On The Origin of Species by Charles Darwin Chapter 13 Page 54

organisms ranging more widely than the higher — some of the species of widely-ranging genera themselves ranging widely — such facts, as alpine, lacustrine, and marsh productions being generally related to those which live on the surrounding low lands and dry lands — the striking relationship between the inhabitants of islands and those of the nearest mainland — the still closer relationship of the distinct inhabitants of the islands of the same archipelago — are inexplicable on the ordinary view of the independent creation of each species, but are explicable if we admit colonisation from the nearest or readiest source, together with the subsequent adaptation of the colonists to their new homes.

5. Summary Of The Last And Present Chapters

In these chapters I