Note 32 — DARWIN'S EXAMPLES.

If a prominent breast is admired and selected by fanciers, the sternum might shorten in assuming a more forward and vertical position. If the shortening of the sternum is entirely due to disuse, it seems strange that Darwin has not noticed any similar shortening in the sternum of the duck. But selection has not tended to make the duck elegant, or "pigeon-breasted"; it has enlarged the abdominal sack instead, besides allowing the addition of an extra rib in various cases.