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placental mammals at the end of that or the beginning of the 
tertiary period marked the zenith of their reign, and they had to 
give way in competition with the ancestors of the mammals which 
people the greater part of the world to-day. New Zealand, if it 
ever had a land connection with Australia, must have been 
separated from it before mammals appeared on the earth ; for 
with the exception of two Bats, identical with the Australian 
species, no mammal is known to occur there, and its whole flora 
and fauna is poor numerically, though highly peculiar. 
The English watercress grows so luxuriantly in New Zealand 
as to completely choke the rivers, causing disastrous floods. The 
native plants have been crowded out by it, and the only efficacious 
way of keeping the nuisance down is to plant willows—its old 
competitors—along the river banks. The roots of these trees 
penetrate the bed of the stream in every direction, and the water- 
cress, unable to obtain the requisite amonnt of nourishment, 
gradually disappears. It was only in 1860 that the rabbit was 
introduced into Australia for the purpose of sport; by 1886 
£361,492 had been directly expended in attempting to destroy the 
progeny ; £23,000 had been spent in clearing one State. In New 
Zealand by 1881 more than 500,000 acres of sheep-run were 
abandoned ; the rabbits had monopolised the herbage, and the 
sheep had starved. During the ten years prior to 1886, the loss 
to Australia owing to the rabbit plague was estimated at 
£3,000,000 sterling. In proportion to the rabbits’ increase, there 
has been a decrease in the native mammals, some species of 
which have gone to the wall altogether. 
Not only does the doctrine of Evolution account for the differ- 
ences in the fauna of the great zoographical regions, but it 
explains the otherwise anomalous distribution of such forms as 
the Tapirs, now found only in South America and the Malay 
Archipelago, and the Camels of Asia and North Africa, whose 
nearest allies are the Llama and Huanaco of South America. 
Before our climate had attained its present genial character, 
Ireland had been separated from Great Britain, and a little later 
Great Britain from the Continent. The geological evidence of 
these separations, conclusive in itself, is amply confirmed by a 
comparison of the fauna of Britain with that of Continental 
countries. Germany possesses 90 species of land mammals, 
Scandinavia 60, Britain has only 40, and Ireland only 22. 
Belgium has 22 species of reptiles and amphibians, Britain has 
only 13, and Ireland only 4. . The Irish stoat is slightly different 
from the stoat of England and the Continent, and the house 
mouse and the long-tailed field mouse of the little island of St. 
Kilda in the Outer Hebrides have become slightly differentiated 
from those of the mainland. The Red Grouse is the only species 
