198 
REVIEWS. 
So much for the facts; to apply them, M. De Candolle reverts 
to the well known hypothesis which originated with Darwin we 
believe, (which, however, he attributes to Heer and A. Gray), 
that the N. circumpolar regions when warmer than now, were 
also more closely united than they now are, and were peopled by 
a temperate Flora, which was driven southwards in various longi¬ 
tudes by the cold of the Glacial epoch; and continues to observe 
that the chesnut probably originated in the Chinese and Japanese 
regions. It was absent in the hypothetical Europeo-American 
continent, the Atlantis of Heer, which was probably separated from 
America at an earlier date than from the south of Europe. At the 
close of the tertiary epoch, when Europe was continuous with 
Western Asia, the chesnut could extend on that side westward into 
Europe, and advance towards the Alps, whence it proceeded south¬ 
ward to Spain, Corsica, Sardinia and Sicily, islands which were then 
conterminous with Europe, as they certainly were during the 
Miocene epoch. These tracts were, however, already separated 
from Africa before the arrival of the chesnut tree. The Azores, 
Ireland and England being also separated, the species could not 
spread farther west. The most doubtful point is, whether the 
chesnut ever lived in central Asia, between its present habitats 
of China and Asia Minor. In the present state of our knowledge 
we have no data to guide us to any conclusion on this point. 
The discussions on the common and evergreen oaks are as interest¬ 
ing as the above, but hopelessly involved, these species being more 
common, more generally distributed in certain directions; and fur¬ 
ther, being surrounded by satellites of closely allied or doubtful 
species, and nearly connected with fossil tertiary species, in Europe 
and elsewhere, giving rise to whole trains of complicated fragmentary 
considerations (in which the Atlantis continent plays a large part), 
through which we do not see our way clearly to any result; and as 
nothing short of a full, literal translation, too long for the pages of 
this review, would do justice to the discussion, we must refer our 
readers to the essay itself, assuring them that it is well worth a 
careful study. It need hardly be remarked, that all the force of the 
above line of reasoning depends on the establishment of M. De Can¬ 
dolle’s doctrine that birds cannot carry acorns, chesnuts or beech 
nuts across an arm of the sea. The fate of continents and islands 
seems to hang, according to him, on this slender thread. 
The remainder of M. De Candolle’s essay is occupied with his 
opinions and reflections upon the “Systeme de M. Darwin,” which he 
considers to be the most ingenious and complete of those based on 
the theory of the continuous evolution of organic beings. In this, 
however, there is nothing novel, and his grasp of the doctrine is 
feeble compared with that of its two great expounders, A. Gray and 
Huxley, which are well known in this country. Such as it is, it proves 
that the many considerations connected with the geological history, 
development, distribution, variation and classification of organized 
