490 
ISLAND LIFE. 
[part II. 
a group of large islands probably extends across or around the 
south polar area to Victoria Land and thence to Adelie Land. 
The outlying Young Island, 12,000 feet high, is about 750 
miles south of the Macquarie Islands, which may be considered 
a southern outlier of the New Zealand group; and the Mac- 
quarie Islands are about the same distance from the 1,000- 
fathom line, marking the probable southern extension of Tas- 
mania. Other islands may have existed at intermediate points ; 
but, even as it is, these distances are not greater than we know 
are traversed by plants both by flotation and by aerial currents, 
especially in such a stormy atmosphere as that of the Antarctic 
regions. Now, we may further assume, that what we know 
occurred within the Arctic circle also took place in the Ant- 
arctic — that is, that there have been alternations of climate 
during which some portion of what are now ice-clad lands 
became able to support a considerable amount of vegetation. 1 
During such periods there would be a steady migration of plants 
from all southern circumpolar countries to people the com- 
paratively unoccupied continent, and the southern extremity 
of America being considerably the nearest, and also being the 
best stocked with those northern types which have such great 
powers of migration and colonisation, such plants would form 
the bulk of the Antarctic vegetation, and during the continuance 
of the milder southern climate would occupy the whole area. 
When the cold returned and the land again became ice-clad, 
these plants would be crowded towards the outer margins of 
the Antarctic land and its islands, and some of them would find 
their way across the sea to such countries as offered on their 
mountain summits suitable cool stations ; and as this process of 
alternately receiving plants from Chile and Fuegia and trans- 
mitting them in all directions from the central Antarctic land 
may have been repeated several times during the Tertiary 
period, we have no difficulty in understanding the general com- 
1 The recent discovery of a rich flora on rocky peaks rising out of the 
continental ice of Greenland, as well as the abundant vegetation of the 
highest northern latitudes, renders it possible that even now the Antarctic 
continent may not be wholly destitute of vegetation, although its climate 
and physical condition are far less favourable than those of the Arctic lands. 
