For observation and study, the whole vast world of living creatures is ours, throughout all zones and all lands. It is not ours to flout, to abuse, or to exterminate as we please. While for practical reasons we do not here address ourselves to the invertebrates, nor even to the sea-rovers, we can not keep them out of the background of our thoughts. The living world is so vast and so varied, so beautiful and so ugly, so delightful and so terrible, so interesting and so commonplace, that each step we make through it reveals things different and previously unknown. The Frame of Mind. To the inquirer who enters the field of animal thought with an open mind, and free from the trammels of egotism and fear regarding man's place in nature, this study will prove an endless succession of surprises and delights. In behalf of the utmost tale of results, the inquirer should summon to his aid his rules of evidence, his common sense, his love of fair play, and the inexorable logic of his youthful geometry. And now let us clear away a few weeds from the entrance to our field, and reveal its cornerstones and boundary lines. To a correct understanding of any subject a correct point of view is absolutely essential. In a commonplace and desultory way man has been mildly interested in the intelligence of animals for at least 30,000 years. The Cro- Magnons of that far time possessed real artistic talent, and on the smooth stone walls and ceilings of the caves of France they drew many wonderful pictures of mammoths, European bison, wild cattle, rhinoceroses and other animals of their period. Ever since man took unto himself certain tractable wild animals, and made perpetual thralls of the horse, the dog, the cat, the cattle, sheep, goats and swine, he has noted their intelligent ways. Ever since the first caveman began to hunt wild beasts and slay them with clubs and stones, the two warring forces have been interested in each other, but for about 25,000 years I think that the wild beasts knew about as much of man's intelligence as men knew of theirs. I leave to those who are interested in history the task of revealing the date, or the period, when scholarly men first began to pay serious attention to the animal mind. In 1895 when Mr. George J. Romanes, of London, published his excellent work on "Animal Intelligence," on one of its first pages he blithely brushed aside as of little account all the observations, articles and papers on his subject that had been published previous to that time. Now mark how swiftly history can repeat itself, and also bring retribution.