to suppose that species, aboriginally as distinct as carriers, tumblers, pouters, and fantails now are, should yield offspring perfectly fertile, inter se, seems to me rash in the extreme.

From these several reasons, namely, the improbability of man having formerly made seven or eight supposed species of pigeons to breed freely under domestication — these supposed species being quite unknown in a wild state, and their not having become anywhere feral — these species presenting certain very abnormal characters, as compared with all other Columbidae, though so like the rock-pigeon in most other respects — the occasional reappearance of the blue colour and various black marks in all the breeds, both when kept pure and when crossed — and lastly, the mongrel offspring being perfectly fertile — from