourccl Xfynpocliid(e; Asia the poorest tropical region
in Parrots, Australiz the richest : and a11 these striLing characteribtics are almost uniiiipaircd :it tlie r e r j limits of their respective
dihtricts ; so that in a fern hours \\ e may experience an amount of
zoological difference mhich only m&s or c w n months of travel
ill give us in any other part o f th e \+-orld!
Moreover there is nothing in t,lm aspect or physical character of
t h c islaids to lead us to expect such a difference ; their physical
and geological differences do not coincide with the zoological
differences. There is D striking hoinogeneii)y in the TWO halves
oftlie Archipelago. The great volcanic chain run8 through both
parts ; Borneo is the counterpart of Nen Guinea; the Philippincs closely resemble the equally fertile and equally volcanic
Moluccas; while in rastern Java begins to be felt the inore arid
climate of Tiinor and Australia. But these resemblances are
acc.oiripanied by an extreme zoological diversity, the Asiatic and
Aiiatralirtn regions finding in Rornro and New Guinea respectively
thcsir highe<t development.
o r the great Zoological regioiir of the globc.
c . 1 : o c i n L I J I I Y oi
IS
I i i L 4 1 LAY A ~ ~ C I I T P I ; I , . ~ G ~
17.7
Hut it niaj be said : ‘. Tlw scy:imt,ion between these t\+oregion+
n o l so absolute. Tlrtw I S m i i c transition. There are s p e c k
and genera coninion t o tlic eaitcrir and western islands.” ‘l‘liis is
true, j e t (in my ol)inioii) prows no trailsition in the 1)roper sensc
of tlie word ; and the nature :111cl nniount of t h e rcsemblnacc only
show^ inore strongly tlw i h i l i i t e and original distiiictncss of tlie
tn o cli\isions. The cxccptioii I i t w clearly proles tlic rule.
L e t us investigltr tlicwt
e s uf supposed transitioii. I n tlic
western islmds nlniost t l i i . oidy iiietance of a group peculiar t o
h n s t r d i s and l,he e ’rii idaiirl, is the ilI~~qopoditis
in Northwest Borneo. Not
of t l r c 1uhtralinn forins of RIammalin
passes the limits of’ the rrgiorr
( )n the other Iiand, Quadrumma
occur in Celebes, Batcliian, Loinhock, and perliaps Timor ; D e w
liare rcached C(hbcs;, Tlinoi-, HIIIYI, Ccmni, arid Gilolo. hut not
Kcm Cniiiaea ; Pig3 ha\ v c i t i ~ i i t l t dt o New Guinrn, probal)ly tlir
t r u e enatern liriiit of t l i r s p’iius Szis ; Squirrels are found I I J
Celebes, Lombock, and Siiniban i i : among birds, GYnl2zis occurs iri
Celebev and Soiiiba\\ a, Wootlpcc~l~c~rs
reacli Celebes, and Hornbillr cxtend t o the Korth-\\csht of NCT Guinea. There cases of
identity 01- rescinblniice in tlic. nuiriiitls of tlie tn o region4 x e inn:,
groiip into three clnssci , 1 d , identical species ; 211d, c~losel>allied or rcprebentsti\e
I ( > - , : i i i d 3rd, specicxs of peciiliai* and
isolated genera. The coriiiiiiiii U rcj Jlonkey ( M a c a c 7 ~C ? / 7 2 0 7 n O ~ p S )
has reached Loniboc:k, aiitl Lwrliiips Tiiiior, but not Celcbes. Tlic
Deer of the Moluccas seein\ t o bc a variety of the C k ~ u i i ns f 2 s of
Jars arid Borneo. Tlw .I wiglc C’oc~lcof Celebes and Loinbock is a
.la\ anese species. H i i w i i d o y i w i i z i c c i , Zostci*ops j l a u u c , lialcyon
colIciris, Eurystomzbs gulai*ic,~ I l / i c i ~ y yphasianella,
yi~
illcrops j n m nicus, httkrepies lepicln, P t i h o p i i a tiielnnocephaln,
~
and some other
hirds appear the same in tlie aclj.icwit islands of the erlsterii a i d
western divisions, and soiiic of t Iiciii raiige over the \&ole Arcliipelago. But after ivadiii$ L?t>Ilon t h e various iiiodes of dispei-sioii of’ animala, and loolriiig at the proximity of the islands, we
shall fwl astonished, not a t biic.11 an aniouut of interchange of
species (most of vhich a r c bird- of‘ great p o u r r s of lliqht), but
rather t h a t i n the cour;-c’ o f
ii niiicl1 greater and aliiiosi coinplcte fusion l i a ~not t a k r i i 1 ) I a ~ ~Werc
~
tlic Atlantic graduallj to
narrow till only a strait of 1 i\(-iii
> iiiiles separ:itccl Alfi.ica froin
South America, can n e hell) l d i c w n g tliat niaii? birds and i~isectand soine few maninialr M onltl s~wiibc! interchanged 2 Bnt such
interchange would he a fortnit oii< mixtiire of‘ faunas essentially
and absolutrl! (lis\iiiiil:ii., r i o t ;I ii‘itiiml and rc,qiilnr tronsiticn~fruiii
(
5
.
176
BIR. A. R . WALLACE O N TIIE ZOOT,OGICAL
oue to the other. I n like inanner the cases of identical species
in the eastern and western islands of the ,b-chipelago are due to
the gradual and accidental comiiiingling of' originally absolutely
distinct faunas.
111our second class (representative species) we must place the Wild
Pigs, which seem to be of distinct but closely allied species in each
islaiid ; the Squirrels also of Celebes are of peculiar species, as are
the Woodpeckers and Hornbilla, aud two Celebes birds of the
Asiatic genera Phcenicophmcs and Acridotlwres. Now these and
a few more of like character are closely allied to other species inhabiting Java, Borneo, or the Philippines. W e have only therefore to suppose that the species of the western passed over t o the
eastern islands a t 80 remotc a period as on one side or the other
t o have become extinct, and t o have been replaced by an allied
form, and we shall have produced cxnctly the state of things now
existing. Such extinction a i d snch replacement we knoiv has
beeii continually going on. Such has been the regular course of
nature for countless ages in every part of the earth of wliich we
have geological records ; a i d unlcss we are prepared to show that
the Indo-Australian drcliipelago was an altogether exceptional
region, such must have been the course of nature here also. If
these islands have existed in their present form only during one
of the later divisions of the Tertiary period, a i d if interchange of
species a t very rare and distaiit intervals has occurred, then the
fact of some identical and other closely allied species is a necessary
result, even if' the two regions in question had been originally
peopled by absolutely distinct creations of organic beings, and
there had never been any closer eonnexion betneen them than
lion; exists. The occurreiice of R limited iiumber of representativr
species in the two divisions of the Archipelago does not therefore
prove any true transitiov from one t o the other.
The examples of our third class-of peculiar genera having little
or 110 affinity with those of the adjacent islands-are almost entirely
cordhied to Celebes, and render that island i t district per se, in the
highest degrec interesting C$izopithrczcs, a genos of Baboons, the
e~traordinaryBabirusn and the singular rwiiinnnt Ansa depess~cornishave nothing in c'oinmon with A siatic niamiiialh, but seem
nmrc allied t o those of Africa. A quadrumanous animal of t h r
Rime genus (perhaps identical) occurs in the little island of Batchimu, which forms the extreme eastern liiiiit of the highest order
of inammalia. An allird specie? is a l w said t o exist in the Pliilippiues. No\$ this occurrenw of q u a d ~ - i ~ n ~ ainn athe Aiistr:11inir
177
GEOORAPIIT OF TIIE hLiLAY ARCIIIPELhQO.
region proves nothing n hatcvcr as regards a transition t o the
w s t e r n islands, 11 hich, :imong their iiuiiierous monkeys and apes,
have nothing at all reseiiibling tliem. The species of Celebes and
Batcliian have the high superorbital ridge, the long nasal bone,
the dog-like figure, the minute erect tail, the predaceous habits and
the fearless disposition of tlic true Baboons, and find their aKes
nowhere nearer than in tropical Africa. The Anon seems also t o
point towards the saitie region, so rich in varied forms of Antelopes.
I n the class of birds, Cclebes possesses a peculiar genus of Parrots (Prioizitzcms),said t o occur also in the Philippines; Jferopogo?2,
intermediate betiwen an Indian and an African form of Bee-eaters ;
and the aiioiiialous Scissirosfiwz, wliich Priilce Bonnparte places
liest t o a Madagnsuar bird, and forms a distinct subfaniily for thc
reception of tho two. Cclebcs also contains a species of C O ~ C M S ,
which is lierc quite out of its nornial area, tlie genus being othcrwise confined to Africa and continental India7not occurring in
any other part of the Archipelago. The Celebes bird is placed, in
Bonaparte’s ‘ Conspectus,’ between two African species, to which
therefore I presume it is ittnrc nearly allied than t o those of India.
Raving just received Mr. Siiiitli’s Catalogue of the I-Iymenoptera
collected during my Erst residence in Celebes, I find in it some
facts of an equally singtilnr iitlturc. Of 103 species, only 1 G are
lrnowii t o inhabit any of the western islands of the Archipelago,
while 1s are identical. u itli spccics of coutiiientd Iudin, China,
and the Philippine Islantlu, t n o arc stated t o be identical with
iiisects liitlierto k n o 1~1 only froiii tropical Africa, and another is
said t o be most closcly allicd to oiic from the Cape.
Thcsc phenomena of dihtrilJiitiixi are, I believe, the most aiioritalous yet linou-11, atid in fact altogctltcr tinique. I am anare of 110
othcr spot upon the enrlli nhich contaiiis a nuiiiber of species, in
several distinct classes of aiiinials, thc nearest allies to N hich do
not exist iii any of the countrics nhich on every side surround it,
but which arc to be found oitly in aiiotlier primary division of the
globe, separated from tlteni all by n vast expanse of ocean. I n no
other case are the species of n genus or the genera of a fmiily distributed in tzuo distinct arcas separntcd by countries in which tlicy
do not exist ; so that i t htxs collie to be considcred n law in geographical distribution, “ that both spccics and groups iiihabit continuous areas.”
Facts such as these can oiily be esplnined by a bold acceptaiicc
of rast cliaiigcs in the surface of tlic earth. Thcy teach US t h n t
h i s iulanil of Celebes is iiiore ancient tlinii most of the islands
LIWW. PB00.--XOOLOC+Y.
12
1'is
1IR. A. 11. WALLACE OK TIIE ZOOLOG'CCAL
now snrrounding it, and obtained some part of its fauna before
they came into existence. They point t o the time when a p e a t
coiitinent occnpied a portioil a t least of i t hat is now the Indian
Ocean, of vliich the islands of Mauritius, Bourbon, &c. niay be
fragments, while the Chagos Bank and the Keeling Atolls indicate
its former estcnsion eastward to the vicinity of nliat is now the
AL'alayan Archipelago. The Celebes group rcniains tlie last eastern
fragment of this now submerged land, or of some of its adjacent
islands, indicating its peculiar origin by its zoological isolation,
and by still retaining a marked afinity with the African fauna.
The great Pacific continent, of wliich Australia and New Guinea
are no doubt fragments, probably existed at a innch earlier period,
nud extended as far westward as the Moluccas. The extension of
Asia as far t o the south and east as the Straits of Macassar and
Lonibock inust have occurred subsequent t o the submergence of
both these great southern continents ; and the breaking up and
separation of thc islands of Sumatra, Java, and Borneo has been
the last great geological change these regions hare undergone.
That this has really tnlren place as here indicated, me think is
proved by the following considerations. Not more than twenty
(probably a smaller nwnber) out of about one hundred land birds
of Celebes at present lrnoirn are found in Java or Borneo, and
only one or two of twelve or fifteen Mammalin. Of the Maininalia and birds of Borneo, howevey, at least three-fourths, probably
five-sixths,inhabit also Java, Sumatra, or the peninsula of Malacca.
Now,loolring at the direction oftlic Macassar Straits running nearly
nortli and south, and reinenibering we nr? in tlie district of tlie
~noiisooiis,a steady sontli-east and north-west wind blowing altcrnately for about six inontlis each, we shall at once see that Celebes
is inore favourably situ:itcd tlinu any other island to receive stray
pmsengers from Borneo, 11 lictlier drifted across the sea or wafiecl
through the air. The distance too is less than between any of the
otlicr large islnnds ; tlicro arc no violent currents t o iicntrttliLe
the action of the Winds ; and ~iuriiero~~s
islets in mid-cliannel ofer
stations which niight rcscue niaiiy of the wanderers, and ndniit,
after i'epose, of fresh migrations. Between Java and Borneo the
midtli of sea is much greatcr, the intermediate islands are fewer,
and the direction of the monsoons d o n y and not across the J m a
sea; accompanied by alternating currents in the same direction,
must render accidental coniaunication between the two islands
exceedingly difficult ; so tlint nhere the facilities for intercommunication are greatest, the nuniber of species corninon to the two
OEOORAPIIT OF TIIC MALAY ARCIIITPELAGO.
179
couiitries is least, and ricc. versA. But again, the tilaw of ilic
species of Boriieo, Jn\:I, 8c., ~ v t ’ i i\I lie11 iiot itleiitical are co~z.c/eiieric,
whicli, as before explained, iiiilieiitcs iclmtity ai, ail earlier cpocli ;
whereas the great iiiass of tlic thiuia of Celebes is 11-i-idelydiEereiit
from that of the ircsterii iblaiicls, consisting iuostlp of genera, :lid
even of entire families, nltogrtlicr fbreigii to them. This clearly
points to B former total tli\ ersity of‘ foriiis :md specics,-cxisting
siiiiilarities being the result of nitcrinixture, the evtreiiie facilities
for which we 1iare pointed out. l n tlie case of the great western
islands a former iiiorc completc identity is iiiclicated, the p r m ~ ~ t
differeiices having arisen f i m i tlicir isolation during a considerabl~
period, allowing time for tliat p:wtial extiiictioii and introductioii
of species which is the regular coiirse of nature. I f tlie very siiiall
number of western specics iu Celebes is all that the inost favourable conditions for trniistiii&oii could bring about, the completc
similarity of the faunas of the \\ec~ternislands could never (with
far less hvourable conditions) 1i:iic been procluced by the same
meaiis. And what otlier iiieaus (m we conceive but thc former
connexion of those islaiidu with each other and mith the continent
of Asia ?
I n strikiug confirmation of tliis ricw we have physical evidence
of a very interesting natarc.. These couiitrics are in fact still
cosznected, and that so coiiiplctcsly that ail clevation of only 300
feet would nearly double tlie extent of tropical Asia. Ober
the whole of the J:wa Sen, the Straits of Malacca, the Gulf of
Siam, and the southern p:wt ol‘ the Cliiua Sea, ships can aiichor in
less than fifty iitlioms. i\ vast snbninriiie plain unites together
the apliarently dissjoiiitedpar‘tr of the Iiidiaii Loological region, and
abruptly termiiiatcs, exactly at its liniits, in a11 uiifathoiiiable ocean.
Tlic deep sea of tlie lMoliioc~a3miles up to the very coasts of
Nortlierii Boriico, t o the Strait of Loiiibock iii the soiitli, :md t o
near tho iniddlc of the Strait of A1:icassar. M a y e not therefore
from tlicse facts rcry fairly twiic.1 nde that, accorcling t o the s j stein
of alteriiste bands of elcvntiou and depression that seem8 very
gciierally t o prevail, the labt great rising inoveiiiciit of the volcauit’
range of J a m aiid Sumatra I\ ar :iccoiiipanied by the depression
that now separates them froin 13orneo and from the contiiient ?
It is worthy of reniarlc that the I nrious islands of tlie 3Ioluccaa,
though generally divided by n less eiteiit of sea, ha\ e fewer qiccies
in coiiimon; but the Reparating was are in aliiiost erery case of
immense depth, indicatiiig that the separation took place at a mud1
earlier period, The same principle is well illustrated by tlie dis12*
1so
NB. A. R. WALLACE ON TIIE ZOOLOGICAL
tributioii of tlir genus P n d i s c n , two species of whicli (the COUin011 Birds of Piiradise) are found only in Ncw Guinea and the
idands of Aru, Mysol, TVaigiou, and Jobie, all of which are coniiected with New Guinea by banlcs of soundings, while they do
n o t cxterid t o Ccraiii or thc I(& Islands, whicli are no further from
Ncw aninea, but are separated from it by decp sea. Again, the
chain of sinall rolcaiiic islaiicls to tlic west o i Gilolo, though divided
by channels of only ten or fifteen iiiilcs \Tide, possess many distinct
representative species of insects, aiid cvcii, in some cases, of birds
also. The Baboons of Bntcliinn have iiot pnssed t o Gilolo, a mucli
larger iuland, only separated froiii it by a channel ten miles wide,
aiid in one parl almost blocked iq) with siiinll iulands.
Now looking a t these pheiiomcna of distribution, and especially
a t those presented by the fanla of Celebes, it appears to me that
a much exaggerated effect, iu prodiiciiig thc present distribution
of animals, has bccn imputed t o the accidental transmission of
individunls across intervening seas ; for we have herc as it were
a test or standard by wliich TTC iiiay mcasurc the possible effect
due to these causes, and we find that, under conditions perhaps the
most favourable that exist on tlic globe, the percentage of species
derived from this source is extremely small. When my researches
in tlic Archipelago arc coinpleteil, I hope t o be able to determine
with some accuracy this iiuniericd proportion in several cases ; but
in the iiieaii time wc mill consider 20 per cent. as the probablc
iiiaximuiii for birds and niammnls JF hi& in Cclcbes have bccii
derived from Borneo or J a \ a.
Lct us now apply this standnrcl t o tlic case of Great Britain and
the Continent, iu whicli tlic ~iicltliof divicling sea aud the extcnt
of opposing coasts arc iicarly the same, but in mhicli the species
:ire almost ill1 identical,-or t o Irclmd, more tliaii 90 per c m t .
of whose species arc British,-and we slinll at once see that no
theory of transmission across tho present Straits is admissiblc, and
sliall be compelled to resort to the idea of a very recent separation
(long since admitted), t o account for these zoological phenomena.
It is, however, to the occmic islands that we consider the application of this test of the most importance. Let any one try t o
realize the comparative fncilitics for the transmission of organized
beings across the Strait of IEacassar from Borneo t o Celebes, and
from South Europe or Nortli Africa, to the island of Madeira, a t
least four times the distance, and a mere point in the ocean, and
lie would probably consider that in a given period a hundred cases
of tranemissioa would be marc likely to occur in the former case
OEOGRAPIIT OF TWE N A L A P ARCBIPELAUO.
181
than one in the latter. Yet of the comparatively rich insect-Bnna
of 1\1Zadeirn,40 per cent. are continenla1 species ; and of the flowcriiig plants more than GO per cent. The Caiiary Islands ofer
nearly similar results. Nothing but a former connesioii with the
Continent will explain sncli an amount of specific identity (tlic
weight of which will be very much increased if we take into account
the representative species) ; a i d the direction of the Atlas range
towards Teneriffe, and of the Sierra Nevada towards Madeira, are
material indications of siucli a connesion.
The Galapagos are no fiirtlier from South America than Madeira is from Europe, and, being of greater extent, arc far more
liable to receive chance iiiiiiiigrants ; yct they hare hardly a species
identical with any inhabiting the American continent. These
islands therefore niay well have originated in mid-ocean; or if
they ever were connectecl \\it11 the mainland, it was at YO distant
a period tliat the natural extiiiction and rene\\-nl of species has left
not one in conimon. The character of their fauna, however, is inore
what we should expect to arise from the chancc introduction of a
very fcw species at distant i i i t e r d s ; it is very poor ; it contains
but few genera, and those scattered. among unconnected families ;
its genera oftcii contaiu scvernl closely allied species, indicating
a single antitype.
The fauna aiid flora of IIadeira mid of the Canaries, 011 thc other
liand, have nolie of this cliancc character. They are comparatively
rich in genera and species ; iiiost of the priiicipal groups and
families are more or less rcprewitecl ; and, in fact, tliesc ial:mda do
not diifcr materially, as to tlic gencrd character of thcir a n h a 1 and
vegetable productions, fi*oni any isolated mountain i u Europe or
North Africa of about equal extent.
On exactly the same principles, the very large numbcr of species
of plants, insect+ and birds, in Europe and Korth America, either
absolutely identical or represented by very closely allied species,
most assuredly indicates tliat somc means of land coiiimtunieation
ill temperate or sub-arctic latitudes existed at no very distant geological epoch ; and though iriniiy iiaturalists are iiiclinccl t o regard
a11 such views as vague aiid unprofitable speculations, ivc arc
convinced they will soon takc tlwir place among the legitimate
deductions of science.
Geology can detect but a portion of the changes the surface of
the earth has undergone. It can reveal the past history and mutations of what is now dry lalid ; but the ocean tells nothing of her
bygone history. Zoology and Dotany liere collie to tlie aid of
182
MR. A. R. WALJJACE ON TITE ZOOLOGICAL
thcir sister science, and by nieaiis of the liumble wccds and ciespised insects inhabiting its now diataut &ores, can diacover some
of those past changes which the ocean itself refuses to reveal.
Tlicy can indicate, approximately a t least, where and a t what
period former continents must have existed, from what countries
islands must have been separated, aiid a t liom distant an epoch the
rupture took place. By the invaluable indications which Mr.
Darwin has deduced from the structure of coral reefs, by the
surveys of the ocean-bed now in progress, and by a more extensive
and detailed knowledge of the geographical distribution of animals
a i d plants, the natfuralist may sooii hope to obtain some idea of
the continents which haye iiow clisappexrcd beneath the ocean,
and of the general distribution of land and 8ea at former geological
epocha.
Most writers on geographical distribution have coinpletely overlooked its connexion with well-cstablishccl gcological facts, and
haye thereby created difficulties where none exist. The peculiar
and apparently endemic fmnm and florfe of the oceanic islands
(such as the (hlapagos and St. Helena) have been dwelt upou as
something anomalous and inexplicable. It has been imagined that
the more simple conditioii of such islands would be to have their
productions identical with those of the nearest lmid, and that their
aci,ual condition is an incoinprcheiisible mystery. Tlie very rejqysc of this is however the case. We really require no speculati\rc hypothesis, no new theory, to explain these phenomena ; they
are the logical results of well-Iriiown laws of nature. The regular
a i d unceasing cxtiiiction of species, and thcir replacement by allied
forms, is iiow 110 hypothcsis, hut an established fact ; and it necessarily produces such ~~wc"linr
f:iitn~cand f l o m in all but receiitly
f'onued or nealy disrupted isl:tnils, subeject of course t o morc or
riiodificntion according t o thc Facilities for the transmission of'
freuli s~ieciesfrom ac1,jncunt continents. Such phenomena thcrefore
arc far froin uncoiiniioii. nladngascar, nlnuritius, the Moluccas,
N t w Zealand, New C'aledonin, the Pacific Islands, Juan Fernantlez, the West India Islands, aiicl iiiniiy others, all present such
peculiarities in greater or le5s do\ clopriieiit. It is the instances
of identity of species in distmt countries that presents the real
tlilliculty. 1Vh:rt was ~ ~ q q ) o s t<od be the more normal state of
things is really exceptional, and requires some hypothesis for its
csplanation. Tlic plicnoiiiena of distribution in the Malay Archipelago, t o which I liavo lierc called attention, tcach us that, however nilrruw iiiay be the strait neptwating an island from ita cou] ( S J ~
OEOCtRAPIIY OF TIIIE MALAY ARCHTEELAOO.
183
tineiit, it is still an iiiipassa”1,lc barrier against the passage of ally
considerable number aiitl \ wicty of lanil aiiiinals ; and that in all
cases in which such irlmids p o w m a tolerably rich aiid T a r i d
€auna of species mostly itLentical, o r closely allied \z it11 thosc of
the adjacent couiitry, 1% c :ire fi,rc~dto the conclusion that iz gcologically recent clisruptioii has t:tl<en place. Great Britain, Irrland, Sicily, SuiiiiLtra, J ;I\ L: and Uoriieo, thc Aru Islands, Ilie
Canaries and Aladeira, arc e a b c ~to xliicli the reasoiiiiig is f~illy
npplicable.
Iii his iiitroductory Esbay u n the Flora of New Zealand, Dr.
Ilooker lias niost coiij iucaiiigly :tpplied this principle to sliow tlw
former coiincxioii or Ncw % c d a i i ; L aiid other southern islalids u itli
the soutliern citreniitg o f ,I
1iieriv:i; and lwill take this opportunity
of calling the attention of’ zoologists to the very satisfactory iiianncr iii which this vien clezrs aw a+,ymany difficulties iii the distribution of animals. The niost obbious of these is thc occiirreiice
of Marsupials in Ainerica only, beyond the AustriLlinn region.
They cvidently ciitered bj the sune route as the plants of S e n
Zealaid aiid Tasmania \vliicli occur in South tciiiperate h i e r i c n ,
but liming greater p o crs
~ of dispersion, u greater plasticity of
organization, 1iai.e mtc~ndetltlieniselvcs over tlia u-holc coutiiieiit
though with so few iiioclifivntions of form and structure as to point
to IL unity of origin :it a winparatively recent period. It is among
insects, however, that tlic rcsciii Iilances approach in iiuuiber and
degree to those cxliibitcd by plmits. Among Butterflies tlic. beautiful HeZicmidfi arc strictly conlincd t o South America, n it11 the
exception of a single gciiiis (Hmiailryns) found in the Australiaii
region from New Zealaiitl to NCWGuinea. l n Colcoptera mniiy
families and geiicra are vliamvtcristic of the t~ o couiitrics j sucli
are Pseziclo~~aoi~~7iitZa.
:~iuoiigtlic Geodephaga, i h y ~ ~ i 9 n i i aiid
fa
Syndesida aiiu)iig the Luv.ani, iiizoplopnthidct. among the Lamellicorncs, ~ S t i . p o d w i d aaiiiciiig tlie Buprestes, Natalis among tlw
C’leridx+,besides :L great i i u i r i b c ~ of representative genera. T l i i ~
peculiar distributiuii h i 5 111 Llicriu only excited astonisliiiieiit, nlitl
has confouiichl all idea.: oj’ iiuity in the distribution of orpiiic:
beiiigs ; but x c: lion w e tlrnt f lrc,>- :we in cxact accordance 1) it11 the,
plieiioiiiena pr2,ciitctl b j t I i c ~Iloi*a of tlie saiiic regions, a s tic\ cloltrd
in the greatest tlclnil by
rc rclics of Dr. Hooker.
It is soiiien liat siugid~ir,hcn\ e~w, that not oiie ilk
of insect should y t ha\e bccu cliscovcred, whde no less t h n 89
species of fio\iering p l d b ;iiv.~ fmud both in New Zexlmd and
South Bmcrica. The rclaticm uf the aniinnls and of the l ~ l ~ t s
t11cb
184
ZOOLOUICAL QEOCRAPIIY OF THE XALAT ARCIIIPELAGO.
of thcse countries must necessarily dcpend 011 the sanie physical
cliaiiges which the Soiitliern liciiiisphere has nndergone ; and we
are thcrcfore led t o concludc thzt insects are inucli lcss persistent
in tlieir specific foriiis than flowering plants, while mnong Maminalia and land birds (in nliich no genns even is coiiimon t o the
countries in question)-spccies must die and bc replaced much morc
rapidly than in either. And this is exactly in accordance with tho
fact (well established by geology) that at a time when the shells
of the Europeaii seas n erc alinost a11 identical with species now
living, the European Maiiimalia were alniost all different. The
duration of life of species woulcl seem to be in an inverse proportion to their complexity of organization and vital activity.
I n the brief sketch I have n o ~ vgiven of this interesting subject,
such obvious a i d striking fhcts alone have been adduccd as it traveller's note-book can s~ipply. The argument ninst tlierefore Iosc
iiincli of its wciglit from the absenw of detail and accninulated
examples. Thcrc is, however, such n very general accordance in
tlic phenoinena of distribution as separately dccluecd from tlic
various classes or liingdoiiis of the organic world, that wlicnever
one class of aniiiials or plants exhibits in a clearly marked manner
certain relations between two countries, the other classes will certainly sliow siiiiilar ones, though it may be in a greater or a less
drgree. Birds and insccts \\ill teach us thc same truths ; and eTreii
:iiiininls and plan ts,'tliougli existing under sncli clifkrciit conditions,
mid multiplied and dispersed by sitcli a generally distinct process, nil1 never gibe coiiflictiiig testimony, however much they
may difl'er as regards thc ainouiit of rclationaliip between distant
regioiis indicatcd by tllem, and consequently notwitlistmiding tllc
greater or less weight citlicr iiiay liave in the determining of
qnestions of this nature.
Tliis is my apology for oik:riiig t o the Linnean Society the present imperfect outline iii anticipittioii of tlic inore detailed proof?
and illustrations which I Iiopc t o bring forward on a future
occasioii.