The couple multiplied rapidly, until whole families of equal whiteness ascended and descended the staircases of the cage. At last we found ourselves at the head of thirty rats, all so much at home with us that when the weather was cold they burrowed in our pockets without the least ceremony, and lay there, keeping themselves warm. Sometimes leaving open the door of the Ratopolis, we would go up to the second floor of the house, and give a whistle well known to our pupils. Then the tiny crew, who with great difficulty could climb from one step of the stairs to the other, would swarm upward, clutching the rail, pulling themselves along by the balusters, following each other in a file with the regularity of acrobats, up the steep road, down which occasionally one slipped, and run to find us, uttering little cries and manifesting the liveliest joy.
We must now confess to an act of bru-
