358 
GEOGEAPHICAL DISTEIBUTION. 
Chap. XL 
recent period continents which are now quite separate, 
have been continuously, or almost continuously, united 
with each other, and with the many existing oceanic 
islands. Several facts in distribution,—such as the 
great difference in the marine faunas on the opposite 
sides of almost every continent,—the close relation of 
the tertiary inhabitants of several lands and even seas to 
their present inhabitants,—a certain degree of relation 
(as we shall hereafter see) between the distribution of 
mammals and the depth of the sea,—these and other 
such facts seem to me opposed to the admission of such 
prodigious geographical revolutions within the recent 
period, as are necessitated on the view advanced by 
Forbes and admitted by his many followers. The 
nature and relative proportions of the inhabitants of 
oceanic islands likewise seem to me opposed to the 
belief of their former continuity with continents. Nor 
does their almost universally volcanic composition favour 
the admission that they are the wrecks of sunken 
continents;—if they had originally existed as moun¬ 
tain-ranges on the land, some at least of the islands 
would have been formed, like other mountain-summits, 
of granite, metamorphic schists, old fossiliferous or other 
such rocks, instead of consisting of mere piles of volcanic 
matter. 
I must now say a few words on what are called acci¬ 
dental means, but which more properly might be called 
occasional means of distribution. I shall here confine 
myself to plants. In botanical works, this or that plant 
is stated to be ill adapted for wide dissemination; but 
for transport across the sea, the greater or less facilities 
may be said to be almost wholly unknown. Until I 
tried, with Mr. Berkeley’s aid, a few experiments, it 
was not even known how far seeds could resist the inju¬ 
rious action of sea-water. To my surprise I found that 
