the knotted string passed through. For the twenty-first trial two other female English Sparrows were in the cage. The one designated as No. 2 was noted as showing most promise. In the following test the latter made a few efforts, then there was one effort by No. 1, after which very suddenly No. 2 opened the door by one well placed effort.
These results, which constitute all that were obtained during this series, are insufficient to serve as proof of imitation. Female English Sparrow No. i was too clearly the victor and in later tests drove away others of her kind as well as the Cowbird.
It will be seen that this series furnishes us with fairly satisfactory results so far as concerns times and efforts required. Toward the close the physical condition of the Sparrows did not warrant further trials. Some weeks later an attempt was made to test a pair of Cowbirds and a Junco with the same form of simple maze which was earlier used with a Vesper Sparrow, a female Cowbird and several English Sparrows. See Am. Jour. Psy., Vol. XVII, p. 253. It is not the intention here to state in detail the results obtained. In order to avoid the difficulty encountered earlier when some of the birds caught their claws in the wire mesh which formed the floor as well as the top and sides of this simple maze, the bottom was cut out. Typical results were obtained with each bird until they formed the habit of stopping at the far corner of the maze or that part which, because of the small size of the experimental cage, was thrown very near the window and on a level with it. The birds, instead of attempting to get through the maze, were attracted toward the source of light and thus stood still or struggled to escape.
This maze is therefore an unsatisfactory test for quantitative results when used under these conditions. In fact the writer had this feeling after having made the first tests.
Series D. A Pair Each of English Sparrows and Cowbirds and a Single Junco
For some years the writer had wanted to make tests similar to those made with the English Sparrow on the Junco. The reason for this is that the Junco remains in this latitude throughout the winter and lives in small groups. When a friend kindly brought me one of these birds, I lost no time in beginning work with it. It seemed none the worse for having bumped against the side of our library building. I found that it was easily kept in captivity since like the Cowbird it seemed to do much better on the various kinds of seed and cracked corn than the English Sparrow. From facts like these one may infer that the English Sparrow's rapid increase in numbers is
