When we come to consider animals in which the anatomist can recognize a brain and the psychologist an individual mind, the types of gregariousness we meet with are found to have lost the magnificent intensity of the bee. This decline in intensity seems to be due to the greatly increased variety of reaction of which the individual is capable. The gregarious mammalia are most of them relatively intelligent, they are capable of assimilating experience to a certain extent and have a definite capacity for individual existence. In them the social habit shows comparatively little tendency to a gradual intensification, but is a more static condition. Doubtless, there are other conditions {108} which also limit it. For example, the slowness of multiplication and fixity of structure in the mammalia obviously deprive them of the possibility of undergoing a continuous social integration as the insects have. Be this as it may, we find in them the social habit but little or scarcely at all expressed in physical specialization but shown as a deeply ingrained mental character which profoundly influences their habits and their modes of reaction to bodily and external impressions. Among the mammalia other than man and possibly apes and monkeys, gregariousness is found in two broadly distinguishable types according to the function it subserves. It may be either protective as in the sheep, the deer, the ox, and the horse, or aggressive as in the wolf and allied animals. In both forms it will involve certain common types of capacity, while the distinguishing characteristic of each will be a special kind of reaction to certain stimuli. It is important to understand that these peculiarities are possessed by each individual of the larger unit, and will be displayed by him in a characteristic way whether he is in the company of his fellows or not. It is not necessary to repeat here in any detail the characters of the gregarious mammal. They have been dealt with in an earlier essay, but it is desirable to emphasize here certain features of exceptional importance and some which were but little discussed before. The quite fundamental characteristic of the social mammal, as of the bee, is sensitiveness to the voice of his fellows. He must have the capacity to react fatally and without hesitation to an impression coming to him from the herd, and he must react in a totally different way to impressions coming to him from without. In the presence of danger his first motion must be, not to fly or to attack as the case may be, but to notify the herd. This characteristic is beautifully demonstrated in the low {109} growl a dog will give at the approach of a stranger. This is obviously in no way part of the dog’s programme of attack upon his enemy—when his object is intimidation he bursts into barking—but his first duty is to put the pack on its guard. Similarly the start of the sheep is a notification and precedes any motion of flight.