Then the question of cross-breeding came up, and he gave his opinion on the qualities of "droppers." To which she replied, sleepily; and the conversation veered again toward the mystery of heredity, and the hopelessness of escape from its laws as illustrated now by the Sagamore pup, galloping nose in the wind, having scented afar the traces of the forbidden rabbit.
"His ancestors turned 'round and 'round to flatten the long reeds and grasses in their lairs before lying down," observed Siward.

"He does it, too, where there is nothing to flatten out.

Did you ever notice how many times a dog turns around before lying down?
And there goes the carefully schooled Sagamore, chasing rabbits! Why?
Because his wild ancestors chased rabbits.

...

Heredity?
It's a steady, unseen, pulling, dragging force.