358 GEOGRAPHICAL DISTRIBUTION. Chap. XI. 



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 

 out of 87 kinds, 64 germinated after an immersion of 

 28 days, and a few survived an immersion of 137 days. 



