He had understood perfectly well his master's order that he leave
them alone. And he had been disappointed by it. He himself had
not known clearly what it was he would have liked to do to them.
But he had known he and they ought to have some sort of
relationship. And then at the gesture and the snarled command of
"Go get them!" some closed door in Chum's mind had swung wide,
and, acting on an instinct he himself did not understand, he had
hurled himself into the gay task of rounding up the flock.

So, for a thousand generations on the Scottish hills, had Chum's
ancestors earned their right to live. And so through successive
generations had they imbued their progeny with that
accomplishment until it had become a primal instinct. Even as the
unbroken pointer of the best type knows by instinct the rudiments
of his work in the field so will many a collie take up sheep
herding by ancestral training.

There had been nothing wonderful in Chum's exploit. Hundreds of
untrained collies have done the same thing on their first sight
of sheep. The craving to chase and slay sheep is a mere
perversion of this olden instinct; just as the disorderly
"flushing" and scattering of bird coveys is a perversion of the
pointer or setter instinct. Chum, luckily for himself and for his
master's flock, chanced to run true to form in this matter of
heredity, instead of inheriting his tendency in the form of a
taste for sheep murder.

The first collie, back in prehistoric days, was the first dog
with the wit to know his master's sheep apart from all other
sheep. Perhaps that is the best, if least scientific, theory of