S6 THE MAMMALIA. 



epoch which has so conveniently killed off all sorts of animals in 

 Europe. Things have gone on in Australia since Post-Tertiary 

 times much as they are going on now. Man himself has probably 

 only recently become a denizen of this " fifth quarter " of the 

 globe. He appears in the rudest and most primitive state, and 

 was unable to kill off even the diminished kangaroos of the present 

 day. Therefore, it seems safe to say that there is a law governing 

 the duration of species. As a man may die by accident or disease 

 after a longer or shorter life, yet must at last die of old age, so it 

 seems to be with species and even orders of animals. They may 

 be pre7?iaturely destroyed by glacial epochs, or drying up of 

 marshes, or inundations of the sea, but if they are exposed to no 

 possibility of perishing by external accidents, the species dies out of 

 old age. 



The Liberal-Conservative animals, if I may be allowed to 

 borrow a term from politics, seem to have the best chance of com- 

 paratively long duration : those which do not change too quickly 

 or too slowly. The frogs have outlived the enterprising Deino- 

 saurs by long ages, and the elephant has persisted longer than the 

 much bigger and more formidably tusked mammoth, Deitioceras^ 

 (whose reptilian brain could suggest no method of making a mark 

 in the world except by growing six horns on the top of his nose), 

 was doomed to a particularly speedy extinction. 



Having shortly examined the Marsupials of Australia and seen 

 how they died out or diminished, notwithstanding every advan- 

 tage in the struggle for existence, we will next examine the 

 Proboscideans, of whom the only living representatives are the 

 two closely-allied species of modern elephants. No animals 

 apparently could be more fitted to survive in the struggle for 

 existence. They were mostly of gigantic size, with a formidable- 

 ness of tusk and a thickness of skin which made them almost 

 invulnerable. Their huge, compressed molars, growing from 

 persistent pulps, served them throughout the longest life. Their 

 food, consisting of leaves and vegetables and branches of trees, 

 was unlikely to fail them. Yet we have but the meagre survival 

 of two species in the present day. The Glacial period appears 

 hazily to account for the extinction of the Mammoth, though 

 he seems to have lived pretty comfortably through it, and to 



