with inner delight, opening and shutting its lips, its body large and rigid with excitement. Yet it never for one instant paused in its short journeys to and fro.
He noted exactly what it did: it walked, he saw, the same number of paces each time, some six or seven steps, and then it turned sharply and retraced them. By the pattern of the great roses in the carpet he measured it. It kept to the same direction and the same line. It behaved precisely as though it were rubbing against something solid. Undoubtedly, there was something standing there on that strip of carpet, something invisible to the doctor, something that alarmed the dog, yet caused the cat unspeakable pleasure.
"Smokie!" he called again, "Smokie, you black mystery, what is it excites you so?"
Again the cat looked up at him for a brief second, and then continued its sentry-walk, blissfully happy, intensely preoccupied. And, for an instant, as he watched it, the doctor was aware that a faint uneasiness stirred in the depths of his own being, focusing itself for the moment upon this curious behaviour of the uncanny creature before him.
There rose in him quite a new realization of the mystery connected with the whole feline tribe, but especially with that common member of it, the domestic cat—their hidden lives, their strange aloofness, their incalculable subtlety. How utterly remote from anything that human beings understood lay the sources of their elusive activities. As he watched the indescribable bearing of the little creature mincing along the strip of carpet under his eyes, coquetting with the powers of darkness, wel-
