Vol. XXIV. -1 
1925. J 
Annual Congress 
167 
completed by desert in the one case and snow regions in the 
other, while the four well marked sub-regions of the Australian 
animal kingdom have an island or archipelago origin except in 
so far as North Queensland maintains in the animal world its old 
connection with the Austro-Malayan sub-region. To this sub- 
region is, I believe, confined the genus of Cassowaries of which 
the dozen existing species yield such an excellent example to 
zoogeographers, of differentiation under conditions of isolation. 
Originally at home in the large area of New Guinea, there are 
now, T believe, no less than five species there, and six in five 
neighbouring small islands, as well as one in North Queensland. 
This last must have differentiated since the separation of New 
Guinea from North Queensland by the formation of the lorres 
Straits—even the shallow depth of those straits sufficing to isolate 
a bird of bulky form and quite incapable of flight. 1 hose among 
this company who are historical as well as zoological geographers 
will remember that well into the 18th century, Nova Guinea and 
Terra Australis are shown on maps as connected, and in Captain 
Cook’s map Dieman’s Land is drawn as part of New Holland. 
The discovery that these islands were separated from the main¬ 
land occurred in the opposite order to the actual separation. I 
understand geologists hold that Bass Strait was formed before 
Torres Strait, while a connection across what is now the Timor 
Sea was broken at an earlier date, and earliest of all there came 
separation of what we in these days term the Australian and 
Oriental zoogeographical regions by the breach between the 
islands of Lombok and Bali. The bearing of these separations 
on the bird life of Australia is, as you are, I am sure, aware, 
sketched in a fascinating manner by Mathews and Iredale in 
the introduction to their Manual of the Birds of Australia, where 
they suggest two early sources of endemic forms with two later 
immigrations from the north—the endemic forms, such as the 
Emu and Lyre-Birds, being confined to the southern part of 
Australia. In these forms degeneration set in where there was 
lack of inimical opposition, especially in Tasmania, unreached 
by the spent waves of immigration from the north after the 
formation of Bass Strait. Elsewhere competition arising both 
on the east and west sides of the continent between invaders and 
settlers, many of the weaker forms of the latter disappeared, 
while the stronger continued with accumulative progress arising 
from the struggle for life with the newcomers. Invasion from 
the north thus produced reaction from the south, the result show¬ 
ing itself in the form of differentiated species of prevailing 
northern genera. I can hardly conceive a more attractive study 
than that of zoogeographical distribution of species and sub¬ 
species to which the two great ornithologists I have mentioned 
invite us. 
But I am a busy man and no naturalist, and though I find 
myself here in Queensland in the central chamber of what may 
