of the Aru Islands. 481 



determined the distribution of the existing organic world, there 

 must be no exceptions, no striking contradictions. Now we 

 have seen how totally the productions of New Guinea differ from 

 those of the Western Islands of the Archipelago, say Borneo, as 

 the type of the rest, and as almost exactly equal in area to New 

 Guinea. This difference, it must be well remarked, is not one 

 of species, but of genera, families, and whole orders. Yet it 

 would be difficult to point out two countries more exactly re- 

 sembling each other in climate and physical features. In neither 

 is there any marked dry season, rain falling more or less all the 

 year round ; both are near the equator, both subject to the east 

 and west monsoons, both everywhere covered with lofty forest ; 

 both have a great extent of flat, swampy coast and a moun- 

 tainous interior; both are rich in Palms and Pandanacese. If, 

 on the other hand, we compare Australia with New Guinea, we 

 can scarcely find a stronger contrast than in their physical con- 

 ditions : the one near the equator, the other near and beyond 

 the tropics ; the one enjoying perpetual moisture, the other with 

 alternations of excessive drought ; the one a vast ever-verdant 

 forest, the other dry open woods, downs, or deserts. Yet the 

 faunas of the two, though mostly distinct in species, are stri- 

 kingly similar in character. Every family of birds (except Me- 

 nuridm) found in Australia also inhabits New Guinea, while 

 all those striking deficiencies of the latter exist equally in the 

 former. But a considerable proportion of the characteristic 

 Australian genera are also found in New Guinea, and, when that 

 country is better known, it is to be supposed that the number 

 will be increased. In the Mammalia it is the same. Marsupials 

 are almost the only quadrupeds in the one as in the other. If 

 kangaroos are especially adapted to the dry plains and open 

 woods of Australia, there must be some other reason for their 

 introduction into the dense damp forests of New Guinea, and we 

 can hardly imagine that the great variety of monkeys, of squirrels, 

 of Insectivora, and of Felidse, were created in Borneo because 

 the country was adapted to them, and not one single species 

 given to another country exactly similar, and at no great distance. 

 If there is any reason in the hardness of the woods or the scarcity 

 of wood-boring insects, why woodpeckers should be absent from 

 Australia, there is none w^hy they should not swarm in the forests 

 of New Guinea as well as in those of Borneo and Malacca. We 

 can hardly help concluding, therefore, that some other law has 

 regulated the distribution of existing species than the physical 

 conditions of the countries in which they are found, or we should 

 not see countries the most opposite in character with similar 

 productions, while others almost exactly alike as respects climate 

 and general aspect, yet differ totally in their forms of organic life. 



