THE AUSTRALIAN NATURALIST. 103 
Investigation of fossils shows very plainly that the animals of 
the earth have passed through three very important phases, in 
which certain types became predominant, reached their climax 
and passed away. The first phase, which comes prominently 
under notice is that of the invertebrates and the fishes. ‘This 
was followed by the age of reptiles and amphibians. It was in 
this age that the reptiles reached their highest development, 
and their greatest size, some forms absolutely dwarfing the 
largest animals alive on the earth to-day. These animals chiefly 
through over-specialisation, which left them quite unsuited to 
withstand any change in their environment, have absolutely 
passed away. The age of mammals has passed through two 
stages. The first is indicated by the magnificent faunas which 
developed in America, Europe and Asia, prominent members of 
which were the Mastodon, Mammoth, Woolly Rhinoceros and the 
Titanothere, and nearer home, the Diprotodont with its con- 
temporary the Thylacoleo, and the Moa. This phase passed, 
probubly as a result of a glacial period, and we have the rich 
and complex faunas inhabiting the world to-day. This may 
be stated to have reached its highest development in point of 
numbers at the beginning of the last century. 
Profound changes have been produced by man among the 
wild animals during the last 150 years. Commercial interests 
have caused the slaughter in enormous numbers. The occupa- 
tion of the land by man has driven the animal inhabitants off. 
In a zoological sense we have entered into the age of man, and 
in the near future all the habitable land will be required by 
man, and the only animals that can remain will be those of 
economic use, so it is clear that we are getting very near the 
end of the age of Wild Mammals. 
The causes of the disappearance of the Australian animals 
is not only the occupation of the land by pastoral and agri- 
cultural interests, but far more important is the introduction of 
animals from other countries. The fox, the cat, the rabbit, 
the rat and mouse, animals reared in a hard school of adversity 
and competition are a million years ahead of our primitive 
rodents and marsupials, and they are rapidly occupying their 
heritage. Already the Bridled Nail-tailed wallaby has gone, the 
Brush-tailed Rock-wallaby is on the verge of extinction. Hastern 
and South Eastern Australia have been practically cleared of 
rat-kangaroos and bandicoots and native-cats. One. thing has 
so far stayed the advance*of the fox on the eastern coasts and 
that is the Poison Tick, but it is very likely that immune ani- 
