begun. We also know how quickly animals acquire the idea of the time of day. Sparrows know when it is time for the bread to be thrown out for them, and collect around the spot at that hour. Lacépède tells of a toad which used to come out of its hole at the time it was accustomed to be fed. I had a lizard that would leave its nest and climb up my sleeve at dinner-time. Persons of my age, in Liege, used to be acquainted with a vagabond dog that regularly at the same hour made the round of the cafés for the bones or the lumps of sugar which he was sure to receive from his friends there; and would as regularly every evening go to his sleeping-place under a particular gateway. This animal evidently perceived the time of day by certain signs that had been taught him by observation; and M. Dubuc's dog knew when it was Sunday, or hunting-day, by the same means. And if, on some Saturday, the house had been arranged and the household had managed to behave in the manner usual to Sunday, the dog too would have been found all prepared for his anticipated hunting excursion, just as if it had not been one day short of his accustomed seven.
This faculty of attentive observation of dogs may be stretched so far as to deceive an experimenter who is a little prepossessed on the subject.
In his paper before the British Association at Aberdeen, Sir John Lubbock related how Mr. Huggins, having arranged cards bearing the ten ciphers, gave his dog a problem, such as to give the square root of nine, or of sixteen, or the sum of two numbers. He would then touch each card in succession, and the dog would make a sound to inform his master when he came to the right one. The dog was always right. The secret of the experiment was that Mr. Huggins unconsciously informed the dog by his attitude when he came to the card that gave the answer. Sir John Lubbock tried to train his dog not to take a piece of bread till he had counted seven; but when he used a metronome the dog showed that he was lost. I made analogous and systematic experiments with my Mouston. They extended to the number four, and I aimed to make the sign of the number more and more indistinct, on each repetition of the experiment. As soon as it was quite effaced, the dog lost his knowledge of it, and his perplexed and inquiring look was amusing.
Sir John Lubbock mentions that Lichtenberg pretended to have a nightingale that could count three. Every day he gave it three meal-maggots, one at a time, and the bird never came back after it had got the third. This observation is very interesting, but we ought to know whether the nightingale did not perceive by some sign that the meal was over. I have no doubt that, if, in the experiments which I have made on siskins and gold-finches, I had had only three grains of hemp-seed in my mouth, they would not have returned after having taken the third seed, or at least would have been likely not to return; but in fact I had many grains, and I frightened them away when they had
