Mr. Wallace on the Geographical Distribution of Birds. 453 
that these two regions are as absolutely distinct as South America 
and Africa/ and it is only because they are separated by straits 
of from 20 to 100 miles wide, instead of the Atlantic, that they 
have become slightly connected by the interchange of a few 
species and genera. 
Thus I account for Gallus reaching Celebes and Sumbawa, for 
Cervus in the Moluccas, Megapodius in North-western Borneo, 
a Woodpecker in Celebes, &c. There is, however, an important 
physical feature which gives us the true key to the separation of 
the two regions: it is, that the islands of the Indian region are 
all connected by a shallow sea, while they are separated from the 
Australian region by an unfathomable ocean. Of this connexion 
to the Philippines I am not certain, except as far as Palawan, 
which is joined to Borneo by a 50-fathom bank. Mindanao is 
also closely connected by islands to Borneo. 
Now look at the map of the Archipelago, and consider that 
Borneo and Java have species in common by hundreds, Borneo 
and Celebes only by units, and we shall be forced to believe that 
the two former have been connected at no very distant epoch, 
while the two latter have been ever separated, or at least during 
a long geological epoch, and probably more widely than at pre¬ 
sent. Here then is the key to the problem :—Sumatra, Java, 
Borneo, and the Philippines are parts of Asia broken up at no 
distant period (an elevation of 50 fathoms would in fact join 
them all again); Celebes, Timor, the Moluccas, New Guinea, 
and Australia are remnants of a vast Pacific continent in part 
marked out by coral islands (see Darwin), but broken and sepa¬ 
rated at a more distant period, as shown by the fewer species 
common to the several islands, and the number of distinct sub¬ 
faunas into which the region is divided. Celebes is in some 
respects peculiar, and distinct from both regions, and I am in¬ 
clined to think it represents a very ancient land which may have 
been connected at distant intervals with both regions, or per¬ 
haps with some other continent forming a direct connexion with 
Africa. It may also at one time have had a connexion with the 
Philippines. All this is indicated by a peculiar genus of Rumi¬ 
nants in Celebes (Anoa); by a genus of Apes found in Celebes, 
the Philippines, and Batchian, more nearly allied to the African 
