Note 83 — Chapter VI · THE GENERIC THEORY.

A familiar example of this disappearance of a creature before the aggressive powers of another, which is either hostile to or stronger than itself, is presented by the Black Rat (Mus rattus) of our own country,—which is said to have been extremely abundant formerly, but which is now replaced by the common brown (or "Hanoverian") one of Northern Europe. The British species, however, although it has become extremely scarce, is not yet quite exterminated: it has been recorded (vide 'Zoologist,' 611) in Essex, and in Devonshire ('Zoologist,' 2344); and it still swarms on a small rock off Lundy Island, in the Bristol Channel. It is reported, moreover, to have been lately re-introduced at Liverpool.