This book gathered works to understand slavery from a study of the behavior of the workers of ants. The bearing on the origin of slavery of the obvious and fundamental fact that there is a double ontogeny and phylogeny in social organisms, namely, one of the colony as well as one of the individual, has been appreciated only within the past few years and has completely changed the aspect of the subject. It is not confined to ants and other social insects, but has analogies also in human societies (trusts, grafters, criminal and ecclesiastical organizations) and in human families (when the parents become senile).