But so it has in nature.
The fantail has not only more tail-feathers than any of the three hundred and forty existing species of pigeons, but more than any of the eight thousand known species of birds.

There is, of course, some limit to the number of feathers of which a tail useful for flight can consist, and in the fantail we have probably reached that limit.

Many birds have the oesophagus or the skin of the neck more or less dilatable, but in no known bird is it so dilatable as in the pouter pigeon.

Here again the possible limit, compatible with a healthy existence, has probably been reached.

In like manner, the differences in the size and form of the beak in the various breeds of the domestic pigeon, is greater than that between the extreme forms of beak in the various genera and sub-families of the whole pigeon tribe.