NOTES ON THE GEOGRAPHICAL DISTRIBUTION OF ANIMALS. 265 
are fierce and dangerous animals, they may have been extermi- 
nated partly for this reason. A very interesting volume could 
be written on the animals which have disappeared from Europe 
within historic times. When the ancient world was overrun by 
huge and destructive animals, it must have been difficult for 
men to make any progress in civilization ; but when the glacial 
epoch had swept all before it, it was much easier for men to 
improve their condition. So far as we know, the ancient 
centres of civilization, such as Central Asia and Egypt, were 
less overrun with wild beasts than others. 
The islands of Corsica and Sardinia, though barely alluded 
to by Wallace, are interesting from the number of peculiar 
species which they already contain, and for the still, larger 
number of local forms, which, if isolated for a sufficient time, 
will ultimately become perfectly distinct species. Their fauna 
appears to have been derived from the mainland of Italy at a 
period when that country was already fully stocked with its 
present fauna, as they possess a large proportion of the Italian 
species. They have apparently been separated from the main- 
land for a much longer period than Britain from France ; for, 
although GTuenee calls Britain “ le pays des varietes,” well- 
marked species have not yet had time to develop themselves. 
Here, however, other considerations step in. The much hotter 
and finer climate of Corsica and Sardinia may have stimulated 
the more rapid differentiation of species. And although we 
are still ignorant of many of the laws which govern the range 
of species, yet it appears from the large proportion of species 
common on the French coast, and not extending to Britain, that 
Britain was separated from France before France had fully 
acquired its present fauna and flora. The same reasoning will 
apply to Ireland, which is much poorer in species than 
Britain. 
Some writers think that the Glacial Period has not wholly 
passed away, and that the earth has not yet recovered its 
normal temperature ; and although it would require a long 
series of observations, extending over many years, if not 
centuries, to arrive at absolute certainty, yet there are some 
historical grounds for believing that the climate of all Europe 
was much more severe only 2,000 years ago than at present.* 
How far the clearing of forests, &c., may have influenced the 
climate we do not yet know, nor whether its gradual improve- 
ment is due to local or general causes. It is quite possible that 
the animals and plants now confined to Eastern, Southern, or 
Central Europe are still extending their range north and west, 
so far as they meet with no barriers to their further migra- 
tions. 
* Compare Mallet’s u Northern Antiquities,” pp. 242, 243. 
NEW SERIES, VOL. I. — NO. III. T 
