So much, then, to give a general idea of the extent to which co-operation is exhibited by Ecitons—a fact which must be taken to depend upon some system of signs. Turning next to still more definite evidence of communication, Mr. Hague, the geologist, writing to Mr. Darwin from South America, says that on the mantel-shelf of his sitting-room there were three vases habitually filled with fresh flowers. A nest of red ants discovered these flowers, and formed a line to them, constantly passing upwards and downwards between the mantel-shelf and the floor, and also between the mantel-shelf and the ceiling. For several days in succession Mr. Hague frequently brushed the ants in great numbers from the wall to the floor, but, as they were not killed, the line again reformed. One day, however, he killed with his finger some of the ants upon the mantel-shelf. “The effect of this was immediate and unexpected. As soon as those ants which were approaching arrived near to where their fellows lay dead and suffering, they turned and fled with all possible haste. In half an hour the wall above the mantel-shelf was cleared of ants. During the space of an hour or two the colony from below continued to ascend until reaching the lower bevelled edge of the shelf, at which point the more timid individuals, although unable to see the vase, somehow became aware of the trouble, and turned without further investigation; while the more daring advanced hesitatingly just to the upper edge of the shelf, when, extending their antennæ and stretching their necks, they seemed to peep cautiously over the edge until they beheld their suffering companions, when they too turned and followed the others, expressing by their behaviour great excitement and terror. An hour or two later the path or trail leading from the lower colony to the vase was entirely free from ants.... A curious and invariable feature of their behaviour was that when an ant, returning in fright, met another approaching, the two would always communicate; but each would pursue its own way, the second ant continuing its journey to the spot where the first ant had turned about, and then following that example. For some days after this there were no ants visible on the wall, either above or below the shelf. Then a few ants from the lower colony began to reappear; but instead of visiting the vase, which had been the scene of the disaster, they avoided it altogether, and, following the lower front edge of the shelf to the tumbler standing near the middle, made their attack upon that with precisely the same result.”