in two or more degrees—­the family first, then the group, and finally the association of groups, habitually scattered, but uniting in case of need, as we saw it with the bisons and other ruminants.  It also takes higher forms, guaranteeing more independence to the individual without depriving it of the benefits of social life.  With most rodents the individual has its own dwelling, which it can retire to when it prefers being left alone; but the dwellings are laid out in villages and cities, so as to guarantee to all inhabitants the benefits and joys of social life.  And finally, in several species, such as rats, marmots, hares, etc., sociable life is maintained notwithstanding the quarrelsome or otherwise egotistic inclinations of the isolated individual.  Thus it is not imposed, as is the case with ants and bees, by the very physiological structure of the individuals; it is cultivated for the benefits of mutual aid, or for the sake of its pleasures.  And this, of course, appears with all possible gradations and with the greatest variety of individual and specific characters—­the very variety of aspects taken by social life being a consequence, and for us a further proof, of its generality.(24)

Sociability—­that is, the need of the animal of associating with its like—­the love of society for society’s sake, combined with the “joy of life,” only now begins to receive due attention from the zoologists.(25) We know at the present time that all animals, beginning with the ants, going on to the birds, and ending with the highest mammals, are fond of plays, wrestling, running after each other, trying to capture each other, teasing each other, and so on.  And while many plays are, so to speak, a school for the proper behaviour of the young in mature life, there are others, which, apart from their utilitarian purposes, are, together with dancing and singing, mere manifestations of an excess of forces—­“the joy of life,” and a desire to communicate in some way or another with other individuals of the same or of other species—­in short, a manifestation of sociability proper, which is a distinctive feature of all the animal world.(26) Whether the feeling be fear, experienced at the appearance of a bird of prey, or “a fit of gladness” which bursts out when the animals are in good health and especially when young, or merely the desire of giving play to an excess of impressions and of vital power—­the necessity of communicating impressions, of playing, of chattering, or of simply feeling the proximity of other kindred living beings pervades Nature, and is, as much as any other physiological function, a distinctive feature of life and impressionability.  This need takes a higher development and attains a more beautiful expression in mammals, especially amidst their young, and still more among the birds; but it pervades all Nature, and has been fully observed by the best naturalists, including Pierre Huber, even amongst the ants, and it is evidently the same instinct which brings together the big columns of butterflies which have been referred to already.