The Malay archipelago : the land of the orang-utan ... - Wallace Online

372 THE MALAY ARCHIPELAGO. [chap.mainland of New Guinea. Among these are the great winglesscassowary, two siiecies of heavy brusli-tui'kej^s, and two of shortwinged thrushes, which could certainlj^ not haA-e passed overthe 150 miles of open sea to the coast of New Guinea. Thisbarrier is equally effectual in the case of many other birds whichlive only in the depths of the forest, as the kinghunters (Dacelogaudichaudi),the fly-catching wrens (Todopsis), the great crownpigeon (Goura coronata), and the small wood doves (Ptilonopusperlatus, P. aurantiifrons, and P. coronulatus). Xow, to sliowthe real effect of such a barrier, let us take the island of Ceram,which is exactly the same distance from New Guinea, butseparated from it by a deep sea. Out of about seventy landbirdsinhabiting Ceram, only fifteen ai-e found iu New Guinea,and none of these are terrestrial or forest-haunting species.The cassowary is distinct ; the kingfishei's, parrots, pigeons, flycatchers,lionej'suckers, thrushes, and cuckoos, are almost alwaysquite distinct s^Decies. More than tliis, at least twenty genera,which are common to New Guinea and Aru, do not extend intoCeram, indicating with a force which eA'ery naturalist willapjDreciate, that the two latter countries have received theirfaunas in a i-adically diffei'ent manner. Again, a true kangaroois found in Aru, and the same sjDecies occurs in !Mysol, which isequally Papuan in its productions, while either the same, or oneclosely allied to it, inhabits New Guinea ; but no such animal isfound in Ceram, which is only sixty miles from Mysol. Anothersmall marsupial animal (Peramales doreyanus) is common toAru and New Guinea. The insects show exactly the sameresults. The butterflies of Aru are all either New Guineaspecies, or very slightly modified forms ; whereas those of Ceramare more distinct than are the birds of the two countries.It is now generally admitted that we may safely reason onsuch facts as these, which sujDply a link in the defective geologicalrecord. The upward and downward movements whichany country has undergone, and the succession of such movements,can be determined with much accuracy ; but geologyalone can tell us nothing of lands which have entirely disappearedbeneath the ocean. Here physical geography and thedistribution of animals and plants are of the greatest service.By ascertaining the depth of the seas separating one countryfrom another, we can form some judgment of the changeswhich are taking place. If there are other evidences of subsidence,a shallow sea implies a former connexion of the adjacentlands ; but if this evidence is wanting, or if there is reason tosuspect a rising of the land, tlien tlie shallow sea may be theresult of that rising, and may indicate that the two countrieswill be joined at some future time, but not that they havepreviously been so. The nature of the animals and plantsinhabiting these countries will, however, almost always enableus to determine this question. Mr. Darwin has shown us howwe may determine in almost every case whether an island has