20 JOURNAL OF SCIENCE. 
These conclusions are more precise, but are much the same 
as those at which I arrived in 1872, with the exception that I 
now substitute a South Pacific continent from which Australia 
was isolated, for the lower cretaceous Antarctic continent of my 
former paper. Mr. Wallace’s hypothesis of an isolated West 
Australian continent on which the characteristic Australian flora 
and mammalian fauna were developed is fairly satisfactory, but 
I presume that the Australian birds are not supposed to belong 
to the West Australian fauna. A few, such as the ancestors of 
the honey-suckers and the brush-tongued parrots, may have 
crossed over the sea from New Guinea to Western Australia, but 
the mass of the birds are supposed to be East Australian, to have 
passed into West Australia by the north while the continent was 
being upheaved and its climate still humid, and to have become 
differentiated since the entire drying up of the interior sea so 
dessicated the country as once more to isolate West Australia 
almost as effectually as if it were surrounded by water. But Mr. 
Wallace does not make this sufficiently clear. When, however, 
we come to that part of Mr. Wallace’s hypothesis which deals 
with the connection between Australia and New Zealand we find 
it to be not so satisfactory. In the first place the facts of geology 
are against any connection having taken place between the two 
countries at the time supposed. In the second place the South 
American element in the fauna and flora is not separated from 
the Antarctic element. In the third place the hypothesis fails to 
explain the South American element, except on the supposition 
of large extensions of land during the warm miocene period, for 
which there is no sufficient evidence, and which if it hadoccurred 
would have allowed birds as well as frogs and land-shells to pass. 
And in the fourth place it ignores altogether the special relation 
which exists between New Zealand and some of the islands in 
the Pacific. The hypothesis here proposed, is no doubt incom- 
plete, and will be much improved when the paleontology of New 
Zealand is better known ; but it does, I think, give a fairly satis- 
factory account of the origin of the South American, Australian, 
and Polynesian elements in our fauna and flora. The Antarctic 
and North Temperate elements still remain for consideration, but 
so wide a subject cannot be entered upon at the end of an ad- 
dress, and I must postpone all discussions to some future oc- 
casion. 
ON THE HYBRIDISM OF NEW ZEALAND PLANTS. 
BY BARON FERD. VON MUELLER, K.C.M.G., F.R.S. 
Serine saeeree 
In dealing descriptively in the first instance with the ele- 
ments of a new flora, the workers on material, avowedly often 
incomplete, must encounter great difficulties in assigning specific ° 
limits to the forms brought before them, particularly as the ideas 
as to what constitutes a real species are still so vague, and as even 
