Forel places in a jar some ants of enemy species, the sanguinea and the pratensis. After a few days of warfare, followed by a sullen armistice, he introduces a newly hatched pratensis which is very hungry. She runs to those of her own species begging them to feed her. The pratenses fob her off. Then the poor innocent appeals to the enemies of her species, the sanguineae, and, after the manner of ants, she licks the mouth of two among them. The two sanguineae are so touched by this gesture, which turns their instinct topsy-turvy, that they disgorge their honeyed store and feed the young enemy. Thenceforward all is well. An offensive and defensive alliance is formed between the little pratensis and the sanguineae against the ants of the young one's own species. The alliance becomes irrevocable. Let me adduce another example; the results of a common danger. Forel places in a bag a nest of sanguineae and another of pratenses. He shakes them together, and leaves them in the bag for an hour. Thereafter he opens the bag and places it in direct contact with an artificial nest. At first we witness a general state of confusion, a delirium of fear. The ants cannot recognise one another apart; they show their mandibles, and then sidle away in a panic. But by degrees calm is restored. The sanguineae begin by removing the pupae, taking indifferently those of both species. Some of the pratenses follow their example. From time to time fights take place, but these are merely single combats, and they grow less and less fierce. From the next day onwards, all work together. In four days the pact is sealed; the pratenses disgorge food to the sanguineae. At the end of a week, Forel transports them to the neighbourhood of an abandoned ant-hill. They settle in, helping one another in the house-moving, carrying one another, and so forth. No more than a few isolated individuals of the respective species, irreconcilable nationalists no doubt, keep up their sacred enmity, and end by killing one another. A fortnight later, the mixed community is flourishing; perfect concord prevails. The summit of the ant-hill, which at ordinary times is covered with pratenses for the most part, reddens with the martial sanguineae directly danger threatens the common state. Next month, Forel, carrying the experiment a stage further, went to the old nest for a number of the pratenses and put them down just outside the hill of the mixed community. The newcomers promptly fell upon the sanguineae. But these latter defended themselves without animosity, merely knocking the aggressors head over heels, and then letting them alone. The pratenses could not make it out. As for the other pratenses, those belonging to the mixed community, they avoided their sometime sisters, would not fight with them, but carried the pupae into the nest. The hostility was all on the side of the newcomers. Next day some of them had been admitted as members of the mixed community, and ere long