Some characteristic points of difference--for instance, that of the width of mouth--could hardly be detected in the young.

But there was one remarkable exception to this rule, for the young of the short-faced tumbler differed from the young of the wild rock-pigeon, and of the other breeds, in almost exactly the same proportions as in the adult stage.

These facts are explained by the above two principles.

Fanciers select their dogs, horses, pigeons, etc.