With animals, facility in preventing crosses is an important element in the formation of new races--at least, in a country which is already stocked with other races.

In this respect enclosure of the land plays a part.

Wandering savages or the inhabitants of open plains rarely possess more than one breed of the same species.

Pigeons can be mated for life, and this is a great convenience to the fancier, for thus many races may be improved and kept true, though mingled in the same aviary; and this circumstance must have largely favoured the formation of new breeds.

Pigeons, I may add, can be propagated in great numbers and at a very quick rate, and inferior birds may be freely rejected, as when killed they serve for food.