CHAPTER Imutual aid among animalsStruggle for existence.-Mutual Aid-a law of Nature and chief factor of progressive evolution.--Invertebrates.-Ants and Bees.- Birds : Hunting and fishing associations.-Sociability.-Mutual protection among small birds,-Cranes; parrots.The conception of struggle for existence as a factor of evolution, introduced into science by Darwin and Wallace, has permitted us to embrace an immensely-wide range of phenomena in one single generalization, which soon became the very basis of our philosophical, biological, and sociological speculations. An immense variety of facts :-adaptations of function and structure of organic beings to their surroundings ; physiological and anatomical evolution ; intellectual progress, and moral development itself, which we formerly used to explain by so many different causes, were embodied by Darwin in one general conception. We understood them as continued endeavours-as a struggle against adverse circumstances-for such a deveTable of Contents PASS; Introduction vii; CHAPTER I; mutual aid among animals; Struggle for existence-Mutual Aid-a law of Nature and chief factor of progressive evolution-Invertebrates-Ants and bees--Birds : Hunting and fishing associations-Sociability-Mutual protection among small birds-Cranes; parrots i; CHAPTER II; mutual aid among animals {continued); Migrations of birds-Breeding associations-Autumn societies- Mammals : small number of unsociable species-Hunting associations of wolves, Hons, etc-Societies of rodents ; of ruminants ; of monkeys-Mutual Aid in the struggle for life-Darwin's arguments to prove the struggle for life within the species-Natural checks to over-multiplication-Supposed extermination of intermediate links- Elimination of competition in Nature 32; CHAPTER III; mutual aid among savages; Supposed war of each against all-Tribal origin of human society -Late appearance of the separa