32 Geological Extinction and [January, 
of the northern and southern hemispheres due to the glacial 
period. They are so familiar to the general reader that they need 
not detain us long. 
By the end of the Tertiary period the northern regions, includ- 
ing the land around the north pole, viz: Spitzbergen, Novaya- 
Zemlya, Siberia, Greenland, together with Northern Europe and 
Northeastern America, must have abounded in life. Forests of 
trees, deciduous, evergreen and palmaceous, in their general ap- 
pearance resembling those of Louisiana, spread like a mantle 
over the land, bordering the vast Tertiary lakes and sheltering 
herds of herbivorous mammals, such as deer, oxen, mammoths» 
which were attended by packs of dogs, or by solitary secretive 
cats prowling through the forest glades, waging war on the weak 
and defenceless or scattered ruminants. 
This rich assemblage of mammalian life, with countless species 
of insects, and other invertebrate organisms, land, fresh-water 
and marine, was swept away. A large proportion died outright, 
perhaps a larger proportion migrated southward; a very small 
per centage survived. The mammoth and mastodon lived on, 
adapted themselves to the great change of climate, but just as 
the ice had passed away and the climate had ameliorated, and 
when the condition of life seemed more favorable, they suc- 
cumbed, The Arcticgbear, fox, lemming and hare, with the white 
ptarmigan and snowy owl, by adaptation to a snow-clad land sur- 
vived, so to speak, the change, or rather, they are the descendants — ) 
of species so plastic that they became modified, and adapted to añn 
Arctic life. Even man, who appeared in the old world before of 
about the time of the incoming of the ice, not only followed the 
retreat of the glaciers, but adopted a strange sort of existence ina 
mean annual temperature of less than 
32° F. Wherever the Eskimo lived he found the walrus and 
seal, the modified relatives of the sea lions and sea elephants of _ 
other parts of the world. The profusion of Tertiary insect life 
was succeeded by a scanty assemblage of Arctic butterflies, — 
ls 
- Lets | 41 
a -5'V"-. Waslit UIC 
moths, bees and other stragglers from the temperate regions, 
The forests died outright, and where Sequoia, the sweet gum; 
the palm and other luxuriant semi-tropical trees flourished, now _ 
grow the dwarfed birch, willows and low herbs of Alpine and — 
Arctic barrens. It is sufficiently manifest that the circumpolar 
flora and fauna are the dwarfed, or otherwise modified descend- 
fe 
