results has been led to adopt. For a statement of this criterion see page 8. We not only obtain a more rigid standard, but we are more certain that Bird No. i really sees, is interested in, and attends to what the other is doing. It has had such experience with the apparatus, that it is more likely to be interested in what is done in order to open the box.
3. If the Cowbirds did start a series, as they often did, the English Sparrows after a few tests displaced them.
4. This may be accounted for by the fact that the English Sparrow is far more active and though much smaller, often drove the Cowbirds away and held them at bay even after a bitter struggle.
5. The Junco learned to open the food-box, but not until after the female English Sparrow had taken the lead. There was keen rivalry and fighting between them. There was probable imitation of each by the other of the intelligent sort.
6. The White-throated Sparrow and Field Sparrow learned to open the food-box though not so rapidly as some of the other birds. This slowness may be due to the indirect method of the former, to the small size of the latter, and to the fact that both were tried in a cage near the entrance to all the cages, and hence were disturbed a good deal.
7. A young Song Sparrow for a few tests showed signs of rather rapid learning. There were a few uncertain signs of imitation of the intelligent sort with the White-throated, Field, and Song Sparrows and the Junco.
8. In a long series of tests on a pair of Bluebirds, Whitecrowned Sparrows, and two each of Juncos and Tree, Fox, and Song Sparrows, the best fighters were the ones to open the door early in the series. The male Bluebird early began to lead and finally was the only one to do it. Here again there were some uncertain imitative acts on the part of each Bluebird, but chiefly by the female. A memory series for these Bluebirds showed that they had forgotten little in one month. It also revealed some errors on their part which indicated that such memory of the place to alight upon did not mean that they had at any time analyzed the mechanism of the box. Some learning tests on another male Bluebird, who was alone in the cage, showed that he was very slow in starting.
9. A long series of tests with a pair of Blue Jays gave no results on imitation, but did give good evidence of the male's power to learn. But when the strings were changed he did not adapt himself as readily as the English Sparrow. However, it was still possible for the Jay to use his old method. This of course makes it impossible to generalize from these tests.
10. In experiments on three Cowbirds, two males and one female, two young English Sparrows and a male Balti-
