Walking among the oaks one day in early winter when the trees were nearly leafless, I noticed a squirrel sitting very quietly on a branch; and though he did not get excited, he began to move away before me, stopping at intervals and sitting still to watch me for a few moments. He was a trifle suspicious, and nothing more. In this way he went on for some distance, and by-and-by came to a long horizontal branch thickly clothed with long lichen on its upper sides, and instantly his demeanour changed. He was all excitement, and bounding along the branch he eagerly began to look for something, sniffing and scratching with his paws, and presently he pulled out a nut which had been concealed in a crevice under the lichen, and sitting up, he began cracking and eating it, taking no further notice of me. The sudden change in him, the hurried search for something, and the result, seemed to throw some light on the question of the animal's memory with reference {108} to his habit of hiding food. It is one common to a great number of rodents, and to many of the higher mammals--Canidæ and Felidæ, and to many birds, including most, if not all, the Corvidæ. When the food is hidden away here, there, and everywhere, we know from observation that in innumerable instances it is never found, and probably never looked for again; and of the squirrel we are accustomed to say that he no sooner hides a nut than he forgets all about it. Doubtless he does, and yet something may bring it back to his mind. In this matter I think there is a considerable difference between the higher mammals, cats and dogs, for instance, and the rodents; I think the dog has a better or more highly developed memory. Thus, I have seen a dog looking enviously at another who had got a bone, and after gazing at him with watering mouth for some time, suddenly turn round and go off at a great pace to a distant part of the ground, and there begin digging, and presently pull out a bone of his own, which he had no doubt forgotten all about until he was feelingly reminded of it. I doubt if a squirrel would ever rise to this height; but on coming by chance to a spot with very marked features, where he had once hidden a nut, then I think the sight of the place might bring back the old impression.